Water Availability in the Eastern Mount Lofty RangesSummary of a report to the Australian Government from the CSIRO Murray-Darling Basin Sustainable Yields Project

October 2007

The assessments of current and potential future water availability have been undertaken by considering four scenarios of historical, recent and future climate and current and future development. All scenarios are defined by daily time series of climate variables based on different scalings of the 1895–2006 climate. The first scenario is for historical climate and current development and is used as a baseline against which other scenarios are compared. The second scenario is for recent climate and current development and is intended as a basis for assessing future water availability should the climate in the future prove to be similar to that of the last ten years. The third scenario is for future climate and current development and evaluates three global warming scenarios using 15 global climate models to provide a spectrum of possible climates for 2030. From this spectrum three variants are reported: a median (or best estimate), a wet variant and a dry variant. The fourth scenario is for future climate and future development and considers the effects of both a 2030 climate and the expansions in farm dams and commercial plantation forestry expected under current policy, and the changes in groundwater extractions anticipated under existing groundwater plans.

The project framework begins with definition of sub-catchments for modelling and regions for reporting, and with definition of the climate and development scenarios to be assessed (including generation of the time series of climate data that describe these scenarios). The climate data form inputs to spatio-temporal modelling of the implications of these climate scenarios for catchment runoff and groundwater recharge. The catchment development scenarios (farm dams and forestry) are modifiers of the resulting modelled runoff time series. The runoff implications are then propagated through existing river system models. The recharge implications are propagated through groundwater models – for the major groundwater resources – or considered in simpler assessments for the minor groundwater resources. The connectivity of surface and groundwater is assessed and the actual volumes of surface-groundwater exchange under current and likely future groundwater extraction are quantified. Monthly water balances for the last 10 to 20 years are analysed using all relevant existing data and remotely-sensed measures of irrigation and floodplain evapotranspiration, and are compared to the river modelling results. The implications of the scenarios for water availability and water use under current water sharing arrangements are then assessed and synthesised.

The uncertainty in the assessments is considered from the perspective of “IF this future” (of climate and development) “THEN these hydrologic implications”. There is uncertainty in both the IF and the THEN. The uncertainty in the IF is typically large, since the degree of future global warming cannot be accurately predicted. Additionally, there is still considerable uncertainty in predictions of rainfall change resulting from global warming. The uncertainty in the THEN stems from the adequacy of hydrologic and meteorologic data and the imperfect predictions of hydrologic response to climate change given current understanding.

Scenarios assessed

2 Water Avai labi l i ty in the Eastern Mount Lofty Ranges

Acknowledgments Prepared by CSIRO for the Australian Government under the Raising National Water Standards Program of the National Water Commission. Important aspects of the work were undertaken by Sinclair Knight Merz; Resource - Environmental Management Pty Ltd; Department of Water and Energy (New South Wales); Department of Natural Resources and Water (Queensland); Murray-Darling Basin Commission; Department of Water, Land and Biodiversity Conservation (South Australia); Bureau of Rural Sciences; Salient Solutions Australia Pty Ltd; eWater Cooperative Research Centre; University of Melbourne; Webb, McKeown and Associates Pty Ltd; and several individual sub-contractors.

Disclaimers Derived from or contains data and/or software provided by the Organisations. The Organisations give no warranty in relation to the data and/or software they provided (including

accuracy, reliability, completeness, currency or suitability) and accept no liability (including without limitation, liability in negligence) for any loss, damage or costs (including consequential damage) relating to any use or reliance on that data or software including any material derived from that data and software. Data must not be used for direct marketing or be used in breach of the privacy laws. Organisations include: Department of Water, Land and Biodiversity Conservation (South Australia), Department of Sustainability and Environment (Victoria), Department of Water and Energy (New South Wales), Department of Natural Resources and Water (Queensland), Murray-Darling Basin Commission.

