Adaptive operation of reservoirs in the Lower reaches of Jinsha River at the dry season under climate change

             Reservoir operation is important to realize the coordination of social, economic and environmental systems. However, climate events have changed the water cycle process and the spatial-temporal distribution of the water resource system, which has brought new challenges to regional water resources management and reservoir operation. This study aims at analyzing the impacts of climate change on the multi-objective reservoir operation at the dry season, and the adaptive reservoir operation scheme for future climate change scenarios. The Jinsha River, at the upper reaches of the Yangtze River, was chosen as the research area because a large number of reservoirs have been built in the basin. Firstly, the Pettitt, MK and Moving t-test methods were used to identify the abrupt points of the hydro-meteorological data series from 1957 to 2018, and then the SWAT model was used to quantify the impacts of climate change on the runoff in the Jinsha River. Secondary, the multi-objective optimal operation model of cascade reservoirs was constructed, and then an improved PA-DDS method is developed to find the Pareto front between ecological protection and power generation. Thirdly, the impacts of climate change on reservoir operation were analyzed by comparing the scheduling results between the pre-change period (1957-1996) and the post-change period (1997-2018). Finally, using the Delta downscaling method, the GCM models chosen by suitability assessment were inputted into the SWAT model to simulate the future runoff for the reservoir operation model under different scenarios. The results showed that (1) the temperature and precipitation in the Jinsha River faced an abrupt change in 1997, while the runoff changed in 1997 and 2004. (2) the SWAT model can well simulate the daily runoff of Jinsha River (Re<15%, NSE>0.79, R²>0.8), while climate change accounts for 52.4% and 52.1% of runoff change during 1997-2004 and 2005-2018, respectively. (3) climate change can increase the ecological deviation degree and the power generation of reservoirs. In addition, compared with the traditional optimal scheduling scheme, the potential climate change brings higher requirements for water resources optimization in the future. (4) From 2021 to 2100, the temperature, precipitation and runoff of the Jinsha River are continually increased compared with the pre-changed period. It should be noted that the runoff from September and October is significantly reduced in most scenarios, increasing the insufficient storage risk of cascade reservoirs; man-made floods may be caused by the increasing runoff from April to June and the concentrated discharge of reservoirs before flood season. This study can provide theoretical support for reservoir operation and provide technical references for the impact mechanism of climate change on water resources and their management.