The Waitaki River will be flushed next week when Meridian Energy releases 950cumecs of water down the river.
The river's mean flow is about 350cumecs at the Waitaki dam.
Meridian Energy has been spilling water from southern hydro-electricity lakes following significant rainfall in the catchment.
External relations manager Claire Shaw said yesterday Meridian was in the unusual position of having "quite a bit of water".
Meridian had been consulting Environment Canterbury, the Department of Conservation and Fish and Game, with potential benefits recognised for flushing the river.
It was intended to provide a flow of 950cumecs for a 24-hour period starting on Monday.
Meridian would start to provide more water into the Waitaki, from Benmore, at 6am and it should be up to 950cumecs by midday, Miss Shaw said.
Environment Canterbury duty flood controller Tony Henderson said the river could handle the high flow.
The only concern was for recreational users to be aware the river would be rising.
