New South Wales is well behind on developing water sharing plans for its rivers, and is unlikely to meet June deadlines, putting in doubt its claims that water is being shared fairly between farmers and the environment.

Water resource plans set the detailed rules for sharing water between irrigators and the environment in each catchment and NSW is yet to submit first drafts of 12 of 20 required plans, instead operating under old unaccredited plans.

The NSW minister for primary industries, Niall Blair, denied on Tuesday there was a problem of over-allocation in NSW, saying the primary cause of falling dam levels and low flows was the drought.