Update, 3 November — the release has doubled to eight gates. See the update section below.
Four spill gates at the Deduru Oya Reservoir have been opened by one foot each after heavy rainfall pushed water levels up, and the Irrigation Department has warned residents living along the riverbanks downstream to stay alert.
Water is being discharged into the Deduru Oya at 2,800 cubic feet per second as a result, the Daily Mirror reported on Monday evening.
The department said levels downstream may fluctuate while the gates are open, and asked people in the affected areas to follow the periodic announcements it issues alongside disaster management authorities as the release continues. The public has been advised to take precautions in response to any change in water levels.
Where this sits in the current wet spell
The opening is the latest in a sequence of reservoir releases through a prolonged period of heavy rain. This desk reported on spill gates opening at Polgolla, Victoria and Thabbowa on 26 October, when Kala Wewa stood at 103 per cent of capacity and Thabbowa and Inginimitiya were together releasing 7,400 cusecs into the Mee Oya.
The rain has not stopped since. The Met Department raised its rainfall warning on Monday to above 75 mm at some places across six provinces — the North-Western among them — as Cyclone Murasu intensified in the Bay of Bengal on a track towards the Andhra Pradesh coast rather than Sri Lanka.
The Disaster Management Centre’s running count of damage from the late-October storm period and the unsettled weather around it stands at six dead, three missing and 745 damaged houses between 23 October and 1 November. Those figures predate Monday’s release and do not include it.
Update — 3 November: river overflows, Northern Line suspended
A day after the gates were opened, the Deduru Oya overflowed downstream far enough to halt rail traffic. The Railway Control Room suspended Northern Line train services between Wellawa and Ganewatta on Tuesday morning and sent technical officers to inspect the track, according to NewsFirst and Hiru News.
Neither filing on the rail suspension states whether Monday’s discharge caused the overflow, and the link should not be assumed without that confirmation — but the affected stretch lies in the downstream reach the Irrigation Department’s warning covered. The Met Department’s Tuesday forecast again carries falls above 75 mm at some places.
A caution on identifying this event
Spill-gate openings at Deduru Oya are a recurring headline, and several distinct releases have been reported at this reservoir within the past few weeks alone, with different gate counts and discharge rates each time. The event described here is specifically the Monday 2 November release: four gates, one foot each, 2,800 cubic feet per second. Earlier reports describing two gates, or six gates at four feet, are separate openings and not this one.
Not reported
The filing does not give the reservoir’s current storage level or percentage of capacity, name the downstream divisional secretariats or villages most at risk, say how long the gates are expected to remain open, or state whether any evacuation or flood warning has been issued for the lower Deduru Oya basin. No second verified newsroom had carried this specific release at the time of writing, and Ada Derana — which has covered earlier openings — remained unreachable from this desk.
Update — 3 November, 8.04am Colombo: eight gates now open
The Irrigation Department has opened eight spill gates at the Deduru Oya Reservoir, Hiru News reported on Tuesday morning — double the number reported on Monday evening. The department has again told people living downstream of the reservoir to remain alert.
The filing is two sentences long. It does not give the gate aperture or the discharge rate, so the 2,800 cubic feet per second figure above belongs to Monday’s four-gate release and should not be carried forward to Tuesday’s. It gives no storage level or percentage of capacity, and names no divisional secretariat.
The caution in the section above applies directly to this update: gate counts at Deduru Oya change from filing to filing, and a count alone does not identify a release. Tuesday’s event is eight gates, 8.04am Colombo, 3 November.
Downstream, the consequences had already appeared. The river burst its banks between Wellawa and Ganewatta overnight and Northern Line train services were suspended from 6.09am; the line reopened at 9.17am, about an hour after the eighth gate was opened.
Update — 3 November, 11.47am Colombo: the apertures and the discharge rate
The Daily Mirror has now filed on the eight-gate release and supplies the two figures missing from the update above. Two gates are open by two feet each and six by three feet each, and water is being released into the Deduru Oya at a rate exceeding 15,300 cubic feet per second, the Irrigation Department said, according to the Daily Mirror.
That confirms the eight-gate count from a second verified newsroom, and puts Tuesday’s discharge at more than five times Monday’s 2,800 cusecs — the comparison the Hiru filing could not support.
The Director of Irrigation (Water Management) urged residents on both banks downstream of the reservoir to stay alert to changes in water level, and to follow announcements from the Irrigation Department and the disaster management authorities on the operation of the spill gates.
Still not given: the reservoir’s storage level or percentage of capacity, how long the gates will remain open, the divisional secretariats most at risk, and whether any evacuation order has been issued.
Update — 3 November, 8.36pm Colombo: Hiru confirms the apertures, release unchanged
Hiru News has re-filed the eight-gate story under a new article ID, and its text now carries the detail its morning filing lacked: six gates open by three feet each and two by two feet each, discharging 15,300 cubic feet per second, attributed to the irrigation engineer in charge of the reservoir. Residents on both banks downstream are again told to stay alert.
Those figures match the Daily Mirror’s 11.47am filing exactly, so the Irrigation Department’s release appears unchanged across the day rather than escalating further. The aperture breakdown is now carried by two verified newsrooms.
Note for future reference: this is the same event as the morning filing, not a third opening — Hiru published it twice under two IDs with the same headline and slug. Gate counts at Deduru Oya change between genuine releases, and a repeated count across two filings hours apart is a re-file, not an escalation.
