Problems of water resource qualityIntensive development of irrigation farming and land drainage in Central Asia together with growing water use for industrial and household needs resulted in increased abstraction of fresh water and discharges of polluted return flow into water bodies. The main pollution sources are agrochemicals that are washed out into drainage systems and are mixed with river water. The second-ranking source in terms of impact on the quality of the water resources is the effluent from municipal and industrial sewers. National reports also note an increased contamination of groundwater due to substandard management of municipal and industrial waste sites, especially in the mining industry. River quality statistics for the past 40 years confirm trends of an increased mineralization, both over time and in terms of the length of the rivers affected. For instance, in the late 1960s, average mineralization of water did not exceed 1.0 g/l even in the Amudarya estuary. At present, it varies from 0.3-0.5 g/l in the upper reaches to 1.7-2.0 g/l in the lower reaches (table 7). The possibility of using water for irrigation depends not only on the mineralization but also on the chemical content. Thus, a consistent trend has developed for changes in the ionic composition of salts in the water toward a dangerous increase in alkalinity. Until now, due to a high content of gypsum in soils and CaSO4 in water, the alkalinity (SAR) has remained below the maximum allowable level, yet soil reserves of gypsum are expected to diminish, leading to leaching and increasing concentrations of sodium carbonate. The increasing mineralization of water in rivers and the intensity of drainage from irrigated land substantially affect the dynamics of salinization and increase the need for reclamation of irrigated areas. An example is shown in table 7 with the water-salt balance of the Amudarya. It is shown that only about half of the more than 50 million tons of salt annually ending up in the river stems from a natural run-off, with the rest formed by run-off from the drained return flow. An analysis of the salt balance in rivers and irrigated lands makes it possible to pinpoint salt accumulation areas in terms of reclamation needs of irrigated lands whose productive capacity is either diminishing or remains at the lowest level of safety. In the Amudarya basin, such areas include, for instance, areas of the Turkmen coast, Tashauz and Karakalpakistan. Similar changes in water content have occurred in the Syrdarya basin. Salt content in its upper reaches of the Syrdarya does not exceed 0.3-0.5 g/l, whereas salt content at the site where the river exits from the Fergana Valley climbs up to 1.2-1.4 g/l, and at the Kazalinsk city site exceeds 1.7-2.3 g/l. Mineralization has increased from 1960-1970 levels in all controlled sections. Increases in overall mineralization are accompanied by higher concentrations of magnesium, copper, iron, sulphates, chlorides, etc. As a result, not only lower reaches but also the medium course of the Syrdarya contain water that is unacceptable for drinking and its significant pollution quite often leads to increased morbidity of the local people. Prevailing diseases are related to the quality of drinking water and include hepatitis, typhoid and gastrointestinal disorders. The overall average annual mineralization by representative sections of the Syrdarya are shown in table 8. National reports indicate that a certain reduction in the mineralization that occurred in the late 1990s in inter-State rivers was due to a temporary slowdown in water use for irrigation and by industries. In the meantime, contamination of groundwater has become widespread. For some pollutants, content levels exceed maximum allowable concentrations by dozens – and, in some areas, by hundreds of times. The highest incidence of groundwater contamination has been recorded around large settlements, chemical, oil refining and non-ferrous metallurgical plants, etc. Statistics for 1995-2001 indicate that, on average, 8-15% of water samples fail to satisfy bacteriological requirements and 20-40% fall short of physical and chemical standards. National experts voice concern over the unsatisfactory technical condition of sewage disposal facilities (in 60-70% of all cases) that fail to provide efficient treatment of sewage and industrial effluent. The following priority measures have been proposed to address the water quality problem:
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