Regional water availability report Weekly edition 25 May 2020 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 .................................................................................... 10 5.1 Lachlan valley ........................................................................................................................................... 13 5.2 Macquarie valley ..................................................................................................................................... 10 6. Northern valley based operational activities ................................................................................. 18 6.1 Namoi valley ............................................................................................................................................. 19 6.2 Gwydir valley ............................................................................................................................................ 21 6.3 Border rivers ............................................................................................................................................... 22 6.4 Barwon-Darling River system ................................................................................................................... 22 7. Coastal valley based operational activities ................................................................................... 27 7.1 Bega river .................................................................................................................................................. 27 7.2 Hunter valley ............................................................................................................................................. 28 7.3 Toonumbar Dam ...................................................................................................................................... 30 8. Rural Dam Levels ............................................................................................................................... 31 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 25 May 2020 was 31.1% of the total active storage capacity. This was an increase of 0.7% since last week. The total storage level of urban water supplies on 25 May 2020 was 81.8% of the total storage capacity. This was an increase of 0.1% since last week. 2. System risks Inflows adding to over 565 GL are continuing to flow into Menindee Lakes over the next few weeks and releases to the Lower Darling have reached the Murray River. The relatively small inflows to most northern dams mean that drought measures and works are being reviewed, but most will likely remain in place, despite the large flows downstream. This is particularly the case for Chaffey, Split Rock, and Wyangala Dams, where the risks to critical needs remains high. Risks are also increasing in the Hunter Valley as inflows to Glenbawn and Glennies Ck Dams continue to track well below previous drought records. Water availability weekly report 3 3. Climatic Conditions Figure 1 - Weekly rainfall totals for New South Wales This week’s weather forecast A deep low pressure system over the Tasman Sea is bringing large surf as well as windy, cool and wet weather to parts of the east. This low is expected to linger offshore, gradually weakening and moving a little further north during Tuesday and Wednesday, before moving away to the east mid- week as a trough skims the south of the state. Meanwhile, a high pressure system near Tasmania extends a ridge across the state's west. Figure 2a – First 4-day Forecast (26 – 29 May 2020) Figure 2b – Following 4-day forecast (30 May – 2 June 2020) Water availability weekly report 4 Rainfall for the fortnight 30 May to 12 June is likely to be average across western NSW. There is a much higher chance of a wetter than average June to August for western NSW. Figure 3 – 3-month rainfall outlook Water availability weekly report 5 4. 4Southern valley based operational activities 4.1 Murray Valley Storage and release status • Hume Dam is currently 24% of active capacity, and at min releases of 600ML/d. • Release downstream of Yarrawonga Weir are at about 6,000ML/day and likely to remain steady over the week. • The Edward River Offtake flow is currently about 1,200 ML/d and is likely to recede further as Murray flows recede. • The Gulpa Creek Offtake flows are at about 220ML/d and is likely to recede over the coming days. • Stevens Weir level is about 4.51m and will marginally vary. Water level upstream of Wakool Canal offtake is about 1.83 m. • Forest regulators have been closed with the falling river levels. • Flow downstream of Stevens Weir is about 2,100 ML/day and is likely that flows return to within channel capacity but remain close to channel capacity as Murray Irrigation commenced drainage of their channel system. • Flows in the Colligen Creek (350ML/day), Yallakool Creek (420ML/day) and Wakool River (50ML/day) and flows are likely to remain relatively steady. On top of the above, MIL is escaping about 100ML/day into the Wakool River. • Flow in Niemur River at Mallan School is currently about 450ML/d and increasing. Flow will continue to rise due to flow via Werai forest through this week. • Merran Creek flows upstream of its confluence with Wakool is about 200 ML/day and is likely to gradually increase this week. • Flow in Wakool River at Stoney Crossing is currently at about 730 ML/day and is likely to gradually increase this week. • Flow at Balranald is currently about 786 ML/d and will fluctuate over the next week. The end of system target at Balranald for the month of May is 297ML/day. • Lake Victoria is currently holding about 406 GL or 53% of active capacity. The flow to South Australia is about 5,700ML/d. Environmental water operations • eWater delivery has now ceased into Wakool-Yallakool system and into Colligen-Niemur system. Water availability weekly report 6 Water availability • The latest Murray Water Allocation Statement 15 May 20 confirmed that general security allocation have increased by 3 per cent. Drought operation measures • The NSW Murray regulated river water source has remains at Stage 2, meaning drought operational planning has commenced in preparation for extreme dry conditions that may continue through 2020-21. Water quality • Potential Blue Green Algae issues: – Recent Blue Green Algae (BGA) sampling at Lake Hume shows Lake Hume is on a Green alert level. The sites at Heywoods and Ebden indicate Amber alert level. – For more information visit: Water Quality Algae Planned supply interruptions: • Maintenance activities are underway in the Stevens weir gates and super structure under the Coatings Programme. However, the maintenance activity is not expected to impact the normal river operations and Weir levels. Water availability weekly report 7 4.2 Lower Darling valley Storage and release status • Menindee Lakes system collectively holds about 27% of total capacity, and is releasing about 220 ML/d. • The status of individual lakes: Lake Wetherall - 67%, Tandure – 84%, and Lake Pamamaroo – 118%, Copi Hollow – 133%; while Lakes Menindee and Cawndilla remain dry. • As per the Water Sharing Plan, the planned minimum flows for the months of May and June will be 200 ML/day measured at Weir-32. • Water is being transferred from Lake Wetherell to Lake Pamamaroo to equalise the level in these sections of the storage. The purpose of this is to minimise the surface area and area of inundation for the volume in storage, therefore minimising losses from the storage system. The transfer is as per standard filling procedure. • Inflows to the lakes commenced on 10 March 2020 and so far about 642 GL (with updated ratings) has reached Wilcannia. • Current forecast in the Barwon-Darling system indicates that in total about 570 GL is expected to reach the lakes including the water in transit. Water availability • To date the current inflows have not resulted in the storage volume reaching 640GL and are currently not forecast to reach this trigger in the current event.