The Snowy River has its headwaters in the montane areas of the Snowy Mountains, and flows 380 km to the sea by the Victorian town of Marlo. The River is largely dependent for flow on the catchment above Jindabyne due to a rain shadow effect on the tablelands. For instance, mean annual rainfall varies with up to 2000 mm in the Snowy Mountains and less than 500mm in the rain shadow affected areas around Dalgety.

The Snowy Mountains Scheme captures and diverts the waters of 12 rivers and 71 creeks. It includes 16 dams, 18 aqueducts, 19 trans-mountain tunnels, 7 power stations and 2 pumping stations. The Scheme has diverted approximately 99% of the Snowy River’s natural flow below Jindabyne Dam.

Under current water release arrangements, the Scheme is required to provide a minimum of 2,088 GL of regulated water to the Murray and Murrumbidgee systems each year. However, on average, it actually provides long term releases of 2,410 GL. The average annual release into the Murray is 1,200 GL and 1,210 GL into the Murrumbidgee. Approximately half of this water is from the Snowy River catchment (long term average flow is approximately 1,150 GL) and half is water which would flow into these systems naturally but has been regulated by the Scheme.

The annual diversion and storage of water from the Snowy River increases the availability of water in the western rivers and provides drought insurance to irrigation schemes located in the Murray and Murrumbidgee valleys.

The Snowy-Murrumbidgee portion of the Scheme provides on average 25% of the flow in the Murrumbidgee River, which increases to around 60% during drought periods. The reliability of the Scheme has underpinned primary production. The Snowy-Murray portion of the Scheme provides an average of about 10% of the flows to the Murray system but during periods of drought its contribution can rise to about 33%.

The Snowy Mountains Hydro-Electric Authority is in the process of being corporatised. As part of this process, the NSW and Victorian governments sponsored the ‘Snowy Water Inquiry’ to examine and report on environmental issues from the current pattern of water flows in the Snowy Mountains region, including environmental flows. The Inquiry recommended that 15% of the original flow of the Snowy River be restored immediately below Jindabyne Dam.

Since the release of the Snowy Water Inquiry’s Final Report, there has been constant debate in the community and media on the appropriateness of restoring environmental flows to the Snowy. The issue is complicated by the fact that there are three governments who must agree on the final decision – the Victorian, NSW and Commonwealth, and any decision may impact on the drinking water of South Australia, so the South Australian Government has also been active in the debate.