Hydrogeochemistry and its relation to groundwater level fluctuation in the Palar and Cheyyar river basins, southern India

An investigation was carried out to understand the role of water level fluctuation on major-ion chemistry of groundwater in the Palar and Cheyyar river basins, southern India. As groundwater is the only major source of water for agricultural and drinking purposes in this area, it is important to know the effect of geological formations and agricultural activities on groundwater chemistry. Groundwater samples were collected once a month from 43 wells (6,41 samples in total). from January 1998 to June 1999, and analysed for major ions. The results indicate that the major-ion chemistry of the groundwater varies with respect to space. Groundwater occurring near the River Palar has a high concentration of major ions except calcium, due to the absence of any recharge from the river, whereas lower concentrations of major ions were observed in the central part of the study area due to the recharge of fresh water from a number of surface reservoirs. The major-ion chemistry of the study region is controlled by both mineral dissolution and anthropogenic activities. The relative contributions of mineral dissolution and anthropogenic contamination are estimated by a stoichiometric approach, which suggests that mineral dissolution is the dominant process in both the formations. The relation between water level fluctuations and major-ion chemistry indicates that major-ion chemistry is also greatly influenced by the water level fluctuations in different geological formations. Thus, the major-ion chemistry of groundwater in this region is greatly influenced by mineral dissolution, anthropogenic activities and water level fluctuations in different geological formations. Copyright (c) 2006 John Wiley & Sons, Ltd.