Impact of Monsoon Recharge on Groundwater Salinity: A Seasonal TDS Assessment in the Kadwa Basin, Maharashtra, India

Abstract

Groundwater quality is increasingly challenged in rapidly developing, monsoon-dependent regions, where both natural processes and human activities influence aquifer chemistry. This study evaluates seasonal changes in groundwater salinity through a comparative assessment of Total Dissolved Solids (TDS) using 110 paired groundwater samples collected during pre- and post-monsoon periods in the Kadwa Basin, Nashik district of Maharashtra. Pre-monsoon TDS concentrations ranged from 128 to 1,088 mg/L, whereas post-monsoon concentrations varied between 64 and 640 mg/L. The mean TDS declined from 503.73 mg/L prior to monsoon recharge to 285.09 mg/L afterward, indicating a reduction of approximately 39%. A paired-samples t test confirmed that this decrease was statistically significant, t (109) = 11.92, p < .001. The seasonal decline suggests that monsoon rainfall enhances dilution, improves aquifer flushing, and promotes mixing of fresher recharge water with stored groundwater. However, persistently elevated values at several sites indicate continued influence from agricultural inputs, wastewater seepage, and geogenic weathering processes. Comparison with drinking-water guidelines indicates that although quality improves after the monsoon, some wells remain unsuitable for direct consumption. The findings emphasize the need for sustained monitoring, regulated land-use practices, and integrated groundwater management strategies across monsoon-driven regions.