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WATER QUALITY Catchment Management Evidence Review
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Bringing people together to understand how to achieve a better
more sustainable environment
COLLABOR8 is a transnational European project, funded by the Interreg IVB North West
Europe programme, which aims to contribute to the economic prosperity, sustainability and
cultural identity of North West Europe in increasingly competitive global markets. This is
being achieved by forming and supporting new clusters in the cultural, creative, countryside,
recreation, local food and hospitality sectors using uniqueness of place as a binding force and
overcoming barriers to regional and transnational collaboration.
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“Water is the driving force in nature.”
Leonardo Da Vinci
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The Upstream Thinking Project is South West Water's flagship programme of
environmental improvements aimed at improving water quality in river
catchments in order to reduce water treatment costs. Run in collaboration with a
group of regional conservation charities, including the Westcountry Rivers Trust
and the Wildlife Trusts of Devon and Cornwall, it is one of the first programmes
in the UK to look at all the issues which can influence water quality and quantity
across entire catchments.
Published by:
Westcountry Rivers Trust
Rain Charm House, Kyl Cober Parc
Stoke Climsland
Callington
Cornwall PL17 8PH
Tel: 01579 372140
Email: [email protected]
Web: www.wrt.org.uk
© Westcountry Rivers Trust: 2013. All rights reserved. This document may be reproduced with prior
permission of the Westcountry Rivers Trust.
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CONTENTS Introduction 6 Fresh water: a vital ecosystem service 6 Pressures affecting water quality 6 Factors that determine pollution risk 7 The catchment management ‘toolbox’ 10 Assessing the efficacy of interventions 15
Pollutant Summaries 16 Nutrients & algae 16 Suspended solids & turbidity 28 Pesticides 35 Microbes & parasites 45 Colour, taste & odour 52
Assessing improvements 57
Governance & planning 65
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INTRODUCTION Fresh water: a vital ecosystem service Rain falling on the land brings life to the plants and animals living upon it, but it also
collects and runs across the land forming rills, gullies, streams and ultimately rivers. The
transfer of fresh water onto and then across the land is one of the fundamental
processes that sustain life on Earth. All of us depend on the fresh, clean water in our
rivers and streams every day – we drink it, we bathe in it and it sustains other life on
which we depend for food and enjoyment.
Targets for the acceptable levels of pollutants in fresh water are set out in the European
Commission’s Directive on the Quality Required of Surface Water Intended for the
Abstraction of Drinking Water 1975 (75/440/EEC) and, more recently, in the European
Commission’s Water Framework Directive 2000 (2000/60/EC).
While the former EC Directive refers to the quality of raw water intended for human
consumption, the latter sets targets above which it is expected that the ecological
condition of a watercourse may be degraded.
In addition, Article 7 of the Water Framework Directive (2000) also stipulates that, for
‘waters used for the abstraction of drinking water’, waterbodies should be protected to
avoid any deterioration in water quality, such that the level of purification treatment
required in the production of drinking water is reduced.
While for most pollutants there is no inevitable link between the quality of raw and
treated drinking water, the level of contamination in raw water is directly linked to the
diversity, intensity and cost of the treatments required.
Furthermore, there are certain pollutants or physical characteristics that, when they
occur in the raw water, can severely affect the efficiency of the drinking water treatment
process. When these pressures do occur, or when the water treatment process does not
take account of a specific pollutant or group of pollutants, there can be an increased risk
that the treated drinking water may fail to reach the drinking water standards required
at the point of consumption (the tap).
Pressures affecting water quality Aquatic ecosystems can be damaged or degraded by a wide variety of pressures, which
arise either from human activities being undertaken in specific locations (point sources)
or from the cumulative effects of many small, highly dispersed and often individually
insignificant pollution incidents (diffuse sources).
Highly localised, point sources of pollution occur when human activities result in
pollutants being discharged directly into the aquatic environment. Examples include the
release of industrial by‐products, effluent produced through the disposal of sewage, the
overflows from drainage infrastructure or accidental spillage.
Superimposed on the pressures exerted by point sources of pollution are the more
widely dispersed and less easily characterised diffuse pollution sources.
When large amounts of manure, slurry, chemical phosphorus‐containing fertilisers or
agrochemicals are applied to land, and this coincides with significant rainfall, it can lead
to run‐off or leaching from the soil and the subsequent transfer of contaminants into a
watercourse. In addition, cultivation of arable land in particular ways or the over
disturbance of soil by livestock (poaching) can make fine sediment available for
mobilisation and subsequent transfer to drains and watercourses by water running over
the surface.
Other diffuse sources include the run‐off of pollutants from farm infrastructure such as
dung heaps, slurry pits, silage clamps, feed storage areas, uncovered yards and chemical
preparation/storage areas.
Animal access to watercourses can also lead to the direct delivery of bacterial and
organic compounds to the water and to their re‐mobilisation following channel
substrate disturbance. It should be noted that, while these agricultural sources of
pollution can often appear more like point sources, they are, however, considered as
diffuse sources as they relate to widespread, land‐based, rural practices that that can
have significant cumulative effects.
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Pollutants that exert negative impacts on the quality of fresh water, degrade the health
of our aquatic ecosystems and contaminate raw drinking water are numerous and
varied. For this review, these pollutants are categorised under five main headings:
Nutrients. Phosphorus & nitrogen‐containing compounds
Suspended solids. Including both sediment & organic material in suspension
Pesticides. Including other chemical pollutants from domestic sources
Microbiological contaminants. Including faecal coliforms & cryptosporidium
Colour, taste & odour compounds. Including metals & soluble organic compounds
Factors that determine pollution risk There are a number of factors in the landscape that determine the degree to which a
pollutant will become available in a particular location and the likelihood of it being
mobilised and carried along a pathway to a watercourse.
Soil character & condition
The characteristics and condition of the soil in a particular area both play a key role in
the ability of the land to regulate the movement of water and the likelihood that
pollutants will become available for mobilisation into adjacent aquatic environments.
Some soils, such as heavy clay‐ or peat‐based ‘stagnogleys’, are more susceptible to
damage, such as compaction, caused by intensive cultivation or livestock farming. This
increases the risk of erosion or significant surface run‐off occurring from their surface.
Other soil types, such as lighter, free‐draining ‘brown earth’ soils, can have pollutants
leached away by water passing rapidly down through them. In addition, soils with very
high levels of organic matter, such as peat, can release large quantities of organic
compounds when they are drained or their structure has become degraded.
In light of this, it is clear that careful and appropriate management of soils can be a
powerful method for minimising the risk of pollution occurring as a result of their innate
structural vulnerability.
Topography & hydrology
The shape (morphology) of the land interacts with the underlying soil type and geology
to control the movement of water across the landscape. Some of the water falling on
the land as rain will be absorbed into the soil from where it can be taken up by plants or
pass down into the groundwater held in the underlying geology.
When the soil is saturated or damaged or the underlying rock is impermeable, water
stops being absorbed and begins to move laterally across the land via surface or sub‐
surface flow. Once moving through the landscape, water then collects in rills, gullies,
drains and ditches, before entering our streams and rivers to make its way back the sea.
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INHERENT RISK
PRACTICE
The risk that an area of land poses to
the provision of an ecosystem service,
such as the regulation of water quality,
can be conceptualised as the
interaction between the inherent
characteristics of the land and the
activities or practices being undertaken
upon it. Therefore, it is possible to
identify areas where potentially risky
practices are being undertaken and
where this coincides with a high
underlying risk that water quality could
be degraded. These high‐scoring areas
can be considered the priority for the
targeting of catchment management
interventions and also where the
greatest enhancement of ecosystem
service provision may be achieved.
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In certain areas across the landscape, where there are steep converging slopes or where
the land is flat, water will naturally accumulate more than in other areas. In these
‘hydrologically connected’ or ‘wet’ areas there is an increased likelihood, particularly
during periods of heavy rainfall, that water will run rapidly across the surface and
mobilise any pollutants that are available on the land surface.
Given the fact that certain areas, due to their morphology, have an elevated level of
hydrological connectivity and an increased probability that water will flow laterally
across their surface, it is vital that we identify them and design tailored management
interventions to mitigate any risk that they may generate pollution.
Land‐use & land‐cover
The use to which a parcel of land is put can have a significant effect on its ability to
regulate the movement of water across it and the likelihood that it will generate
pollution in the aquatic environments nearby.
Natural habitats have rougher surfaces with more complex vegetation. They therefore
have a relatively low risk of becoming a pollution source as they are more likely to slow
the movement of water across the landscape, increase infiltration into the soil and
increase the uptake of water by plants.
In contrast to natural habitats, land in agricultural production experiences greater
levels of disturbance, whether through cultivation or the actions of livestock, and there
is therefore greater risk that it will become damaged and become susceptible to
erosion, pollutant wash‐off or pollutant leaching.
While it is certainly not always the case, the risk of pollution occurring is generally higher
where land is in arable crop production or under temporary grassland. This is simply
because the presence of bare earth for longer periods and the high intensity of
cultivation undertaken on this land increases the likelihood that the soil condition may
be degraded and pollutant mobilisation may occur.
Land under permanent grassland (pasture) inherently represents a lower pollution risk
due to its undisturbed soil and more mature vegetation. However, even this landuse can
generate significant levels of pollution when its soil surface becomes damaged by high
livestock density or when large levels of nutrients or pesticides are applied to improve it.
When assessing the risk that diffuse pollution may occur, there are also areas of urban
and industrial landuse that should not be overlooked. Significant levels of pollutants
(such as sediment, oil, metals, pesticides and a variety of other chemicals) can be
mobilised from the often impermeable surfaces and drainage systems connected to
watercourses in urban environments.
In light of these differences in the ability of different land‐uses and land‐covers to
generate pollution, it is clear that either changing land‐use or ensuring that best
management practices are undertaken on each particular land‐use represent the most
important methods for the mitigation of land‐use driven pollution risk.
Hydrological assessment of a river valley
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Practice & land management
While soil characteristics, morphology, hydrology and land‐cover all contribute the
innate potential for land to generate water pollution, it is ultimately the management of
land and the practices that are undertaken upon it that will determine the likelihood and
scale of any pollution that occurs.
The intensity and timing of our activities can affect the ability of land to retain pollutants
and so increase the likelihood of pollution arising from it. The risk of pollution occurring
can be increased when land is over‐stocked with livestock in vulnerable locations or at
times of elevated risk due to the increased chance of heavy rainfall. The risk can also be
increased when land is drained, compacted with machinery or when it becomes
damaged by repeated cycles of intensive cultivation and crop production.
Furthermore, the exogenous application of additional materials (manure and slurry) and
chemicals (pesticides and fertiliser) to the land can increase the availability of pollutants
in certain areas at times when there is increased likelihood that they will be mobilised
and transported into aquatic ecosystems.
Finally, it is also important to consider the impacts that other human practices, such as
recreational and domestic activities, can have on the condition of land, the availability of
pollutants in certain areas at certain times and the risk they pose to the water quality.
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Mapping key areas for the provision of fresh water as an ecosystem service There are areas of land where, due to the physical characteristics of the location or a sudden change in the weather, any
land management practice, irrespective of whether it is inherently risky and despite best practice being observed, can
still result in the generation of pollution. On this high priority land, there is the greatest likelihood of water quality being
degraded and for the ecosystem services dependent on it to be compromised. In addition, these are also the areas where
the greatest environmental benefits may be realised for the minimum investment.
Through combining data on soil characteristics, landuse, land topography and hydrological connectivity we can create a
map of these innately risky and therefore the most important areas of land in a catchment (the example below shows
and analysis of this type performed on the Tamar catchment).
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CASE STUDY
Paul Anderson
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A Catchment Management Toolbox If we can determine which pressures are exerting negative impacts on the water quality
in our aquatic ecosystems and identify their sources in a catchment, then we can
develop a programme of tailored and targeted interventions to remove these sources
and disconnect their pollution pathways.
For many point sources of pollution, the scale of their contribution to the pollution load
in a watercourse can be characterised through monitoring and modelling approaches
and then regulatory and technological measures can be implemented to mitigate their
impacts.
In contrast to point sources of pollution, the various sources of diffuse pollution in
catchments are far harder to identify and, individually, their impacts are often too slight,
intermittent or transient to quantify with great accuracy and certainty. Despite these
challenges, however, there is now a wealth of evidence and data which do allow these
diffuse sources of pollution to be identified and for programmes of interventions and
measures to be developed to mitigate their impacts.
Over the last 10‐15 years a comprehensive suite of land management advice and on‐
farm measures has been developed to minimise loss of pollutants from farms while
maximising efficiency to increase yields and save costs. Some of the most common of
these so‐called Best Farming Practices (BFPs) that are now recommended to farmers,
and which are now being delivered on farms across the UK, are illustrated on the
following page.
There are now many organisations that have skilled, knowledgeable and highly qualified
farm advisors who are able to give advice on farming practices, including; Catchment
Sensitive Farming, Rivers Trusts, Wildlife Trusts, Soils‐for‐Profit, Natural England, the
Environment Agency and the Farming & Wildlife Advisory Group to name just a few. In
addition, land managers also obtain a considerable amount of advice from their own
agronomists and farming advisors.
What is clear is that, irrespective of who is delivering an integrated farm advice and
investment package, it should cover a broad spectrum of land management practices
and indicate where the adoption of good or best practice may minimise the risk that an
activity will have a negative impact on the environment and where it may enhance the
provision of an ecosystem service such as water quality provision.
During the development of the on‐farm intervention toolbox there were a number of
key design considerations taken into account, which allow a farm advisor to correctly
tailor and target their application:‐
Mechanism of action. It is important to understand the mechanism via which the
intervention will reduce pollution. Often this will require the presentation of evidence
that it is the farming practice that is causing pollution before intervention is
undertaken.
Applicability. Each measure must have the farming systems, regions, soils and crops
to which it can be applied clearly defined. Farm advisors must recommend
interventions that are suitable for the situation found on a particular farm.
Feasibility. The ease with which the measure can be implemented and any potential
physical or social barriers to its uptake or effectiveness must be identified. Careful
consideration must be given to measures that may impact other farming practices.
Costs & benefits. The cost of implementing, operating and maintaining the measure
must be clearly understood. The potential practical and financial benefits to the
farmer of implementing the measure must also be estimated as it is vital for
encouraging uptake of the measures. In some circumstances, where the cost is high
or the measure will result in a loss of income, the farmer or farm advisor may need to
find additional funding from incentive or capital grant schemes to enable delivery.
Strategically targeted. The measures need to be delivered into situations where
they are most likely to have the desired water quality outcome. By ensuring that the
right intervention is targeted onto the most suitable and appropriate parcel of land,
the likelihood that the most cost‐effective use of the investment has been made
increases – i.e. the greatest possible ecosystem service improvement has been
delivered for the resources deployed.
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In this review, for each of the five main pollutant categories, we give an overview of the
interventions that can been delivered to mitigate the impacts of pollution on; (1) the
ecological health of our river catchments, (2) the risks and costs incurred at drinking
water treatment works through having to treat low quality raw water, and (3) on the
generation of pollution‐derived problems in the estuaries and coastal regions in the
lower reaches of river catchments.
Furthermore, we also describe the catchment management interventions considered to
be the most effective in reducing diffuse pollution and mitigating the impacts described.
We will also attempt to evaluate and summarise the numerous studies (completed or
currently underway) which allow us to estimate the scale of benefit that these
catchment management interventions can deliver at a variety of scales.
In assessing and collating this evidence, we hope that we will be able to demonstrate
with some certainty that significant improvements in water quality can be achieved
through the targeted and integrated implementation of catchment management
interventions.
The catchment management intervention toolbox can be delivered through a variety of
approaches, which are described in more detail in the sections below.
Farm visits and advice
An integrated land management advice package will cover many aspects of a farmers
practice and will indicate where the adoption of good or best practice may minimise the
risk that an activity will have a negative impact on the environment and where it may
enhance the provision of a particular ecosystem service.
In addition to broad advice on good or best practice, an integrated farm advice package
should produce a targeted and tailored programme of measures that could be
undertaken and should include specific advice on pesticide, nutrient and soil
management on the farm to mitigate any potential environmental impacts.
Illustration showing some practices that can pose a threat to water quality (left side) and a wide array of Best Farming Practices (BFPs) (right side) which can minimize loss of pollutants to watercourses as a result of agricultural activity.
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Capital grants for on‐farm infrastructure
Where an advisor believes it to be appropriate, they will recommend in the
management plan that improvements or additions be made to the infrastructure on a
farm. Although some statutory designations, such as Nitrate Vulnerable Zones, do
require certain standards in on‐farm infrastructure, under most schemes the uptake of
these measures is entirely voluntary and the advisor will indicate funding mechanisms
through which a grant may be obtained to contribute to the total cost of the work.
Incentivisation to change farming practice
At present, farmers, who represent less than 1% of our society, currently manage nearly
80% of our countryside and are largely responsible for the health of the ecosystems it
supports. However, despite their key role in managing our natural ecosystems, farmers
are currently only paid for the provision of one ecosystem service; food production.
To redress this apparent imbalance, there are now a number of funding programmes
through which land managers and farmers can receive payments for adopting more
environmentally beneficial and ecosystem services‐enhancing practices on all or part of
their land. Schemes of this type, in which the beneficiaries of ecosystem services
provide payment to the stewards of those services, are often referred to as Payments
for Ecosystem Services (described in more detail in Assessing Improvements on p64).
The basic idea behind Payments for Ecosystem Services is that those who are
responsible for the provision of ecosystem services should be rewarded for doing so,
representing a mechanism to bring historically undervalued services into the economy.
Farming community engagement & education
Educational and training activities, such as farmer meetings and workshops, which raise
awareness of different initiatives and promote best practice among local farming
communities, are a key component of any catchment management programme. They
also serve to establish relationships and build trust between advisors and farmers on the
ground in a catchment.
LEAF (Linking Environment And Farming) LEAF is the leading organisation promoting sustainable food and farming. They help farmers
produce good food, with care and to high environmental standards, identified in‐store by the
LEAF Marque logo. LEAF attempts to build public understanding of food and farming in a
number of ways, including; Open Farm Sunday, Let Nature Feed Your Senses and year round
farm visits to our national network of Demonstration Farms.
LEAF is also an industry partner in the Campaign for the Farmed Environment (CFE), which is an
opportunity for their members to demonstrate their commitment to protecting and enhancing
the farmed environment. As part of the Campaign, farmers are asked to ensure that a third of
their ELS points come from a list of key target options. These include options which result in
cleaner water and healthier soil, protect farmland birds and encourage wildlife and biodiversity.
LEAF also provide a wide array of educational and best practice guidance resources
on their website, including their Water Management Tool, which offers farmers a
complete health check for water use on their farms, and the Simply Sustainable
Water Guidance booklet and film. The Simply Sustainable Water booklet has been
produced to help farmers develop an effective on‐farm management strategy for
efficient water use and to improve their farm’s contribution to protecting water in
the environment. It allows farmers to get the best from this valuable resource, to
improve awareness of the importance of water and track changes in water use and
quality over time.
Based on Six Simple Steps to help improve the performance, health and long term
sustainability of their land, farmers are encouraged to set a baseline by assessing
their water use and their water sources. The six key measures are: (1) water saving
measures, (2) protecting water sources, (3) soil management, (4) managing
drainage, (5) tracking water use, and (6) water availability and sunshine hours.
CASE STUDY
Devon Wildlife Trust
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Delivery methods for catchment management At present there are a number of different programmes and initiatives via which
catchment management interventions are funded to deliver catchment‐scale
improvements in water quality through the delivery of land management advice and on‐
farm measures.
Perhaps the most significant of these are; the Natural England‐coordinated Catchment
Sensitive Farming initiative, some elements of the Natural England Environmental
Stewardship Scheme and a number of newly established water company‐funded
schemes, such as the South West Water Upstream Thinking Initiative and the United
Utilities Sustainable Catchment Management Programme (SCaMP).
