An Innovative Equivalent River Channel Method for Integrated Hydrologic–Hydrodynamic Modeling

Abstract. To address the lack of river cross-sectional data in hilly regions, this study proposes a novel method that transforms Muskingum parameters (K and X) into Conceptual Equivalent River Channel (CERC). By integrating linear or nonlinear Muskingum parameters with characteristic discharge, roughness, and other relevant inputs, this approach derives simplified yet hydraulically representative cross-sections. Two types of CERC models are introduced: single-layer and dual-layer. The single-layer CERC model includes rectangular, parabolic and triangular cross-sections, while the double-layer CERC builds upon these with an exponential shape. The proposed method was applied to two river reaches in China: the Chenggouwan–Linqing reach in the Haihe River Basin and the Huayuankou–Jiahetan reach in the Yellow River Basin. Using previously calibrated and validated Muskingum parameters, the resulting channel geometries were incorporated into a one-dimensional (1-D) hydrodynamic model. Results indicated that CERCs accurately replicated observed hydrographs, and the dual-layer approach improved performance in reaches with strong nonlinear characteristics. Furthermore, the model effectively captured changes in water level and flow velocity, confirming the suitability of CERC for hydrodynamic modeling. A sensitivity analysis examined the impact of variations in roughness (n) affected the Conceptual Equivalent River Channel Cross-sections (CERCXs) and discharge outcomes, demonstrating the robustness of the proposed method. While CERCs simplify the natural complexity of river channels, their parametric framework represents the channel’s storage capacity and allows flexible shape selection, enabling accurate simulations of water levels and flow velocities when adjusted to match measured cross-sections. This research provides a practical solution that bridges traditional hydrological and hydrodynamic routing methods in regions with limited data availability, especially in hilly areas.