Hydrochemical Evolution in Stressed Aquifers: Role of Groundwater Extraction, Recharge, and Lateral Flow Systems in India

Abstract

In the last few decades, intensive groundwater extraction for irrigation in India has severely depleted aquifers, with growing concerns over groundwater quality. This study the first national-scale assessment linking hydrochemical evolution with extraction intensity, integrating depth-to-water levels (DTWs), groundwater recharge (GWR), and water quality parameters with the stage of groundwater extraction (SoGE) across alluvial (ALV) and hard-rock (HR) aquifers. Results show that increasing groundwater stress is associated with rising pH, declining DTWs, reduced GWR, and overall water quality deterioration, particularly within over-exploited, critical, and semi-critical (OCS) units. Within critical SoGE ranges (~ 60–140% in ALV; ~ 50–160% in HR), Na⁺, Cl⁻, SO₄2⁻, NO₃⁻, F⁻, and TDS increase, with stronger responses in HR aquifers. Fluoride and nitrate enrichment, linked to anthropogenic inputs, irrigation returns, peak within these ranges but declines beyond the thresholds. PCA results further indicate NO₃⁻ dominance in ALV aquifers due to irrigation-derived inputs under permeable soils, whereas F⁻ dominance in HR aquifers signifies stronger lithological control and water–rock interaction. At higher SoGE, deeper flow systems, characterised by longer residence times and stronger geogenic processes, predominate with reduced anthropogenic influence. While TDS generally increases with SoGE, states (e.g., Punjab, Haryana, Uttar Pradesh, Delhi, Tamil Nadu) exhibit stable or declining trends, attributed to possible lateral groundwater inflows from foot-hills, river valleys, and palaeochannel networks that buffer water quality under stress. However, this buffering effect weakens under extreme abstractions (> ~200% SoGE). Recognising and preserving such lateral flow pathways, wherever existing, is therefore critical for sustainable groundwater management in stressed aquifer systems. National-scale assessment links groundwater extraction (SoGE), recharge, and hydrochemical evolution. Rising SoGE lowers DTWs, reduces recharge, raises pH and deteriorates water quality. Hard-rock (HR) aquifers are more vulnerable to groundwater stress than alluvial (ALV) aquifers. Critical SoGE ranges (~ 60–140% in ALV; ~ 50–160% in HR) show sharp increases in groundwater solutes. Beyond critical SoGE, F⁻ and NO₃⁻ decline, especially in HR aquifers. Some highly stressed states show declining TDS, suggesting lateral flow influence. Under extreme SoGE, lateral flows may no longer sustain groundwater quality. National-scale assessment links groundwater extraction (SoGE), recharge, and hydrochemical evolution. Rising SoGE lowers DTWs, reduces recharge, raises pH and deteriorates water quality. Hard-rock (HR) aquifers are more vulnerable to groundwater stress than alluvial (ALV) aquifers. Critical SoGE ranges (~ 60–140% in ALV; ~ 50–160% in HR) show sharp increases in groundwater solutes. Beyond critical SoGE, F⁻ and NO₃⁻ decline, especially in HR aquifers. Some highly stressed states show declining TDS, suggesting lateral flow influence. Under extreme SoGE, lateral flows may no longer sustain groundwater quality.