Surface water yields in south-west Western Australia

Transcription

1 Surface water yields in south-west Western Australia Summary of a report to the Australian Government from the CSIRO South-West Western Australia Sustainable Yields Project December 2009 Summary 1

2 About the project Scenarios assessed In 2007 and 2008, CSIRO produced a series of reports examining the likely water yield of surface water and groundwater catchments in the Murray-Darling Basin as a result of future climate changes and possible land management changes such as afforestation and farm dams. On 26 March 2008, the Council of Australian Governments (COAG) agreed to expand the CSIRO assessments of sustainable yields to northern Australia, Tasmania and south-west Western Australia (SWWA). For the first time, Australia will have a comprehensive scientific assessment of water yields in all major water systems across the country, which allows a consistent analytical framework for water policy decisions across the nation. The CSIRO South-West Western Australia Sustainable Yields Project has estimated the likely water yields of all major fresh, marginal and brackish surface water and groundwater systems between Geraldton and Albany under the same climate and development scenarios as used in the other three projects, except that the historical climate data were of shorter length (the 33-year period from 1975 to 2007). The project has also estimated future water demands and compared these with likely future yields from all water resources under all scenarios. For the first time: A consistent set of future climate inputs have been compiled for use in surface water and groundwater models over the main water catchments in SWWA. Daily rainfall-runoff modelling has been undertaken at high spatial resolution under climate and development scenarios in a consistent approach across all major water catchments. Runoff projections under the future climate are available for every major stream with projected inflows to all major dams across the project area. The project has reported the results in three main reports titled: Surface water yields in south-west Western Australia Groundwater yields in south-west Western Australia Water yields and demands in south-west Western Australia. In this report runoff projections under the future climate are presented for every major stream and projected inflows to all major dams across the project area are reported. The groundwater report presents modelled groundwater yields across the project area. The water yields and demands report presents estimates of future water demands by major water user groups and compares these with possible future surface water and groundwater yields to identify areas where water shortages may occur and where there may be impacts on water dependent ecosystems. Companion technical reports provide more detail on the methods and results. The assessments reported here have been reviewed by expert staff within the Department of Water Western Australia, a Technical Reference Panel, external reviewers, and a Steering Committee with representatives from the Australian and Western Australian governments. The assessments of current and future water availability were made by considering a range of climate and development scenarios. The historical climate scenario was based on the climate of the historical past (1975 to 2007). This period was chosen because the climate in SWWA changed in about 1975 resulting in substantially reduced streamflows. This scenario was used to assess water yields should the climate in the future prove to be similar to that of the historical past. This scenario was used as the baseline against which other scenarios were compared. Current levels of surface water and groundwater development were used. The recent climate scenario was based on the climate of the recent past (1997 to 2007). This scenario was used to assess water yields should the climate in the future prove to be similar to that of the recent past. Current levels of surface water and groundwater development were used. The future climate scenario used 15 global climate models with three estimates of temperature changes (due to global warming) to provide a spectrum of possible ~2030 climates. From this spectrum three were selected for reporting, representing a wet extreme, median and dry extreme future climate. Current levels of surface water and groundwater development were used. The future climate with future development scenario used the same climate time series as the median future climate scenario, but future levels of development were used (~2030 projections of commercial forestry plantations, farm dams and likely future irrigation developments). Acknowledgments The South-West Western Australia Sustainable Yields Project was undertaken by CSIRO under the direction of the Australian Government Department of the Environment, Water, Heritage and the Arts. Important aspects of the work were undertaken by the Department of Water Western Australia. The Water Corporation and the Western Australia Department of Agriculture and Food provided expert advice and data. A contract to develop a groundwater model for part of the region was undertaken by URS Australia Pty Ltd. Additional technical input was provided by CyMod Systems, Jim Davies and Associates, Resource Economics Unit and Geographic Information Analysis. Valuable feedback was received during the review process from Tony Jakeman, Andy Pitman, Don Armstrong, Peter Davies and Murray Peel. 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 the data or software including any material derived from that data or software. Data must not be used for direct marketing or be used in breach of the privacy laws. Organisations include: Department of Water Western Australia, Bureau of Meteorology, Water Corporation and the Western Australia Department of Agriculture and Food. 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 are assumed to be correct as received from the organisations. CSIRO 2009 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. 2 Surface water yields in south-west Western Australia >> > Cover: The Warren River near Pemberton, WA (CSIRO)

