A spatiotemporal evaluation of groundwater quality was undertaken to assess its drinking and irrigation in the alluvial aquifers of Malda district, West Bengal, for 2015 and 2023. Hydrochemical analysis revealed notable temporal shifts, including an increase in alkalinity (pH from 7.9 to 8.6), reduction in electrical conductivity (EC) (from 1086 to 668 µS/cm), and decreased concentrations of major ions, specifically calcium, sodium, and chloride. However, increased potassium and fluoride concentrations beyond the WHO safe limits point to emerging health risk concerns. Hydrochemical facies classification suggested that silicate weathering and rock–water interactions predominantly control groundwater chemistry, with secondary contributions from anthropogenic activities such as intensive agriculture and urban expansion. Multivariate statistical analysis revealed significant shifts in ionic compositions and salinity drivers over time. The temporal analysis showed a decline in drinking water quality, with regions transitioning from “good” or “excellent” in 2015 to “poor” or “unsuitable” in 2023, particularly in the northeastern and central zones. Despite a general decline in major anion and cation concentrations from 2015 to 2023, the Water Quality Index (WQI) analysis revealed a deterioration in overall groundwater quality, rendering a significant portion of the water unsuitable for drinking. This paradox is primarily attributed to elevated levels of fluoride and increased pH values observed in 2023. Indicators of irrigation suitability produced mixed results; although sodium-related risks decreased, rising magnesium levels in 2023 raised concerns regarding potential soil degradation. Notably, an improved Permeability Index suggests enhanced water infiltration, which is favourable for irrigation in certain areas. This study highlights the dual nature of groundwater quality evolution, both improvements and emerging threats, underscoring the need for region-specific mitigation strategies to address fluoride contamination and optimize irrigation practices. Achieving these objectives requires a collaborative effort among policymakers, communities, and scientists, which is crucial for sustainable groundwater management and resource utilization, ensuring long-term suitability for drinking and agricultural purposes.