Murray-Darling storage in drastic decline

Water levels in the major storages of the Murray-Darling have declined drastically in recent weeks.

Murray Darling Basin storage levels.

Water levels in the major storages of the Murray-Darling have declined drastically in recent weeks, with all but one in the northern basin at less than 10 per cent capacity and most in the southern basin only half full or much less.

Lake Victoria in far western NSW is at 54 per cent capacity, down from 75 per cent on December 11, while the massive Lake Hume on the NSW-Victorian border is now at 22 per cent, down from 32 per cent.

Water levels in the Murray-Darling’s major storages have declined drastically in recent weeks. Picture: Getty Images

The dire situation has prompted authorities to warn that without good rain in winter and spring, water availability will be even more restricted next year.

While towns on the Murray would still get water, farmers would be likely to face even greater reduction in water allocated for irrigation, placing further pressure on agricultural production and food prices.

In its latest drought update released on Wednesday, the Murray-Darling Basin Authority said that apart from a few isolated downfalls, no rain had fallen in most areas that feed the southeast river systems, and the situation was expected to get worse.

MDBA executive director of river operations Andrew Reynolds said the two biggest storages used for long-term water security, Dartmouth Dam in Victoria and Hume, were in marked decline.

“We are starting to use that water up,” he said. “If we don’t get good inflows to replenish it, that will reduce availability next year.”

Allocation of water was the responsibility of the states, Mr Reynolds said. “Town supplies are the highest priority, and we are reasonably confident about maintaining those,” he said.

But if water levels continued to decline, he said, states “might implement some other restrictions”.

December rainfall was the lowest on record for Australia and the second-driest on record for the basin, the MDBA said.

Areas of the northern basin and parts of South Australia experienced the lowest rainfall on record.

In the Upper Murray, flows receded during the last two weeks of December although some localised rain slightly increased flows in early January, the MDBA said.

“However, flows in the catchment of the basin’s largest river and its tributaries remain very low,” the authority said.

“Most of the northern basin’s rivers are not flowing or have very low flows.”

As a consequence, the volume of water in basin storages continues to decline.

“For the third consecutive year, the northern basin did not receive significant inflows during 2019, meaning that already low water storages further declined to very low levels,” the MDBA said.

The eight northern basin storage volumes are mostly in low single-digit percentages, with only Chaffey Dam in double digits at a still low 13 per cent, the MDBA said. The southern basin is in better condition, but 2019 inflows were well below average and storages were lower than usual for this time of the year, it said.

“The major storages of Lake Hume and Lake Victoria have fallen markedly in the past month,” the authority said.

Continuing dry and hot conditions, which increase evaporation and reduce flows to storages, point to further declines over summer.

Reduced inflows and stream flows are affecting water quality at many locations throughout the basin, the MDBA says, and conditions are expected to deteriorate further over summer.

Nine new areas across NSW and Victoria are now on red alert for blue-green algae, bringing the total to 20, with 17 in NSW and three in Victoria.