The sedimentation study by an expert team from the Kerala Engineering Research Institute (KERI) continued in the reservoir of the Malampuzha dam, in spite of the winds slowing down the survey.
The team led by Deputy Director Shini K.K. is measuring the quantity of water available in the 22 sq km reservoir using Integrated Bathymetric System (IBS), a modern survey method used to measure the depth of waterbodies.
The amount of silt in the dam’s reservoir will be measured on the basis of the amount of water currently available. Malampuzha Dam, whose water is used both for drinking and irrigation, has a total capacity of 226 million cubic metres.
The survey team uses sonars for echo sounding and Differential Global Positioning System (DGPS) for accuracy. Data is collected at every two-metre interval. The data collected through DGPS and echosounder will be analysed using a computer software to get the exact volume of water.
Winds in reservoir
Ms. Shini said the winds in the reservoir area were affecting the movement of the survey boat. The team aimed at covering one square kilometre in day. However, she said they would finish the study in less than two weeks.
The last sedimentation study in the Malampuzha reservoir was done in 2014-15. Although that study was not an exhaustive one, many concerns have risen since, especially in the wake of the two floods of 2018 and 2019.
An opposite impact?
Although the general perception is that the floods caused by the landslips had brought a huge quantity of mud and soil into the reservoir, dam and irrigation experts have raised another theory that the heavy inflow and the spillage of muddy waters could have actually reduced the silt in the dam.
“It is possible. We have found it in our studies in Peechi,” said Ms. Shini. She said they did not expect a major increase in the volume of silt in the dam in spite of two major floods in successive years.
Desilting proposal
Malampuzha Dam, with its 145-sq km catchment area, has not been desilted since it was erected in 1955. The attempts to desilt the dam in 2010-12 had failed. Experts said desilting a dam like Malampuzha, which caters to the drinking needs of Palakkad and neighbouring places, would involve lots of technicalities. Desilting can even render the water undrinkable for a certain period. According to experts, nowhere in India has a dam been desilted successfully.
In the sedimentation study done in 2005, Malampuzha reservoir was found to have 30 million metre cube silt in it. The results of the current study will throw light on the volume of mud and soil that reached the reservoir in the last 15 years.
