South-West Western Australia Sustainable Yields Project Don - PowerPoint PPT Presentation

South-West Western Australia Sustainable Yields Project Don McFarlane Project Leader

Acknowledgements • DEWHA – funding and policy guidance • Department of Water – data, models, researchers, report review • Water Corporation – data, report review • Department of Agriculture and Food WA – soils data • Bureau of Meteorology – climate data, surface water modelling • Queensland Department of Environment and Resource Management – SILO data • Contracts and consultancies • URS – Peel Harvey groundwater model • CyMod Systems Pty Ltd – groundwater model calibration • Resource Economics Unit – demand estimation • Geographic Information Analysis – model data preparation • Jim Davies and Associates – yield and demand analyses • External reviewers: Peter Davies (University of Tasmania); Andy Pitman (University of New South Wales); Tony Jakeman (Australian National University): Don Armstrong (Lisdon Associates) and Murray Peel (University of Melbourne) CSIRO South-West Western Australia Sustainable Yields Project – Overview

Broad terms of reference • Estimate the current and 2030 yield of water for catchments and aquifers in the south-west of WA considering climate change and development (plantations, farm dams, groundwater abstraction) • Compare the estimated current and future water yields to those needed to meet the current levels of extractive use, future demands and environmental needs CSIRO South-West Western Australia Sustainable Yields Project – Overview

Publications Main reports Executive summaries Factsheets Web: www.csiro.au/partnerships/SWSY.html CSIRO South-West Western Australia Sustainable Yields Project – Overview

Project context Environmental impacts of This Project alternate allocation regimes Water resource Assessments Socio-economic impacts of planning, of current and alternate allocation regimes management future water and yields and investment demands Stakeholder and community consultation • The project does not attempt to set new allocation limits • The project is regional and doesn’t address local issues • The results are scenarios based on assumptions about the future climate, landuses, abstraction levels and demands CSIRO South-West Western Australia Sustainable Yields Project – Overview

Sustainable Yields Projects – 2007 to 2009 Murray-Darling Basin Northern Australia South-West Western Australia Tasmania CSIRO South-West Western Australia Sustainable Yields Project – Overview

Location of the project area • All fresh, marginal and brackish surface water catchments between Gingin Brook and the Hay River • All aquifers within the Perth and Collie basins, plus the western Bremer Basin • Area = 62,500 km 2 CSIRO South-West Western Australia Sustainable Yields Project – Overview

Project area topography • Short streams that arise in the Darling Ranges are fresh • Darling Fault separates Perth Basin from Darling Plateau • Coastal plains are flat and low lying – Swan Coastal Plain; Scott Costal Plain; South Coast • Perth Basin Plateaux are higher in elevation CSIRO South-West Western Australia Sustainable Yields Project – Overview

Land cover • Surface water catchments are mainly forested • About 60% of the Perth Basin is cleared about 56% of this being under dryland agriculture Gnangara • The uncleared areas Mound include coastal areas north of Perth, the Gnangara Mound and the Blackwood Plateau Blackwood Plateau CSIRO South-West Western Australia Sustainable Yields Project – Overview

Climate – annual averages, 1975 to 2007 Potential Rainfall - APET evapotranspiration CSIRO South-West Western Australia Sustainable Yields Project – Overview

South-west WA has had reduced rainfall since 1975 May – July August October – 600 500 -18% Total rainfall (mm) 400 300 200 -8% 100 0 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 The 1975 to 2007 period is the baseline for all subsequent comparisons CSIRO South-West Western Australia Sustainable Yields Project – Overview

Scenarios • The ‘historical climate’ assumed that the climate of the last 33 years (1975 to 2007) would continue. This was used as a base case for comparison of other climate scenarios • The ‘recent climate’ assumed that the climate of the last 11 years (1997 to 2007) would continue • The ‘future climate’ used 15 GCMs with 3 GHG emission levels which would result in 0.7, 1.0 and 1.3 o C of warming by 2030 = 45 possible climates. They are reported as • wet future climate • median future climate, and • dry future climate • Current levels of abstraction and land use were assumed to continue for all scenarios above • The ‘future climate and development’ assumed a median future climate and full groundwater abstraction, new plantations and farm dams (where important) CSIRO South-West Western Australia Sustainable Yields Project – Overview