CSIRO advises that the information contained in this publication comprises general statements based on scientific research. The reader is advised and needs to be aware that such information may be incomplete or unable to be used in any specific situation. No reliance or actions must

therefore be made on that information without seeking prior expert professional, scientific and technical advice. To the extent permitted by law, CSIRO (including its employees and consultants) excludes all liability to any person for any consequences, including but not limited to all losses, damages, costs, expenses and any other compensation, arising directly or indirectly from using this publication (in part or in whole) and any information or material contained in it. Data is assumed to be correct as received from the Organisations.

Photos courtesy of the Department of Water, Land and Biodiversity Conservation, SA.

© CSIRO 2007 all rights reserved. This work is copyright. Apart from any use as permitted under the Copyright Act 1968, no part may be reproduced by any process without prior written permission from CSIRO.

Project framework

Define climate scenarios

Define reporting regions and

sub-catchments

inflows

Rainfall-runoff modelling

Groundwater recharge modelling

River system modelling

Groundwater modelling and assessment

Environmental assessments

ReportingMonthly water

accounts

inflows

SW–GW exchanges

> Cover: Bremer River catchment, SA

> Saunders Creek, SA

> Tributary of Marne River, SA

> Saunders Creek, SA

> Giles Creek, Finniss River catchment, SA

> Tributary of Marne River, SA

October 2007 �

Eastern Mount Lofty Ranges

The Eastern Mount Lofty Ranges (EMLR) region in the far south west of the Murray-Darling Basin is entirely in South Australia and represents less than one percent of the total area of the Basin. The region is based around the Marne, Bremer and Finniss Rivers; these and numerous other rivers and streams drain into the River Murray and into Lake Alexandrina. The region’s population is about 52,000 or slightly less than 3 percent of the Basin total, including the towns of Murray Bridge, Mount Barker and Strathalbyn. Predominant land uses are dryland cropping and grazing. Irrigated cropping – for hay production, vines and horticulture – accounts for less than 3 percent of the total area and there are only small areas of commercial plantation forestry.

Current surface water diversions for irrigation make up less than 0.1 percent of the Basin total, and groundwater use is less than 2 percent of the Basin total.

About 80 percent of surface water used in the region is from the Murray River and Lake Alexandrina, and is considered in the forthcoming report for the Murray region. About 8000 farm dams in the region capture runoff for stock, domestic and irrigation use; water use from these dams has been modelled. Relatively small volumes of groundwater are extracted in the region for stock and domestic use and for irrigation. Wetlands of national significance in the region include the Tookayerta and Finniss Catchments, the Marne River Mouth and Ambersun – West Swamp. Some of the rivers of the region discharge into The Coorong and Lakes Alexandrina and Albert – a Ramsar wetland site.

� Water Avai labi l i ty in the Eastern Mount Lofty Ranges

for the Marne Saunders GMU. The total reduction in stream flow across the region due to current groundwater extraction is estimated to increase to 7 GL/year over the next 50 years; proportionally, these losses would be highest in Tookayerta Creek, with smaller impacts in the Angas, Bremer, Marne and Finniss rivers.

Currently, there is insufficient information to allow reliable assessments of hydrologic impacts on nationally important wetlands in the region. However, the regionally important Fleurieu Swamps may have been affected by reductions in low flows in the Finniss River and Currency Creek caused by water resource development. The Coorong and Lakes Alexandrina and Albert Ramsar site are considered in the Murray region report.

For recent climate and current development

Rainfall for the period 1997 to 2006 was 7 percent lower than the historical average, surface water availability was 26 percent lower and groundwater recharge was 24 percent lower. Long-term continuation of conditions similar to these would reduce average surface water availability by 28 GL/year and reduce average groundwater recharge by 15 GL/year. These changes would in turn reduce net diversions from

farm dams by 6 percent, but due to the large reduction in water availability would effectively increase the level of surface water use to 11 percent. Similarly, under these climate conditions, groundwater use (at current levels) would represent a greater fraction of rainfall recharge: 8 percent greater for the EMLR GMU and 12 percent greater for the Marne Saunders GMU.

