The southern Murray-Darling Basin occupies the southern half of NSW and northern Victoria. It receives most of its water from rain in the cooler months that fills dams, with any overflow spilling into the floodplains.
The Murrumbidgee River catchment is approximately 84,000 square kilometres, or about 8% of the basin. It encompasses a complex series of wetlands and floodplains.
The height of the Murrumbidgee River—the third longest in Australia and highly valued for irrigation and hydro-electricity—has dropped by about 30% during the growing season. This is a loss of approximately 300 million litres per day.
The findings follow a major report the Intergovernmental Panel on Climate Change released on Monday, which found much of Australia will become more arid as the world warms. This will bring reduced river flows, mass tree deaths, more droughts and drier soils.
Given this drop is associated with the wettest months from April to September, the outlook for the warmer months between October and March is dismal. The number of days when the river ceases to flow will certainly increase.
Dam building and excessive irrigation are often behind decreased river flows across the Murray-Darling Basin. But in this case, we can point to decreased rainfall from climate change as the reason the Murrumbidgee River catchment is losing water.
Under climate change, we can expect further drying of wetlands and major losses of wildlife habitat. For farmers and communities, we can expect huge reductions in the amount of water allocated for irrigation. The ability for communities to survive these severe decreases in agricultural productivity will be tested.