The dams have collected about 4000 megalitres of water so far this month, well short of the 40,000 megalitres needed to lift allocation for holders of general security water licences.

This week the NSW Department of Primary Industries deputy director general water, Gavin Hanlon, told of likely water availability in the Macquarie and Cudgegong regulated rivers for the rest of the 2014/2015 water year and the start of the 2015/2016 water year, beginning July 1. Mr Hanlon said the general security allocation for the current water year remained at 2 per cent of entitlement, and further inflows would be required "before any general security allocation could be made in 2015/16".

"For example, an inflow of about 40,000 megalitres is required into storages in May before any additional general security allocations can be made," he said.

"Inflows so far this month total some 4000 megalitres."

The department's Office of Water forecasts full allocations in the new water year for holders of high security water licences covering town water supplies, domestic and stock needs. It also assured the delivery of remaining general security water into the new water year.

Average general security water carryover from the current water year to 2015/2016 is expected to be equal to about 5 per cent of entitlement, or 34,000 megalitres.

About 27,000 megalitres remains in the Environmental Water Allowance. The Office of Water reports of advice from the Bureau of Meteorology of a 65 to 75 per cent chance of average rainfall being exceeded in the region during May, June and July.

It also confirmed a "firming El Nino event in the tropical Pacific", expected to dominate the Australian climate during the second half of 2015.