River Murray operations 12-19 April 2017
21 April 2017
Welcome to our summary report on River Murray operations for the week ending 19 April 2017.
You can find the full weekly report under the River Murray system section of our website.
Rainfall and inflows
It has been relatively dry in the Basin over the past week. The most significant rain was confined to an isolated pocket in northern New South Wales in the Northwest Plains, where a total of 15 mm was recorded at Walgett on the Barwon River. The remainder of the Basin received little to no rainfall. Scattered patches of rain were recorded in Queensland, with 5 mm north of Toowoomba at Mount Kynoch. Canberra received a total of 4 mm. Little or no rain was recorded in Victoria or South Australia.
In response to this week’s drier weather, stream flows in the upper Murray tributaries have been receding. On the Mitta Mitta River at Hinnomunjie Bridge, the flow has decreased by around 250 ML/day, averaging around 300 ML/day. Flow in the upper Murray at Biggara decreased by about 200 ML/day, averaging almost 400 ML/day. Downstream of Hume Reservoir, the flow in the Kiewa River at Bandiana averaged around 600 ML/day. Flows in the King River were steady and, downstream, the Ovens River at Wangaratta averaged around 650 ML/day.
A north-west cloud band is currently travelling east across the continent and is predicted to reach the southern Basin in the coming days. Rainfall of 10 to 35 mm is forecast for Mildura on Thursday before the band moves further east towards Deniliquin on Friday. There is a chance of thunderstorms in affected areas.
Total in storage
Total MDBA storage decreased by 62 GL this week, with the active storage now 5,257 GL (61% capacity).
At this time of year, River Murray operations aim to maintain a balance between sufficient flows in the river to meet demand while also conserving as much water as possible in Dartmouth and Hume Reservoirs for use in coming years. Irrigation demand is expected to cut back with rainfall forecast for the coming days, and evapotranspiration rates reducing as temperatures cool. Hence, deliveries of inter valley transfer (IVT) water as well as releases from the Menindee Lakes and Hume Reservoir are being reduced.
- The storage volume at Dartmouth Reservoir increased by 3 GL this week to 2,930 GL (78% capacity). The release from Dartmouth, measured at Colemans, averaged around 200 ML/day.
- The Hume Reservoir storage volume decreased by 59 GL this week to 1,781 GL (59% capacity). Releases from Hume have decreased from 11,000 ML/day to 7,500 ML/day (on 20 April) as a result of decreases in downstream demand.
- Diversions from Lake Mulwala have fluctuated throughout the weak. Diversion to Mulwala Canal dropped to around 3,500 ML/day over the weekend before returning to around 4,000 ML/day on Wednesday. Yarrawonga Main Channel slightly declined from around 1,500 ML/day to 1,300 ML/day. Lake Mulwala is currently 124.78 m AHD. The release from Yarrawonga Weir has been reduced from 8,000 to 6,500 ML/day.
- On the Edward River system, the flow through the Edward Offtake was around 1,400 ML/day, with a slight reduction to 1,200 ML/day occurring towards the end of the week. Flow through the Gulpa Offtake averaged 300 ML/day. Diversions from Stevens Weir pool into the Wakool Main Canal have slightly reduced from around 800 ML/day to 650 ML/day. Downstream of Stevens Weir the release averaged around 800 ML/day.
- On the Goulburn River, the flow at McCoys Bridge has increased from 1,000 ML/day to around 1,540 ML/day due to the delivery of IVT water to the Murray. IVT from the Goulburn system is now being wound back in response to decreased irrigation demands. It is expected that Goulburn River flows will soon begin to recede towards 940 ML/day.
- Diversion from Torrumbarry Weir pool to National Channel has slightly reduced by 200 ML/day, averaging around 3,200 ML/day over the week. The release downstream of the weir has increased to around 3,800 ML/day as a result of higher flow from the Goulburn River. Forecast rainfall is expected to reduce demand from National Channel which will result in releases from Torrumbarry Weir increasing for the next few days. Beginning around mid-May, the level of the Torrumbarry Weir pool will be varied to a maximum planned lowering of 50 cm below full supply level (FSL).
- Environmental flows along the Murrumbidgee River have begun to decrease and the flow at Balranald has receded from around 2,000 ML/day at the beginning of the week to around 1,280 ML/day. This flow is expected to recede further over the coming weeks.
- At Euston Weir, the pool level is currently around 47.48 m AHD (12 cm below FSL). As part of the weir pool variability program it is expected that this level will reduce to around 20 cm below FSL over the coming days. The flow rate downstream of the weir has reduced from around 6,000 ML/day to around 4,800 ML/day. The flow is expected to be relatively steady in the coming week.
- On the Darling River, the total storage volume in the Menindee Lakes fell by 16 GL to the current volume of 815 GL (47% capacity). Releases from Menindee Lakes to the lower Darling River are currently around 1,100 ML/day at Weir 32 and will be gradually decreased to target a flow of 400 ML/day over the next few days. This release includes some environmental water aimed at maintaining cod habitat in the Lower Darling River. Releases from Lake Cawndilla have remained steady at around 1,100 ML/day for the fifth consecutive week as environmental flows continue to be released to the Great Darling Anabranch.
- At the junction of the Darling and Murray rivers at Wentworth, flows have decreased from 7,700 ML/day at the beginning of the week to 5,850 ML/day.
- Weir pool variability continues at Lock 7 and Lock 8. Lock 7 is currently 87 cm below FSL (21.23 m AHD) which is close to the maximum planned lowering of 90 cm below FSL. Lock 8 is currently 97 cm below FSL (22.63 m AHD), which is also close to the planned one metre below FSL.
- Lake Victoria’s storage increased by 9 GL this week to a volume of 334 GL (49% capacity). The flow to South Australia is currently around 5,400 ML/day and is expected to decrease further over the coming weeks. Downstream of Lock 1 flows are around 4,140 ML/day.
- At the Lower Lakes, the 5-day average water level in Lake Alexandrina has not changed, remaining at 0.57 m AHD. The average total barrage release remained low at around 2,000 ML/day. Releases are currently prioritised at Goolwa and Tauwitchere barrages.