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No. 4 April 2001

The National Pollutant Inventory (NPI) is

an internet database designed to provide

the community, industry and government

with information on the types and amounts

of certain chemicals being released to air

and water. The database is a program

cooperatively implemented by the

Commonwealth, States and Territories.

Industries that use certain substances,

burn fuel or waste or emit certain

substances to water, in quantities that

exceed thresholds, are required to report

their emissions to the NPI. The EPA provides

industry with emissions estimation handbooks,

training and technical advice to ensure

that industry reports their emissions to

the highest practicable standard.

Emissions from other diffuse and

sub-threshold point sources (aggregated

emissions data) are estimated by the EPA

using models and other published emission

estimation techniques. The models are used

to estimate aggregate emissions (see

Aggregate emission rates) of total

phosphorus (TP) and total nitrogen (TN) to

waterways. Phosphorus and nitrogen are

important nutrients for plant growth and

very high concentrations in water can lead

to excessive growth resulting in proliferation

of weeds or algal blooms. Due to the impact

these nutrients can have on waterways,

aggregate emissions of TP and TN in

Queensland have been modelled for the NPI

in the Dawson River, Johnstone River and

south east Queensland catchments.

The EPA collates and validates the data

and submits it to the Commonwealth for

publishing on the NPI database. The NPI

database can be searched by substance

(e.g. total nitrogen) or by location (e.g.

water catchment). It can be accessed at

http://www.npi.ea.gov.au

Information on reporting requirements and

emissions estimation techniques, including

the methodology for aggregated emissions

data can be accessed at http://

www.env.qld.gov.au/environment/

business/inventory/watercatchment.

The Dawson study� summary

The objective of the study was to

estimate the average annual

nutrient (TN and TP) emissions to

the Dawson River catchment using

the Catchment Management

Support System modelling package

(see The Model � CMSS) for

incorporation in the NPI.

CMSS estimated that certain land

uses were contributing nutrients to

the waterways in the catchment.

In summary;

� grazing and dryland cropping

were predicted to contribute

the most TP;

� grazing and state forest were

predicted to contribute the

most TN.

The National Pollutant Inventory

Dawson Valley.

Nutrient loads from the Dawson River Catchment:National Pollutant Inventory

Delusion Creek.

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The Dawson CatchmentThe Dawson River originates near the

junction of the Carnarvon and the Great

Dividing Ranges. Near Duaringa, it merges

with the McKenzie River, eventually

forming the Fitzroy River, which flows to

Keppel Bay, south east of Rockhampton.

The study area encompasses the Dawson

River and its tributaries, including the Don

and Dee Rivers and Callide Creek.

Sub-catchmentboundariesA land use map was sourced from the

National Land and Water Resources Audit

and sub-catchments were chosen based

on the location of Department of Natural

Resources and Mines water quality

monitoring stations. Monitoring stations

included in the study were those with

sufficient flow data and more than 10

nutrient (TN and TP) measurements.

From the 26 DNR monitoring sites in the

Dawson catchment, eight had sufficient

data for inclusion.

Using a combination of water quality data

collected from the DNR stations and

literature-based nutrient generation rates

(average annual measure of nutrient

production from a given land use), the

aggregate emission rates (see Aggregate

emissions) for land use types in the

catchment were estimated using CMSS

(see The model � CMSS).

The model � CMSSThe Catchment Management Support

System (CMSS) modelling package predicts

the average annual nutrient emissions

from different land uses in a designated

catchment. The model uses published

nutrient generation rates in combination

with detailed land use maps specific to

the catchment.

In addition to using published nutrient

generation rates, TP generation rates for

grazing and cropping were derived from

water quality data collected from DNR

monitoring stations. Specific generation

rates for TN from grazing, forestry and

cropping were also calculated from field

data. CMSS was then used to estimate

aggregate emissions of TP and TN (see

Aggregate emissions) for each

sub-catchment in the Dawson catchment.Palm Tree Creek supports a species of palmtree endemic (localised) to the area.

Dawson River at Taroom.

Mimosa Creek in the Becker�s sub-catchment ispredicted to receive one of the highest totalphosphorus loads in the Dawson catchment.

Grazing land uses (sheep and cattle)

dominate in the Dawson River catchment

comprising 77 percent of the total area.

State forests (12 percent), dryland cropping

(7 percent) and national parks (3 percent)

are also present in the catchment.

Irrigated cropping (1 percent) is carried

out in two irrigation areas, centred on the

Dawson River and Callide Creek. Other

features of the catchment include several

small urban settlements (0.3 percent).

Land UseThe predominant land use in the Dawson

Catchment is grazing. Other land uses

include State forest, which is land

managed for production from relatively

natural forests, national parks, cropping,

which includes crop rotation, permanent

cropping and plantations, irrigated

cropping and urban uses. In-stream vegetation use nutrients in the water.

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TP � aggregateemission ratesThe Don and Callide subcatchments had

the highest TP emission rates in the

Dawson catchment. This may be the

result of land use management practices

that differ from the rest of the

catchment. Woodleigh also had a high

TP emission rate (0.34kg/ha/yr) and the

highest land use percentage of cropping

(15 percent) and irrigated cropping

(3 percent).

