THIRUVANANTHAPURAM: Nine months after the mid-August floods that ravaged the state last year, the Irrigation Department has decided to float global tenders to desilt two of its dams in the state on a pilot basis. The desilting is expected to take off after the monsoon season.
“We have been working on the project for some time. The final DPR (detailed project report) has been submitted to the state government. The global tenders can be floated based on the government’s approval,” said a senior officer with the Irrigation Department.
Water Resources Minister K Krishnankutty confirmed the process to desilt the Mangalam and Chulliyar dams is in the final stages. Though there had been plans to desilt the state’s dams since the 90s, this is the first time the state is experimenting with desilting an entire dam on a commercial basis. Based on the progress of the work in the two dams, the state government would take a call on desilting other dams and barrages in the state.
Irrigation Department officers said the desilting work would be awarded as ‘work contract’ and ‘turnkey’ mode. The silt removed from the dams would be provided to farmers for enhancing the fertility of their land, the clay would be given to industries, while the sand would be exploited commercially. The cost of desilting Chulliyar dam is estimated at Rs 60.2 crore which would be awarded on ‘work contract’ basis. The desilting of Mangalam dam would be carried out via ‘turnkey’ mode and its cost will be decided through competitive bidding.
A study by the National Centre for Earth Science Studies and Kerala Engineering Research Institute had found the silt had reduced the storage capacity of Chulliyar dam by 8.22 per cent. The storage capacity of Mangalam dam reduced by 11.7 per cent due to accumulation of silt.In Chulliyar dam, 55 per cent of the accumulated sediment is fine sand, while 43 per cent is clay residue. In Mangalam dam, 34.6 per cent of the sediment is fine sand, while 60 per cent is clay content.
How it will be done
The firm engaged to desilt the dams will pump the stored water to a designated place using high-power pumps. The water will be released into the reservoir again after the segregation of silt from the sand, for which a standard operating procedure has been accepted.
Why is it being done?
The Irrigation Department is the custodian of around 60 dams and four barrages in the state all of which have huge deposit of sedimentation. Desilting them will significantly enhance their carrying capacity. The shortage of storage space due to silt accumulation had been one of the talking points during the mid-August floods.