River Murray operations 29 March to 4 April 2017

7 April 2017

Welcome to our summary report on River Murray operations for the week ending 4 April 2017.

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

Rainfall and inflows

Most rainfall this week was confined to the north east of the Basin in the wake of ex-tropical cyclone Debbie which tracked southwards across the Queensland-New South Wales border. This resulted in heavy rainfall within Queensland’s Condamine-Balonne catchment with a weekly total of 169 mm recorded outside of Dalby and 138 mm in Maryvale. Less rainfall reached the Basin in New South Wales where a top of 63 mm was recorded at both Glenn Innes and Deepwater in the northern tablelands.  The ex-tropical cyclone has since moved offshore. There was no significant rainfall in Victoria or South Australia, with only 6mm recorded in the southern reaches of the Basin. Very little rainfall was recorded over the River Murray itself.

At the beginning of the week, stream flows in the upper Murray tributaries were receding following last week’s rain but they have since steadied. On the Mitta Mitta River, the flow at Hinnomunjie Bridge averaged 200 ML/day. On the upper Murray at Biggara the flow averaged around 280 ML/day. Downstream of Hume Reservoir both the Kiewa River at Bandiana and the Ovens River at Wangaratta receded by about 200 ML/day this week and are currently around 330 ML/day and 530 ML/day respectively.

In the northern Basin, recent heavy rain associated with ex-Tropical Cyclone Debbie fell mainly over coastal catchments. However, significant rainfall also made its way across the divide into the upper catchments of several Barwon-Darling tributaries - including the Condamine, Moonie, Weir, Dumaresq and Macintyre Rivers - and resulted in significant flow responses. River levels exceeded the major flood level at several locations and a number of Bureau of Meteorology warnings for minor to moderate flooding remain current. It is too early at this stage to estimate the volumes of water likely to flow into the Barwon-Darling River from this event, however significant loss and diversion is likely to reduce the volume as it moves downstream. Further updates will be provided in the Weekly Report during the coming weeks.

March 2017 Summary

March was a wet month in some parts of the Basin with above-average rainfall in much of New South Wales and Queensland. Numerous locations in the north east of the Basin had their highest total March rainfall on record. In contrast, much of South Australia received below average rainfall. Close to average rainfall was recorded for most of Victoria. The Basin experienced an exceptionally warm month with temperatures very much above average. Some parts of north central Victoria recorded highest on record mean March temperatures with an anomaly of 2.83 °C above the long-term average. The Loddon‑Avoca catchment was particularly warm with Kerang recording a mean temperature of 23.8 °C.

River Murray System inflows during March (excluding Snowy Scheme, Darling River and managed environmental flows) totalled around 90 GL, which is below the month’s long-term average of about 216 GL. In comparison with the historical record since 1891, only about 18% of previous monthly totals for March have been lower than the inflows observed in March 2017. Recent warmer than average conditions have contributed to evaporation within the Basin.

Total in storage

Total MDBA storage decreased by 145 GL this week, with active storage now 5,418 GL (63% capacity).

River operations

System Operations

Similar to the last few weeks, operations 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.

Low and variable flows are projected along the mid-reaches of the River Murray during coming weeks, including the Easter period. 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.

