The impact of the Three Gorges Dam on summer streamflow in the Yangtze River Basin

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. K E Y W O R D S canonical correlation analysis, high flow, low flow, Three Gorges Dam

The Operation of the Three Gorges Dam Alters Wetlands in the Middle and Lower Reaches of the Yangtze River

“…The relative stable status in floodplains and water surface areas between Chenglingji and Hukou may be the consequences of water and sediments dynamics of mainstream Yangtze and Dongting Lake, such stable status may continue for a period of time depending the speed of river bed erosion of the lower part of Y-C section. Siltation at H-N section remains similar to the period before the operation of the TGD, which is a continue processes and combination of Poyang Lake (Duan, 1993;Li, 2009;Su et al, 2019).…”

Spatio-Temporal Variability in Hydroclimate over the Upper Yangtze River Basin, China

“…The upper catchment contains four major tributaries, i.e., Jinshajiang, Mintuojiang, Jialingjiang and Wujiang, and the main stream of the upper reaches [61]. The climate is characterized by complex regional sub-basin-scale patterns of precipitation and temperature in terrain ranging from plateaus to plains [39]. The watershed climate is mainly influenced by the Indian Summer Monsoon, and the climate is drier and colder at the western end of the upstream [58].…”

“…The monthly averaged flow data were obtained by averaging the daily flow rates within each month. The annual and seasonal series were prepared from monthly datasets, with runoff in monsoon summer (June, July and August) dominated [39]. The runoff data were converted to millimeter units by using the catchment area of Yichang station for subsequent analysis.…”

“…Due to the nonlinear behavior of hydrological processes and the effects of dam construction, it is difficult to adequately relate hydrological changes to climate signals by analyzing observed changes in precipitation and runoff alone, especially for the main stream [61]. The Yichang station is known as Gateway to the Three Gorges and is located approximately 40 km downstream of the dam [39]. Hydraulic structures on rivers, such as the Three Gorges Dam (TGD), can alter the river flow to a large extent [61], signifying changes in precipitation cannot easily be converted into amounts of observed streamflow change.…”

“…With its rich natural resources, diverse economic culture and important location advantages, the Yangtze River Basin (YRB) has occupied an extremely important position in China's social and economic development [38]. The YRB is home to one-third of the country's population, and the largest capacity hydropower project in the world to date is the Three Gorges Dam (TGD) located at the end of the upper reaches [39]. The Yangtze River is extraordinarily vulnerable to climate warming due to its dense population and the rapidly developed economy [33].…”