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<p>Groundwater is an essential supply of freshwater in the peri-urban area of Southwest Delhi, India. This study is novel in its dual-seasonal (pre-monsoon and post-monsoon) analysis of groundwater chemistry and recharge dynamics using stable isotope (δ<sup>2</sup>H&#xa0;and δ<sup>1</sup>⁸O) at different depths which highlighting the groundwater-drain water&#xa0;(GR-DRW) interactions. The findings indicated that both groundwater (EC range: 262–9581 μS/cm in pre-monsoon, 763–8600 μS/cm in post-monsoon) and drain water (ECrange:2120- 5326 μS/cm in pre-monsoon,1935–3600 μS/cm in post-monsoon) had salinity beyond the permissible limit in both the seasons.The observed dominance of anions in groundwater and drain water was in the order of HCO<sub>3</sub><sup>−</sup> &gt; Cl<sup>−</sup> &gt; NO<sub>3</sub><sup>−</sup> &gt; SO<sub>4</sub><sup>2−</sup>, while the cations followed the order Na<sup>+</sup> &gt; Ca<sup>2+</sup> &gt; Mg<sup>2+</sup> &gt; K<sup>+</sup>. The stable isotopic data for the deep groundwater shows the most depleted δ<sup>18</sup>O (-9.13‰) and δ<sup>2</sup>H (-54.17‰) values, indicating minimal evaporation and longer residence times. Moderate depth groundwater has δ<sup>18</sup>O and δ<sup>2</sup>H value shows less depleted (-6.47‰ and -45.09‰). Shallow groundwater (δ<sup>18</sup>O: -6.17‰ to -3.23‰, δ<sup>2</sup>H: -42.75‰ to -31.02‰) and drain water (δ<sup>18</sup>O: -6.91‰ to -2.21‰, δ<sup>2</sup>H: -48.02‰ to -35.52‰) exhibit enriched isotopic values due to evaporation in the pre-monsoon season. In the pre-monsoon season, recent recharge from precipitation or snowmelt slightly influences isotopic values, with deep groundwater at δ<sup>18</sup>O: -7.85‰ and δ<sup>2</sup>H: -47.13‰, and shallow groundwater at δ<sup>18</sup>O: -5.66‰ to -1.82‰ and δ<sup>2</sup>H: -48.57‰ to -39.91‰. Furthermore, the analysis of d-excess values reveals that deep groundwater has the highest d-excess (21.27‰) during pre-monsoon, indicating minimal evaporation. Shallow groundwater (-0.70‰) and drain water (-4.03‰) show negative d-excess, suggesting evaporative enrichment. In post-monsoon, d-excess values decrease overall, with drain water (-16.08‰) showing significant evaporation effects. Therefore, this study is crucial for managing groundwater resources in peri-urban areas of Southwest Delhi,&#xa0;where the freshwater scarcity is a growing concern.</p>

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A Stable Isotope-hydrochemical Approach to Assess Groundwater Chemistry and Recharge Dynamics in Southwest Delhi, India

  • 期刊论文

  • 发表日期：

    2025年10月3日

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  • Mamta Bisht,
  • Manoj Shrivastava,
  • Sudhir Kumar,
  • Dhirendra Kumar Singh,
  • Vinay Kumar Sehgal

摘要

Groundwater is an essential supply of freshwater in the peri-urban area of Southwest Delhi, India. This study is novel in its dual-seasonal (pre-monsoon and post-monsoon) analysis of groundwater chemistry and recharge dynamics using stable isotope (δ2H and δ1⁸O) at different depths which highlighting the groundwater-drain water (GR-DRW) interactions. The findings indicated that both groundwater (EC range: 262–9581 μS/cm in pre-monsoon, 763–8600 μS/cm in post-monsoon) and drain water (ECrange:2120- 5326 μS/cm in pre-monsoon,1935–3600 μS/cm in post-monsoon) had salinity beyond the permissible limit in both the seasons.The observed dominance of anions in groundwater and drain water was in the order of HCO3− > Cl− > NO3− > SO42−, while the cations followed the order Na+ > Ca2+ > Mg2+ > K+. The stable isotopic data for the deep groundwater shows the most depleted δ18O (-9.13‰) and δ2H (-54.17‰) values, indicating minimal evaporation and longer residence times. Moderate depth groundwater has δ18O and δ2H value shows less depleted (-6.47‰ and -45.09‰). Shallow groundwater (δ18O: -6.17‰ to -3.23‰, δ2H: -42.75‰ to -31.02‰) and drain water (δ18O: -6.91‰ to -2.21‰, δ2H: -48.02‰ to -35.52‰) exhibit enriched isotopic values due to evaporation in the pre-monsoon season. In the pre-monsoon season, recent recharge from precipitation or snowmelt slightly influences isotopic values, with deep groundwater at δ18O: -7.85‰ and δ2H: -47.13‰, and shallow groundwater at δ18O: -5.66‰ to -1.82‰ and δ2H: -48.57‰ to -39.91‰. Furthermore, the analysis of d-excess values reveals that deep groundwater has the highest d-excess (21.27‰) during pre-monsoon, indicating minimal evaporation. Shallow groundwater (-0.70‰) and drain water (-4.03‰) show negative d-excess, suggesting evaporative enrichment. In post-monsoon, d-excess values decrease overall, with drain water (-16.08‰) showing significant evaporation effects. Therefore, this study is crucial for managing groundwater resources in peri-urban areas of Southwest Delhi, where the freshwater scarcity is a growing concern.