Climate Change Impacts on Yangtze River Discharge at the Three Gorges Dam
Steve J. Birkinshaw1, Selma B. Guerreiro1, Alex Nicholson2, Qiuhua Liang1, Paul Quinn1, Lili Zhang3, Bin He4, Junxian Yin3, and Hayley J. Fowler11School of Civil Engineering and Geosciences, Newcastle University, Newcastle NE1 7RU, UK 2Ove Arup and Partners, Admiral House, 78 East St., Leeds, UK 3State Key Laboratory of Simulation and Regulation of Water Cycle in River Bain, China Institute of Water Resources and Hydropower Research, Beijing, 100038, China 4School of Hydraulic Engineering, Dalian University of Technology, Dalian, P. R. China
Received: 13 May 2016 – Accepted for review: 19 May 2016 – Discussion started: 23 May 2016
Abstract. The Yangtze River Basin is home to more than 400 million people, contributes to nearly half of China’s food production, and is susceptible to major floods. Therefore planning for climate change impacts on river discharges is essential. We used a physically-based distributed hydrological model, Shetran, to simulate discharge in the Yangtze River just below the Three Gorges Dam at Yichang (1,007,200 km2), obtaining an excellent match between simulated and measured daily discharge, with Nash-Sutcliffe efficiencies of 0.95 for the calibration period (1996–2000) and 0.92 for the validation period (2001–2005). We then used a simple monthly delta change approach for 78 climate model projections (35 different GCMs) from the Coupled Model Intercomparison Project-5 (CMIP5) to examine the effect of climate change on river discharge for 2041–2070 for Representative Concentration Pathway 8.5. Projected changes to the basin’s annual precipitation varied between −3.6 % and +14.8 % but increases in temperature and consequently evapotranspiration (calculated using the Thornthwaite equation) were projected by all CMIP5 models, resulting in projected changes in the basin’s annual discharge from −29.8 % to +16.0 %. These large differences were mainly due to the predicted expansion of the summer monsoon north and west into the Yangtze basin in some CMIP5 models, e.g. CanESM2, but not in others, e.g. CSIRO-Mk3-6-0. This was despite both models being able to simulate current climate well. Until projections of the strength and location of the monsoon under a future climate improve there will remain large uncertainties in the direction and magnitude of future change in discharge for the Yangtze.
Birkinshaw, S. J., Guerreiro, S. B., Nicholson, A., Liang, Q., Quinn, P., Zhang, L., He, B., Yin, J., and Fowler, H. J.: Climate Change Impacts on Yangtze River Discharge at the Three Gorges Dam, Hydrol. Earth Syst. Sci. Discuss., doi:10.5194/hess-2016-231, in review, 2016.