In addition to these programmes, the Environment Agency, Natural England, the
Forestry Commission and a number of non‐governmental organisations also make
considerable investment of their resources in the delivery of advice and practical
support for people managing natural resources in the catchment.
Each of these catchment management programmes have different funding mechanisms
and use different methods to target and deliver funding. For example, Catchment
Sensitive Farming offers small‐medium grants (up to £10,000 per farm) for capital
investments in farm infrastructure in its priority catchments alongside a programme of
advice and training. In contrast, Environmental Stewardship Schemes offer revenue
payments in return for the delivery of a suite of on‐farm measures in their target areas.
Catchment Sensitive Farming Funded by DEFRA and the Rural Development Programme for
England, Catchment Sensitive Farming (CSF) is a joint initiative
between the Environment Agency and Natural England that has
been established in a number of priority catchments across England.
CASE STUDY
Overall, CSF has two principle aims: (1) to save farms money by introducing careful nutrient and pesticide planning,
reduce soil loss and help farmers meet their statutory obligations such as Nitrate Vulnerable Zones, and (2) to deliver
environmental benefits such as reducing water pollution, cleaner drinking water, safer bathing water, healthier fisheries,
thriving wildlife and lower flood risk for the whole community.
To achieve these goals CSF delivers practical solutions and targeted support which should enable farmers and land
managers to take voluntary action to reduce diffuse water pollution from agriculture to protect water bodies and the
environment.
Catchment Sensitive Farming Officers work with independent specialists from the farming community to deliver free
advice tailored to the area and farming sector. This advice includes workshops, farm events and individual farm
appraisals. CSF also offer capital grants, at up to 60% of the total funding, to deliver improvements in farm
infrastructure.
As part of the Catchment Sensitive
Farming programme, Natural England
have also undertaken an evaluation
study to demonstrate the benefits
that the delivery of advice and
measures have realised.
In addition to a summary report
(http://tinyurl.com/mzyrpc7), Natural
England have also produced a number
of case studies and technical reports
covering specific areas; such as,
advice and education delivery, water
quality monitoring and environmental
modelling. These can be accessed at
http://tinyurl.com/pk5rulg.
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Like Catchment Sensitive Farming, the South West Water Upstream Thinking initiative
also offers capital grants for on‐farm infrastructure improvements, but it also places
conditions on the management of the new infrastructure and on other activities
undertaken on the farm following the investment via a deed of covenant.
In addition, the Westcountry Rivers Trust, along with DEFRA and the University of East
Anglia, have recently investigated the potential of an innovative ‘reverse auction’
approach to target the allocation of funding in a catchment (see below). This work,
undertaken on the River Fowey as part of the Upstream Thinking Project and as part of
a DEFRA Payments for Ecosystem Services (PES) Pilot Project has demonstrated the
cost‐effectiveness of this method for the distribution of catchment management
funding.
Upstream Thinking South West Water (SWW) in collaboration with a group of regional
conservation charities, including the Westcountry Rivers Trust, the
county Wildlife Trusts for Devon and Cornwall and The Farming
and Wildlife Advisory Group, have established one of the largest
and most innovative conservation projects in the UK: the ‘Upstream
Thinking Initiative’.
This project will deliver over £9 million worth of strategic land
restoration in the Westcountry between 2010 and 2015.
CASE STUDY
The ‘provider is paid’ funding mechanism used in the Upstream Thinking scheme is, perhaps, the most innovative aspect
of the project. SWW have recognized that it is cheaper to help farmers deliver cleaner raw water (water in rivers and
streams) than it is to pay for the expensive filtration equipment required to treat polluted water after it is abstracted
from the river for drinking. SWW believe that water consumers will be better served and in a more cost‐effective
manner if they spend money raised from water bills on catchment restoration in the short term rather than on water
filtration in the long term. The entire 5 year initiative will cost each water consumer in the South West around 65p.
Fowey River Improvement Auction
In the first scheme of this kind in the UK, an auction was successfully
used to distribute funds from a water company to farmers, investing
in capital items to improve water quality. The work was supported by
the Natural Environment Research Council Business Internship
scheme, managed by the Environmental Sustainability Knowledge
Transfer Network.
The scheme offered SWW the opportunity to work directly with
researchers from the University of East Anglia to devise an
innovative mechanism for paying for the delivery of ecosystem
services via their Upstream Thinking scheme.
Upstream Thinking uses an advisor‐led approach in other areas.
Advisors from the Westcountry Rivers Trust visit farms to suggest
work and pay grants at a fixed rate. The disadvantages of this
approach are that it’s labour intensive, not practical to visit all farms
and the potential for all the funds to be used on a small number of
farms. The main advantage is that advisors can suggest investments
most likely to improve water quality.
The University of East Anglia devised an auction approach, working with Westcountry Rivers Trust to: (1) increase
coverage by encouraging all eligible farmers to participate, and (2) achieve maximum water quality benefits at the same
time as achieving efficiency for SWW’s investment.
150 farmers in the Fowey catchment, were contacted in Summer 2012 with a list of capital investments eligible for
funding, plus additional farm management practices which could be added to increase bid competitiveness.
Farmers were asked to enter sealed bids up to a maximum of £50,000 per farm.
42 bids were received, requesting a total of £776,000 and 18 bids met the value for money threshold, with grant rates
paid in the scheme from 38% to the full 100%.
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Assessing the efficacy of interventions The principal, over‐arching aim of catchment management is to improve raw water
quality in lakes, rivers and coastal waters. If effective, this approach could make a
significant contribution to their attainment of good ecological status, in accordance
with the EU Water Framework Directive.
In addition, it could also reverse the escalating risks and costs associated with the
treatment of drinking water from our groundwater and surface water sources and it
could reduce the impacts of pollution on our most sensitive and highly productive
estuaries and coastal environments.
Given the potentially significant role of this approach in the improvement of water
quality, it is vital for that we collect sufficient evidence to provide an objective and
scientifically robust assessment of the effectiveness of the interventions used.
Ultimately, we must be able to justify that the money spent and the interventions
delivered across the landscape have delivered both significant improvements in water
quality and a number of secondary financial, ecological and social benefits.
In this review we have attempted to collect a comprehensive and robust set of data and
evidence, which, taken together, demonstrates qualitatively and quantitatively that the
delivery of integrated catchment management interventions can deliver genuine
improvements in water quality.
In sections 2 to 6 we have, for each of the main groups of pollutants, identified key
sources of pollutant loads and examined the impacts these pollutants have on the
aquatic environment, including how they translate into a cost or risk to society.
We have also identified key mitigation measures for reducing pollutant loads and
evaluated the data and evidence for the efficacy of these measures. This process has
also allowed us to identify the interventions for which the evidence of efficacy does
not exist or where it does not exist at an appropriate scale.
Section 7 addresses issues of scale and reviews a selection of modelling tools that
can be used to predict the impact of interventions and measures at a larger sub‐
catchment or whole‐catchment scale. This section also explores the potential for
secondary environmental, economic and societal benefits to result from the delivery
of catchment management interventions.
Section 8 reviews the governance structures currently being used to implement a
catchment management‐based approach in the UK and explores some of the
approaches now being adopted to create catchment management plans.
Determine water quality impacts
Identify & qualify pressures
Locate sources & pathways
Develop programme of measures
Fund & deliver measures
Measure improvements
Record secondary benefits
A summary of the cyclical and adaptive
catchment management process: from
the characterisation of impacts to the
identification of pressures and on to
the delivery of measures and the
evaluation of improvements achieved.
Assessing fish populations using electrofishing
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NUTRIENTS & ALGAE
NUTRIENTS & ALG
AE
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Nitrogen‐ and phosphorus‐containing compounds (often termed nutrients) are natural
and vital components of healthy aquatic ecosystems. They play a critical role in
supporting the growth of aquatic plants, which, in turn, produce oxygen and provide
habitats that support the growth and reproduction of other aquatic organisms.
Nitrogen‐ and phosphorus‐containing nutrients also support the growth of algae,
another natural component of many aquatic ecosystems. Algae occur in the benthic and
planktonic phases of freshwater habitats and form a key component of the food chain
for many species of fish, shellfish and invertebrate assemblages.
Unfortunately, when nutrients are released into the environment, deliberately or
accidentally, as a result of human activities, it can result in a perturbation of the finely
balanced equilibrium of nutrients cycling through the ecosystem.
When nutrients accumulate in aquatic ecosystems they drive the uncontrolled and
unbalanced growth of aquatic plants and algae in a process called eutrophication and
these so‐called plant or algal ‘blooms’ can then cause severe problems for other aquatic
organisms, the ecological health of a waterbody and for the humans who also depend
on the water for drinking water, recreational use or for the production of food such as
fish and shellfish.
Sources of nutrients There are three principal sources of nitrogen‐ and phosphorus‐containing compounds in
a river catchment: point anthropogenic sources, point agricultural sources and diffuse
agricultural sources.
Point anthropogenic sources. A considerable fraction of the phosphorus in river water may be derived from inputs of sewage effluent (which may or may not have
been treated), from drainage systems in urban areas, septic tanks and from roadside
drains. The principal sources of phosphates and nitrates in sewage are human faeces,
urine, food waste, detergents and industrial effluent that have been discharged to
the sewers. Typical sewage treatment processes generally remove 15‐40% of the
phosphorus compounds present in raw sewage and there are many small sewage
treatment facilities and septic tanks in rural areas which could also be making
significant contributions to the phosphorus load in rivers and reservoirs.
Point agricultural sources. These include farm infrastructure designed to store and manage animal waste and other materials such as animal food. Key infrastructure
includes dung heaps, slurry pits, silage clamps and uncovered yards. Animal access
points to watercourses can also lead to the direct delivery of phosphorus compounds
to the water and to their mobilisation following channel substrate disturbance.
Diffuse agricultural sources. When large amounts of manure, slurry or chemical
phosphorus‐containing fertiliser are applied to land, and this coincides with
significant rainfall, it can lead to run‐off and the transfer of phosphorus into
watercourses. This is a particular problem where heavy soils are farmed intensively,
which can result in their compaction and an increased risk of surface run‐off.
There are a number of methods that can be used to estimate the level of nutrient
enrichment in a watercourse and to determine where this contamination has been
derived from. For example, it is widely accepted that a detailed evaluation of the
benthic algae (diatom) communities in a river can provide a robust assessment of its
ecological condition, because these diatom communities are particularly sensitive to
changes in the pH and nutrient levels in the water.
In addition to biological assessments, water quality monitoring can also be used to
characterise the levels of nutrient enrichment in rivers and identify which sections of a
catchment are contributing most to the nutrient load at any particular location.
However, water quality sampling can be costly and time consuming, when undertaken
at fine temporal or spatial scales, and much of the work to identify sources of nutrient
pollution in river catchments has therefore focused on the use of models such as the
Extended Nutrient Export Coefficient Plus (University of East Anglia), the Phosphorus
and Sediment Yield CHaracterisation In Catchments (PSYCHIC) model (ADAS Water
Quality) and the new Source Apportionment GIS (SAGIS) tool (Atkins UK).
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Robert Marshall
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There are numerous potential sources
of nutrients in river catchments;
including sewage discharges (top),
agricultural point sources such as slurry
stores (middle) and diffuse sources such
as fertiliser applied to agricultural land
(bottom).
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CASE STUDY Source Apportionment-GIS (SAGIS) modelling framework The Source Apportionment‐GIS (SAGIS) modelling framework was developed through UWKIR research project WW02:
Chemical Source Apportionment under the WFD (UKWIR, 2012) with support from the Environment Agency. The
primary objective of this research was to develop a common modelling framework as the basis for deriving robust
estimates of pollution source contributions that would be used to support both water company business plans and the
EA River Basin Planning process.
The SAGIS tool quantifies the loads of pollutants to surface waters in the UK from 12 point and diffuse sources including
wastewater treatment works discharges, intermittent discharges from sewerage and runoff, agriculture, soil erosion,
mine water drainage, septic tanks and industrial inputs (UKWIR project WW02). Loads are converted to concentrations
using the SIMulation of CATchments (SIMCAT) water quality model, which is incorporated within SAGIS, so that the
contribution to in‐stream concentrations from individual sources can be quantified.
Diffuse sources of nutrient pollution are incorporated into SAGIS from the Phosphorus and Sediment Yield
CHaracterisation In Catchments (PSYCHIC) model (developed by a consortium of academic and government
organisations led by ADAS Water Quality).
PSYCHIC is a process‐based model of phosphorus and suspended sediment mobilisation in land runoff and subsequent
delivery to watercourses. Modelled transfer pathways include release of desorbable soil phosphorus, detachment of
suspended solids and associated particulate phosphorus, incidental losses from manure and fertiliser applications, losses
from hard standings, the transport of all the above to watercourses in under‐drainage (where present) and via surface
pathways, and losses of dissolved phosphorus from point sources.
The maps below show the baseline export of total phosphorus from manure‐based sources across the Tamar catchment
predicted by the PYCHIC model (inset) and the modelled concentrations of Soluble Reactive Phosphate in sub‐
catchments of the Tamar and their sources according to the SAGIS modelling tool (main).
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Impacts of nutrients On the health of aquatic ecosystems
The principal effect of accelerated plant growth and algal blooms is the reduction
(hypoxia) or elimination (anoxia) of oxygen in the water as oxygen‐consuming bacteria
decompose the plants and algae when they die back. This reduction in the oxygenation
of a waterbody can have a severe effect on the normal functioning of the ecosystem,
causing a variety of problems such as a lack of oxygen needed for fish, shellfish and
invertebrates to survive.
Under the Water Framework Directive (WFD) classification scheme the ecological
impacts of nutrients on freshwater systems are recorded through the changes that they
exert on the plant and algal communities that are found in them. Changes in the
composition of these communities are interpreted as an indication that nutrient
enrichment is perturbing the ecological health of the ecosystem in that waterbody.
The impact of nutrients on the health of estuaries and coastal areas is still relatively
poorly understood but, as with freshwaters, excessive nutrient loads can cause their
eutrophication. The susceptibility of estuaries to nutrient enrichment depends on
factors such as the physical characteristics, the hydro‐dynamic regime and the biological
processes that are unique to each individual estuary. Generally speaking, estuaries and
coastal areas are thought to be less susceptible to eutrophication due to their tidal
nature, which results in high turbidity (less light penetration) and frequent flushing.
Estuaries with good light regimes are often more sensitive to nutrient enrichment.
Primary producers in estuaries may be opportunistic green algae, epiphytes or
phytoplankton and excessive growth of any or all of these can impact on water turbidity
and light availability, causing changes in the depth distributions of plant communities in
the water column. Such changes can have implications for the structure and functioning
of estuarine and coastal food webs, with potential consequences for fish and shellfish
fisheries and for bathing water quality on neighbouring beaches.
In addition to the assessment of these biological indicators, the levels of Soluble
Reactive Phosphorus (SRP) in waterbodies are also measured and, through comparison
with established thresholds known to cause ecological impacts, the levels are used to
identify where degradation might be expected to occur. The WFD threshold above
which SRP is expected to have a significant impact on the ecological condition of an
aquatic ecosystem varies between different waterbody types, but an average SRP
concentration above 50 ug/l would result in a WFD failure in any waterbody type. Bob Blaylock
The Exe Estuary at Topsham
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Water starworts (Callitriche spp) (top)
are just one group of macrophyte
plants that can cause problems when
they proliferate excessively. Phyto‐
benthic algae (diatoms) are particularly
sensitive to nutrient enrichment
(bottom).
20
On the provision of drinking water
In addition to the ecological impacts of nutrient enrichment leading to hypoxia and/or
anoxia in aquatic ecosystems, algal blooms can also result in other negative effects that
have significant consequences for the treatment and supply of drinking water.
These include their potential to damage property or water supply infrastructure, to
increase algae‐derived toxins in the water and to cause taste and odour problems, all of
which can result in increased drinking water treatment costs.
These impacts are particularly felt as blooms of algae and explosions of macrophyte
growth begin to die‐back at the end of the summer growing season or following the
depletion of nutrients and oxygen in the water column, when a number of so‐called
decomposition bi‐products can be released.
The three principal types of chemical pollutants produced as decomposition bi‐products
of this type are: (1) ammonia/ammonium (NH4), (2) soluble organic compounds (e.g.
methyl‐isoborneol (MIB) and geosmin) and (3) dissolved metal ions (e.g. manganese).
Ammonia and its ionised cationic form ammonium (NH4+) are naturally occurring
components of the nitrogen cycle that are generated in aquatic ecosystems by
heterotrophic bacteria as the primary nitrogenous end‐product of organic material
decomposition. In healthy aquatic ecosystems ammoniacal nitrogen is readily
assimilated by plants or converted through nitrification to nitrate, but in eutrophic lakes,
where elevated levels of nutrients are driving algal blooms and the development of
stratified hypoxic conditions, this process can be inhibited and ammoniacal nitrogen
then accumulates rapidly.
The presence of ammoniacal nitrogen in water can begin to have a toxic effect on
aquatic organisms (especially fish) at concentrations above 0.2 mg/l. In addition, when
abstracted for drinking water treatment, ammoniacal nitrogen concentrations above
0.2 mg/l can also cause taste and odour problems as well as decreased disinfection
efficiency during chlorination.
The increased chlorination required to remove ammoniacal nitrogen during the
treatment process can also lead to the indirect generation of dangerous chemical bi‐
products such as trihalomethanes (THMs), which are thought to have toxic and/or
carcinogenic properties and are very difficult to remove from the final treated drinking
water. Furthermore, increases in the nitrification of ammonia in the raw water, and the
increased consumption of oxygen that this entails, may also interfere with the removal
of manganese by oxidation on the filters, which can result in the production of mouldy,
earthy‐tasting water.
In 2002 the Environment Agency commissioned the University of Essex to undertake an
assessment of the environmental costs resulting from the eutrophication of fresh water
ecosystems in England and Wales. Their findings, summarised in the table below,
revealed that the total damage costs were in the range of £75 to £114 million.
Summary of the annual costs associated
with freshwater eutrophication in the
UK. Costs were calculated as ’damage
costs’ – i.e. the reduced value of clean
or non‐nutrient‐enriched water
(adapted from Pretty et al., 2002).
Cost categories Range of annual costs (£ million)
Social damage costs
Reduced value of waterside dwellings £9.83
Reduced value of waterbodies for commercial use (abstraction, navigation, livestock, irrigation and industry) £0.50 ‐ 1.00
Drinking water treatment costs (treatment and action to remove algal toxins and algal decomposition products) £19.00
Drinking water treatment costs (to remove nitrogen) £20.10
Clean‐up costs of waterways (dredging, weed‐cutting) £0.50 ‐ 1.00
Reduced value of non‐polluted atmosphere (via greenhouse and acidifying gas emissions) £5.12 ‐ 7.99
Reduced recreational and amenity value of water bodies for water sports, angling, and general amenity £9.65 ‐ 33.54
Revenue losses for formal tourist industry £2.94 ‐ 11.66
Revenue losses for commercial aquaculture, fisheries, and shellfisheries £0.029 ‐ 0.118
Health costs to humans, livestock and pets unknown
Ecological damage costs Negative ecological effects on biota (arising from changed nutrients, pH, oxygen), resulting in changed species composition (biodiversity) and loss of key or sensitive species
£7.34 ‐ 10.12
TOTAL £75.0 ‐ 114.3
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Mitigation measures & their efficacy There are a wide range of mitigation measures available for reducing nutrient inputs
into the aquatic environment.
Soil, land and slurry management
Limiting fertiliser and manure inputs to suit crop requirements prevents over‐use and
reduces the quantities of surplus nutrients entering the system. Mitigation measures to
limit nitrogen inputs to suit crop requirements have been shown to substantially reduce
nitrate losses from soil (Lord and Mitchell, 1998), but these methods are less effective in
reducing phosphorous concentrations in run‐off due to phosphorous build‐up in soil.
Mitigation measures to reduce nutrient loads through changes in agricultural land and
soil management practices include the use of fertiliser placement technologies and
avoiding application of fertiliser to high‐risk areas. There are also a variety of
conservation tillage techniques that can be implemented, with the aim of reducing
nutrient losses via surface run‐off.
