River Murray Weekly Report For the week ending Wednesday, 28 April 2021 Trim Ref: D21/10590 Rainfall and inflows Little to no rainfall was observed across the Murray Darling Basin this week (Map 1). Specific information about flows at key locations can be found at the MDBA’s River Murray data webpage. The Bureau of Meteorology is currently forecasting widespread rainfall across much of the Basin in the coming week. Following heavy rain in late March, Water NSW now estimate that 800-950 GL of inflow may reach Menindee Lakes as a result of flow in the Darling River. This estimate may be revised further in coming weeks as flows move towards Menindee Lakes. These inflows are expected to result in the water stored in Menindee Lakes increasing above the trigger volume (640 GL), which means the Menindee Lakes will be part of the River Murray shared water resources. For updates on flow forecasting in the northern Basin please see the Water NSW website. 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 Water NSW website. Map 1: Murray-Darling Basin rainfall for the week ending 28 April 2021. Source: Bureau of Meteorology. Subscribe to the River Murray Weekly Report River Data website Water in Storages River Murray Weekly Report River operations • Significant flows in the northern Basin are contributing to increased storage at Menindee Lakes. • Water for the environment pulse taking place in the Goulburn River and Murrumbidgee River • River users and houseboat owners should be aware that river levels will continue to vary over the coming week. River Levels Over the last few weeks, demands have oscillated as warm conditions were followed by mild autumn weather and now widespread rainfall is forecast. Releases, and water levels, along the Murray have varied in response. River users can monitor River Murray levels and flow forecasts at key locations on the MDBA’s River Murray data webpage to assist in planning any river activities. Recreational activities that require deeper water such as boating can take advantage of many weir pools along the river which will remain near normal levels over the coming week. Water demand The MDBA has been actively monitoring shortfall risks over the irrigation season. 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 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 negligible. The MDBA is continuing to monitor weather conditions and forecast demands and will actively manage the risk of delivery shortfall across the autumn period as conditions evolve. The MDBA, Basin state governments and their agencies have different roles and responsibilities in managing shortfalls. Read more information on delivery shortfall risks for Victorian water licence holders. Water quality impacts The Murray and Lower Darling Regional Algal Coordinating Committee has continued to declare a number of red and amber alerts for blue-green algae in the River Murray System. Currently, red alert warnings are in place on the River Murray at Echuca/Moama and between Tooleybuc and Fort Courage. Amber alerts are in place at a number of sites on the River Murray and along the Edward-Wakool River system. The locations of these sites are available on the WaterNSW website. 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. River operations Total active storage reduced by 50 GL over the last week to 3,727 GL (44% capacity). At Dartmouth Reservoir, the storage increased by 2 GL to 2,458 GL (64% capacity) and the release, measured at Colemans, continues to target around 250 ML/day. Over the past week the Hume Reservoir storage decreased by 44 GL to 1,279 GL (43% capacity). The Hume release remained around 11,000 ML/day for most of the week before reducing to 10,000 ML/day. The release is expected to continue to gradually reduce over the coming week as supply requirements downstream of the storage ease. The Lake Mulwala level is currently near 124.76 m AHD, within the normal operating range (124.6 to 124.9 m AHD). Diversions to Mulwala Canal have remained steady over the past week, averaging around 2600 ML/day. On the Victorian side, diversion to Yarrawonga Main Channel increased from 1,000 ML/day to 1,300 ML/day. The release from Yarrawonga Weir continued to target 8,500 ML/day this week and forecast to gradually reduce over the coming week as downstream demands ease. Subscribe to the River Murray Weekly Report River Data website Water in Storages River Murray Weekly Report The gates of the Edward River Offtake remain lifted clear of the water, meaning flows will now vary with Murray levels. The flow through the offtake is around 1,550 ML/day and is expected to ease as Yarrawonga Weir releases reduce. Flow through Gulpa Creek Offtake has averaged 250 ML/day this week and may similarly ease over the coming week. Downstream on the Edward River, the release from Edward Escape ceased during the week and the diversion to Wakool Main Canal diversion has reduced to around 650 ML/day. The flow downstream of Stevens Weir varied as high as 1,250 ML/day to the current lower rate near 770 ML/day. Flows are expected to remain around this rate over the coming week. Flow through the Wakool River and Yallakool Creek offtakes gradually eased across the week and are near 50 and 200 ML/day, respectively. Flows will continue to fall over the coming week as the end of an autumn environmental pulse is delivered to support native fish. Flow through the Colligen Creek offtake is currently 230 ML/day. On the Goulburn River, the flow measured at McCoys Bridge increased from 2,200 ML/day to peak at the current rate of 5,800 ML/day. Water for the environment is currently being delivered on top of Goulburn IVT to boost the flows and benefit the recovery of native vegetation along the banks of the lower Goulburn River. In addition to the Goulburn River, the delivery of water from the Goulburn IVT account to the Murray is continuing from the Campaspe River with a combined Goulburn IVT delivery of around 40 GL planned for April. A small volume of delivery on top of the 40 GL in April, to account for undelivered volumes in previous months, is planned for delivery in late April. For more information see the Goulburn-Murray Water website. Information regarding opportunities for allocation trade between the Goulburn and Murray Valleys is available at the Victorian water register website. Diversions to National Channel averaged around 2,500 ML/day and are expected to reduce over the coming week. The release from Torrumbarry Weir rose over the week to near 9,000 ML/day as the water for the environment pulse from the Goulburn river makes its way downstream. Inflow from the Murrumbidgee River, measured at Balranald, continued to gradually reduce to the current rate of 450 ML/day. Flows are forecast to remain low over the coming week before starting to rise as IVT and water for the environment are delivered in a pulse up to 6,000 ML/day expected in the second week of May. A revised request of up to 50 GL of Murrumbidgee IVT has been ordered from the Murrumbidgee system in April. Additionally, up to 30 GL of Murrumbidgee IVT has been ordered for May. The Murrumbidgee IVT balance is open for trade from the Murray to the Murrumbidgee (89.0 GL), but remains closed for trade from the Murrumbidgee to the Murray. At Euston Weir, the weir pool level remains near full supply level (FSL). Over autumn and into winter, Euston weir pool will be lowered to around 20 to 30 cm below FSL as part of normal weir pool variability. Varying pool levels helps restore a more natural wetting and drying cycle to riverbanks and adjacent wetlands within the influence of the weir pool. Also, during periods of higher flow, lowering the pool level can increase flow velocity within the weir pool to help move accumulated sediment downstream. The downstream release remain near the current rate of 7,000 ML/day and is expected to start rising over the coming week. In the coming week, a portion of water for the environment passing downstream of Euston weir will be diverted into the Hattah lakes system to fill to a number of lakes and provide benefits to aquatic environment wetlands plants and animals. This action is undertaken on behalf of environmental water holders and will continue until early June 2021. Several of the upstream tributaries of the Barwon-Darling have experienced flooding following heavy rain in late March, including moderate to major flooding in the Barwon and Warrego Rivers. Flow in the Darling River at Bourke appears to have peaked around 43,600 ML/day and downstream, Wilcannia is rising and near 22,000 ML/day.