Urban India relies heavily on groundwater for drinking, yet anthropogenic pressures and natural geochemical processes threaten its quality. This study evaluates seasonal groundwater hydrochemistry at nine locations in Ahmedabad and Gandhinagar, Gujarat. Samples were collected during summer, monsoon, and winter (2023-2024). Fifteen physicochemical parameters, including heavy metals (As, Cd, Cr, Pb), were analyzed using standard APHA and USEPA methods, while coliform counts were assessed during winter to determine microbiological safety. Results indicate declining groundwater quality. Total Dissolved Solids (451-1795 mg/L), chloride (26.82-544.80 mg/L), and nitrate (1.99-211.95 mg/L) frequently exceeded WHO and BIS permissible limits, while nitrite-N surpassed limits in one sample (0.92 mg/L). Higher concentrations during summer were associated with evaporation and reduced dilution, whereas elevated nitrate levels suggested agricultural runoff. Electrical conductivity and hardness indicated significant rock-water interaction intensified by groundwater extraction. Correlation analysis revealed strong TDS-chloride relationships. Principal Component Analysis identified TDS, EC, and chloride as dominant contributors, with five components explaining 91.25% of total variance. Cluster analysis grouped Sites A and D with high similarity, while Sites I and E formed a distinct high-salinity cluster. Coliform counts peaked at Gyaspur (45 CFU/100 mL). Water Quality Index classified only 44% of sites as good, highlighting risks to drinking water quality and emphasizing the need for sustainable groundwater management aligned with SDG-6 and public health protection under SDG-3.