Regional Water Availability Report Weekly Edition 10 May 2021
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Regional water availability report Weekly edition 10 May 2021 WaterInsights now presents most of the content from this report and is updated in real time. This report will be phased out over coming weeks. To assist this transition to WaterInsights this report includes links to the relevant sections on WaterInsights. 1 Contents 1. Overview ................................................................................................................................................. 3 2. System risks ............................................................................................................................................. 3 3. Climatic Conditions ............................................................................................................................... 4 4. Southern valley based operational activities ..................................................................................... 6 4.1 Murray Valley .............................................................................................................................................. 6 4.2 Lower Darling valley ................................................................................................................................... 8 4.3 Murrumbidgee valley ............................................................................................................................... 10 5. Central valley based operational activities ..................................................................................... 13 5.1 Lachlan valley ........................................................................................................................................... 13 5.2 Macquarie valley ..................................................................................................................................... 15 6. Northern valley based operational activities ................................................................................... 17 6.1 Namoi valley ............................................................................................................................................. 17 6.2 Gwydir valley ............................................................................................................................................ 19 6.3 Border Rivers .............................................................................................................................................. 20 6.4 Barwon-Darling River system ................................................................................................................... 21 7. Coastal valley based operational activities ..................................................................................... 23 7.1 Bega river .................................................................................................................................................. 23 7.2 Hunter valley ............................................................................................................................................. 24 7.3 Toonumbar Dam ...................................................................................................................................... 25 8. Rural Dam Levels .................................................................................................................................. 26 9. More Information .................................................................................................................................. 26 Water availability weekly report 2 1.Overview WaterNSW manages and operates 42 dams and storages to deliver water for environmental, domestic, town water, stock, industrial and irrigation purposes across the state. WaterNSW storages provide supplies to all the major river systems in Western NSW, Greater Sydney, the Southern Highlands, Shoalhaven Bay as well as the Hunter, Bega, and Iron Pot valleys in coastal NSW. The total active storage percentage of rural water supplies on 10 May 2021 was 58.03%. Which is an increase of 1.03% since last week. The total storage level of urban water supplies on 10 May 2021 was 99.1 %. This was an increase of 3.5% since last week. 2.System risks Algal alerts are current for many storages and river sections. Algae WaterNSW is working with BOM in assessing the likelihood of filling NSW storages, with high storage levels and wet catchment conditions, and preparing for airspace operations and flood operations. All floodplain landholders are recommended to review their flood operations plans and be aware of any notifications from BoM and SES. WaterNSW is working with DPIE-W and Snowy Hydro to reduce the risks of filling and spilling Blowering and Burrinjuck Dams this winter/spring. This includes limiting releases from Snowy into Blowering Dam, while ensuring water availability for next year. Any floods and floodplain flows that occur in the coming months, including the current flood flows in the Barwon-Darling system, may also trigger poor water quality, particularly low dissolved oxygen for fish, as floodwaters may pick up significant amounts of accumulated leaf litter. Forecast inflows to Menindee lakes from the current flows in the Upper Darling River and tributaries are expected to be approximately 800-1,000 GL. Recent rainfall over most catchments has resulted in increased allocation in most valleys and the additional inflow is likely to contribute to the commencing allocations in the next water year. Operational plans are being reviewed because of the inflows. Essential maintenance activities are planned across most valleys as irrigation demand is dropping over next few months. Water availability weekly report 3 3.Climatic Conditions A cold front is bringing a cold southwest to southerly change to southern and western New South Wales. A high-pressure system will be centred near Tasmania later today in the wake of the front, with low pressure troughs subsequently developing over the inland of New South Wales and off the coast. By Wednesday the high should be over the southern Tasman Sea and the low-pressure troughs will continue to affect the state. For the first part of the week, the coastal regions of the state are predicted to receive negligible rainfall, with higher falls of up to 25mm predicted for the far northern and southern regions. The central to western regions are predicted to remain dry. As the week progresses the state is predicted to remain dry apart for negligible rainfall along the coastal fringes. Figure 2a – First 4-day forecast (11 – 14 May 21) Figure 2b – Following 4-day forecast (15–18 May 21) Climate outlook overview Issued: 6 May 2021 Rainfall for winter (June to August) is likely to be above average for NSW (chance of exceeding median is greater than 60%). Eastern parts of NSW have roughly equal chances of above or below average rainfall (chance of exceeding median is close to 50%). The outlook pattern for June is similar to winter, but much of eastern Australia has only slightly increased chances of above average rainfall. Water availability weekly report 4 ENSO Outlook: INACTIVE The ENSO Outlook is INACTIVE. This means the El Niño–Southern Oscillation (ENSO) is neutral with no indication that El Niño or La Niña will develop in the coming months. During this time, other influences, such as the Madden–Julian Oscillation or localised sea surface temperatures, are likely to play a bigger role in affecting Australian rainfall patterns. All seven climate models surveyed by the Bureau suggest a neutral ENSO state is the most likely scenario through the remainder of the southern hemisphere autumn and winter. Bureau climatologists routinely monitor the tropical Pacific for any signs of developing ENSO events, regardless of the ENSO Outlook status. Water availability weekly report 5 4.Southern valley based operational activities 4.1 Murray Valley Storage and release status on: WaterInsights Hume Dam is currently at 42 percent of active capacity and releasing 5,167 ML/d. The release will vary to meet the regulated flow demands. Release downstream of Yarrawonga Weir is at approximately 4,400 ML/d and is likely to decrease over the next week. The Edward River offtake flow (about 1,200ML/d) will decrease in line with Yarrawonga decreasing flows. The Gulpa Creek offtake flow (220 ML/d) and will remain below the channel capacity of 240 ML/d. Stevens Weir level is at approximately 4.60 m and will vary to supply environmental water to Wakool system. Planning is underway to lower the Stevens for winter maintenance starting from 15 May 2021, when the diversion to Wakool Main Canal of Murray Irrigation Limited will cease. Currently, the water level upstream of Wakool District Main Canal Regulator is approximately 1.787 m. Flow downstream of Stevens Weir is approximately 600 ML/d. The flow will reduce over the week to about 600/day. Flows into Colligen Creek is about 164 ML/day (target 170 ML/d), Wakool River is 38 ML/day (target is 30 ML/d) and Yallakool Creek flow is 143 ML/day (target is 170ML/d) will be varied to meet the operational requirements and to match the hydrograph required for the environmental water delivery in the Wakool River. Flow in the Niemur River at Mallan School is currently at approximately 180ML/d and will remain steady over the week. Merran Creek flow upstream of its confluence with Wakool is approximately 50 ML/d with the flow forecast to increase gradually over the week. Flow in Wakool River at Stoney Crossing is currently at approximately