Engineers opened two spill gates each at the Upper Kotmale and Deduru Oya reservoirs on Wednesday as heavy rain fell over their catchment areas.
At Deduru Oya Reservoir, the two gates were opened by two feet each, releasing water into the Deduru Oya at a rate of 4,200 cubic feet per second, the Director of Irrigation (Water Management) said. Residents living along the Deduru Oya downstream of the reservoir were urged to remain vigilant and to monitor water levels in the river.
At Upper Kotmale Reservoir, engineers said the gates were opened because of continuous rainfall in the catchment. They said the remaining spill gates would open automatically if heavy rain continued in the area, and advised residents on both banks of the Kothmale Oya downstream of the dam to stay alert.
Train services on the line beyond Rambukkana were also disrupted on Wednesday after a landslide at Kadigamuwa Railway Station, according to reports. Services to Gampola and Peradeniya were affected. No time for the line to reopen was given in the information available.
The Department of Meteorology said in its forecast issued at 4 p.m. on Wednesday that a low-level atmospheric disturbance near the island had developed into a low-pressure area. The system is expected to bring enhanced rainfall to the island and the surrounding deep and shallow sea areas on 21 and 22 October.
Rainfall exceeding 100 mm is likely in some areas of the Western, Sabaragamuwa and North Western provinces, the department said. Showers or thundershowers are expected at times in the Western, Sabaragamuwa, Central, Southern and North Western provinces and in the Mannar district. Elsewhere, showers or thundershowers are expected after 1 p.m.
The department warned of temporary strong winds and lightning during thundershowers and urged the public to take precautions to limit possible damage. Misty conditions are expected in some areas of the Central and Uva provinces during the early morning. Naval and fishing communities were advised to follow later forecasts and official bulletins as the system develops.
Background
Spill gates are opened when a reservoir fills close to its capacity. Releasing water in a controlled way lowers the level behind the dam, which protects the structure. It also means river levels downstream rise, which is why irrigation officials and engineers issue warnings to communities along the banks.
The Deduru Oya flows through the North Western Province, while the Kothmale Oya drains the central hills. The Department of Meteorology treats October and November as the second inter-monsoon period, when thundershowers in the afternoon and evening are common, before the north-east monsoon season begins later in the year.
What it means
People living beside the Deduru Oya and the Kothmale Oya below the two dams have been asked to watch water levels, as releases may continue or increase if rain persists. Anyone travelling by rail towards Gampola and Peradeniya may wish to check service updates with the railway before setting out.
In areas where more than 100 mm of rain is forecast, heavy falls over a short period can bring flooding of low-lying land and landslides on slopes. The department has advised the public to take precautions during thunderstorms and to follow its official bulletins for any change in the forecast.
