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River Murray operations 26 April to 3 May 2017

Welcome to our summary report on River Murray operations for the week ending 3 May 2017.

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

Rainfall and inflows

Most of the rain recorded this week fell along the Great Dividing Range due to a surface trough and cold front at the start of the week. Light falls were also recorded along the southern divide and in the north of the basin later in the week. In Queensland, the highest weekly totals included 22 mm at Yangan and 19 mm at Wallangarra in the Darling Downs. In NSW, 20 mm was recorded at Glen Innes airport and Inverell in the northern tablelands and 17 mm at Woolbrook on the northwest slopes. In Victoria, the highest totals included 21 mm at Mount William in the Wimmera and 18 mm at Mount Hotham AWS in the northeast.

Stream flows along upper Murray tributaries receded this week. On the Mitta Mitta River, the flow at Hinnomunjie bridge decreased from around 1,350 to 380 ML/day. On the upper Murray at Biggara, flows reduced from 1,600 to 420 ML/day. On the Ovens River, flow at Rocky Point decreased from around 2,200 to 570 ML/day.

April 2017 Summary

April was a wet month across much of the southern Murray-Darling Basin with above-average rainfall recorded in Victoria, South Australia and south western New South Wales . Of particular significance, above-average rainfall along much of the River Murray resulted in renewed tributary inflows and reduced irrigation demands. Below-average rainfall was recorded in parts of central NSW and the far north of the basin in Queensland.

April rain map
Source: Bureau of Meteorology
Murray-Darling Basin rainfall deciles for April 2017

Following an exceptionally warm March, temperatures during April were mostly closer to average. Broadly speaking, mean daily maximum temperatures were below average in the northeast and close to average across the remainder of the basin, while mean daily minimum temperatures were above average in the southwest and mostly close to average across the remainder of the basin.

River Murray system inflows during April totalled around 209 GL, which is above the month’s long-term median of 174 GL. In comparison with the historical record since 1891, only about 35% of previous monthly totals for April have been higher than the inflows observed in April 2017.

Total in storage

Total MDBA storage increased by 34 GL this week, with the active storage currently 5,289 GL (62% capacity). This is close to the long-term average for this time of year (Figure 1).

River operations

  • At Dartmouth Reservoir, the storage volume increased by 7 GL to 3,010 GL (78% capacity). The release from Dartmouth, measured at Colemans, was held at 200 ML/day throughout the week.
  • The Hume Reservoir storage volume increased by 31 GL this week and is currently 1,797 GL (60% capacity). Releases decreased during the week to 900 ML/day due to reduced demand and higher inflows from the Kiewa and Ovens Rivers. The release subsequently increased again to 2,000 ML/day late in the week as tributary inflows receded, and is expected to remain around this rate over the coming week.
  • At Lake Mulwala diversions to the Mulwala canal remained low, averaging around 650 ML/day. Diversions at Mulwala canal are expected to cease on Monday 8 May. At Yarrawonga Main Channel, diversions have currently ceased and are unlikely to increase significantly before the end of their irrigation season on 15 May. The pool level at Lake Mulwala is currently 124.85 m AHD and is likely to gradually reduce toward 124.7 m AHD in the coming week. The release downstream of Yarrawonga Weir was reduced to 4,000 ML/day during the week and is currently being maintained around this rate using environmental water. This environmental 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.  The use of environmental water to vary the release at around 4,000 ML/day is expected to continue over May and June unless inflows from the Kiewa and Ovens Rivers boost flows above this rate.
  • The Edward and Gulpa offtake gates were lifted clear of the water during the week.  Inflows to the Edward-Wakool system can be expected to fluctuate in coming weeks in response to any 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 790 ML/day and 220 ML/day respectively. At Stevens Weir, diversions to the Wakool Main Canal have remained low, averaging 180 ML/day, and are expected to cease on Monday 8 May. With inflows to the system reducing, water stored in the weir pool will be used to help meet demands over the final few days of the irrigation season. In response, the pool level is likely to be variable over the coming week. Releases downstream have fluctuated, averaging around 820 ML/day, and are expected to reduce to around 300 ML/day in the coming week. Inflows of around 600 ML/day from Billabong Creek are boosting flows on the Edward River at Moulamein to around 1,450 ML/day. On the Wakool River, the flow at Stoney Crossing has risen to 920 ML/day and is expected to remain around this rate during the coming week.
  • On the Goulburn River, flows at McCoys Bridge eased to around 1,300 ML/day. The flow is expected to reduce further, to around 940ML/day, in the coming week. On the Campaspe River, the flow at Rochester peaked at around 470 ML/day in response to rainfall last week and is currently 80 ML/day and receding.
  • At Torrumbarry Weir, the pool remains at the full supply level (FSL) of 86.05 m AHD. Beginning around mid-May, as part of the weir pool variability program, the weir pool is expected to be varied 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 600 ML/day. The release downstream of the weir reduced during the week from a peak of around 8,200 ML/day to the current rate of 6,100 ML/day, and will continue to recede over the coming week.
  • Inflows from the Murrumbidgee River are rising in response to reduced demands resulting from recent rainfall. The flow at Balranald is currently 720 ML/day. The flow will continue to rise and is likely to remain above 1,000 ML/day over the coming week.
  • At Euston Weir, the pool level is currently 47.41 m AHD (19 cm below FSL). The pool level is now planned to be gradually refilled to the full supply level over the coming week as higher flows travel downstream. Rather than holding the pool level low, surplus water resulting from the significant reduction in demand following rainfall late in April will be stored to maximise water availability ahead of the 2017-18 season. The flow rate downstream of the weir has increased to around 8,900 ML/day and is expected to peak above 10,000 ML/day in the coming week.
  • On the Darling River, the total storage volume in the Menindee Lakes reduced by 27 GL and is currently 789 GL (46% capacity). Inflows at low rates are continuing following rainfall in March. Earlier in the week, the Darling River peaked at Bourke at around 4,800 ML/day and later at Louth at around 2,900 ML/day. Releases from Menindee Lakes to the lower Darling River are currently around 400 ML/day. 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 as environmental flows continue to be delivered to the Great Darling Anabranch. Downstream on the Darling at Burtundy, the flow is gradually receding and is currently 500 ML/day
  • At the junction of the Darling and Murray rivers at Wentworth the flow is currently 8,200 ML/day and rising. Downstream of the weir, inflows from the Great Darling Anabranch are contributing around 800 ML/day.
  • At Lock 7 and Lock 8 the pool levels are currently 82 cm and 93 cm (respectively) below their FSL as part of the weir pool variability program. These pool levels are also now planned to be gradually refilled to their full supply levels over the next two weeks as higher flows travel downstream. Raising the weir pool levels will allow replenishment flows to the Potterwalkagee Creek at Lock 8 and the upper Lindsay River at Lock 7.
  • Lake Victoria’s storage increased by 23 GL this week to a volume of 367 GL (24.2 m AHD, 54% 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 strategy aims to protect the health of foreshore vegetation around the Lake in order to minimise the impact on its aboriginal heritage. The flow to South Australia is currently targeting around 4,600 ML/day and is expected to increase over the coming weeks. Downstream of Lock 1 flows are around 4,400 ML/day. 
  • At the Lower Lakes, the 5-day average water level in Lake Alexandrina has increased slightly to 0.61 m AHD. Barrage releases are continuing at low rates when conditions permit.
Homepage Image: 
April rain map
Site Context: 
Grid View Image: 
April rain map
Published on: 
Friday, May 5, 2017

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