3 Overview of the project area The geographic extent of the South-West Western Australia Sustainable Yields Project includes all fresh, marginal and brackish surface water basins from Gingin Brook, north of Perth, to Albany; and groundwater resources in the Perth and Collie basins, and the west Bremer Basin near Albany in the south-east (Figure 1). This area covers all current and anticipated future water resources in SWWA suitable for irrigation, domestic water supplies and industries that require low salinity water. Inland water supplies are either limited or too saline for these uses. As a result these inland areas are supplied with water from the project area. The project area covers about 62,500 km 2 with over 1.9 million people or 89 percent of the population of Western Australia. It is concentrated over the highest rainfall part of the south-west of the state and includes all of the state s irrigation areas with the exception of the Gascoyne (Carnarvon) and the Ord (Kimberley). The main land uses in the project area are native vegetation including logged state forest (52 percent) and dryland agriculture (40 percent), with minor areas of urban (2 percent), forestry plantations (3 percent) and irrigation (2 percent). The main dryland agriculture is grazing for wool and meat production while the main irrigation is for vegetables, fruit, vines, grazing for beef and dairy cattle, and fodder. SWWA is renowned for its high level of biodiversity and unique flora and fauna as a result of a long stable landform and climate and the isolation of the region from other parts of the world. The assessment of surface water yield has been applied only to that part of the project area (34,942 km 2 ) that includes substantial surface water resources. This area has been divided into three geographic regions (Figure 2): a northern region, including the Gingin to Murray basins and tributaries to the lower reaches of rivers in the Avon and Swan Coastal basins; a central region, including the Harvey, Collie and Preston basins; and a southern region, including the south coast from the Busselton Coast to the Denmark basins. The northern region includes the Water Corporation s Integrated Water Supply Scheme (IWSS) reservoirs. The central region contains surface water irrigation schemes, some water from which has been traded to now supply the IWSS. The southern region includes large areas of nature reserves and managed forest, horticulture, dryland agriculture and plantations. The Avon, Murray, Blackwood and Frankland rivers are not included because they are too salty for normal consumptive use. The project collated historical climate and streamflow data and applied rainfall-runoff models to estimate the surface water resources in the thirteen surface water basins of the project area for 33 years under climate and development scenarios. The projected streamflows were analysed for flow characteristics including variability and frequency distribution. The implications of these projections on future surface water yields to meet demand and environmental requirements are assessed in a companion report. A creek running through the northern >> jarrah forest, WA (CSIRO) >>Figure 1. Groundwater resources and surface water resources in the project area December

4 Key findings Under all future climate scenarios, rainfall declines relative to the historical and recent climate. Under the median future climate, rainfall declines by an average of 8 percent and runoff by 25 percent relative to the historical climate. The declines in runoff are proportionally greater in the northern surface water region but greater volumetrically in the central and southern regions. Averaged across all surface water basins, the decline in runoff under the median future climate results in a decline in mean annual streamflow of over 800 gigalitres (GL), and a decline of over 1400 GL under the dry extreme future climate. This is in addition to the decline in runoff that has occurred since the mid-1970s. Under the historical climate, the probability of rainfall exceeding 900 mm and runoff exceeding 130 mm in any one year is 20 percent. This probability reduces to 5 percent under the median future climate and to less than 3 percent under the dry extreme future climate. Under the future climate, runoff variability increases substantially and all regions show an increased number of days of low or zero flows. >>Figure 2. Mean annual rainfall, areal potential evapotranspiration and rainfall deficit (rainfall minus areal potential evapotranspiration) across the surface water modelling area under the historical climate >>Sampling the first flows in a tributary of the Canning River, WA (CSIRO) 4 Surface water yields in south-west Western Australia

