The dam reached capacity on Friday afternoon and releases amped up to a rate of 40GL, Tony Webber from Water NSW said on Monday.

He said inflows reached a rate of 109GL a day on Saturday with rains in the catchment; this doesn't mean 109GL flowed in in the day, that's what would flow in if the water continued at that rate for a full 24 hours.

With the Water NSW website showing the dam at 104.9 per cent through the weekend, releases spilled from the dam at a rate of 80GL a day, Mr Webber said.

They were scaled back to a rate of 50GL per day from midnight Sunday with inflows coming down to 30GL per day.

That water is combining with water from the Belubula River and other tributaries and it's anticipated they will cause major flooding at Forbes mid this week.

Water NSW is working with the Bureau of Meteorology and regional airspace reference panels to manage inflows into dams across several key areas of regional NSW, with more rain forecast for the week ahead.

With dam storage levels high, most catchments saturated and wetter than average weather conditions forecast by the Bureau for the near future, WaterNSW is monitoring rain forecasts and making releases to increase storage capacity to capture inflows as required.

Wyangala Dam remained at 103.5 per cent on Monday.