River Murray Weekly Report For the week ending Wednesday, 11 November 2020 Trim Ref: D20/46325 Rainfall and inflows Over the past week a low-pressure trough and associated thunderstorm activity produced moderate to heavy falls across parts of the northern Murray-Darling Basin (Map 1). In New South Wales light to moderate falls were mostly confined to areas along the Great Dividing Range, while in the southern Murray-Darling Basin the highest rainfall totals were over the upper Murrumbidgee and Lachlan River catchments. Map 1 - Murray-Darling Basin rainfall totals for week ending 11 November 2020 (Source: Bureau of Meteorology). Given the drier and warmer conditions across upper Murray catchments, upper Murray tributary inflows continued to ease this 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. The Bureau of Meteorology’s (BoM) current 8 day rainfall forecast shows modest rain for the Basin, primarily in southern and eastern areas. Subscribe to the River Murray Weekly Report River Data website Water in Storages River Murray Weekly Report River operations • Hume Dam release increased to meet downstream demands • Water for the environment supporting Murray Cod in the Murray and Lower Darling • Lake Victoria storage level to peak in coming week • System transfers to Lake Victoria may commence in coming weeks Water quality impacts Amber alerts for blue-green algae have been extended and now include the River Murray downstream of Yarrawonga Weir, Cobram, Picnic Point, Tooleybuc, Buronga and Lock 8, plus the Edward River at Old Morago 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 spring 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. 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 increased by 4 GL to 5,220 GL (62% capacity). At Dartmouth Reservoir, the storage level increased by 17 GL to 2,348 GL (61% capacity). The release, measured at Colemans, continued to target the minimum flow rate of 200 ML/day. After reaching a peak storage level late last week, this week the Hume Reservoir storage level decreased by 28 GL to 2,410 GL (80% capacity). The current Hume release is near 13,500 ML/day and is expected to increase in coming days as downstream tributary inflows further ease and demands slowly increase. Currently, the majority of the Hume release is water for the environment, released to help meet a target flow rate downstream of Yarrawonga Weir. Over the coming weeks, should dry conditions prevail, MDBA may commence bulk transfers to slow the rate of storage decline at Lake Victoria. This operation would help ensure system demands can be met over the peak summer period. These transfers may include Hume to Lake Victoria transfers and call of water held in Inter Valley Trade accounts in the Goulburn and Murrumbidgee valleys. Further information will be provided in coming weeks. At Lake Mulwala, the pool level remains near 124.74 m AHD and within the normal operating range of between 124.6 and 124.9 m AHD. Diversion to Mulwala Canal is currently 1,250 ML/day and on the Victorian side, about 1,200 ML/day is being diverted into Yarrawonga Main Channel. Diversions are anticipated to gradually increase over the coming week, in-line with the warm and mostly dry forecast conditions. The release from Yarrawonga Weir has continued to target 15,000 ML/day and a similar rate is expected over the coming week. This release continues to support the Murray Cod nesting season, while also increasing lateral connectivity between the River Murray and the Barmah—Millewa Forest. This greater connectivity has been enabled by the opening of selected regulators in the forest. Together, these actions promote increased productivity Subscribe to the River Murray Weekly Report River Data website Water in Storages River Murray Weekly Report in the river and supports plants and animals in the forest. All actions associated with water for the environment are tracked and water usage debited from environmental water holder accounts. Flow through the Edward River Offtake is steady near 1,540 ML/day, while flow through the Gulpa Creek Offtake continues to target 700 ML/day to help fill wetlands adjacent to the creek. Downstream return flows from Millewa forest to the Edward River continue and will persist over coming weeks. Flow through the Wakool River, Yallakool Creek and Colligen Creek offtakes is currently around 100, 500 and 400 ML/day, respectively. This week the flow downstream of Stevens Weir fluctuated around 2,400 ML/day and may ease this week if diversions to Wakool Main Canal increase above the current take of 580 ML/day. On the Goulburn River, the flow measured at McCoys Bridge gradually reduced this week from around 1,500 ML/day to 1,100 ML/day. Later this week flows are anticipated to gradually increase and peak the following week, due to the release of water for the environment. This action is aimed at supporting large-scale Golden Perch migration and spawning in the Goulburn River. Information regarding opportunities for allocation trade between the Goulburn and Murray Valleys is available at the Victorian water register website. Diversions to National Channel increased to 2,100 ML/day and similar diversion is expected over the coming week to help improve storage levels in Kow Swamp and other mid-Murray lakes within the Torrumbarry Irrigation system. Elevated baseflows continue to be supplied to Gunbower Creek to provide increased habitat for native fish and other aquatic animals over the spring period. Flow in Gunbower Creek returns to the River Murray via Koondrook Spillway, downstream of Torrumbarry Weir near Barham. This week the release downstream of Torrumbarry Weir reduced from around 9,750 ML/day to 8,100 ML/day. Inflow from the Murrumbidgee River, measured at Balranald, averaged around 2,700 ML/day for the week. Flows are expected to increase to around 4,000 ML/day over the coming week, before receding. This higher flow is primarily due to the release of water for the environment from Burrinjuck Dam last month. For information on any supplementary access in the Murrumbidgee system, please refer to the WaterNSW website. The Murrumbidgee IVT balance is open for trade from the Murray to the Photo 1 – Nardoo (Marsilea drummondii) that has grown in response to water for the Murrumbidgee (102 GL) but remains environment being pumped (outlet in background) at Wallpolla Creek East; Wallpolla closed for trade from the Island. Photo Credit: David Wood, MalleeCMA Murrumbidgee to the Murray. Subscribe to the River Murray Weekly Report River Data website Water in Storages River Murray Weekly Report At Euston Weir, the weir pool level remains at FSL. The downstream release peaked at around 15,500 ML/day before receding to the current flow of 13,500 ML/day and flows are expected to vary around this rate for the coming week. Menindee Lakes storage eased this week to 438 GL (25% capacity). The downstream release, measured at Weir 32, remains near 480 ML/day, with small releases of water for the environment continuing to help boost the rate above the normal minimum target. These flows aim to improve the condition of the lower Darling and help Murray Cod breed this spring. For more information refer to the Commonwealth Environmental Water Office and NSW Department of Planning, Industry and Environment. Some water restrictions remain current in NSW. Links to drought services and assistance can be accessed via the MDBA drought webpage. At Wentworth Weir, the weir pool level is being managed at around FSL. The downstream flow peaked at around 14,200 ML/day and is forecast to slowly decrease over the coming week. Downstream at Lock 9, Lock 8 and Lock 7 weir pools continue to vary near FSL, within their normal operating range. The storage level at Lake Victoria increased this week by 14 GL to 656 GL (97% capacity) as the storage continued capturing water in transit from upstream tributaries.