River Murray operations 3-10 May 2017

12 May 2017

Welcome to our summary report on River Murray operations for the week ending 10 May 2017.

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

Rainfall and inflows

For the week ending 10 May 2017, the majority of the Basin experienced relatively dry conditions, with patches of moderate rain isolated to the north-east and south-east. On Sunday, a vigorous cold front and associated low pressure system tracked across south-eastern Australia, with showers and thunderstorms producing falls in southern Victoria. Moderate falls were recorded in the Victorian Alps, with 11mm recorded at Mount Hotham and 9mm recorded at Mount Buller. In the north-east, moderate falls were recorded across the New South Wales and Queensland borders. In Queensland, the most significant rainfall occurred west of Toowoomba in the Condamine-Balonne and Moonie catchments. Meandarra recorded 18mm of rainfall while 26mm was recorded outside of Moonie. In New South Wales 10mm fell at Lake Pindari in the Borders River Catchment.

Stream flows along upper Murray tributaries continued to recede this week following the dry weather. The Mitta Mitta River at Hinnomunjie Bridge saw a slight decrease in flow from 350 ML/day to around 300 ML/day. Similarly, flow along the upper Murray at Biggara fell from 400 ML/day to around 350 ML/day. On the Ovens River, flow at Rocky Point decreased from 530 ML/day to around 450 ML/day.

Total in storage

Total MDBA storage increased by 53 GL, with the active storage now 5,340 GL (62% capacity).

River operations

  • At Dartmouth Reservoir, the storage volume decreased by 1 GL to 2,938 GL (78% capacity). The release from Dartmouth, measured at Colemans, has remained at around 200 ML/day for the past fortnight.
  • At Hume Reservoir, the storage volume increased by 34 GL to 1,808 GL (61% capacity). Releases from Hume Reservoir averaged about 2,400 ML/day during the week.
  • Diversions from Lake Mulwala to the Mulwala Canal ceased during the week. Diversions peaked at around 1,500 ML/day on Monday before coming to a close on Tuesday. After temporarily ceasing diversions at the end of last week, Yarrawonga Main Channel diversions increased to 800 ML/day this week. Diversions through Yarrawonga Main Channel are expected to finish on the 15th of May. The pool level at Lake Mulwala is currently 124.71 m Australian Height Datum (AHD).
  • The release downstream of Yarrawonga Weir was reduced to 4,000 ML/day during the week and is currently being maintained around this rate to meet environmental orders. This water is providing higher base flows whilst tributary inflows are low, and during a period (outside the irrigation season) when dam releases are historically targeting minimum flow requirements along the River Murray. This is expected to continue over May and June unless inflows from the Kiewa and Ovens Rivers boost flows above this rate.
  • With the Edward and Gulpa offtake gates now clear of the water, inflows to the Edward-Wakool system can be expected to fluctuate in coming weeks in response to changes in river levels downstream of Yarrawonga Weir. In response to falling River Murray levels, flow through the Edward River and Gulpa Creek offtakes has reduced and is currently around 540 ML/day and 180 ML/day respectively. At Stevens Weir, diversions to the Wakool Main Canal continued at around 200 ML/day before ceasing on Monday. Releases downstream have receded to around 300 ML/day.
  • On the Goulburn River, the flow at McCoys Bridge is targeting 940 ML/day, with the water above the minimum flow of 350 ML/day, being provided for the environment. On the Campaspe River, the flow at Rochester has gradually fallen to 70 ML/day.
  • At Torrumbarry Weir, the pool remains at the full supply level (FSL) of 86.05 m AHD. In the coming weeks, as part of the weir pool variability program, the pool level is expected to be varied and fall to a maximum planned lowering of around 50 cm below the FSL (for more information, visit the MDBA website). Demands in the Torrumbarry irrigation district remain low and diversions to National Channel are around 530 ML/day. During the week, release downstream of the weir reduced from around 5,400 ML/day to 3,500 ML/day, and is forecast to remain relatively steady over the coming week.
  • Inflows from the Murrumbidgee River peaked at 1,570 ML/day at Balranald on the weekend in response to rainfall and subsequent reduction in demands over the past fortnight. The flow is expected to decrease over the coming week towards the minimum end of system target of about 300 ML/day.
  • At Euston Weir, the pool level is currently at FSL (47.60 m AHD). The weir pool has been gradually refilled to FSL over the week as higher flows arrived from upstream. Rather than holding the pool level low, surplus water resulting from the significant reduction in demand following rainfall late in April was stored to maximise water availability ahead of the 2017-18 season. The flow rate downstream of the weir has increased to around 9,500 ML/day.
  • On the Darling River, the total storage volume in the Menindee Lakes reduced by 3 GL and is currently 785 GL (45% capacity). The rate of fall of the lakes has been temporarily slowed by the arrival of residual flows following the rainfall in March. A total of about 12 GL passed Wilcannia this week where flows have peaked and are now receding. Releases from Menindee Lakes to the lower Darling River at Weir 32 are currently around 400 ML/day, which includes water for the environment.
  • Over the last week on the Darling at Burtundy, the flow has receded from around 580 ML/day to around 330 ML/day. NSW, in association with the Commonwealth Environmental Water Holder, has been releasing water into the Great Darling Anabranch since the beginning of February to improve connectivity with the River Murray. Flows into the Anabranch will now decrease as the releases from Cawndilla have been reduced to around 800 ML/day this week.
  • Lake Victoria’s storage increased by 22 GL this week to a volume of 389 GL (24.44 m AHD, 57% capacity). The storage will continue to rise over the coming weeks, however during May it will be limited to a maximum volume of 396 GL (24.5 m AHD) in accordance with the Lake Victoria Operating strategy. This end of May limit is applied in years when water remains available to MDBA in Menindee Lakes or when reserves held for NSW are in excess of 1,000 GL. This strategy aims to protect the health of foreshore vegetation around the Lake in order to minimise the impact on its aboriginal heritage. Flow to South Australia, increased this week with an average flow of 6,200 ML/day. As a result, downstream flows at Lock 1 have increased to around 6,100 ML/day.
  • At the Lower Lakes, the 5-day average water level in Lake Alexandrina has increased slightly to 0.62 m AHD. The average total barrage release varied between 1,000 ML/day and 2,300 ML/day throughout the week. Releases are currently prioritised at Goolwa and Tauwitchere barrages when conditions permit.

landscape view of the river where two rivers meet with an island in the middle. Trees angling in from the bank.
Great Darling Anabranch
Great Darling Anabranch. Photo courtesy of Sean Kelly, Commonwealth Environmental Water Office

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