The Jindabyne Dam's gates have opened, starting the largest environmental flow into the Snowy River in almost 40 years.


The release of 84,000 megalitres started last week and will peak this week with the opening of the radial gates on Jindabyne Dam to increase flows to 12,000 megalitres a day.


The water is designed to flush the upper reaches of the Snowy where for the past 10 years flows have remained extremely low.


Victorian Water Minister Peter Walsh said that  although more than 50 per cent of the Snowy's flows still run out to sea via unregulated tributaries on Victoria's side of the border, there would still be some ecological benefit from the release.


"The release imitates the natural flows which would usually occur in the river at this time of the year as the snow melts on the mountains.


"The flush of water will occur over 19 days with the peak flows expected to last for three days.


"After years of drought, good rainfall this year has enabled us to deliver water against the Snowy's entitlement," Mr Walsh said.


Mr Walsh said the release was the culmination of an agreement by the Victorian, New South Wales and Australian governments to return flows to the Snowy River.


"In 2002 the Victorian, New South Wales and Australian Governments committed to returning 21 per cent of average natural flows by 2012," Mr Walsh said.