River Murray operations 10-17 May 2017

19 May 2017

Welcome to our summary report on River Murray operations for the week ending 17 May 2017.

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

Rainfall and inflows

The week ending 17 May 2017 was mostly dry across the Murray–Darling Basin with only light to moderate patches of rain occurring throughout the week. Broad low pressure troughs located through inland eastern Australia and off the east Australian coast produced isolated showers and thunderstorm activity. This activity produced moderate falls in parts of southern and eastern New South Wales, eastern Victoria, and across large parts of the southern interior of Queensland.

Stream flows along the upper Murray tributaries changed very little this week as mostly dry conditions continued. The Mitta-Mitta River at Hinnomunjie Bridge decreased this week from 290 ML/day to 275 ML/Day. Flow along the upper Murray at Biggara remained steady at 350 ML/day. On the Ovens River, the flow at Rocky Point is now 490 ML/day, an increase from 450 ML/day earlier in the week. Widespread falls of 25-50 mm are forecast across much of the Basin over the coming week which may yield some rises in stream flows in upper catchments.

Total in storage

Total MDBA storage increased by 44 GL this week, and total active storage is now 5,385 GL (63% capacity).

River operations

  • At Dartmouth Reservoir, the storage volume decreased by 6 GL to 3,003 GL (78% capacity). The release from Dartmouth, measured at Coleman’s, temporarily increased to around 3,000 ML/day during the week for hydro power generation before returning to the current rate of 200 ML/day. 
  • At Hume Reservoir, the storage volume increased by 44 GL to 1,875 GL (62% capacity).  Releases from Hume have decreased steadily this week and are currently 900 ML/day.
  • Diversions from Lake Mulwala to the Yarrawonga Main Channel ceased on 15 May at the end of the irrigation season. The pool level at Lake Mulwala is currently 124.76 m AHD.  
  • The Murray–Darling Basin Authority confirms Lake Mulwala will not be drawn down this winter following receipt of the latest weed survey report. The results are consistent with our aim of keeping the lower basin around Mulwala and Yarrawonga relatively weed free for recreation. The Lake is sometimes lowered during the winter to expose the aquatic weed Egeria to air and frost in an attempt to limit its growth. While the survey showed an increase in Egeria in the mid and upper reaches of the Lake, it also revealed an increase in native species. With the overall abundance at low to medium levels, a lowering of the lake is not yet warranted. However, given the increase in Egeria, a lowering of Lake Mulwala in 2018 may be beneficial. MDBA will consider the Egeria situation along with other local and system-wide factors before advising of a final decision in the lead up to winter 2018.
  • The release downstream of Yarrawonga Weir was reduced to 3,500 ML/day during the week and is currently being maintained around this rate to meet environmental orders. This water is providing higher base flows during the period outside the irrigation season when dam releases have historically targeted minimum flow requirements along the Murray. The releases are expected to continue over coming weeks until inflows from the Kiewa and Ovens Rivers boost flows above this rate.

An autumn day at Lake Mulwala.
Photo: Peter Shaw, MDBA
An autumn day at Lake Mulwala.
  • Inflows to the Edward-Wakool system are now fluctuating in response to changes in river levels downstream of Yarrawonga Weir. Flow through the Edward River and Gulpa Creek offtakes has increased slightly and are currently around 560 ML/day and 180 ML/day respectively. At Stevens Weir flow downstream is currently 500 ML/day. Steven’s Weir is being gradually lowered to 3.8 m AHD and will vary between 3.8 and 4.0 m over winter to provide connectivity for fish in the Yallakool and downstream in the Wakool Rivers see the attached customer notice and the WaterNSW website for more information.
  • On the Goulburn River, the flow at McCoys Bridge is targeting 940 ML/day, with the water above the minimum flow of 350 ML/day being provided for the environment. An environmental flow pulse for the Goulburn River is planned to be undertaken in late June and more information will be provided in future weekly reports.  On the Campaspe River, the flow at Rochester has continued to gradually fall and is currently around 40 ML/day.
  • At Torrumbarry Weir, the pool is currently at the full supply level (FSL) of 86.05 m AHD. This weekend the pool level is expected to start decreasing. The level will be gradually reduced over the coming weeks to around the maximum planned lowering of 50 cm below FSL (for more information, visit the MDBA website). During the week, release downstream of the weir was decreased from around 3,400 ML/day to 3,300 ML/day before increasing to the current flow of around 4,000 ML/day. The flow downstream of Torrumbarry is forecast to remain relatively steady over the coming week. Diversions to the National Channel are currently around 320 ML/day.
  • Inflows from the Murrumbidgee River gradually reduced this week from 1,100 ML/day to around 400 ML/day.
  • At Euston Weir, the pool level is currently at FSL (47.60 m AHD). The flow rate downstream of the weir has decreased gradually to around 6,600 ML/day.
  • On the Darling River, the total storage volume in the Menindee Lakes increased by 9 GL and is currently 795 GL (46% capacity). This week the lakes have continued to receive modest inflows from the rainfall and subsequent stream flows generated in upstream catchments in March. A total of about 10 GL passed Wilcannia this week where flows have continued to recede. Releases from Menindee Lakes to the lower Darling River at Weir 32 are currently around 400 ML/day, which includes water for the environment.
  • Over the last week on the Darling at Burtundy, the flow has reduced slightly to around 300 ML/day.  Flows into the Great Darling Anabranch have decreased this week and are currently 400 ML/day. Flows will remain steady over the coming fortnight before reducing to 100 ML/day until approximately late June.
  • Lake Victoria’s storage decreased by 3 GL this week to a volume of 386 GL (24.40 m AHD, 57% capacity). MDBA is currently targeting a lake level of 24.5 m AHD (395 GL) for the end of May in accordance with the Lake Victoria Operating Strategy. This end of May limit is applied in years when water remains available to MDBA in Menindee Lakes or when reserves held for NSW are in excess of 1,000 GL. This strategy aims to protect the health of foreshore vegetation around the lake in order to minimise the impact on aboriginal cultural heritage. Flow to South Australia, increased this week to approximately 11,500 ML/day late before falling to 8,300 ML/Day. The flow downstream at Lock 1 has increased to around 10,900 ML/day and is likely to fall later in the week.
  • At the Lower Lakes, the 5-day average water level in Lake Alexandrina has increased slightly to 0.64 m AHD. Total barrage releases have averaged 2,400 ML/day this week through Mundoo, Tauwitchere and Goolwa barrages.  

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