Analysis of Spatial Soil Hydraulic Properties to Investigate Soil-Water Movement and Scaling in an Agricultural Field

The coupled processes of overland flow, infiltration, and multidimensional soil-water flow and storage affect the space-time scaling behavior of measured soil-water content. Previous work on this farm field in eastern Colorado revealed simple scaling behavior in near-surface (0-30 cm) water content, despite generally poor correlation with landscape topographic attributes. In this study, we have analyzed soil hydraulic properties along a transect to help investigate coupled overland-subsurface flow processes and how the scaling behavior of measured and simulated soil-water content may be linked to such processes. Soil cores have been collected and analyzed for textural and hydraulic properties. Detailed analyses include three-step outflow experiments followed by numerical inverse simulations to estimate hydraulic conductivity and storage parameters. Spatial patterns of selected parameters and their correlations with topography will be illustrated. Hourly soil-water data has also been collected with capacitance probes at eight landscape positions and four depths along the undulating transect. The soil-water data suggests that significant lateral flow of soil water occurs at seasonal time scales, despite a lack of obvious impeding layers or perched groundwater. Overland flow also occurs during high-intensity rainfall events. Numerical simulation results of the coupled hydrologic processes may provide further insights into causative links with soil-water scaling.