Water availability will drop in the Murray-Darling

Water availability in the southern Murray-Darling Basin is on the decline, and there won’t be enough to go around in the future, according to new research from the University of Technology Sydney (UTS).

In a study published in Scientific Reports, researchers used statistical analysis and machine learning to establish and predict trends in rainfall and river height in the Murrumbidgee River catchment in the southern Murray-Darling Basin.

They found that the impacts of climate change have accelerated catchment drying since the 1990s, which is predicted to continue and drastically reduce future water availability.

This will place pressure on the sharing of water between community, agricultural and environmental needs because there simply won’t be enough water.

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“The southern MDB receives most of its annual catchment run-off during the cool season, from April to September,” says Milton Speer, corresponding author for the study.

“Our research shows that from 1965, up to and including this year, April to May cool-season rainfall, net inflows to the dams and downstream river heights have significantly decreased in the Murrumbidgee River catchment.

“Regardless of the mandated environmental flows in the last decade and the annually determined sustainable extraction limits on irrigation, water availability from the Murrumbidgee River at Wagga Wagga and Hay over recent decades continues to be affected by changes in catchment precipitation and run-off.

“We conclude that decreased river heights at Wagga Wagga and Hay in the 27-year period, 1992 to 2018, occurred as a result of a change in seasonality of rainfall and greater potential evaporation during the current accelerated period of global warming – total evaporation having increased by up to 2.5 millimetres per decade since the 1970s.”

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The authors say this clear prediction should prompt a review of water sustainability in the area, as well as other water systems connected to the Murrumbidgee River.

“A reduction in regular winter-spring downstream floods has already impacted wetland ecosystems because seasonal floods are now much less frequent,” says Speer.

“Meanwhile downstream irrigation from the dams is exacerbating the reduction in water availability because there is not enough water to be shared between community, agricultural needs and the environment.

“At stake is the viability of the MDB in the face of the dangers presented from continued global warming. Decisions about the competing interests of human and animal needs, irrigation for agriculture and the environment need to be based on these impacts.”

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