River Murray operations 22 February to 1 March 2017

3 March 2017

Welcome to our summary report on River Murray operations for the week ending 1 March 2017.

You can find the full weekly report under the River Murray system section of our website.

Rainfall and inflows

A ridge of high pressure over southern Australia maintained dry conditions across the southern Murray-Darling Basin. No rainfall was recorded in South Australia, Victoria and the majority of New South Wales. Light to moderate falls were recorded along the New South Wales ranges, with 26 mm recorded at Guyra in the Northern Tablelands. This week’s highest total of 64 mm fell at Mungallala in Queensland’s Warrego catchment. The BoM is forecasting dry conditions to persist over the southern Basin for at least the next week.

The dry conditions resulted in steady recessions in the upper Murray tributaries. On the Mitta Mitta River, the flow at Hinnomunjie Bridge eased from 280 ML/day to 210 ML/day, while the upper Murray at Biggara receded from near 250 ML/day to 150 ML/day. On the Ovens River, the flow at Wangaratta continued to recede, falling from 1,050 ML/day to 550 ML/day.

February 2017 Summary

In general, February 2017 delivered below average rainfall and another month of well above average temperatures across Queensland and New South Wales. The upper Murray catchments had near average rainfall, while parts of western Victoria and the South Australian Riverland had above average falls. The above average falls in South Australia follow on from above average rain in January, December 2016 and a wet spring in 2016.  Overall, the Bureau of Meteorology reports that area-averaged rainfall across the Murray-Darling Basin in February was 16.9 mm, well below the mean for this time of year (equal 15th lowest out of 118 records).

River Murray System inflows during February (excluding Snowy Scheme, Darling River and managed environmental flows) totalled around 130 GL, which is below the month’s long-term average of about 190 GL.

As previously mentioned, temperatures were well above average across much of the northern Basin in February 2017. The entire Queensland section of the Basin had ‘Very Much Above Average’ or ‘Highest on Record’ mean temperatures, continuing on from the heatwave conditions experienced in January. Mungindi, on the Barwon River, experienced 15 consecutive days of 40°C or above during January, eclipsing the previous record of 8 consecutive days. The bulk of the southern-Basin experienced near average temperatures in February.

Estimated evaporation losses from MDBA storages for February 2017 are in the reported in the full weekly report.

Total in storage

Total MDBA storage decreased 123 GL this week, with the active storage now 6,152 GL (72% capacity).

River operations

System Operations

In January and February, demands and losses along the Murray system have been lower than planned for, meaning that more water has been arriving at Lake Victoria than expected. In order to reduce the volume of water at risk of being spilled from Lake Victoria over the coming winter/spring, deliveries, including from tributary inter valley transfer (IVT) and from Menindee lakes, continue to be reduced.  However, the Bureau of Meteorology’s latest outlook for autumn suggests rainfall is likely to be below average and temperatures are likely to be warmer than average. This means demands and losses may be high during autumn, so that deliveries may need to be increased before the end of the irrigation season. Updates will be provided in coming weeks as flow rates across the system are adjusted in response to the observed and forecast weather and demands.

