Assessment of drinking and irrigation suitability of coastal groundwater in eastern India using integrated numerical indices (WQI, SPI, and IWQI) and geospatial analysis

Under changing climatic conditions, coastal groundwater aquifers in eastern Odisha are increasingly vulnerable to quality deterioration. In response to the severity of this issue, the present study evaluates groundwater quality in a coastal block of Odisha using geospatial techniques combined with three widely applied numerical indices, i.e., Water Quality Index (WQI), Synthetic Pollution Index (SPI), and Irrigation Water Quality Index (IWQI), with the help of advanced software such as Python, ArcGIS, and RStudio. Physicochemical analyses of twenty-three groundwater samples reveal the predominant ionic sequences of Na + > Mg 2+ > Ca 2+ > K + . and Cl - > SO₄² - > HCO₃ - > NO 3 -. The WQI results indicate that nearly half of the groundwater samples are unsuitable for human consumption. Conversely, the SPI assessment reveals a broader range of pollution levels, with only a few samples deemed suitable, primarily in the western portion of the study area. The IWQI, integrated with GIS-based spatial analysis, indicates a deterioration in groundwater quality from the central to northeastern coastal zones, characterized by elevated levels of EC (Electrical Conductivity), SAR (Sodium Adsorption Ratio), and chloride in proximity to the shoreline and industrial areas. Na-Cl and mixed Ca-Mg-Cl hydrochemical facies, reflecting rock-water interactions, saline water intrusion, and anthropogenic influences. The USSL diagram suggests medium to high salinity with moderate sodium hazards. The SAR, RSC, Na%, PI, KR, and MH indices suggest that samples from the central and eastern regions exhibit a susceptibility to water contamination. Principal component analysis (PCA) identifies four major components, highlighting the combined effects of natural geochemical processes and localized human activities. Overall, the integrated application of numerical indices and geospatial pollution mapping provides a robust framework for formulating effective strategies for the sustainable management of groundwater resources for both domestic and agricultural use. • Integrated geospatial and numerical modelling (WQI, SPI, IWQI) revealed widespread groundwater quality deterioration in the coastal aquifers of eastern Odisha. • Hydrogeochemical facies analysis (Piper and USSL diagrams) indicated dominance of Na–Cl and mixed Ca–Mg–Cl water types, reflecting saline intrusion, rock–water interaction, and anthropogenic influences. • Water quality indices showed limited suitability for use, with only 47% of samples fit for drinking and the majority exhibiting moderate to severe irrigation restrictions due to salinity and sodium hazards. • Multivariate statistical analysis (PCA) explained 84% of the total variance, highlighting the combined impact of natural geochemical processes and localized human activities on groundwater quality.