Cumulative Effect of Cascade Hydropower Development on Water Quantity Process in the Upper Wu River of Western China

The Wu River Basin in western China is experiencing extensive hydropower development. Concerns have been raised about the consequences of the development for the ecological environment. In this paper, we assess the cumulative effect of six hydropower stations on water quantity process in the upper Wu River by using a combination of measured data and a distributed hydrological model based on MIKE11. The results show that the operation of hydropower stations averaged the runoff distribution that increased the November-April discharge by 10-176% and decreased the May-October discharge by 6-38%. Furthermore, the effect of averaging runoff distribution would be more obvious along with the adjustment of hydropower cascade stations due to cumulative effect, the differential ratio of mean discharge in flood season and dry season decreased from 79.3% to 20.4% along with the hydropower stations. Thus the water quantity process in the upper Wu River has been significantly altered by cascade hydropower development, but what the consequences are for the ecological environment, needs further study.