Geoscience Reference
In-Depth Information
Increases (%) in mean annual potential evaporation (Penman-Monteith;
Allen 1998) for Emerald (Qld), Birchip (Vic.) and Kellerberrin (WA) for
2030 and 2050 calculated from GCM output (CSIRO Mk 3.5) or from
perturbing the historical climate records by the same mean change in
maximum and minimum temperatures as found in the GCM output
2030
2050
GCM output
Modified
historical
GCM output
Modified
historical
Emerald
7.8
5.2
9.5
7.2
Birchip
8.6
5.7
10.3
7.3
Kellerberrin
7.9
6.0
9.4
7.4
Table 6.2
.
Catchments in the Murray-Darling Basin and the prospective changes in
water availability under 'dry', median and 'wet' scenarios for 2030
2
Climate change
(dry)
Climate change
(median)
Climate change
(wet)
Condamine-Ballonne
2
26
2
8
1
19
Lachlan
2
30
2
11
1
6
Goulburn-Broken
2
45
2
14
2
3
Murray
2
41
2
14
1
7
Water availability and quality
The surface and groundwater resources that supply water used in irrigated
agriculture in Australia are likely to be substantially affected by lower average
rainfall and higher evaporation in a 4°C-plus Australia. For example, annual
water availability in the Murray-Darling Basin could change significantly by
2030, with possible substantial decreases of 26 to 45 per cent in some catch-
ments, through to possible increases of up to 19 per cent in one (
Table 6.2
).
The median scenarios, however, all indicate reductions in average annual flow
although increased annual variability in rainfall may increase the size of flood
events.
Reductions in water availability will likely worsen as one moves from north to
south in the Murray-Darling Basin. In the case of southern catchments like the
Goulburn Broken (in Victoria), there has already been a 15 per cent reduction
in rainfall and a 45 per cent reduction in water availability over the drought-
affected decade up to 2010 (CSIRO, 2008). There may also be reductions in
water quality, for instance, as salt concentrations increase (Beare and Heaney,
2002).
Projected average declines in river flows and higher flow variability in
southern Australia are expected to reduce irrigation water availability (Quiggin
