WBMsed, a distributed global-scale riverine sediment flux model: Model description and validation

Quantifying continental sediment flux is a fundamental goal of earth-system science. Ongoing measurements of riverine-suspended sediment fluxes to the oceans are limited (<10% of rivers) and intrabasin measurements are even scarcer. Numerical models provide a useful bridge to this measurement gap and offer insight to past and future trends in response to human and environmental changes. BQART is a global empirical model that calculates long-term suspended sediment loads. The Psi statistical model accounts for intra- and interannual variability in these BQART sediment flux predictions. Here BQART and Psi are compiled as a new module of the WBMplus global daily water balance/transport model, a central component in the FrAMES hydrological–biogeochemical modeling scheme. The resulting model (WBMsed) simulates spatially and temporally explicit (pixel scale and daily) sediment fluxes over continental Earth. We test WBMsed predictions with (1) observed sediment loads at 95 river mouths and to the original BQART predictions for these rivers, and (2) 11 years of daily sediment flux observations of 11 USGS stations. The results show that WBMsed captures the multiyear average, interannual and intraannual trends but considerably over- and underpredict daily fluxes for extreme discharge periods. These over- and underpredictions are mainly driven by respective mispredictions of water discharge fluxes. Future improvements to WBMsed to address these limitations are provided.