Impact of upstream reservoirs on geomorphic evolution in the middle and lower reaches of the Yangtze River. Issue 3 (14th November 2022)

• Record Type: Journal Article
• Authors: Yang, Yunping; Zhou, Liangping; Zhu, Lingling; Liu, Wanli; Wang, Jianjun
• Is Part Of: Earth surface processes and landforms. Volume 48:Issue 3(2023)
• Page Start: 582
• Page End: 595
• Publication Date: 2022-11-14
• Subjects: human activity -- hydrological–morphological system -- river erosion -- Three Gorges Project -- trend analysis; Geomorphology -- Periodicals; 551.4
• DOI: 10.1002/esp.5504
• Languages: English
• ISSNs: 0197-9337

Abstract

Abstract: Intensive human activities in river basins have substantial effects on fluvial hydrological and morphological processes and developmental trends. In this study, we assessed the evolutionary characteristics and developmental trends of the fluvial morphological system of the Three Gorges Dam (TGD) downstream to understand the impacts of human activities on the fluvial hydrological–morphological system of the region. The results indicated that the Three Gorges Project (TGP) and other upstream cascade reservoirs promoted sediment retention, which in turn aggravated the trend of declining sediment load and cumulative scouring over a long distance in the channels downstream of the TGD. Approximately 84% of scouring occurred in the low‐water channels, along with thalweg scouring and riverbank collapse. Notably, extended operation of the TGP and other upstream cascade reservoirs has resulted in gradual changes in the downstream riverbeds. Specifically, we found that the most intensive scouring zone shifted downstream from the near‐dam Yichang–Chenglingji reach (0–408 km) to the Chenglingji–Hankou reach. The scouring–silting distribution in swales has also changed: the scouring of deep swales and silting on floodplains prior to the TGP have been replaced by the scouring of both deep swales and floodplains. The scouring intensity of riverbeds in the Yichang–Hukou reach (954 km) was slightly higher than that forecasted prior to the TGP; the scouring intensities increased significantly during 2013–2021, which could be attributed to the TGP and other upstream cascade reservoirs; river sand mining and waterway dredging are secondary factors. We conclude that, owing to the effects of sediment retention by cascade reservoirs in the upper reaches of the Yangtze River (or Changjiang River), the cumulative scouring intensities of riverbeds in the middle and lower reaches of the Yangtze River will continue to increase in future decades. Abstract : Distribution of hydropower stations along the upper reaches of the Yangtze River.Highlights The Three Gorges Dam has altered the conditions and trends in downstream channels. Riverbed morphology has changed to adapt to the water–sediment conditions. Intensive scouring occurred in the middle reaches of the Yangtze River. Riverbed scouring downstream of the dam will continue to intensify. Measured scouring–silting intensity was higher than predicted before dam operation.