Soil Physics with HYDRUS: Chapter 3 Equations, Tables, and Figures

3.1 – 3.5

3.6 – 3.9

3.10 – 3.13

3.14 – 3.17

3.18 – 3.20

3.21 – 3.25

3.26 – 3.30

3.31 – 3.34

3.35 – 3.39

3.40

TABLE 3.1 Brooks and Corey (1964) soil hydraulic parameters (K s, θ r, θ s, h a, and λ) for 11 textural classes (Rawls et al., 1982). Macroscopic capillary length (λ c ) calculated using Equation 3.21 and Equation Textural classKsKs θrθr θsθs haha λλcλc (cm d -1 ) (cm 3 cm -3 ) (cm)(-)(cm) Sand Loamy sand loam Loam Silt loam Sandy clay loam Clay loam Silty clay loam clay Silty clay Clay

TABLE 3.2 Soil properties (texture, sand, silt, clay, structure, and K s ) for the Cecil loamy sand (plot 4 from Bruce et al., 1983). HorizonTextureClaySiltSandStructureKsKs %%cm h -1 ApLoamy sand71578Weak, medium granular19.19 BAClay loam372043Weak, medium, subangular blocky 7.69 Bt1Clay502030Strong, medium, subangular blocky Bt2Clay412534Strong, medium, subangular blocky BCClay loam362737Weak, medium, subangular blocky CSandy clay loam 24 52Massive0.467

TABLE 3.3 Soil texture/structure categories for estimation of macroscopic capillary length (λ c ), adapted from Elrick and Reynolds (1992). Soil texture/structure categoryλcλc (cm) Coarse and gravelly sands; may also include some highly structured soils with large cracks and/or macropores 2.8 Most structured soils from clays through loams; also includes unstructured medium and fine sands 8.3 Soils which are both fine textured (clayey) and unstructured25 Compacted, structureless, clayey materials such as landfill caps and liners, lacustrine or marine sediments, etc 100

TABLE 3.4 Dimensionless coefficients for the polynomial (Equation 3.35) describing the geometric factor G, valid for H/r < 10 (Bosch and West, 1998) Soil texture/structureA1A1 A2A2 A3A3 A4A4 Sand Structured loams and clays Unstructured clays

Figure 3.4 Saturated hydraulic conductivity as a function of clay fraction for 324 soils from the UNSODA database (Nemes et al., 2001).