Regional water availability report Weekly edition 16 March 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 ..................................................................................... 13 5.1 Lachlan valley ........................................................................................................................................... 13 5.2 Macquarie valley ..................................................................................................................................... 13 6. Northern valley based operational activities ................................................................................... 18 6.1 Namoi valley ............................................................................................................................................. 19 6.2 Gwydir valley ............................................................................................................................................ 22 6.3 Border rivers ............................................................................................................................................... 24 6.4 Barwon-Darling River system ................................................................................................................... 24 7. Coastal valley based operational activities ..................................................................................... 30 7.1 Bega river .................................................................................................................................................. 30 7.2 Hunter valley ............................................................................................................................................. 31 7.3 Toonumbar Dam ...................................................................................................................................... 32 8. Rural Dam Levels .................................................................................................................................. 33 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 16 March 2020 was 24.5% of the total active storage capacity. This was an increase of 0.3% since last week. The total storage level of urban water supplies on 16 March 2020 was 82.6% of the total storage capacity. This was an increase of 0.1% since last week. 2. System risks Rainfall totals for February of between 100mm and 300mm in the northern Murray Darling has led to some extended rises in stream flows, particularly downstream of the dams. The northern basin Section 324 Temporary Water Restriction for A, B & C Class have been lifted as forecasts indicate the water in transit will meet critical water needs through the entire Barwon-Darling system and to the junction of the Murray River at Wentworth. https://www.industry.nsw.gov.au/water/allocations- availability/temporary-water-restrictions Inflows of over 260 GL are forecast to reach Menindee Lakes, from mid-March and planning has commenced on options for managing this water through Lake Wetherell to the Murray. The recommencement of flow increases the possibility of decreasing water quality and fish deaths, with initial increases in salinity, pH, and reduced dissolved oxygen. 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. Water availability weekly report 3 3. Climatic Conditions Figure 1 - Weekly rainfall totals for New South Wales This week’s weather forecast A high pressure system west of Tasmania is extending a ridge along the coast. This high will gradually move into the southern Tasman Sea during Monday bringing showers to eastern districts into the new week. Meanwhile Tropical Cyclone Gretel has formed in the Coral Sea and is forecast to track southeast towards Norfolk Island today. Figure 2a – First 4-day Forecast (16 - 19 March 2020) Figure 2b – Following 4-day forecast (20 - 23 March 2020) Rainfall for the fortnight 16 March to 29 March is likely to be below average across NSW. Water availability weekly report 4 There is a now a slightly higher chance of a wetter than average April to June for most parts of 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 16% of active capacity, and releasing about 4,600ML/d. • Release downstream of Yarrawonga Weir has reduced to about 5,000ML/day. • The Edward River Offtake flow is currently about 1,300 ML/d and is likely to fall in line with flow in the Murray river below Yarrawonga. • The Gulpa Creek Offtake flows are at about 180ML/d and will remain below 200 ML/day. • Stevens Weir level is about 4.51m and will marginally vary. Water level upstream of Wakool Canal offtake is about 1.83m. • Flow downstream of Stevens Weir is about 900 ML/day. The target is likely to be revised downwards in the coming days. • Flows in the Colligen Creek (170ML/day), Yallakool Creek (220ML/day) and Wakool offtake (25ML/day) are likely to remain steady. • Flow in Niemur River at Mallan School is currently about 120ML/d and is likely to remain steady. • Merran Creek flows upstream of its confluence with Wakool is about 130 ML/day and is likely to remain steady during the week. • Flow in Wakool River at Stoney Crossing is currently at about 390 ML/day and is likely to reduce marginally to 340ML/day over the week. • Flow at Balranald is currently about 890 ML/d and will gradually reduce to about 830 ML/day as Inter Valley Trade water will be delivered on top of the end of system targets until end of March 2020. The average IVT clearance rate in March is targeted to about 650ML/d. • Lake Victoria is currently holding about 258GL or 27% of active capacity. The flow to South Australia is about 6,200ML/d. Environmental water operations • eWater delivery continues into Wakool-Yallakool system and into Colligen-Niemur system to match a specific hydrograph requested by environmental water managers to support fish habitat and water quality aspects. However, when the system demands are higher than the eWater flows then the diversions will increase to match the system demands. Water availability • The latest Murray Water Allocation Statement dated 16 march 2020 confirmed that general security allocation remains unchanged. As dry conditions continue to strain resources, the Water availability weekly report 6 system is being managed to maintain deliverability of all account water and support full opening allocations to high priority needs in 2020-21. The improvement in the NSW Murray resource of 20,000 megalitres due slightly increased inflows above the minimums has been set aside for 2020-21 high priority needs (15,000 ML) and to reduce the current year’s shortfall to Conveyance entitlement holders (5,000 ML). Drought operation measures • The NSW Murray regulated river water source has advanced to Stage 2, meaning drought operational planning has commenced in preparation for extreme dry conditions that may continue through 2019-20. Water quality • Potential Blue Green Algae issues: – Recent Blue Green Algae (BGA) sampling shows a Red alert at Murray River at Merbein (N1027), at Buronga (N1062), at Curlwaa (N1063) and at Fort Courage (N1066) – Recent Blue Green Algae (BGA) sampling shows an Amber alert downstream of Yarrawonga Weir (N1007), at Cobram (N1051), at Picnic Point (N1052) and at Tocumwal (N1013) – Recent Blue Green Algae (BGA) sampling at Lake Hume shows Lake Hume a Red 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 • Significant rainfall recorded