River Murray Weekly Report For the week ending Wednesday, 25 September 2019 Trim Ref: D19/43708 Rainfall and inflows Precipitation was recorded across most of the southern Murray-Darling Basin this week, with higher totals across the Great Dividing Ranges and southern South Australia (Map 1). Some of the highest totals included 32 mm in the Rocky Valley in Victoria’s upper northeast, 21 mm at Tumbarumba in the NSW southwestern slopes and 20 mm at Morgan in South Australia’s flats and lower Basin region. Map 1 - Rainfall totals for week ending 25th September (Source: Bureau of Meteorology) Only modest responses were observed in the upper tributaries of the River Murray System following this week’s rain. For specific information about flows at key locations in the upper Murray catchment including Hinnomunjie Bridge on the upper Mitta Mitta River, Biggara on the upper Murray, Bandiana on the Kiewa River as well as Peechelba on the Ovens River 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 at Bureau of Meteorology’s (BoM) website and in the Murray River Basin daily river report at the WaterNSW website. Subscribe to the River Murray Weekly Report River Data website Water in Storages River Murray Weekly Report Photo 1: Higher flows downstream of Lake William Hovell on the King River (Photo courtesy: Tim Rossi, MDBA) Subscribe to the River Murray Weekly Report River Data website Water in Storages River Murray Weekly Report River operations • Flows downstream of Yarrawonga maintained at 15,000 ML/day as environmental water deliveries continue. • Environmental flow pulses in the lower Goulburn and Campaspe Rivers now arriving in the Murray. • Weir pool levels rise at Locks 15, 8 & 7. River operations The MDBA total active storage reduced by 16 GL to 3,903 GL (46% capacity). At Dartmouth Reservoir, the storage decreased by 13 GL to 2,249 GL (58% capacity). Releases are continuing from Dartmouth aimed at transferring water to Hume to support expected system demands in the months ahead. Approximately 140 GL will have been transferred from Dartmouth to Hume for the month of September. A target transfer volume of closer to 200 GL is expected for October. Over the last week the releases from Dartmouth, measured at Colemans, rose from 4,300 ML/day to 6,000 ML/day. The release is expected to gradually recede again into the coming week. Dartmouth releases will continue to be varied in a manner that will transfer the required volume to Hume Dam, whilst seeking to minimise erosion along the lower Mitta Mitta River. At Hume Reservoir, the storage increased by 1 GL to 1,269 GL (42% capacity). WaterNSW is currently undertaking scheduled maintenance works at Hume Dam to refurbish the irrigation penstocks and emergency closure gates. Works are expected to be completed by the end of 2021. More information regarding these works and access across the dam wall can be found on the WaterNSW website. The release from Hume Dam is currently 12,500 ML/day. Without significant rainfall, releases are expected to increase steadily in order to meet higher demands downstream including environmental demands. The operational component of the flow has been approximately 9,200 ML/day over the week and is anticipated to remain as such through the month of October. This level of operational flow contributes to meeting demands along the river as well as sustaining the level in Lake Victoria in preparation for expected demands over summer and into autumn. Downstream of Hume, tributary inflows from the Kiewa River at Bandiana and the Ovens River at Wangaratta both averaged around 3,000 ML/day over the past week. At Lake Mulwala, the pool level is currently 124.70 m AHD and is expected to remain within the normal operating range of 124.6 to 124.9 m AHD in the coming week. Diversions to the Mulwala Canal and Yarrawonga Main Channel (YMC) are around 1,000 ML/day and 700 ML/day respectively. The release downstream of Yarrawonga Weir is targeting 15,000 ML/day. This higher flow rate is being targeted on behalf of environmental water holders who have identified inundation of the Barmah-Millewa Forest as a key watering action for this year. Water consumed in the Barmah-Millewa Forest will be debited from entitlements held by environmental water holders. Water flowing back into the river from the forest, known as ‘return flows’, will be coordinated with a planned environmental pulse from the Goulburn and Campaspe Rivers providing ecological benefits along the length of the River Murray to the Coorong in South Australia. Updates on environmental watering actions and monitoring during spring 2019 are available from the Commonwealth Environmental Water Office website. For more information on how environmental water is helping to improve the health of rivers in the Basin see the NSW