Authors: Nitin Mishra

Abstract: Groundwater serves as a major source of freshwater for domestic consumption, irrigation, and industrial utilization in India, especially in highly populated regions such as Uttar Pradesh. In recent decades, groundwater quality has been increasingly threatened by rapid urban growth, intensive agricultural activities, industrial discharge, and natural hydrogeochemical interactions. Moreover, seasonal changes associated with monsoon rainfall significantly affect groundwater composition and contaminant distribution. In this context, the present study evaluates seasonal variations in groundwater quality using the Entropy Weighted Water Quality Index (EWQI) and hydrogeochemical interpretation techniques. Groundwater quality data for premonsoon and post-monsoon periods were collected from the Central Ground Water Board (CGWB), Uttar Pradesh. To maintain the accuracy and reliability of the dataset, quality assessment was performed using the Ion Balance Error (IBE) method. EWQI was calculated independently for both seasons to determine the suitability of groundwater for drinking purposes. The analysis revealed noticeable seasonal fluctuations in important physicochemical parameters such as Electrical Conductivity (EC), Total Dissolved Solids (TDS), Total Hardness (TH), nitrate, and fluoride. Higher concen-trations of dissolved constituents were generally observed during the premonsoon season due to limited recharge and increased evaporation, whereas postmonsoon groundwater exhibited com-paratively improved quality because of rainfall-induced dilution and aquifer recharge. Seasonal groundwater quality was evaluated using EWQI classification and hydrogeochemical analysis. The results indicated substantial seasonal variation in groundwater quality across the study area. The outcomes of the study indicate that the integration of EWQI and hydrogeochemical analysis provides an effective framework for groundwater quality assessment under varying seasonal conditions.The developed methodology can assist policymakers and water resource authorities in groundwater monitoring, pollution assessment, and sustainable groundwater management practic-es.

DOI: http://doi.org/10.5281/zenodo.20280351