A global data analysis of sediment and organic carbon loadings to rivers at catchment scale

Although soil erosion could have significant impacts on the global carbon cycle and the well being of aquatic and marine ecosystems, few earth system models include process-based representations of the transport of sediments and particulate organic carbon from land to rivers and streams. Two critical challenges hindering the development of such representations are scale and heterogeneity. More specifically, different processes may dominant soil erosion at different temporal and spatial scales so knowledge derived from low frequency plot scale measurements might not shed lights on soil erosion modeling for coarse-scale earth system models. Also, catchments in different climatic or geologic zones can respond very differently to similar hydrological states. To identify the key processes for parameterizations in coarse-scale soil erosion models, we analyzed the observed sediment and particulate organic carbon fluxes from a large number of catchments across the globe. By comparing the spatio-temporal variations of the fluxes and environmental factors, we found that both soil erosion and deposition processes are important for simulating the effective transport of sediments and organic carbon into rivers. From these flux measurements, we also investigated whether the rainfall intensity threshold triggering large sediment transport could vary substantially across the catchments and estimated the risk of catchment soil loss to climate change based on its sensitivity to environmental factors.