5 Projected growth in plantations and farm dams is expected to have minimal impact on streamflows relative to the effect of the future climate. In about half of catchments runoff has reduced over the recent past (1997 to 2007) even with similar rainfall. This indicates that rainfall-runoff mechanisms may be changing and future model projections may over estimate streamflows. Climate >>Mist over the waters of Wellington Reservoir near Collie, WA (CSIRO) The rainfall in SWWA is highly winter-dominated with 80 percent of rainfall occurring from May to October and 70 percent of areal potential evapotranspiration (APET) occurring from October to March. On an annual basis the total APET exceeds the total rainfall (Figure 2) except in a small area in the southern end of the Shannon basin on the south coast. During the recent past (1997 to 2007), mean annual rainfall across the project area has been slightly lower than during the 33-year historical past (1975 to 2007) (Figure 3). However, this decline has not been uniformly distributed, with a greater decline in the northern and central regions. In some surface water basins in the southern region, rainfall during the recent past has been slightly higher than during the historical past. >>Figure 3. Mean annual rainfall under the historical climate, and changes in rainfall under the recent climate and median future climate relative to the historical climate December

6 Rainfall-runoff model calibration Runoff was simulated in a total of 204 catchments, 106 of which were gauged and used in model calibration with measured streamflow data from the historical period 1975 to The calibrated catchments are distributed over the project area and account for more than 67 percent of the total area and flow. Although observed rainfall and calculated APET data were available for the full 33 years, the streamflow data period varied for individual gauging stations, ranging from 10 years upwards. The calibration catchments had a median area of 149 km 2 and mean annual runoff ranged from 5 to 348 mm. Six rainfallrunoff models were assessed. The mean of the daily modelled flow from the best combination of these individual models was adopted as the model for scenario analysis. In about half of the calibration catchments runoff has reduced over the recent past (1997 to 2007), even with similar rainfall. In these catchments the models over estimate runoff in the last 5 to 10 years of record, and under estimate in the 10 years prior to that. This is interpreted as an indication of the changing moisture storage and declining groundwater contributions to streamflow in these catchments resulting from the recent drying climate and may also be influenced by changing rainfall characteristics and forest condition. The implication is that the modelling may be over estimating projected streamflows. Rainfall and runoff projections Under a continuation of the recent climate, all three regions have lower rainfall and runoff than under the historical climate. Under the recent climate, rainfall peaks in August, a month later than under the historical climate, and produces substantially lower total runoff (Figure 4). Decline in rainfall under the recent climate is about 4 percent in the northern and central regions but runoff declines by an average of 12 percent between them (Table 1). The later onset of winter rainfall may be a contributing factor to the decline in streamflow during the recent past, as Mean monthly rainfall (mm) J F M A M J J A S O N D catchment soils are drier and a greater amount of rain is required before runoff commences. Although there is a large spread in responses under the 45 future climate scenarios (Figure 5), the results indicate that the projected future climate has a major impact on both rainfall and runoff. Relative to the historical climate, rainfall is projected to decline by more than 10 percent in 12 of the 45 future climate projections, and runoff is projected to decline by more than 30 percent in 15 Mean monthly runoff (mm) Future range Median future Recent Historical 0 J F M A M J J A S O N D of the 45 future climate projections. The future projections show a larger range in the winter rainfall than the summer rainfall which translates into a large range in projected winter runoff. Across the surface water modelling area the projected runoff under the median future climate is less than that under both the historical and recent climate (Figure 6). Projected mean annual runoff under the future climate ranges from a 10 to 42 percent reduction under the wet extreme and dry extreme future climate respectively. >>Figure 4. Monthly rainfall and runoff averaged across the surface water basins under all climate scenarios inmcm ncar_pcm iap cccma_t63 ipsl miroc cnrm cccma_t47 ncar_ccsm mri mpi gfdl giss_aom miub csiro Wet extreme Median future Dry extreme -25% -20% -15% -10% -5% 0% Change in rainfall from historical inmcm ncar_pcm iap cccma_t63 ipsl miroc cnrm cccma_t47 ncar_ccsm mri mpi gfdl csiro giss_aom miub -50% -40% -30% -20% -10% 0% Change in runoff from historical >>Figure 5. Percent change in rainfall and runoff averaged across the surface water basins relative to the historical climate for each of the three global warming scenarios and all 15 global climate models (named on vertical axis). The left end of the bars indicates the high warming scenario; the right end, the low warming scenario; and the change in colour, the median warming scenario. The wet extreme, median and dry extreme future climate scenarios (selected on the basis of runoff) are indicated 6 Surface water yields in south-west Western Australia

