Seawater intrusion into the coastal aquifer and the Kollidam river system has been posing a serious threat to agriculture and the environment in the tail-end areas of the Cauvery delta: the Chidambaram, Kattumannarkoil and Bhuvanagiri blocks, and some parts of Nagapattinam district.
Seawater has advanced through the Kollidam towards the plains, a distance of 20 km. One of the factors attributed for the situation is over-exploitation of surface and groundwater. Farmlands and habitations along the river are facing a severe water crunch. Even the groundwater has turned brackish in Chidambaram and Kattumannarkoil. Over a period of time, the water quality has deteriorated, from being fresh to brackish and then to saline. Hence, the farmers and residents demand speedy initiatives to prevent it becoming brine.
On a request from farmers, officials of the Public Works Department recently visited Vallambadugai to inspect the Kollidam and assess the viability of building a check-dam there. Cauvery Delta Farmers’ Welfare Association vice-president V. Kannan told The Hindu that the seawater intrusion, which had set in two-and-a-half decades ago, had now become critical. The major reason, he said, was over-exploitation of the surface water by the civic bodies along the course of the river. Residents and farmers were sinking borewells indiscriminately to meet their need for potable and irrigation water. Adding to the problem was the unbridled sand quarrying on the riverbed.
Sand had an excellent water retention capacity, he explained, and sand quarrying to a depth far beyond the permitted level would cripple the water flow and the groundwater replenishment.
For assessing the availability of fresh groundwater, Tamil Nadu has been divided into 385 blocks. Of these, 138 are over-exploited, 37 critical, 105 semi-critical, 8 saline and 97 safe. Mr. Kannan said the tail-end of the delta region fell in the semi-critical category. Crops would not survive in brackish and saline water. “If the situation was not reversed soon, it would have a long-term impact on soil quality, severely affecting grain production and food security.”
Kollidam-Keelanai Paasana Vivasayigal Sangam president P. Vinayagaya Moorthy told this correspondent that on the request of the Sangam, PWD officials visited Vallambadugai. The officials concurred with the farmers that a stable structure, capable of withstanding a flow of up to 3 lakh cusecs during monsoon, had to be put up across the river to prevent the seawater intrusion.
The officials also reckoned that such a project did not brook any delay. It could be speedily implemented if political leaders and the administration of both Cuddalore and Nagapattinam districts pressured the government. They also told the farmers that a proper study would have to be made to identify the right place for a check-dam or a barrage.
