The National Water Supply and Drainage Board (NWSDB) will suspend the water supply to a large stretch of Colombo and its southern suburbs for 24 hours from Thursday night, for maintenance work at the Ambatale Water Treatment Plant.

Supply will be cut from 8.00 p.m. on Thursday, September 3 until 8.00 p.m. on Friday, September 4, both outlets reported.

Areas affected

The board listed two groups of affected areas. The first covers the southern coastal and suburban belt: Nugegoda, Kohuwala, Dehiwala, Mount Lavinia, Ratmalana, Moratuwa, Rawathawatta, Soysapura, Angulana, Indibedda, Katubedda, Kaldemulla, Modara, Koralawella, Egoda Uyana and Katukurunda.

The second covers areas closer to the city and the eastern suburbs: Sethsiripaya, Himbutana, Udumulla Road, Maligagodella, Bank Junction Road, W. A. Silva Mawatha, Havelock Road, Kalyani Road, Colombo 06, Hospital Roundabout Road, Jayanthi Mawatha and Shanthi Mawatha.

The NWSDB said the work is being carried out to improve the quality and reliability of the supply. It apologised for the disruption and asked consumers in the affected areas to store water in advance and use it sparingly during the interruption.

Two spellings of the same places

The two newsrooms differ slightly on two localities. Ada Derana lists Mutwal and Indibedda, while NewsFirst lists Modara and Indibeddiya. Modara and Mutwal are two names for the same Colombo 15 area; the remaining difference is one of transliteration. The lists are otherwise identical.

Context

This is planned maintenance, and is a separate matter from the unplanned shutdown of the Ambatale and Kelani South plants on 25 August, which was ordered over a water quality alert on the Kelani River and lifted the same day once tests cleared the intakes.

Ambatale is the main treatment plant supplying Colombo and draws from the Kelani River. Work there affects a wide area at once, which is why the board’s list runs from Modara in the north to Katukurunda, south of Moratuwa.

Update, September 3: the work is on the Ambatale–Dehiwala transmission pipeline

Hiru News named the asset being worked on, which neither outlet had done the previous day. The interruption is for essential maintenance on the Ambatale–Dehiwala water transmission pipeline near Diyatha Uyana in Battaramulla, close to the Polduwa Bridge, Hiru reported, citing the board.

That explains the otherwise puzzling shape of the affected area. The outage is not a treatment-plant shutdown at Ambatale but a break in the single trunk main that carries treated water from Ambatale south-west to Dehiwala — which is why the list runs down the southern coastal belt to Katukurunda while sparing most of the intervening city, and why Battaramulla-area roads around Sethsiripaya appear on it.

Hiru confirmed the timing as 8.00 p.m. today (3) to 8.00 p.m. tomorrow (4) and listed the same two groups of areas. It uses Modara and Indibedda, matching NewsFirst on the first and Ada Derana on the second.

Update, September 4: the cut is extended to 11.30 p.m.

The interruption has overrun. The NWSDB said supply to the affected areas will now stay off until 11.30 p.m. on Friday, September 4 — three and a half hours beyond the 8 p.m. restoration time it had announced, and a total interruption of about 27 and a half hours rather than 24.

The board “expressed regret over the inconvenience caused to consumers due to the extension of the water cut” and again asked the public to use water sparingly, Ada Derana reported. Daily Mirror said consumers should make arrangements in advance and gave the board’s 24-hour hotline, 1939, for further information.

Both outlets listed the same affected areas as before, in the same two groups. Neither reported any area being added or dropped.

The two outlets still differ on what is being worked on

Ada Derana attributes the interruption to “essential maintenance work at the Ambatale Water Treatment Plant”, the framing it used on September 2. Daily Mirror attributes it to maintenance on the Ambatale–Dehiwala water transmission pipeline near Diyatha Uyana in Battaramulla — which matches the account Hiru News gave on September 3, and which better fits the shape of the affected area.

The distinction matters for anyone off the list: a plant shutdown would be expected to affect a wider area than a single trunk main. Two of the three outlets now describe it as pipeline work.

Ada Derana’s own area list has also shifted by one name. Where its September 2 report listed Kaldemulla, Friday’s report lists Kaludewella. The rest of the list is unchanged, and no outlet flagged the difference.

What has not been reported

The extension itself was announced without a cause: no outlet has said what overran, whether the work was more extensive than expected or whether a fault was found once the main was opened. None has said whether supply will be restored in stages after 11.30 p.m. or all at once, or whether a further extension is possible.

Nor has any outlet reported whether bowser distribution was arranged for hospitals and other essential users during the interruption, whether pressure was reduced in adjoining areas that are not on the list, or whether this is preventive work or a repair. The board has not said when it expects pressure to return to normal across the full area.

Sources