INTERNATIONAL ASSOCIATION OF HYDROGEOLOGISTS the worldwide groundwater organisation

INTERNATIONAL ASSOCIATION OF HYDROGEOLOGISTSthe worldwide groundwater organisation

THE AGRICULTURAL INTERFACETHE AGRICULTURAL INTERFACEcritical to groundwater resource status in the EU and beyond critical to groundwater resource status in the EU and beyond

Prof Dr Stephen Foster (IAH Past President 2004-08)

World Bank – Groundwater Management Team Director World Bank – Groundwater Management Team Director University College London – Visiting Professor of Groundwater ScienceUniversity College London – Visiting Professor of Groundwater Science

WWCMember

IUGS Affiliate

UN-Water Partner

GWPMember

AGRICULTURE & GROUNDWATERAGRICULTURE & GROUNDWATER

an intimate relationshipan intimate relationship

BECAUSEBECAUSE

agricultural activity occupies large proportion agricultural activity occupies large proportion of most aquifer recharge areasof most aquifer recharge areas

CONSEQUENCESCONSEQUENCES– predominant influence on groundwater qualitypredominant influence on groundwater quality– affects mechanisms/rates of aquifer rechargeaffects mechanisms/rates of aquifer recharge

– also the major consumer of (ground)water resourcesalso the major consumer of (ground)water resources

must understand and control relationship must understand and control relationship to conserve/protect groundwater resourcesto conserve/protect groundwater resources

AGRICULTURE & GROUNDWATERAGRICULTURE & GROUNDWATERScope of PresentationScope of Presentation

• focused at science-policy interfacefocused at science-policy interface• in each facet in each facet start with the scientific realitiesstart with the scientific realities• then then concentrate on the policy implicationsconcentrate on the policy implications

• conscious of climate-change dimensionsconscious of climate-change dimensions• groundwater often key to adaptive groundwater often key to adaptive

managementmanagement• subtle long-term (but significant) impacts on subtle long-term (but significant) impacts on

groundwater recharge rates and quality likelygroundwater recharge rates and quality likely • increased irrigation demand more immediateincreased irrigation demand more immediate• biofuel cultivation could give rise to concernbiofuel cultivation could give rise to concern


FACETS CONSIDERED :FACETS CONSIDERED :

• Effects of Agricultural Land-Use Effects of Agricultural Land-Use

on Groundwater Quality on Groundwater Quality

• Groundwater Use for Irrigated Groundwater Use for Irrigated AgricultureAgriculture

• Conjunctive Use of Groundwater Conjunctive Use of Groundwater & Surface Water Resources & Surface Water Resources

EFFECT OF AGRICULTURAL LAND-USE EFFECT OF AGRICULTURAL LAND-USE ON GROUNDWATER QUALITY ON GROUNDWATER QUALITY

‘As the Land – So the Water’

• cultivation of permeable soils is a ‘leaky activity’ – thus farmers cultivating land also (accidentally) harvest (and pollute) groundwater

• agricultural land use practices thus markedly influence groundwater quality (especially N compounds + some pesticides leached)

• diagnostic/prognostic capability as regards ‘groundwater quality risks’ now improved - but confirmatory monitoring always needed

DIFFUSE POLLUTION FROM AGRICULTURAL LAND-USE

nutrient leaching

pesticide mobility

Cryptosporidium hazard

saline returns

AGRICULTURAL LAND-USE & AGRICULTURAL LAND-USE &

GROUNDWATERGROUNDWATER widespread nutrient leaching

• well established and often dominant influence (especially intensive monocultures on permeable soils)

• principally NO3 (and in some cases NH4, PO4)

• subsurface denitrification can reduce impact, but only in some hydrogeological conditions

• technical control measures (plant husbandry, fertiliser regimes, livestock density, irrigation scheduling) very important – but for vulnerable aquifers may not be sufficient to protect drinking water and ecosystem interests

DIFFUSE GROUNDWATER POLLUTION FROM AGRICULTURAL LAND USE

long term nitrate trends related to intensification

kgN/ha/a

EXCESS N APPLICATIONS TO SOIL

NO3(mg/l)

GROUNDWATERNO3 CONCENTRATIONS

Groundwater Nitrate Trend Data for Valencia Plain - SpainGroundwater Nitrate Trend Data for Valencia Plain - Spain

• pesticides are designed to be (to some degree) biotoxic

• more localised basis problem than nitrate (usually related to preferential flow in vadose zone, shallow water table, thin low storage aquifers)

• main concern focuses on persistence in subsurface environment of soluble/mobile pesticides and their metabolites used in :– pest/weed control in horticulture/fruit production– weed control on arable/pasture land

AGRICULTURAL LAND-USE & AGRICULTURAL LAND-USE & GROUNDWATERGROUNDWATER

the question of pesticide mobility

Pesticide

Compound

Detections

>0.1 g l-1

Sites where Detected

Maximum(g l-1)

Mean(g l-1)

