Geospatial and Hydrogeochemical Insights for Monitoring Water Quality and Salinity in Coastal Regions of Southern Karnataka, India

Abstract

Coastal areas face significant challenges due to the depletion of groundwater and seawater intrusion into freshwater aquifers. Additionally, insufficient monitoring of freshwater quality is a major concern for consumers. In Karnataka’s Dakshina Kannada district, groundwater is crucial for meeting the needs of the community, industry, and agriculture. This study investigates the impact of excessive use, human activities, and agricultural chemicals on groundwater quality, with a focus on the hydrogeochemistry of the Natravathi and Gurapura catchments. The study analyzed 32 groundwater samples collected seasonally from 2021 to 2022 for 18 physiochemical parameters. The Water Quality Index (WQI) was determined using factors such as pH, Dissolved Solids, Oxidatio Reduction Potentisl, Electrical Conductivity, Total Hardness, Total Dissolved Solids, Calcium, Chlorides, Potassium, and Sodium. WQI scores ranged from 0 to 52 post-monsoon and 0 to 42 pre-monsoon. An ArcGIS-based spatial distribution map was created to show temporal changes in groundwater quality. Post monsoon measurements showed significant cations ranging from 4.25 to 64.54 mg/l, calcium from 40 to 520 mg/l, chloride from 40 to 200 mg/l, and potassium from − 8.05 to 15.44 mg/l. Pre-monsoon measurements indicated sodium levels from 28 to 208 mg/l, calcium from 240 to 840 mg/l, chloride from 19.99 to 159.9 mg/l, and potassium from 0 to 61.79 mg/l. WQI results for the post-monsoon season showed 36% of sampling sites as excellent, 52% good, 8% poor, and 4% very poor, while pre-monsoon results indicated 13% excellent, 46% good, and 42% poor. The research reveals higher toxin concentrations in drinking water during pre monsoon period compared to post monsoon, with increased salinity in freshwater aquifers making the water unsuitable for consumption. © 2025 The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.