River Operations

  • At Dartmouth Reservoir, the storage volume increased by 1 GL to 3,000 GL (78% capacity). The release from Dartmouth, measured at Colemans, remains at 300 ML/day. Releases are planned to increase next week to mimic a small natural pulse that will provide water quality and ecosystem function benefits in the Mitta Mitta River downstream of Dartmouth Dam. See our flow advice. The water is provided for by MDBA’s minimum release provisions for Dartmouth Dam.
  • The Hume Reservoir storage volume decreased 71 GL this week to 2,296 GL (76% capacity). Releases averaged around 13,000 ML/day before being increased to 14,700 ML/day to supply increasing downstream irrigation demands. Further increases are likely in the coming days.
  • Diversions from Lake Mulwala increased during the week. Diversion to Mulwala Canal was hovering around 3,800 ML/day before increasing to near 4,700 ML/day, while diversion to Yarrawonga Main Channel has averaged near 1,500 ML/day. Demands from both irrigation channels are expected to increase further in the coming days. The Lake Mulwala pool level has averaged near 124.76 m AHD this week and may lower over the coming days before additional water arrives from Hume Dam. Releases downstream of Yarrawonga Weir had been targeting 9,500 ML/day but are now being gradually reduced back to 8,000 ML/day over the next few days as environmental orders reduce.
  • Inflows to the Edward-Wakool system have remained relatively steady this week. The Edward River and Gulpa Creek off-takes are currently targeting around 1,550 ML/day and 350 ML/day respectively, resulting in a flow downstream at Toonalook near 1,800 ML/day. At Stevens Weir, the flow target continues at the normal summer minimum of 600 ML/day, while on the Wakool River, the flow at Stoney Crossing has remained near 700 ML/day.
  • Back on the Murray downstream of the Edward River Offtake, the river height at Picnic Point has fallen after peaking near channel capacity on Thursday. The river height is expected to fall further over the coming week.
  • The Goulburn River at McCoys Bridge has risen from near 1,100 ML/day to 1,900 ML/day, and is forecast to increase towards 4,500 ML/day by next week. This flow pulse is being provided by environmental water from the Commonwealth Environmental Water Holder and will combine with a flow pulse in the Murray (originating from higher Yarrawonga releases over the past fortnight) to promote movement and dispersal of native fish from downstream of Torrumbarry to upstream reaches, primarily into the Goulburn River. Delivery of inter valley transfer (IVT) water from the Goulburn to the Murray continues, albeit at slightly lower rates than in February.
  • Diversions from the Torrumbarry weir pool to National Channel have increased from 2,200 ML/day to about 2,600 ML/day, and are expected to increase to around 3,800 ML/day in the coming week to meet autumn irrigation needs. The release downstream of Torrumbarry Weir has averaged around 6,100 ML/day and is expected to rise in the coming days as higher Goulburn flows arrive.
  • On the Murrumbidgee River at Balranald, flows continue at rates above the normal end of system target due to the on-going delivery of IVT to the Murray. The flow is currently around 1,750 ML/day, and is expected to recede throughout this coming week.
  • At Euston, the weir pool level is currently 16 cm below the full supply level (FSL). As part of the on-going program of weir pool variation along the mid Murray weirs, the pool level will be varied over the coming months to restore a more natural wetting and drying cycle to benefit the riverine environment. During known recreational events such as the up-coming Robinvale Classic water ski race in March, operations will target a level close to FSL to help with local community requirements as much as possible. The release downstream of the weir has averaged around 6,900 ML/day.
  • On the Darling River system, total storage in the Menindee Lakes fell by 52 GL to a storage volume of 1,077 GL (62% capacity). The release from Menindee Lakes, measured at Weir 32 is currently 2,900 ML/day and is being gradually lowered to 2,250 ML/day in response to reduced River Murray system demands. At the Lake Cawndilla outlet, WaterNSW continues to release near 1,200 ML/day to deliver environmental water to the Great Darling Anabranch using water allocations made available by the Commonwealth Environmental Water Holder.
  • Downstream at the confluence of the Darling and Murray, the flow at Wentworth has slowly fallen to 7,900 ML/day and is likely to remain near this flow rate for the coming week. At Lock 7, the weir pool level has been lowered back to around 50 cm below FSL (21.7 m AHD) after being temporarily raised.
  • The Lake Victoria storage volume remained steady at 453 GL (67% capacity) this week but will begin to fall again over the coming weeks. The flow to South Australia averaged around 8,000 ML/day during the week and is likely to remain near this rate until next week. Further downstream at Lock 1, the flow has eased to 5,300 ML/day.
  • At the Lower Lakes, the 5-day average water level in Lake Alexandrina fell 2 cm to 0.73 m AHD. All fishways remain open and are providing fish passage between Lake Alexandrina and the Coorong. The average total barrage release was around 3,000 ML/day.

Picnic Point
Source: Ben Berry, NSW DPI.
The Murray at Picnic Point has fallen after peaking near channel capacity this week.

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