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Title
Japanese: 
English:Examining the downstream geomorphic impact of a large dam under climate change 
Author
Japanese: Joy SANYAL, J Wesley Lauer, 鼎 信次郎.  
English: Joy SANYAL, J Wesley Lauer, Shinjiro Kanae.  
Language English 
Journal/Book name
Japanese: 
English:CATENA 
Volume, Number, Page Volume 196        104850
Published date Jan. 2021 
Publisher
Japanese: 
English:Elsevier 
Conference name
Japanese: 
English: 
Conference site
Japanese: 
English: 
Official URL https://www.sciencedirect.com/science/article/pii/S0341816220304008
 
DOI https://doi.org/10.1016/j.catena.2020.104850
Abstract Long-term geomorphic evolution of rivers depends both on the amount of sediment supply and on the river’s ability to transport that sediment. Climate change is anticipated to change flow frequency distributions and sediment yield and could thus alter the geomorphic trajectory of many regulated rivers. We aim to examine the possible geomorphic response of the upper Godavari River, India, to climate change using two well-accepted metrics: the frequency of the sediment-transporting flows (T*) and the ratio of the sediment flux below and above a dam (S*). Soil and Water Assessment Tool (SWAT) was used to simulate streamflow and sediment yield in the basin. We calibrated and validated the model using SWAT-CUP for pre- (1971–75) and post-dam (1976–81) conditions downstream of Jayakwadi dam. The model performance was good (NS value > 0.6 for discharge and PBIAS < ± 10 for sediment) with low uncertainty (p-factor > 0.6 and r-factor <1) and it improved significantly by factoring the operation of the reservoirs into the simulation. We ran the model for 10 years consecutively in the pre and post-dam states for baseline (1971–81) and future (2090–99) climate conditions derived from NEX-GDDP climate projections (Emission scenario RCP 8.5 & 4.5). A linear relationship between T*/S* and observed erosion (m) below the dam provided the basis for estimating the amount of erosion associated with future climate states. Our simulations show substantially larger T* below the dam site in 40% of the 2090s scenarios relative to the baseline conditions. These could be associated with 4–6 times the erosion compared to the baseline. Severe erosion is indicated only under RCP 8.5. Simulations suggest that amplified peak releases from dams in the future could lead to greater downstream erosion potential.

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