Urban Water Security Research Alliance

Transcription

1 Urban Water Security Research Alliance Climate and Water over South East Queensland: Past and Future Wenju Cai Climate and Water Science Forum, June 2012

2 Considering Climate Change Figure sourced from SEQ Water Strategy The current SEQ Water Strategy considers climate change as a change to the maximum yield that can be delivered while meeting the pre-determined Level of Service (LOS) performance objectives.

3 Time sequence of SEQ water storage level ( )

4 Research Questions Research question 1: What causes drought in the SEQ region, and how the properties of drought (intensity, duration and frequency) may change in a warming climate, in addition to forcing by multidecadal variability (in conjunction with QCCCE). Research question 2: How best to translate global projections of climate change (rainfall and other hydrological fields) into future water availability information (in collaboration with DERM). Research question 3: How sensitive to the resolution of climate information is the SEQ streamflow model (IQQM).

5 Most models do not produce the observed trends Cai et al. 2010: Asymmetry in ENSO Teleconnection with Regional Rainfall, Its Multidecadal Variability, and Impact. J. Climate, 23,

6 SEQ summer rainfall 2011

7 El Niño & La Niña Index NINO-3.4 NINO C C for 5 months= El Niño NINO C C for 5 months= La Niña Courtesy of McPdaden

8 Cai et al. 2010

9 The nonlinearity oscillates on decadal time scale La Niña El Niño

10 La Niña El Niño La Niña El Niño?

11 Negative PDO Positive PDO La Nina El Nino La Nina El Nino

12 Cai et al. 2010

13 Cai and van Rensch (2012) The 2011 southeast Queensland extreme summer rainfall: a confirmation of a negative Pacific Decadal Oscillation phase? The flood constitutes a confirmation of the PDO changing to a negative phase The result implies an increased chance of high summer rainfall events over the region during La Niña events in the upcoming decade or so.

14 95% significance Really becoming negative

15 Model Details KINGAROY KINGAROY NANANGO NANANGO KILCOY KILCOY NAMBOUR NAMBOUR BUDERIM BUDERIM CALOUNDRA CALOUNDRA WOODFORD WOODFORD The hydrologic model used in this study covers the Brisbane River catchment upstream of the tidal limit CROWS NEST CROWS NEST ESK ESK Somerset Dam Somerset Dam CABOOLTURE CABOOLTURE DECEPTION BAY DECEPTION BAY Historic rainfall and evaporation data is sourced from SILO OAKEY OAKEY PITTSWORTH PITTSWORTH TOOWOOMBA TOOWOOMBA Wivenhoe Dam Wivenhoe Dam GATTON GATTON LAIDLEY LAIDLEY IPSWICH IPSWICH BRISBANE BRISBANE Urban demands are set to full utilisation of existing entitlements, approximately 280 GL/a, with no restriction rules in place BOONAH BOONAH BEAUDESERT BEAUDESERT The model simulation period is from 1889 to 2000 STUDY AREA STUDY AREA

16 Climate Change Models Analysed Model Emissions Global Circulation Model (GCM) Cubic Conformal Atmospheric Model (CCAM) downscaling Model Emissions Scenario 1 Scenario 1 CSIRO Mark 3.0 A2 CSIRO Mark 3.0 A2 CSIRO Mark 3.5 A2 CSIRO Mark 3.5 A2 GFDL CM 2.1 A2 GFDL CM 2.1 A2 MIROC 3.2 (medres) A2 MIROC 3.2 (medres) A2 MPI ECHAM 5 A2 MPI ECHAM 5 A2 NCAR CCSM 3.0 A2 NCAR CCSM 3.0 A2 UKMO HADCM3 A2 UKMO HADCM3 A2 UKMO HADGEM1 A2 UKMO HADGEM1 A2 IAP FGOALS 1.0 A1B INMCM 3.0 A2, A1B MIROC 3.2 (hires) A1B CSIRO Mark 3.0 A1B MIUB echo A2 NCAR CCSM 3.0 A1B 8 Directly Comparable 6 Additional Models 1 All model projections were scaled to Emissions Scenario A1FI

17 Spatial Variation of Climate Projections Monthly percentage rainfall change for downscaled CSIRO Mk 3.5 (for year 2050 SRES A1FI) (source Kent, D., CSIRO) Monthly percentage evaporation change for downscaled CSIRO Mk 3.5 (for year 2050 SRES A1FI) (source Kent, D., CSIRO) Spatial variation in downscaled projections is more pronounced for rainfall than for evaporation

18 Downscaling Effects on Rainfall Mean Monthly Rainfall - Subcatchment UB1 (07/ /2000) Global Circulation Model Generation Method (GCM) 160 Mean Monthly Rainfall (mm) Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec Month Downscaled models display greater variability in rainfall projections than GCMs, but generally result in reduced wet season rainfall

19 Downscaling Effects on Evaporation Mean Monthly Evaporation (mm) Mean Monthly Evaporation (mm) Downscaled models display greater variability in evaporation projections and are generally higher than the original GCM projection Some of this difference may be attributed to the method of calculating the evaporation change within CCAM not all GCMs produced evaporation output (ie. evaporation was derived from temperature relationships)

20 Downscaling Effects on Runoff Generation The combination of increased evaporation and decreased wet season rainfall results in significantly reduced runoff generation/inflow to the hydrologic model (IQQM)

21 Climate Change Effect on Storage Behaviour (GCM) Combined Simulated Storage Volume Somerset and Wivenhoe Dams Global Circulation Model Generation Method (GCM) Several GCMs result in increased storage volume % 50% % DSV 0 Date

22 Downscaling Effects on Storage Behaviour (CCAM) The system does not recover from the federation drought until 1927! All but one downscaled GCM result in decreased storage volumes Storage Volume (ML)

23 Comparison of Median GCM and CCAM Projections The combined effect of reduced rainfall and increased evaporation cause the gradual decline in storage volume during these two periods

24 No Rainfall Change Results (GCM)

25 No Rainfall Change Results (CCAM)

26

27

28 Urban Water Security Research Alliance THANK YOU

29 Raw Pan evaporation (epan_ave) extracted from CCAM

30