Influence of hydrological and hydrogeological factors on inland groundwater salinity in a hard rock aquifer, south India

Groundwater salinization has become a worldwide problem, impacting further agricultural advancements and thereby economic progress in various parts of the globe. Understanding the mechanism and processes behind groundwater salinization is crucial, especially in arid and semi-arid regions, where groundwater quality makes up the basic necessity for agriculture due to low rainfall with little to no surface water. To understand the salinity of groundwater, a monthly climatic water balance is calculated using climatological parameters. Change in the hydrochemistry between pre-monsoon and post-monsoon seasons with reference to local rainfall was used to assess the salinity change for the study period. Stable isotope (oxygen-18 and hydrogen-2) data of groundwater and rainfall was used to assess the groundwater recharge conditions in the study area. Climatic water balance studies show that cyclic dry and wet climatic conditions are favourable to accumulate salts on the surface of the soil, which later migrate to the water table during the monsoon season. Increased electrical conductivity values in most of the bore wells during the post-monsoon season further prove the migration of salts during the rainfall recharge, resulting in high salinity of the groundwater.