A Simple Numerical Method in Modeling Soil Water Dynamics During Vertical Drainage

The change of soil water content (SWC) during vertical drainage may be divided into two parts. The maximum change of SWC, which results when there is no incoming flow, can be predicted from hydraulic conductivity. The actual change of SWC can be predicted from hydraulic conductivity and the incoming flow. A new model has been developed to simulate soil water dynamics during vertical drainage using this concept. Within this model, the maximum daily change of soil water content (SWC) was calculated using a ratio between initial SWC minus field capacity (FC, defined as SWC after 10 days of drainage) and FC. The actual daily change of SWC was obtained from multiplying the maximum daily change of SWC by a coefficient, F. The coefficient F accounts for the impact of the incoming flow on the change of SWC. The model was tested on more than 300 theoretical soils. The model SWC estimates were comparable to SWC estimates of an analytical model.