MOUNTAIN STREAM TYPES IN NORTHWEST CHINA
Yang Zhenniang (Lanzhou Institute of Glaciology and Cryopedology, Academia Sinica)
The mountain streams in the northwestern part of China are supplied by various water sources. According to both their sources and the basic hydrogical characteristics, they may be divided into five types of streams, namely the type of ice and snow meltwater, the type of rain water and ice and snow meltwater, the type of underground water and ice and snow meltwater, the type of snow meltwater, and the type of rain water. In the type of ice and snow meltwater, the ice and snow meltwater is the main supply and the discharge is extremely steady. In the type of rainwater and ice and snow meltwater,the rain water maybe the main supply mixed with ice and snow meltwater and the discharge is quite stable, most streams in the Northwest China belong to this type. The type of underground water and ice and snow meltwater is mainly supplied by under ground water with other mixed sources and the change of the discharge is comparatively big. Both the types of snow meltwater and of the rainfall belong to streams of precipitation supply. However, at present the former is mainly supplied by snow meltwater in spring and the stream discharge is affected directly by precipitation and has the greatest change.