Page 77 - VEWH Seasonal Watering Plan 2020-21
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System overview
The Snowy River originates on the slopes of Mount Kosciuszko. It drains the eastern slopes of the Snowy Mountains in New South Wales (NSW) before flowing through the Snowy River National Park in Victoria and into Bass Strait.
There are four major dams and multiple diversion weirs in the upper Snowy River catchment that divert water to the Murrumbidgee and Murray River valleys. The hydrological effects of the Snowy Mountains Scheme are substantial, but they are partly alleviated by the contribution of flows from tributaries (such as the Delegate River in NSW and the Buchan and Brodribb rivers in Victoria).
Construction and operation of the Snowy Mountains Hydro-electric Scheme previously diverted 99 percent of the Snowy River’s mean annual natural flow at Jindabyne. The loss of flow changed the structure and function of the river, reduced the opening of the Snowy River entrance to Bass Strait and resulted in a decline in environmental values.
The Victorian, NSW and Commonwealth governments have recovered water to help restore damage done by decades of limited flow. Victorian water for the environment available for use in the Snowy system is held in the Murray, Goulburn and Loddon systems. This water is made available for environmental flows in the Snowy River via a substitution method, whereby Victorian water for the environment replaces water that was earmarked for transfer from the Snowy to Victoria to support irrigation demands. The
NSW Department of Planning, Industry and Environment
Recent conditions
Drought conditions in 2018–19 resulted in reduced environmental flow allocations for the Snowy River in 2019–20, which resulted in smaller peaks to high flows and shorter durations of freshening flow events. The Snowy River catchment continued to experience below-average rainfall and above-average temperatures throughout 2019–20. Below-average inflows to Lake Jindabyne occurred, which similarly have influenced the magnitude and duration of high flow events in 2020–21. In Victoria, most of the Snowy River catchment experienced below- average rainfall and above-average temperatures for most of 2019–20, with this easing to average conditions in autumn 2020.
The water year in the Snowy system runs from May to April. In 2019–20, approximately 117,871 ML1 of water for the environment was used to deliver five winter/spring high-flow events in the Snowy River. A major flushing flow occurred in October 2019.
The Snowy River catchment above Lake Jindabyne in NSW was not severely impacted by the widespread bushfires
in south-eastern Australia in December 2019 and January 2020. The catchment area within Victoria, particularly near the estuary mouth in East Gippsland, was severely burnt. If there is heavy rainfall in fire-damaged catchments, it is likely to flush sediment and ash into waterways and degrade water quality in the Snowy River, which may have flow-on effects for river ecology in 2020–21.
 plans environmental flow releases in the Snowy River, in consultation with the Victorian Government.
Environmental values
The remaining environmental values in the upper reaches and tributaries of the Snowy River include freshwater fish (such as river blackfish and Australian grayling). The lower reaches support estuary perch and Australian bass that move between saltwater and freshwater systems. The estuary contains estuarine and saltwater species such as flathead and black bream. The floodplain wetlands of the Snowy River near Marlo provide feeding and breeding areas for wetland and migratory birds.
        1 Preliminary figure of total releases in 2019–20. This volume may alter slightly due to accounting adjustments, and it will be verified in Snowy Hydro Limited’s annual water operating plan.
Victorian Environmental Water Holder | Seasonal Watering Plan 2020–21 | 75
2.5 Snowy system

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