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Climate change and water resources in the Murray Darling Basin ...

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ABARE CONFERENCE PAPER 02.11<br />

The sensitivity of <strong>the</strong> result to <strong>the</strong> effect of potential evaporation is large. If <strong>the</strong> level of<br />

evapotranspiration is not <strong>in</strong>creased to reflect <strong>in</strong>creased potential evaporation, river flows<br />

are between 8 <strong>and</strong> 28 per cent higher by 2100. Economic costs are reduced by around 65<br />

per cent. The impacts are greater <strong>in</strong> <strong>the</strong> nor<strong>the</strong>rn part of <strong>the</strong> bas<strong>in</strong>, as <strong>the</strong> <strong>in</strong>creases <strong>in</strong> potential<br />

evaporation are greater.<br />

The impacts on <strong>water</strong> quality are mixed. The salt concentration of surface runoff above<br />

<strong>the</strong> irrigation areas is lower when evapotranspiration is not affected by potential evaporation<br />

because <strong>the</strong> <strong>in</strong>crease <strong>in</strong> surface <strong>water</strong> runoff more than offsets <strong>the</strong> <strong>in</strong>crease <strong>in</strong> ground<strong>water</strong><br />

discharge. However, higher runoff leads to <strong>in</strong>creases <strong>in</strong> <strong>water</strong> availability for irrigation.<br />

This leads to higher levels of ground<strong>water</strong> discharge from <strong>the</strong> irrigation areas <strong>and</strong> a<br />

reduction <strong>in</strong> <strong>water</strong> quality <strong>in</strong> <strong>the</strong> ma<strong>in</strong> stem of <strong>the</strong> <strong>Murray</strong> River.<br />

31

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