Abstract
Improving understanding of dissolved organic carbon (DOC) cycling from farmlands to rivers is a challenge due to the complex influence of farming practices, the hydrology of predominantly flat lowlands, and seasonal snowpack effects. Monthly field DOC concentrations were measured throughout the year at sub-basin scale across the Chippewa River Watershed, which falls within the Corn Belt of the Midwestern United States. The observations from croplands were benchmarked against the data sampled from hilly forested areas in the Connecticut River Watershed. The Soil Water Assessment Tool (SWAT) was used to simulate daily soil water properties. This method tests for a framework for using the combination of new field data, hydrological modelling, and knowledge-based reclassification of Land Use/Land Cover (LULC) to analyze the predictors of both the spatial and temporal changes of DOC over farmlands. Our results show: 1) DOC concentrations from cropland baseflow were substantially high throughout the year, especially for spring runoff/snowmelt scenarios, 2) gradient analysis with spatial factors only was able to explain ~82% of observed annual mean DOC concentrations, and 3) with both spatial and temporal factors: [Evapotranspiration, Soil Water, and Ground Water], the analysis explained ~81% of seasonal and ~54% of daily variations in observed DOC concentrations.
Factors Driving the Spatiotemporal Variation of Dissolved Organic Carbon Flux from Croplands in the Midwestern USA
