Environmental effects of water resource development and use in the Tarim River basin of northwestern China

The unbridled development and use of water resources in the Tarim River basin over the last 50 years have led to a serious degradation of soil (>12×10³ km² of land desertified between the 1960s and 1990s) and water quality (rise in maximum salinity was from 1.3 g l^–1 in 1960, to 4.0 g l^–1 in 1981–1984, and to 7.8 g l^–1 in 1998). Approximately 300 km of the lower reaches of the river course dried up between the 1950s and 1970s, seriously altering the downstream hydrological processes (a 4–6 m drop in groundwater levels from the 1960s to the 1980s, and 0.2 m yr^–1 thereafter) and ecosystems (67% and 50% decrease (1958–1978) in Populus euphratica forest acreage and biomass, respectively). Between the 1950s and 1990s, 3820 km² of P. euphratica forest and 200 km² of shrub- and grassland were lost in the lower reaches of the Tarim River. In this study, based on estimates of soil organic carbon in desertified lands, it has been found that in the last 30 years (1970–2000), approximately 112 Tg of organic carbon (28% originating in the 0–1.0 m soil profile) has been released into the atmosphere as a result of soil degradation in the Tarim River basin. Intensive anthropogenic disturbance has been one of the foremost factors leading to the deterioration of water resources in this region. The key to solving these problems is to enhance the scientific and technical level of monitoring, management, and restoration of water resources and associated water and soil components of local ecosystems.