The Department of Meteorology has issued a severe lightning advisory covering most of the island, and two spill gates at the Deduru Oya reservoir have been opened as heavy rain continues.

The lightning warning

The Met Department said there was a high probability of severe lightning with thundershowers during the evening or night in the Western, Sabaragamuwa, Central, Uva, North Western, Northern, North Central and Southern provinces, Hiru News reported.

Rainfall above 100 millimetres was forecast at some places in the Western, Sabaragamuwa, Central, Uva, North Western and Southern provinces, and in the Anuradhapura district.

NewsFirst reported the same rainfall forecast and added that showers or thundershowers were expected over most of the island after 1:00 p.m. The public was advised to take precautions against the temporary strong winds and lightning that accompany thundershowers.

116mm at Kirindiwela

The heaviest fall in the 24 hours ending at 8.30 a.m. on Thursday was 116 millimetres, recorded at Kirindiwela in the Gampaha district, according to Hiru.

Deduru Oya releasing 1,400 cubic feet a second

The Department of Irrigation opened two spill gates at the Deduru Oya reservoir by one foot each, releasing water at 1,400 cubic feet per second, NewsFirst reported. Residents in low-lying areas along the Deduru Oya were told to remain alert.

Deduru Oya drains into the North Western dry zone, where the Met Department’s own forecast placed some of the heaviest expected falls.

Update, 10 October: four gates now open, releasing three times as much water

The release from Deduru Oya has escalated. Four radial gates are now open and discharging 4,200 cubic feet per second — triple Thursday’s rate — with the reservoir within seven centimetres of its full supply level, the Daily Mirror reported early on Saturday.

Two of the four gates have been raised by 24 inches and the other two by 12 inches. Thursday’s configuration was two gates at one foot each, releasing 1,400 cusecs.

The storage figures this report lacked. As of 7.00 p.m. on Friday 9 October, the reservoir stood at 70.72 metres above mean sea level against a full supply level of 70.79 metres — effectively full, with 7cm of freeboard. Its water capacity at that time was given as 59,651 acre-feet by Irrigation Director (Water Management) Engineer H.M.P.S.D. Hearth, the first named Irrigation Department official to appear in this thread.

The escalation is consistent with a reservoir that continued to fill after Thursday’s rain: the gate openings widened as the margin below full supply narrowed, which is what the structure’s gates exist to manage.

Context

Sri Lanka records a high number of lightning deaths each year, and the Met Department’s severe-lightning advisories are issued to prompt people to move indoors and away from open ground, isolated trees and water during storms.

This advisory concerns public safety. Separately on Thursday, the Mahaweli Authority asked farmers to rely on rainwater for Maha season land preparation and the Irrigation Department reported five other reservoirs spilling — an irrigation-management matter covered in that report.

Not reported: neither filing says how long the advisory runs, gives a colour-coded warning level, or names the districts within each province expected to see the heaviest rain. Neither reports any casualties, displacement or damage, says whether schools or transport are affected, or gives the current storage level at Deduru Oya or how long the gates will stay open. Neither carries a Disaster Management Centre statement.

Update to the above, 10 October: the storage level is now reported — 70.72m MSL against a 70.79m full supply level, and 59,651 acre-feet, as of 7.00 p.m. on 9 October. Still unreported: how long the gates will stay open, whether the release has caused any flooding downstream, whether any advisory has been issued to residents along the Deduru Oya beyond Thursday’s call to remain alert, and whether the Disaster Management Centre has said anything at any point. Saturday’s filing carries no rainfall figures and no renewed Met Department warning, so it does not establish whether the rain that filled the reservoir is continuing.

Saturday’s escalation is reported by the Daily Mirror alone. This desk searched Hiru News, NewsFirst, Ada Derana, EconomyNext and the Island for a filing on the four-gate release and found none — those searches returned only earlier editions of this recurring story, including Ada Derana’s own report of Thursday’s two-gate opening.

Update, 10 October afternoon: the release eases, and the island-wide picture

By 1 p.m. on Saturday the Deduru Oya release had been scaled back — two gates at 24 inches discharging 2,800 cubic feet per second, down from the four gates and 4,200 cusecs reported that morning, according to the Irrigation Department’s latest reservoir status report, carried by the Daily Mirror.

That is the first de-escalation in this thread. The sequence at Deduru Oya now runs: two gates at one foot and 1,400 cusecs on Thursday, four gates and 4,200 cusecs early Saturday, two gates at 24 inches and 2,800 cusecs by Saturday afternoon — a peak-and-ease pattern consistent with the inflow having passed rather than the reservoir still filling.

