The approach to estimating what water use would have been but for the Basin Plan water recovery considers three components:
-
observed water use in each year
-
allocations to buyback volumes — it is assumed that the annual allocations made to entitlements purchased by Government under the buyback would otherwise have been allocated to and used by irrigators
-
an estimated change to net trade — Because observed water use includes volumes traded in, it needs to be recognised that some of this trade in would not have occurred absent the reductions in allocations associated with the lower level of entitlements held after buyback. Victoria has been a net importer of water allocation in most years during the water recovery and part of the reason for this net import may be using trade as a means to adjust to the changes in the consumptive pool. This is consistent with the net trade pattern observed prior to water recovery where Victoria would be a net importer in response to reduced water availability (NWC, 2009). Net trade was adjusted by the proportion of the environmental buyback allocation volumes compared to observed water use.
The sum of these three components is the estimated counterfactual water use. (Other counterfactual socio-economic issues are considered in Chapter 10.) Carryover use (i.e. risk management) may have also been different as a result of the water recovery program, although this has not been quantified.
Table sets out the elements of this calculation, and a comparison with observed northern Victorian irrigation water use is in Figure below.
Table : Observed and counterfactual water use
|
2004/05
|
2008/09
|
2009/10
|
2010/11
|
2011/12
|
2012/13
|
2013/14
|
2014/15
|
2015/16
|
Observed water use (GL)
|
2,150
|
924
|
1,135
|
751
|
1,731
|
2,402
|
1,857
|
2,033
|
1,762
|
Allocation to buyback (GL)
|
0
|
2
|
80
|
219
|
340
|
516
|
517
|
518
|
492
|
Change to net trade (GL)
|
0.0
|
-0.5
|
-4.6
|
-71.5
|
1.6
|
31.4
|
-54.0
|
-15.3
|
-62.2
|
Counter-factual water use (GL)
|
2,150
|
926
|
1,210
|
899
|
2,073
|
2,950
|
2,320
|
2,535
|
2,192
|
Difference between counter-factual and observed (GL)
|
0
|
-2
|
-75
|
-148
|
-342
|
-548
|
-463
|
-502
|
-430
|
Figure : Observed and counterfactual water use (Victoria)
Due to the relatively fixed water demands of horticulture (discussed further in section 5.5), it is assumed that LMW’s diverters or districts would not have used this additional water. The larger volumetric change in water use are likely to have been in GMW districts (where dairy and cropping can use additional volumes). The chart below shows the expected change to water use in GMW districts. It should also be noted that the reduced net trade into Victoria is likely to have been applied to rice crops in the Riverina.
Figure : Observed and counterfactual water use (GMW districts)
Given the variability observed in GMW diverters, the counterfactual water use is also expected to be higher.
Figure : Observed and counterfactual water use (GMW diverters)
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