The Department of Irrigation says river water levels are gradually receding following reduced rainfall.
Director L.S. Sooriyabandara said a minor flood situation continues along the Kalu River, based on Millakanda gauge data.
Water levels in Attanagalu Oya are also declining, but residents in Gampaha, Katana and Wattala have been advised to remain alert.
Rainfall continues in the Hanwella area along the Kelani River, with further showers forecast.
As of May 15, 22 major reservoirs and 19 medium tanks were spilling, authorities said.