A Catchment‐Based Global Model of River Discharge and Flow Velocity for Earth System Models

Abstract

The representation of river flows in Earth System Models (ESMs) is crucial for understanding water resources availability, contaminant transport, and the impacts of climate change on river systems. In this study, we introduce a global runoff routing model founded on hydraulic geometry principles and hydrologic catchments, specifically designed for integration with ESMs. To simulate river dynamics, the model capitalizes on (a) the river network topology defined by the Pfafstetter coding system, (b) hydraulic geometry principles that connect river discharge to flow velocity, and (c) calibration using more than 2.7 million intermittent field measurements of flow velocity in the contiguous US (CONUS). The model is shown to produce reasonably accurate natural daily river discharge over CONUS except within some arid regions and the region adjacent to the Great Lakes, where streamflow is strongly impacted by reservoir management and by the natural buffering behavior of the large lakes themselves. The average correlation coefficient for discharge (vs. in situ measurements) is 0.80 for tested major rivers over CONUS except in arid regions and the Great Lakes. A unique feature of the model is its ability to simulate flow velocity with realistic magnitudes, standing it in good stead for tracer tracking and water management applications.