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On the Effective Averaging Schemes of Hydraulic Properties at the Landscape Scale

^a Division of Hydrologic Sciences, Desert Research Institute, 755 E. Flamingo Rd., Las Vegas, NV 89119
^b Dep. of Biological and Agricultural Engineering, Texas A&M Univ., College Station, TX 77843-2117

View larger version (27K): [in a new window]   Fig. 1. Some examples of lognormal probability density function and trapezoidal probability function.

View larger version (72K): [in a new window]   Fig. 2. Little Washita (LW) watershed geographical location. Latitude top: 35.0067°, bottom: 34.7688°; longitude right: –97.8492°, left: –98.3006°.

View larger version (24K): [in a new window]   Fig. 3. Influence of the skewness on the effective averaging schemes for = 6.0 and h = 5.0: (a) Gardner model, (b) Brooks–Corey model, (c) van Genuchten model. E, effective parameter coefficient; CS, coefficient of skewness; h, dimensionless suction head at surface; , mean value of dimensionless van Genuchten .

View larger version (23K): [in a new window]   Fig. 4. Influence of the skewness on the effective averaging schemes for = 1.0 and h = 5.0: (a) Gardner model, (b) Brooks–Corey model, (c) van Genuchten model. E, effective parameter coefficient; CS, coefficient of skewness; h, dimensionless suction head at surface; , mean value of dimensionless van Genuchten .

View larger version (24K): [in a new window]   Fig. 5. Influence of the skewness on the effective averaging schemes for = 6.0 and h = 0.5: (a) Gardner model, (b) Brooks–Corey model, (c) van Genuchten model. E, effective parameter coefficient; CS, coefficient of skewness; h, dimensionless suction head at surface; , mean value of dimensionless van Genuchten .

View larger version (42K): [in a new window]   Fig. 6. The * fields for the Little Washita watershed: (a) * = 388 and (b) * = 150(1 + 100). , empirical van Genuchten parameter where * = L; L, depth to water table.

View larger version (19K): [in a new window]   Fig. 7. The * probability distribution for the Little Washita (LW) watershed and the synthetic lognormal and trapezoidal distributions: (a) when water table depth is constant and (b) when water table depth is fully correlated with . , van Genuchten empirical parameter where * = L; L, depth to water table; WT, water table; PDF, probability density function.

View larger version (21K): [in a new window]   Fig. 8. Effective parameter coefficient E for the Little Washita (LW) watershed compared with the synthetic distribution functions: (a) for evaporation when h = 5.0 and (b) for infiltration when h = 0.5. E, effective parameter coefficient; CS, coefficient of skewness; h, dimensionless suction head at surface.