River Murray operations 22-29 March 2017

30 March 2017

Welcome to our summary report on River Murray operations for the week ending 29 March 2017.

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

Rainfall and inflows

Moderate to heavy rain fell across much of the eastern side of the Murray-Darling Basin this week. Isolated heavy falls were recorded in Queensland, the highest being 71 mm at Toowoomba. Rainfall was more widespread in New South Wales with this week’s highest total of 82 mm at Forbes, while Dubbo received 77 mm. In Victoria the heaviest falls were confined to the ranges where Falls Creek recorded 57 mm and Mt Buffalo 52 mm. Similar to last week, conditions in South Australia were dry.

Rain over the Murray catchments delivered only minor, short-lived rises to upper Murray tributaries throughout this week.  Hinnomunjie Bridge, on the Mitta Mitta River upstream of Dartmouth Reservoir, averaged around 300 ML/day this week. Biggara, on the upper Murray, averaged about 450 ML/day.  Downstream of Hume Reservoir, the Kiewa River at Bandiana fluctuated around 450 ML/day while rainfall in the Ovens catchment resulted in the flow in the Ovens River at Wangaratta rising from 380 ML/day to 720 ML/day, before gradually receding.  With no significant rainfall in the forecast, flows in the upper Murray tributaries are expected to recede over the coming week.

Total in storage

Total MDBA storage decreased by 121 GL this week, with the active storage now 5,563 GL (65% capacity).

River operations

System operations

Operations during recent weeks continue to focus on releasing sufficient water from storage to meet system demands and steer towards targets at key locations, including Lake Victoria; while also aiming to conserve water for next season. Actual releases and river flows will continue to be highly influenced by both forecast and observed weather and demand conditions. Current Bureau of Meteorology outlooks suggest warm and dry conditions are more likely during the autumn period, however uncertainty always remains and significant rain events always remain a possibility. These can alter prevailing conditions and change system trends quickly. With significant water able to be supplied from the Menindee Lakes and via trade deliveries from the Murrumbidgee and Goulburn valleys, release requirements from Hume Reservoir remain quite low compared to many other years.

This combination of factors may result in quite low and variable flows along the mid-reaches of the River Murray during coming weeks, including the Easter period (more in our media release). River users are therefore advised to maintain a close eye on conditions and keep up to date via the MDBA Weekly Report when planning recreational or other activities.

