Journal articleOpen access
Geochemistry of groundwater in Tashkent artesian basin (Republic of Uzbekistan)
Геохимия подземных вод Приташкентского артезианского бассейна (Республика Узбекистан)
Highlights
- Eight aquifers; 69 wells; 144 observation points; average annual temperature 14.8 °C, precipitation 300–800 mm.
- Mineralization mostly below 1,000 mg/L; up to 5,680 mg/L in places on the plains; sulphate up to 3.8 g/L without gypsum or anhydrite saturation.
- Lower Quaternary aquifer (apQI) at 78–165 m, and 200–249 m in the south; 60–100 m thick, up to 197 m at Katta Ravot; yields 2.0–64.1 L/s; mineralization up to 500 mg/L.
- Middle Quaternary aquifer (apQII) covers up to 80% of the area, 80–100 m thick, mostly confined; mean mineralization 988 mg/L, up to 5,000 mg/L.
- About 30% of the waters are in equilibrium with calcite; Na-montmorillonite saturation at 18 of 69 points.
Keywords
- groundwater
- Pretashkent artesian basin
- hydrogeochemistry
- water–rock equilibrium
- Tashkent region
Summary
The study covers eight Quaternary aquifers of the Pretashkent artesian basin in Tashkent region, used for drinking water, industry and irrigation. It draws on 144 analyses of major ions from 69 wells along the Chirchik and Akhangaran river valleys, on the plains and in the foothills, and uses equilibrium thermodynamics to judge how far each water has reacted with the minerals around it.
All the aquifers hold fresh bicarbonate water, because they lie in the foothills and mountains of the Kurama and Chatkal ranges, where water is exchanged quickly. Only in places on the plains is the water sulphate-rich, with mineralization up to 5,680 mg/L. In water up to 1,000 mg/L, bicarbonate and sulphate dominate among the anions and calcium and sodium among the cations; above 1,000 mg/L, sulphate and sodium take over.
All the waters are saturated with montmorillonite clays and some with calcite; about 30% are in equilibrium with calcium carbonate. Even water with up to 3.8 g/L of sulphate does not reach saturation with sulphate minerals. On this basis the authors distinguish two geochemical types of water, siliceous calcium (magnesium) and siliceous carbonate–calcium, which differ in pH and in their main ions.
How to cite
N. V. Guseva and Yu. A. Otakulova (2014). Geochemistry of groundwater in Tashkent artesian basin (Republic of Uzbekistan). Bulletin of the Tomsk Polytechnic University, vol. 325, no. 1, pp. 127–136. https://izvestiya.tpu.ru/archive/article/view/1406