The ESB says levels in Lough Derg are finally going down after weeks of swelling.
The drop means it is able to reduce the flow of water through the Parteen Weir.
The rate will be cut to 335 cubic metres per second today - down from its peak of almost 500 over Christmas.
However the change does not remove the risk of flooding for areas downstream including Springfield, Montpelier, Castleconnell, Mountshannon (Annacotty) and the University of Limerick.
European direction
Meanwhile, the European Commission is clarifying EU regulations on flooding.
A cross-party delegation of MEPs is asking the European Commission whether or not rivers like the Shannon can be dredged, in a bid to prevent future flooding disasters.
Hundreds of homes and businesses have been flooded across Ireland in winter storms and many roads are still impassable due to high water levels.