Transport Models for Solute Transfer to Surface Runoff

Two models were discussed to describe the solute transfer to surface runoff. One is a scouring-based model and the other is a diffusion-based model. The scouring-based model is a two-stage model. While the first stage is a quick decrease of mass loss of solute to surface runoff, the second stage is a slow one. The diffusion-based model assumed that solute transfer follows the Fick's law. In this study, a laboratory flume with a medium packed bed was designed. Four different sizes of uniform glass beads were chosen to be the media saturated with three different concentration of potassium chloride before runoff occurred. In a series of experiments, runoff was passed at varied flow rates, velocities, and depths over the medium bed. Runoff samples were taken at the end of flume and analyzed the concentration of potassium chloride. The relationships between the dimensionless modeled parameters and controlled variables were decided by multiple regression. On the other hand, two different soil conditions were selected to be the media. One soil condition was passed 9.5mm screen and the other was passed 4.0mm screen. The same processes of experiment were performed by using these two soil conditions. The outflow concentration of soil experiments was simulated by these two models. The results showed that the simulation of large soil condition was good, but the fine one was underestimated.