Reservoir sedimentation is adversely impacting the storage capacity of dams in Kerala besides increasing manifold the possibility of floods downstream, experts said.
The previous State budget had recommended the desilting of reservoirs to increase their capacity. A status check of the dams in Kerala.
Thiruvananthapuram district
Aruvikkara Dam: Thiruvananthapuram city gets its drinking water from Aruvikkara Dam with a stated original capacity of two million cubic metres. Accumulated sand and silt have reduced the dam's storage capacity by half, and sandbeds could be seen at several parts of the reservoir.
The dam could store enough water only for four days now. A report by the Kerala Water Authority said desilting the reservoir could increase the capacity to hold water enough for eight to nine days.
Though Rs 4 crore was allotted to desilt the reservoir in 2017, the work was stalled citing the expense would overshoot the allocation.
Neyyar Dam: An inspection conducted in 2016 found five metres of silt on the reservoir bed.
Kollam district
Thenmala-Parappar Dam: Sedimentation has reduced the original capacity of 524.3 million cubic metres to 498 million cubic metres. A study by the Kerala Engineering Research Institute, Peechi, in 2018 found the silting has reduced the dam's storage capacity by five per cent.
The damaged generator at the Kallada powerhouse, too, has been contributing to the rapid increase in water level. The powerhouse has been functioning with only one generator for several years.
Pathanamthitta district
The district has four major and six minor dams. None of them have been desilted.
Ernakulam district
Idamalayar Dam: The storage capacity has not been affected since the reservoir is situated in the forest area.
Thrissur district
Chimmony Dam: The reservoir has not been desilted. Original capacity: 151.55 million cubic metres. Current storage capacity: 150.42 million cubic metres (according to a 2019 study).
Vazhani Dam: The original storage capacity of 18.12 million cubic metres has been reduced. An accurate figure, however, is not available.
Peringalkuthu Dam: Capacity: 32 million cubic metres. According to 2019 statistics, the capacity has been reduced to 27.2 million cubic metres. The reservoir has not been desilted.
Sholayar Dam: Capacity: 153.48 million cubic metres. The current capacity is not known.
Peechi Dam: Capacity: 110.43 million cubic metres. A 2018 study found that the storage capacity has been reduced to 94.946 million cubic metres.
Palakkad district
The desilting process in the district began at Mangalam Dam. The intention was to remove three million cubic metres of sand and silt from the reservoir bed, enabling the structure to store an additional 300 crore litre of water. The desilting process which began in February 2021 was soon stopped, but resumed last week.
The desilting of Malampuzha Dam, which started in 2006, too, was stopped before completion. The same is the case with Chulliyar and Walayar Dams.
Wayanad district
Though a survey was conducted to desilt and augment the storage capacity of Karapuzha and Banasura dams, no further action was taken. Mudslides from mountains in Banasura's catchment area had ended up in the reservoir.
