Page 79 - VEWH Seasonal Watering Plan 2020-21
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Scope of environmental watering
The total volume planned for release to the Snowy River in 2020–21 is 91,476 ML2.
Due to operating rules in the system, the flow regime that will be delivered in 2020–21 is pre-planned: the storage manager will make daily releases of varying magnitude
from Lake Jindabyne between May 2020 and April 2021 to mimic the typical flow pattern of a mixed snowmelt/rainfall river system characteristic of the Snowy Mountains. The continuous daily releases will aim to support ecological processes in the Snowy River below Jindabyne Dam and maintain a healthy river that is much smaller than the natural channel that existed before the river was regulated.
Following several years of dry conditions resulting in
lower water availability, fewer high flow events and lower peak magnitudes are planned in 2020–21, but overall
flow patterns will be similar. Four high-flow releases are scheduled between June and November 2020. This includes a large flushing flow in early September 2020, which involves an eight-hour peak at a rate equivalent
to 4,500 ML per day. Other peak flows will mimic winter rainfall events. This variable flow regime aims to improve the physical attributes of the river by scouring and depositing sediment and increasing available aquatic habitat. High flows will be sustained from July to December, to help mix water in the estuary to benefit plants and fish (such as Australian bass). Low flows will then be released until the end of the water year in April 2021.
Daily releases from Lake Jindabyne will help to mitigate water quality impacts caused by rain that flushes in water from fire-damaged land; but due to the pre-planned annual flow regime process for this system, there is no opportunity to release environmental water in response to serious water quality risks.
East Gippsland CMA has monitored the lower reaches and estuary over the past eight years. The results show that the managed environmental flows help improve physical and ecological processes, increase ecosystem productivity and improve aquatic habitat.
2.5 Snowy system
             2 Including contributions from water savings in Victoria and New South Wales.
Victorian Environmental Water Holder | Seasonal Watering Plan 2020–21 | 77

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