Annual rainfall and inflow into Perth dams Runoff is affected by climate and other factors 2500 Annual Rainfall at Jarrahdale (mm) Yearly rainfall at Jarrahdale Annual Total 1911 to 1974 (1251mm) 2000 1975 to 2009 (1047mm) 16% reduction 1997 to 2009 (1003mm) 1500 1000 500 0 1000 1911 1914 1917 1920 1923 1926 1929 1932 1935 1938 1941 1944 1947 1950 1953 1956 1959 1962 1965 1968 1971 1974 1977 1980 1983 1986 1989 1992 1995 1998 2001 2004 2007 Yearly streamflow for major surface water sources - IWSS Annual Total 900 Annual Inflow to Perth Dams (GL) 1911 to 1974 (338GL) 800 700 1975 to 2009 (151GL) 600 1997 to 2009 (107GL) 500 55% Historical 400 reduction 300 200 100 0 1911 1914 1917 1920 1923 1926 1929 1932 1935 1938 1941 1944 1947 1950 1953 1956 1959 1962 1965 1968 1971 1974 1977 1980 1983 1986 1989 1992 1995 1998 2001 2004 2007 Recent Note: A year is taken as May to April (Data courtesy of the Water Corporation) CSIRO South-West Western Australia Sustainable Yields Project – Overview

Annual rainfalls have been even drier since 1997 1997 to 2007 rainfall compared with 1975 to 1996 rainfall CSIRO South-West Western Australia Sustainable Yields Project – Overview

14 of 15 GCMs project it will get drier Change in annual rainfall • Median future climate -7% • Wet extreme future -1% climate (90 percentile) • Dry extreme future -14% climate (10 percentile) Mid warming High warming Low warming CSIRO South-West Western Australia Sustainable Yields Project – Overview

Subsequent talks • Surface water Richie Silberstein • Groundwater Riasat Ali • Environment Olga Barron • Water yields and demands Don McFarlane Short period for questions after each talk • Meet the Team – informal session over afternoon tea CSIRO South-West Western Australia Sustainable Yields Project – Overview

Rainfall and runoff in south-west Western Australia Richard Silberstein Surface Water Team Leader

Objectives – Surface Water • Project future quantity, duration and seasonal distribution of runoff (mm) and streamflow (ML) for conditions in 2030 • under specified climate scenarios, and • with future plantations and farm dams • These results were used in estimating divertible yields and impacts on ecosystems CSIRO South-West Western Australia Sustainable Yields Project – Surface Water

Geographic scope • 13 surface water basins covering 39,000 km 2 CSIRO South-West Western Australia Sustainable Yields Project – Surface Water

Rainfall runoff modelling • Runoff simulated using five simple conceptual models • Sacramento • IHACRES • SIMHYD • AWBM • SMARG • One catchment model • LUCICAT (in about half the catchments) • The calibrated model output was compared with observed data and an average of runoff from Sacramento and IHACRES was the best CSIRO South-West Western Australia Sustainable Yields Project – Surface Water

Catchment representation Collie Basin • 0.05 o x 0.05 o grid (~ 5 x 5 km) • Each cell mapped into a catchment • Flow accumulated for 204 defined streamflow reporting nodes CSIRO South-West Western Australia Sustainable Yields Project – Surface Water

106 Calibration catchments Criteria for use in calibration: • Catchments larger than 10 km 2 • At least 10 years of available streamflow data between 1975 and 2007 (average record length 27 years) CSIRO South-West Western Australia Sustainable Yields Project – Surface Water

Calibration results – examples 500 500 Harvey River - Dingo Road Observed NSE = 0.82 Annual runoff (mm) . Modelled annual runoff (mm) 400 400 Modelled 300 300 200 200 100 100 0 0 400 400 Scott River - Brennan's Ford NSE = 0.87 Observed Annual runoff (mm) . Modelled annual runoff (mm) Modelled 300 300 200 200 100 100 0 0 0 100 200 300 400 1975 1985 1995 2005 Observed annual runoff (mm) Average model efficiency = 0.84, >0.8 in 80% of catchments CSIRO South-West Western Australia Sustainable Yields Project – Surface Water