River Murray operations 25 January to 1 February 2017

3 February 2017

Welcome to our summary report on River Murray operations for the week ending 1 February 2017.

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

Rainfall and inflows

A ridge of high pressure maintained hot and dry conditions across the southern Basin for much of the week before a weak cold front provided respite from high temperatures. In the north of the Basin conditions remained very hot, with a low pressure trough delivering patchy falls in Queensland and parts of New South Wales. In Queensland, 64 mm was recorded on the Maranoa River at Springfield, while the heaviest falls in NSW were in the Northern Tablelands where 62 mm fell at Glenn Innes. Negligible rainfall was recorded in Victoria and South Australia. This week’s hot and dry conditions reduced stream flows in the upper Murray tributaries. For example, on the Mitta Mitta River, the flow at Hinnomunjie Bridge fell from 550 ML/day to 380 ML/day while Biggara, on the upper Murray, receded from around 430 ML/day to near 290 ML/day. On the Ovens River at Wangaratta, the flow continued to recede, falling from 1,300 ML/day to 850 ML/day.

Forecast rainfall      

The eight day forecast for the southern basin shows a widespread rain event throughout Victoria, South Australia and along much of the Murray, with falls in excess of 25 mm. Temperatures along the Murray system are forecast to vary between the high 20s and high 30s over the next week.

January 2017 Summary

Across the Basin as a whole, rainfall was near average in January 2017. The Bureau of Meteorology (BoM) reports that overall the Basin recorded area-averaged rainfall for January of 38.3 mm, which is close to the long-term median for January. Of particular note, monthly rainfall was again above-average in South Australia, following on from above average rain in December 2016 and a wet spring in 2016. Rainfall in the upper Murray catchments was generally near average or above average in January 2017.

River Murray System inflows during January (excluding Snowy Scheme, Darling River and managed environmental flows) totalled around 260 GL, which is slightly above the month’s long-term average around 250 GL.

Temperatures were well above average across the Basin in January 2017. Areas of southern Queensland stretching down into northern New South Wales and south along the New South Wales ranges experienced “Highest on Record” mean January temperatures. Temperatures in much of Queensland and New South Wales have regularly exceeded 40 degrees Celsius and often exceeded 45 degrees Celsius. These hot and mostly dry conditions have contributed to very high evaporation rates from the Menindee Lakes. Estimated evaporation losses from MDBA storages for January 2017 are contained in table 1 the full report.

Total in storage

MDBA total storage decreased by 137 GL, with the active storage currently 6,686 GL (78% capacity).

River operations

System Operations

Summer demands and losses along the Murray system have been lower than planned for, meaning that more water has been arriving at Lake Victoria than expected. This allows for deliveries in February, including from tributary inter valley trade (IVT) and from Menindee lakes to be reduced.  Updates will be provided in coming weeks as flow rates across the system are adjusted in response to the observed and forecast weather and demands. For example, if the forecast rainfall eventuates, demands along the Murray are expected to decrease allowing for possible further reductions in deliveries to Lake Victoria.