Mitigation measures for improved soil, land and slurry management are listed below
and the evidence for their efficacy is summarised in the table below:
Implementation of conservation tillage techniques
Fertiliser spreader calibration Use of a fertiliser recommendation system
Use of fertiliser placement technologies
Re‐site gateways away from high‐risk areas
Do not apply fertiliser to high‐risk areas Avoid spreading fertiliser to fields at high risk times
Do not apply P fertiliser to high P index soils Install covers on slurry stores Increase the capacity of farm manure storage
Minimise volume of dirty water and slurry produced
Change from slurry to solid manure handling system
Reference Mitigation Measure Findings
Benham et al. (2007) Implementation of conservation tillage techniques
Mean losses in surface run‐off for
total nitrogen was reduced by 63%
ammonia was reduced by 46%
nitrate was reduced by 49%
total phosphorus was reduced by 73%
Daverede et al. (2004) Injection of slurry 93% reduction in dissolved reactive P in run‐off 82% reduction in total P in run‐off 94% reduction in algal‐available P in run‐off
Deasy et al. (2010) Tramline management Tramline management reduced nutrient and sediment losses by 72‐99% on 4 out 5 sites and were a major pathway for nutrient transfer from arable hill‐slopes
Goss et al. (1988) Direct drilling Winter losses of nitrogen was on average 24% less than for land that had been ploughed
Johnson and Smith (1996) Shallow cultivation (instead of ploughing) Decreased nitrogen leaching by 44 kg per hectare over a 5 year period
Pote et al. (2003) Incorporation of poultry litter in soil 80‐90% reduction in nutrient losses from soil
Pote et al. (2006) Incorporation of inorganic fertilisers into soil
Reduction of nutrient losses to the water environment to background levels
Shephard et al. (1993, 1996 and 1999), Goss et al. (1998), Lord et al. (1999)
Planting a green cover crop 50% reduction in nitrate losses compared to winter‐sown cereal. Uptake of nitrogen ranging between 10 and 150 kg per hectare
Withers et al. (2006) Ensure tramlines follow contours of the land across the slope
No significant differences in run‐off quantity, sediment and total phosphorous loads compared to areas with no tramlines
Zeimen et al. (2006) Ensuring a rough soil surface by ploughing or discing
Transport of soluble phosphorus in surface run‐off reduced by a factor of 2‐3 compared to untilled soils
The table below summarises key
findings of research into the efficacy of
mitigation measures aimed at limiting
nutrient losses by changing agricultural
land and soil management practices.
These findings are a result of research
carried out at either a plot‐ or field‐
scale.
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The Westcountry Rivers Trust have
produced a series of farm‐measure fact‐
sheets, which can be found on the
DEFRA website at—http://tinyurl.com/
kqpyctv.
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CASE STUDY River Otter Catchment Management Project The River Otter rises in the Blackdown Hills in East Devon and runs for approximately 25 miles southwest to the sea.
Below Honiton, the Otter enters its floodplain and runs south through several towns and villages before reaching the salt
marshes at Budleigh Salterton. In its lower reaches, the Otter becomes a gravel‐bed river that meanders through rolling
topography with mixed agricultural land use, including livestock, cereals, oil seeds, fruit and vegetables.
Issues
Due to the sandy nature of the soils in the Otter catchment, leaching of nitrate and pesticides is common. South West
Water (SWW) relies heavily on the lower Otter boreholes to meet local drinking water demands and many of these
boreholes have shown worrying trends in nitrate levels. Sediment and phosphate levels in surface waters are also high
and in need of attention.
High nitrate levels increase the burden of supplying potable water and, although the SWW Dotton treatment plant is
capable of blending and stripping excess nitrate from the extracted water, its capacity is limited. Reducing the nitrate
content in raw water will reduced this burden and its associated economic and environmental costs.
Delivery of Interventions
Farm visits were made to engage with farmers and explain the benefits of better
nutrient management. Where appropriate, farmers were provided with farm reports to
highlight priority areas likely to influence raw water quality and to provide advice on
management practices to reduce pollutant loads. From 2010‐2012, thirty‐seven farms
were visited and eight received farm reports. Events were also held to engage with the
farming community whilst at the same time to bolster the understanding of the project
aims. Events have included fertiliser spreader workshops, crop trial workshops and
visits to the SWW water treatment works.
Following the visit to the water treatment works one farmer commented that the
project was, “...very interesting. Our strategy has more influence on water quality than I
thought...”.
Monitoring & Outcomes
Focusing on the nitrate contribution from agriculture, a monitoring study was set up to assess the relative contributions
from different land use types within the catchment and to monitor changes in nitrate levels following farm visits.
Ten geographically diverse farmers kindly gave permission to use a single field on each of their farms for testing, pre‐ and
post‐winter. Each farm was chosen carefully to ensure a representative selection of land use types were included.
The nitrate testing sites were selected in 2010 and sampling was undertaken in November 2010, March and November
2011, March and November 2012 and March 2013. The difference in nitrate levels recorded in the soil between November
and March gives a value for nitrogen lost over winter.
The chart (left) shows that overall levels of nitrogen lost
from the soil has decreased significantly over the
monitoring period, with levels in 2012/2013 approximately
a third of the level lost over the 2010/2011 winter.
The amount of nitrogen used by the current crop has been
taken into account, where appropriate, and the remaining
fraction of nitrogen unaccounted for is considered to be
associated with the export of animal products, crops,
leaching, de‐nitrification and volatilisation. In most cases,
the nitrogen loss will mainly be associated with leaching,
volatilisation and de‐nitrification, all of which are
environmentally damaging.
While these results are encouraging, there are several other factors that could have contributed to this reduction, such as
the weather, and it is not possible to prove that these positive results are directly linked to interventions. However, they
do offer a snapshot of the problems faced in this area and certainly point towards a positive impact resulting from the
provision of nutrient advice on farm visits and in farm plans.
This monitoring work also provides invaluable data for the farmers participating in the project and helps to reinforce the
project aims, as demonstrated by positive farmer feedback.
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Management of livestock
In their Europe‐wide study into the sources of phosphorus inputs into rivers, Morse et al
(1993) estimated that the most significant contributions were from livestock, human
waste and fertiliser run‐off sources (see chart right).
Mitigation measures designed to reduce nutrients inputs from livestock are listed below
and the evidence for their efficacy is summarised in the table below:
Reduction in stocking density Reduction in dietary N and P intakes Exclusion of livestock from waterbodies and provision of alternative drinking
sources
Exclusion of livestock from poorly drained areas of land to prevent poaching and subsequent mobilisation of soils and nutrients
Reference Mitigation Measure Findings
Heathwaite and Johnes (1996)
Reduced livestock grazing density Phosphorous exports in surface run‐off was recorded as:
2 mg total P per m2 for ungrazed land
7.5 mg total P per m2 for lightly grazed land
291 mg total P per m2 for heavily grazed land
Huging et al. (1995) Reduce livestock grazing density There is a significant relationship between grazing intensity and nitrogen losses to water
Nitrogen leaching losses were reduced by 69%
Kurz et al. (2006) Exclusion of livestock from poorly drained areas of land to prevent poaching
Decreased concentrations of total nitrogen, organic phos‐phorous and potassium were measured in surface run‐off from un‐grazed areas when compared to grazed areas
Line (2003) Fencing the watercourse to exclude live‐stock combined with a 10‐15m buffer‐strip
Total organic nitrogen load decreased by 33%
Total phosphorous load decreased by 76%
Parkyn et al.(2003) Fencing the watercourse to exclude live‐stock
Streams within fenced off areas showed rapid improvement in visual water clarity and channel stability
Soluble reactive phosphorous decreased by up to 33% in some streams, although in others it increased
Total nitrogen decreased by up to 40% in some streams but increased in others
Sheffield et al. (1997) Provision of alternative drinking source for livestock
Total phosphorus load decreased by 54%
Total nitrogen load decreased by 81%
Exclusion of livestock from poorly drained areas of land to prevent poaching Poaching around feeding and drinking areas can lead to soil damage, as well as stock welfare and pollution problems,
particularly during wet periods. Simple management changes can help farmers to benefit from:
improved stock health and lower vet bills
reduced soil damage, erosion, runoff and watercourse pollution
improved grass production and nutritional value
reduced sward restoration costs.
reduced risk of damage to environmentally sensitive areas
CASE STUDY
Careful management of out‐wintered stock and equipment in order to avoid serious
damage to soils and sward was undertaken on 5 ha of grassland. Regular inspections,
particularly in wet weather allowed movement to better‐drained areas before serious
poaching occurred.
This resulted in 10% less grass to be restored, encouraged early recovery and
provided an early spring “bite”. Annual savings included 10% less grass to be
reseeded @ £54/ha and 10% less loss of forage@ £24/ha. The total saving for 5ha
was £390 with an immediate payback.
Sources of phosphorus in the EU
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Buffer Strips for nutrient pollution mitigation Creation of riparian buffer strips along watercourses is perhaps the most widely recommended mitigation method for
controlling diffuse pollution losses from agriculture. Consequently, research into the efficacy of buffer strips in reducing
pollutant load entering watercourses has been extensive.
Efficacy (% reduction)
Reference Location Buffer Width (m) Soil Texture Slope (%) Phosphorous Nitrogen
Abu‐Zraig et al. (2003) Canada 2 Silt loam 2.3 57‐64
5 47‐60
10 5 65‐72
15 2.3 55‐93
Barfield et al. (1998) USA 4.6 9 92
9.1 100
13.7 97
Barker et al. (1984) 79 99
Blanco‐Canqui et al. USA 0.7 Silt loam 4.9 44‐63 62‐77 (2004) 54‐72 35‐36
22‐53
4 77‐82 82‐83
81‐91 54‐70
71‐84
8 87‐91 88‐90
96‐99 83‐84
87‐95
Borin et al. (2004) Italy 6 Sandy loam 3 78 72
Cole et al. (1994) 2.4‐4.9 Silt loam 6 93
Dillaha et al. (1988) UK 4.6 Silt loam 11‐16 73 27
49
9.1 93 57
56
Doyle et al. (1977) UK 1.5 Silt loam 10 8 57
62 68
A riparian buffer strip can be defined as a corridor of natural vegetation
between agricultural land and a watercourse. They act as barriers to surface
flows and therefore impact on delivery of pollutants to watercourses. The
rate of surface run‐off is slowed as the water meets resistance from
vegetation and flows over rougher and more porous surface material.
The substantial root systems beneath the surface also increase the likelihood
of infiltration. Slower flowing water has a reduced capacity for the transport
of particulate matter and, as a result, there is increased deposition of
sediment prior to surface flows reaching the watercourse.
CASE STUDY
There are numerous factors that may influence the performance of buffer strips in reducing pollutant load. These include
the characteristics of the incoming pollutants, the topography and soils of the land surrounding the watercourse and the
characteristics of the buffer strip itself, for example vegetation type and width. In addition, seasonal variations in
meteorological conditions and farming practices can also influence buffer strip performance.
The findings of the many studies into the efficacy of buffer strip in mitigating nutrient losses from farmland are shown in
the table below. These results illustrate the variability inherent in quantifying the efficacy of buffer strips in reducing
nutrient inputs to watercourses, with the range of efficacy for total phosphorus varying from 30 to 95% and for total
nitrogen, from 10 to 100%.
Continued over page...
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Efficacy (% reduction)
Reference Location Buffer Width (m) Soil Texture Slope (%) Phosphorous Nitrogen
Duchemin & Madjoub 3 Sandy loam 2 85 96
(2004) 41
9 87 85
57
Edwards et al. (1983) UK 30 ‐ 2 47‐49
Knauer & Mander (89) Germany 10 ‐ 70‐80 50
Kronvang et al. (2000) Denmark 0.5 Sandy loam 7 32
29 100
Kronvang et al. (2004) Norway 5 Silt loam 12‐14 46‐78
10 80‐90
Lee et al. (2000) 7.1 Silty clay loam 5 28‐72 41‐64
Lim et al. (1998) USA 6.1 Silt loam 3 74.5 78
76.1
12.2 87.2 89.5
90.1
18.3 93.0 95.3
93.6
Magette et al. (1987) UK 9.2 Sandy loam 41 17
McKergow et al. (03) Australia Loamy land <2 6 23
Muenz et al. (2006) USA 25 Sandy clay loam 16.5 50 50
Patty et al. (1997) France 6 Silt loam 7‐15 22 47
18 89 100
Parsons et al. (1991) USA 4.3‐5.3 ‐ 26 50
Schmitt et al. (1999) 7.5 Silty clay‐loam 6 48 35
19
15 79 51
50
Schwer & Clausen 26 Sandy loam 2 89 92 (1989) 92
Smith (1989) New Zealand 10 ‐ 55 67
80
Syversen (1992) Norway 5 ‐ 65‐85 40‐50
10 95 75
Thompson et al. UK 12 ‐ 4 44
(1978) 36 70
Vought et al. (1995) Sweden 5 ‐ 40‐45 10‐15
10 65‐70 25‐30
15 85‐90 40‐45
Young et al. (1980) UK 27 ‐ 4 76‐96 82‐94
Zirschky et al. (1989) 91 Silt loam 38
Buffer Strips for nutrient pollution mitigation...continued….
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Delivery of interventions
All thirteen farms in the Mill Creek catchment were paid to implement agricultural BMPs under a contract that calls for 10
year maintenance of the practices in return for the technical and financial assistance. Additionally two deed restrictions
were applied to two barns.
Mill Creek, Pennsylvania State, USA The Mill Creek catchment drains into the Stephen Foster Lake in the northern mountain region of Bradford County,
Pennsylvania, USA. While greater than half of the surrounding 26 km2 catchment area is used for agricultural production,
the remainder is predominantly forested.
Over time Mill Creek has deposited excess sediment and nutrient run‐off into the 28 Ha lake. As a result, Pennsylvania
added Stephen Foster Lake to the state’s list of impaired waters in 1996 for nutrient and sediment runoff due to
agricultural activities. Subsequently, a Total Maximum Daily Load (TMDL) for the lake that called for reductions of 49%
for phosphorus was established.
CASE STUDY
Catchment management plan
Several computer models were used to estimate the load reductions that might result from Best Management Practices
(BMPs) being implemented. With the combination of these efforts, the nutrient runoff was estimated to be reduced by
52% and sediment runoff reduced by 59%, exceeding the reduction recommended in the TMDL.
The suggested BMPs were primarily aimed at the control of nutrient inputs from animal wastes, which contribute an
estimated 175 kg of phosphorus (10% of the total annual load). Erosion control, to further reduce nutrient and sediment
loadings to the lake, are estimated to reduce the total phosphorus load in it by an additional 10%.
Manure and runoff from a previously severely degraded manure handling area is now contained and directed to the new manure storage facility for field application.
Farm feedlot before and after infrastructure improvements.
Upstream of the lake, farmers and the Bradford
County Conservation District installed 9 miles of
stream fencing and alternative water supply
systems to help prevent cattle from wandering
into waterways.
Agricultural crossings, to swiftly move cattle
across streams and prevent the animals from
grazing near waterways and destroying
riverbanks were also constructed.
Project partners also built 11 systems to store and
treat animal waste, planted riparian buffers, and
restored 2,500 feet of stream channel. The
Bradford County Conservation District identified
over $518,000 worth of improvements to be
delivered over the 11 farms.
Growing Season Total Phosphate (TP) loads (kg) entering Stephen
Foster Lake before (1994‐95) and after (2004, 2005, 2006 & 2008‐09)
delivery of Best Management Practices
Monitoring & Outcomes
Pennsylvania Department for Environmental Protection conducted
biological monitoring and analysis of Mill Creek. Across the
catchment there were four sample stations collecting monthly
readings for pH, conductivity, a suite of Phosphate and Nitrogen
measurements, alkalinity, total suspended solids and temperature.
Since 2004 the growing season Total Phosphate (TP) load entering
Stephen Foster Lake declined by 50 to 90% relative to the original
Phase I study (1994‐95) load. As a result of these reductions, the
lake has been in compliance with its total phosphorus TMDL
targeted, growing season load since 2005.
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CASE STUDY Upper Tamar Lakes Farm Intervention Assessment The farm is located in the Tamar Lakes Catchment and has a first order stream which runs next to the yard. The 98 Ha of
land is comprised of gently undulating pasture (60 Ha), arable (10 Ha in maize and 20 Ha in winter and spring barley) and
woodland. The main farm enterprise is a dairy with 130 milkers and 50 followers. There are around 60 bull calves and the
farmer has winter sheep kept over October to February. The dairy herd are housed over the winter months (September
to March) and the farm has approximately 4 months slurry storage capacity. Slurries are separated into a slurry lagoon
and three dirty water pits. The slurry is spread over the land by the farmer using the farm’s own machinery.
Intervention
Although the farmer demonstrated several good practices, there was a problem with his slurry store, which was
outdated, could not cope with the demands of the modern dairy and did not afford the environment with enough
protection against leaks and overflowing episodes. In this instance the ‘weeping wall’ slurry lagoon was placed too close
to watercourse and therefore ran the risk of polluting it.
In this situation the solution was to create a solid walled lagoon, which being slightly larger, allowed for slurry to be
removed and spread at appropriate times, as well as giving protection to the watercourse. The photographs below show
the formalisation of the slurry pit from an inadequate weeping wall system to a concrete, bunded system in early 2008.
Monitoring
Monitoring of aquatic invertebrates was undertaken and taxa scored against the BMWP scoring system (Biological
Monitoring Working Party ‐ National Water Council, 1981) to assess changes in agricultural pollution. Data was collected
over the term of the project from 2007 to 2009 and further monitoring was undertaken in 2012 to assess the long‐term
effects. Two sites one upstream and one downstream (separated by around 100m) allowed assessment of the impact of
the intervention.
Results
The results of the BMWP scores show that there is a
significant negative impact on water quality between
the upstream score (blue line) and the downstream
score (red line) in the first two samples before the
intervention. After the intervention in Early 2008 (green
line) the difference between the upstream and
downstream reduces suggesting that there is little
water quality difference between sites.
Although the 2012 upstream and downstream readings
are lower than the 2008 and 2009 readings there is still
little difference between the two suggesting that there
continues to be no impact from the site in terms of
water quality.
Monitoring
The river is a small first order stream, which goes part way to explaining the relatively low BMWP scores when compared
to second and third order streams in the area. It is highly likely that weeping wall slurry pit was having a significant
negative impact on downstream water quality and the intervention of formalising the pit reduced the difference between
the two survey sites, both immediately after the intervention and four years later. The decrease in upstream and
downstream scores in 2012 is likely to be wider environmental factors such as an increase summer rainfall.
BMWP scores upstream (blue) and downstream (red) of a farmyard with an inadequate slurry pit with weeping wall. The slurry pit was updated in early 2008 (shown as an green line) after which the difference between the two scores reduces. Whilst 2012 figures are reduced compared to 2008 & 2009 the difference between upstream and downstream is less than before intervention.
NUTRIENTS & ALG
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SUSPENDED SOLIDS & TURBIDITY
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Turbidity is a measure of how much suspended material there is in water. Turbidity is
reported in nephelometric units (NTUs), which are measured by an instrument
(turbidimeter or nephelometer) that estimates the scattering of light by the suspended
particulate material.
There are many factors that can cause the turbidity of water to increase, but the most
common are the presence in the water column of algae, bacteria, organic waste
materials (including animal waste and decomposing vegetation) or silt (soil or mineral
sediments). These materials are often released into the water following disturbance of
the river or lake substrate, but they can also enter the water as a result of erosion and
run‐off from the land.
Sources of suspended solids Numerous methods have been developed to identify the sources of suspended solids
and the dynamics of sediment transport in rivers. These methods, which vary greatly in
the spatial scales at which they can be applied, include:
Fine sediment risk modelling. Uses topographic, rainfall and land‐use data to
identify areas where a high propensity for the lateral flow of water over the land is
likely to mobilise fine sediment and transport it to the river.
