Page 239 - VEWH Seasonal Watering Plan 2020-21
P. 239

Scenario planning
5.2.15 outlines the potential environmental watering and expected water use under a range of planning scenarios.
There are two categories of planned environmental watering opportunities for Lindsay, Mulcra and Wallpolla islands in 2020–21:
• environmental watering of anabranch waterways (Mullaroo Creek, Lindsay River and Potterwalkagee Creek) and floodplain wetlands in coordination with operation of weir pools
• a program of small-scale pumping to deliver water to individual wetlands at Lindsay and Wallpolla islands.
Of the waterways and floodplain wetlands connected to the weir pools, the only sites proposed to receive environmental water under all planning scenarios are Mullaroo Creek and Websters Lagoon. Even under drought conditions, it is essential to provide flows to Mullaroo Creek to maintain flowing water habitat for large-bodied native fish. Websters Lagoon can be efficiently managed via a regulator to provide an annual wet-dry cycle under all scenarios.
Under an average scenario, environmental water may be delivered to Lindsay River and Potterwalkagee Creek in spring, when locks 7 and 8 will be at suitable levels. These locks are expected to be lowered during summer/autumn under an average scenario and all year under a drought
or dry scenario, which will prevent flow into Lindsay River and Potterwalkagee Creek. No environmental watering is planned for these systems under a wet scenario, because natural flows and floods are likely to meet all ecological watering requirements.
Water for the environment may be pumped to up to nine high-priority wetlands and ephemeral creek lines across Lindsay and Wallpolla Islands in 2020–21. Water will need to be pumped directly into Wallpolla Horseshoe under drought, dry and average scenarios, but it is expected to fill naturally under a wet scenario. Other wetlands on Lindsay and Wallpolla islands are likely to need active watering under dry and average scenarios. Most of these wetlands will likely be watered in spring 2020, but pumping at Lake Wallawalla is planned to commence in autumn 2021 under average and wet scenarios and continue through to late spring 2021. All sites are expected to receive natural inflows under a wet scenario; but if only minor-to-moderate flooding occurs, pumping may still be required to reach target water levels in Lake Wallawalla and Wallpolla Creek East.
Additional environmental watering priorities (tier 2) have been identified for Lindsay and Mulcra islands wetlands
and floodplain under dry and average scenarios. The tier
2 priorities identified are critical to achieving environmental objectives at the site in the long term and could be delivered in 2020–21 if circumstances allow, but they could be deferred without significant environmental harm.
5.2 Victorian Murray system
  Victorian Environmental Water Holder | Seasonal Watering Plan 2020–21 | 237

   237   238   239   240   241