The Irrigation Department issued a minor flood alert on Thursday evening for low-lying ground along the Nilwala River in six divisional secretariat divisions, after heavy rain in the river’s upper and middle catchments — and one gauge on the river had already crossed minor flood level by the afternoon.
The six divisions at risk over the following 24 hours are Akuressa, Athuraliya, Malimbada, Kamburupitiya, Thihagoda and Matara, the Daily Mirror reported at 6.40 p.m. The department said it issued the warning on prevailing rainfall and an analysis of water levels at its own gauging stations in the basin, and asked residents and motorists in those areas to take extreme care. Disaster management authorities have been asked to take precautionary measures.
The warning has moved downstream since September
The Nilwala was last under a minor flood warning on 24 September, and the list of divisions is not the same one.
| September 24 | October 15 | |
|---|---|---|
| Divisions | 8 | 6 |
| Upper basin | Pasgoda, Kotapola, Pitabeddara | — |
| Middle basin | Akuressa, Athuraliya, Malimbada, Kamburupitiya, Tihagoda | Akuressa, Athuraliya, Malimbada, Kamburupitiya, Thihagoda |
| River mouth | — | Matara |
Three interior divisions have dropped off the list and Matara, at the river mouth, has been added — a division that was not warned in September. The five middle-basin divisions are unchanged. Neither filing comments on the shift, and the department does not explain it; it is recorded here as a difference between two warnings three weeks apart, not as an interpretation of the river’s behaviour. (Hiru rendered the fifth division Tihagoda in September and the Daily Mirror renders it Thihagoda now — the same place.)
One gauge is already over
NewsFirst, reporting the Irrigation Department separately, says the Nilwala at Thalgahagoda has already reached minor flood level, and that three further points are at warning level: the Nilwala at Panadugama, the Kuda Ganga at Millakanda and the Attanagalu Oya at Dunamale.
Thalgahagoda and Millakanda are the same two gauges that were over in the last week of September, when the Nilwala and Gin warnings ran for four days.
El Niño is back in the stated reason
The more significant line in Thursday’s filing is about the next two months rather than the next 24 hours. The Department of Meteorology warned that flood risk could increase in the coming months as rainfall continues and El Niño strengthens to unusually high levels, saying the developing conditions could significantly influence rainfall patterns over the next two months.
That closes a gap this desk flagged three weeks ago. When the department told authorities on 26 September to prepare for possible floods in October and November, those filings did not mention El Niño at all, and it was not stated whether the assessment updated or repeated an earlier, El Niño-based outlook from late August. Thursday’s advisory puts El Niño back in the department’s own reasoning, and it also supplies the other thing September’s warning lacked — named river basins, which that filing did not identify.
The trajectory is consistent with the department’s own forecasting. Director General of Meteorology Ajith Wijemannage put the probability of the current event escalating into a strong El Niño at 98% within three months on 11 September. He is the official quoted again now, saying unsettled weather should persist through the month, with sunny mornings giving way to afternoon and evening thundershowers under the Second Inter-Monsoon.
Thursday’s numbers
- Highest 24-hour rainfall: 127.3 mm at Kekirawa
- Level Two landslide warnings: Maturata, Walapane, Hanguranketha and Nildandahinna (Nuwara Eliya); Balangoda and Kolonna (Ratnapura)
- Level One landslide warnings: parts of Hambantota, Kalutara, Kandy, Kegalle, Matale, Matara and Ratnapura
- At sea: thundershowers from Negombo to Colombo to Galle, winds to 60–70 kmph in squalls
The two NewsFirst filings give different rainfall thresholds a few minutes apart. The 4.57 p.m. forecast puts heavy falls above 100 mm at some places in the Western and Sabaragamuwa provinces and the Matara, Galle and Puttalam districts; the 5.18 p.m. advisory says some areas could receive above 75 mm. Both name the same areas for showers — Western and Sabaragamuwa provinces and the Matara, Galle, Puttalam, Mannar and Jaffna districts.
The separate lightning advisory running until 1 a.m. Friday is covered in this desk’s report on Thursday’s advisory and the Colombo flooding. Worth noting against it: the Southern Province was the one province left out of that lightning advisory altogether — and it is where the river flood alert has now been issued.
Not reported
Neither filing gives an expiry time for the Nilwala alert beyond “the next 24 hours”, and neither reports any evacuation, displacement, road closure or damage in the six divisions. No reading is given for how far above minor flood level Thalgahagoda stands, and no filing says whether the warning is expected to be extended as the September one was.
The department does not define “unusually high levels” for El Niño, give a current index value, or say whether this supersedes the 98% figure from September. Neither filing names the agency that would lead flood preparations, and neither reports whether the National Building Research Organisation has issued any red evacuation warning.
Sources: Daily Mirror, NewsFirst weather warning and rain forecast.