For future climate and current development

Under the best estimate (median) 2030 climate water availability would be reduced by about 18 percent, that is, about 22 GL/year less water available (a smaller impact than the last ten years). This would reduce net diversions from farm dams by 5 percent, but due to the large reduction in water availability would effectively increase the level of surface water use to 10 percent. This 2030 climate would have very little impact on the fraction of rainfall recharge that is extracted from groundwater for use. There is considerable uncertainty in the climate predictions for 2030 (different climate models and different global warming scenarios), meaning reductions in average water availability could range from 3 percent to 52 percent. Thus in the future ‘worst case scenario’ water availability would be less than half the current

Key findings

• Current average surface water availability is 120 GL/year and 9 percent of this is diverted for use. Current groundwater recharge from rainfall is 64 GL/year and nearly 19 GL/year is used. Of current groundwater use, 7 GL/year will ultimately come from streamflow due to surface-groundwater connections.

• If the recent climate were to continue for the long-term, surface water availability would reduce to 92 GL/year and rainfall recharge to groundwater would reduce to 50 GL/year. Surface water use would decline slightly but would be 11 percent of the available water.

• The best estimate of climate change by 20�0 is less severe than the recent past: surface water availability would be 98 GL/year and rainfall recharge to groundwater would be about 62 GL/year. There is however, a wide range in the potential impacts of climate change: from little change in surface water availability, to a reduction of more than half.

• Future development of commercial forestry and farm dams could reduce surface water availability by a further 4 GL/year; with impacts focussed in the higher rainfall areas in the south west of the region. If not controlled, groundwater extraction could increase by 60 percent, eventually reducing streamflow by an additional 4 GL/year.

For historical climate and current development

The long-term average annual rainfall for the EMLR is 463 mm, modelled average annual runoff is 30 mm and estimated average groundwater recharge from rainfall is 64 GL/year. Average annual surface water availability is 120 GL/year across the Marne, Bremer, Angas, Finniss, Tookayerta and Currency catchments. Current average net diversions from farm dams (including net evaporation) across these catchments are around 11 GL/year – or about 9 percent of the average available water. The level of use varies however, across the six catchments considered, from about 5 percent to 18 percent.

Current groundwater extraction is a quarter of rainfall recharge in the EMLR groundwater management unit (GMU). Groundwater development is therefore low for this GMU which accounts for the majority of current groundwater use in the region. For the Marne Saunders GMU extraction is two-thirds of rainfall recharge, and while this is high, rainfall recharge for this GMU may be as low as 40 percent of total recharge due to (poorly quantified) flood recharge. Groundwater development is therefore probably moderate to high

October 2007 �

average level, and the level of surface water use would be 15 percent of this. For groundwater, this uncertainty between the dry and wet future climate extremes means extraction could be between 22 and 39 percent of rainfall recharge for the EMLR GMU and between 59 and 101 percent for the Marne Saunders GMU.

For future climate and future development

The combined impact of a potential 16 percent increase in total farm dam volume (an additional 3400 ML) and of a potential doubling of the area of commercial plantation forestry (an additional 2000 ha), both of which could occur by 2030, would be a 3 percent reduction in water availability in addition to the climate change impacts. These changes would actually increase net diversions considerably, as more farms dams provide more opportunity for water use. Future forestry growth would only be likely in the wetter Tookayerta and Currency catchments, for which the modelled reductions in runoff are 17 and 7 percent respectively. The level of surface water use with these developments for the best estimate 2030 climate would be 12 percent.

Without intervention, groundwater extraction from all GMUs is likely to increase in the future. For the best estimates of future extraction (a 60 percent increase) and 2030 climate, extraction would be over 40 percent of rainfall recharge for the EMLR GMU and would exceed rainfall recharge for the Marne Saunders GMU. This increase in extraction would reduce streamflow by an about additional 4 GL/year – a total average impact of about 11 GL/year; the largest proportional impact would be on Tookayerta Creek. Current groundwater allocation planning may however, prevent these levels of extraction being realised.

The flow changes expected due to any future commercial plantation forestry development in the Tookayerta and Currency catchments and as a result of climate change may further affect the ecology of the regionally important Fleurieu Swamps; however, detailed assessments of wetland hydrology have not been made.

