The shutters of the Idukki dam will open on Tuesday.
The state’s largest reservoir, which accounts for more than 93 per cent of its live storage capacity, is rapidly filling up after heavy rain.
The decision was taken after three days of heavy rain was forecast., beginning Wednesday.
Chief Minister Pinarayi Vijayan has issued warnings and the government will shift people to safer locations once the dams has opened.
Already, 64 families which would be immediately affected by the dam opening have been evacuated.
Water Resources Minister Roshi Augustine said two shutters of the dam would be opened by 50 cm. “We can ease the anxiety of the people by keeping the water level down. The water level at the dam would be maintained between 2395 and 2396 ft as against the full storage level of 2403 ft. At present the water level is at 2397.56 ft.”