Page 201 - VEWH Seasonal Watering Plan 2020-21
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Recent conditions
The 2019–20 year was characterised by extremely dry conditions throughout spring, although two small natural flow events originating from the Ovens and Kiewa rivers caused low-level flooding in the forest in mid- and late winter. Carryover in the Murray system from 2018–19 was essential to enable watering early in the year; Victorian Murray allocations increased slowly as a result of the dry conditions during 2019–20.
Forest regulators were opened in July 2019 to allow a natural connection between the Murray River and the waterways in Barmah Forest. Flow increased above the channel’s capacity in August 2019 as a result of rainfall
in upstream catchments. That event was followed by
the delivery of the ‘southern spring flow’ — a planned environmental flow event for the Murray River between
Lake Hume and the sea — which wetted low-lying parts
of the Barmah Forest floodplain through September and October 2019. Environmental flows reduced in late October, and forest regulators were closed at the end of October 2019. Most floodplain habitats within the forest dried during summer and autumn. The main exception was a small section of the forest that re-flooded in January 2020 as a result of vandalism to a forest regulator.
Watering actions for Barmah Forest were mostly delivered as planned in 2019–20. Maintaining winter/spring connection between the river and the forest enabled carbon and nutrient exchange and improved food resources and habitat for fish, frogs, turtles and waterbirds. The low-level flooding supported wetland plant growth, but it ended
too soon to stimulate some species to flower, due to insufficient water availability. A potential watering action that aimed to support colonial nesting waterbird breeding was not delivered, because significant natural breeding was not observed. Drying throughout the forest in summer/ autumn is important to maintain plant diversity and wetland productivity.
A prolonged, low-level, spring watering event in 2020–21
is desirable to allow more floodplain vegetation to flower, set seed and recruit. Waterbird breeding in Barmah Forest was at the lowest level in a decade in 2019–20 as a result of dry conditions. Providing flows to support a successful waterbird breeding event will be a priority in 2020–21. If conditions remain very dry, water for the environment will be mainly used to maintain critical drought refuges (such as waterholes in creek beds).
Scope of environmental watering
Table 5.2.1 describes the potential environmental watering actions in 2020–21, their functional watering objectives (that is, the intended physical or biological effect of the watering action) and the longer-term environmental objective(s) they support. Each environmental objective relies on one or more potential environmental watering actions and their associated physical or biological functions.
5.2 Victorian Murray system
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