Eight reservoirs spilling

Deduru Oya is one of eight reservoirs under the Irrigation Department spilling or releasing water as of 1 p.m., with gates open at three major tanks. The six major reservoirs listed are Ambewela Tank and Kande Ela Tank in Badulla, Yan Oya and Rajangana in Anuradhapura, Deduru Oya in Kurunegala and Wan Ela in Trincomalee. Two medium-sized reservoirs — Bomuruella in Badulla and Denagama Wewa in Galle — were also spilling.

The largest release is not Deduru Oya’s. Rajangana is discharging 5,365 cusecs through six gates — two open by five feet, two by four feet and two by two feet. Yan Oya is releasing just 68 cusecs through three gates at half a foot, and Wan Ela is spilling at one foot for a discharge of 10 cusecs.

The spread of locations is worth noting: Badulla and Nuwara Eliya in the hill country, Anuradhapura and Trincomalee in the dry zone, Kurunegala in the north-west and Galle in the south. This is no longer a North Western event.

The department repeated the downstream warning, urging people living below spilling or releasing reservoirs to watch for changes in river levels and to follow instructions from the Irrigation Department and local authorities.

Storage still only a third full

The figure that puts the spilling in perspective: the effective water storage of the department’s 74 major reservoirs stood at 35.3 per cent of total capacity. Eight reservoirs spilling is therefore a story about where the rain fell, not about a system near capacity.

The district figures bear that out. Nuwara Eliya was at 99.3 per cent and Kurunegala at 82 per cent — the catchments doing the spilling — while Hambantota stood at 54.6 per cent.

One figure in the report is internally inconsistent. Monaragala appears twice, at 85 per cent and at 28.5 per cent, in two separate entries. The filing does not reconcile them or say what distinguishes the two entries, and we have not resolved which applies to what; the discrepancy is reported here rather than one figure being chosen.

The report was issued by Irrigation Director (Water Management) Engineer H.M.P.S.D. Herath — the same official named in Saturday morning’s filing, where the Daily Mirror rendered the surname Hearth. This is a spelling variant across two filings by the same paper, not two officials.

What this closes and what it does not

This answers one item flagged above: the release has now been reported as easing, and a reservoir-by-reservoir picture exists. It does not report any flooding downstream, any Disaster Management Centre statement, any rainfall figures, or how long the remaining gates will stay open — so those gaps stay open. Nor does it say whether the Met Department’s lightning advisory is still in force.

Update, 11 October: the ease continues and Rajangana’s release collapses

Sunday’s Irrigation Department status report shows the event continuing to wind down. Seven reservoirs are now spilling or releasing — five major and two medium — against eight the previous day, the Daily Mirror reported from a water management report issued at 12.30 p.m.

Spill gates are open at Yan Oya and Rajangana in Anuradhapura and Deduru Oya in Kurunegala. Kande Ela and Wan Ela are spilling, as are the medium-sized Bomuruella in Badulla and Denagama Wewa in Galle.

The sharpest change is at Rajangana. Its discharge has fallen from 5,365 cusecs on Saturday to 502 cusecs — a drop of more than 90 per cent, and the single clearest sign the inflow has passed. Deduru Oya is now the largest release at 2,800 cusecs, unchanged from Saturday afternoon, and Yan Oya is at 67.7 cusecs, effectively flat against Saturday’s 68.

Ambewela Tank, listed as spilling on Saturday, no longer appears. That accounts for the drop from eight to seven.

The four-stage sequence at Deduru Oya now reads: 1,400 cusecs on Thursday, 4,200 early Saturday, 2,800 on Saturday afternoon, and 2,800 on Sunday — a peak, a fall, and then a plateau.

The department repeated its downstream warning in the same terms.

Two discrepancies in Sunday’s filing

The district storage figures contradict themselves. The report states that “Matale recorded the highest effective storage level at 86.1 per cent, followed by Nuwara Eliya at 99.3 per cent, Kurunegala at 82 per cent and Matara at 77.9 per cent.” Nuwara Eliya’s 99.3 per cent is higher than Matale’s 86.1, so the two cannot both be as described. Nuwara Eliya was also the highest district on Saturday’s report, at the same 99.3 per cent. We report the figures as given rather than choosing which is wrong.

Kande Ela has changed district. Saturday’s filing placed it in Badulla; Sunday’s places it in Nuwara Eliya. This is the same paper on consecutive days, in the same recurring report. Kande Ela is a reservoir in the Nuwara Eliya area, so Sunday’s attribution is the more plausible of the two, but neither filing acknowledges the change.

Storage barely moved

The headline storage figure is 35 per cent of total capacity across the department’s 74 major reservoirs, against 35.3 per cent on Saturday. Despite a week of spilling, the national system is no fuller — which again places this as a story about where rain fell rather than one about reservoirs nearing capacity.

Still open

Sunday’s report closes nothing that was previously flagged. There is still no flooding report, no Disaster Management Centre statement, no rainfall figure, no indication of how long the remaining gates will stay open, and no word on whether the Met Department’s lightning advisory remains in force.