Department of Planning, Industry and Environment website and the latest fact sheet and update from the Commonwealth Environmental Water Office. Flows through the Edward and Gulpa offtakes are currently near 1,560 and 720 ML/day respectively. The diversion to Gulpa Creek at this higher rate is delivering environmental water to the Gulpa wetlands to provide optimal nesting habitat for the endangered Australasian Bittern over October, November and into December. Subscribe to the River Murray Weekly Report River Data website Water in Storages River Murray Weekly Report Further downstream on the Edward River at Toonalook the flow averaged near 4,100 ML/day. This flow is currently being boosted by around 1,800 ML/day from return flows from the Millewa Forest. At Stevens Weir, the release is near 3,200 ML/day and is forecast to remain around this rate into the near future. Regulators into Werai forest have been opened to assist in managing flows downstream of Steven’s Weir. This action will allow water to flow through the Niemur River via anabranch channels in Werai forest. Photo 2: Edward River at Deniliquin, downstream of Toonalook (Photo courtesy of Digby Jacobs, MDBA) On the Goulburn River the flow has increased this week from 1,100 ML/day to 5,500 ML/day at McCoys Bridge as environmental spring pulse is delivered through the Goulburn System. The timing of these flows has been co- ordinated with the spring watering event on the River Murray. Similarly, an environmental watering action is underway in the Campaspe River. Flows at Rochester reached 1,500 ML/day and have receded to 650 ML/day. Flows will continue to recede over the coming week. For more information see the Victorian Environmental Water Holder and their latest watering releases. The current Goulburn IVT balance is around 236 GL. More information regarding current opportunities for allocation trade between the Goulburn and Murray valleys is available at the Victorian water register website. Downstream at Torrumbarry weir pool, diversions to Koondrook-Perricoota Forest are continuing at around 500 ML/day. Koondrook-Perricoota Forest was last inundated during 2016 following extensive natural flooding. However dry conditions since then have seen the health of the forest and wetlands deteriorate. The MDBA ‘Basin Environmental Watering Priorities 2019-20’ identify Koondrook-Perricoota Forest as a priority site to receive water this year. A flow of around 500 ML/day is planned for delivery through September and October, with a total volume of around 30 GL expected to be delivered. This is expected to inundate approximately 4,500 ha, or just over 10% of the forest. Subscribe to the River Murray Weekly Report River Data website Water in Storages River Murray Weekly Report The diversion to National Channel averaged 1,300 ML/day this week. A portion of this flow is being used to maintain base flows through Gunbower Creek to benefit native fish. Much of this flow is returning to the River Murray at Barham via Koondrook spillway. The additional loss attributed to maintaining this higher flow in the creek is debited from Victorian held environmental entitlements. The Torrumbarry Weir pool is currently at Full Supply Level (FSL) (86.05 m AHD). Downstream of Torrumbarry Weir, the release is now increasing as flows arrive from upstream environmental watering actions. The release is currently near 10,700 ML/day and over the coming week will steadily rise to peak around 15,500 ML/day. Inflow from the Murrumbidgee River, measured at Balranald, is currently around the September end of system target of 1,330 ML/day. The Murrumbidgee IVT balance is currently 101 GL, and trade from the Murrumbidgee to the Murray is closed. Trade will remain closed until the account reduces below 85 GL. This could occur from trade from the Murray back to the Murrumbidgee, and/or from IVT deliveries from the Murrumbidgee to the Murray which are expected to commence in coming months. MDBA regularly reviews its operations planning to account for changes in catchment and climatic conditions as well as water availability. The increased water available to be delivered from the Murrumbidgee IVT account has been incorporated into this planning. Further information will be provided as part of the October update to the Annual Operating Outlook. At Euston, the weir pool level is currently 26 cm above FSL and is being slowly raised to target around 50 to 60 cm above FSL as part of the weir pool variability program. Varying pool levels helps restore a more natural wetting and drying cycle to riverbanks and adjacent wetlands within the influence of the weir pool. The downstream release averaged around 10,000 ML/day and is expected to start rising over the coming week as the environmental water continues its journey downstream.