Current Operations

  • Rainfall over the past week resulted in the storage volume at Dartmouth Reservoir rising by 4 GL to 2,994 GL (78% capacity). The release from Dartmouth, measured at Colemans, remained at 300 ML/day throughout the week.
  • Storage in Hume Reservoir decreased 47 GL this week and is currently 1,995 GL (66% capacity). Releases from Hume were cut to 7,800 ML/day at the start of the week in anticipation of reduced downstream demands resulting from last week’s rainfall across the major irrigation districts. However, the release has since been increased to 18,400 ML/day to provide for re-emerging demands. Releases are likely to ease back over the next few days.
  • At Lake Mulwala diversions to Mulwala Canal and Yarrawonga Main Channel have increased considerably throughout the week after being subdued from last week’s rain. The diversion to Mulwala Canal fell to as low as 2,600 ML/day before rising to around 3,500 ML/day and is expected to increase further in the coming days. Diversions to Yarrawonga Main Channel more than doubled from 900 ML/day to 2,300 ML/day and may increase further. In response to last week’s reductions in demand the Lake Mulwala level temporarily rose to approximately 124.92 m AHD (marginally above the Full Supply Level of 124.90 m AHD), before falling away to as low as 124.69 m AHD as irrigation demands quickly escalated. Over the next day or two the pool level may fall further before returning to above 124.7 m AHD as additional water from Hume arrives.
  • The release downstream of Yarrawonga Weir started the week at 9,500 ML/day but has since been gradually reduced to 7,600 ML/day to help manage pool levels. Over the next couple of weeks the release is planned to average around 8,000 ML/day.
  • Inflows to the Edward-Wakool system have remained fairly steady throughout the week, with around 1,600 ML/day flowing through the Edward River Offtake and just under 350 ML/day through the Gulpa Creek Offtake. Diversion from the Stevens Weir pool into the Wakool Main Canal fell from near 1,300 ML/day to around 700 ML/day, but is expected to slowly increase this coming week. Downstream of Stevens Weir, the flow increased to near 1,100 ML/day before dropping back towards 600 ML/day.
  • On the Goulburn River, the flow at McCoys Bridge continues to slowly recede and has fallen from 2,900 ML/day to below 2,000 ML/day. This flow includes the tail end of an environmental delivery as well as a component of IVT water that continues to be delivered to the Murray. Flows will continue to recede over the next few days and are anticipated to be near 1,200 ML/day by early April.
  • Diversions from the Torrumbarry Weir pool to National Channel have increased from 2,800 ML/day to around 3,200 ML/day to meet rising irrigation demands. The downstream release increased from around 6,000 ML/day to 6,500 ML/day this week before receding to around 5,500 ML/day. The release is expected to recede further over this coming week as upstream inflows to Torrumbarry decrease and irrigation demands remain relatively high.
  • On the Murrumbidgee River at Balranald, flows have gradually risen over the week to 860 ML/day and are expected to continue rising into April as environmental water arrives.
  • Downstream on the Murray at Euston Weir, the pool level is currently 47.44 m AHD (16 cm below FSL) and will be further reduced to around 20 cm below FSL over the coming days as part of the weir pool variability program. The flow rate downstream of Euston has gradually risen from near 5,000 ML/day to 5,600 ML/day and is forecast to rise further over the next week.
  • In the northern Basin, rainfall during the last couple of weeks has resulted in some reasonably significant streamflow responses along the upstream reaches of several tributaries. The Bureau of Meteorology has issued minor and moderate flood warnings for the Bogan and McIntyre Rivers, and with further rainfall forecast has now issued a Flood Watch for several valleys. However, responses have so far been fairly short in duration and at this stage it is unknown what volumes may make it down into the Barwon-Darling River in the coming weeks.
  • Downstream at the Menindee Lakes, the total storage volume decreased by 42 GL to 908 GL (52% capacity). The release from Menindee Lakes into the lower Darling River has been reduced to about 1,500 ML/day in response to reducing downstream requirements. Depending on weather conditions and forecast downstream demands, releases may be reduced further in April. At the Lake Cawndilla outlet, the release by NSW is continuing at around 1,100 ML/day primarily to deliver environmental water to the Great Darling Anabranch. These releases are expected to continue over the coming weeks.

e water flow
Source: Paul Brown, Murray-Darling Freshwater Research Centre.
The flow front progressing down the Great Darling Anabranch.
  • At the confluence of the Darling and Murray Rivers at Wentworth, flows have risen from around 5,700 ML/day to near 6,500 ML/day but may ease back over the coming days. Downstream at Lock 8, the weir pool level is currently 34 cm below FSL and over the next few weeks will be gradually lowered to around 1 metre below FSL. The downstream release has averaged around 4,600 ML/day this week.

Releases from Lock 8 have remained fairly steady over the past week.
Source: Alex Burgess-Norris, MDBA.
Releases from Lock 8 have remained fairly steady over the past week.
  • At Lock 7, after being raised back to FSL to provide a freshening flow into the Lindsay River, the weir pool level is currently 5 cm below FSL and is to be gradually lowered to around 90 cm below FSL over the coming weeks. This will result in diminished flows to the Lindsay River over the coming weeks, as would naturally occur at this time of year. Weir pool variability helps to restore a more natural wetting and drying cycle to riverbanks within the weir pool.
  • The Lake Victoria storage volume decreased by 35 GL this week to a storage volume of 340 GL (50% capacity) and will fall further in the coming week.
  • The flow to South Australia is currently near 9,700 ML/day, and above the normal March entitlement rate of 6,000 ML/day, due in part to the delivery of environmental flow pulses released from upstream storages several weeks’ ago. The flow to South Australia will fall towards 7,000 ML/day this coming week. Downstream at Lock 1, the flow has remained fairly steady around 7,500 ML/day and is expected to begin to recede in a few days’ time.
    Freshening flows provided in the Lindsay River are to recede over the coming weeks.
    Source: Tom Zouch, MDBA..
    Freshening flows provided in the Lindsay River are to recede over the coming weeks.
  • At the Lower Lakes, the 5-day average water level in Lake Alexandrina decreased 1 cm to 0.58 m AHD. Releases through the barrages are continuing, although gates at Goolwa and Mundoo barrage have been closed at times to manage reverse flows of sea water due to high tides and large swells. Releases have been around 4,000 ML/day during recent days.

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