River Murray operations 5-12 July 2017

14 July 2017

Welcome to our summary report on River Murray operations for the week ending 12 July 2017.

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

Rainfall and inflows

Further rain was recorded this week in the northern and the southern parts of the Murray-Darling Basin. Throughout the week a series of cold fronts and surface troughs continued to track across southern Australia, resulting in widespread rain across the southern Basin. Troughs moving through inland Queensland also produced showers with light to moderate falls in the northern Basin.

Total in storage

MDBA total storage rose by 54 GL this week, with the active storage now 5,731 GL or 67% capacity.

River operations

  • At Dartmouth Reservoir, the storage volume increased by 7 GL to 3,026 GL (78% capacity). Releases from Dartmouth, measured at Colemans gauge, continued at the minimum flow rate of 200 ML/day.
  • At Hume Reservoir, the storage increased by 51 GL to 2,189 GL (73% capacity). Increases to Hume storage are continuing to be driven by the consistently high releases from the Snowy Hydro Scheme and were boosted further this week by tributary inflows in response to recent rainfall. Inflows to Hume averaged around 9,000 ML/day this week compared with the average inflow of 7,400 ML/day in June when conditions were very dry. The release from Hume varied between the minimum release rate of 600 ML/day and 3,500 ML/day. Releases above the minimum will continue in order to meet winter environmental flow targets in the Murray downstream at Yarrawonga Weir. Since 1 June 2017 around 60 GL of water has been release on behalf of the environmental water holders to protect winter base flows downstream in the River Murray. Over the coming weeks releases from Hume Dam will vary to mimic natural flow conditions downstream of Yarrawonga up to 10,000 ML/day (channel capacity). This water is being released on behalf of the Commonwealth Environmental Water Holder for the purpose of providing environmental benefits all the way to the Murray mouth in South Australia.
  • At Yarrawonga Weir, the pool level is 124.77 m AHD. If conditions in the irrigation districts remain dry, diversions are expected to commence later in July in order to refill channels in preparation for the start to the irrigation season. Releases from the weir increased during the week to target 5,500 ML/day.
  • Downstream of Yarrawonga Weir, the regulators into the Barmah-Millewa forest were opened this week (see photos below). Traditionally these regulators were only opened when river flows downstream of Yarrawonga would result in the Barmah Choke channel capacity being exceeded. This new operation will provide connectivity between the river and the floodplain in winter and into spring when river flows are below channel capacity. This will benefit native fish and improve the transfer of valuable nutrients from the floodplain to the river to increase productivity. The small additional water loss associated with undertaking this action is being debited from water accounts held by the environmental water holders.

Mary Ada regulator. Photo Ali Borrell, NSW NPWS.
Water flowing through Mary Ada regulator into the Millewa forest. Photo courtesy of Ali Borrell, NSW NPWS.

