River Murray Weekly Report For the week ending Wednesday, 18 November 2020 Trim Ref: D20/46986 Rainfall and inflows Small to moderate rainfall totals were recorded across the southern and western basin and the Eastern ranges this week (Map 1). In the Lower Darling catchment Karpa Kora Station (Pooncarie) recorded 24mm. Cabramurra in the upper Murray recorded 18 mm, and in Victoria, Castlemaine in the Loddon-Avoca catchment recorded 18 mm. Map 1 - Murray-Darling Basin rainfall totals for week ending 18 November 2020 (Source: Bureau of Meteorology). Despite some modest rainfall totals, inflows continued to ease across the Murray catchment this week with predominantly drier and warmer conditions increasing across the southern basin. 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 some moderate rainfall totals are possible 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 • Inflows to the system continue receding • Water for the environment supporting Murray Cod in the Murray and lower Darling • Lake Victoria storage peaking just below full 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, Curlwaa, Fort Courage 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 decreased by 58 GL to 5,174 GL (61% capacity). At Dartmouth Reservoir, the storage level increased by 11 GL to 2,359 GL (61% capacity). The release, measured at Colemans, continued to target the minimum flow rate of 200 ML/day. This week the Hume Reservoir storage level decreased by 58 GL to 2,352 GL (78% capacity). The current Hume release is near 12,500 ML/day and is expected to remain steady in coming days depending on actual demands. This week, the portion of Hume releases supplying water for the environment downstream of Yarrawonga Weir began to decrease as volumes to meet all other demands increased. Over the coming weeks, should dry conditions persist, these higher releases will continue to supply consumptive demands and conveyance along the river, as well as helping slow the rate of storage decline at Lake Victoria as we head into summer. This will ensure the system is well placed to meet demands across the coming months, particularly if conditions remain dry. At Lake Mulwala, the pool level remains within the normal operating range of between 124.6 and 124.9 m AHD. Diversion to Mulwala Canal is currently 1,600 ML/day. On the Victorian side, about 1,500 ML/day is being diverted into Yarrawonga Main Channel. Diversions are anticipated to remain around these rates over the coming week, in- line with the warm and mostly dry forecast conditions. The release from Yarrawonga Weir was reduced from 15,000 to 14,000 ML/day during the week. This marginally lower 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 in the river and support plants and animals in the forest. All actions associated with water for the environment are tracked and Subscribe to the River Murray Weekly Report River Data website Water in Storages River Murray Weekly Report water usage debited from environmental water holder accounts. Flows will decrease later in the week as the water for the environment is gradually reduced to help provide conditions suitable for fish breeding. Flow through the Edward River Offtake remains steady near 1,550 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 350 ML/day, respectively. This week the flow downstream of Stevens Weir averaged around 2,500 ML/day and is anticipated to remain steady over the coming week. On the Goulburn River, the flow measured at McCoys Bridge gradually increased this week from around 1,100 to 3,200 ML/day as a pulsed release of water for the environment made its way downstream. The flow is anticipated to continue to increase and peak during the coming week. This action is aimed at supporting large-scale Golden Perch migration and spawning in the Goulburn River and will contribute beneficial flow along the length of the Murray as it passes further downstream. The delivery of water from the Goulburn IVT account to the Murray commenced this week. 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 remained steady at around 2,100 ML/day this week and a 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 averaged around 8,200 ML/day and is anticipated to increase and peak over the week as higher flows from the Goulburn River arrive on the Murray. Photo 1 – Taemas Bridge over the Murrumbidgee River, Wee Jasper Road. Photo Credit: Tim Rossi. Subscribe to the River Murray Weekly Report River Data website Water in Storages River Murray Weekly Report Inflow from the Murrumbidgee River, measured at Balranald, increased slowly over the week to a peak of around 4,300 ML/day on Sunday, after which the flow began to recede. 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 Murrumbidgee (102 GL) but remains closed for trade from the Murrumbidgee to the Murray. MDBA has called on 30 GL of water from the Murrumbidgee IVT account for delivery in December. At Euston Weir, the weir pool level remains at FSL. The downstream release averaged around 14,100 ML/day this week and flows are expected to gradually decrease over the coming week. Menindee Lakes storage eased this week to 424 GL (24% 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 held relatively steady this week averaging around 11,600 ML/day. Slightly higher flows are expected 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.