2.1 Study area
The Qilian Mountains form a huge marginal mountain range in the northeastern section of the Qinghai-Tibet Plateau (94°E~104°E, 36°N~39°N). The Shiyang, Heihe, and Shule Rivers which originated on the north slope of the Qilian Mountains, are the three inland rivers of the Hexi Corridor. The surface water resources in the upper reaches of the Shiyang River are characterized by unequal distribution annually The Qilian Mountains are the main runoff areas for inland rivers (Fig. 1). In recent years, reservoirs have been built near the exit of each tributary, including the Xiying Reservoir, the Nanying Reservoir, the Huangyang Reservoir and so forth (Fig. 1). The existence of reservoirs in the eastern section of the Qilian Mountains and the stability of their water volume have a direct impact on the industrial and agricultural production and the improvement of ecological conditions for the Wuwei and Minqing Oasises the Minqing Oasis being one of the oases with the largest ecological function in the eastern section of the Hexi Corridor.
The Xiying Reservoir is an important and typical reservoir in the region which has irrigation as its main function and plays an important role in flood control and power generation. The total storage capacity is 2.35×107 m3, and the effective irrigation area is 252.33 km2.
Figure 1. Location of the research area