River Murray operations 19-26 April 2017

28 April 2017

Welcome to our summary report on River Murray operations for the week ending 26 April 2017.

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

Rainfall and inflows

It was one of the wettest weeks across the southern Murray–Darling Basin this year with widespread totals between 25 and 100 mm accumulating from two major rain events that crossed the region. Rain was lighter and patchier further north in the Basin with conditions in the far north staying dry. The rain was associated with consecutive cloud bands that moved across from the north-west before a strong cold front generated further showers and dropped temperatures late in the week.

The highest weekly totals fell over the Victorian Alps and the NSW Snowy Mountains with several locations recording more than 100 mm. For example 156 mm fell at Mt Buffalo, and 117 mm at Mt Hotham. There were similarly large totals across central, northern and north-western Victoria including 120 mm at Echuca, 108 mm at Woomelang, 102 mm at Kyabram and 98 mm at Violet Town. Totals in southern and western NSW were also substantial and included 77 mm at Burtundy, 71 mm at Mathoura and 62 mm at Moulamein. Totals across the South Australian lower Murray region included 51 mm at Milang and 41 mm at Meningie.

Stream flows along upper Murray tributaries have risen following the rain with many gauges at their highest levels for around 2 to 3 months. On the Mitta Mitta River, the flow at Hinnomunjie bridge increased from around 300 to 1,200 ML/day. On the upper Murray at Biggara, flows have increased from 350 to 1,300 ML/day. On the Ovens River, flow at Rocky Point was averaging around 400-500 ML/day prior to the rain, but has since increased to almost 2,000 ML/day – a rate not observed at this gauge since early January. Similar flows are expected along the lower Ovens for a few days.

Total in storage

Total MDBA storage decreased 3 GL this week, with the active storage now 5,255 GL (61% capacity).

River operations

System operations

The impact of significant widespread rainfall on River Murray system operations during autumn has been clearly demonstrated this week. Many autumns are characterised by persistent dry weather across irrigation districts. This helps maintain water demands through until the end of the irrigation season. However in some years, such as this one, autumn rainfall along the Murray valley and neighbouring irrigation areas can supress water usage and significantly decrease transmission losses across the system. This is one reason why patterns of demand can often be difficult to predict from year to year.

With downstream requirements now greatly reduced following the rain, and the irrigation season now effectively finishing early, operations over the coming weeks will be focusing on reducing storage releases, reviewing operating plans and analysing possible scenarios and requirements for the winter-spring period that lies ahead. One element of this activity will be on-going reviews of Bureau of Meteorology rainfall outlooks. The latest outlook suggests a high likelihood of warmer and drier conditions across the Murray-Darling Basin during the coming 3 month period.

