The characteristics of ground-water resources and their changes under the impacts of human activity in the arid Northwest China-a case study of the Shiyang River Basin

Based on a hydrogeological survey and geochemical and isotopic technology, a case study of the Shiyang River Basin is presented to illustrate ground-water resources and geochemistry and their changes caused by the impact of human activity in the arid area of Northwest China. The aquifer is mainly recharged by surface water originating in mountain regions, and there is extensive transfer between rainfall, surface water and ground-water. The deep ground-water is old, approximately 40 ka, and was recharged in a colder and wetter climate environment. The shallower water is mainly palaeowater mixed with limited modern recharge. The sources of salinity are from weathering of rock in mountain areas and from higher evaporation leading to higher salinity along the line of ground-water flow. Human activity, in particular large-scale water resources development associated with dramatic population growth in the last 50 years, has led to tremendous changes in the ground-water regime. Recharge has been reduced by 50% and ground-water abstraction exceeds recharge by 0.41×109 m3 yr−1. Consequently, the ground-water level has fallen widely by between 3 and 5 m, with a maximum fall of 35 m in several towns. These hydrological changes have resulted in a serious degradation of the ecosystem. It is suggested that modernized irrigation technology and new regulation to cover water resources management and allocation within the river basin are urgently needed to achieve sustainable development.