Location: Dale Bumpers Small Farms Research CenterTitle: Soil systems for upscaling saturated hydraulic conductivity (Ksat) for hydrological modeling in the critical zone Author
|Libohova, Zamir - Natural Resources Conservation Service (NRCS, USDA)|
|Schoenberger, Phil - Natural Resources Conservation Service (NRCS, USDA)|
|Bowling, Laura - Purdue University|
|Wysocki, Doug - Natural Resources Conservation Service (NRCS, USDA)|
|Wills, Skye - Natural Resources Conservation Service (NRCS, USDA)|
|Williams, Candiss - Natural Resources Conservation Service (NRCS, USDA)|
|Seybold, Cathy - Natural Resources Conservation Service (NRCS, USDA)|
Submitted to: Vadose Zone Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/6/2017
Publication Date: 4/12/2018
Citation: Libohova, Z., Schoenberger, P., Bowling, L., Owens, P.R., Wysocki, D., Wills, S., Williams, C., Seybold, C. 2018. Soil systems for upscaling saturated hydraulic conductivity (Ksat) for hydrological modeling in the critical zone. Vadose Zone Journal. https://doi.org/10.2136/vzj2017.03.0051.
DOI: https://doi.org/10.2136/vzj2017.03.0051 Interpretive Summary: Water movement into and through soils is an important property for understanding soil function with respect to water dynamics. Soil water movement is commonly evaluated by examining boreholes and measuring how water moves from the borehole into the soil. Understanding water movement in the larger landscape is more difficult and using the borehole measurements can introduce errors when predicting water behavior across landscapes. This research evaluated multiple measurements and observations to determine water movement on the landscape scale. Considering the landscape and landscape attributes when evaluating the soil water movement greatly improved the understanding and usefulness of multiple types of soil water measurements and predictions. Understanding water movement helps hydrologists and land managers make informed decisions for best land use management.
Technical Abstract: Successful hydrological model predictions depend on appropriate framing of scale and the spatial-temporal accuracy of input parameters describing soil hydraulic properties. Saturated soil hydraulic conductivity (Ksat) is one of the most important properties influencing water movement through soil under saturated conditions, and one of the most expensive to measure and highly variable. The objectives of this research were to: (i) assess the ability of Amoozemeters, wells, piezometers, and flumes to accurately represent Ksat at a small catchment scale; and (ii) extrapolate Ksat to a larger watershed based on available soil data and soil landscape models for simulating streamflow using the Distributed Hydrological Soil Vegetation Model (DHSVM). The mean Ksat between Amoozemeters, wells, and flumes varied from 2.4 to 4.9e-07 m sec-1, and differences were not significant. Mixed trends in mean Ksat for slope positions and soil series were observed. The strongest significant and consistent trend in mean Ksat was observed for soil depth. The mean Ksat decreased exponentially with depth, from 6.51e-06 m sec-1 for upper horizons to 2.37e-07 m sec-1 for bottom horizons. Recognizing the significantly decreasing trend of Ksat with soil depth and lack of consistent trends between soils and slope positions for small catchments, Ksat values were extrapolated from the small catchments occurring in Dillon Creek to another large watershed (Hall Creek) based on soil similarity and distribution. The Nash-Sutcliffe (N-S) model overall efficiency of 0.52 indicated a good performance in simulating streamflows without model calibration. Combining Ksat measurement methods in small catchments with an understanding of soil landscapes and soil distribution relationships allowed for successful upscaling of localized soil hydraulic properties for streamflow predictions to larger watersheds.