Regional Water Availability Report
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Regional water availability report Weekly edition 22 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 ...................................................................................................................................... 26 8. Rural Dam Levels .................................................................................................................................. 27 9. More Information .................................................................................................................................. 28 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 22 March 2021 was 49%. This is an increase of 0.4%. 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 22 March 2021 was 99.1%. This was an increase of 6.0% 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 pre-releases 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 maintained stream flows and inflows to the dams and from tributaries below dams. Water availability has increased in several valleys and operational plans are being reviewed as these inflows accumulate. Water availability weekly report 3 3. Climatic Conditions A strong high-pressure system over the southern Tasman Sea is directing humid easterly winds across New South Wales and is leading to heavy rain in many areas. Meanwhile, a low-pressure system over the centre of the state is moving southeast and is expected to be off the south coast tonight before moving to Bass Strait on Wednesday morning. The rain is expected to clear most of the state by tonight. Strong north easterly winds in the east will ease tonight as the low moves further south. A break from the wet conditions is expected on Wednesday apart from a few showers along the western ranges and slopes but fresh to strong westerly winds are expected in the southeast. The low will continue to move away to the southeast on Thursday as a ridge of high pressure moves across the state. For the first part of the week, much of the state is predicted to receive rainfall with falls of up to 100mm predicted. As the week progresses negligible rainfall is forecast across the coastal and southern regions. Figure 2a – First 4-day forecast (23 – 26 March 21) Figure 2b – Following 4-day forecast (27 – 30 March 21) Climate outlook overview Issued 18 March 2021 End of March and April likely to be wetter than average Water availability weekly report 4 • April to June is likely to be wetter than average (chance of exceeding median is more than 60%) across eastern parts of NSW. • The fortnight of 22 March to 4 April is likely to be wetter than average (chance of exceeding median is greater than 60%) over the eastern half of Australia. Parts of the east coast are very likely to be wetter than average (greater than 80% chance). Figure 3 – 3-month rainfall outlook ENSO Outlook (16 March) The ENSO Outlook remains at LA NIÑA, but there are several signs that this event is nearing its end. Oceanic indices have weakened in recent weeks with most returning to El Niño–Southern Oscillation (ENSO) neutral values, however, some atmospheric indices persist at La Niña levels. Latest model outlooks and observations indicate that the tropical Pacific will return to ENSO-neutral levels (neither El Niño nor La Niña) by mid-autumn. There is little sign that there will be a resurgence of the 2020−21 La Niña during the southern winter. The ENSO Outlook remains at LA NIÑA, but there are several signs that this event is nearing its end. Oceanic indices have weakened in recent weeks with most returning to El Niño–Southern Oscillation (ENSO) neutral values, however, some atmospheric indices persist at La Niña levels. Latest model outlooks and observations indicate that the tropical Pacific will return to ENSO-neutral levels (neither El Niño nor La Niña) by mid-autumn. There is little sign that there will be a resurgence of the 2020−21 La Niña during the southern winter. Despite weakening, La Niña is still likely to influence Australian rainfall patterns, with above average rainfall forecast for parts of eastern and northern Australia during April. Bureau climatologists will continue to closely monitor model outlooks and conditions in the tropical Pacific as this current La Niña event decays. 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 4,400 ML/d. The release will vary to meet the regulated flow demands. • Release downstream of Yarrawonga Weir is at approximately 9,100 ML/d and is likely to gradually decrease to about 7,000 ML/day over the next week. • The Edward River offtake flow (about 1,580 ML/d) will remain within channel capacity of 1,600 ML/d. • The Gulpa Creek offtake flow (230 ML/d) will remain below operational channel capacity of 250 ML/day. • Stevens Weir level is at approximately 4.60 m and will vary marginally to supply environmental water to Wakool system. Currently, the water level upstream of Wakool District Main Canal Regulator is approximately 1.79 m. • Flow downstream of Stevens Weir is approximately1,400 ML/d for MDBA flow requirements