Water for the environment for the Latrobe, Thomson and Macalister systems is held in Blue Rock Reservoir, Thomson Reservoir and Lake Glenmaggie respectively.
Environmental entitlements in these systems have unique characteristics that influence planning for environmental flows. The Thomson system receives a share of the daily inflows to the Thomson Reservoir and a secure annual allocation which is available on 1 July each year. In the Latrobe and Macalister systems, the availability of water for the environment depends on system inflows to Lake Glenmaggie and Blue Rock Reservoir. Winter and spring are the peak inflow periods for all systems, so annual allocations are usually well-known before the start of summer.
In dry years, waterway managers rely on carryover and early-season allocations to deliver the highest-priority environmental watering demands. In 2018–19, the Gippsland region experienced one of the driest and hottest periods on record. Environmental flows in 2018–19 were carefully managed to ensure a critical supply of water could be carried over for 2019–20.
The Gippsland system catchments will need significant rain in winter and spring 2019 to saturate the ground and generate substantial streamflow. Forecasts are for lowerthan- average rainfall across the region in winter 2019, and waterway managers are therefore preparing to enact environmental watering plans for dry to drought scenarios in 2019–20.
The volume of water needed to meet environmental demands in the Latrobe, Thomson and Macalister systems in winter/spring 2019–20 is similar to the volume required to meet demands for summer/autumn. As supply is mostly determined by winter/spring inflows, waterway managers will be able to confidently plan the supply of watering demands for the whole year by mid to late spring 2019.
Drought conditions could significantly limit allocations of water for the environment during 2019–20. Most tier 1 environmental watering priorities for the Thomson and Macalister rivers in 2019–20 can be achieved with the volume of water that is likely to be available in those systems, but supply is not assured for several high-priority (that is, tier 1b) environmental watering actions in the Latrobe system. If conditions remain dry, water for the environment will need to be carefully managed throughout the year to ensure there is enough carryover to meet critical demands in 2020–21. Where critical demands cannot be met by existing allocations, the VEWH and its program partners may investigate alternative supply options (such as transfers or trades). The VEWH also works with storage managers to identify opportunities to adjust the pattern of consumptive water deliveries to support environmental watering outcomes while still meeting the needs of consumptive water users.
The New South Wales Department of Planning, Industry and Environment plans and manages environmental flows in the Snowy system in consultation with Victorian and Australian governments and relevant stakeholder groups. The water year for the Snowy system starts in May and finishes in April the following year, which differs from how water is managed in the other Gippsland systems. The total volume for release and daily release targets for the Snowy River from May 2019 to April 2020 are set in place, and daily releases will not vary unless flows increase the risk of flooding downstream or operational constraints prevent delivery.