Clogging Effect on Hydraulic Conductivity

Soil clogging decreases porosity in the biozone with inert and biological materials. With the reduced soil porosity, the hydraulic conductivity of soil decreases with time (USEPA, 1980). A field-scale experiment suggests the reduction in hydraulic conductivity in the biozone is primarily influenced by STE loading rate and the type of infiltrative surface (Bumgarner and McCray, 2007). Weintraub et al. (2002) proposed a relationship between the biozone hydraulic conductivity and soil moisture contents.

$K_{bz}=K_{sat}\frac{\theta -\theta_f}{\theta_s-\theta_f}$ (7)

where $K_{bz}$ is biozone hydraulic conductivity (mm/hr), $K_{sat}$ is saturated hydraulic conductivity of soil (mm/hr), and $\theta$ is moisture content of biozone (mm). An advantage of this model is that, $K_b$ is directly related to $K_s$ and the soil moisture content. The theoretical basis on the formulation of the equation is not presented in the literature; instead, the formula is indirectly validated by comparing percolation to the subsoil layer as a function of time.