National Water Account 2016

Murray–Darling Basin: Outlook 2016–17

Rainfall conditions across the Murray–Darling Basin region are expected to improve from the 2015–16 year, which is likely to contribute to an increase in surface water storage. Total water assets are expected to remain in surplus at 30 June 2017. Water use is expected to increase during the year, which takes into account current and anticipated climate conditions in the region.

 

 

 

Future prospects

This section looks forward over the next reporting period and considers what water inflows and commitments might affect the region's water resources during the 2016–17 year. It is anticipated there will be a surplus of available water assets and future water rights over water liabilities and future water commitments that are expected to be settled within 12 months of the report date (Figure S12).

 

Figure S12 Water outlook for the Murray–Darling Basin region for 2016

Figure S12 Water outlook for the Murray–Darling Basin region for 2016 

 

Expected inflows

At the time of publication, rainfall over the Murray–Darling Basin region during the first eleven months of the 2016–17 year (July–May) was generally above average (Figure S13) and 37% higher than the same period last year. This has led to increases in surface water storage volumes across the region. According to the Bureau of Meteorology's Water Storages website, storage volumes at 31 May 2017 were approximately 66% full compared with 33% full at the same time last year.

 

Figure S13 Rainfall deciles for the Murray–Darling Basin region from July 2016–May 2017
Figure S13 Rainfall deciles for the Murray–Darling Basin region from July 2016–May 2017

 

The Bureau's climate outlook (released on 25 May 2017) indicates a high probability of below-average rainfall over most of southern Australia, including the Murray–Darling Basin region, for the next three months (June–August 2017). This outlook is influenced by warming of tropical Pacific sea surface temperatures and a cooler than average eastern Indian Ocean. Despite the relatively poor rainfall outlook for the last month of the 2016–17 year, given the above-average rainfall and soil moisture conditions during July 2016–May 2017 (see the Bureau's Australian Landscape Water Balance product), total annual streamflows and storage inflows for the year are still expected to be higher than they were during the 2015–16 year.

The expected inflows for the 2016–17 year are based on a regression analysis between annual net inflow and annual rainfall using the past seven years of data (2009–2016). Based on this analysis, the combined expected precipitation (approximately 1,400,000 ML) and river inflows into the storages (approximately 12,750,000 ML) could exceed the expected evaporation from the storages (approximately 3,250,000 ML) during the year.

The expected inter-region supply during the 2016–17 year of 1,800,000 ML is estimated based on the average annual delivered volume over the past five years.

 

Future commitments

The expected surface water diversions (8,800,000 ML) and groundwater extractions (1,500,000 ML) are based on water use data for the 2014–15 year, a period when similar water availability was experienced in the region.

 

Contingent water assets

Non-extractable portion of groundwater

Jurisdictions within the Murray–Darling Basin region are responsible for setting annual extraction limits on the groundwater aquifers within sustainable diversion limit areas. This limit is established to protect groundwater dependent ecosystems. Water up to this prescribed maximum extraction limit is recognised as a water asset in the Statement of Water Assets and Water Liabilities. The volume of water beyond the annual extraction limit is considered a contingent water asset for aquifers in the region; however, there is currently insufficient information available regarding groundwater resources in the region to allow for a volumetric estimate.

 

Inter-region claim on water

Inter-region claims on water that can be considered as contingent water assets in the Murray–Darling Basin region are a claim on Snowy Hydro to release water to the region and a claim by Grampians Wimmera–Mallee Water on the Glenelg catchment.

The Snowy Hydro claim is estimated based on several input variables at the commencement of the water year; however, input variables on which the actual entitled release depends include dry inflow sequence volume reduction (allowance to reduce guaranteed supply volume when inflows are less than those in the drought originally modelled) for the year and the volume of water provided by Snowy Hydro to New South Wales irrigators under separate agreements. 

Volumes for these two variables are not known at the beginning of the year, so the Snowy Hydro claim is a contingent water asset for the Murray–Darling Basin region.

Under a Victorian bulk entitlement, Grampians Wimmera–Mallee Water is able to transfer water to the Wimmera–Mallee supply system, located within the Murray–Darling Basin region's boundaries from:

  • the Glenelg River upstream and including Rocklands Reservoir
  • the first and second Wannon creeks upstream of and including the weirs.  

The bulk entitlement requires Grampians Wimmera–Mallee Water to release a flow for domestic and stock use and other social and environmental purposes in the Glenelg River downstream of Rocklands Reservoir. The volume that can be diverted to the Murray–Darling Basin will depend upon the inflows into the Glenelg River and the requirement to meet the Glenelg compensation flows. Therefore, the claim is a contingent water asset.