‘High likelihood’ Murray-Darling water entitlements are less reliable due to climate change

A report into water-sharing arrangements in the southern Murray-Darling Basin has found that the past two decades have seen a “marked decrease” in the volume of water available in the system.

Mick Keelty, the interim inspector-general of Murray-Darling Basin water resources, was commissioned in December 2019 by then-federal water minister David Littleproud to assess the impact of changing inflows into the southern MDB, after protests from farmers calling for the abolition of the Murray-Darling Basin Plan.

Keelty found the median average inflow over the past 20 years is approximately half that of the previous 100 years and the frequency of drier years has also increased.

“While there may be many factors contributing to the extent of observed inflow reductions, the lack of rainfall and runoff has been the primary driver for the conditions being experienced by many across the basin in recent times,” the report said. As a result, implications for future inflow trends were “uncertain”.

The report said that there was now a “high likelihood” that historical expectations of reliability when it comes to general security water entitlements are no longer accurate because of climate change.

Some irrigators had expressed concerns that entitlement reliability had reduced because of changes in irrigator behavior and lack of compliance, but Keelty found that a changing climate was a bigger factor, compounded by “poor historical strategic business decisions” from many irrigators.

“These ranged from missed opportunities to convert NSW general security to high security entitlements, selling water entitlements and choosing to rely on the allocation market, as well as decisions about financing, expansion and crop choice,” the report said.

In addition, Keelty said it was difficult to attribute conveyance losses (the net amount lost before consumption to factors such as evaporation and seepage) to any single source, such as extensive horticultural development in certain regions.

“The Murray-Darling Basin Authority found in its Losses Report that conveyance losses in 2018-19 were comparable (albeit slightly higher) to years when the flows and operational strategies were similar, indicating that the impacts of downstream development on conveyance might not be as material as some people suggest,” the report said.

Keelty made five recommendations that have all been accepted by federal water minister Keith Pitt, including one that the basin officials committee, the body that advises the water ministerial council, should consider creating an authoritative platform with information on water ownership and prices, to provide higher levels of transparency and trust and improve water markets literacy more broadly.

Consultant Aither, which helped compile the report, said in a statement: “While the inquiry found that the interstate water-sharing arrangements set out by the MDB agreement are being implemented as intended, the report does highlight the challenge of equitably and efficiently sharing scarce water supplies and the importance of having a robust and transparent framework for doing so.

“The fact that the arrangements in the MDB agreement have withstood more than 100 years of history, amidst the most variable inflows in the world and a changing climate, is significant. With a water entitlement market valued at over A$20 billion ($12.8 billion; €11.7 billion) reliant on these arrangements, it is also well worth continued investment to ensure that the arrangements continue to be appropriate and transparent.