Abstract
Abstract. The Yangtze River basin is home to more than 400 million people and contributes to nearly half of China's food production. Therefore, planning for climate change impacts on water resource 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 general circulation models – GCMs) from the Coupled Model Intercomparison Project Phase 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, large uncertainties in the direction and magnitude of future change in discharge for the Yangtze will remain.
Highlights
The Yangtze River (Fig. 1) is the third longest river in the world (6418 km) and the longest river in Eurasia
The daily discharge has a Nash–Sutcliffe efficiency (NSE) of 0.95 for the calibration period (1996–2000) and 0.92 for the validation period (2001– 2005). These NSE values are considerably higher than the www.hydrol-earth-syst-sci.net/21/1911/2017/
Using 78 climate projections under RCP8.5 from the most recent generation of climate models (CMIP5), the analysis shows that between 1981–2010 and 2041–2070 projections of change to basin annual precipitation vary from −3.6 to +14.8 %, with a multimodel mean of 4.1 %
Summary
The Yangtze (or Chang Jiang) River (Fig. 1) is the third longest river in the world (6418 km) and the longest river in Eurasia. Industry and agriculture within the Yangtze River basin generates 30–40 % of China’s GDP and the Yangtze River basin contributes nearly half of China’s crop production, including more than two-thirds of the total volume of rice (Yang et al, 2005). The Yangtze River has been responsible for some of China’s worst natural disasters. Catastrophic floods occurring over the last century include events in 1911, 1931, 1935 and 1954, which claimed the lives of over 300 000 people. As recently as 1998, flooding of the Yangtze River caused over 4000 deaths, inundated 250 000 km of agricultural land and cost in excess of USD 36 billion in damage to property and infrastructure (Yin and Li, 2001)
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