The NSW government releases water for environmental purposes from all the dams it manages, including Chaffey and Copeton, to maintain a healthy river habitat.

WaterNSW spokesperson said environmental water releases had been gradually restricted, consistent with other types of water releases, as the drought impacts have intensified in affected valleys.

"There has been zero allocation to general security irrigators and environmental customers across many of the northern river valleys over the past few years, including the most recent 1 July allocations announcement," they said.

"This applies to licences held by environmental managers in the Peel valley and that valley's environmental contingency allowance."

WaterNSW said it was working closely with other agencies to determine the best times to do small periodic releases where possible, to avoid adverse environmental events such as the Menindee fish kill earlier this year.

However without significant inflows into the major drought zones in the state's north particularly, priority will increasingly be given to town supply and critical needs only.