Water Demand for Sediment Transport in Rivers: Conceptualization and Computational Approaches

Sediment transport water demand provides the critical theoretical foundation for effective watershed management, optimized reservoir operation, and sustaining river ecosystem health. This demand refers to the clear or sediment-laden water volume needed for transporting a specified amount of sediment to a downstream location within a given period, under defined flow-sediment and channel boundary conditions, while preserving a target erosion-deposition balance. This demand is governed by the sediment‑carrying capacity and channel‑forming processes of the river and is modulated by channel geometry, sediment supply dynamics, grain‑size distribution, target erosion‑deposition levels, and temporal scale. It manifests through multi‑factor coupling, spatiotemporal variability, scale dependency, and functional orientation. A range of methods have been developed to calculate this demand, including the definition method, the equilibrium sediment transport method, data‑based analysis, erosion‑deposition correction, energy balance, and non‑equilibrium sediment transport approaches. Drawing on case studies from the Ningxia-Inner Mongolia reach and the lower Yellow River, this paper examines the key characteristics of sediment transport water demand and compares the applicability of prevailing calculation methods.