Sediment load sampling. Water sampling to determine suspended solid load and the
contribution being made by different sub‐catchments.
Sediment river walkover surveys. Rapid river surveys typically undertaken in wet
weather to identify sources of sediment and organic material entering the river.
Source apportionment using fluorescent, chemical and genetic signatures.
Pioneered by research organisations, such as ADAS Water Quality and the University
of Plymouth, these approaches allow the areas of river bank or land that are
contributing to the in‐channel sediment load to be identified.
Overall these studies reveal that the sediment load in rivers is derived from point or
diffuse sources in three principal locations:
Material from the river channel and banks
Soil and other organic material washed off from the surface of surrounding land
Particulate material from anthropogenic sources; including point sources, roads,
industry and urban areas.
SUSPENDED SOLIDS & TURBIDITY
SUSPENDED SOLIDS
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Examples of sediment being mobilised
from the land surface (in this case a
country road; top) and entering a
watercourse (bottom).
30
SCIMAP: A fine sediment risk modelling framework A simple and robust fine sediment risk model can be extremely beneficial as it helps us to target and tailor both further
monitoring work and catchment management interventions.
The SCIMAP fine sediment risk model was developed through a collaborative project between Durham and Lancaster
Universities. The SCIMAP Project was supported by the UK Natural Environment Research Council, the Eden Rivers Trust,
the Department of the Environment, Food and Rural Affairs and the Environment Agency.
The SCIMAP model gives an indication of where the highest risk of sediment erosion risk occurs in the catchment by (1)
identifying locations where, due to landuse, sediment is available for mobilisation (pollutant source mapping) and (2)
combining this information with a map of hydrological connectivity (likelihood of pollutant mobilisation and
transportation to receptor).
The combination of the sediment availability and hydrological connectivity maps results in a final fine sediment erosion
risk model that is useful for targeting field surveys and the mitigation of erosion risk at catchment, farm or field scale.
CASE STUDY
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Impacts of suspended solids & turbidity On the health of aquatic ecosystems
The most obvious effect of turbidity on the quality of water is aesthetic, as it gives the
appearance that the water is dirty. However, suspended material in the water of rivers
and lakes can also cause significant damage to the ecology of the aquatic ecosystem by
blocking the penetration of light to aquatic plants, clogging the gills of fish and other
aquatic organisms, and by smothering benthic habitats. This has the effect of
suffocating the organisms and eggs that reside in the interstitial spaces of the substrate.
Furthermore, where elevated turbidity is the result of algal or other microbial growth
these organisms can also have direct toxic effects on the ecology of the ecosystem (e.g.
toxic blue‐green algae) or indirect effects through the eutrophication of the water
column.
Suspended material in rivers and streams can also have a significant impact on the
ecological health, productivity and safety of estuarine and coastal environments in the
downstream sections of their catchments.
On the provision of drinking water
In addition to their ecological impacts, turbidity and suspended solids also add
significantly to the intensity and cost of drinking water treatment as they can
accumulate in and damage water storage and treatment infrastructure.
Suspended sediment must also be eliminated from the water for effective chlorine
disinfection of the water to be achieved.
Furthermore, particulates in suspension also carry other damaging and potentially
dangerous pollutants, including metals, pesticides and nutrients (such as phosphorus).
Once removed from the water, the resulting sludge, which may be contaminated with
these other pollutants, must also be disposed of in a safe manner and this can be
extremely costly when it is produced in large volumes.
In light of the impact that turbidity and suspended solids have on the efficiency and cost
of water treatment and on the aesthetic quality and safety of the final drinking water, it
is little surprise that the UK Water Supply (Water Quality) Regulations 2000 indicate
that treated drinking water should not have turbidity above 1 NTU.
In addition, the EC Directive on the Quality Required of Surface Water Intended for the
Abstraction of Drinking Water 1975 (75/440/EEC) gives guidance that raw water should
not have Total Suspended Solids (TSS) above a concentration of 25 mg/l without higher
levels of treatment being undertaken before consumption.
In the water treatment processes undertaken at water treatment works, the suspended
material in the raw water, and hence the turbidity, is removed by coagulation induced
by the addition of various coagulants (e.g. alum). The level of turbidity in the raw water
has a significant effect on the coagulation process. When turbidity is elevated, the
amount of coagulant added must be increased and, at many treatment works, turbidity
(along with colour) is one of the parameters that is constantly measured and used to
calibrate the dose of coagulant used in the treatment process.
Sediment pressure is felt at the
sediment or sludge press of the water
treatment works (top). This generates
large quantities of sediment or sludge
‘cake’ which must then be safely
disposed of (bottom). Data indicate
that raw water polluted with
suspended sediment can double or
even triple the amount of sludge
created at a works.
Sediment accumulation on a riverbed
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Water quality & biological monitoring to determine sediment impacts In 2002, a sediment ‘fingerprinting’ study undertaken on 18 rivers in England and Wales revealed that 69% of the
sediment load in the River Tamar was derived from land‐surface sources and just 31% was from river channel/bank
sources (see below). The study found that this ratio was in stark contrast to the findings in other Westcountry rivers. For
example, in the other rivers of the wider Tamar catchment, the Tavy and Plym, just 10% and 8% of the sediment
respectively were derived from surface sources (see below).
The authors believed that the predominance of land surface sources in the Tamar catchment was a direct result of the
catchments high stocking densities, which subject surface soils beneath pasture to severe poaching and subsequent
erosion during rainstorms.
CASE STUDY
Invertebrate community assessment
It has long been recognised that benthic macro‐invertebrates are sensitive to the accumulation of fine sediment in rivers
(Cordone & Kelly, 1961; Chutter, 1969; Richards et al., 1997) and in recent years the Proportion of Sediment‐sensitive
Invertebrates (PSI) index has been developed as a biological indicator for the assessment of fine sediment accumulation
in rivers. The PSI index assigns families and species of benthic macro‐invertebrates a sensitivity rating from 0‐100 for
sediment according to their anatomical, physiological and behavioural adaptations. The scores for the taxa found in a
sample are summed to give the sample an overall PSI score.
The development of the PSI index and its incorporation into
the RIVPACS database in 2011 has allowed invertebrate
sampling to be used as a biological method for the assessment
of fine sediment load across the Crownhill WTWs catchment.
Duplicate (two season) invertebrate samples were taken at 30
locations across the catchment. Each sample was identified to
species level and the PSI index calculated.
At each sampling location environmental measurements were
also taken and entered into the River Invertebrates Analysis
Tool (RICT), which uses the RIVPACS database to predict what
the PSI index score should have been for that site.
The Ecological Quality Ratio (EQR) for the sample is then
calculated as the ratio between the observed and the expected
(O/E) score.
The findings of this invertebrate study (above right) show that several waterbodies in the Tamar catchment appear to
have invertebrate assemblages that are impacted by fine sediment. The observation that the most impacted areas are in
the Upper Tamar, Ottery and Lower Tamar sub‐catchments is entirely in accordance with our previous findings and with
the Environment Agency WFD Reasons for Failure database.
Water chemistry sampling
To further investigate the sources of
suspended solids in the Tamar catchment, a
telemetrically linked multi‐parameter probe
(sonde) was installed to identify occasions
when heavy rainfall had triggered high‐flow
events in the river and a corresponding spike
in the turbidity of the river had occurred.
Water quality samples were then taken and
analysed to identify the relative suspended
solids contribution being made by each sub‐
catchment at those times (right).
The provenance of interstitial sediment samples
collected from study catchments in south‐west
England. Source apportionment was performed
using the sediment fingerprinting technique
(adapted from Walling et al, 2002).
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Sediment mitigation measures & their efficacy There are a wide range of mitigation measures available for reducing sediment loads
and turbidity in the aquatic environment. These measures are primarily aimed at
reducing the availability of sediment sources, at reducing the likelihood of material
being mobilised and at disconnecting the pathways via which particulate matter (mainly
soil) is carried into watercourses. Measures include:
Early harvesting and establishment of crops in Autumn
Cultivation of land for crops in Spring rather than Autumn
Adopt a reduced cultivation system Cultivate compacted tillage soils
Cultivate and drill across the slope Leave autumn seedbed rough
Manage over‐winter tramlines
Loosen compacted soil layers in grassland fields
Reduce field stocking rates when soils are wet
Construct troughs with a firm but permeable base
Move feeders at regular intervals
A wide and varied body of research has been conducted over the past 40 or so years in
the attempt to quantify and understand the processes of soil erosion on agricultural land
in the UK and how it can be reduced.
There are numerous conservation tillage techniques that have been shown to reduce
soil erosion and it is well documented that rough soil surfaces on arable land reduce run‐
off and increase the water holding capacity of the soil, thereby preventing mobilisation
and transportation of particulate matter to watercourses.
The table below summarises the key findings from the Mitigation Options for
Phosphorus and Sediment (MOPS) project— a collaborative research project, funded by
the UK Department for Environment, Food and Rural Affairs (DEFRA), and involving
four project partners, Lancaster University, ADAS, the University of Reading and The
Game & Wildlife Conservation Trust Allerton Project. The project was designed to test
the efficiency of a range of mitigation measures aimed at reducing sediment through
conservation tillage techniques.
Mitigation measure Reduction in suspended sediment
Contour cultivation 64‐76%
Minimum tillage 37‐98%
Tramline modification 75‐99%
Beetle bank construction 16‐94%
Summary of key findings from the
Mitigation Options for Phosphorus and
Sediment (MOPS) project that aimed to
test the efficiency of a range of
mitigation measures aimed at reducing
sediment through conservation tillage
techniques. (From Stevens and Quinton,
2008.)
Direct drilling: a minimum tillage technique Direct drilling is a system of seed placement where soil is left undisturbed with crop residues on the surface from harvest
until sowing. Seeds are delivered in a narrow slot created by discs, coulters or chisels.
Direct drilling offers the potential for savings over traditional plough‐based crop establishment systems due to lower
costs associated with machinery, energy, soil damage, soil erosion, nitrogen leaching and agrochemical losses. It also
offers substantial environmental benefits, such as increased soil fauna and habitats for birds, as well as a reduced risk of
watercourse pollution.
CASE STUDY
System Depth (cm)
Cost (£/ha)
Time (mins/ha)
Cereal yield (%)
Plough 15‐35 100‐135 150‐220 100
Direct drilling 0 30‐45 25‐40 99.2
The Soil Management Initiative (SMI) Guide to
Managing Crop Establishment says the method gives
‘a dramatic reduction in establishment costs and an
increase in work rate, improved control of black grass
and reduced slug activity’ Source Cranfield University
A sub‐soiler (top) and a rough
cultivation (bottom) ‐ both good
methods for maintaining good soil
structure throughout the year
Blonder1984
Amanda Slater
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Buffer Strips for sediment pollution mitigation As we have described for nutrient pollution, the efficacy of buffer strips in reducing suspended sediment loads in
watercourses has also been the subject of a significant body of research. The findings of this research, summarised in the
table below, indicate that buffer strips can reduce sediment losses from between 33 and 100% in plot and field
experiments and that percentage reduction is primarily influenced by buffer strip width.
CASE STUDY
Reference Location Buffer Width (m) Soil Texture Slope (%) Efficacy (% Sediment reduction)
Arora et al. (1996) USA 1.52 Silty clay loam 3 40‐100
Blanco‐Canqui et al. USA 0.7 Silt loam 4.9 81‐92
(2004) 4 94
8 98‐99
Borin et al. (2004) Italy 6 Sandy loam 3 93
Dillaha et al. (1988) UK 4.6 Silt loam 11‐16 63
9.1 78
Duchemin & Madjoub 3 Sandy loam 2 87
(2004) 9 90
Ghaffarzadeh et al. (92) 9.1 7‐12 85
Homer & Mar (1982) USA 61 80
Kronvang et al. (2000) Denmark 0.5 Sandy loam 7 62
29 100
Kronvang et al. (2005) Norway 5 Silt loam 12‐14 60‐87
10 90
Lee et al. (2000) 7.1 Silty clay loam 5 70
Lim et al. (1998) USA 6.1 Silt loam 3 70
12.2 89.5
18.3 97.6
Lynch et al. (1985) 30 75‐80
Jin et al. (2002) USA 19 4 62
17 6 38
4 4 64
Magette et al. (1987) UK 9.2 Sandy loam ‐ 72
McKergow et al. (2003) Australia Loamy land <2 93
Muenz et al. (2006) USA 25 Sandy clay loam 16.5 81
Patty et al. (1997) France 6 Silt loam 7‐15 87
18 100
Schellinger & Clausen (1992)
22.9 33
Schmitt et al. (1999) 7.5 Silty clay loam 6 63
15 93
Schwer & Clausen (1989) 26 Sandy loam 2 95
Smith (1989) New Zealand 10 87
Verstraeten et al. (2002) Belgium 20 Silty clay loam <2 41
Wong & McCuen (1982) 30.5 2 90
61 95
Young et al. (1980) UK 27 4 67‐79
Ziegler et al. (2006) Thailand 30 Sandy loam 34‐87
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PESTICIDES PESTICID
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PESTICIDES Chemicals that are used to kill or control ‘pest’ organisms are referred to generically as
‘pesticides’. In agricultural and horticultural uses these chemicals are grouped according
to their target organisms and include herbicides (weeds), insecticides (insects),
fungicides (fungi), nematocides (nematodes) and rodenticides (vertebrate poisons).
In agricultural applications, pesticides are widely used to protect crops and livestock
from pests and diseases and, when used with care, they can deliver substantial benefits
for society: increasing the availability of good quality, reasonably priced food and well
managed urban environments.
Despite the potential benefits of pesticide use, however, it is important to note that,
following their application, large amounts of pesticide often miss their intended target
and are lost into the environment where they can contaminate non‐target species, air,
water and sediments. Pesticides are, by design, harmful to living organisms and so,
when they do accumulate in these non‐target locations, they can pose a significant
threat to ecosystem health, biodiversity and human health if the risks are not accurately
assessed and appropriate measures taken to minimise them.
Sources of pesticides Pesticide pollution occurs primarily through two routes:
Point agricultural sources. Such as leakage, spillage or accidental direct application to a watercourse (for example as the result of spray drift)
Diffuse agricultural sources. Where active ingredients are washed off or leached
from the soil following their application.
The threat posed by an individual pesticide is also dependent on the unique intrinsic
properties of the active ingredients, which determine the specific risk they pose in terms
of water pollution and the ease of their subsequent removal from drinking water. These
intrinsic properties include:
Pesticide half‐life. The more stable the pesticide, the longer it takes to break down
and the higher its persistence in the environment.
Mobility & solubility. All pesticides have unique mobility properties, both vertically
and horizontally through the soil structure. Many pesticides are designed to be
soluble in water so that they can be applied with water and easily absorbed by the
target. A pesticide with high solubility also has a far higher risk of being leached out
of the soil and into a watercourse. In contrast, residual herbicides have lower
solubility to facilitate their binding to the soil, but their persistency in the soil can also
cause problems.
Mecoprop (herbicide)
MCPA (herbicide)
Glyphosate (herbicide)
Cyromazine (insecticide)
PESTICID
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In addition to the intrinsic characteristics of each pesticide, there are also several
extrinsic factors that can determine whether a pesticide poses a risk in a particular
situation:
Rainfall. High levels of rainfall increases the risk of pesticides contaminating water.
Water moving across or through the soil can wash pesticides into watercourses or
they can be transported into the water bound to treated soil via soil erosion.
Microbial activity. Pesticides in the soil are broken down by microbial activity and
this degradation is expedited where the levels of microbial activity are high due to
the presence of high numbers of microbes or elevated soil temperature. Pesticide
residues can also be degraded through evaporation and photo‐decomposition.
Application rate. The more pesticide that is applied, the longer significant
concentrations remain available to be transported into the water.
Treatment surface. Pesticides are generally designed to be applied to soil‐based
systems where they are held before being taken up by the target organism. When
pesticides are applied to non‐porous surfaces (such as concrete or tarmac) or to soil
that is degraded, they are not absorbed by the soil and are therefore particularly
vulnerable to mobilisation into watercourses following rainfall.
Assessing pesticide pollution risk using a spatial model The principal aim of this approach is to identify areas where the use of pesticides applied to the land represents a
pollution risk due to an elevated likelihood that they will be mobilised and transported through or over the soil and into a
watercourse.
A number of proprietary tools and modelling approaches have been developed to assess the spatial risk of pesticide
pollution. These include the Cranfield University CatchIS tool, the ADAS Pesticide Risk Assessment Model and the GfK
Kynetec i‐MAP Water system, but all are essentially based on similar conceptual models.
CASE STUDY
We used the i‐MAP Water system to model pesticide application
rates across the sub‐catchments of the Tamar catchment. It is
generally accepted that, while the i‐MAP dataset is robust at
catchment or sub‐catchment scale, its aggregation to a finer
scale than the sub‐catchment level would result in significant
inaccuracy in the final model.
To achieve our modelling aim we developed a spatial mapping
protocol (summarised right), which is essentially based on the
application rate of the pesticide (derived from the i‐MAP system),
the landuse for which it is used, the propensity of the soil to
release pesticides by leaching or run‐off, and the hydrological
connectivity of the land.
Using this method we have developed risk models for all of the active ingredients detected in the Crownhill water
treatment works catchment. Risk maps derived for two acid herbicides; Mecoprop and MCPA, and one neutral herbicide;
Chlorotoluron are shown below.
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Assessing pesticide pollution load using passive sampling Taking samples of river water using the conventional method of filling bottles by
hand can be costly and time‐consuming. The results obtained from these ‘spot’
samples can, at best, only provide a snapshot of the concentration target compounds
which may be present at the time of sampling.
Subsequent interpretation of the analytical results obtained is also difficult (was it the
leading edge of a pollutant plume, the peak, or the trailing edge?) and the time lag
between these results and repeat samples or remedial action inevitably means the
environmental investigation is reactive in nature.
Recently, a number of alternative and innovative monitoring strategies have been
proposed to overcome these challenges. In particular, research is focusing on the use
of passive samplers which can be deployed alone or, more often, in conjunction with
spot sampling to provide addition data on water quality and pollutant loads in rivers.
CASE STUDY
Recently, a research collaboration between South West Water, the University of
Portsmouth, Natural Resources Wales and the Westcountry Rivers Trust has been
established to use the ChemcatcherTM passive sampler (developed at the University)
to investigate water quality in this area.
Chemcatcher™ is a small plastic device fitted with a specifically tailored receiving‐
phase disk that has a high affinity for the target compounds of interest. Different
phases are available to sequester non‐polar (e.g. poly‐aromatic hydrocarbons and
some pesticides) and polar pollutants (e.g. pharmaceuticals and personal care
products), heavy metals (e.g. cadmium, copper, lead and zinc) and some radio‐
nuclides (e.g. caesium).
In practice, the receiving phase disk is overlaid with a thin diffusion‐limiting
membrane. These devices can be used to obtain the equilibrium concentration of the
pollutants or more typically the time‐weighted average (TWA) concentration over
the sampling period.
The first riverine trials using the ChemcatcherTM involved investigating
pesticides along the River Exe; a river designated as a WFD Article 7
Drinking Water Protected Area (DrWPA) with additional Safeguard
Zone (SGZ) status that requires a formal ‘action plan’ to be drawn up
by the Environment Agency. Here the aim was to ‘field test’ the
technique and hopefully provide an understanding of where the worst
problem pesticide loadings and locations were.
Over a two‐week period in early May 2013, timed to coincide with
known agricultural applications and forecasted rainfall, a number of
devices were deployed along much of the length of the river.
ChemcatcherTM samplers were housed in a number of specially
fabricated metal cages supplied by Anthony Gravell, Technical
Specialist at Natural Resources Wales Llanelli Laboratory, who
specialises in passive sampling in conjunction with HPLC‐MS
techniques for the analysis of pesticides, pharmaceuticals and
endocrine disruptors in various environmental compartments. Each
cage held three replicate sampling devices and was weighted to ensure
stability (see images right).
