The Department of Irrigation has warned that the water level of the Deduru Oya is nearing spill level due to heavy rainfall in the upper and middle regions of the Deduru Oya basin.
As a result, the sluice gates of the Deduru Oya Reservoir have been opened, and water is currently being released into the Deduru Oya at a rate of 16,500 cubic feet per second, the department said.
It added that the volume of water released may need to be increased further depending on the amount of water flowing into the reservoir.
Under the prevailing conditions, there is a risk of flooding in low-lying areas and downstream sections of the river valley within the Deduru Oya basin.
Accordingly, residents of the Wariyapola, Nikaweratiya, Mahawa, Kobeigane, Bingiriya, Pallama, Chilaw, Arachchikattuwa and Rasnayakapura Divisional Secretariat divisions have been warned to remain vigilant.
Residents of the affected areas and motorists have been urged to exercise extreme caution.
Disaster management authorities have also been requested to take the necessary precautionary and safety measures in preparation for possible flooding.