Evaluation of spatio-temporal variability of groundwater quality for irrigational suitability and its relation with climatological parameters in the Pondicherry region, India

Abstract

Groundwater quality in coastal aquifers is increasingly threatened by climate variability, intensive abstraction, and saline intrusion, directly affecting agricultural sustainability. This study evaluates the spatio-temporal variability of groundwater quality for irrigation and its relationship with climatological parameters in the Pondicherry coastal region, southeast India. Seventy groundwater samples were collected during pre-monsoon and post-monsoon seasons of 2023 and analyzed for major physico-chemical parameters. Irrigation suitability was assessed using standard indices, including Sodium Adsorption Ratio, Percent Sodium, Residual Sodium Carbonate, Magnesium Ratio, Kelley's Index, and Permeability Index, supported by Wilcox and U.S. Salinity Laboratory classifications. Spatial distribution maps were generated using geographic information system techniques, and long-term rainfall and temperature data (2010–2022) were correlated with groundwater quality indicators.

The groundwater chemistry is dominated by sodium–chloride and calcium–bicarbonate facies, reflecting the combined influence of seawater intrusion, carbonate weathering, and recharge processes. Most groundwater samples (approximately 80–85%) are suitable for irrigation in both seasons; however, persistent salinity and sodium hazards were identified in coastal locations such as Muthialpet, Thengaithittu, and Kirumampakkam. POM conditions show improved groundwater quality due to recharge-induced dilution. A strong negative correlation between rainfall and electrical conductivity, and a positive correlation between temperature and salinity, demonstrate the controlling influence of climatic variability on groundwater chemistry.

The results highlight that seasonal recharge enhances irrigation suitability, whereas over-extraction and marine intrusion degrade groundwater quality in coastal aquifers. The integrated hydrochemical, spatial, and climatological approach provides a robust framework for sustainable groundwater management in climate-sensitive coastal regions.