Numerical Modeling of Preferential Flow at the Pantex Plant Area

The objective of this study was to analyze preferential flow based on observations from four ponding tests conducted in the vicinity of the Pantex Plant. According to soil profiles exposed after the field ponding tests (Xiang et al., 1993), we derived the hydraulic conductivity of an equivalent homogeneous soil as that of the actual heterogeneous soil. Models of four different types of subsurface flow were considered. These include flow through the soil matrix, through root tubules, between ped faces, and along soil-filled cracks. The results of numerical simulations of matrix flow were similar to field observations of matrix flow from ponding tests. To evaluate preferential flow, different values of hydraulic conductivity were used. The simulations show that preferential flow results in an increased rate of water movement because of the higher equivalent hydraulic conductivity.