Weekly Report 06 January 2021
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River Murray Weekly Report For the previous two weeks ending Wednesday, 6 January 2021 Trim Ref: D21/397 Please note that the usual Annual Summary for 2020 and a Monthly Summary for December 2020 will be included in the next Weekly Report for the week ending 13th January 2021. Rainfall and inflows for the last two weeks In the southern Basin, rainfall was largely absent in the week ending 30th December 2020 (Map 1a). For the week ending 6th January 2021, an east moving surface trough brought widespread rainfall across south eastern Australia (Map 1b). In NSW, highest rainfall totals included 47 mm at Cabramurra in the upper Murray catchment and 26 mm at Burrinjuck Dam on the Murrumbidgee River. In Victoria, 25mm was recorded at Goulburn Weir and 17 mm was recorded in the lower Murray at Mildura. In the northern Basin, a broad surface trough resulted in widespread moderate to high rainfall totals across both weeks. For the week ending 6th January 2020, 100-150 mm was recorded across central NSW and southern QLD. The BoM is currently forecasting little to no rainfall over the coming 8 days. Map 1a: Rainfall totals for week ending 30 December 2020 (Source: Bureau of Meteorology) Subscribe to the River Murray Weekly Report River Data website Water in Storages Map 1b: Rainfall totals for week ending 6 January 2021 (Source: Bureau of Meteorology) The upper Murray tributaries saw a reduction in streamflow during the first week of the Christmas break, however, modest streamflow rises were observed following rainfall in the second week. 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 operations • October update to 2020-21 Annual Operating Outlook published on MDBA website • System transfers continue • The delivery of IVT from the Goulburn and Murrumbidgee valleys to the Murray continue • Lake Victoria continues to fall, as forecast, to support system demands • Red alert level for blue-green algae issued upstream of Euston Weir and the Murray River at Buronga. 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. For more information, please see the MDBA’s October update to the 2020-21 River Murray System Annual Operating Outlook. This update refines the scenarios from the July publication using data to the end of October. Please note that the Operating Outlook may be updated again later this water year if observed conditions deviate significantly from those assumed in the report. 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 Water NSW have recently declared red alerts for blue-green algae in the River Murray System upstream of Euston Weir and at Buronga. A number of amber alerts remain and include the River Murray at Picnic Point, Barham, Murray Downs, Tooleybuc, Mt Dispersion, Merbein, Curlwaa, Fort Courage and Lock 8, plus the Edward River at Old Morago and Moulamein and the Wakool River at Wakool-Barham Road and 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. 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. Subscribe to the River Murray Weekly Report River Data website Water in Storages 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 Total active storage reduced over the last two weeks by 178 GL to 4505 (53% capacity). At Dartmouth Reservoir, since 23 December 2020, the storage increased by 6 GL to 2,397 GL (62% capacity). The release, measured at Colemans, continued to target 350 ML/day and is expected to remain around this rate for the remainder of January. At Hume Reservoir, since 23 December 2020, the storage decreased by 137 GL to 1,892 GL (63% capacity). The current Hume release is around 15,000 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 in summer. Photo 1: Rocky Valley Dam near Falls Creek Resort. Photo: Mathew Todhunter, MDBA. At Lake Mulwala, the pool level remained above 124.7 m AHD across the holiday period. Diversions to Mulwala Canal averaged around 3,700 ML/day over the last two weeks before increasing to the current rate of 4,250 ML/day. On the Victorian side, diversion into Yarrawonga Main Channel averaged 800 ML/day before increasing to the current rate near 1,100 ML/day. With warm temperatures forecast across the coming week, diversions are expected to remain around these rates. Subscribe to the River Murray Weekly Report River Data website Water in Storages The release from Yarrawonga Weir has varied between 9,000 and 9,200 ML/day over the last fortnight and is currently near 9,000 ML/day, resulting in a flow below channel capacity at picnic point. It is anticipated that releases will continue at around these rates over the coming weeks under dry conditions. Flow through the Edward River Offtake has averaged near 1,600 ML/day, while flow through the Gulpa Creek Offtake has remained near 370 ML/day to help fill wetlands adjacent to the creek, higher flow is supplemented by water for the environment. Downstream, flow through the Wakool River, Yallakool Creek and Colligen Creek offtakes is currently around 65, 435 and 280 ML/day, respectively. Over the coming week a second pulse of water for the environment will be delivered in the Yallakool Creek to support silver perch breeding. All actions associated with water for the environment are tracked and water usage debited from environmental water holder (EWH) accounts. The flow downstream of Stevens Weir is currently around 2,300 ML/day and is expected to remain near this rate over the coming week. Photo 2: Rocky Valley Creek at Bogong Village. Photo: Mathew Todhunter, MDBA. On the Goulburn River, the flow measured at McCoys Bridge remained steady across the last two weeks near 1,350 ML/day and is forecast to fluctuate around this rate throughout January 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 via the Campaspe River and Broken Creek. A total of around 27 GL and 40 GL of IVT was delivered during November and December respectively, and a further 40 GL is to be delivered in January. For more information see the Goulburn-Murray Water website.