Effects of damming and climatic change on the eco-hydrological system: A case study in the Yalong River, southwest China

The eco-hydrological system in China is undergoing dramatic changes in recent decades due to climate change and construction of cascade dams for power production. Given that multiple drivers often interact in complex and nonadditive ways, the purpose of this study is to predict future changes in runoff and fish habitat quality of the Yalong River basin attributed to the individual and combined effects of cascade dam construction and climate change. The bias corrected and spatially downscaled CMIP5 GCM projections are used to drive the Soil and Water Assessment Tool hydrological model and to simulate and predict runoff responses under diverse scenarios. The physical habitat simulation model is established to describe the relationship between river hydrology and fish habitat quality and to assess the individual and combined effects of cascade dam construction and climate change. The mean annual temperature and precipitation of the Yalong River in 2020-2100 are predicted to increase at a rate of 0.016-0.487 degrees C/10a and 4.55-10.13 mm/10a, with an increase of 1.63-3.25 degrees C and 0.66-3.34% in comparison with those in 1957-2012, respectively. While, the mean annual runoff of the middle and lower reaches is increased by 11.77%-16.63% and 14.02%-19.02% compared with that in the history, respectively. The construction of cascade dams could significantly improve the fish habitat quality of the Yalong River basin, especially in dry seasons, and consequently the ecological conservation degree is increased by about 2%. In the middle reaches, changes in runoff from February to October are mainly determined by cascade dam construction, but the effect of climate change becomes more pronounced from November to January. Similarly, cascade dam construction has a more significant effect on runoff of the lower reaches than climate change except in November and December.