Four weeks into a six-week Murray-Darling Basin Commission watering at the Narran Lakes system has already resulted in a huge boost to the environmental health of the system's plants and animals, particularly its birdlife.

The MDBC bought 11,000 megalitres of water over the Easter weekend to supplement the natural watering occurring at the internationally important Ramsar wetland site in north central New South Wales.

MDBC chief executive, Dr Wendy Craik, said today that expert ground surveys were showing that about 75pc of the 30,000 pairs of straw-necked ibis attracted to the lakes since January were now expected to successfully produce healthy, full-fledged offspring.

"Many of the young are already fledged and have started to fly out of the area and more are expected to do so by as early as next week," Dr Craik said.

"We are delighted that so many have successfully reproduced, despite low water levels, cooler overnight temperatures, increased predation and decreasing food supplies.

"Unfortunately, some chicks have been abandoned by their parents, but that still leaves us with a huge, historically successful breeding event – the first since 1999."

Dr Craik says there are also increased numbers of swans, great egrets, and pelicans, along with tens of thousands of ducks of various species have arrived since the last aerial survey in March.

"An added bonus is that great cormorants have started breeding," she said.

Dr Craik said the watering was also contributing to the health of plant species, invertebrates, frogs and fish and was likely to continue to benefit these organisms and the other bird species for some time.

She said inflows would continue until early May and with reduced losses over the cooler months the lakes would provide a valuable waterbird refuge through to summer next year.

Likewise, wetlands on the Warrego and Paroo would hold water for 12 months or more.