Prior to the trials, researchers at the University and South West Water’s
Organics Laboratory worked together to identify a receiving phase disk
capable of sequestering a group of nine specific pesticides that are
commonly detected in raw waters in the South West.
Prior to the field deployment, laboratory tests were undertaken using a large tank filled with River Exe water and spiked
with known concentrations of the pesticides under investigation. Here the aim was to measure the uptake kinetics (and
hence the sampler uptake rates) of these chemicals over a two‐week period. Once these data were available, they were
then used to estimate the TWA concentrations of these pollutants in the river over the field trial period.
PESTICID
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Assessing pesticide pollution pressure using an invertebrate index: SPEAR Another approach we have adopted is the assessment of invertebrate assemblages using the newly developed SPEcies
At Risk ‐ Pesticides (SPEARPESTICIDES) index (Liess and von der Ohe, 2005). This index assesses the degree to which the
invertebrate assemblages in the river are being affected by the presence of pesticides (and insecticides in particular) using
the life‐history and physiological traits to develop sensitivity scores for each species.
The continuous exposure of the invertebrate fauna in a stream to the pesticide load in the water makes them an excellent
indicator of pesticide pressure across a catchment in a way that water quality sampling cannot achieve unless undertaken
with very high frequency.
CASE STUDY
In 2011, the SPEARPESTICIDES index was also added to the River
InVertbrate Prediction and Classification System (RIVPACS)
database and this facilitated its use in the same year as a
biological method for the assessment of pesticide pressure across
the Crownhill water treatment works catchment.
Invertebrate samples taken across the catchment were identified
to species level and the SPEARPESTICIDES index calculated. The
River Invertebrates Analysis Tool (RICT) was then used to predict
what the SPEARPESTICIDES index score should have been for that
site and the Ecological Quality Ratio (EQR) for the sample
calculated as the ratio between the observed and the expected
(O/E) score.
The findings of the Crownhill WTWs catchment SPEARPESTICIDES
invertebrate study are summarised in the map (right).
Impacts of pesticides On the health of aquatic ecosystems
Pesticides contain active ingredients designed to kill certain groups of organisms and,
as such, there is significant potential for them to pose a threat to the health of other
non‐target species (including humans), habitats and ecosystems when they accumulate
in the environment.
Direct effects of pesticides on vertebrates have been greatly reduced since the phasing
out of organochlorines, but there are a number of active ingredients, such as the
molluscicide methiocarb, which have been shown to exert toxic effects on vertebrate
non‐target species (Johnson et al., 1991).
Many herbicides are also known to have negative impacts on invertebrate abundance
and species diversity (Chiverton and Sotherton, 1991; Moreby, 1997), while insecticides
have been shown to have significant impacts on both terrestrial and aquatic
invertebrate communities (e.g. Moreby et al., 1994). Some fungicides have also been
implicated in reducing invertebrate abundance (e.g. Reddersen et al., 1998).
Other studies (Williams et al., 1995) have shown that pesticide flushes can occur at the
headwaters of streams, where stream fauna could be affected. This is of particular
concern because such waters are otherwise of high quality and may be fish nursery
grounds.
Most recently, in 2013, an extensive analysis of the effects of pesticides on communities
of stream invertebrates in Europe and Australia found that they caused significant
effects on both the species and family richness, with losses in species richness of up to
42% recorded (Beketov et al., 2013).
As a result of these findings, the Water Framework Directive sets thresholds for many
key pesticides, such as Diazinon, Linuron and Cypermethrin, above which they may be
expected to be damaging the aquatic environment and/or pose a threat to human
health (so‐called ‘specific pollutants’). The WFD also sets targets for several high
toxicity (and largely banned) pesticides, such as Atrazine and DDT, which are classified
as ‘priority’ or dangerous substances under the EU Dangerous Substances Directive.
PESTICID
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On the provision of drinking water
Water companies are required by law to assess the risk that pesticides pose to each of
their raw water sources and also to monitor these sources for the presence of any of
these compounds.
The European Drinking Water Directive stipulates that there must be no individual
pesticide detected in drinking water at concentration over 0.1 μg per litre. However,
over recent decades, as a result of this stringent standard, the continued contamination
of river and ground water sources with pesticides has driven water companies to invest
in ever more advanced water treatment processes to remove them from drinking water.
There are several methods available for the removal or reduction of pesticide
concentrations in treatment of drinking water. Blending with water from an un‐
contaminated source can be effective as can blending treated water, but these methods
often require lengthy and costly transfers of water or are simply not feasible.
At the water treatment works, the methods available for the reduction of pesticide
concentrations can be divided into adsorption processes, biological processes,
destruction processes and physical removal processes. These include:
Granular activated carbon (GAC) ‐ adsorption Powdered activated carbon (PAC) ‐ adsorption
Ozone‐GAC – destruction/adsorption/biological
Ultraviolet irradiation ‐ destruction Advanced oxidation ‐ destruction Nano‐filtration‐reverse osmosis – physical removal (size exclusion)
All of these processes are expensive to undertake, in terms of both the infrastructure
investment required and their running costs, and all are highly energy and resource
intensive.
Furthermore, there are a number of pesticides for which these high‐intensity processes
can remain ineffective (such as metaldehyde; see below) and there remains a
considerable risk that these contaminants could still be passed on into the final treated
water supplied to customers if further precautions are not taken.
Metaldehyde is a selective pesticide
used by farmers and gardeners to
control slugs and snails in a wide variety
of crops. Technically it is known as a
‘molluscicide’ and its action is very
specific to slugs and snails)
Metaldehyde is sold under a variety of
brand names in pellet form.
Metaldehyde is an issue for water
companies, because pellets applied to
crops on land can find their way into
drains and water courses either directly
during application or as a result of run
off during high rainfall events. Levels of
metaldehyde have been detected in
trace concentrations in the rivers or
reservoirs at levels above the European
and UK standards set for drinking
water. Current drinking water
treatment methods are not effective at
reducing the levels of metaldehyde in
water. There have been occasions when
very low levels of metaldehyde have
been detected in treated drinking
water. These levels are extremely low –
the highest being around 1ug/l and
mostly much lower. However the levels
are above the European and UK
standards for pesticides in drinking
water that is set at 0.1ug/l.
Advanced water treatment solutions
required to remove pesticides from
drinking water include powdered
activated carbon (top), granular
activated carbon (GAC) filters (middle)
and ultrafiltration (bottom).
PESTICID
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Pesticide mitigation measures & their efficacy High pesticide inputs to watercourses are most likely to occur due to direct application
or when rainfall causes surface run‐off or leaching shortly after application. Mitigation
measures to reduce pesticide inputs therefore fall into three main categories:
Best practice advice and education. Encouraging measures to prevent direct
application or point‐source loss of pesticides to a watercourse or drainage system.
Land management and soil management advice. Soil management measures to
prevent rapid run‐off or leaching which ensure that pesticides are taken up by target
species or broken down in the soil rather than being available to cause pollution.
Landuse change and the improvement of farm infrastructure. Mitigation measures
(e.g. buffer strip and riparian wetlands) designed to intercept surface run‐off and
ensure pesticides are broken down before reaching the watercourse.
Pesticide best practice advice & education
Many pesticide contaminations occur as the result of poor practices undertaken during
their transportation, storage, preparation or application. These so called point‐source
inputs of agricultural pesticides mainly occur from hard impermeable surfaces (such as
farmyards, storage facilities or roads), which become contaminated during the filling
and cleaning of sprayers, improper disposal of un‐used mix, leaks from faulty
equipment, incorrect storage of canisters and washing of equipment.
Once present on these surfaces pesticides are then available to be washed into an
adjacent watercourse or to enter the sewerage system, which then transports them to
the sewage treatment works and on into the aquatic environment via the works
discharge. Direct contamination of the aquatic environment can also occur as the result
of spray drift or when pesticide application is inaccurate and occurs outside the confines
of the target field.
Standards for the use and management of pesticides in the UK are set out by BASIS and
the Health and Safety Executive and, in 2001, the farming and crop protection industry
established the Voluntary Initiative to promote best practice in the use and
management of pesticides and to minimise their environmental impacts.
The Voluntary Initiative The Voluntary Initiative (VI) began in April 2001. It is a UK‐wide package of measures,
agreed with Government, designed to reduce the environmental impact of the use of
pesticides in agriculture, horticulture and amenity situations. Initially a list of 27
proposals, the programme finally included over 40 different projects covering
research, training, communication and stewardship.
CASE STUDY
The combined cost of the programme between 2001 and 2006 to the farming
industry, the crop protection industry, the water industry and others was estimated to
be £45‐47m, but during that time they worked to:
Improve awareness among farmers of the potential environmental risks arising
from pesticide use; improve the competence of advisors and improve field
practices of spray operators and optimise the performance of their machines.
Engage the farming unions and establishment of Crop Protection Management
Plans (CPMPs) as a self‐audited means of assessing and planning the
environmental aspects of crop protection activities across the whole farm.
Establish a low‐cost sprayer testing scheme (NSTS) with a nationwide network of
294 testing centres and 465 certificated testers.
Establish the National Register of Spray Operators (NRoSO), through which spray
operators can demonstrate a commitment to best practice in pesticide handling
and application.
Create a series of Environmental Information Sheets as an aid to risk management
for all products sold by members of the Crop Protection Association.
There are a number of comprehensive
guides on good/best practices to be
undertaken when using pesticides,
including the Code of Practice for Using
Plant Protection Products (below).
PESTICID
ES
42
Perhaps the simplest method for the reduction of point‐source pesticide pollution is to
reduce the number of sprayer filling and cleaning actions undertaken by encouraging
farmers to share the use of spraying equipment. In addition, numerous studies have
found that the adoption of good or best practices when using pesticides can ensure that
the risk of environmental contamination is minimised (Kreuger and Nilsson, 2001).
The best management practices shown to be effective include filling and cleaning
sprayers only on the field or on a biobed (Felgentreu and Bischoff, 2006; Vischetti et al.,
2004), careful handling and storage of pesticides and safer storage of empty containers
(Higginbotham, 2001), applying tank mix and container leftovers in dilute form to the
field (Jaeken and Debaer, 2005), and no application of pesticides on the farmyard.
Overall, stewardship initiatives and application of best management practices have
been shown to achieve a reduction in the total river load of 40–95% in a number of
catchment studies (Reichenberger et al., 2007; Kreuger and Nilsson, 2001; Maillet‐
Mezeray et al., 2004). However, in most catchment studies, it was also found that
continued effort is essential to ensure continued prevention.
Another powerful method for the collection and disposal of pesticide‐contaminated
water is the biobed. A biobed consists of a pit or container filled with a mixture of
chopped straw, peat and topsoil that rapidly degrades any pesticide entering the bed
through microbial activity.
CASE STUDY
A pesticide handling area is the site
where the sprayer is filled and is often
also used for sprayer washing, nozzle
calibration, sprayer testing,
maintenance and storage.
A biobed is a mixture of peat free
compost, soil and straw (biomix)
covered with turf that is placed in a
lined pit (see right).
Liquids enter the biomix within the
biobed by gravity drainage or a pump.
Once there they then undergo
bioremediation before being drained
from the biobed. This drained liquid,
which contains minimal pesticide
residues, can be used for land irrigation
or re‐used e.g. for subsequent sprayer
washing.
Mitigating pesticide pollution in Drift Reservoir, Cornwall Over the period 1996‐2010, South West Water’s Drift Water Treatment Works recorded a steady increase in both the
number of pesticide detections per annum and the detected concentration of individual pesticide compounds in both the
raw and final water. During this period there were 54 positive detections for pesticides in the raw water within Drift
Reservoir representing 14 different compounds.
The chart below shows that, in recent years, herbicide detection results for a number of chemical compounds have
shown discrete high, narrow spikes indicative of individual pollution incidents. This increasing risk and frequency of water
quality failure has led South West Water to take a two‐pronged approach at Drift. First, an advanced water treatment
plant was installed at the treatment works, with a capital cost of £4 million and an annual running cost of £30,000, in
order to ensure the final water met Drinking Water Inspectorate standards.
Concurrently, funding of £100,000 was
invested in a programme of landowner
engagement, agricultural training, and
farm intervention work upstream of
the reservoir, to address these rising
chemical detections at source. These
interventions are being delivered in the
catchment through Cornwall Wildlife
Trust’s Wild Penwith Project, which is
working in partnership with South
West Water to provide landowners
across the Drift catchment with a
number of advisory, educational and
infrastructure improvement measures. Continued over page...
PESTICID
ES
43
Mitigating pesticide pollution in Drift Reservoir, Cornwall...continued….
Cornwall Wildlife Trust’s Wild Penwith project is working in partnership with South West Water to provide landowners
across the Drift catchment with:
One‐to‐one farm advisory visits, including an assessment of current farm practices, and provision of water protection
best practice;
Free agricultural training events, such as weed management;
A capital‐grant award, funding, for example, improved pesticide handling and storage areas.
In February 2013, Wild Penwith ran a weed management
training day on a dairy farm adjacent to Drift Reservoir.
Following presentations on the cultural, mechanical and
chemical control of weeds, local farmers visited the water
treatment works at Drift to learn more about the
complexities of drinking water treatment.
Peter James, who farms at Little Sellan adjacent to Drift
Reservoir said, “As a farmer, I am very pleased that South
West Water is taking this proactive approach in our river
catchment. We are now more aware of both the water
companies business, and how important our activities on the
farm are to the drinking water treatment process. I believe
working in partnership in this way will be of benefit to
everyone.”
These farm activities are supported by a comprehensive
programme of water chemistry sampling (monitoring
herbicides, insecticides and fungicides) on the reservoir’s two
feeder streams. Water samples are regularly collected with
the consent and co‐operation of each landowner involved.
Follow‐up samples can be taken from a wider network of
additional farms as required. Using this system, the source of
any in‐reservoir or in‐river pesticide detection can be traced
back to individual farm holdings and advice and guidance
given to mitigate the problem.
Land managers are then made aware of the drinking water issues, and offered one‐to‐one water protection best practice
advice and other farm interventions from the Wild Penwith team as appropriate. In addition to this chemical monitoring
programme, biological monitoring has also been undertaken in the catchment, including the assessment of macro‐
invertebrates, macrophytes (large aquatic plants) and diatoms (benthic algae).
Minimising the levels of pesticides found in the raw
water could result in South West Water savings on
treatment plant operating costs. Wider environmental
gains include improved wetland and stream habitat
quality, and associated enhanced biodiversity.
This is a fantastic example of South West Water’s
‘Upstream Thinking’ project working to deliver
improved water quality in a small reservoir catchment.
Through the wider Wild Penwith Living Landscape
project, Cornwall Wildlife Trust staff gained the respect
and trust of local farmers, which enables them to tackle
these important drinking water quality issues together.
PESTICID
ES
Further info: www.cornwallwildlifetrust/wildpenwith
44
Land management & soil advice
It has been widely demonstrated that any improvements in soil or land management,
such as implementation of conservation tillage techniques, that reduce the risk of run‐
off and soil erosion are also likely to reduce the risk of a pesticide being mobilised
following its application to the land. In addition, the incorporation of organic material
into the soil has also been shown to increase the sorption of some pesticides; reducing
their mobility and the likelihood that they will be lost through leaching.
Interestingly, several studies have shown that the presence of sub‐surface land drainage
also reduces the loss of pesticides through surface run‐off. This finding is supported by
hose of a study of autumn‐applied pesticides on clay loam soils in north east England
where losses from an un‐drained plot were found to be up to 4 times larger than from a
mole‐drained plot (Brown et al., 1995).
In contrast to these findings, however, it is also important to note that there is
considerable evidence that over efficient drainage may also generate significant loss of
pesticides through leaching and drain flow. The risk factors that lead to pesticide loss
through leaching and drainage are poorly understood, but it seems that active
ingredient mobility, application rate, soil type and rainfall may all contribute to the
generation of pollution via this route.
Where pesticide loss via drainage is considered a threat, the use of collection ponds or
wetlands at the outflow are just two measures that could work to mitigate the risk that
a receiving watercourse will be contaminated.
Landuse change & the improvement of farm infrastructure
Perhaps the most studied interventions for the mitigation of diffuse pesticide pollution
are buffer strips around fields (conservation headlands), riparian buffer strips and
constructed wetlands.
These features not only reduce the risk of spray drift contaminating adjacent habitats
and watercourses, but they also act to disconnect pesticide pollution pathways by
promoting the infiltration of run‐off waters carrying them into aquatic environments.
CASE STUDY Buffer Strips for pesticide pollution mitigation As we have described for nutrient and sediment pollution, the efficacy of buffer strips in reducing pesticide losses to
watercourses has also been the subject of a significant body of research (mainly at plot‐ or field‐scale). The findings of this
research, summarised below, indicate that buffer strips can be highly effective in mitigation of pesticide pollution.
In one of the most comprehensive reviews undertaken on the effectiveness of buffer strips in the mitigation of pesticide
pollution, Reichenberger et al. (2009) summarised the findings of 14 publications that between them assessed the
performance of 277 different buffer strips. The pesticide load reductions for active ingredients in solution (below left, 63
data points) and bound to sediment (below right; 214 data points) are summarised below.
Overall, buffer strips of all widths were found to be effective in the mitigation of pesticide loss from fields and were
especially effective when they were vegetated and when run‐off flow was slowed sufficiently to enable water infiltration.
PESTICID
ES
Riparian buffer strips and ‘conservation
headlands’ can reduce pesticide
damage to adjacent natural habitats.
45
MICROBES & PARASITES
MICROBES & PARASITES
46
MICROBES & PARASITES Two principal bacterial groups, coliforms and faecal streptococci, are used as indicators
of possible sewage contamination in water because they are commonly found in human
and animal faeces. Although these bacteria, which are often referred to as faecal
indicator organisms (FIOs), are not typically harmful themselves, they do indicate the
possible presence of pathogenic (disease‐causing) bacteria, viruses, and protozoans
that also live in human and animal digestive systems.
Another group of microbial pollutants derived from human and animal faecal material
which pose a significant risk to human health, either when people come into contact
with the river water or when contaminated water is abstracted for drinking water
treatment, are parasitic protozoa in the genus Cryptosporidium.
Cryptosporidium is transmitted through the environment as hardy spores (oocysts) that,
once ingested, hatch in the small intestine and result in an infection of intestinal
epithelial tissue. The resulting condition, Cryptosporidiosis, is typically an acute short‐
term diarrheal disease but it can become severe and chronic in children and in other
vulnerable or immuno‐compromised individuals. In humans, Cryptosporidium can
persist in the lower intestine for up to five weeks; from where it continues to shed
oocysts into the environment.
Sources of microbial contamination The most commonly tested faecal bacteria indicators are total coliforms, faecal
coliforms, and faecal streptococci. Total coliforms are a group of bacteria that are
widespread in nature and which occur in many materials including human faeces, animal
manure, soil, and submerged wood. The usefulness of total coliforms as an indicator of
faecal contamination therefore depends on the extent to which the bacteria species
found are faecal and human in origin.
For recreational waters, total coliforms are no longer recommended as an indicator, but
for drinking water, total coliforms are still the standard test because their presence
indicates contamination of a water supply by an outside source.
Faecal coliforms are a subset of the total coliform bacteria and are more specifically
faecal in origin. Faecal streptococci also occur in the digestive systems of humans and
other warm‐blooded animals. In the past, the ratio between the level of faecal
streptococci and faecal coliforms was used to determine whether bacterial
contamination was of human or nonhuman origin and, while no longer recommended
as a reliable test, this method can still give an indication of the potential source.
There are three principle mechanisms via which faecal material, parasites and faeces‐
derived substances (e.g. ammonia) make their way into a watercourse. These include:
Direct ‘voiding’ into the water by livestock in the river.
Wash‐off and leaching of manure or slurry on the land surface or accumulated on
yards or tracks.
From consented or un‐consented discharges of untreated human sewage.
Cryptosporidium oocysts under a fluorescence microscope.
Bacteria Escherichia coli.
