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<p>In many arid urban regions, increasing reliance on inter-basin water transfers and inadequate wastewater management have led to serious threats to groundwater quality and sustainability. Zahedan, located in southeastern Iran, is a prime example of such challenges. This study presents a comprehensive hydrogeological and environmental assessment of groundwater quality in Zahedan, where pressures from imported water and wastewater infiltration are intensifying. A total of 191 samples from diverse water sources were analyzed for major ions, stable isotopes (δ<sup>18</sup>O, δ<sup>2</sup>H), and microbial contaminants. Groundwater types ranged from Na–SO<sub>4</sub> in the west to Na–Cl in the east. Isotope analysis confirmed recharge from inter-basin transferred originating in Zabol, which raised the urban water table by 2–6&#xa0;m during 2002 to 2021. Over 80% of groundwater samples exceeded WHO nitrate guidelines for nitrate (50&#xa0;mg/L as NO<sub>3</sub>⁻), with a strong correlation between nitrate and fecal/total coliform contamination, highlighting the critical impact of urban wastewater. A mixing model identified contributions from multiple sources, especially water transferred from Zabol and local aquifers. Elevated fluoride, ammonia, and microbial loads were observed in shallow and low-discharge wells, suggesting an urgent need for targeted mitigation. These findings emphasize the complex interactions between urbanization, water transfer infrastructure, and aquifer vulnerability in arid regions.</p>

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Hydrogeological and environmental assessment of groundwater quality under urban stress: a case study from Zahedan, Iran

  • 期刊论文

  • 发表日期：

    2025年7月27日

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  • Reza Jahanshahi,
  • Alieh Allahdadi,
  • Sepideh Mali

摘要

In many arid urban regions, increasing reliance on inter-basin water transfers and inadequate wastewater management have led to serious threats to groundwater quality and sustainability. Zahedan, located in southeastern Iran, is a prime example of such challenges. This study presents a comprehensive hydrogeological and environmental assessment of groundwater quality in Zahedan, where pressures from imported water and wastewater infiltration are intensifying. A total of 191 samples from diverse water sources were analyzed for major ions, stable isotopes (δ18O, δ2H), and microbial contaminants. Groundwater types ranged from Na–SO4 in the west to Na–Cl in the east. Isotope analysis confirmed recharge from inter-basin transferred originating in Zabol, which raised the urban water table by 2–6 m during 2002 to 2021. Over 80% of groundwater samples exceeded WHO nitrate guidelines for nitrate (50 mg/L as NO3⁻), with a strong correlation between nitrate and fecal/total coliform contamination, highlighting the critical impact of urban wastewater. A mixing model identified contributions from multiple sources, especially water transferred from Zabol and local aquifers. Elevated fluoride, ammonia, and microbial loads were observed in shallow and low-discharge wells, suggesting an urgent need for targeted mitigation. These findings emphasize the complex interactions between urbanization, water transfer infrastructure, and aquifer vulnerability in arid regions.