Areas around Minjur and Panchetti continue to be vulnerable to seawater ingression owing to the overexploitation of groundwater sources.
Farmers in the region struggle to cultivate crops once in a year as they depend on surface water from local sources and the monsoon. Public water supply is the only source for drinking as groundwater has been saline for years now.
A three-year-study made by the Department of Geology, Anna University, in the Minjur-Ponneri belt reveals that the seawater had intruded up to 14.7 km into land this May. S.P. Rajaveni, one of the team members, said the groundwater level has dipped 15 metres below sea level in Minjur and Panchetti and this has paved the way for the mixing of seawater with freshwater.
K.E. Subramanian, a resident of Thathaimanji located about 12 km from Minjur, says he cultivates paddy once in a year during the northeast monsoon and harvests by February. “I make only minimal profits as I can’t use groundwater. But I don’t want to leave my lands barren. The government must help us by constructing more checkdams in Araniar and Kosasthalaiyar rivers and providing warehouses,” he said.
More salt pans, which were confined to areas closer to the coast, have come up in the region as salinity has increased in the groundwater. Indu Nair, who was involved in the study, said in 2007, the seawater intrusion was recorded till 10 km into land near Minjur belt.
The team took groundwater samples from 50 locations for a radius of 25 km from the coast. The samples were taken once in two months from 2012.
L. Elango, professor, Department of Geology, noted that the seawater intrusion comes down during December by 3 km.
“Even if there is over-exploitation of groundwater sources in Poondi located about 50 km away from the coast, it will have an impact on Panchetti and Minjur belt and increase seawater ingression in Araniar-Kosasthalaiyar river basin. This is because the aquifer formation is the same in the region,” he said.
The government may increase the number of check dams, increase the level of existing check dams and also encourage farmers to create percolation ponds to mitigate impact of seawater intrusion and recharge groundwater, he added.