MICROBES & PARASITES
47
When considering microbial contamination is it important to examine the contribution
that these different potential sources make to the load in the water column in any
particular location.
Analysis of data from 205 river and stream sampling points spread widely across
mainland UK has shown that microbial load is typically correlated with high flow rather
than low flow condition and that urban and grassland landscapes make the most
significant contribution to the load (Kay et al., 2009).
Further studies have also shown that faecal indicator organism (FIO) loads in
catchments with high proportions of improved grassland were shown to be as high as
from urbanised catchments and in many rural catchments ≥40% of FIO may be derived
from agricultural sources (land surface and farmyard infrastructure).
This strong correlation between high flow and contamination levels has also been
shown to be the case for cryptosporidium and outbreaks of cryptosporidiosis are
strongly linked to an animal to human transmission pathway following periods of heavy
precipitation (Lake et al., 2005).
It is assumed that the remaining load at times of high flow is derived from point sources
such as sewerage treatment works, misconnections in the sewerage system and
combined sewer overflows (which discharge when sewage treatment works reach their
maximum treatment capacity).
Interestingly, in contrast to these findings of Kay et al, a detailed study of the River
Ribble catchment undertaken in 2002 found that over 90% of the total FIO load
entering the Ribble Estuary was discharged by sewage related sources during high flow
events.
At times of low flow the principal sources of FIOs has been shown to be from point
sources, such as sewage treatment works, septic tanks and misconnections in the
sewerage system.
Impacts of microbial contamination On the health of aquatic ecosystems
When animal and human faecal material and the microbes it contains, enter a river
system they can exert severe negative impacts on the ecological health of the
ecosystems locally and further down the catchment in a number of ways.
First, the elevated levels of turbidity reduce the levels of light penetrating the water
column and this can affect the plant communities present in the system. This can be
particularly problematic in the deeper and ecologically sensitive waters of the estuaries
and coastal regions at the bottom of a river catchment.
More significantly, however, is the effect that the metabolic activity of aerobic bacteria
decomposing organic waste has on the levels of dissolved oxygen in the water column.
Where the levels of organic material and hence the microbial activity in the water are
high the Biological Oxygen Demand (BOD) in the water will be elevated and the levels
of dissolved oxygen available for other plants and animals living in the water will fall.
Eventually this depletion of dissolved oxygen will become so severe that the ecological
health of the river ecosystem will be degraded as fish and invertebrate communities
begin to suffer.
Unrestricted access of livestock to a watercourse
eutrophication&hypoxia
MICROBES & PARASITES
48
On the provision of drinking water, recreation & fisheries
The total level of microbial contamination in water and the level of different faeces‐
derived bacteria are both used as indicators of the potential pathological risk posed by
that water. In addition, faecal material may also contain other pathogenic organisms,
such as Cryptosporidium, which cause gastrointestinal infections after ingestion or
others which cause infections of the respiratory tract, ears, eyes, nasal cavity and skin.
When animal and human faecal material enter a river system they can therefore pose a
significant threat to the health of people who rely on that water for drinking water,
recreation or the sustenance of fisheries and shell fisheries in downstream regions of the
river catchment.
As a result of this threat, significant steps must be taken at the water treatment works
to remove microbial contaminants from drinking water. There are a number of methods
for the disinfection and filtration of drinking water and all must be undertaken with
increased intensity if the microbial load in the abstracted raw water increases
significantly at certain times.
The EC Drinking Water Directive also requires that drinking water should not contain
any micro‐organism or parasite (such as Cryptosporidium) at a concentration that would
constitute a potential danger to human health. Cryptosporidium is particularly adept at
breaking through the standard suite of treatment processes undertaken at many works
(such as sand filtration and chlorination) and the Drinking Water Inspectorate now
requires water companies to implement raw water monitoring, to undertake
comprehensive risk assessments and to design and continuously operate adequate
treatment and disinfection for cryptosporidium.
In addition to these increased demands for disinfection, it is also important to note that
the presence of elevated levels of faecal material also make a significant contribution to
the turbidity and suspended solid load in the raw water. As already described previously
the levels of turbidity in the raw water are used to calibrate the water treatment process
and, when elevated, will increase the costs of coagulation and sludge management
processes undertaken at the drinking water treatment works.
CASE STUDY Bathing water standards in the UK The European Union began work to regulate the provision of clean and healthy bathing
waters in the 1970s and in 2006 the EC Bathing Water Directive was passed to preserve,
protect and improve the quality of the environment and to protect human health.
The monitoring and improvement of water quality at bathing waters that are at risk of
failing the standards set out in the European Bathing Water Directive are the
responsibility of the Environment Agency. They take weekly water samples from over
500 coastal and inland bathing waters in England and Wales during the bathing season
(May to September).
These samples are tested for contamination with bacteria such as Escherichia coli and intestinal enterococci which,
although not directly harmful in themselves, do indicate a decrease in water quality and give an indication of when
pathogenic microbes may be present in the water.
Prior to 2012, water samples taken at bathing waters were analysed
for Total coliforms, Faecal coliforms and Faecal streptococci; however
this has changed in preparation for the revised bathing water
directive, which sets more stringent water quality targets to achieve
by 2015.
In addition to improving water quality at bathing waters the revised
Directive also places much greater emphasis on managing beaches
and providing information. From 2016, Bathing Water Controllers (any
local authorities, water companies and businesses in control of the
land immediately next to bathing waters where people swim) will also
have to provide information to the public about the quality of their
bathing water and advise people if there has been a pollution incident.
Cryptosporidiosis (the Cryptosporidium pathogenic lifecycle) (top) and a micrograph showing cryptosporidium oocysts alongside Giardia lamblia (another parasite) (bottom).
MICROBES & PARASITES
49
Microbial mitigation measures & their efficacy There are numerous highly effective methods designed to reduce the microbial
contamination of watercourses, estuaries and coastal waters. Which of these measures
is required depends entirely on the sources from which the contamination is derived in a
particular catchment.
If a domestic sewage treatment works or septic systems are found to be discharging
significant levels of faecal material and bacteria into a watercourse then the addition of
further ‘tertiary’ treatment processes, such as disinfection may be required to remove
high levels of bacteria from the effluent discharged.
Where the contamination is the result of untreated effluent discharges from combined
sewer overflows (CSOs) or poorly functioning (misconnected) sewerage infrastructure,
only increased sewage storage or treatment capacity at the works or investment in
infrastructural improvements may be capable of reducing these impacts. This type of
remedial work can have significant cost implications for the individuals or the water
company responsible for the infrastructure (see below).
Mitigation measures for reducing microbial contamination in watercourses derived from
diffuse agricultural sources include :
Reduction in livestock stocking rate Creation of riparian buffer strips Creation of wetlands or reedbeds
Exclusion of livestock from watercourse and provision of alternative drinking
sources for livestock
Increased slurry storage capacity Minimise the volume of dirty water produced (clean and dirty water separation)
Increased use of solid manure
Do not apply manure or slurry to fields at high‐risk times
All of these measures act to either reduce the total levels of faeces‐contaminated
material available for mobilisation on a farm, change the way that manure is stored to
reduce its likelihood of mobilisation to a watercourse, prevent direct ‘voiding’ into water
courses, or disconnect the pathways via which faecal material is washed into
watercourses.
CASE STUDY The Clean Sweep Project Before South West Water (SWW) was privatised in 1989, little had been done to protect the coastal bathing waters of the
South West, and the region’s reputation was suffering as a result. In 1990, the UK Government adopted higher water
quality standards imposed by the European Union, making the need for change even more critical. Starting in 1992,
SWW’s response to this was Clean Sweep – the largest environmental programme of its kind in Europe. MICROBES & PARASITES
The Westcountry Rivers Trust farm
measure fact‐sheets can be found at—
http://tinyurl.com/kqpyctv.
Over an 18 year period, over £1.5 billion was invested in improving the water
quality of the South West’s bathing waters. As a result of Clean Sweep, 250
crude sewage outfalls were closed and 140 individual mitigation projects
were completed.
The success of the programme was demonstrated in 2006, when for the first
time all 144 bathing sites in SWW’s region achieved 100% compliance with
the EU mandatory standard. This was a massive improvement when
compared to the situation in 1996, when only 51% of beaches complied.
The 2007 Good Beach Guide, published by the Marine Conservation Society
(MCS), stated that ‘the South West is the top performing region in this year’s
guide’ and recommended over 80% of beaches in SWW’s operating region.
Since Clean Sweep ended in 2010, SWW have continued to develop their
strategic plans for the delivery of environmental improvements and
sustainability. Most recently, they have been working in partnership to
locate and remediate mis‐connections in Torbay, Bude and Plymouth.
More information: www.beachlive.co.uk
50
CASE STUDY Torbay Bathing Water Improvement Project Initiated and funded by South West Water in 2010 and delivered by the Environment
Agency working in partnership with Torbay Council, the Torbay Bathing Water
Improvement Project aims to reduce the levels of pollution in Torbay's streams and
improve bathing water quality. In particular, the project has focused on locating and
remediating drainage and sewage mis‐connections that are leading to pollution.
The project has focused on five resort beaches, key to the local economy, which are
at risk of failing to meet the new standards set out by the Revised EC Water Directive
from 2015. These beaches were Torre Abbey, Hollicombe, Preston, Paignton and
Goodrington.
MICROBES & PARASITES
Mis‐connections
Over one hundred misconnected properties have been identified through the
project, which have all been discharging foul or dirty water into streams through
surface water systems. 80% of the mis‐connections found have now been
resolved and connected to foul sewer.
The majority of misconnections have been residential with household extensions
and washing machines moved into garages being the most common culprits.
Commercial inputs have also been an issue; including a hotel, car wash, two
cafes, a supermarket, doctors surgery, offices and a factory. Other issues such as
dog and bird fouling, waste from boats, sewerage infrastructure and council
operations are all being looked at as part of the project.
It is estimated that the project has so far stopped approximately 5,000 cubic
metres (per annum) of polluting water entering Torbay streams and bathing
waters.
Examples of the mis‐connections found in Torbay that discharge either directly into a
watercourse (top left) or into a surface water sewer (bottom left).
Significant findings
In one Torquay hotel a blockage in a main foul sewer line was
leading to considerable pollution of the Cockington stream.
Working with the hotel owners and South West Water, the
issue was identified and resolved with a considerable
improvement in water quality in the stream, as shown in the
chart (right).
In other locations six houses were found discharging into the
Torre Abbey and Cockington Streams and a blocked private
manhole was allowing foul water from two flats to discharge
to the sea via an un‐sampled surface water system.
0
20
40
60
80
100
120
Ce
ll c
ou
nt
(00
0's
/10
0m
l)
FaecalColiforms/100ml
Problem fixed
Working with Environment Agency contractors (ONSPOT), the project also discovered that a large factory had been
wrongly connected and was discharging most of its waste waters into the Torre Abbey Stream via a surface water
system. The factory accommodates some 100 staff and is thought to have been polluting the stream for over ten years.
Next Steps
Such was success of the Torbay project that additional
funding has now been secured and the focus will be
extended to include two further catchments in Torbay; the
Torre Abbey Stream and the Kirkham Stream, which both
remain affected by as yet unknown pollution sources.
In addition, the project will also produce an engagement
plan, designed to advise and educate both the public and
tradesmen, to reduce the likelihood of further mis‐
connections in the future. There is also be a drive underway
to share best practice from the project with other local
authorities to help improve other ‘at risk’ bathing waters in
locations such as Bude (north Cornwall) and Plymouth. Paignton Beach
51
CASE STUDY Measures to mitigate diffuse microbial pollution risk Methods to reduce pathogen transfers to watercourses essentially tackle aspects of source, mobilisation or delivery to
the watercourse.
Perhaps the most effective measures designed to reduce the sources of faecal and organic material are those that
improve the management of manure by increasing slurry storage capacity, reduce inputs of rainwater to manure stores
or switch to a confined composting system of storage.
By reducing the volume of contaminated material produced these measures enable farmers to restrict their application of
manure to the land to dry periods, when the risk of wash‐off is least. They also allow farmers to keep their yards free of
contaminated material and reduce the levels of live bacteria in the manure before it is spread.
Another major source of microbial contaminants is direct ‘voiding’ by livestock while in or immediately adjacent to a
watercourse.
In a 7 year study of a dairy farm, Line (2003) demonstrated that livestock exclusion resulted in a 66% reduction in the
levels of faecal coliforms in the watercourse below the farm and there is considerable additional evidence that exclusion
of livestock from water courses and the provision of alternative drinking points can significantly reduce contributions
from this source (see table below).
The final type of intervention that can mitigate delivery of microbial contaminants to watercourse are riparian buffer
strips and constructed wetlands that act to disconnect pollution pathways carrying material washed off the land surface.
The ability of these measures to disconnect run‐off has already been described in detail, but there have been a number of
studies that have investigated their ability to reduce bacterial loads at field and plot scale (summarised in table below).
Reference Location Buffer Width (m) Soil Texture Slope (%) Efficacy (% FIO reduction)
Atwill et al. (2002) USA 3.1 Sandy loam 5‐20 99.9
Lim et al. (1998) USA 6.1 Silt loam 3 100
12.2 100
18.3 100
Muenz et al.(2006) USA 25 Sandy clay loam 16.5 53
Tate et al. (2004) USA 1.1 Sandy loam 5‐20 75‐88
MICROBES & PARASITES
52
COLOUR , TASTE & ODOUR COMPOUNDS
COLO
UR, T
ASTE & O
DOUR
53
COLOUR, TASTE & ODOUR There are a number of factors that may result in water exhibiting aberrations in its
colour, taste or odour and which negatively affect its quality and/or safety. On most
occasions when colour, taste or odour problems do occur the impacts are primarily on
the aesthetic quality of the water and therefore, with the resulting increase in the risk of
water customer dissatisfaction, there is an increase in the intensity and cost of
treatment required to remove it from the water.
In addition, however, there are occasions when soluble colour, taste and odour causing
compounds occur which can pose a serious threat to the condition of water supply
infrastructure and, in some circumstances, to human or ecosystem health.
Perhaps the best examples of this are metal ions which, in addition to causing aesthetic
problems in the water, can have significant impacts on the ecological condition of rivers
and streams.
Sources of colour, taste & odour compounds There are two main groups of soluble species that can cause colour, taste and odour
problems, namely metal ions and soluble organic compounds (a component of dissolved
organic carbon—DOC).
These compounds (described in the table below) are often derived from natural sources
in the environment, such as the underlying geology, or through the natural breakdown
of organic material. However, in certain circumstances their levels can be artificially
elevated as an indirect result of human activities or as a direct bi‐product of the water
treatment process itself.
Soluble species Sources Impacts
Metal ions
‐ Aluminium Natural release from underlying geology and bi‐product of water treatment coagulation process.
Can cause discolouration of water. Evidence suggests there may be some health and ecological impacts of chronic expo‐sure.
‐ Copper Naturally occurring, but can be mobilised as a result of human activity.
Can cause metallic taste and can lead to the discolouration of supply infrastructure. Evidence suggests there may be some health and ecological impacts of chronic exposure.
‐ Iron Naturally occurring, but can be mobilised as a result of human activity.
Can cause metallic taste and can lead to the red/brown discol‐ouration of supply infrastructure. Evidence suggests there may be some ecological impacts of chronic exposure.
‐ Manganese Naturally occurring, but can be mobilised as a result of human activity.
Can cause metallic taste and can lead to the black/brown discol‐ouration of supply infrastructure. Evidence suggests there may be some ecological impacts of chronic exposure.
‐ Zinc Naturally occurring, but can be mobilised as a result of human activity.
Can cause metallic taste. Evidence suggests there may be some ecological impacts of chronic exposure.
Organic compounds
‐ Geosmin Produced by aerobically growing aquatic algae and microbes. Also produced by fila‐mentous actinomycete bacteria in soil.
Cause earthy taste and odour problems in drinking water that are very hard to remove without activated carbon filtration.
‐ Methyl‐Isoborneol (MIB)
Produced by aerobically growing aquatic algae and microbes. Also produced by fila‐mentous actinomycete bacteria in soil.
Cause earthy taste and odour problems in drinking water that are very hard to remove without activated carbon filtration.
‐ Trihalomethanes (THMs)
Produced as a bi‐product of chlorine‐disinfection of drinking water containing organic material.
Growing evidence that THMs are carcinogenic. Very hard to remove without activated carbon filtration.
‐ Humic substances Produced by biodegradation of dead organic matter (e.g. peat, woodland, algae etc.)
Discolouration of water (yellow) that is very hard to remove without activated carbon filtration.
Can reduce efficiency of other treatment processes.
Ferric (iron‐based) compounds leach in
to a stream (top) and heavily coloured
water in the upper reaches of the River
Dart (bottom).
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The drainage and over‐exploitation of peat bogs and other upland habitats with peat‐
based soils, is known to enhance the loss of dissolved organic carbon (DOC) to
watercourses and to significantly increase water discolouration through contamination
with colour‐causing organic compounds such as humic acids (Worrall et al., 2007;
Wallage et al., 2006; Armstrong et al., 2010).
In addition to the colour‐causing compounds derived from peat and peaty soils, it has
also been shown that leaf litter is another important source of natural dissolved organic
carbon (DOC) in forested catchments (Hongve, 1999). Interestingly, rainwater
percolating through fresh litter is known to obtain higher concentrations of DOC and
colour than is derived from older forest floor material and organic soils. Furthermore,
deciduous leaf litter has been shown to impart high DOC concentrations in the autumn,
while coniferous litter and organic soils release DOC more evenly.
In their Advisory Note 19 on, ‘Rivers and their catchments: potentially damaging physical
impacts of commercial forestry’, Scottish Natural Heritage warn that ploughing and
restructuring of drainage patterns may occur as part of ground preparation work prior to
commercial tree planting. They also describe how drainage ditches are often aligned at
right angles to the slope, which causes peak run‐off flows to arrive more rapidly in the
receiving watercourse.
The effect of this drainage, coupled with the increased availability of colour‐causing
compounds in the soil due to the decomposition of leaf litter and the degradation of the
peat, could be the cause of the deteriorations in water quality now commonly observed
in many watercourses and reservoirs in upland catchments.
Other organic taste and odour‐causing compounds that are generated in soil and
decomposing organic material are geosmin and 2‐Methylisoborneol (MIB). These
compounds are also generated within many lakes and reservoirs as algal and
macrophyte growth dies back at the ends of the growing season (see right).
Many colour‐causing metals, such as iron, zinc and manganese, are released naturally
from land with underlying geology where they occur and they can therefore be leached
at quite significant levels into watercourses. This leaching can be significantly enhanced
where geological disturbance has been caused through human activities such as mining.
It has also been shown that upland peaty soils, with their inherently acidic nature,
particularly favour the mobilisation of manganese and, furthermore, conifer
afforestation has also been demonstrated to increase manganese levels in surface
waters immediately following felling.
In addition to being catchment‐derived, manganese flux in lakes or reservoirs can also
occur as a result of seasonal stratification occurring in eutrophic waterbodies.
Manganese ions are mobilised into solution from lake‐bed sediment when an hypoxic/
anoxic layer of water forms above it and, once solubilised, are then distributed
throughout the waterbody when re‐mixing of the water column occurs in the autumn.
This phenomenon results in large spikes of these manganese ions in solution at various
times (see right) and can then present a significant challenge to the ecological health of
the aquatic environment and to the water treatment process.
Humic acids (top) are known to be
released from degraded peatland
(bottom).
Data showing large seasonal
accumulations of geosmin (top) and
manganese (bottom) in a small
reservoir in the South West of England.
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Impacts of colour, taste & odour contaminants On the health of aquatic ecosystems
The ecological impacts of taste and odour‐causing organic compounds (dissolved
organic carbon) remain poorly understood, but their ecotoxicology has been
investigated in a number of experimental systems and few toxic effects have been
demonstrated at the concentrations typically found in contaminated waterbodies.
