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Effect of Climate Change on South West WA Hydrology

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Presentation by Don McFarlane, CSIRO on the effect of climate change on hydrology in the South West of Western Australia

Presentation by Don McFarlane, CSIRO on the effect of climate change on hydrology in the South West of Western Australia

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  • 1. The effect of climate changeon South West WA hydrologyDon McFarlaneResearch Manager
  • 2. Structure of the talk1. Recent and projected climate change in South West WA i. Rainfall amount and intensity ii. Temperature2. Wheatbelt i. Groundwater levels and dryland salinity ii. Streamflows and flooding3. Darling Range i. Groundwater levels ii. Surface water yields4. Perth Basin i. Groundwater levels ii. Surface water – groundwater interactions5. Conclusions The effect of climate change on South West WA hydrology
  • 3. Location of the areas discussed Perth Basin Darling Range streams Wheatbelt Blue + pink = South WestSustainable Yield project area The effect of climate change on South West WA hydrology
  • 4. South west WA annual rainfall has fallen since 1970 Bureau of Meteorology 2010>60 mm>120 mm
  • 5. South-west WA has had reduced rainfall since1975 May – July August – October 600 500 -18%Total rainfall (mm) 400 300 200 100 -8% 0 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 Change may have started in about 1965 and stabilised by 1975The effect of climate change on South West WA hydrology
  • 6. SWWA winter extreme rainfall has decreased since 1965 Li et al. 2005 90Rainfall (mm) (on log scale) 80 70 60 50 40 Year 1930-1965 Year 1966-2001 30 1 10 100 1000 Return period (years) (on log scale) The effect of climate change on South West WA hydrology
  • 7. Annual rainfalls have been even drier since 1997 CSIRO 2009 1997 to 2007 rainfall compared with 1975 to 1996 rainfallThe effect of climate change on South West WA hydrology
  • 8. 14 of 15 GCMs project it will get drier CSIRO 2009 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 warmingThe effect of climate change on South West WA hydrology
  • 9. Temperatures have risen which increases potential evapotranspiration and reduces soil water Bureau of Meteorology 2010Up to 0.60CUp to 0.80C Up to 0.40C
  • 10. Projected changes intemperature by 2030CSIRO and BoM 2007
  • 11. Groundwater levels and salinity in the WheatbeltThe effect of climate change on South West WA hydrology
  • 12. Slow fall in saline valley floorYilgarn Examples ofCraton falling groundwater levels 5m fall since 2000 where WT is deeper Speed (2008) 1m fall since 2000PerthBasin
  • 13. Speed (2008) Rising or stable trends prior to 2000Declining trends irrespective of geology, WTdepth or land use
  • 14. Before 2000 most groundwater levels were rising in northern and central regions. Now most are falling Based on data in George et al. 2008 80 Pre 2000 Rising Pre 2000 Falling 70 Post 2000 Rising Post 200 Falling 60Percent of bores 50 40 30 20 10 0 Northern Central South West South Coast (W) South Coast (E) Region The effect of climate change on South West WA hydrology
  • 15. Land Monitor - dryland salinity spread 1989 to 1996 and hazard Yellow = 1989 Red = 1996 Blue = salt hazard
  • 16. Shire salinity McFarlane et al. 2004 Percentage of Change Salinity Hazard as a Percentage of shire shire with between 1989 Hazard Percentage of with salinity in 1996 salinity in 1989 salinity and (ha) ShireShire 957,581 ha 859,306 ha 1996 salinity 5,464,834 haBoddington 1.2% 0.6% 0.61% 12,767 6.7%Broomehill 4.1% 3.3% 0.75% 21,395 18.2%Dumbleyung 6.0% 5.3% 0.67% 54,169 21.3%Gnowangerup 3.3% 2.5% 0.80% 89,850 21.1%Jerramungup 2.4% 1.8% 0.56% 125,571 19.3%Katanning 7.3% 6.5% 0.77% 39,306 25.9%Kent 5.5% 4.7% 0.78% 138,454 24.6%Kulin 4.7% 3.8% 0.90% 84,794 18.0%Lake Grace 7.7% 7.0% 0.68% 273,648 26.4%Moora 7.7% 6.2% 1.46% 81,158 21.6%Narrogin 4.9% 4.4% 0.55% 45,613 28.2%Nungarin 11.1% 7.7% 3.40% 50,012 43.0%Tambellup 8.6% 7.7% 0.92% 49,286 34.3%Wagin 6.6% 5.8% 0.85% 56,488 29.0%West Arthur 2.9% 2.2% 0.69% 72,640 25.7%Wongan-Ballidu 10.9% 10.2% 0.70% 94,822 28.1%Woodanilling 5.5% 4.7% 0.83% 36,217 32.1%TOTALS 2.9% 2.6% 0.30% 5,464,834 16.8% 17,000 ha per annum The effect of climate change on South West WA hydrology
