Climate Change Impacts on Inflow and Hydropower Generation in Three Gorges Reservoir

The impact of climate change on the water cycle is likely to affect the hydropower plant as far as the regional electric system. Using the Soil and Water Assessment Tool (SWAT), integrated with a statistic hydropower model, this study examines the impacts of climate change on the reservoir filling and hydropower generation of the Three Gorges Reservoir (TGR), which is the largest hydroelectric construction in the world. ArcSWAT2012 was used to develop a model for simulating the river inflow to TGR. The model parameters were calibrated and validated based on climate dataset derived from Water and Global Change Program. Based on a subset of five General Circulation Models (GCMs) under three Representative Concentration Pathways (RCPs), we simulated the climate change impact on river inflow to TGR during 2006-2099. Combining the daily reservoir operation, a statistic hydropower model was forced by the simulated river inflow to estimate the changes in hydropower generation during three time slides: future early-century (2016–2035), mid-century (2046–2065) and end-century (2080–2099) by comparing with that of the ‘present day’ (1986–2005). Results show that, the simulated mean annual inflow, extreme high(Q5) and low flow(Q95) are slightly lower than that of present day in the early 21st century, but gradually increase to higher than the current after which. This led to substantial changes in TGR impoundment, with the estimated full storage rate higher than that of current during the whole 21st century under RCP2.6, while higher than that of current only after the middle 21st century under RCP4.5 and RCP8.5. The estimated mean storage level will be higher than that of present day till the end of 21st century under RCP4.5 and RCP8.5, however, the estimated mean first full storage day will be earlier under all RCPs for all three time slides. The simulated mean annual hydropower generation has a slight decline in the early 21st century, but increase than that of present since the mid-century. Although the simulated river inflow will generally increase after the mid-century, the increased inter-annual variation, changes in monthly runoff magnitude, which imply an increase in simulated frequency and intensity of extreme stream flow, will decrease the stability of the TGR impoundment and hydropower generation. These findings indicate the complexity of hydropower management and production under future climate change scenarios, and call for the introduction of a true integrated and adaptive approach.