Geospatial modeling method to provide estimates of POC flux for regional-scale watersheds

The transport of particulate organic carbon associated with fine sediments has been shown to account for 10 to 80 of the total carbon flux in rivers; however variability is high requiring further estimates of POC for different watershed systems. The objective of this research was to establish a new geospatial modeling method to provide estimates of POC flux at regional scales for temperate climate, lowland watersheds with agricultural and urban land-uses. The geospatial method relies on integration of sediment loading estimates published by the USGS and soil organic carbon estimates published by the USDA-NRCS. The modeling method accounts for the content of carbon at the soil erosion sources as well as carbon enrichment or losses during soil erosion. The modeling method makes use of a finer scale sediment and carbon transport model for a representative sub-watershed, i.e., third order stream, in order to account for variation of POC transport processes including seasonal and hydrologic variation. Specifically, the modeling method is applied here for the Inner Bluegrass Region of the Kentucky River Basin in Kentucky USA. Sediment and carbon modeling generated an average POC flux value of 1.5 tC km^-2 yr^-1. Likewise, initial geospatial modeling generated an estimate of 0.055-159 tC km^-2 yr^-1, with the high variability attributed to the range of sediment loading estimates from the USGS model and variability in the POC sources in the watershed.