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Water Wednesday 2009 July Bill Young
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Water Wednesday 2009 July Bill Young

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Bill Young at Water Wednesday

Bill Young at Water Wednesday

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Water Wednesday 2009 July Bill Young Water Wednesday 2009 July Bill Young Presentation Transcript

  • Water Research Centre Water Wednesday Sustaining the River Murray with less water
  • Declining Streamflow – the Future for the Murray-Darling Basin? Bill Young Director, Basin Plan Modelling Murray-Darling Basin Authority 15 July 2009, Water Research Centre, University of Adelaide
  • Overview • The current drought in the historical context • Climate change projections – Rainfall and runoff – Water availability – Use under current water sharing arrangements – Impacts on end of system flows
  • Natural flow to the sea
  • Growth in storage capacity & diversions 40,000 Capacity major storages 35,000 Average annual flow of all rivers (without-development) 30,000 Average natural flow to the sea Total surface water diversions 25,000 Volume (GL) 20,000 15,000 10,000 5,000 0 1920 1930 1940 1950 1960 1970 1980 1990 2000 2010
  • Flows over the barrages
  • Reduction in Barrage flows • Natural flows at barrages – 1895 – 2006 12,200 GL/yr – 1987 – 2006, 86% of long-term average 10,550 GL/yr – 2002 – 2006, 46% of long-term average 5,570 GL/yr • With current development/sharing – 56% reduction over 1895 – 2006 (111 years) 5,090 GL/yr – 62% reduction over 1987 – 2006 (20 years) 4,000 GL/y – 96% reduction over 2002 – 2006 (5 years) 220 GL/yr
  • Percent difference in rainfall and runoff
  • Change (mm) in rainfall and runoff
  • Southern MDB Rainfall
  • Southern MDB Runoff
  • Is this just drought or is it global warming? • Decline in Autumn rainfall – Probably linked to intensification of sub-tropical ridge – Decrease in frequency of La Nina events – Both consistent with global warming predictions • Other changes observed in climate system which are consistent with global warming predictions – More extreme and earlier than expected • However, similar changes are known to occur as a part of decadal scale climate variability
  • Recent climate: reduced autumn rainfall 80 70 60 50 40 30 1895 – 2006 1997 – 2006 20 1936 – 1945 10 1895 – 1904 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
  • Recent climate: reduced autumn runoff % Difference from long-term mean 16 Rainfall Runoff 1997-2006 -13 % -39 % 14 1937-1946 -14 % -22 % 1895-1904 -11 % -31 % 12 10 8 6 4 1895 – 2006 1997 – 2006 2 1936 – 1945 1895 – 1904 0 Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
  • Best conclusion… “It is likely that climate change is contributing to the current drought both through increased temperatures and a shift in rainfall drivers towards a phase associated with lower rainfall in the southern MDB” Accurate quantification of this contribution remains a difficult and ongoing research issue…
  • Percent changes in runoff by 2030
  • Percent changes in runoff by 2030
  • Climate change projections for MDB High global warming 80 80 Northern MDB Southern MDB 40 40 0 0 Runoff change (%) -40 -40 -80 -80 2070 1990 2010 2030 2050 2070 1990 2010 2030 2050 2070 Medium global warming 80 80 Northern MDB Southern MDB 40 40 0 0 -40 -40 -80 -80 2070 1990 2010 2030 2050 2070 1990 2010 2030 2050 2070
  • Median 2030 streamflow reductions
  • Dry extreme 2030 streamflow reductions
  • Streamflow reduction due to diversions
  • Impact of climate by region • MDB: median impact is an 11% reduction in available water – ranges from 2% to 21% reduction across regions – ~2500 GL/year across MDB on average • Consequence under current water sharing arrangements is a 4% reduction in surface water diversions – ranges from 1% increase to 11 percent decrease across regions – ~450 GL/yr across MDB on average 5% Change under median 2030 climate (%) 0% -5% -10% -15% Surface water availability -20% Surface water diversions -25% a e oi ee g e on pe am n ca n s go o s ir y ns gh er nn ni li n ge e la ra am er ro yd dg s vo re ve ok m ea ch oo iv lo Pa ar ur pa an w im N ar bi -A O R Br Ba Ba tler La M M -D G R m W W n- er on e- ru as fty ur C rd dd in rw ur -C Lo lb Bo m Lo M ou ie da nt ar G ou on qu M C ac n M er st Ea
  • Change in annual surface Change in annual surface Change in annual surface water diversions (%) water diversions (%) water diversions (%) -60% -50% -40% -30% -20% -10% 0% 10% -60% -50% -40% -30% -20% -10% 0% 10% -60% -50% -40% -30% -20% -10% 0% 10% Co Pa nd am W roo ine a rre -B go al on Bo M ne Average rd oon er 1-year lowest Ri ie M ve ac G rs qu wy ar di ie- Ca Na r Ba s tle mo rw r e i on ag -D h ar l M La i ng ur ru c hla m bi n dg M ee G ur ra ou y lbu Ov rn en -B s Ca rok Lo mp en Ea dd a st on spe er n -A M v tL W oc a im of ty m Change in diversions in dry years Ra era ng es Change in annual surface Change in annual surface Change in annual surface water diversions (%) water diversions (%) water diversions (%) -100% -80% -60% -40% -20% 0% Co -100% -80% -60% -40% -20% 0% -100% -80% -60% -40% -20% 0% 20% nd Pa am W roo i ar 1
  • Impact sharing – median 2030 climate Use Loss Outflow 0% -5% -10% Change (%) -15% -20% -25% -30%
  • Flow over the barrages – no diversions
  • Flow over the barrages – current sharing
  • End of Basin flows • Total flow at the Murray mouth reduced by 61 percent • Flow ceases 40 percent of the time compared to 1 percent of the time in the absence of consumptive use • Severe drought inflows to Lower Lakes (<1500 GL/year) – Never under without-development conditions – 9 percent of years at current development with historical climate – 13 percent of years under median 2030 climate – 33 percent of years under dry extreme 2030 climate 1895 1915 1935 1955 1975 1995
  • Conclusions • We are in a severe drought which can be partly attributed to climate change • The recent period very low flows over the barrages is a result both of drought and surface water diversions • Current water sharing arrangements would transfer a disproportionate fraction of the impact of anticipated climate change to the environment • The new Basin Plan will set sustainable diversion limits on all water resources considering the range of possible future climate conditions
  • Acknowledgements • CSIRO MDB Sustainable Yields Project • National Water Commission • Francis Chiew, CSIRO (SEACI Project)