Limitations

The runoff modelling for the EMLR region is comparatively good because there are four calibration catchments in the higher runoff producing areas in the western and south-western parts of the region from which to estimate the model parameter values. The river model is conceptually sound, reproducing monthly and inter-annual flow patterns well. The model is considered suitable for assessing relative changes in average flows. Projections of absolute current and longer-term flow volumes are uncertain. This may have implications for the use of these results to assess local in-stream environmental values and availability of water for users. A simple water balance approach has been used for groundwater modelling in the EMLR. This is appropriate given the low priority rating of the GMUs in this region in the context of the overall project. The largest sources of uncertainty for Scenario C results are the climate change projections (global warming level) and the modelled implications of global warming on local rainfall. There are considerable uncertainties associated with the future development projections. There are multiple drivers for commercial plantation forestry and farm dams, many of which have not been considered, and the ways in which land holders will respond to the current policies is uncertain.

> Mt Barker, SA

6 Water Avai labi l i ty in the Eastern Mount Lofty Ranges

Rainfall and Runoff

The mean annual rainfall and modelled runoff averaged over the EMLR region are 463 mm and 30 mm respectively. Rainfall is significantly higher in the winter half of the year and most of the runoff occurs in winter and early spring. The EMLR region covers 0.4 percent of the Murray-Darling Basin and contributes about 0.5 percent of the total runoff in the Murray-Darling Basin.

The mean annual rainfall and runoff over the past ten years (1997 to 2006) averaged over the entire region are 7 percent and 36 percent lower respectively than the 1895 to 2006 long-term means. The 1997 to 2006 runoff is statistically different to the 1895 to 1996 runoff.

Rainfall-runoff modelling with climate change projections from global climate models suggests that future runoff in the EMLR will decrease significantly. Nearly all the modelling results with different global climate models show a decrease in runoff. The best estimate (median) is a 15 percent reduction in mean annual runoff by ~2030 relative to ~1990. The extreme estimates, which come from the high global warming scenario, range from a 44 percent reduction to no change in mean annual runoff. By comparison, the range from the low global warming scenario is from a 15 percent reduction to no change in mean annual runoff.

Projected increase in commercial forestry plantations and farm dam storage volume in the EMLR region by ~2030 of 2000 ha and 3400 ML (or an increase of 16 percent of current farm dam storage volume) respectively are used in the modelling. These projected increases would reduce mean annual runoff by about 3 percent in addition to the median climate change impact on runoff. The median estimate of the combined impact of climate change and increases in plantations and farm dams is an 18 percent reduction in mean annual runoff, with extreme estimates ranging from 3 percent to 46 percent reductions.

Future climate

Current development Future development

Historical 1895-2006

Recent 1997-2006

Dry Best estimate

Wet Dry Best estimate

Wet

mm mm Percent change from Historical

Rainfall 463 429 -19% -5% 1% -19% -5% 1%

Runoff 30 19 -44% -15% 0% -46% -18% -3%

Evapotranspiration 433 410 -18% -4% 1% -17% -4% 1%

> Dawsons Creek, Bremer River catchment, SA

> Bremer River, SA

October 2007 7

Rainfall

Ann

ual r

ainf

all (

mm

)

0

200

400

600

800

1995

1975

1955

1935

1915

1895

J F M A M J J A S O N D

Mea

n m

onth

ly r

ainf

all (

mm

) Future climate range

Historical

Future climate (best estimate)

0

20

40

60

80

100

Annual rainfall (1895–2006) spatially averaged across the region (based on SILO data) with low-frequency smoothed line shown to indicate longer-term variations.

Average (1895–2006) monthly rainfall averaged across the region and range (shaded) of potential changes in mean monthly rainfall due to climate change by 2030.

Average (1895–2006) annual rainfall (mm) distribution.

