Environmental and Ecological Engineering | Article | Published 2024
This work helps address recent calls for systematic water quality assessment in Central Asia and considers how nutrient and salinity sources, and transport, affect water quality along the continuum from glacier to lowland plain. Spatial and, for the first time, temporal variations in stream water pH, temperature, salinity (electrical conductivity), and nitrate and phosphate concentrations are presented for four catchments (485 – 13 500 km 2 ), all with glaciers and major urban areas. The catchments studied were: Kaskelen (Kazakhstan), Ala-Archa (Kyrgyzstan), Chirchik (Uzbekistan) and the Kofarnihon (Tajikistan). Measurements were made in cryosphere, stream water, groundwater, reservoir and lake samples over a 22-month period at fortnightly intervals from 35 sites. The results highlight that glacier, permafrost and rock glacier melt were primary and secondary nitrate sources (> 1 mg N l -1 ) to the headwaters, and there are major increases in salinity and nitrate concentrations where rivers receive inputs from agriculture and settlements. Overall, the water quality complies with national and World Health Organization standards, however there were pollution hot-spots with shallow urban groundwaters contaminated with nitrate (> 11 mg N l -1 ), and stream salinity above 800 µS cm -1 in some agricultural areas. Phosphate concentrations were generally low (< 0.06 mg P l -1 ) throughout the catchments, and elevated (> 0.2 mg P l -1 ) only in urban areas due to effluent contamination. A melt-water dilution effect along the main river channels was discernable in the electrical conductivity and nitrate concentration seasonal dynamics, even at the lowest monitoring points. Thus, the input of relatively clean water from cryosphere is an important regulator of main channel water quality in the urban and farmed lowland plains adjacent to the Pamir and Tien Shan, and improved sewage treatment is needed in urban areas.