Variation of the runoff in the upper and middle reaches of the main Heihe River and its causes
CHENG Jianzhong;LU Zhixiang;ZOU Songbing;CHENG Wenjia;Zhangye Hydrology and Water Resources Survey Bureau of Gansu Province;Key Laboratory of Ecohydrology of Inland River Basin,Northwest Institute of Eco-Environment and Resources,Chinese Academy of Sciences;
The interannual variability,annual distribution and variation of the runoff in the upper and middle reaches of the main Heihe River and their reasons are analyzed based on the measured hydrological and meteorological data,together with the groundwater level data in in the midstream. The results show that the runoff in the upper reaches of the river has slightly increased since 1945 as a whole,and the month with the maximum runoff has shifted from July to August since the beginning of the 21~(st) century,which was mainly controlled by the precipitation.The runoffs at Gaoya and Zhengyixia Stations have increased slightly since 1977 with the rates of 1. 7million m~3 and 10. 2 million m~3 per year,respectively. The water consumption in the section from Yingluoxia to Gaoya have increased at the rate of 8. 5 million m~3 per year due to the social and economic development; the amount of the irrigation return water and groundwater recharging to the river have been almost the same as the irrigation water diversion and other water consumption in the section from Gaoya to Zhengyixia. Excessive exploitation of groundwater have slowed down water consumption pressure in Heihe River basin to a certain extent,but it was bad to the sustainable utilization of water resources. This results will be helpful for scientific allocation and reasonable regulation of water resources in the Heihe River basin.