KOCHI: With the government giving its nod to desilt the Chulliyar and Mangalam dams owned by the Irrigation Department, the KSEB is also working on a similar proposal. Senior KSEB officers said many small and medium dams have lost up to 50 per cent of their storage capacity due to accumulation of silt in the reservoir bed. Desilting will improve storage, help effective flood management and conserve more water to meet the summer shortage, they said.
However, it’s easier said than done, as dredging or opening of sluice gates can lead to contamination of water and force potable water projects downstream to stop. The desilting work should be undertaken by the government as it needs coordinated effort of different departments. Dumping of the removed silt is another problem, as most dams are located in forests and the Forest Department may object to dumping of silt on forest land.
Though KSEB feels it necessary to desilt the dams, it is yet to submit a formal proposal to the government. “KSEB had conducted a study in 1993 on the accumulation of silt in dams which revealed many small dams lost up to 25 per cent storage capacity over the years. It has been 25 years since the study and the silt level would have risen to 50 per cent by now,” said an officer.
“We definitely want to desilt the dams, but would prefer to wait till desilting of Irrigation Department dams are over. After evaluating its results, we will submit a formal proposal before the government,” said KSEB chairman N S Pillai. “There is no emergency as major dams like Idukki, Idamalayar, Kakki and Pampa have not been affected. Normally, the dams do not get filled during the monsoon. This year, we had unusually heavy rainfall which filled up the dams. It is a fact huge quantity of silt has accumulated in dams due to the flow of debris in the recent floods. Small dams like Poringal have lost significant amount of storage capacity as a result.”
“The Poringalkuthu dam lost around 50 per cent of its storage capacity due to accumulation of silt. The storage capacity of many other small dams like Panniyar, Lower Periyar, Alumpara and Vellathooval have dropped significantly too.
The custodians of the dams have reported the problem and the proposal is under process. It is for the government to make a decision in this regard,” said KSEB Engineers’ Association president N T Job.The Kerala Dam Safety Authority (KDSA) has also recommended the government to desilt the dams as many reservoirs have lost more than 30 per cent of their storage capacity.
Works to strengthen the dams under the Dam Rehabilitation and Improvement Project are progressing at Chimmony and Kanjirappuzha dams. KDSA has also recommended construction of a support dam at Kuttiady as the old dam would have lost strength. “Many small dams like Lower Periyar, Poringal, Kallarkutti and Sengulam need to be desilted. However it is a big challenge as the work needs to be done without affecting power generation and potable water projects,” said KDSA chairman C N Ramachandran Nair.