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Spatial Averaging of van Genuchten Hydraulic Parameters for Steady-State Flow in Heterogeneous Soils

A Numerical Study

Biological and Agricultural Engineering Dep., Scoates Hall, Texas A&M University, College Station, TX 77843-2117

View larger version (88K): [in a new window]   Fig. 1. Images of randomly generated van Genuchten parameter fields for loam used in the simulations. (a) log(Ks) with Ks in centimeters per day; (b) log() with in (1/cm), |R|2 = 1.0; (c) log() with in (1/cm), |R|2 = 0.1; (d) log(n - 1), |R|2 = 1.0; (e) log(n - 1), |R|2 = 0.1.

View larger version (92K): [in a new window]   Fig. 2. Calculated log(q) fields with q in centimeters per second for both infiltration and evaporation when Ks and are spatially variable fields. (a) Infiltration with |R|2 = 1.0; (b) evaporation with |R|2 = 1.0; (c) infiltration with |R|2 = 0.1; (d) evaporation with |R|2 = 0.1. Ps = 30 (-cm) for infiltration and Ps = 480 (-cm) for evaporation.

View larger version (96K): [in a new window]   Fig. 3. Calculated log(q) fields with q in centimeters per second for both infiltration and evaporation when Ks and n - 1 are spatially variable fields. (a) Infiltration with |R|2 = 1.0; (b) evaporation with |R|2 = 1.0; (c) infiltration with |R|2 = 0.1; (d) evaporation with |R|2 = 0.1. Ps = 30 (-cm) for infiltration and Ps = 480 (-cm) for evaporation.

View larger version (50K): [in a new window]   Fig. 4. Maximum ratio of the horizontal flux over the vertical flux (qh/q) for selected values of the surface pressure head when Ks and are spatially variable fields.

View larger version (46K): [in a new window]   Fig. 5. Maximum ratio of the horizontal flux over the vertical flux (qh/q) for selected values of surface pressure head when Ks and n - 1 are spatially variable fields.

View larger version (44K): [in a new window]   Fig. 6. Effective parameter eff vs. surface pressure for various soil textural classes.

View larger version (41K): [in a new window]   Fig. 7. Effective parameter neff vs. surface pressure for various soil textural classes.

View larger version (49K): [in a new window]   Fig. 8. Coefficient of variation of the flux against surface pressure head for various soil textural classes.