River Operations

  • Dartmouth Reservoir’s storage volume increased 2 GL this week to 3,024 GL (78% capacity). The release, measured at Colemans gauge, remained at 290 ML/day.
  • The Hume Reservoir storage volume fell by 69 GL this week to 2,539 GL (84% capacity), with the release averaging around 12,750 ML/day. Downstream of Hume, the Kiewa River has provided an average of around 900 ML/day to the Murray.
  • Higher than anticipated diversions from Lake Mulwala resulted in the pool level falling to 124.72 m AHD early in the week before rising again over the Australia Day weekend. Diversions to Yarrawonga Main Canal and Mulwala Canal have averaged 1,450 ML/day and 3,370 ML/day respectively over the past week.
  • The release from Yarrawonga Weir has remained steady near 8,000 ML/day and would be lower without deliveries of environmental water. Currently, 1,000 ML/day of environmental water is being released for large bodied native fish and continued bird breeding in the Barmah-Millewa forest and sites further downstream. The target flow around 8,000 ML/day will continue in February. These releases are lower than experienced over the last few years at this time of year due to downstream demands being supplemented by water from the Goulburn, Campaspe and Murrumbidgee Rivers and Menindee Lakes. This allows more water to be conserved in the major storages of Hume and Dartmouth than would otherwise have been the case.
  • On the Edward River system, the flow through the Edward offtake has continued to average close to 1,600 ML/day. The Gulpa Creek offtake has been reduced to 450 ML/day and is expected to lower to around 400 ML/day later in the week. Downstream at Stevens Weir the flow has fluctuated around 600 ML/day and is expected to continue around this rate over the coming week.
  • Flows in the Broken Creek at Rice’s Weir have averaged 300 ML/day. The Goulburn River at McCoys Bridge has gently receded to 1,350 ML/day and is expected to gradually fall to around 1,200 ML/day this coming week.
  • At Torrumbarry Weir, diversions to National Channel have remained close to 2,200 ML/day with a portion of this water provided to support Murray Cod in Gunbower Creek. Downstream of Torrumbarry Weir the flow has reduced from 5,300 ML/day to around 4,650 ML/day and is expected to gradually fall to around 4,300 ML/day over the coming week.
  • On the lower Murrumbidgee River, deliveries of IVT to the Murray have resulted in the flow at Balranald increasing from 650 ML/day to near 2,000 ML/day this week. IVT deliveries are to persist throughout February. Further information on IVT in the Murrumbidgee system is available from WaterNSW.
  • At Euston, the flow has fluctuated around 6,000 ML/day and is expected to remain around this rate for the coming week. The lock at Euston remains closed due to repair works being undertaken on one of the upstream lock gates. Damage to the lock gate is more extensive than originally thought and repairs will likely take until mid-February to complete. In the coming weeks the Euston weir pool may be lowered below the Full Supply Level (FSL) as part of weir pool variability but will be returned to near FSL during important recreational times. Downstream of Euston the final volumes of water are returning to the Murrayfrom the Hattah Lakes following last year’s natural flooding which built upon earlier environmental watering.

Messenger Creek regulator
Source: Heather Peachey, MDBA.
Flows from Hattah Lakes returning to the Murray via Messengers Creek regulator.
  • On the Darling River, total storage at Menindee Lakes fell by 50 GL to a storage volume of 1,301 GL (75% capacity). Additional Dilution Flows to South Australia will cease once the total volume drops below 1,300 GL. The release at Weir 32 has targeted 5,000 ML/day this week and is to be gradually lowered to 4,000 ML/day over the coming days. For more information on Menindee operations see this media release.
  • At Wentworth, the flow has declined to around 7,200 ML/day and may slowly rise over the coming days. The weir pool at Lock 9 was lowered by 100 mm on Wednesday 25 January to investigate a structural issue at Carrs No.2 regulator. The weir pool will remain lowered while the issue is being investigated. Updates will be provided as information comes to hand. Lock 8 weir pool continues to be lowered to target 50 cm below FSL. It is currently 23 cm below FSL. The lowering of Lock 7 weir pool by up to 50 cm is also underway and is currently around 44 cm below FSL.  Weir pool variability helps to restore a more natural wetting and drying cycle to riverbanks within the weir pool. More information on possible weir pool levels in the coming weeks is available on the MDBA website.
  • The storage volume at Lake Victoria fell 20 GL to 496 GL (73% capacity) with the releases from Lake Victoria averaging near 2,600 ML/day. The flow to South Australia averaged 10,500 ML/day this week and is expected to be gradually reduced throughout the remainder of February. This flow is largely made up of South Australian entitlement and additional dilution flow, with a smaller proportion of environmental water being delivered to South Australia.
  • Recent high flows to South Australia helped to improve connectivity between the Coorong and the ocean however they did not scour as much sand at the Murray Mouth as the longer period of high flows in 2010-11. Now that the high flows have passed through the river system, releases over the barrages are being reduced and dredging has again resumed to ensure the Murray Mouth remains open – with only one dredge required at this stage. More information on the Murray Mouth and dredging conditions can also be found in South Australia’s River Murray Weekly Flow Report.

 


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