7 >>Table 1. Mean annual rainfall and runoff statistics Scenario Mean annual rainfall Mean annual runoff Rainfall minus runoff Runoff coefficient* mm >>Figure 6. Spatial distribution of mean annual runoff across the surface water modelling area under the historical, recent and median future climate; and change relative to the historical climate percent change relative to historical climate mm percent change relative to historical climate mm percent change relative to historical climate percent Streamflow volume Surface water modelling area Historical climate % 3411 Recent climate 818-2% 91-7% 728-2% 11% 3172 Wet extreme future climate 819-2% 88-10% 731-1% 11% 3068 Median future climate 769-8% 74-25% 695-6% 10% 2575 Dry extreme future climate % 57-42% % 8% 1986 Northern (Gingin to Murray) region Historical climate % 457 Recent climate 738-4% 40-13% 698-3% 5% 396 Wet extreme future climate 754-1% 43-8% 711-1% 6% 422 Median future climate % 33-30% 659-8% 5% 320 Dry extreme future climate % 22-53% % 3% 217 Central (Harvey to Preston) region Historical climate % 742 Recent climate 783-4% % 675-3% 14% 663 Wet extreme future climate 803-2% 112-7% 691-1% 14% 689 Median future climate 742-9% 93-23% 649-7% 12% 569 Dry extreme future climate % 72-40% % 10% 443 Southern (Busselton Coast to Denmark) region Historical climate % 2212 Recent climate 871-1% 111-4% 760-1% 13% 2113 Wet extreme future climate 858-3% % 755-1% 12% 1957 Median future climate 818-7% 89-24% 729-5% 11% 1686 Dry extreme future climate % 70-40% 693-9% 9% 1326 Note that all numbers have been rounded to nearest mm. * The fraction of rainfall that becomes runoff. GL December

8 Under the median future climate, rainfall (averaged across the surface water modelling area) declines by 8 percent and runoff by 25 percent relative to the historical climate. Relative to the recent climate, rainfall and runoff decline by 6 percent and 19 percent respectively. Each millimetre of rainfall or runoff is equivalent to 1 megalitre (ML) per square kilometre in streamflow. Across the whole project area, the projected streamflows under the wet extreme, median and dry extreme future climate are 343, 837 and 1426 GL/ year, respectively, less than under the historical climate, and are 104, 597 and 1186 GL/year, respectively, less than under the recent climate. Rainfall and runoff variability Under the future climate, runoff variability increases substantially so that in addition to the lower flow across the project area there is reduced reliability. Under the historical climate, annual rainfall averaged across the surface water modelling area exceeds 900 mm, and runoff exceeds 130 mm, in about 1 in 5 years (Figure 7). Under the median future climate, these frequencies are projected to decline to about 1 in 20 years. The variability in runoff is much greater than in rainfall. The mean annual rainfall and runoff over the surface water modelling area under the historical climate are 837 mm and 98 mm, respectively, and the 10 th, 50 th and 90 th percentile runoff values are 55, 95 and 151 mm respectively (Figure 7). With the drier conditions under these scenarios, the coefficient of variation of annual flow increases. This has implications for reliability of supply and security of environmental flows in the areas particularly affected, notably the more inland parts of the surface water basins. The highest mean annual rainfall across the project area under the historical climate is 1230 mm which reduces to 1150 mm under the median future climate (Figure 8). Under the historical climate, 1000 mm rainfall is received by over one-fifth of the surface water modelling area which generates over 160 mm of runoff. This reduces to about one-tenth of the area under the median future climate (Figure 8). Under the future climate, all regions show an increased number of days of low or zero flows. The impact on aquatic systems of this level of flow depends on the changed distribution of low flow days projected under future climate scenarios. Annual rainfall (mm) Future range Median future Recent Historical Percent time annual rainfall is exceeded Annual runoff (mm) Percent time annual runoff is exceeded >>Figure 7. Temporal distribution of annual rainfall and runoff averaged across the surface water basins under all climate scenarios Annual Rainfall (mm) Annual Runoff (mm) Future range Median future Recent Historical >>Figure 8. Spatial distribution of mean annual rainfall and runoff across the surface water basins under all climate scenarios Percent of area annual rainfall is exceeded Percent of area annual runoff is exceeded 8 Surface water yields in south-west Western Australia