In contrast, several metal ions have been shown to have an impact on the ecological
health of aquatic ecosystems. As a result of these findings chromium, copper, iron and
zinc are all listed as ‘specific pollutants’ and have standards monitored as part of the
ecological condition assessments undertaken for the Water Framework Directive
classification process. The inclusion of manganese as a specific pollutant in the next
cycle of Water Framework Directive classification is currently being considered.
On the provision of drinking water
The levels of colour, taste and odour compounds in raw water have a direct impact on
the dose of coagulant required in its treatment at the water treatment works (indeed
many works dose coagulant according to turbidity and colour levels in the raw water). If
these compounds are not removed they can impinge on the aesthetic quality of the final
drinking water and cause the discolouration of drinking water infrastructure (for
example manganese in treated water can stain sanitary ware).
In addition, soluble organic compounds, such as humic substances and geosmin, can
cause further problems at the water treatment works as they can be converted into
disinfection by‐products (DBPs) when chlorine is used during water treatment process
(Krasner et al., 1989).
These DBPs can take the form of trihalomethanes (THMs), haloacetic acids (HAAs) and
a host of other halogenated DBPs, many of which have been shown to cause cancer in
laboratory animals and which can pass though the standard treatment processes
undertaken at many works (Singer, 1999; Rodriguez et al., 2000).
CASE STUDY Colour in Fernworthy Reservoir, Devon Increasing levels of colour in the water from Fernworthy Reservoir on the
eastern edge of Dartmoor represent a significant challenge for South West
Water at the Tottiford water treatment works. The deterioration in the water
quality in the reservoir was so severe that the Bovey Cross water works had to
close because the treatment process could not cope with the raw water. The
colour‐causing compounds in Fernworthy Reservoir are primarily humic
substances derived from the degradation of organic material in the peat‐lands
and forested areas that surround this moorland reservoir (see land cover map;
right). It is clear that water percolating through peat or forest leaf‐litter across
the catchment is mobilising and transporting these colour‐causing substances
into the watercourses and drains that feed into the reservoir. This effect is
being significantly enhanced in areas where the peat has been damaged or
degraded through drainage or intensive exploitation.
Humic colour‐causing compounds in raw water can only be
removed through the coagulation process at the works and
so, if the colour levels in the water increase, it can have
significant cost implications for the water company as the
coagulant dose must also be increased. These organic
compounds cause further problems at the works as they
can be converted into disinfection by‐products (DBPs)
when chlorine is used during water treatment.
Examination of South West Water data (left) shows that
the level of colour in Fernworthy Reservoir cycles
throughout the year, but also that the average level has
significantly increased since 2004.
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Colour, taste & odour mitigation measures Ultimately, the only way to completely remove the soluble organic compounds and
metal ions that cause colour, taste and odour problems in raw water intended for
treatment and supply as drinking water is to implement technological solutions, such as
activated carbon filters, at the treatment works.
Whether they are derived from point or diffuse sources in the catchment, mitigation of
their loss into the aquatic environment at their source is far more challenging to achieve.
Having said this, however, there is increasing evidence that re‐wetting of peat‐lands and
mires that have been degraded by drainage or over‐exploitation of peat can reduce the
leaching of Dissolved Organic Carbon (DOC) compounds that cause colour, taste and
odour contamination of raw water.
Specifically, several studies have demonstrated that the re‐wetting of mires and peat‐
lands, through the practice of drain‐blocking, can significantly reduce the loss of DOC
and colour‐causing compounds from land of this type (Wallage et al., 2006; Armstrong
et al., 2010).
In their extensive UK‐wide survey of blocked and unblocked drains across 32 study sites
and through the intensive monitoring of a peat drain system that has been blocked for 7
years, Armstrong et al. (2010) demonstrated that dissolved organic carbon
concentrations and water discolouration were significantly (~28%) lower in blocked
drains compared to unblocked drains.
Overall, whether the source of contamination is from mine works, forestry or peatland
soils it is clear that it is the management of drainage and the hydrological regime of the
land which may achieve the greatest effect in mitigating the impacts of colour, taste and
odour‐causing contaminants.
CASE STUDY The Sustainable Catchment Management Programme (SCaMP) The Sustainable Catchment Management Programme (SCaMP), has been developed by
United Utilities in association with the Royal Society for the Protection of Birds (RSPB).
The programme aims to apply an integrated approach to catchment management across
all of the 56,385 hectares of land United Utilities own in the North West, which they hold to
protect the quality of water entering the reservoirs.
Through the delivery of SCaMP United Utilities is recognised within the UK water industry
as being at the forefront of water company‐funded catchment management scheme that
are aiming to secure multiple benefits at a landscape scale.
Peatland restoration being undertaken
by the Exmoor Mires Project (top) and
stakeholders visit a restored mires site
(bottom)
The aims of the SCaMP initiative are to help; (1) protect and
improve water quality, (2) reduce the rate of increase in raw
water colour which will reduce future revenue costs, (3)
reduce or delay the need for future capital investment for
additional water treatment, (4) deliver government targets
for SSSIs, (5) ensure a sustainable future for the company's
agricultural tenants, (6) enhance and protect the natural
environment, and (7) help these moorland habitats to
become more resilient to long term climate change.
Monitoring at a sub‐catchment level in SCaMP delivery areas indicates that there is a statistical ‘tipping point’ two years
after intervention. This has been found in similar short term studies and it is thought that re‐wetting dried peat initially
releases more carbon in the form of colour before the natural biochemical processes begin to re‐establish. At present
several sub‐catchments are indicating a slight, but statistically significant, decrease in colour over time and one site
has seen a significant 45% reduction in stream flow turbidity since restoration.
For more information visit—corporate.unitedutilities.com/scamp‐index.aspx
Over the last 30 years there has been a substantial increase in the levels of colour in the water sources prior to treatment
from many upland catchments (see example below). The removal of colour requires additional process plant, chemicals,
power and waste handling to meet increasingly demanding drinking water quality standards. To address this, expensive
capital solutions are often required at a water works which result in significant increases in annual operational costs.
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ASSESSING ASSESSING IMPROVEMENTS IN IMPROVEMENTS IN WATER QUALITYWATER QUALITY
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The principal, over‐arching aim of any catchment management work is to improve the
water quality in our freshwater ecosystems and to make a significant contribution to
their attainment of good ecological status in accordance with requirements of the EU
Water Framework Directive. It is therefore vital that sufficient evidence is collected to
provide an objective and robust assessment of the improvements delivered.
Ultimately, we must be able to justify that the money spent and the interventions
delivered across the landscape have delivered significant improvements in water quality
(and have therefore made significant contributions to the delivery of good ecological
status of river catchments) and have generated significant secondary financial,
ecological and social benefits.
To achieve these over‐arching aims, a range of approaches have been developed that
will allow us to assess various outcomes delivered by our catchment management work;
Quantification of intervention delivery. Gathering precise and detailed evidence of
what has been delivered, where and how it was delivered, what it cost and, perhaps
most importantly, what the intended outcome was for each measure.
Monitoring for environmental outcomes. Collection of a comprehensive and robust
set of data and evidence which demonstrates qualitatively and quantitatively
whether real improvements in raw water quality have been achieved. To achieve this
it is vital that this includes robust baseline data that includes temporal (before
intervention) and spatial (no intervention) controls.
Modelling to predict environmental outcomes. Use of the most advanced modelling
techniques which can be used to estimate the improvements in water quality that
have been achieved.
Assessment of secondary outcomes. There are a number of monitoring and
modelling approaches that can be used to assess how a catchment management
programme has enhanced the provision of other ecosystem services across a
catchment and to quantify the economic benefits to those engaged in the process.
ASSESSING IMPROVEMENTS
The DEFRA Demonstration Test Catchments (DTC) As part of a national drive to gather evidence that catchment management can have a significant impact on raw water
quality DEFRA are currently funding a £5 million Demonstration Test Catchment (DTC) Project across three catchments:
the Hampshire Avon, the Wensum and the Eden. The aim of DTC Projects is to evaluate the effectiveness of on‐farm
measures to improve water quality when their delivery is scaled‐up to a real‐life whole sub‐catchment situation. .
The Westcountry Rivers Trust’s current Upstream Thinking Project on the Caudworthy Water, a short (~3.5 km)
tributary of the River Ottery in the Tamar catchment, now represents a satellite study of the Hampshire Avon DTC. The
DTC consortium is undertaking a detailed monitoring programme before and after the a comprehensive farm
investment and advice programme being delivered across the catchment.
CASE STUDY
Two monitoring stations located at the middle and bottom of the catchment have
been recording total nitrogen, nitrate, nitrite, soluble reactive phosphate, total
phosphate, turbidity, suspended sediment concentration, dissolved oxygen,
temperature, pH, ammonium, chlorophyll, effective particle size and discharge.
In addition to this chemical monitoring programme, extensive biological
monitoring has also been undertaken in the catchment, including the assessment
of macro‐invertebrates, benthic algae (diatoms), macrophytes and fish.
The baseline data for Caudworthy Water has been collected over an 18 month
period and Westcountry Rivers Trust have approached all twenty‐four farmers in
the Caudworthy Water sub‐catchment. To date, over £450,000 has been invested
in around £700,000 worth of capital investments with Best Management Practices
ensured through the application of a Restrictive Deed on 19 of these farms.
Following the implementation of the Best Management Practices in 2012‐13, the
effects on water quality will then be monitored over 2013‐15.
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CASE STUDY The Extended Export Coefficient Model (ECM+) The Extended Nutrient Export Coefficient Model (ECM+) has been
developed by the University of East Anglia under the Rural Economy and
Land Use (RELU) Programme and part‐funded by the Westcountry Rivers
Trust. This model has been reviewed by scientific peers and the DEFRA
Water Policy Group and is widely expected to become one of the primary
methods for rural land management planning through stakeholder
participation in the future.
ECM+ has been developed to predict the effects implementation of Best
Management Practices (BMP’s) (Cuttle et al. 2007) will have on sediment,
faecal indicator organisms (FIOs), phosphorus and nitrogen inputs into
watercourses.
Put simply, the model uses export coefficients for different land‐use types to
calculate exports of these pollutants based on the following input data:
Landuse distribution—including urban and various agricultural landuses
such as cereals, maize and grassland.
Livestock numbers—including numbers of cattle, sheep, pigs and poultry.
Population served, treatment levels and locations of Sewage Treatment
Works (STWs)
Population not served by STWs—indicative of septic tank numbers
Road and track density
Rainfall and hydrological data combined with information on in‐stream
processing of pollutants
Location and area of lakes and reservoirs with modelled impact on pollutant
load at outflow
Farming practices: current uptake of Best Management Practices and
effectiveness in reducing pollutant export
What makes the ECM+ model such a powerful tool is that it is constructed with the participation of farmers, water
company representatives and other stakeholders in the catchment and this allows all of the input data to be ‘ground‐
truthed’ before it is added into the model. In addition, the model is calibrated at the sub‐catchment level with real‐world,
in‐stream measurements of pollutant load derived from Environment Agency monitoring data.
Another important component of the ECM+ model is that, once it has been built, it is then possible to develop and run a
number of scenarios with the stakeholders (which can include different blends of both Best Management Practices on
farms and improved sewage treatment measures) and observe their effects on the export of pollutants to the
watercourse.
ECM+ in Action
The River Tamar is a key raw water source for South West Water
and has been the subject of considerable investment in catchment
management interventions through schemes such as Upstream
Thinking and Catchment Sensitive Farming.
The Caudworthy Water sub‐catchment of the River Ottery in the
Tamar catchment is also a satellite study site for the DEFRA
Demonstration Test Catchment (DTC) project on the Hampshire
Avon.
In light of its importance as a drinking water catchment and for the
Water Framework Directive (the Crownhill WTWs catchment is
comprised of 45 WFD waterbodies) the ECM+ model has been built
for the River Tamar catchment above its tidal limit at Gunnislake
through a participatory development process.
Once built, the model has then be used to predict the improvements in water quality that may have been achieved
through the delivery of different catchment management scenarios in different locations.
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This case study summarises the ECM+ predicted export of nitrate and phosphate from the Tamar catchment under four
different management scenarios, involving different levels of implementation of the top 35 (most commonly used) Best
Management Practices. The four scenarios were as follows:
Scenario 1: Baseline (current situation, no additional interventions)
Scenario 2: 100% uptake of top 35 BMPs in the Caudworthy sub‐catchment
Scenario 3: 100% uptake of top 35 BMPs across the whole of the Tamar above Gunnislake Bridge
Scenario 4: 100% uptake of top 35 BMPs across the whole of the Tamar plus 90% nitrogen and phosphate stripping
efficiency at all Sewage Treatment Works.
The model outputs show the predicted average concentration of each pollutant against specific standards. For phosphate, the background
matches the classification used for the EU Water Framework Directive: blue represents ‘high ecological status’; green ‘good ecological status’,
yellow ‘moderate ecological status’, orange ‘poor ecological status’ and red ‘bad ecological status’. For nitrate, the pre‐abstraction standard
for drinking water is defined by the dark blue vertical line on the far right of the nitrogen export graphs below (equating to 11.3 mg/l). The
bright blue line in the centre of the graphs represents a stringent ecological limit used in some water bodies, which translates to 2.5 mg/l.
Scenario 1: Baseline
The outputs from the ECM+ model (right) indicate that the
Caudworthy sub‐catchment under the current ‘business‐as‐
usual’ scenario (Scenario 1) is likely to have an average
phosphorous export load corresponding to moderate/poor
ecological status.
At Gunnislake Bridge the phosphate levels are likely to be
moderate.
Below the Caudworthy outflow and Gunnislake Bridge the
nitrogen levels are likely to be compliant with the drinking
water standard, but exceed the ecological standard in both
locations.
Extended Export Coefficient Model (ECM+)...continued….
Scenario 2: 100% BMP uptake on the Caudworthy
In Scenario 2 (not shown), the model predicts that average water quality in the Caudworthy sub‐catchment will improve
to better than good ecological status for phosphate and will be compliant with the more stringent ecological standard for
nitrogen. The effect of this level of action in the Caudworthy is also passed on to Gunnislake, but the improvements are
masked by the volume of water from the rest of the Tamar catchment.
Scenario 3: 100% BMP uptake on the whole Tamar catchment
In Scenario 3 (left), water quality at the Caudworthy Water
outflow and Gunnislake Bridge both improve significantly with
nitrogen levels at both sample sites predicted to be compliant
with the stringent ecological standard.
However, phosphate levels at Gunnislake Bridge are still only 25%
certain to reach good ecological status.
Scenario 4: Scenario 3 plus 90% N and P stripping at STWs
In Scenario 4, the model predicts a greater than 50% chance
that the water quality at the Caudworthy outflow and
Gunnislake Bridge would both meet water framework
directive standards for phosphorous and that nitrogen levels
would be compliant with stringent ecological standards.
ECM+ predicts significant improvements in water quality as a result of implementation of BMP’s. Importantly, the ECM+
has been used very successfully as a method for rural land management planning through stakeholder participation.
Delivering improvements in water quality through catchment management requires strong partnerships and successful
stakeholder engagement, including private, public and third sector organisations and landowners.
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CASE STUDY Farmscoper on the Hampshire Avon The FARM SCale Optimisation of Pollutant Emission Reductions (FARMSCOPER)
model is a decision support tool that can be used to assess diffuse agricultural
pollutant loads on a farm and quantify the impacts of farm pollution control options
on these pollutants.
FARMSCOPER allows for the creation of unique farming systems, based on
combinations of livestock, cropping and manure management practices. The
pollutant losses and impacts of mitigation can then be assessed for these farming
systems.
The effect of a potential mitigation methods are expressed as a percentage
reduction in the pollutant loss from specific sources, areas or pathways.
The tool utilises a number of existing models including:
Phosphorus and Sediment Yield Characterisation in Catchments (PSYCHIC)
National Environment Agricultural Pollution‐Nitrate (NEAP‐N)
National Ammonia Reduction Strategy Evaluation System (NARSES)
MANure Nitrogen Evaluation Routine (MANNER)
IPPC methodology for methane and nitrous oxide.
The effectiveness of mitigation methods are characterised as a percentage
reduction against the pollutant loss from a set of loss coordinates. The
effectiveness values were based on a number of existing literature reviews, field
data and expert judgement and are assumed to incorporate any efficiencies of
implementation.
The effectiveness values for mitigation methods were allowed to take negative
values, which can represent ‘pollution swapping’, where a reduction in one
pollutant is associated with an increase in another.
The tool also estimates potential consequences of mitigation implementation on
biodiversity, water use and energy use.
The Hampshire Avon Study
The Hampshire Avon is a lowland system situated on the
southern coast of England. It is a predominantly rural
catchment with approximately 75% of land used for
agriculture. Parts of the Avon suffer from ‘chalk stream
malaise’ due to nutrient and sedimentation issues that are
thought to primarily originate from diffuse agricultural
pollution. Over 50% of the waterbodies in the catchment do
not achieve good ecological status under the Water
Framework Directive.
The Hampshire Avon is also one of DEFRA’s Demonstration
Test Catchments. trekker308
Spatial datasets and the Agricultural Census returns for the River Avon in 2009 were used to develop a collection of farm
types characteristic of the Hampshire Avon and reflective of landuse patterns, physical landscape characteristics and
farm management practices in the area.
Of these representative farms, it was estimated that there were 292 cereal farms (representing 51% of the land area),
129 lowland grazing farms (11% of land area), 130 mixed farms (20% of land area), 77 dairy farms (8% of land area) and 52
horticultural farms (less than 1% of land area) in the Avon catchment. The remaining land area comprised small numbers
of general cropping, pig, poultry or ‘other’ representative farm types.
FARMSCOPER was then used to test three different scenarios and estimate sediment, nitrate, phosphorous, ammonia,
methane and nitrous oxide loads or emissions for each representative farm type. The scenarios tested were:
Scenario 1: Baseline pollutant emissions with no mitigation measures
Scenario 2: Current pollutant emissions based on an estimate of the existing level of mitigation measures
implemented
Scenario 3: Maximum reductions through implementation of all measures in the Defra User Guide (Newell et al. 2011)
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FARMCOPER on the Hampshire Avon...continued….
Results
FARMSCOPER predicts baseline pollutant loadings in kg per hectare per year (kg ha‐1 yr‐1) (see table). Under scenario 1,
the baseline levels of pollutant emissions if no mitigation measure were in place, it estimated that cereal farms would
contribute about 55% of nitrate, 38% of phosphorous, 67% of sediment and 50% of nitrous oxide. Mixed farms were
estimated to contribute 48% of ammonia, 40% of methane and about 26% of nitrate, phosphorous and nitrous oxide.
The principal contribution from dairy farms was methane emissions, contributing 32% of total methane. These
predictions were compared with monitored data for pollutant loads in the Avon and were considered acceptable.
Farm Type Nitrate (NO3) Phosphorous Sediment Ammonia (NH3)
Methane (CH4)
Nitrous oxide (N2O)
Cereals 4.0% 6.0% 7.8% 9.0% 0.0% 6.2%
General cropping 3.9% 6.0% 7.8% 9.0% 0.0% 6.1%
Horticulture 4.5% 6.5% 8.9% 9.0% 0.0% 7.7%
Dairy 4.9% 11.6% 4.9% 15.2% 10.4% 7.6%
Lowland grazing 2.4% 10.4% 4.7% 0.3% 0.0% 3.0%
Mixed 3.0% 14.8% 6.3% 4.8% 0.3% 5.4%
Under scenario 3, which is the delivery of the
maximum reductions through implementation of all
mitigation measures listed in the Defra Inventory of
Methods to Control Diffuse Water Pollution (Newell
et al. 2011), the estimated percentage reductions in
emissions for specific pollutants were much greater,
ranging from 0 to 70.8%.