Gulf regulator into the Barmah forest. Photo Keith Ward, GBCMA.
Water flowing through Gulf regulator into the Barmah forest. Photo courtesy of Keith Ward, GBCMA.
  • On the Edward River system, the gates at Edward and Gulpa Offtakes remain raised clear of the water. Flows through the Edward and Gulpa offtakes are currently 650 ML/day and 200 ML/day respectively and will continue to vary over the winter period in response to river level fluctuations in the Murray at Picnic Point. At Stevens Weir, the pool level is around 4.0 m (local gauge) and will vary between 3.8 m and 4.0 m over winter to provide connectivity for fish and protect instream habitat in the Colligen and Yallakool Creeks and downstream in the Wakool River. The release downstream of the weir averaged 420 ML/day.
  • On the Goulburn River, the flow at McCoy’s bridge eased to 7,400 ML/day. Flow at McCoy’s bridge is expected to continue to recede over the coming week as environmental releases continue to be reduced. The environmental flows in the Goulburn River have been planned by the Goulburn Broken CMA. More information can be found on the GMW factsheet and the Goulburn Broken CMA website.
  • On the Campaspe River, there is a small environmental flow passing Rochester at a rate of around 200 ML/day.
  • At Torrumbarry the weir pool level is 85.7 m AHD which is 35 cm below the full supply level (FSL) in accordance with the weir pool variability program. The weir will be gradually raised during July to around 86.0 m AHD (5 cm below FSL). Diversions into National Channel continued at around 420 ML/day to maintain winter base flows along Gunbower Creek for the benefit of native fish. Release downstream of Torrumbarry Weir averaged 11,800 ML/day. Flow downstream of Torrumbarry will recede over the coming week as inflows from the Goulburn River reduce.
  • Inflow from the Murrumbidgee River averaged 1,200 ML/day this week. Environmental agencies are planning to deliver a ‘river fresh’ along the Murrumbidgee River and Yanco Creek systems starting later in July. The fresh includes targeting a flow rate of around 20,000 ML/day at Wagga Wagga which aims to improve the health of wetlands along the mid-Murrumbidgee River as well as deliver instream benefits throughout the mid and lower Murrumbidgee River system. This event is expected to deliver significant inflows, at within-channel rates, to the Murray in August. Further environmental benefits will accrue as the flows are passed down the Murray to South Australia.
  • At Euston weir, the pool level is currently 47.22 m AHD (38 cm below FSL). The pool level is expected to be varied over the coming weeks, also as part of the weir pool variability program. The release downstream of Euston weir has increased and is currently around 11,100 ML/day. Further increases are expected over the coming week as environmental flows from the Goulburn move down the system.
  • Downstream of Euston at Hattah Lakes, pumping of environmental water into the lakes has increased to the pump capacity of around 1,000 ML/day. Pumping around this rate is expected to continue until early October 2017. Delivery of this water will build upon the ecological outcomes resulting from the natural flooding that occurred in 2016, and continue to improve the ecological health of this wetland system.
  • On the Darling River, the total storage volume in the Menindee Lakes decreased by 4 GL and is currently 767 GL (44% capacity). Inflows to the lakes are continuing at low rates, with the daily flow, measured at Wilcannia, around 500 ML/day. Releases from Menindee Lakes to the lower Darling River at Weir 32 are currently 400 ML/day. This is above the normal minimum of 200 ML/day at this time of year. The additional water is being released on behalf of environmental water holders to benefit native fish in the lower Darling River.
  • At the junction of the Darling and Murray rivers at Wentworth, flow has increased to 7,600 ML/day. Downstream of the weir, inflows from the Great Darling Anabranch have reduced to less than 50 ML/day.
  • At Locks 9, 8 and 7, the pool levels are currently 3 cm, 96 cm and 21 cm below FSL respectively. Pool levels are varied to help restore a more natural wetting and drying cycle to riverbanks and adjacent wetlands within the influence of the weir pool. Lock 7 was raised to around 20 cm below FSL this week to assist in the upstream passage of vessels attending the Wentworth Junction Rally.
  • At Lake Victoria, the storage volume decreased by 1 GL and is currently 423 GL (62% capacity). Over the coming months MDBA will manage the filling of Lake Victoria in line with the Lake Victoria Operating Strategy. The strategy aims to maximise water security whilst minimising the impact on vegetation and aboriginal cultural heritage sites around the lake.
  • Flow to South Australia increased to 7,700 ML/day and will increase further to target around 10,500 ML/day by the coming weekend as additional environmental water is delivered. Whilst flow to South Australia is higher, South Australia’s Department of Environment, Water and Natural Resources (DEWNR) is planning to undertake modest weir pool lowerings of 8 cm (within normal operating ranges) at Locks 2, 5 and 6 during July for ecological benefits. Further information can be found at DEWNR’s WaterConnect website.
  • At the Lower Lakes, the 5-day average water level in Lake Alexandrina rose by 2 cm to 0.72 m AHD. Releases through the barrages averaged around 2,600 ML/day this week. Barrage operations in recent weeks have been made more difficult due to higher tides, ocean swells and reverse flow conditions that typically become more frequent as winter progresses. However, suitable conditions allowed a pulse of over 6,000 ML/day to be released early in the week. A key objective of this pulse was to provide an attractant flow for pouched lamprey which characteristically migrate upstream at this time of year to breed.

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