Mecoprop 36 10 7.10 2.10

Bentazone 2 2 0.12 0.06

Atrazine 14 3 1.40 0.34

Isoproturon 15 5 1.20 0.49

Clopyralid 1 3 0.30 0.06

Benazolin 9 2 0.18 0.09

Dicamba 0 1 0.05 0.04

Chlorotoluron 0 5 0.06 0.05

Pentachlorophenol 0 2 0.04 0.03

MCPA 0 4 0.06 0.03

GROUNDWATER PESTICIDES CONTAMINATION problem of analytical complexity and

spatial + temporal variability in vulnerable aquifers

(South Yorkshire Triassic Sandstone, England –compounds detected during Jan 2002 –June 2003)

• 14 other compounds detected occasionally, almost all at <0.1 g/l)• pesticide metabolites and derivatives not included

(Goody et al, 2005)

IMPACT OF GROUNDWATER POLLUTION IN BRITAINIMPACT OF GROUNDWATER POLLUTION IN BRITAINproblems requiring water utility actionproblems requiring water utility action

mainly nitrates

largely pesticides,arsenic and solvents

various causes - incl. cryptosporidium

CAPITAL COST – E 950million (plus operational costs)

MAIN CAUSES- groundwater quality deterioration- tighter drinking-water standards

M/ld

• Guidelines of ‘Best Agricultural Practice’Guidelines of ‘Best Agricultural Practice’

• Groundwater Special Protected AreasGroundwater Special Protected Areas– Drinking Water Safeguard ZonesDrinking Water Safeguard Zones– Private Agreements on Modified CroppingPrivate Agreements on Modified Cropping

• Groundwater-Friendly Farming RegimesGroundwater-Friendly Farming Regimes (with CAP financial support)(with CAP financial support)

CONTROL OF DIFFUSE AGRICULTURAL POLLUTION approaches and their limitations for protecting groundwater quality

BEST AGRICULTURAL PRACTICE

integration of groundwater quality considerations much welcomed BUT for some crops and soils not capable of reducing average nutrient and/or pesticide losses to below drinking-water guidelines



• Groundwater-Friendly Farming Regimes (with CAP financial support)

CONTROL OF DIFFUSE AGRICULTURAL POLLUTION approaches and their limitations for protecting groundwater quality

GROUNDWATER SUPPLY PROTECTION ZONES

focus for land-use controls

MEASURESMEASURESto preventto prevent to promoteto promote

• deforestation deforestation • ploughing natural pastureploughing natural pasture• urban urban expansion/encroachmentexpansion/encroachment• excessive fertiliser excessive fertiliser applicationapplication• excessive grazing densitiesexcessive grazing densities• unacceptable slurry/sludge unacceptable slurry/sludge

spreading spreading • use of certain pesticidesuse of certain pesticides• expansion of irrigated expansion of irrigated

agricultureagriculture

• afforestation/re-forestationafforestation/re-forestation• reversion to natural pasturereversion to natural pasture• low-intensity agriculturelow-intensity agriculture• recreational land-userecreational land-use• harvesting’ high-quality harvesting’ high-quality

groundwater groundwater • reductions in irrigated area reductions in irrigated area

GROUNDWATER PROTECTED AREASGROUNDWATER PROTECTED AREASspecific measures needed for quality protectionspecific measures needed for quality protection

• declaration of ‘protected areas’ with special powers to constrain/prohibit activities in public interest feasible in most national legal codes • but legal powers may require a level of land-owner compensation that is difficult to administer – and private agreements may be more practicable

• participation of stakeholders always needed with major implications for monitoring and data provision

GROUNDWATER PROTECTED AREASGROUNDWATER PROTECTED AREASlegal basis and limitationslegal basis and limitations

1940 1960 1980 2000 2020

NO

3 C

on

cen

trat

ion

(m

g/l

)IMPACT OF BRITISH ‘NITRATE SENSITIVE AREA’

POLICYin fast response aquifer

Old Chalford - Oxford(Jurassic Limestone)

measured data model output Silgram et al, 2005

required tight control of N applications and limited conversion of arable land to unfertilised pasture and deciduous woodland – with payment of some compensation to farmers



• Groundwater-Friendly Farming RegimesGroundwater-Friendly Farming Regimes (with CAP financial support)(with CAP financial support)

CONTROL OF DIFFUSE AGRICULTURAL POLLUTION approaches and their limitations for protecting groundwater

quality

GROUNDWATER QUALITY MONITORINGDo we really know what is going on under our

feet ?

substantial investment widely needed with much substantial investment widely needed with much more emphasis on impact monitoring in more emphasis on impact monitoring in

recharge zonesrecharge zones




on Groundwater Qualityon Groundwater Quality



BENEFITS OF GROUNDWATER USE FOR BENEFITS OF GROUNDWATER USE FOR IRRIGATED AGRICULTUREIRRIGATED AGRICULTURE ‘The Silent Revolution’

• massive growth of waterwells for agricultural

irrigation – especially in more arid and/or drought-prone regions

• mainly private investment but frequently stimulated by government waterwell grants, electrical energy subsidies, crop guarantee prices, etc

• initially investment returns are very good both for : – staple crops (groundwater development fuelling