  • 17. Comparison of salinity extent and hazard Method Extrapolation NLWRA 1998 Land Monitor from studies McFarlane et al. Ferdowsian et al. 2004 1996Salt-affected in 1996 to 1.8M 4.4M 0.96M 2000 period (ha)Annual rate of increase 75,000 55,000 14,000 (ha) 2000 to 2020 2000 to 2020 1989 to 1996Final hazard area (ha) 6.1M 8.8M <5.5M The effect of climate change on South West WA hydrology
  • 18. Streamflow and flooding in the WheatbeltThe effect of climate change on South West WA hydrology
  • 19. Wet years for Narrogin in 25-year segments (Hatton and Ruprecht 2001) 6Wet years (number) 6 Wet years defined as above 1-in-10 year 5 annual recurrence interval 4 4 3 2 2 1 0 0 1900-1925 1925-1950 1950-1975 1975-2000 1900-1925 1925-1950 1950-1975 1975-2000 The effect of climate change on South West WA hydrology
  • 20. Annual floodflow for the Avon (Walyunga) Hatton and Ruprecht 2001 1200 Annual Maximum Mean 1000 90th Percentile 800Floodflo w (m 3/sec) 600 400 200 0 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 Year NB: Modelled flows from 1910 to 1969 and gauged data after 1969 The effect of climate change on South West WA hydrology
  • 21. Blackwood Basin The effect of climate change on South West WA hydrology
  • 22. Land Monitor mapped Salinity 1998The effect of climate change on South West WA hydrology
  • 23. Valley HazardThe effect of climate change on South West WA hydrology
  • 24. Predicted peak flows of the Blackwood at Darradup with January 1982 rainfall (Cyclone Bruno) Hatton and Ruprecht (2001) 6000 Calibration Prediction: Sc enario 1 - Salt-affec ted land area doubles 5000 Prediction: Sc enario 2 - Salt-affec ted land area trebles Prediction: Sc enario 3 - Salt-affec ted land area quadr uples 4000Flow (m 3/s) 3000 2000 1000 0 21/01/82 24/01/82 27/01/82 30/01/82 The effect of climate change on South West WA hydrology
  • 25. Major catchments of the Avon River Basin Ali et al. (2009) Total area~116,600 km2 Northam Walyunga
  • 26. % reduction in annual flow if rainfall is 10 and 20% less Based on data from Ali et al. (2009) 10% rainfall 20% rainfall reduction reduction compared with compared with 1976 to 2003 1976 to 2003 0 -10 3 to 4 times % change in annual flow -20 reduction 3+ times reduction -30 -40 -50 Walyunga Northam -60 -70 -80The effect of climate change on South West WA hydrology
  • 27. % reduction in peak daily flows if rainfall is 10 and 20% less Based on data from Ali et al. (2009) 10% rainfall 20% rainfall reduction reduction compared with compared with 1976 to 2003 1976 to 2003 0 1 2 -10 2+ times reduction % change in peak daily flows 2+ times -20 reduction -30 Walyunga Northam -40 -50 -60The effect of climate change on South West WA hydrology
  • 28. Groundwater levels and surface water yields in the Darling RangeThe effect of climate change on South West WA hydrology
  • 29. Annual rainfall and inflow into Perth dams Runoff is affected by climate and other factors 2500Annual Rainfall at Jarrahdale (mm) Yearly rainfall at Jarrahdale Annual Total 1911 to 1974 (1251mm) 2000 16% 1975 to 2009 (1047mm) 1500 reduction 1997 to 2009 (1003mm) 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) 800 1911 to 1974 (338GL) 700 1975 to 2009 (151GL) 600 1997 to 2009 (107GL) 500 400 55% Historical 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) The effect of climate change on South West WA hydrology
