Impact of runoff schemes on global flow discharge: A comprehensive analysis using the Noah-MP and CaMa-Flood models

This study examines seven common runoff schemes within the widely used Noah-Multi-parameterisation (Noah-MP) land surface model (LSM) and evaluates their performance using ERA5-Land runoff data as a benchmark for assessing runoff and in situ streamflow observations for evaluating discharge across the globe.

Then, to assess the sensitivity of global river discharge to runoff, we simulate the discharge using the Catchment-based Macro-scale Floodplain (CaMa-Flood) model across various climatic regions. The results indicate significant variability in the accuracy of the runoff schemes, with model experiments that use TOPMODEL-based runoff schemes, which are based on topography, underestimating runoff across many regions, particularly in the Northern Hemisphere, while experiments using the other runoff schemes, including default Schaake free-drainage scheme from Noah, BATS (Biosphere–Atmosphere Transfer Scheme), Variable Infiltration Capacity (VIC) scheme, and Xinanjiang scheme (XAJ), showed improved performance.