Page 292 - VEWH Seasonal Watering Plan 2020-21
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 5.7 Loddon system
Scenario planning
Table 5.7.2 outlines the potential environmental watering and expected water use under a range of planning scenarios.
Up to three summer/autumn freshes and continuous
low flow are planned to be delivered in the Loddon River under all scenarios. These flows are critical for providing connectivity for aquatic animals and freshening water quality. A winter/spring high flow, timed to combine with increased flow in Pyramid Creek, is also planned to be delivered under all scenarios to trigger upstream movement of native fish from the Murray system for feeding and breeding.
Low flow is important for wetting bank vegetation and providing foraging habitat for aquatic animals. In the Loddon River, the magnitude of low flow is expected to vary between 25 to 100 ML per day, depending on conditions (and therefore changes in expected supply) and the time
of year. During winter/spring, continuous low flow of 50
ML per day is planned under a drought scenario. This will result in the accumulation of passing flows (as passing flows increase to 77 ML per day in May to October), for use later in the season. Under dry conditions, passing flows are expected to meet the winter low flow requirement, whereas under average and wet conditions, low flow will likely be increased to 100 ML per day. During summer and autumn, continuous low flow is planned to be as low as 25 ML per day in a drought-dry year but may be increased to 50 ML per day if conditions are average to wet. Contingency has been factored in to supply volumes under drought and dry scenarios to temporarily increase summer/autumn low flow magnitudes or the duration of freshes if required, to prevent dangerously low oxygen declines if extended heatwaves are forecast. If more water is available, it is planned to be used to further increase the magnitude of planned freshes and low flow to better align with the environmental flow recommendations. Autumn high flow to cue and support fish movement is a lower priority under a drought scenario compared to dry, average and wet scenarios.
Freshes and low flow are priorities across all seasons for Serpentine Creek under all scenarios. Lower anticipated supply under drought and dry conditions will likely restrict the number of summer/autumn freshes that can be delivered and restrict low flow to the lower end of the recommended range. The full number of recommended freshes and higher-magnitude low flow should be delivered if more water becomes available under these scenarios.
In Pyramid Creek, the highest-priority action under all scenarios is to deliver a spring high flow, which is intended to be timed to meet the peak of the high flow in the Loddon River at Kerang Weir. Coordinating these events provides flow of a sufficient magnitude to trigger native fish to move upstream from the Murray River toward Kow Swamp and Gunbower Creek for spawning and recruitment. Pyramid Creek carries a large volume of consumptive water during the irrigation season, but the flow can drop significantly outside the irrigation season. Under all scenarios, water for the environment will likely be used to supplement flow in late autumn and winter, to maintain habitat for fish and other aquatic animals during this period. Autumn high flow should be delivered under average and wet conditions, if sufficient water is available.
Up to 6,500 ML is prioritised for carryover into 2021–22. This water will help meet winter/spring low flow in all waterways and the spring high flow in the Loddon River.
    290 | Victorian Environmental Water Holder | Seasonal Watering Plan 2020–21

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