The National Water Supply and Drainage Board (NWSDB) has temporarily suspended the water supply to several areas of the Colombo and Gampaha districts after an urgent problem with water quality was detected near the Kelani River intake point.

Production has been halted at both the Ambatale and Kelani South water treatment plants, Ada Derana reported early on Tuesday. The Board said the suspension followed a notification it received from the Disaster Management Centre (DMC).

The NWSDB said further updates would be issued on when supply would be restored, and apologised to consumers for the disruption.

Why the DMC route matters

The two plants named are central to the capital’s supply. Ambatale is the largest treatment facility serving Colombo and its suburbs, drawing raw water directly from the Kelani River; Kelani South serves areas on the southern bank. A shutdown of both at once removes a substantial share of the metropolitan supply rather than a single distribution zone.

The involvement of the Disaster Management Centre is the notable detail. Routine interruptions — main breaks, scheduled maintenance, pump failures — are announced by the Water Board alone, as when a burst Ambatale–Kolonnawa main cut supply to Colombo suburbs in June. A DMC notification points instead to an external event affecting the river itself.

What has not been said

Ada Derana’s report did not specify which areas are affected, what the water quality problem is or what caused it, or how long the suspension is expected to last. The NWSDB has not published a restoration estimate.

The suspension comes as the Kelani basin runs through a prolonged dry spell, with river flows down across the island and reservoir storage at about 36%. Lower flows in the lower Kelani raise the risk of salinity intrusion at the intake, though no outlet has linked Tuesday’s suspension to that.

Update: risk resolved, supply returning — August 25

The threat to water quality at the Kelani River intakes has been cleared and supply is being restored, the NWSDB said later on Tuesday morning.

The Board said the risk around the right bank and Ambatale intakes was resolved with the assistance of the Tri-Forces. Laboratory tests were then run to check the water against the standards required for resumption, following recommendations issued by the Disaster Management Centre. Those tests confirmed the water meets the required quality standards, and distribution has resumed.

Supply to areas near the treatment plants was expected back to normal within a few hours. Full restoration will take longer in some suburbs, though the outlets gave slightly different lists: Ada Derana named Battaramulla, Kotte, Pamankada and Nugegoda, while the Daily Mirror named Battaramulla, Kotte, Nawala and Nugegoda.

NewsFirst, filing at 6.59 a.m., breaks that tie in Ada Derana’s favour: it lists Battaramulla, Sri Jayawardenepura Kotte, Pamankada and Nugegoda. Two of the three outlets therefore have Pamankada, and the Daily Mirror’s “Nawala” stands alone. NewsFirst independently confirmed both the Tri-Forces role and that the suspension followed a sudden deterioration in water quality at the Kelani River intake. Hiru News also reported the restoration, without naming affected areas.

The NWSDB asked for public cooperation with the measures taken to protect consumer health, and gave its 24-hour toll-free hotline, 1939, for further information.

Neither the Board nor either newsroom has said what the contamination risk actually was, what caused it, or what role the Tri-Forces played in resolving it. The original suspension notice also went out without that detail, so the cause of a shutdown at the capital’s two main treatment plants remains unexplained.

Update: the cause, later on August 25

The NWSDB later confirmed that the shutdown followed the release of a chemical into the environment by private industrial premises at Heiyanthuduwa, upstream of the intakes, and said it has lodged a police complaint. Residents had traced blue-tinted water through a paddy field to a container yard drain feeding the Kottunna Oya. See the full account of the leak and the investigation.

Sources