River operations

  • At Dartmouth Reservoir, the storage volume increased by 2 GL to 3,003 GL (78% capacity). The release from Dartmouth, measured at Colemans, was held at 200 ML/day throughout the week.
  • The Hume Reservoir storage volume decreased 15 GL this week and is currently 1,766 GL (59% capacity). Releases began the week at just under 10,000 ML/day but were subsequently decreased throughout the week ahead of and following the rain. The current release is just 1,600 ML/day and similarly low release rates are expected for the next few days.
  • At Lake Mulwala total diversions to the Mulwala Canal and Yarrawonga Main Channel decreased from around 5,400 ML/day to just under 1,000 ML/day. At this stage, diversions are not expected to increase to any great extent between now and the end of the irrigation season in mid-May. The pool level at Lake Mulwala is currently 124.88 m AHD and is likely to remain at similar levels in the coming days. The release downstream of Yarrawonga Weir was reduced to 6,500 ML/day at the beginning of the week. With falling demands downstream, releases are now expected to be gradually reduced over the coming week with a release of around 4,000 ML/day expected by early May.
  • Inflows to the Edward-Wakool system have remained fairly steady through the week, with around 1,200 ML/day flowing through the Edward River Offtake and 300 ML/day through the Gulpa Creek Offtake. At Stevens Weir, diversions to the Wakool Main Canal were also affected by the rain and have fallen from around 700 ML/day to less than 200 ML/day. This reduction and a decrease in overall losses resulted in a temporary boost to inflows into Stevens Weir. Some water was stored in the weir pool and releases downstream were increased to around 1,500 ML/day before decreasing to 900 ML/day. Downstream on the Wakool River, the flow at Kyalite has risen to an estimated 1,900 ML/day and is expected to increase above 2,000 ML/day during the coming week.
  • On the Goulburn River, flows at McCoys Bridge are now planned to be reduced with the cessation of the inter-valley transfer (IVT) order early in the week. However, rainfall has boosted flows along the Goulburn and flows at McCoys remain at around 1,600 ML/day and are expected to continue close to 1,500 ML/day during the coming days.
  • 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 have been significantly affected by the rain and diversions to National Channel have been decreased from around 3,000 ML/day to only 600 ML/day. This reduction has combined with local inflows to boost flows downstream in excess of previous expectations. The flow is currently at around 7,400 ML/day and is likely to remain above 7,000 ML/day for a few more days before receding.
  • Environmental flows in the Murrumbidgee River have continued to decrease. The flow at Balranald receded from around 1,200 ML/day at the beginning of the week to the current rate of around 500 ML/day. This flow is expected to recede to around 300 ML/day in the coming week.
  • At Euston Weir, the pool level is currently 47.41 m AHD (19 cm below FSL). As part of the weir pool variability program it is expected that the pool level will remain around 20 cm below FSL into May. Later in May, it is expected that the pool level will be varied further to a maximum planned lowering of around 40 cm below FSL. The flow rate downstream of the weir has increased to around 6,500 ML/day (Image 1, 2). The flow is expected to continue rising over the coming week to around 9,000 ML/day.
  • On the Darling River, the total storage volume in the Menindee Lakes remained steady and is currently 816 GL (47% capacity). 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. Releases, which commenced in mid-February, finally connected with the River Murray (downstream of Wentworth Weir) this week.

Euston Weir flows
Photo: Andrew Bishop, MDBA
A recent view of Euston Weir, where flow rates are set to increase in coming days.
  • At the junction of the Darling and Murray rivers at Wentworth, flows have increased to around 7,300 ML/day. Flows are expected to remain around this rate for much of the coming week before increasing.
  • Weir pool variability continues at Lock 7 and Lock 8. Lock 7 is currently 78 cm below FSL which is close to the maximum planned lowering of 90 cm below FSL. Lock 8 is currently 90 cm below FSL which is also close to the planned one metre below FSL.
  • Lake Victoria’s storage increased by 10 GL this week to a volume of 344 GL (51% capacity). The flow to South Australia is currently targeting around 4,500 ML/day and is expected to decrease further over the coming weeks. Downstream of Lock 1 flows are around 4,100 ML/day. 
  • At the Lower Lakes, the 5-day average water level in Lake Alexandrina has increased slightly to 0.59 m AHD. Barrage releases are continuing at low rates with releases currently prioritised at Goolwa and Tauwitchere barrages when conditions permit.

 


Tagged as

0 Comments

Add new comment

Leave a comment

Filtered HTML

  • Web page addresses and e-mail addresses turn into links automatically.
  • Allowed HTML tags: <a> <em> <strong> <cite> <blockquote> <code> <ul> <ol> <li> <dl> <dt> <dd>
  • Lines and paragraphs break automatically.

Plain text

  • No HTML tags allowed.
  • Web page addresses and e-mail addresses turn into links automatically.
  • Lines and paragraphs break automatically.
CAPTCHA
This question is for testing whether or not you are a human visitor and to prevent automated spam submissions.

Contact us

For news related enquiries:
media@mdba.gov.au

For all other enquiries:
engagement@mdba.gov.au

Postal address:
GPO Box 1801,
Canberra City, 
ACT 2601

By month