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Hydrochemical characteristics of groundwater in Central Tajikistan

Хусусиятҳои гидрохимиявии обҳои зеризаминии Тоҷикистони Марказӣ

F. I. Nazhmudinova, A. S. Qodiri, I. M. Rakhimov

  1. Center for Innovative Development of Science and Digital Technologies, National Academy of Sciences of Tajikistan, Dushanbe, Tajikistan
PDF3.7 MB Cite

https://doi.org/10.65599/eng4873

Politekhnicheskii vestnik. Seriya: Inzhenernye issledovaniya (Polytechnic Bulletin. Series: Engineering Research), No. 3 (75)

Date2026

Issue2026, pp. 24–31

LanguageTajik (Russian and English abstracts)

LicenceNot stated

Published byTechnical University of Tajikistan named after Academician M. S. Osimi

Highlights

  • 15 sampling points in and around Dushanbe, sampled in 2023–2025.
  • pH 7.0–7.6; Eh 347–517 mV; EC 25.5–98.3 mS/m (highest at TJK 25 and TJK 92).
  • Ca²⁺ 39.8–114.6 mg/L; Mg²⁺ 9.1–50.8 mg/L; Na⁺ 7.9–121.8 mg/L.
  • HCO₃⁻ 213–555 mg/L (highest at TJK 44, lowest at TJK 3); SO₄²⁻ 27.0–147.3 mg/L; Cl⁻ 6.8–24.2 mg/L.
  • NO₃⁻ 0.6–49.9 mg/L (highest at TJK 2).
  • Total hardness 176–420 mg/L as CaCO₃; water mainly of the Ca–Mg–HCO₃ type.

Keywords

  • groundwater
  • hydrochemistry
  • bicarbonate
  • nitrate
  • sulfate
  • drinking water
  • Tajikistan

Summary

F. I. Nazhmudinova, A. S. Qodiri and I. M. Rakhimov of the Center for Innovative Development of Science and Digital Technologies of the National Academy of Sciences of Tajikistan describe the chemistry of groundwater in central Tajikistan, around Dushanbe. In 2023–2025 they sampled 15 points in valleys, foothills and settlements, chosen to cover different hydrogeological zones and located by GPS. In the laboratory they measured pH, electrical conductivity (EC), redox potential (Eh) and the major cations (Na⁺, K⁺, Ca²⁺, Mg²⁺) and anions (HCO₃⁻, Cl⁻, SO₄²⁻, NO₃⁻); bicarbonate was calculated from alkalinity and hardness from calcium and magnesium.

The water is neutral to weakly alkaline, with pH 7.0–7.6, and oxidising, with Eh of 347–517 mV. EC ranges from 25.5 to 98.3 mS/m and is highest at points TJK 25 and TJK 92. Calcium leads the cations at 39.8–114.6 mg/L, with magnesium at 9.1–50.8 mg/L and sodium at 7.9–121.8 mg/L; potassium is low in all samples. Bicarbonate leads the anions at 213–555 mg/L, highest at TJK 44 and lowest at TJK 3. Sulphate is 27.0–147.3 mg/L and chloride 6.8–24.2 mg/L. Total hardness is 176–420 mg/L as CaCO₃, so most samples are hard or very hard.

The water is mainly of the Ca–Mg–HCO₃ type, which the authors attribute to the dissolution of carbonate minerals and water–rock interaction. Nitrate is 0.6–49.9 mg/L, highest at TJK 2: below the World Health Organization guideline value, but close to it at some points. The authors link higher nitrate to human activity, including mineral fertilisers and household wastewater. Sulphate stays below the WHO value of 250 mg/L. They conclude that most of the groundwater is suitable for drinking and household use. Ground temperatures, thermal conductivity and groundwater chemistry for ground-source heat pumps in Dushanbe were measured at the same centre.

Figures (2)

Satellite image of Dushanbe and its surroundings under a lettered and numbered grid of 1.7 km squares, with red dots for groundwater and blue dots for river water sampling points
Fig. 1. Map showing the locations of groundwater sampling points in the study area (red: groundwater; blue: river water). Source: F. I. Nazhmudinova, A. S. Qodiri and I. M. Rakhimov (2026), Nazhmudinova et al. (2026), Fig. 1.
Bar chart of sulphate at 15 sampling points, from about 27 mg/L at TJK47 to about 145 mg/L at TJK25
Fig. 3. Variation in water sulfate concentration at points within the study area. Source: F. I. Nazhmudinova, A. S. Qodiri and I. M. Rakhimov (2026), Nazhmudinova et al. (2026), Fig. 3.

How to cite

F. I. Nazhmudinova, A. S. Qodiri and I. M. Rakhimov (2026). Hydrochemical characteristics of groundwater in Central Tajikistan. Politekhnicheskii vestnik. Seriya: Inzhenernye issledovaniya (Polytechnic Bulletin. Series: Engineering Research), No. 3 (75), 2026, pp. 24–31. https://doi.org/10.65599/eng4873