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Measured and Modeled Unsaturated Hydraulic Conductivity of a Walla Walla Silt Loam

^a Oregon State Univ., Columbia Basin Agricultural Research Center, P.O. Box 370, Pendleton, OR 97801
^b Texas A&M Univ. System, Texas Agricultural Experiment Station, 2301 Experiment Station Road, Bushland, TX 79012

View larger version (24K): [in a new window]   Fig. 1. The hydraulic conductivity as a function of [K()] from internal drainage experiments conducted at the Columbia Basin Agricultural Research Center, near Pendleton, OR. Current study refers to internal drainage data from six plots in 1998. The Allmaras et al. (1977) data represent published data from two adjacent plots. The solid line represents the log-function fitted to the pooled data.

View larger version (28K): [in a new window]   Fig. 2. Water release curve (WRC) for a Walla Walla silt loam derived from four different sources: WRC1 (•), which represents field-measured data from the internal drainage experiment in this study, combined with field-measured data of Allmaras et al. (1977), taken at same experiment station; WRC2 (), which represents laboratory- and field-measured data of Pikul (1988);WRC3 (), calculated data from the Rosetta model, using percentages of clay, silt, and sand, and bulk density reported by Allmaras et al. (1977) as inputs; and WRC4 (), calculated data using the Campbell (1985) model, which also used the percentages of clay, silt, and sand, and bulk density of Allmaras et al. (1977) as inputs. The solid curve represents the fitted van Genuchten model (1980), using the field-measured internal drainage data (WRC1).

View larger version (27K): [in a new window]   Fig. 3. Fitted log-linear model of hydraulic conductivity as a function of for a Walla Walla silt loam using the modified Klaij and Vachaud method (MKV) and four water release curves (WRC): WRC1 (log10K() = 9.34–4.05, r2 = 0.54, SEE = 0.71); WRC2 (log10 K() = 12.39–5.60, r2 = 0.67, SEE = 0.67); WRC3 (log10 K() = 13.29–5.54, r2 = 0.67, SEE = 0.72); and WRC4 (log10 K() = 22.55–12.12, r2 = 0.73, SEE = 1.05). Outside lines represent the 95% confidence interval for the linear regression equation.

View larger version (19K): [in a new window]   Fig. 4. Measured and modeled K() for a Walla Walla silt loam near Pendleton, OR: Measured-internal drainage (ID) is from the internal drainage method; Measured-MKV is from the Modified Klaij and Vachaud; Modeled-1 is from the Mualem-van Genuchten model (MVG), with parameters estimated by the Rosetta model, using soil texture data as inputs; and Modeled-2 is also from the MVG, but with parameters obtained from field-measured water release curve (WRC1) and saturated hydraulic conductivity (Ksat).