Regional Water Availability Report
Total Page:16
File Type:pdf, Size:1020Kb
Regional water availability report Weekly edition 29 March 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 ................................................................................................................... 22 7. Coastal valley based operational activities ..................................................................................... 24 7.1 Bega river .................................................................................................................................................. 24 7.2 Hunter valley ............................................................................................................................................. 25 7.3 Toonumbar Dam ...................................................................................................................................... 27 8. Rural Dam Levels .................................................................................................................................. 28 9. More Information .................................................................................................................................. 29 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 29 March 2021 was 52.6%. This is an increase of 3.6%. Please note that rural water supply figures now include Cochrane Dam, Lake Victoria and Lake Cargelligo. The total storage level of urban water supplies on 29 March 2021 was 99.3%. This was an increase of 0.2% 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 coastal and southern NSW storages, with the positive seasonal rainfall forecasts, 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 may also trigger poor water quality, particularly low dissolved oxygen for fish, as floodwaters may pick up significant amounts of accumulated leaf litter. Rainfall over most catchments in previous weeks has resulted in rises in stream flows and significant inflows into the dams and from tributaries below dams. The rainfall event has triggered supplementary events in Northern valleys, water availability has increased 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 as a result of the inflows. Water availability weekly report 3 3. Climatic Conditions A high-pressure system centred near Adelaide will drift slowly east during the next few days, to be over the Tasman Sea by Thursday. The presence of this system will promote stable weather across most part of New South Wales this week, with daytime temperatures gradually increasing and showers restricted to part of the northeast. A low-pressure trough looks set to cross from the west later in the weekend, potentially deepening off the northern coast early in the week. For the first part of the week, much of the state is predicted to remain dry with negligible rainfall forecast for the mid and north coastal regions. As the week progresses rainfall increases slightly along the coast and north eastern regions. Climate outlook overview Issued: 25 March 2021 April to June show no significant shift towards a wetter or drier three months (chances of exceeding median is close to 50%). The fortnight of 29 March to 11 April, parts of western NSW are likely to have a drier than average fortnight. Water availability weekly report 4 Figure 3 – 3-month rainfall outlook ENSO Outlook reset to INACTIVE as La Niña comes to an end – 30 March 21 The 2020−21 La Niña has ended, having been active since September 2020. The tropical Pacific Ocean has returned to near-normal temperatures, in line with the typical El Niño / La Niña life-cycle. Most model outlooks suggest a neutral El Niño-Southern Oscillation (ENSO) state (neither El Niño nor La Niña) is the most likely scenario through the remainder of the southern hemisphere autumn and winter. As a result of these changes, the ENSO Outlook has been reset to INACTIVE. An INACTIVE status means that the El Niño-Southern Oscillation (ENSO) is neutral and there are currently no indications that an El Niño or La Niña event will develop in the coming months. During this time, other drivers, such as the Madden-Julian Oscillation are likely to play a bigger role in influencing Australian rainfall patterns. 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 48 percent of active capacity and releasing 7,900 ML/d. The release will vary to meet the regulated flow demands. • Release downstream of Yarrawonga Weir is at approximately 6,950 ML/d and is likely to remain steady over the next week. • The Edward River offtake gates are not controlling the flows. The Edward River offtake flow (about 1,430 ML/d) will vary in line with the upstream levels in Murray River. • The Gulpa Creek offtake flow (240 ML/d) will remain below operational channel capacity of 250 ML/day. • Stevens Weir level is at approximately 4.63 m and will vary to supply environmental water to Wakool system. Currently, the water level upstream of Wakool District Main Canal Regulator is approximately 1.73 m. • Flow downstream of Stevens Weir is approximately 600 ML/d. The flow in the Edward River system is augmented by delivery via Edward River Escape (up to about 600 ML/day) of the Mulwala Canal to maintain the delivery targets below Stevens Weir. • Perricoota Escape is now closed. • Flows into Colligen Creek (target 170 ML/d), Wakool River (target is 80 ML/d) and Yallakool Creek (target is 280ML/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 200 ML/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 remain steady over the week. • Flow in Wakool River at Stoney Crossing is currently