Kochi: If the Kerala government’s plan to desilt the Malampuzha dam, the biggest irrigation dam in the southern state, succeeds, it will not only increase the storage capacity of the dam but also fetch the state at least Rs800 core through the sale of sand, extracted from the sediment.
This is the first time the government is attempting such a project. Last week, it invited expressions of interest, or EoIs, with a 15 July deadline. Successful bidders, either firms or a consortium, will have up to three years to complete the desilting.
Work on the dam, in the northern district of Palakkad, began in 1953. It was partially commissioned in 1956 and finally completed in 1964.
It has a catchment area of 147.63 sq. km. The water is stored over an area of 22 sq. km and the reservoir has a storage capacity of 226 million cu. m.
The state water department had in March authorized the Kerala Engineering Research Institute, or Keri, to conduct a study. According to Keri’s report, roughly 30 million cu. m of sediment would need to be removed from an area of around 15 sq. km.
The study pointed to a loss of around 12% storage capacity because of sedimentation. It also estimated that about 8 million cu. m of sand could be extracted from the area, and valued it at around Rs800 crore at current rates.
“It’s a novel and unique concept. Sand is a scarce resource and its illegal mining from the rivers has affected the water table,” said N.K. Premachandran, state water resources minister. “It was during the last budget that there was a proposal to dredge sand silted in dams across the state.”
State finance minister Thomas Isaac had said during his budget presentation earlier this year that silt deposits had reduced the water storage capacity in major dams by 30-40%.
Initial plans involved desilting a few dams, but were scaled back to desilt just one irrigation dam to start with. Selling the sand recovered through desilting would serve a dual purpose: revenue for the government and increased storage for the dams.
On whether there would be any environmental impact because of the dredging and removal of sedimentation, Premachandran said the sand would be mined 500m from the dam, with little impact and no damage to the reservoir.