‘green revolution’) – cash crops with improvements in rural livelihoods

and high water productivity

GROUNDWATER FOR AGRICULTURAL IRRIGATION

controlling demand versus regulating use

• many areas with good aquifers showing signs of

excessive groundwater abstraction with question of sustainability over 10-50 year time-base

• more consistent enforcement of controls over illegal waterwell drilling/deepening + installation of larger-capacity well pumps

• ‘irrigation water demand management’ critical to sustainable groundwater resources in such areas (especially in aquifers susceptible to irreversible degradation) – with blend of agronomic, participatory, regulatory and economic measures required

GROUNDWATER FOR AGRICULTURAL IRRIGATION

understanding the ‘use drivers’

• clear that ‘irrigation demand’ is strongly driven

by economic subsidies for irrigation infrastructure, pumping energy and crop prices/risks – which reduce effectiveness of auto-regulation of abstraction through increasing costs in situations of falling water-table

• solution of agricultural sector is invariably so-called ‘irrigation water-use efficiency’ improvements – but unless nature of real water-losses versus recirculation returns well understood and respected this is not effective and can be positively misleading

IRRIGATION WATER IRRIGATION WATER ORIGIN & APPLICATION ORIGIN & APPLICATION

TECHNIQUE TECHNIQUE

major influence on groundwater recharge

rates and scope for ‘real water resource saving’

REAL GROUNDWATER RESOURCE SAVINGSREAL GROUNDWATER RESOURCE SAVINGSfrom improved irrigation techniquesfrom improved irrigation techniques

only reductions in non-beneficial evaporation are real groundwater savings

rh5

Carrizal ValleyMendoza-Argentina

MENDOZA CARRIZAL AQUIFER MENDOZA CARRIZAL AQUIFER growing problem of groundwater salinisationgrowing problem of groundwater salinisation

MENDOZA CARRIZAL AQUIFERMENDOZA CARRIZAL AQUIFERcharacteristics of groundwater flow characteristics of groundwater flow

regimeregime

• declare ‘area of restriction’ to prevent further declare ‘area of restriction’ to prevent further growth in numbers of irrigation waterwells growth in numbers of irrigation waterwells

• constrain spatial transfer of groundwater use rights constrain spatial transfer of groundwater use rights from ‘down-gradient’ areas to ‘terrenos chacra’ from ‘down-gradient’ areas to ‘terrenos chacra’

• intensify monitoring of groundwater levels, use and intensify monitoring of groundwater levels, use and salinity – as basis to ensure continued aquifer salinity – as basis to ensure continued aquifer

drainage drainage

• caution about cumulative effects of improving caution about cumulative effects of improving irrigation efficiency (widespread adoption of ‘drip irrigation efficiency (widespread adoption of ‘drip technology’) since total groundwater resource technology’) since total groundwater resource consumption increasing (even if licensed consumption increasing (even if licensed

abstraction fixed) abstraction fixed)

GROUNDWATER RESOURCES MANAGEMENT GROUNDWATER RESOURCES MANAGEMENT approach in Mendoza – Carrizal Aquiferapproach in Mendoza – Carrizal Aquifer




on Groundwater Qualityon Groundwater Quality



CHALLENGE OF CONJUNCTIVE USE OF GROUNDWATER & SURFACE WATER

RESOURCES the ‘dismal reality’ in many areas

• informal/spontaneous conjunctive use widely

practised in tail zones of major canal commands as ‘coping strategy’ – response of farmers to inadequate canal-water supply (poor maintenance related)

• simultaneously some head-canal zones are experiencing soil waterlogging/salinisation and loss of valuable agricultural land – due to excessive seepage from canals and over-irrigation of fields

• overall cropping intensity thus reduced to < 150%

HYDROGEOLOGICAL CONDITIONS OF GANGETIC PLAINHYDROGEOLOGICAL CONDITIONS OF GANGETIC PLAINinterfluve canals as recharge mounds and rivers as discharge sumpsinterfluve canals as recharge mounds and rivers as discharge sumps

CHALLENGE OF CONJUNCTIVE USE OF GROUNDWATER & SURFACE WATER

RESOURCES scientific logic frustrated by social barriers

• integrated modelling for tropical climates often

demonstrates that cropping intensity for entire command area could be increased to 200-250% with ‘planned conjunctive use’ and better crop choices could further enhance ‘irrigation water productivity’

• but how to overcome social and economic obstacles to rationalising conjunctive use (political power of head-canal land owners, comparative water cost to users and initial capital investment requirements) ?

AGRICULTURE & GROUNDWATERGeneral Conclusion

• need very widely to move from ‘opportunistic water engineering and agricultural development to integrated land and water management including full consideration of groundwater ‘ (long overdue even in EC)

• in our overall long-term interest and especially so facing the need to adapt to accelerated climate change

www.worldbank.org/gwmate

www.iah.org

INTERNATIONAL ASSOCIATION OF HYDROGEOLOGISTSthe worldwide groundwater organisation

INTERNATIONAL ASSOCIATION OF HYDROGEOLOGISTS the worldwide groundwater organisation

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