9 Regional results Rainfall is highest in the southern region, but runoff and the fraction of rainfall that becomes runoff (the runoff coefficient) are highest in the central region. The rainfall, runoff and the runoff coefficient are lowest in the northern region. While all regions are projected to have similar percentage declines in mean annual rainfall under the median future climate relative to the historical climate (equivalent to a reduction of about 70 mm), the northern region has the largest proportional reduction in runoff of about 30 percent (13 mm). However, in quantity this is half of the reduction in runoff projected under this climate in the central and southern regions. Projected declines in mean annual runoff in the northern region range from 8 to 53 percent under the wet and dry extreme future climate respectively. Under the dry extreme future climate the reduction in runoff equates to reductions in mean annual streamflows of 241, 299 and 886 GL in the northern, central and southern regions respectively. Under the recent climate, the percentage decline in runoff is greatest in the northern and central regions and is projected to decline further under the median future climate (Figure 9). The main IWSS dams are located in the northern region where there has already been a decline in inflows of over 50 percent from pre- >>The Harvey Reservoir at near capacity, WA (CSIRO) 1975 levels. If the median or dry extreme future results eventuate, the runoff into IWSS and irrigation scheme dams will be even more severely impacted than they are at present, as these are all in the Swan Coastal, Murray, Harvey and Collie basins. The reductions in runoff in the southern catchments will impact self-supply irrigators and streams in national parks and nature reserves. The Harvey basin has the highest runoff coefficient in the SWWA of 22 percent under the historical climate, reducing to 16 percent under the dry extreme future climate. Under the median future climate in the central region, there is a 9 percent reduction in mean annual rainfall and a corresponding 23 percent reduction in mean annual runoff relative to the historical climate. Projected decline in mean annual runoff ranges from 7 to 40 percent under the wet and dry extreme future climate respectively. The decline in runoff in the recent past, relative to the historical past, is only 4 percent in the southern region. However, under the median future climate, projected decline in runoff is similar (around 25 percent) in all modelled surface water basins and the decline relative to the recent climate is greatest (20 percent) in the southern region. Under all scenarios the mean annual rainfall in the Shannon basin is the highest of all the basins in the project area. Under all future climate scenarios with projected farm dam development, mean annual runoff is projected to decrease by an additional 1 percent due to increases in farm dam storage capacity. While there are some differences in the mean monthly runoff with farm dams under this future development scenario, the results are always well within the range of results under the future climate scenario with current development. There is unlikely to be a major impact of projected plantation development on surface water resources in the project area. Northern region Central region Southern region Change in mean annual runoff (%) Gingin Swan Coastal Murray Harvey Collie Preston Busselton Coast Lower Blackwood Donnelly Recent climate Median future climate Warren Shannon Kent Denmark >>Figure 9. Percentage decline in runoff in all surface water basins under the recent and the median future climate relative to the historical climate December

10 Regional results (cont.) Over the historical period there have been decreases in groundwater levels in Darling Range catchments of up to 10 m. This is likely to have reduced both the baseflow and areas of saturation which generate runoff in an area which traditionally had high groundwater levels in stream zones. Runoff generation may also have been affected by bauxite mining, and by rehabilitation and revegetation of the sites after mining. Reductions in rainfall intensity, and simply lower rainfall, may also result in reduced runoff coefficients. Therefore there may be a change in the rainfall-runoff processes in these catchments making the estimation of future water yields into reservoirs more difficult. The modelling of calibration catchments indicated that in many areas, there was a systematic trend in model errors relative to observed flows, with under estimation early in the series and over estimation later in the series, indicating a systematic change in catchment response to rainfall. Put simply, the same amount of rainfall now results in less runoff than it did in the past and this trend appears to be continuing. >>Dairy cattle beside an irrigation channel in the Harvey basin (CSIRO) Steps to improve our understanding Should it be necessary the project results could be improved by using dynamical and more sophisticated statistical downscaling of global climate model outputs to provide more realistic projections of future climate. In particular, the effect of changes in rainfall intensity and seasonal distribution on runoff could be quantified. This project used all 15 global climate models used in the Intergovernmental Panel on Climate Change Fourth Assessment that were able to estimate daily climate data. Some of these models do not reproduce the decline in rainfall that has affected SWWA in the past 33 years and therefore they may not be good predictors of future climates. There could be further assessment of which models perform best in SWWA and which meteorological variables most affect catchment runoff. >>Clouds over coastal plains south of Perth, WA (CSIRO) There is a clear need to explore the adaptation of vegetation to changing climate: how fast it adapts and whether the relationships between rainfall, APET and runoff are modified in the process. The projections may be significantly improved by incorporation of vegetation dynamics in future modelling. Additionally, the models used in this project would be improved if vegetation management could be simulated. This is particularly significant in the light of other studies that have found vegetation management to be the best lever to manipulate catchment yields and groundwater recharge. The models could also be improved with a process that simulates long-term groundwater behaviour that appears to impact on runoff generation and streamflow. 10 Surface water yields in south-west Western Australia