  • 30. Declining groundwater levels in Darling Range catchments CSIRO 2009 1988 1992 1996 2000 2004 2008 1988 1992 1996 2000 2004 2008 0 10 2 Gordon L4622-5A Bates E4506-3A Depth to groundwater (m) Depth to groundwater (m) 12 4 14 6 8 16 10 18 12 20 14 16 22 1988 1992 1996 2000 2004 2008 1988 1992 1996 2000 2004 2008 26 0 Cameron L4521-0928 Cobiac K3817-3A 2 Depth to groundwater (m) Depth to groundwater (m) 27 4 28 6 29 8 10 30 12 31 14 32 16The effect of climate change on South West WA hydrology
  • 31. Groundwater trend Petrone et al. 2010 1Groundwater Depth (m) 2 3 4 1988 1990 1992 1994 1996 1998 2000 2002 2004 2006 2008 2010 •Increasing annual amplitude bc1 •Decreasing groundwater depths The effect of climate change on South West WA hydrology
  • 32. Dam Inflow and Runoff Statistics 1950-2008 Rainfall and Runoff Change Point 1969/1975 1989-2008 Runoff Only Change Point 1997/2001Petrone KC, JD Hughes, TG Van Niel, RP Silberstein 2010 Geophysical Research Letters The effect of climate change on South West WA hydrology
  • 33. Groundwater Level and Runoff Runoff (mm) 50 100 150 200 250 300 350 1.0 1992 Max Groundwater Depth (m) 1.2 1991 1993 1989 1996 BC3 1999 1.4 1994 1990 2000 1988 BC2 BB3 1995 BB 1997 1.6 BC1 2 2005 1998 2003 2004 2008 BB1 2009 2007 1.8 2001 2002 BA3 2.0 BA2 BA1 2006 2.2 Runoff (mm) 50 100 150 200 250 300 350 Runoff (mm) 0 1989 1992 50 100 150 200 250 300 350Max Groundwater Depth (m) 1991 0.8 1988 Max Groundwater Depth (m) 1993 1992 1.0 1 19961990 1991 1999 1989 1997 2000 1994 1995 1.2 1993 1998 1994 1988 1990 1996 2009 1.4 2 2004 2003 1995 2005 2000 1999 2002 2007 2008 1.6 1997 2003 2001 2001 2007 2005 1998 2004 3 1.8 2006 2002 2009 2008 2.0 2006 2.2 The effect of climate change on South West WA hydrology
  • 34. Equilibrium shift in Drying Climate? • Reduction in saturated areaGW-SW Connection (groundwater discharge zone) w rflo and “saturation excess overland Inte flow” oam • Reduction in groundwater da nd L y) baseflow San e (Cla lid Zon • Reduction in interflow Pal Ro ck ent Ba se m w Eq Loss of GW-SW Connection nte rflo uil I ib ri u oam nd L m Sa nd a Sh Cl a y) ift Zone ( Pa llid Ro ck ent Ba se m after Croton and Bari 2001 The effect of climate change on South West WA hydrology
  • 35. Projected change in mean annual runoff relative tothe historical climate (1976 – 2007)• Runoff declines by 25% under median future climate and 42% under dry climateThe effect of climate change on South West WA hydrology
  • 36. Percent decline in runoff in all basins Northern region Central region Southern region d st oo oa kw al C st ac oa n k n Bl lly to ar n C no y n y el ne toChange in mean annual runoff (%) ve er n m ra re an lie ss an gi es nt w en on ur ar ar in ol Sw Bu Ke Sh Lo Pr W M H D D G C 0 -10 -20 -30 Recent climate Median future climate -40• Decline under a continuation of the recent climate (1997 to 2007) is greatest from Gingin to Collie• Decline under a median future climate is more uniform indicating that southern basins may ‘catch up’ in the drying trendThe effect of climate change on South West WA hydrology
  • 37. Groundwater levels in the Perth BasinThe effect of climate change on South West WA hydrology
  • 38. 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 elevationCSIRO South-West change Australia West WA hydrologyThe effect of climateWestern on South Sustainable Yields Project – Overview
  • 39. Land cover• Surface water catchments are mainly forested• About 60% of the Perth Basin is cleared about 56% of this being under dryland agriculture• The uncleared areas Gnangara Mound include coastal areas north of Perth, the Gnangara Mound and the Blackwood Plateau Blackwood PlateauCSIRO South-West change Australia West WA hydrologyThe effect of climateWestern on South Sustainable Yields Project – Overview
  • 40. Land cover likely to affect recharge / dischargeGroundwater assessment areas• 56% dryland agriculture• 38% native vegetation• 6% plantations, urban, irrigated, open waterThe effect of climate change on South West WA hydrology
