Page 212 - VEWH Seasonal Watering Plan 2020-21
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 5.2 Victorian Murray system
Scenario planning
Table 5.2.6 outlines the potential environmental watering and expected water use under a range of planning scenarios.
The highest-priority potential watering actions under all conditions in 2020–21 are to fill and provide top-ups to Reedy Lagoon and Black Swamp in winter/spring 2020. These are permanent wetlands, and water is needed to support the growth and recruitment of wetland plants as well as provide feeding and breeding habitat for small- bodied native fish, frogs, turtles and waterbirds. If a waterbird breeding event commences in any wetland, top- ups may be needed to maintain water depth and habitats through spring and summer until juvenile waterbirds have fledged. Additional top-ups may be delivered to Reedy Lagoon and Black Swamp in autumn/winter 2021 if dry conditions are expected in 2021–22, to provide refuge over winter for water-dependent animals including waterbirds. Providing the prescribed low flow to Gunbower Creek in
all seasons is also a high priority under all scenarios, to maintain and improve populations of native fish.
Under the dry, average and wet scenarios, the environmental watering priorities will be to maintain and improve the condition of semi-permanent and permanent wetlands across the forest and support local populations of waterbirds, frogs, small-bodied fish and turtles. Delivering top-ups and fills to selected wetlands within the Little Gunbower and Little Reedy wetland complexes in autumn/ winter 2021 will provide habitat for waterbirds and other water-dependent animals during the cooler months and prime the wetlands for a spring productivity boost. If flow
in the Murray River exceeds 15,000 ML per day for more than two weeks in winter/spring, a fresh may be delivered
in Yarran Creek to allow carbon, fish, turtles and seed propagules to move between Gunbower Creek, Gunbower Forest and the Murray River. Delivering water for the environment to the Gunbower Forest floodplain in autumn/ winter 2021 is a high priority under the dry, average and wet scenarios, to maintain and improve the health of river red gums and provide waterbird and native fish habitat.
Under average and wet conditions, natural flow from
the Murray River may wet parts of the Gunbower Forest floodplain in winter/spring 2020. Water for the environment may be used to extend natural flooding events in selected river red gum areas, to maintain and improve tree health.
If significant volumes of water for the environment are delivered to Gunbower Forest via the Hipwell Road Regulator, it may not be possible to deliver the full range
of flows to increase the large-bodied fish population in Gunbower Creek. If so, flow in Gunbower Creek will be managed to maintain habitat for the existing native fish population. Low flow may be increased to the upper end
of the recommended range — 500 ML per day — to dilute low-oxygen floodwater that drains from the floodplain below Koondrook Weir following a natural or delivered floodplain watering event.
Water for the environment may also be used to temporarily increase flow in Gunbower Creek to the upper end of the recommended flow range — 500 ML per day— in response to higher flows in the Murray River that occur at important times for fish breeding or movement. These high Murray River flows are expected to mainly occur under a wet scenario.
There is a possibility that Goulburn-Murray Water will require Gunbower Creek to be shut down during winter/spring 2021 to allow for the construction of fishways at Koondrook Weir and Cohuna Weir outside the irrigation season. If
these works proceed as planned, water will be delivered at a low rate to maintain some pool habitats for resident fish populations, but higher flows to the creek and deliveries to Gunbower Forest via the Hipwell Road Regulator will not be possible. Any potential watering actions that are cancelled as a result of those works will likely become a very high priority to deliver in 2021–22.
A minimum volume of 21,000 ML is planned to be carried over into 2021–22. The carryover volume will provide certainty of supply for low flow in Gunbower Creek during the non-irrigation season to maintain flowing habitat and support top-ups of permanent wetlands in lower Gunbower Forest. Extra water may need to be carried over to support any Gunbower Forest floodplain watering actions that commence in autumn or June 2021.
210 | Victorian Environmental Water Holder | Seasonal Watering Plan 2020–21

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