11 Limitations This project provides estimates of catchment-scale runoff using lumped conceptual rainfall-runoff models and large hydrological datasets, some of which were obtained from large-scale climate models. The methods used in this project are suitable for regional estimates but to assess local impacts on runoff and streamflows, finer scale modelling and analysis would be required. There are a number of assumptions that may result in errors in estimated runoff. These include assuming (i) the future input climate data have properties similar to the past data, e.g. number of rain days per season does not change; (ii) the interpolated data obtained from SILO DataDrill ( retain the temporal and spatial properties of the true climate; and (iii) land use changes or vegetation adaptation to a hotter and drier climate are minor. Changes in leaf cover occur in forested catchments caused by logging, fire, disease and other factors. It is possible that some vegetation components will adapt to climate change, affecting rainfall-runoff relationships. The rainfall-runoff models used in this project do not explicitly model groundwater, which is known to be declining in the catchments in the project area. Future runoff projections may be unreliable if the prolonged dry climate results in unusually low groundwater levels causing a disconnection between groundwater and streams and areas close to streambeds, a major source of runoff generation. Both of the latter cases imply that catchment systems may not be in a stable state which is implicit in the calibrations that were used. >>Above: Stream gauging station in the northern jarrah forest, WA (CSIRO). Below: Mundaring Weir is a major water supply for country users in south-west WA (CSIRO) December

12 Where to from here This report presents the results of an intensive and comprehensive surface water modelling project to assess the impacts of climate change and development on runoff for the high rainfall catchments in SWWA. The implications are that under all likely future climate projections, runoff and streamflow to reservoirs will be reduced in the future relative to the levels during the historical past (1975 to 2007), and relative to levels during the recent past (1997 to 2007). The estimates of proportional reduction can be used to guide future water source planning, as even with uncertainties over actual quantities of flow, the projections of proportional changes are considered reliable. As such, any agency interested in examining future water supply scenarios can find relevant data in this report to guide their analysis. The results presented in the report are necessarily of a general nature, because of the extent of the project area. However, the results are available in sufficient detail for each surface water basin with fresh, marginal and brackish water in the project area. Combined with projections of future demands in specific regions, these results can be used to assess where shortfalls in future water supplies may occur. In addition, the companion technical reports and project database include results from all catchments ranging in size from 10 to 4000 km 2. These results provide a readily available dataset to begin detailed investigations of surface water issues in these catchments. The modelling undertaken has limitations discussed above, but is robust enough to highlight locations that may be targeted for more intensive analysis. Additionally, consequences for the environment of future streamflow trends can be assessed for each of the catchments analysed. The methods developed can be applied to specific locations to develop regional synopses of surface water trends, be they summer low flows, winter peak flows or flow frequency distributions. While the demands of the project required some compromises in the specific modelling approaches adopted, the methodology used could be readily adapted for similar analyses with improved models, with more refined scenarios or at a finer scale. For further information: CSIRO Water for a Healthy Country Flagship Project Leader Dr Don McFarlane Phone: (08) don.mcfarlane@csiro.au Web: MCK218 Dec 2009 SWSY_SurfaceWater_Summary.indd Web: Enquiries More information about the project can be found at 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. More information on the Australian Government s Water for the Future plan can be found at Printed on recycled paper