The impacts of human activity on hydrological processes in the arid zones of the Hexi Corridor, northwest China, in the past 50 years

摘要

The Hexi Corridor, like other arid zones in northwest China, is characterized by alternating high mountains and plains. The mountain areas have abundant precipitation and glaciers that provide surface water flow to the plains and form numerous inland river systems. The hydrological regimes of the groundwater and springs, to a large extent, depend on the surface runoff. The regional hydrology and ecosystems of the Hexi Corridor region have changed over the last half century under the driving force of intense human activity. This paper aims to show the characteristics of hydrological changes resulting from human activities in the last 50 years from several points of view, such as: surface runoff changes at the mountain front and in the lower reaches of streams, both annual and inter-annual, the changes of the groundwater table and spring water volume, and temporal and spatial hydro-chemical regimes. Streamflow issuing from mountains in the eastern section of the Corridor by way of the Shiyang River has decreased significantly. Annual mountain outflow from the Heihe and Shule rivers in the central and western portions of the Corridor, respectively, have tended to increase. However, river discharge in the lower reaches is decreasing, terminal lakes are contracting or drying up and water quality is getting worse due to expanding large-scale exploitation of water resources. Many small rivers disappear soon after flowing from mountain valleys, river courses are shortening, the spring water volume is continually reducing, and the groundwater table is falling in most parts of the middle and lower reaches. These hydrological changes exacerbate the water supply-demand paradox, and result in serious environmental problems. Understanding the characteristics of hydrological processes and regime change is important for driving the solutions to rational use of the limited water resources and the limiting of environmental degradation in the northwest China.