A big cloud seeding trial is being credited for a positive turn-around in lake levels in the New South Wales Snowy Mountains.

For the first time in five years, water storages are rising after droughts that had seen lake levels fall to their lowest since the opening of the Hydro Electric Scheme in the 1950s.

Snowy Hydro spokesman Paul Johnson said that the expanded cloud seeding program is paying off. "Preliminary data indicates that you could be seeing up to about a 10 per cent increase in snow over a 10 year period on average," he said. But Snowy Hydro warns that it is going to take at least 10 years of above average inflows to restore the dams to capacity.