Numerical evaluation of the effects of the Dongzhuang reservoir on channel deposition in the Lower Wei River in China

Jing River is a tributary of the Wei River which is the largest tributary of the Yellow River. Sediments eroded from the upland of the Jing River basin are one of the major contributors of sediment entering the lower Wei River (LWR). The Dongzhuang reservoir is designed to be constructed on the lower Jing River for flood control and water resources regulation, and this may change the sustainable management of the LWR as changed channel deposition by trapping sediments and releasing concentration-limited flow. Its effects on the LWR, especially the deposition distribution, should be analyzed. The steady quasi-two-dimensional dynamic model was adopted to estimate the deposition processes in the LWR. Then, the qualitative effects of the Dongzhuang reservoir on channel deposition were evaluated and compared with historical data, including capacity loss in other reservoirs and measured deposition in the LWR. Analyses indicated that the annual deposition in the LWR will decrease by approximately two-thirds due to the reservoir’s operation. After 15 years of operation, the effects of the Dongzhuang reservoir on the lower channel will decrease gradually. Moreover, its effects on lateral distribution in different sub-reaches are different. After the reservoir’s operation, the floodplain of the Xianyang-Lintong (XY-LT) sub-reach will change its sediment regime from deposition to erosion. For the Lintong-Huaxian (LT-HX) sub-reach, deposition in the main channel will be more serious during the first 30 years of operation. For the Huaxian-Tongguan (HX-TG) sub-reach, the reservoir will have almost no effects on the lateral distribution. All these analyses may benefit the sustainable management of the Wei River and the Yellow River.