Over-Exploitation and Pollution of Groundwater: A Case Study from Rasipuram Area, Tamil Nadu

Rasipuram and surrounding areas in Namakkal district of Tamil Nadu are known to be a zone of historically low groundwater levels, caused by large scale abstraction of groundwater. Study of hydrogeological conditions in the area has helped in identifying parameters that characterise an over-exploited zone. Majority of the dug wells in the area has been rendered unproductive due to lowered groundwater levels. The density of borewells is very high in certain pockets and the depths have been steadily increasing over the years. In the year 1998 the average depth of agricultural borewells was 192m, while that of drinking water borewells was 135m. It is estimated that if the present trend continues, the average depth of agricultural borewells in the year 2020 may reach 270m. The average yield (at the time of drilling) of agricultural borewells, is seen to be approximately the same despite the increasing depths. Over-exploitation of groundwater in the area has caused deterioration in the quality of groundwater with high levels of total hardness noticed in zones having deep groundwater levels. The role of baseflow in maintaining the quality of groundwater is discussed.