Application of Loosely Coupled Watershed Model and Channel Model in Yellow River, China

Abstract

Insufficient flow and excessive sediment supply in the Middle Yellow River lead to persistent sedimentation and rising flood levels in the lower river channel. Better understanding of the relationship between sediment erosion, transportation, and deposition can help in the decision making of soil and water conservation in the Coarse Sediment Source Area (CSSA) and sediment reduction works in the lower channel. A linked simulation can help elucidate the interrelationship. The goal of the current research is to simulate the whole sediment process from the CSSA to the downstream channels of the Yellow River. To achieve this goal, we use the Digital Yellow River Model (DYRM), a watershed hydrology and sediment yield and transportation model plate, coupled with a one-dimensional (1D) unsteady model for the hyper-concentrated sediment-laden flow in complex sections, to study the sedimentation process in the entire watershed. The performance of the simulation of flood in year 1977 was evaluated using the percent bias, Nash-Sutcliffe statistics of the residuals, and percentage difference. Simulation of the sediment process in 1977 shows that linked simulation can describe the hydrographs of discharge and sediment concentrations, especially flood in the downstream main channels. Compared with the underestimated discharge and sediment load in the main channel, the discharge of most tributaries is overestimated, whereas most of the sediment load is underestimated. The inconsistency indicates that more efforts are required to conduct better simulation, including data input and data processing, and both DYRM and 1D models.

Keywords: linked simulation, Digital Yellow River Model, one-dimensional unsteady model, Yellow River