River Murray Ops Update – 13 February

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Free Flow ‎Friday, ‎13 ‎February ‎2015, ‏‎2:45:26 PM
River Murray Ops Update – 13 February
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Welcome to our weekly report of river operations on the Murray. This one covers the river week ending 11 February.

Rainfall and inflows
Conditions were hot and dry across the Basin this week, with most areas recording little or no rainfall. Almost the entire Murray valley from Albury to South Australia sweltered through a series of mid to high 30 degree days, and similar or hotter temperatures were also experienced throughout western NSW.

Highest weekly rain totals in Queensland included 23 mm at The Head and 20 mm at Derbyshire Downs. In NSW, 36 mm fell at Cooma and 14 mm at Young; whilst in Victoria, 7 mm was recorded at Nhill.

Stream flows in the upper tributaries continued receding this week, and are now down to their lowest point so far this summer. Upstream of Dartmouth Dam, the Mitta Mitta River at Hinnomunjie Bridge decreased from 220 ML/day to 180 ML/day. On the Upper Murray, the flow at Biggara receded from 330 ML/day to 290 ML/day; whilst on the Ovens River, the flow at Wangaratta fell to 140 ML/day before increasing back up to 170 ML/day.


 River operations
MDBA total storage decreased by 151 GL this week, with the active storage now 4,550 GL (54% capacity).

At Dartmouth Reservoir, the storage decreased by 29 GL to 3,081 GL (80% capacity). The release, measured at Colemans gauge, will be held around 3,600 ML/day over the coming week as water is transferred downstream to Hume Reservoir.

At Hume Reservoir, the storage volume decreased by 82 GL to 1,282 GL (43% capacity). Releases from Hume averaged 18,000 ML/day over the past week, but are expected to ease slightly in coming days due to the likelihood of storm activity and associated rainfall.

Diversions from the major irrigation offtakes at Lake Mulwala were steady this week at around 6,800 ML/day. The pool level in Lake Mulwala is currently 124.75 m AHD and the downstream release from Yarrawonga Weir is steady at 10,100 ML/day. Planning is underway to perform a lowering of Lake Mulwala in late autumn-winter (see media release). The draw down will allow routine testing of the weir structure, erosion control works on the lake foreshore, as well as an opportunity to manage the invasive water weed Egeria densa. Lowering the water level and subjecting the exposed weed to frost has proven in the past to be an effective method for controlling its spread within the weir pool.

On the Edward River system, the combined flow through the Edward River and Gulpa Creek offtakes is steady at around 1,900 ML/day. Diversions to Wakool Main Canal decreased this week from 950 ML/day to 750 ML/day, which led to a corresponding increase in the flow in the Edward River downstream of Stevens Weir, which rose from 2,400 ML/day to 2,600 ML/day.

On the Goulburn River, the flow at McCoys Bridge is 2,700 ML/day and rising as a pulse of water released from Lake Eildon makes its way into the Murray System. The pulse, which will be held at a peak of around 3,000 ML/day at McCoys Bridge for a week, is a combination of traded inter-valley transfer (IVT) water and environmental water.

At Torrumbarry Weir, diversions at National Channel are steady at 2,400 ML/day. The flow downstream of Torrumbarry is 6,600 ML/day and forecast to rise to around 8,000 ML/day in coming days as the Goulburn pulse passes downstream.

On the lower Murrumbidgee River, the flow at Balranald was reduced this week from 700 ML/day to 380 ML/day. This flow is expected to remain around 300 to 400 ML/day over the coming week as further IVT water is delivered. Downstream on the Murray at Euston, the flow is 6,900 ML/day and forecast to remain steady over the coming week.

Planning is underway for major works at Mildura Weir this coming autumn-winter (see media release). These works include refurbishment of the Lock 11 lock chamber, as well as repairs on the concrete weir trestleway and installation of six mechanised trestles. The works on the lock are planned to commence after Easter and will take three to four months, during which time the lock will be closed to boat traffic. The works on the trestleway are planned to commence around late-autumn and will require the weir pool to be fully drawn down for a period of up to 10 weeks. Further advice with more specific dates and details will be issued over coming months.

A small pulse of water is currently making its way down the upper Darling River, with the flow at Louth currently 300 ML/day. This flow has originated from the Culgoa and Warrego Rivers following widespread rain throughout southern Queensland in late December. Over the past week, the total storage at Menindee Lakes (currently managed by NSW) decreased by 8 GL to 130 GL (8% capacity). Releases from the lakes, measured at Weir 32, are 160 ML/day, whilst the flow downstream at Burtundy is estimated to be around 10 ML/day.

At Wentworth Weir, the flow is 6,000 ML/day and expected to reduce to around 5,200 ML/day over the coming week. The Wentworth weir pool is continuing to be held at around 10 cm above its full supply level of 30.80 m AHD to assist diverters within the weir influence pump water while there are low flows in the lower Darling.

At Lake Victoria, the storage volume has decreased by 32 GL to 381 GL (56% capacity). The daily flow to South Australia is targeting 9,400 ML/day. This is around 2,500 ML/day above the usual February entitlement flow rate due to the delivery of additional environmental water made available to sustain higher barrage releases into the Coorong.

At the Lower Lakes, the 5-day average water level in Lake Alexandrina decreased by 4 cm this week to 0.58 m AHD. This reduction in lake level was significantly influenced by the hot weather and increased evaporation experienced over South Australia in the past week. Barrage releases averaged around 2,300 ML/day for the week.
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