River Murray Weekly Report For the week ending Wednesday, 23 December 2020 Trim Ref: D20/51035 Please note that MDBA offices will be closed from Christmas Day to New Year’s Day. As such this will be the final Weekly Report issued for the 2020 calendar year. There will be no Weekly Report issued for the week ending Wednesday, 30th December 2020. The first report for 2021 will cover the two‐week period ending Wednesday, 6th January 2021 and will be available from Friday, 8th January 2021. Rainfall and inflows This week there were widespread and varied rainfall totals across the Murray‐Darling Basin, the highest totals of which were observed in North East NSW (Map 1). In the southern Basin, the highest totals were recorded in the Murrumbidgee catchment, with slightly lower totals in upper Murray catchments and along the mid‐Murray. In NSW, Tumut in the Murrumbidgee catchment recorded 64 mm, and in the Central Murray catchment, Albury recorded 53 mm. In Victoria, Falls Creek in the Victorian Alps recorded 39 mm and Kerang in the mid‐Murray recorded 43 mm. Map 1 ‐ Murray‐Darling Basin rainfall totals for week ending 23 December 2020 (Source: Bureau of Meteorology). Streamflow in the upper Murray catchments experienced a small rise in some locations following some rainfall during the week. However, streamflows have now begun to recede again. Further specific information about flows at key locations can be found at the MDBA’s River Murray data webpage. Up‐to‐date river data for sites in the upper Murray can also be found on BoM’s website and in the Murray River Basin Daily River Report at the WaterNSW website. BoM produce 7‐day stream flow forecasts for a number of tributaries including the Ovens and Kiewa Rivers and these are available on their website. Subscribe to the River Murray Weekly Report River Data website Water in Storages River Murray Weekly Report The Bureau of Meteorology’s (BoM) current 8 day rainfall forecast shows rainfall totals up to 25 mm are likely for the upper Murray over the coming week with some lower totals possible on the mid‐Murray. Photo 1 – Aquatic vegetation in Reedy Lagoon, Gunbower Forest, as drawdown commences. Credit: GBCMA. River operations Water for the environment Southern Spring Flow event concludes System transfers continue The delivery of IVT from the Goulburn and Murrumbidgee valleys to the Murray continue Lake Victoria continues to fall as it supports the delivery of system demands Water demand The MDBA is actively monitoring shortfall risks. A shortfall occurs when water cannot be delivered to users when and where it is needed. A delivery shortfall occurs when actual water use is higher than it was forecast to be when river water was released from the Hume and Dartmouth storages, weeks earlier, to meet the forecast needs for irrigation and environmental water. A system shortfall occurs when the combined capacity of the system is unable to supply all downstream requirements over the full season. More information about shortfalls can be found at Water demand (shortfalls) | Murray‐Darling Basin Authority (mdba.gov.au). The risk of a delivery shortfall in the River Murray between Wakool Junction and the SA Border, over the coming week, is currently negligible. The MDBA is continuing to monitor weather conditions and forecast demands to manage the risk of delivery shortfall. The risk of a system shortfall is being closely monitored in consultation with states. The system is finely balanced and the potential for a system shortfall in late summer has been identified within river operations planning scenarios. The MDBA and states will continue to monitor this risk closely over the coming weeks and will take steps to minimise the risk of a shortfall as necessary. The MDBA, Basin state governments and their agencies have different roles and responsibilities in managing delivery shortfalls. Read more information on delivery shortfall risks for Victorian water licence holders. Water quality impacts A number of amber alerts for blue‐green algae remain and include the River Murray at Picnic Point, Barham, Murray Downs, Tooleybuc, upstream of Euston Weir, Mt Dispersion, Merbein, Curlwaa, Fort Courage and Lock 8, plus the Edward River at Old Morago and Moulamein and the Wakool River at Stoney Crossing. It is important that water users regularly keep up to date with algal alerts, notices and health warnings. This information is available through Goulburn‐Murray Water and WaterNSW. Following the Bureau of Metrology’s declaration of La Niña and continued wet rainfall outlook across south eastern Australia, Murray Darling Basin communities should be aware there is a significant risk of hypoxic blackwater events occurring particularly in New South Wales. After three hot and dry years, floodplains have a high load of leaf litter and other organic