The Irrigation Department has issued minor flood warnings for low-lying areas along the Kalu Ganga and the Mahaweli River and opened the spill gates of several reservoirs after heavy rainfall.
The Mahaweli warning covers low-lying areas in the Pasbage Korale Divisional Secretariat Division, where significant rain fell in the river’s upper catchment over a few hours. It was issued at 11.30 a.m. on Monday and remains valid until 11.30 a.m. on Tuesday.
The Kalu Ganga warning covers the Ratnapura and Kalutara districts and is based on rainfall and water levels at the department’s river gauging stations. It is valid until 11.30 a.m. on Tuesday. In Ratnapura District, the areas at risk are Pelmadulla, Nivithigala, Ratnapura, Kuruwita, Ayagama and Elapatha. In Kalutara District, they are Ingiriya, Horana, Dodangoda, Millaniya, Bulathsinhala, Madurawala and Palindanuwara.
The department advised residents and motorists in those areas to remain vigilant and asked disaster management authorities to take precautions.
At Deduru Oya Reservoir, eight spill gates were opened by two feet each, releasing 10,400 cubic feet of water per second. At Rajanganaya Reservoir, discharge into Kala Oya was above 3,800 cubic feet per second and was expected to reach 8,000 by 9.00 a.m. on Monday.
One spill gate at Kukule Ganga Reservoir was opened, releasing 45 cubic metres per second. A further 48 cubic metres per second is discharged during power generation, bringing the total flow into Kuda Ganga to 93 cubic metres per second.
Two emergency spill gates at Kala Wewa were opened by six inches each, releasing 511 cubic feet per second. The reservoir is receiving about 5,500 cubic feet per second through Dambulu Oya, and its storage has risen to 83,782 acre-feet. Two gates at Thabbowa Reservoir were opened by half a foot each. At Inginimitiya Reservoir in the Mee Oya basin, water was expected to be released at 1,000 cubic feet per second by 1.00 p.m. on Monday.
The department said the gate openings and releases could change depending on rainfall in the catchment areas. It asked people living along Deduru Oya, Kala Oya, Mee Oya and other downstream areas to watch water levels and follow official instructions.
Background
The Irrigation Department monitors rainfall and river levels through gauging stations on the main river basins and issues flood warnings to the public and to disaster management authorities. A minor flood warning refers to flooding in low-lying land near the river, not wide inundation of settled areas.
Spill gates are opened when inflow raises the water in a reservoir towards its safe limit. Releasing water in a controlled way protects the dam, but it raises river levels downstream for a time, which is why the department notifies residents along the rivers each time.
What it means
People living near the rivers named in the warnings should expect water levels to change during the day, and the department has asked them to follow its announcements and disaster management instructions.
Motorists on roads that cross low-lying land near the Mahaweli and Kalu Ganga were advised to take care. Sri Lankans abroad with family in the Ratnapura, Kalutara and downstream districts may wish to check with them, as the warnings remain in force until Tuesday morning.
