Study On Temporal And Spatial Variations Of Water Chemistry And Its Influence Factors In Lhasa River Catchements, Tibet

Lhasa river is known as "Mother River" in Lhasa. It is the main artery of economic development within the river basin. Lhasa City- the capital of Tibet Autonomous Region is located on the north bank of the low reaches of the River. The city is the political, economic and cultural center of Tibet. As the main surface water, the Lhasa river is one of the major water sources for drinking water, animal husbandry, agricultural and industrial water in the catchements. Human activities, containing the results of the damming, exploration of geothermal and mineral resources and, discharge of municipal wastes, have already dramatically destroyed the environmental hydrochemistry of Lhasa river in time and geographical coordinates. both in time and geographical coordinates. Some pollutants, such as Cu, Cd, Pb and As ions, have significantly affected on the ecological environment and human health and also detected the overproof amount within the river catchments. In particular, elevated levels of heavy metals(including Cu, Pb, Zn and Hg) were found in the surface sediments of the river downstream of mining sites. Therefore, a comprehensive study of water chemistry in the river catchments is prerequisited for the sustainable management of abundant water resources.This study was conducted mainly in the middle and lower reaches of the Lhasa River(about 300 km) and its major tributaries. Based on the measured major water physicochemical parameters and water chemistry data in different water periods, chemical composition(major ions and trace elements) of the river was evaluated; mathematical statistic methods were applied for examination of the temporal and spatial variations of water chemistry in the river cachments and, major controlling factors of the water chemistry were analized; Pollution souces and the potential environmental pressures were also identified within the watershed. This study provides a scientific basis for future sustainable development and utilization of the rich natural resources in the river basin.