HILL SLOPE SCALE MODEL OF THE VADOSE ZONE AT KONZA PRAIRIE

The spatial scaling of vadose zone hydrologic data from point measurements to a hill slope or watershed is especially difficult due to the heterogeneity of soil hydraulic properties. A hill slope model of the soil water profile at Konza Prairie, a long-term ecological research station, will combine data from multiple scales to create a vadose zone hydrologic model. Understanding of the soil water profile of the vadose zone is important for the interactions between surface processes of infiltration and runoff, the subsurface processes of lateral flow and groundwater recharge, the available water stored in the root zone, and contaminant transport. Using unsaturated flow equations, a hill slope scale model of the soil water profile will be created from infiltration rates, groundwater recharge rates, and soil hydraulic properties. The unsaturated soil hydraulic properties were measured with automated mini-disk infiltrometers at the surface and at depths of 60 cm at ten sites along a hill slope in Konza Prairie. The soil hydraulic properties are used to form a steady flow model of the unsaturated zone on a hill slope. The results will show how water flows vertically through soil layers to become groundwater and laterally to form seeps and springs. The model will aid in the further development of a comprehensive hydrologic model of Konza Prairie. The results will show the importance of lateral flow in seepage erosion. By studying and modeling the soil water profile at a location like Konza Prairie, we can determine what the predevelopment soil water flux is in Kansas. The result at Konza Prairie can be compared to post-development conditions in urban or agricultural land uses. The vadose zone is a critical component to the hydrologic cycle, controlling the pathway for groundwater recharge, available water for plant roots, and erosion and deposition processes.