Runoff

Ann

ual r

unof

f (m

m)

0

20

40

60

80

100

120

1995

1975

1955

1935

1915

1895

J F M A M J J A S O N D

Mea

n m

onth

ly r

unof

f (m

m) Future climate range

Historical

Future climate (best estimate)

0.0

2.0

4.0

6.0

8.0

10.0

Annual runoff (1895–2006) spatially averaged across the region (based on daily modelling) with low-frequency smoothed line shown to indicate longer-term variations.

Average (1895–2006) monthly runoff averaged across the region and range (shaded) of potential changes in mean monthly runoff due to climate change by 2030.

Average (1895–2006) annual runoff (mm) distribution.

8 Water Avai labi l i ty in the Eastern Mount Lofty Ranges

Surface water

Current long-term average water availability across the Marne, Bremer, Angas, Finniss, Tookayerta and Currency catchments of EMLR is 120 GL/yr. Current average net diversions from farm dams (including net evaporation) across these catchments are around 11 GL/year – or about 9 percent of the average available water. The level of use varies however, across the six catchments considered, from about 5 to 18 percent.

A continuation of the climate of the last ten years (1997 to 2006) would reduce water availability by 26 percent – or 28 GL/year less water available on average. This would lead to a 6 percent reduction in net diversions from farm dams on average; however, the lowest 1-year diversions would decrease by 21 percent. These changes effectively increase the level of use to 11 percent for these climate conditions. The average period between spilling for farm dams across the region would increase by 33 percent.

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

Mar

ne

Brem

er

Ang

as

Finn

iss

Took

ayer

ta

Cur

renc

y

Ann

ual d

iver

sions

(G

L)

Future climate range

Future climate (best estimate)

Historical

Water availability Future climate

Current development Future development

Historical Recent Dry Best estimate

Wet Dry Best estimate

Wet

GL/y Percent change from Historical

Total inflows – -22% -51% -18% -3% -53% -20% -6%

Total surface water availability

120.4 -23% -52% -18% -3% -54% -21% -6%

Net diversions from farm dams

Lowest 1-year period 5.7 -21% -56% -12% 0% -55% -8% 5%

Lowest 3-year period 8.7 -10% -33% -7% 0% -30% 0% 8%

Lowest 5-year period 9.7 -8% -28% -7% 1% -25% 0% 9%

Average 10.7 -6% -19% -5% 1% -14% 3% 10%

Non-diverted water Percent

Non-diverted water as a percentage of total available water

91% 89% 85% 90% 91% 84% 88% 90%

Non-diverted share relative to historical non-diverted share

100% 69% 69% 93% 148% 69% 93% 148%

Annual water (GL)0 20 40 60 80 100 120 140

Recent

Historical

Future climate (wet)

Future climate (best estimate)

Future climate (dry)

Future climate/development (wet)

Future climate/development (best estimate)

Future climate/development (dry)

0 20 40 60 80 100 120 140

Diverted

Non-diverted

Recent

Historical

Future climate (wet)

Future climate (best estimate)

Future climate (dry)

Future climate/development (wet)

Future climate/development (best estimate)

Future climate/development (dry)

DivertedNon-diverted

Under the best estimate (median) 2030 climate an 18 percent reduction in water availability (about 22 GL/year) would be expected. However, because the level of water use is low, the reduction in average net diversions from farm dams would be only 5 percent, effectively increasing the level of surface water use to 10 percent.

The climate extremes for 2030 indicate:

• Under the wet extreme, a three percent decrease in water availability but a one percent increase in average net diversions from farm dams; and

• Under the dry extreme, a 52 percent decrease in water availability and a 19 percent reduction in average net diversions from farm dams. Thus in the worst future case water availability would be less than half the current average level and the level of surface water use would be 15 percent.

The combined impact of a potential 16 percent increase in total farm dam volume (an additional 3400 ML) and of a potential doubling of the area of commercial plantation forestry (an additional 2000 ha), both of which could occur by 2030, would be a 3 percent reduction in water availability in addition to the climate change impacts. These changes would actually increase net diversions considerably, as more farm dams provide more opportunity for water use. Future commercial plantation forestry growth would only be likely in the wetter Tookayerta and Currency catchments, for which the modelled reductions in runoff are 17 and 7 percent respectively. The level of surface water use with these developments for the best estimate 2030 climate would be 12 percent.