material. La Niña conditions in summer can increase the risk of heavy rain and flooding, which can wash organic matter into waterways and lead to hypoxic blackwater events. For more information, including the Basin water quality risk map, please see the MDBA website. Subscribe to the River Murray Weekly Report River Data website Water in Storages River Murray Weekly Report Monthly snapshot of water in the system River Murray communities can now access a monthly point‐in‐time snapshot that shows what proportion of water in the river has been provided for the environment compared with water for towns, industries and irrigators. Every day, water enters the river at different points and for different purposes, including irrigation, town water supply, industries and specific environmental benefits. The monthly snapshot shows in simple terms the volume of flow and the extent to which it comprises water for the environment at five locations—in the River Murray at Yarrawonga and the South Australian border, and in the Murrumbidgee, Goulburn and Darling rivers just upstream of their junction with the Murray. Find out more on Flows in the River Murray system. River operations Over the past week, MDBA total active storage decreased by 101 GL to 4,665 GL (55% capacity). At Dartmouth Reservoir, the storage level increased by 5 GL to 2,391 GL (62% capacity). The release, measured at Colemans, was increased this week to target 350 ML/day for variability in the Mitta Mitta River. It is expected that the release will remain at around this rate over the next week and into January. This week the Hume Reservoir storage level decreased by 74 GL to 2,029 (68% capacity). The current Hume release is around 13,000 ML/day and will likely remain at around this rate over the next week. The current release rate is supplying consumptive demands and conveyance along the river, as well as slowing the rate of decline of Lake Victoria’s storage volume as we head into summer. At Lake Mulwala, the pool level remains within the normal operating range of between 124.6 and 124.9 m AHD. Diversions to Mulwala Canal averaged around 4,000 ML/day this week. On the Victorian side, diversion into Yarrawonga Main Channel peaked at near 1,100 ML/day before reducing to the current rate of around 900 ML/day. Diversions over the coming week may vary with Christmas day falling mid‐week. Photo 2 ‐ Kiewa River near the Yackandandah tributary, Kiewa Photo 3 – Kiewa River at Bandiana, Kiewa catchment. catchment. Credit Matt Todhunter. Credit: Tom Zouch. Subscribe to the River Murray Weekly Report River Data website Water in Storages River Murray Weekly Report This week, the release from Yarrawonga Weir decreased to 8,800 ML/day, within channel capacity, as the water for the environment Southern Spring Flow event concluded. It is anticipated that releases will continue at around 8,800 ML/day to support demands across summer. The water for the environment flows have supported the Murray Cod nesting season, while also increasing lateral connectivity between the River Murray and the Barmah—Millewa Forest. This greater connectivity has been achieved by opening selected regulators in the forest. Together, these actions promote increased productivity in the river and support plants and animals in the forest. All actions associated with water for the environment are tracked and water usage debited from environmental water holder (EWH) accounts. Photos 4&5 – Ibis nest with eggs and chick at Boals Deadwood Wetland, Barmah Forest (above) and Pseudorpahis spinescens (Moira Grass) on flooded Hut Lake, Barmah Forest (below). Credits: Keith Ward, GBCMA. Flow through the Edward River Offtake remains steady near 1,550 ML/day, while flow through the Gulpa Creek Offtake has averaged near 400 ML/day to help fill wetlands adjacent to the creek. Downstream, return flows from Millewa Forest to the Edward River are gradually easing as flows downstream of Yarrawonga reduce. Flow through the Wakool River, Yallakool Creek and Colligen Creek offtakes is currently around 80, 520 and 270 ML/day, respectively. This week a pulse of water for the environment was delivered in the Yallakool Creek to support silver perch breeding. The flow is anticipated to peak at around 550 ML/d during the coming week. This week the flow downstream of Stevens Weir averaged around 2,500 ML/day and is anticipated to remain near this rate over the coming week. On the Goulburn River, the flow measured at McCoys Bridge averaged around 1,100 ML/day over the week and is forecast to fluctuate around 1,350 ML/day throughout the remainder of December as Goulburn Inter Valley Trade (IVT) is delivered to the Murray. In addition to the Goulburn River, the delivery of water from the Goulburn IVT account to the Murray is continuing to take place via the Campaspe River and Broken Creek.