Hydro-Ecological Situation in the Basin of the River Zaravshan in Uzbekistan

The Zaravshan River Basin is one of the most densely populated areas in Central Asia. The length of Zaravshan River is 877 km, the watershed area is 17.7 thousand km2, and the population is more than 5 million. The current social and economic situation in this region requires a significant increase of water supply to communal and household needs, developing industry, irrigated agriculture and other fields of the national economy. Although the Zaravshan River is the sole source of potable water supply, it receives communal, household, industrial and agricultural sewage in Leninabad province of Tajikistan, and the Samarkand and Navoi provinces of Uzbekistan. All along, the river is characterized by intensive pollution by agricultural, stock-breeding, industrial and sewage waste flow. Consequently, it is one of the most polluted rivers in Central Asia. Impoverishment of water resources in this area has been caused by significant consumption of water for irrigation and drainage of agricultural lands. Drainage water brings herbicides, pesticides and defoliants. Salinity of water increases 6–8 times from the river head to the river outlet - from 0.27–0.30 g/l to 2–2.4 g/l. Particularly in its lower part it becomes unusable for drinking purposes due to chemical contamination. Since there are no water and sewage systems in rural areas, population of the region receives water that does not meet any health related requirements. At the same time, a tense situation with water utilization and ecology is developing in the region which no doubt manifests itself in the health situation of the region. The situation is also worsening because a number of residents in rural areas use water from open reservoirs and canals for household needs and drinking. According to the report of the Central hydro-meteorology service of Uzbekistan, the quality of water in the Zaravshan River is of class IV by the Surface Water Pollution Index, which means polluted and heavily polluted water. The most contaminated water is in the area below the Navoi city. The maximum concentration of pollutants, which are the major indicators of contamination of water reservoirs with organic and biogenic substances in this area is: phenol - 0.005 mg/L (5 times higher than the maximum allowable concentration (MAC)), petroleum products - 0.64 mg/L (12.8 MAC), nitrates - 0.202 mg/L (10.1 MAC). Such concentrations of these substances are mostly due to the existing anthropogenic pressures on the water resource.

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