Farm Type Nitrate (NO3) Phosphorous Sediment Ammonia (NH3)
Methane (CH4)
Nitrous oxide (N2O)
Cereals 4.0% 6.0% 7.8% 9.0% 0.0% 6.2%
General cropping 3.9% 6.0% 7.8% 9.0% 0.0% 6.1%
Horticulture 4.5% 6.5% 8.9% 9.0% 0.0% 7.7%
Dairy 4.9% 11.6% 4.9% 15.2% 10.4% 7.6%
Lowland grazing 2.4% 10.4% 4.7% 0.3% 0.0% 3.0%
Mixed 3.0% 14.8% 6.3% 4.8% 0.3% 5.4%
FARMSCOPER also allows the total emissions for each pollutant in kg per hectare per year (kg ha‐1 yr‐1) resulting from
scenarios 2 and 3 to be compared (see below).
Farm Type Nitrate (NO3) Phosphorous Sediment Ammonia (NH3)
Methane (CH4)
Nitrous oxide (N2O)
Cereals 4.0% 6.0% 7.8% 9.0% 0.0% 6.2%
Lowland grazing 2.4% 10.4% 4.7% 0.3% 0.0% 3.0%
Mixed 3.0% 14.8% 6.3% 4.8% 0.3% 5.4%
For improvement scenarios, FARMSCOPER predicts percentage reduction in emissions (relative to the baseline scenario)
(see table). Under scenario 2, the current pollutant emissions based on an estimate of the existing level of mitigation
measures implemented, the estimated percentage reductions in pollutant emissions ranged from 0 to 15.2%.
Farm Type Nitrate (NO3) Phosphorous Sediment Ammonia (NH3)
Methane (CH4)
Nitrous oxide (N2O)
Cereals 38 0.2 159 7 0 7
General cropping 37 0.1 117 7 0 7
Horticulture 34 0.3 247 5 0 4
Dairy 40 0.5 104 36 173 10
Lowland grazing 24 0.4 80 15 98 7
Mixed 51 0.4 95 43 90 10
Conclusion
FARMSCOPER estimated that current levels of mitigation measure implementation have reduced total pollutant loads
by between 3 and 10%, as compared to a scenario where no mitigation measures were in place. It also predicted that,
should there be significant uptake of the full range of mitigation measures, pollutant loads could be reduced further by
significant amounts for sediment (66%), phosphorous (47%), nitrate (22%), ammonia (30%) and nitrous oxide (16%).
Case study adapted from: Zhang et al.,2012
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Secondary benefits of catchment management It is widely accepted that the delivery of catchment management interventions will
produce a wide array of ancillary benefits that could make considerable contributions to
improving the ecological condition of rivers and towards other economic,
environmental or nature conservation targets.
Secondary environmental benefits
In addition to determining the primary benefit obtained through catchment
management interventions, it is also important for any secondary environmental
benefits achieved to be recorded and quantified.
This can be undertaken using a number of survey, monitoring and modelling
approaches that assess how an intervention can enhance the provision of other
ecosystem services across a catchment and to quantify the economic gains achieved by
all of the groups engaged in the process.
Perhaps the most common example of this occurring is where interventions, such as
wetland creation or restoration, which have been designed and targeted to enhance the
regulation of water quality also play a key role in the regulation of water quantity (high
and low flows). It is clear that these measures, if targeted into multifunctional areas of
land that regulate several different ecosystem services, are capable of enhancing the
provision of several of them.
In addition, considerable research is also being undertaken to asses the ability of
catchment management interventions to restore ecosystem health, deliver increased
biodiversity and for them to therefore have significant conservation value. In one such
study, undertaken by Jobin et al (2003) in Canada, it has been demonstrated that the
creation of riparian buffer strips (especially wooded ones) can significantly increase the
overall species richness and insectivorous bird abundance across a catchment.
Many of the on‐farm measures described in this review have also been shown to reduce
the emission of greenhouse gases from agricultural land and there is growing evidence
that many may act to increase their sequestration. Careful targeting of catchment
management measures to land areas with the greatest carbon sequestration potential
will optimise the levels of sequestration achieved.
At a more strategic level, several groups and organisations (such as Durham Wildlife
Trust, the Westcountry Rivers Trust, and many others) have developed methodologies
for the mapping of land which contributes to the provision of ecosystem services. When
combined together, these studies reveal that there are many multi‐functional areas that
play a key role in the delivery of several ecosystem services.
These ecosystem services mapping exercises allow us to identify sections of the
catchment where these multifunctional, ecosystem services‐providing areas may come
into direct conflict, and therefore be compromised by, other human activities, such as
intensive agriculture or urban development.
This so‐called ‘ecosystem services’ approach allows us to identify where catchment
management or policy level interventions designed to improve the provision of one
ecosystem service (e.g. water quality) may also yield concurrent improvements in the
provision of other ecosystem services. Ultimately, this approach allows interventions to
be delivered in a targeted, integrated and balanced way that delivers the greatest
environmental improvement for the resources available.
A brown trout from a healthy river
64
Assessment of financial costs and benefits
For the full benefit of catchment management interventions to be assessed, it is also
important for all of the parties involved (funders, deliverers, beneficiaries, landowners)
to have a clear understanding of the financial costs and benefits of the proposed
change. For many interventions, a clear and detailed understanding of their cost of
delivery has already been gained and, as we have described previously, the evidence for
their environmental benefit continues to be gathered.
The key link that will need to be established, once this evidence is in place, is how the
environmental benefits achieved can be translated into financial benefits for the funder,
the beneficiaries of the ecosystem service or the land managers who have implemented
the intervention (e.g. as the result of increased efficiency or reduced costs incurred).
This information will then allow the cost‐benefit of catchment management
interventions to be explored in more detail. At present, the robust extrapolation of the
cost‐benefit ratios calculated up to the sub‐catchment or catchment scale remains a
significant challenge that will require careful consideration and further research.
Payments for Ecosystem Services (PES) Payments for Ecosystem Services (PES) schemes are market‐based instruments that connect ’sellers’ of ecosystem
services with ‘buyers’. The term Payments for Ecosystem Services is often used to describe a variety of schemes in which
the beneficiaries of ecosystem services provide payment to the stewards of those services. Payments for Ecosystem
Services schemes include those that involve a continuing series of payments to land or other natural resource managers
in return for a guaranteed or anticipated flow of ecosystem services.
At present, farmers, who represent less than 1% of our society, currently manage ~80% of our countryside and are
largely responsible for the health of the ecosystems it supports. However, despite this key role for farmers in managing
our natural ecosystems, they are currently only paid for the provision of one ecosystem service; food production. The
idea behind Payments for Ecosystem Services is that those who are responsible for the provision of ecosystem services
should be rewarded for doing so, representing a mechanism to bring historically undervalued services into the economy.
A Payments for Ecosystem Services scheme can be defined as a voluntary transaction where (1) a well‐defined
ecosystem service (or a land‐use likely to secure that service) is being ‘bought’ by (2) an ecosystem service buyer
(minimum of one) from (3) an ecosystem service seller (minimum of one) if, and only if, (4) the ecosystem service
provider secures ecosystem service provision (conditionality).
An example of a PES scheme: Upstream Thinking
Drinking water is a vital ecosystem service that we derive from our river catchments and there is significant scope for
water companies interested in the quality of the raw water they treat for supply to customers as drinking water.
South West Water’s Crownhill water treatment works in Plymouth currently treats around 55‐60 million litres of water
each day and it is anticipated that over the next 20 years the demand for water in Plymouth will increase steadily
towards 100 million litres a day. In addition to this increased demand for water, there is evidence that declining water
quality in the river sources used to supply the Crownhill works could concurrently increase the costs and risks associated
with the treatment of the raw water undertaken there.
The South West Water Upstream thinking project is a PES scheme in which the water company invests in catchment
management on behalf of their customers in an attempt to avoid incurring the extra costs and risks associated with
treating low quality raw water at the works. If the average cost of treating water at Crownhill is increased by £5 per
million litres treated (~10%) due to poor raw water quality then the removal of this pressure could save over £2 million on
treatment costs over the next 20 years (at a treatment volume of 60 million litres a day).
CASE STUDY
Under the current situation, where land is managed
exclusively for agricultural production, only the private
profits from this activity are realised. By identifying where
another ecosystem service, such as improved water quality,
may be provided and by offering either a minimum payment
to cover profit forgone or a maximum possible payment
based on the overall value to society, the buyer can
incentivise the seller to change, or even switch, their
practice and therefore deliver the improvements in the
ecosystem service they require.
65
GOVERNANCE & STRATEGIC PLANNING
66
The EC Water Framework Directive 2000 Perhaps the greatest driver for catchment management is the requirement for the
condition of UK river waterbodies to meet the quality standards set out in the European
Commission Water Framework Directive 2000 (WFD, 2000). The WFD assessment
process, which applies to lakes, rivers, transitional and coastal waters, artificial and
heavily modified waterbodies, and groundwater, has set more rigorous and higher
evaluation standards for the quality of our aquatic ecosystems.
The main objectives of the WFD are to prevent deterioration of the status of water‐
bodies, and to protect, enhance and restore them with the aim of achieving ‘good
ecological status’, or ‘good ecological potential’ in the case of heavily modified
waterbodies. Similarly, groundwater bodies need to reach a good status as they are
required to maintain drinking water quality. The WFD aims to achieve at least good
status for all water bodies by 2015 or, if certain exemption criteria are met, then by an
extended deadline of 2027.
The Water Framework Directive delivery process essentially occurs in three phases: (1)
waterbody condition assessment to characterise ecological status, (2) investigations to
diagnose the causes of degradation, and (3) a programme of remedial catchment
management interventions set out in a River Basin Management Plan (RBMP).
In addition to protecting and improving the ecological condition of aquatic ecosystems,
the Water Framework Directive has several further overarching aims that include;
Promoting sustainable use of water as a natural resource
Conserving habitats and species that depend directly on water
Contributing to mitigating the effects of floods and droughts
GOVERNANCE & PLANNING
The catchment partnership approach In recent years it has been increasingly recognised that enhancing the delivery of
ecosystem services through better catchment management should not only be the
responsibility of the public sector, but also the private and third sectors.
Alongside this movement towards shared responsibility, there is also now a growing
body of evidence that far greater environmental improvements can be achieved if all of
the groups actively involved in regulation, land management, scientific research or
wildlife conservation in a catchment area are drawn together with landowners and other
interest groups to form a catchment management partnership.
A number of research projects have now been able to demonstrate that an empowered
catchment area partnership comprised of diverse stakeholders and technical specialists
from in and around a catchment, can be responsible for coordinating the planning,
funding and delivery of good ecological health for that river and its catchment. They
have also shown us that an integrated stakeholder‐driven assessment of a catchment
will we be enable us to develop a comprehensive understanding of the challenges we
face and, following this, to develop a strategic, targeted, balanced and therefore cost‐
effective catchment management intervention plan.
Overall (top) and fish (bottom) status of
waterbodies in the Tamar catchment
under the Water Framework Directive
classification system.
67
The ‘Catchment-Based Approach’ (CaBA) In response to this increased understanding of the potential benefits of participatory
catchment planning, undertaken with local stakeholders and knowledge providers, in
2011 the Environment Minister Richard Benyon MP announced that the UK Government
was committed to adopting a more ‘catchment‐based approach’ to sharing information,
working together and coordinating efforts to protect England’s water environment.
Following their announcement, DEFRA began working with the Environment Agency to
explore improved ways of engaging with people and organisations that could make a
real difference to the health of our rivers, lakes and streams.
In the summer of 2011, they launched a new initiative to test the catchment partnership
approach in ten 'pilot' catchments. Alongside these ten Environment Agency‐led pilots
they also established fifteen further pilot catchments that would be hosted by other
organisations.
The outputs of the DEFRA Catchment Pilot Projects, which are now presented on the
Catchment Change Management Hub website (ccmhub.net), reveal that the new
partnerships created in many catchments were able to generate ambitious and
comprehensive plans for the improvement of river ecological health and water quality.
In response to the success of the Pilot Catchments, in May 2013 DEFRA announced their
policy framework for the roll‐out of the Catchment‐Based Approach (CaBA) to all of the
~80 catchments in England and catchment hosts will be selected in autumn 2013.
Rural Economy & Land Use (RELU) Programme The interdisciplinary RELU Programme, funded between 2004 and 2011, had the
aim of harnessing the sciences to help and promote sustainable rural development
and advance understanding of the challenges caused by this change today and in
the future. Research was undertaken to inform policy and practice with choices on
how to manage the countryside and rural economies.
The findings of several RELU projects highlighted the need for more sustained and
two‐way communication with stakeholders about land management. The
researchers have demonstrated that new ‘knowledge‐bases’ can be established that
combine local knowledge with external expertise.
The research has also identified a number of techniques that enable stakeholders,
who may start with different views and levels of understanding, to redefine the
issues collectively in a way that can help them find innovative solutions with
multiple benefits.
CASE STUDY
Perhaps the best example of this work is the ESRC‐funded
RELU study, led by Laurie Smith from SOAS at the
University of London, which developed the concept of a
‘catchment area partnership’ (CAP) and ‘catchment area
delivery organisations’ (CADO) approach for the delivery
of catchment management in England and Wales.
Piloted in the Tamar and Thurne catchments, the project
drew on the scientific and social accomplishments of
several innovative catchment programmes in the USA
and other European countries and examined how they
could be adapted for use in the UK.
The SOAS project established a clear catchment management ‘roadmap’ (above) on how to: create a catchment
partnership, integrate scientific investigation with policy, establish governance and legal provisions; foster decision‐
making and implementation at the appropriate governance level to resolve conflicts; and to share best practice.
Several of the other RELU research projects to focus on catchment management characterised a positive feedback loop
in participatory catchment management planning whereby small initial changes initially yield a small benefit that, in
turn, goes on to encourage far bigger changes later in the process. The common result of this feedback loop is the
building of local capacity through levering in tangible new resources, including fresh commitments of time and external
funding and the supply of expertise.
The DEFRA Catchment‐Based Approach
Policy Framework, May 2013.
68
Catchment-Based Approach (CaBA) Pilots To develop an understanding of how the catchment‐based approach could work in practice, a series of catchment‐level
partnerships were developed through a pilot phase (May 2011 to December 2012). Ten of these partnerships were hosted
by the Environment Agency (EA) and 15 were led by a range of stakeholders such as Rivers Trusts, Groundwork, water
companies and community groups. A group of 41 wider catchment initiatives were also established that were not part of
the formal evaluation.
Some examples of successful catchment partnerships established through the pilot phase of the catchment‐based
approach are summarised below.
CASE STUDY
The Tamar Plan
The Tamar Catchment Plan adopted a stakeholder‐led ‘ecosystem services’ approach
to catchment planning. This has involved the host organisation working with
stakeholders to identify areas within the catchment which play, or have the potential
to play, a particularly important role in the delivery of clean water and a range of
other benefits (services) to society.
Through this process the stakeholders have developed; (1) a shared understanding of
the pressures affecting ecosystem service provision in the catchment, (2) a shared
vision for a catchment landscape with a blend of environmental infrastructure that
may be able to deliver all of these vital services optimally in the future, and (3) a clear
understanding of what is currently being done to realise this vision and what
additional actions may be required to bring it to full reality.
Saving Eden
The Eden Pilot Project, hosted by Eden Rivers Trust within the Eden and Esk
management catchment encouraged greater levels of participation including
increased levels of engagement with ‘difficult to reach’ groups and facilitation of
knowledge exchange between stakeholders. The pilot project produced a plan called
‘Saving Eden’, which summarises the current health and the necessary actions
required to deliver Good Ecological Status in the Eden catchment.
Saving Eden says, ’we asked over 1,000 people, face‐to‐face or online, whether and
why they care about rivers and how a plan might work...People told us that they care
about things that aren’t really critical to WFD: beauty, wildlife, access and having
water for them to use. Our catchment community wants a plan that is about these
things as well. So our plan is going to be about what people care about, the necessary
WFD requirements, and achieving other parallel standards like those in the Habitats
Directive. Where there are different standards we will pursue the highest one possible.’
The Tyne Catchment Plan
The Tyne Catchment Plan was created by Tyne Rivers Trust who asked people in the
catchment to tell them about the biggest issues for their rivers and to suggest
projects to tackle those issues.
The Tyne Catchment Plan, which is the result of that process, is a ‘wish list’ of
proposed projects that will; (1) deliver better rivers for people to enjoy and value, (2)
increase community involvement in local decision‐making about river issues, (3)
engage and educate those who don’t know the value and importance of rivers, (4)
create robust and resilient environments which will cope with weather extremes and
climate change, (5) make best use of the available resources, research and evidence
in supporting work across the catchment, and (6) help deliver the targets set out in
European legislation like the Water Framework Directive and the Habitats Directive.
The planning process undertaken in the Tyne Catchment included a survey to which
over 200 people responded and which raised 342 different issues across the
catchment. The results of this survey gave them a real understanding of what people
think is important for the future of the Tyne and its tributaries.
The process also included a full assessment of all the projects already underway in
the catchment and developed a prioritised list of 58 new proposed projects that the
catchment partnership thought would be important going forward.
69
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71
Further information & contacts The Westcountry Rivers Trust is an environmental charity (Charity no. 1135007,
Company no. 06545646) established in 1995 to secure the preservation, protection,
development and improvement of the rivers, streams, watercourses and water
impoundments in the Westcountry and to advance the education of the public in the
management of water.
Our vision is:‐
A healthier living, working natural environment on a landscape scale.
Protection of ecosystem function and natural resources, particularly water.
To facilitate a move towards a society that values the natural environment and the
services it provides – Payments for Ecosystem Services.
Educate and reconnect society with the natural environment.
To base our work on good scientific research.
To find out more out more about the Westcountry Rivers Trust please visit our website
at www.wrt.org.uk or contact one of our team;
Dr Dylan Bright Director
Trained as a limnologist and freshwater ecologist Dylan is Director of the Rivers Trust
and Managing Director of Tamar Consulting. He is an experienced farm and land
management advisor and has led Defra funded projects investigating Water Framework
Directive Metrics and implementation of catchment management plans to inform good
status.
Email: [email protected]
Dr Laurence Couldrick Head of Catchment Management
Dr Laurence Couldrick is the Head of Catchment Management at the Westcountry
Rivers Trust and Project manager for the Interreg funded WATER Project on the
Payments for Ecosystem Services approach to river restoration.
Email: [email protected]
Dr Nick Paling GIS & Communications Manager
Nick is an applied ecologist and conservation biologist with 8 years of experience using
spatial techniques to inform conservation strategy development and catchment
management. He provides data, mapping & modelling support for all Trust projects and
coordinates and manages a number of large‐scale monitoring programmes currently
being undertaken by the Trust.
Email: [email protected]
Lucy Morris Data to Information Officer
Lucy is an ecologist and data analyst specialising in the communication of the Trust’s
scientific outputs to a wide variety of audiences. Lucy collates and assesses data and
evidence before preparing press releases, articles and technical documents for
publication in a variety of media types, including traditional print media, film/TV, online/
websites and new media such as social networking sites.
Email: [email protected]
Hazel Kendall Upstream Thinking Project Officer
Working with Upstream Thinking partners to collate information and data collection for
reporting, Hazel will combine this role with bio‐monitoring undertaken as part of the
proof of concept study supporting the physical works of the initiative, using a range of
sampling techniques and Biotic Indices.
Email: [email protected]
72
The Upstream Thinking Project is South West Water's flagship programme of
environmental improvements aimed at improving water quality in river catchments in
order to reduce water treatment costs. Run in collaboration with a group of regional
conservation charities, including the Westcountry Rivers Trust and the Wildlife Trusts of
Devon and Cornwall, it is one of the first programmes in the UK to look at all the issues
which can influence water quality and quantity across entire catchments.
The principal, over‐arching aim of any catchment management work is to improve the
water quality in our freshwater ecosystems and to make a significant contribution to their
attainment of good ecological status in accordance with requirements of the EU Water
Framework Directive. It is therefore vital that sufficient evidence is collected to provide an
objective and robust assessment of the improvements delivered.
In this review we explore the data and evidence available, which, taken together,
demonstrate qualitatively and quantitatively that the delivery of integrated catchment
management interventions can realise genuine improvements in water quality. To
support the evidence collected, we have also summarised a number of case studies which
demonstrate catchment management in action.
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