  • 41. Maximum depth of the watertable in the southern half of the Perth Basin in 2007• Coloured areas are potential GDEs if not cleared• Coastal plain soils have very shallow watertables except Gnangara and Spearwood Dunes• Plateaux areas mainly 22% 14% have deep watertables 10% 46%The effect of climate change on South West WA hydrology
  • 42. Change in groundwater levels between 2008 and2030 under climate and development scenariosThe effect of climate change on South West WA hydrology
  • 43. Surface water - groundwater interactionsThe effect of climate change on South West WA hydrology
  • 44. Gaining and losing sections in Gingin Brook CSIRO 2009 GAINING LOSINGThe effect of climate change on South West WA hydrology
  • 45. Amount and proportion of baseflow will change as both streamflow and groundwater levels reduce Current base flow is about two-thirds of streamflow Under a dry future climate baseflow may reduce 80 Groundwater discharge 70 Surface water flow 60 50 GL/year 40 30 20 10 0 1972 1977 1982 1987 1992 1997 2002 2007The effect of climate change on South West WA hydrology
  • 46. Collie groundwater basin level changes between 2008 and 2030Groundwater levels are less affected near riversThe effect of climate change on South West WA hydrology
  • 47. Conclusions 1• The SW of WA experienced a climate shift in about 1975 with rainfall amounts and intensities reducing. The accompanying rise in temperatures may be contributing to drier soils• Groundwater levels in the northern and central Wheatbelt are mainly falling and the rate of salinisation has slowed.• Flooding in the Wheatbelt was projected to increase because of salinisation and increased rainfall intensities• However runoff and flooding have decreased and are projected to decrease further as catchments dry and if intensities remain low or fall further• There have been major reductions in streamflows in northern jarrah forest streams – initially due to the reduced rainfall and more recently due to lower groundwater levels resulting in changes in runoff processes• This trend is projected to continue to more southerly streams The effect of climate change on South West WA hydrology
  • 48. Conclusions 2• Groundwater levels under the Perth Basin are falling under perennial vegetation and in the north but rising under dryland agriculture in most areas• Levels are expected to fall further in future or rise more slowly under dryland agriculture in the south and central parts• Where streams cross the Perth and Collie Basins they currently gain fresh groundwater• These trends may reverse and brackish or saline streamflow may contaminate nearby fresh aquifers• Water dependent ecosystems have already been badly impacted by climate change and this is likely to worsen• Hydrological processes need to be understood if future projections are to reflect these changesThe effect of climate change on South West WA hydrology
  • 49. Possible areas for post graduate study• Surface water – groundwater interactions under climate change (hydrology, isotopes to separate flow components, modelling)• Managing vegetation to influence recharge and runoff in a drier climate – e.g. Gnangara Mound post-pine areas• The influence of lower rainfall, higher temperatures, higher potential evapotranspiration and more CO2 on plants and hydrology (i.e. vegetation is also changing as a response to climate change so hydrological impacts are complex)• Methods of reclaiming saline Wheatbelt valleys where groundwater levels have receded• Ways of retaining important water dependent ecosystems in a drying climate (e.g. use of stormwater and treated wastewater to augment natural flows)The effect of climate change on South West WA hydrology
  • 50. Questions?CSIRO South-West change Australia West WA hydrologyThe effect of climateWestern on South Sustainable Yields Project – Water Yields and Demands

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