Estimating the sediment trap efficiency and lifespan of cascaded reservoirs in the Upper Yangtze River Basin, China.

Abstract: The cascaded reservoirs in the Upper Yangtze River Basin (UYRB) are subject to sediment inflow and deposition, resulting in reduction in their effective capacity. The sediment trap efficiency (TE) of the cascaded reservoirs was estimated using several empirical methods, and the factors affecting the TE also were analysed. A new empirical formula was obtained to calculate the TE of the small reservoirs (storage capacity C < 0.5 km3) in the UYRB. Further, four zones were partitioned to describe the relationship between the sediment trap effect and the service function of the reservoirs. The TEs of Xiluodu, Xiangjiaba and Ertan Reservoirs in the UYRB were investigated and compared between stand‐alone and combined operation modes, indicating the TE will be underestimated without considering the cumulative sediment trap of the cascaded reservoirs. Finally, the lifespan of the Xiluodu Reservoir, considering different water storage schemes and different capacity loss percentages, was estimated using the TE method and exhibited good agreement with the results calculated by the mathematical model. The derived TE calculation method under the combined operation of the cascaded reservoirs can be used to assess the sediment trap from the complex hydroelectric project system in the UYRB. [ABSTRACT FROM AUTHOR]