Waranga Basin fills early

Promising start to the irrigation season, as Waranga Basin fills early

Water
WARANGA BASIN FILLING: The Stuart Murray Canal, Nagambie, supplies water to parts of the Central Goulburn irrigation area and the Waranga Basin water storage.

WARANGA BASIN FILLING: The Stuart Murray Canal, Nagambie, supplies water to parts of the Central Goulburn irrigation area and the Waranga Basin water storage.

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Rainfall fuels confidence after Waranga fills early.

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Good rainfall across the catchments has allowed Goulburn-Murray Water to fill one of the region's main storages, ahead of schedule.

GMW has announced it's been able to divert additional water into the Waranga Basin, north of Nagambie, after rainfall stemmed irrigation demand and saw increased river flows in the Goulburn catchment.

Additional water was diverted during April and May.

The Basin stands at 371,623megalitres, or 85.95pc full, more than double what is was, last year.

Achieving the early milestone highlighted two months of increased rainfall downstream of Eildon, with the highest flows seen in 10 years, estimated at around 5000 megalitres per day, in June.

GMW Water Resources manager Mark Bailey said the water would now be held in storage, until the next irrigation season began on August 15.

"This is exactly what we like to see at this time of year, bringing benefits that are two-fold," Dr Bailey said

"It fuels confidence that we have water available for improved seasonal determinations in the Goulburn system when the season opens with a good likelihood longer-term determinations will exceed initial forecasting.

"It also means more water will reach the Murray system, which becomes a Victorian resource under the Murray-Darling Basin Authority accounting rules."

There were strong inflows downstream of the Goulburn Weir, through Murchison, and into Shepparton, from all the tributaries below Lake Eildon, such as the Acheron and Rubicon rivers as well as the Hughes and Sunday creeks.

Dr Bailey said since the last seasonal outlook, a more optimistic picture was viable for the

Goulburn system and the Murray system was improving.

"Between now and the start of August, we won't need to put any more water into Waranga Basin," he said.

"This means inflows for the Goulburn and ultimately the Murray rivers."

Dr Bailey also said Murray system would start 2020/21 with a seasonal determination of eight per cent of high-reliability water shares.

The Goulburn and Loddon systems began with a 35pc HRWS seasonal determination.

The Campaspe system would start 2020/21 with a seasonal determination of 32pc HRWS, while the Broken system would open on 17pc HRWS.

The Bullarook system would start 2020/21 with 0 per cent HRWS.

Mr Bailey said opening seasonal determinations are higher than last season in all systems, except the Bullarook, due to flows into the major storages in recent months.

"Flows into the major storages since the start of April have helped secure operating requirements for 2020/21 and enabled water to be allocated at the start of the new water year." Dr Bailey said.

"The catchments are wet and responding to rain."

This meant there was more likely to be runoff entering the storages when rain fell.

"We need the rain to continue over coming months to increase storage levels and the seasonal determinations," Dr Bailey said.

"The latest Bureau of Meteorology seasonal outlook slightly favours below-average rainfall across the catchment areas during July to September.

"The Bureau has issued a La Nina watch meaning the chance of a La Nina forming is around 50pc in late winter or early spring.

"La Nina events may support rainfall across southeast Australia."

The risk of spill was consistent with the June 2020 assessment.

Victoria's share of the volume in Lake Hume gives the Murray system about a 60 per cent risk of spill.

The risk of spill from Lake Eildon in the Goulburn system is about 20pc cent, and the risk of spill from Lake Eppalock in the Campaspe system is about 50pc.

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