From Aravalli hills to Thar sands: assessing groundwater quality dynamics and chemical contaminant trends across Rajasthan’s hydrogeological spectrum

Abstract

In arid Rajasthan, groundwater is the primary water source for domestic and agricultural needs across the state’s hydrogeological spectrum. However, pervasive chemical has been reported locally, and long-term statewide groundwater quality trends remain poorly characterized. This study presents a comprehensive 21-year spatiotemporal analysis of groundwater quality across Rajasthan, India, focusing on irrigation compatibility, human health risk, and regional hydrochemical evolution. Mann–Kendall, Modified Mann–Kendall and Sen’s slope tests were used to identify temporal trends in 12 key parameters (EC, major ions, nitrate, fluoride). Irrigation suitability was assessed using standard indices (SAR, RSC, Na%, KR, MH, PI, PS), and non-carcinogenic health risks were quantified via hazard indices for nitrate and fluoride ingestion. Hierarchical cluster analysis was applied to delineate evolving hydrochemical zones. Temporal analysis reveals statistically significant deterioration in salinity, sodicity, nitrate, and sulfate concentrations, particularly in the arid northwest and agriculturally intensive east. Key irrigation indices such as RSC (~ 269 mg/L), SAR (~ 43.8), and KR (> 2.5) consistently exceeded permissible limits, rendering most groundwater marginal to unsuitable for crop use. Concurrently, hazard index values for nitrate and fluoride ingestion averaged 2.35 (adults) and 2.99 (children), indicating chronic health risks in over various districts. Hierarchical cluster analysis delineated distinct hydrochemical zones, salinity-dominated west, nitrate-enriched agricultural belts, and fluoride-affected hard-rock terrains with increasing divergence over time. The emergence of complex contamination profiles underscores an accelerating groundwater quality crisis, demanding region-specific interventions. This integrated, multi-dimensional assessment provides critical insights for sustainable water management and policy planning in semi-arid and arid landscapes undergoing hydrochemical stress. © The Author(s), under exclusive licence to Springer Nature B.V. 2025.