October 2007 9

Groundwater

Current groundwater extraction is a quarter of rainfall recharge in the EMLR groundwater management unit (GMU). Groundwater development is therefore low for this GMU which accounts for the majority of current groundwater use in the region. For the Marne Saunders GMU extraction is two-thirds of rainfall recharge, and while this is high, rainfall recharge for this GMU may be as low as 40 percent of total recharge due to (poorly quantified) flood recharge. Groundwater development is therefore probably moderate to high for the Marne Saunders GMU.

The main concern for groundwater at current extraction levels is increasing groundwater salinity in the Angas Bremer GMU and the Currency Creek region.

The total reduction in stream flow across the region due to current groundwater extraction is estimated to increase to 7 GL/year over the next 50 years; proportionally, these losses would be highest in Tookayerta Creek, with smaller impacts in the Angas, Bremer, Marne and Finniss rivers.

Long-term continuation of conditions similar to the last ten years would mean groundwater use would represent a greater fraction of rainfall recharge: 8 percent greater for the EMLR GMU and 12 percent greater for the Marne Saunders GMU.

The best estimate 2030 climate would have very little impact on the fraction of rainfall recharge that is extracted from groundwater. However, the uncertainty in 2030 climate estimate means groundwater extraction (at current levels) could represent between 22 and 39 percent of rainfall recharge for

* A water allocation plan for the EMLR GMU is currently being prepared. DWLBC recommended interim allocation; to be confirmed once environmental investigations are complete.

** A water allocation plan for the Marne Saunders is currently being prepared. Annual allocation volume is an interim value.

*** The confined aquifer receives minimal recharge from rainfall or stream flow.

Angas Bremer and Marne Saunders extraction values are for the 2004/05 water use year. The land use survey for the EMLR GMU was completed in 2002/03.

Code Priority ranking

Groundwater management unit

Current groundwater extraction

Total entitlement Long-term average extraction limit

Recharge from rainfall

Estimated future groundwater extraction

GL/y GL GL/y

S14 Low Eastern Mount Lofty Ranges

15.6 46* 46* 61.4 25.0

S18 Low Angas Bremer 1.2 6.5 6.5 *** 3.0

S23 Low Marne Saunders 2.0 4** 4** 3 3.0

Unincorporated area (east of Marne Saunders)

Not available Not licensed Not licensed

the EMLR GMU and between 59 and 101 percent for the Marne Saunders GMU.

Without intervention, groundwater extraction from all groundwater management units is likely to increase in the future. For the best estimates of future extraction (a 60 percent increase) and 2030 climate, extraction would be over 40 percent of rainfall recharge for the EMLR GMU and would exceed rainfall recharge for the Marne Saunders GMU. This increase in extraction would reduce streamflow by an about additional 4 GL/year – a total average impact of about 11 GL/year; the largest proportional impact would be on Tookayerta Creek. Current groundwater allocation planning may however, prevent these levels of extraction being realised.

The Eastern Mount Lofty Ranges region

Located at the lower end of the Murray-Darling River system in South Australia, the Eastern Mount Lofty Ranges (EMLR) region covers 4693 km2 or 0.4 percent of the Murray-Darling Basin, is home to around 52,000 people (2.6 percent of the Murray-Darling Basin) and includes the towns of Murray Bridge, Mount Barker and Strathalbyn. The eastern slopes of the Mount Lofty Ranges are steep and fall away to the broad Murray Plains and eventually to the Murray River and the lower lakes of Lake Alexandrina and Lake Albert. Rainfall is low on average and has remained relatively consistent over the past 111 years. The major water sources within the EMLR region are the Marne, Bremer, and Finniss Rivers, alluvial aquifers and private on-farm water storages. The predominant land use within the region is dryland grazing and cropping (see table below).

Broad land use in Eastern Mount Lofty Ranges in the year 2000.

