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The impact of the Three Gorges Dam on summer streamflow in the Yangtze River Basin |
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| Authors: | Zhenkuan Su Michelle Ho Zhenchun Hao Upmanu Lall Xun Sun Xi Chen Longzeng Yan |
| Institution: | 1. State Key Laboratory of Hydrology-Water Resources and Hydraulic Engineering, Hohai University, Nanjing, China;2. Columbia Water Center, Columbia University, New York, New York
CSIRO Land and Water, Canberra, ACT, Australia;3. Columbia Water Center, Columbia University, New York, New York Department of Earth and Environmental Engineering, Columbia University, New York, New York;4. Columbia Water Center, Columbia University, New York, New York Key Laboratory of Geographic Information Science (Ministry of Education), East China Normal University, Shanghai, China;5. Bureau of Hydrology, Changjiang Water Resources Commission, Wuhan, China;6. Upper Changjiang River Bureau of Hydrology and Water Resources Survey, Bureau of Hydrology, Changjiang Water Resources Commission, Chongqing, China |
| Abstract: | The Three Gorges Dam is the world's largest capacity hydropower station located in the Hubei province along the Yangtze River in China, which began operations in 2003. The dam also functions to store and regulate the downstream releases of water in order to provide flood control and navigational support in addition to hydropower generation. Flow regulation is particularly important for alleviating the impacts of low- and high-flow events during the summer rainy season (June, July, and August). The impact of dam operations on summer flows is the focus of this work. Naturalized flows are modelled using a canonical correlation analysis and covariates of subbasin-scale precipitation resulting in good model skill with an average correlation of 0.92. The model is then used to estimate natural flows in the period after dam operation. A comparison between modelled and gauged streamflow post 2003 is made and the impact of the dam on downstream flow is assessed. Streamflow variability is found to be strongly related to rainfall variability. An analysis of regional streamflow variability across the Yangtze River Basin showed a mode of spatially negatively correlated variability between the upper and lower basin areas. The Three Gorges Dam likely mitigated the occurrence of high-flow events at Yichang station located near the dam. However, the high flow at the remaining stations in the lower reach is not noticeably alleviated due to the diminishing influence of the dam on distant downstream flows and the impact of the lakes downstream of the dam that act to attenuate flows. Three types of flow regime changes between naturalized and observed flows were defined and used to assess the changes in the occurrence of high- and low-flow events resulting from dam operations. |
| Keywords: | canonical correlation analysis high flow low flow Three Gorges Dam |