Grazing (80 percent) and dryland cropping

(12 percent) emissions were predicted to

contribute most of the TP to the Dawson

catchment (see Pie charts)

TN � aggregateemission ratesThe Glebe sub-catchment had the highest

TN emission rate (1.7kg/ha/yr) and the

highest percentage of forestry (27 percent)

and national parks (7 percent) in the Dawson

catchment. The majority of the remainder of

the land was used for grazing (64 percent).

The Beckers and Utopia sub-catchments also

had high emission rates and both had large

forested areas (15 percent and 16 percent

respectively) as well as large areas of grazing

(70 percent and 78 percent respectively).

Grazing and forestry were predicted to

contribute most of the TN emissions

(82 percent) to the Dawson catchment

(see Pie charts).

Pie chartsThese pie charts

depict the predicted

total nutrient loads

from different land

uses in the Dawson

catchment.

Aggregate emissionsThe nutrient emissions originating from

both diffuse sources and sub-threshold

point sources (aggregate emissions) were

estimated for sub-catchments in the Dawson

River basin using CMSS.

In general, grazing (80 percent) and

dryland cropping (12 percent) produced

most of the TP emissions, and grazing

(43 percent) and state forest (39 percent)

produced most of the TN emissions in the

Dawson River basin. The results are

illustrated in the pie charts on this page.

Aggregate emission rates from individual

sub-catchments are presented in the

tables below. The data displayed are

specific to each subcatchment and do not

include emission rates from upstream

subcatchments. The colour coding was

based on comparison of emissions within

the Dawson catchment only.

Callide Creek is estimated to receive highemissions of TP from the surrounding land.

Grazing makes up 77 percent of the majorland uses in the Dawson River catchment.

Subcatchment TN Load per Unit Area(kg/ha/yr)

Delusion 0.94

Taroom 0.95

Theodore 1.03

Don 1.07

Duaringa 1.12

Callide 1.12

Woodleigh 1.14

Utopia Downs 1.31

Beckers 1.47

Glebe 1.70

AVERAGE 1.26

Subcatchment TP Load per Unit Area(kg/ha/yr)

Glebe 0.24

Utopia Downs 0.27

Duaringa 0.30

Delusion 0.30

Beckers 0.31

Taroom 0.33

Theodore 0.33

Woodleigh 0.34

Don 0.52

Callide 0.55

AVERAGE 0.33

TP TN

TP

TN

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FurtherinformationNutrient emission modelling in the Dawson

River basin using Catchment Management

Support System (CMSS). M. Joo, V. McNeil,

E. O�Brien and R. Fearon. (October 2000)

Department of Natural Resources and

Environmental Protection Agency.

ISBN 0 7345 1716 5.

Visit the EPA Environmental and

Technical Services (Water) website at:

www.env.qld.gov.au/environment/science/

water

Use the database at the NPI site:

http://www.environment.gov.au/epg/npi/

Visit the Department of Natural

Resources and Mines website at:

http://www.dnr.qld.gov.au/

Bp1346 April 2001 � Recycled paper saves energy and resources

Nutrients in waterwaysNitrogen and phosphorus are important

nutrients for plant growth. Very high

concentrations in the water can lead to

excessive plant growth resulting in

proliferation of weeds or algal blooms.

Natural sources of phosphorus include

weathering of rocks and decomposition of

organic matter. Nitrogen can be present in

waterways due to the breakdown of plant

and animal matter, production of wastes

by biota, and land drainage.

Concentrations of these nutrients in

waterways can be increased by human

activities such as land cultivation,

wastewater treatment and stormwater

runoff. They are also present in a number

of domestic household products including

detergents and garden fertilisers.

Comparison with othercatchments

It is difficult to compare catchments

because of differences in land uses, land

use management practices, underlying

geology, climate and vegetation.

For example, comparing the Dawson River

and Johnstone River catchments is

complicated. Unlike the Dawson River

catchment, land uses within the

Johnstone River catchment are

predominantly rainforest (54 percent),

cattle grazing (21 percent) and sugar

cane farms (12 percent). The climate

and topography are also substantially

different. There was generally lower

emission rates of TP and TN in the Dawson

River compared with the Johnstone

River catchment which may result from

a combination of these variables.

QueenslandCatchments in the NPIIn addition to the Dawson River

catchment, aggregate emission rates

for the Johnstone River and south east

Queensland catchments have also been

modelled for the NPI. This data in

addition to the Dawson Catchment

data, is available on the NPI internet

database (http://www.environment.

gov.au/epg/npi/) and can be

searched by substance (e.g. total

nitrogen or total phosphorus) or by

location (e.g. water catchment �

Dawson, Qld; Johnstone, Qld; etc.).

Predicted emissions to the air as well as

water are available for these areas, as

well as areas in other states.

Bogamoss near Palm Tree Creek.

Delusion creek is surrounded by land usedmainly for grazing.

National Parks comprise 3 percent of the landuse in the Dawson River catchment.

The fascinating bogamoss habitats can be foundin the Dawson Valley. These areas are a resultof freshwater upwellings through faults in theunderlying stone. A mound is built up from yearsof silt or clay deposition and resembles aswamp. A range of animals and plants areassociated with these mounds.

Glebe Weir regulates water flow in theupper reaches of the Dawson river.