Land use Area

percent ha

Dryland crops 27.2% 127,700

Dryland pasture 66.6% 311,100

Irrigated crops 2.8% 13,200

Cereals 2.9% 400

Horticulture 10.5% 1,400

Orchards 1.5% 200

Pasture and hay 40.2% 5,300

Vine fruits 44.9% 5,900

Native vegetation 1.0% 4,500

Plantation forests 0.5% 2,100

Urban 1.1% 5,000

Water 0.8% 3,800

Total 100.0% �67,�00

Source: BRS (2000).

Environment

Water planning has only recently commenced in the Eastern Mount Lofty Ranges region and at this time there are no formal environmental water allocations or environmental flow rules for the region. While environmental studies have commenced, at this time there are no agreed ecologically-relevant hydrologic indicators for assessing environmental change in the region. Therefore no quantitative environmental assessments have been undertaken for this region.

The region includes three wetlands of national importance (the Tookayerta & Finniss Catchments, the Marne River Mouth, and Ambersun – West Swamp) and the creeks and rivers of the region flow into the River Murray (an ’Icon Site’ under the Living Murray Initiative) and the internationally important Coorong and Lakes Alexandrina and Albert Ramsar wetland. These latter two environmental assets are considered for the Murray region report. Additionally, the Eastern Mount Lofty Ranges region contains the regionally important Fleurieu Swamps in the Currency Creek, Tookayerta Creek and Finniss River catchments.

The Fleurieu Swamps may have been affected by the considerable reductions in low flows in the Finniss River and Currency Creek caused by water resource development. They would also be likely to be affected by future flow changes caused by climate change or by any commercial plantation forestry development in Currency Creek.

> Marne River catchment, SA

Share of MDB runoff

0.5%

1.3%

Share of total MDBgroundwater use (excluding Great Artesian Basin)

10

October 2007 11

MARNE RIV

ERBREMERRIVER

FINNISS

RIVER

AN

GASRIVER

CURRENCY CREEK

REEDYCREEK

TO

OKAYERTA CREEK

Mannum

Nairne

Milang

Meadows

Springton

Strathalbyn

Mount Barker

Macclesfield

Murray Bridge

0 25Kilometres

River

TownMain Road

Legend

Other (see table)

Lakes

Native vegetationIrrigation

Z00

3065

8

Enquiries

More information about the project can be found at www.csiro.au/mdbsy. This information

includes the full terms of reference for the project, an overview of the project methods and

the project reports that have been released to-date, including the full report for the region.

About the project

The CSIRO Murray-Darling Sustainable Yields Project resulted from the Summit on the Southern Murray-Darling Basin, convened by the Prime Minister on 7 November 2006. The project is providing governments with a robust, Basin-wide estimate of water availability on an individual catchment and aquifer basis taking into account climate change and other risks. The project will report progressively to early 2008. The project will be the most comprehensive Basin-wide assessment of water availability undertaken to-date. For the first time:

• daily rainfall-runoff modelling has been undertaken at high spatial resolution for a range of climate change and development scenarios in a consistent manner for the entire Basin;

• the hydrologic sub-catchments required for detailed modelling have been precisely defined across the entire Basin;

• the hydrologic implications for water users and the environment by 2030 of the latest Intergovernmental Panel on Climate Change climate projections, the likely increases in farm dams and commercial forestry plantations and the expected increases in groundwater extraction have been assessed in detail;

• the assessments have employed all existing river system and groundwater models as well as new models developed within the project;

• the modelling has included full consideration of the downstream implications of upstream changes between multiple models and between different States, and quantification of the volumes of surface-groundwater exchange; and

• detailed analyses of monthly water balances for the last 10 to 20 years have been undertaken using available streamflow and diversion data together with additional modelling including estimates of wetland evapotranspiration and irrigation water use based on remote sensing imagery. These analyses provide an independent cross-check on the performance of river system models.

The assessments reported here have been reviewed by a project Steering Committee and a Technical Reference Panel both with representation from Commonwealth and State governments and the Murray-Darling Basin Commission.

This document is printed on recycled paper.