Climate change and climate uncertainty in the MurrayDarling Basin

1
Climate change and climate uncertainty in the
Murray-Darling Basin

• Adamson, Mallawaarachchi and Quiggin
• AARES 2007

2
Overview

• Climate change and uncertainty
• A state-contingent model of the Murray-Darling
  Basin
• Adjustment to a warmer, drier climate

3
Climate Change vs Uncertainty

• Seasonal patterns natural variations in the
  system (floods, drought, variations from the
  mean)
• Change movement towards a new mean (in this
  case potentially irreversible)
• or what makes people worry is adverse
  consequences to which we do not know the outcome

4
Climate Change (Perth stream flows)
http//www.watercorporation.com.au/_images/Dams/da
ms_streamflow.gif
5
MDB InflowsNatural variation or climate change ?
Source MDBC Ministerial Briefing, November 2006
6
Current v Natural Flows

• Capital investment to normalise flows
• Conjunctive management
• High pressure on system from competing sectors
  (quality and quantity)
• Regular over use of water (turn off the tap)

7
Current v Natural Flows
8
Runoff v Rainfall

• Jones et al use a simple model relating
  proportional changes in mean annual runoff (Q) to
  proportional changes in mean annual precipitation
  (P) and potential evapotranspiration (Ep)
• dQ A dP B dEp
• Here A is the elasticity of catchment runoff with
  respect to changes in precipitation, P and B are
  the elasticity of catchment runoff with respect
  to changes in evaporation,

9
Climate Change 2030
10
Over Allocation Climate Change

• Manipulating natural flows means no flush out
  event
• Storing salt on the land
• Environmental issues (fish spawning, etc)

11
Model
12
Water Use (GL)
13
Salinity Levels (mg/L)
14
Basin Surplus (m)
15
Regional Impacts

• Under climate change less water means higher
  salinity less profit as flow down the system
• More land will shift into dryland production

16
Issues Still to be Addressed

• Climate change impacts on yield (Trang)
• Climate change impacts on pests
• Probability distribution

17
Policy Issues

• Multiple use tradeoffs for available water
• CAP will have to be addressed
• River pumpers property rights
• Ground water Farm dams
• Water quality
• Transfers into the basin from the Snowy River
• Salinity Mitigation /or salt tolerant species
• Urban water quality
• Environmental issues

18
Summary

• Attempted to highlight nature of interactions
  between impacts of rainfall availability, runoff
  and water use patterns under 1 climate change
  scenario.
• Many climate change scenario with alternative
  spatial impacts
• Irrigators will adapt, but net cost will be
  substantial