Hydrology and Earth System Sciences www.hydrol-earth-syst-sci.net 1027-5606 1607-7938 13 4 2009 10.5194/hess-13-453-2009 http://www.hydrol-earth-syst-sci.net/13/453/2009/ http://www.hydrol-earth-syst-sci.net/13/453/2009/hess-13-453-2009.html http://www.hydrol-earth-syst-sci.net/13/453/2009/hess-13-453-2009.pdf 453 465 2009-04-07 An alternative deterministic method for the spatial interpolation of water retention parameters H. Saito hiros@cc.tuat.ac.jp K. Seki J. Šimůnek Department of Ecoregion Science, Tokyo University of Agriculture and Technology, Fuchu, Tokyo 183-8509, Japan Faculty of Business Administration, Toyo University, Tokyo 112-8606, Japan Department of Environmental Sciences, University of California, Riverside, CA 92521, USA There are two approaches available for mapping water retention parameters over the study area using a spatial interpolation method. (1) Retention models can be first fitted to retention curves available at sampling locations prior to interpolating model parameters over the study area (the FI approach). (2) Retention data points can first be interpolated over the study area before retention model parameters are fitted (the IF approach). The current study compares the performance of these two approaches in representing the spatial distribution of water retention curves. Standard geostatistical interpolation methods, i.e., ordinary kriging and indicator kriging, were used. The data used in this study were obtained from the Las Cruces trench site database, which contains water retention data for 448 soil samples. Three standard water retention models, i.e., Brooks and Corey (BC), van Genuchten (VG), and Kosugi (KSG), were considered. 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