River Operations

  • The storage volume at Dartmouth Reservoir has not changed this week, remaining at 2,994 GL (78% capacity). The release from Dartmouth, measured at Coleman’s, averaged 300 ML/day. The release will be increased for this weekend to 1,000 ML/day, see attached flow advice.
  • Storage in Hume Reservoir decreased this week by 85 GL and is currently 1,909 GL (64% capacity). Releases from Hume were as high as 17,000 ML/day at the beginning of the week before falling to 12,000 ML/day due to fluctuating demand and losses in the Hume to Lake Mulwala reach. The release now sits at 14,000 ML/day. 
  • Diversions from Lake Mulwala remained high this week. Diversion to Mulwala Canal has seen an increase to almost 5,000 ML/day, whereas diversion to Yarrawonga Main Channel has remained relatively constant, averaging 2,300 ML/day. After dropping to 124.64 m AHD last Thursday, the water level at Lake Mulwala is now sitting at 124.84 m AHD. The releases downstream of Yarrawonga Weir have averaged around 8,000 ML/day.
  • Inflows to the Edward-Wakool system have remained fairly steady through the week with very similar flows as last week. Flows through the Edward River off-take have remained around 1,600 ML/day while the Gulpa Creek off-take has remained around 330 ML/day. Diversions from the Stevens Weir pool into the Wakool Main Canal are considerably lower than in previous months and are currently around 900 ML/day. Downstream of Stevens Weir the flow has been relatively steady averaging almost 800 ML/day.
  • On the Goulburn River, the flow at McCoys Bridge has continued to recede as anticipated, falling from 2,000 ML/day to 1,000 ML/day. This reduction in flow was due to the cessation of IVT from the Goulburn and reduction in environmental water from the Goulburn. Delivery of IVT from the Goulburn for April and May will depend on system demands and weather.
  • Diversion from Torrumbarry Weir pool to National Channel has remained steady at around 3,200 ML/day. Due to diminished upstream inflows and relatively high irrigation demands, the release downstream of the weir has receded from 5,000 ML/day at the beginning of the week to just under 2,500 ML/day. Further downstream at Swan Hill the flow also receded this week, from around 5,500 ML/day to 3,600 ML/day. The flow at Swan Hill is forecast to recede further to around 2,500 ML/day this coming week (this corresponds with a level of around 0.67 m which is above the minimum target level of 0.6 m local gauge height)
  • A significant increase in flow is being experienced on the Murrumbidgee River at Balranald. As projected last week, the arrival of environmental water has seen an increase from around 900 ML/day at the beginning of the week to around 3,430 ML/day on Wednesday. These are the highest recorded flows since the beginning of January.
  • At Euston Weir, the pool level is currently 47.42 m AHD (18 cm below full supply level) see photo 1. As part of the weir pool variability program it is expected that this level will vary to around 20 cm below FSL over the coming days. The flow rate downstream of the weir has continued to rise gradually and is now around 6,200 ML/day.

 

Euston Weir
Source: Phil Cocks, WaterNSW
Looking upstream at Euston Weir. The weir pool is currently being varied to manage downstream flows whilst erosion control measures are being undertaken.
  • On the Darling River, total storage volume in the Menindee Lakes fell by 45 GL, to the current volume of 863 GL (50% capacity). The release from Menindee Lakes into the lower Darling River has been steady this week around 1,400 ML/day but is now targeting 1,000 ML/day. This is significantly lower than in previous months and can be attributed to a decrease in downstream demand. Releases over the remainder of April and May will depend on system demands. For almost the third week in a row, releases from Lake Cawndilla have remained at around 1,000 ML/day as environmental flows are provided to the Great Darling Anabranch. So far around 49 GL of environmental water has been released which is slowly making its way downstream and is likely to reach the Murray by the end of the month.
  • At the junction of the Darling and Murray rivers at Wentworth, flows have averaged around 6,500 ML/day and on Wednesday increased to 6,970 ML/day.
  • Weir pool variability continues at Locks 7 and 8 which are 51 cm and 64 cm below FSL respectively. Over the coming weeks Lock 7 will be gradually lowered to around 90 cm and Lock 8 will be lowered up to one metre below FSL.
  • Lake Victoria storage decreased by 15 GL this week to a storage volume of 326 GL (48% capacity). The flow to South Australia is currently around 7,800 ML/day and is projected to decrease over the coming weeks. Downstream at Lock 1 flows have eased to around 5,000 ML/day.
  • At the Lower Lakes, the 5-day average water level in Lake Alexandrina increased by 1 cm to 0.59 m AHD. Barrages were closed at the beginning of the week because of large swells and high tides. Releases reached around 2,800 ML/day toward the end of the week.

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