Page 279 - VEWH Seasonal Watering Plan 2020-21
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Scenario planning
Table 5.6.2 outlines the potential environmental watering and expected water use under a range of planning scenarios.
For 2020–21, the highest-priority environmental flows
are low flow in summer/autumn and winter/spring and delivering a year-round fresh (if needed) under all conditions (see tier 1a actions in Table 5.6.2).
Low flow in summer/autumn is critical for maintaining the river at a level that flushes high-salinity water from pools and maintains oxygen concentrations at a level that can support native fish and waterbugs. Under drought and
dry conditions, the amount of water available for the environment is not likely to be sufficient to deliver the recommended winter/spring low flow watering action,
and therefore a reduced magnitude low flow is proposed
to ensure continuous flow is maintained year-round. The reduced magnitude winter/spring low flow will maintain riffle and pool habitats and water quality in all reaches but may not achieve objectives for streamside vegetation or allow fish and platypus to move freely throughout each reach. Delivering the full winter/spring low flow is a high priority under wet and average scenarios.
The other potential watering actions under average and wet scenarios are summer/autumn freshes and winter/spring freshes. Year-round freshes are a potential watering action as well; when there are low oxygen levels in the river, these will help improve water quality and help de-stratify pools in reach 4, to support aquatic animals.
Any additional water available under the drought or dry scenarios should be used to increase the magnitude of winter/spring low flow (tier 1b). Winter/spring freshes have been identified as tier 2 priorities under the drought and dry scenarios, and an additional winter/spring fresh is identified as a tier 2 watering action under the average scenario. These freshes will improve the condition of environmental values in the Campaspe River, but if there is insufficient water to deliver these freshes, that will not be to the detriment of the system’s environmental values in 2020–21. Carryover into 2021–22 is not a priority this year, because sufficient allocation from a very high-reliability entitlement is expected to be available on 1 July 2020 to meet minimum critical demands.
5.6 Campaspe system
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