The complex dielectric constant of the soil surrounding a land mien and its contrast with the dielectric constant of the landmine are critical to the effectiveness of ground penetrating radar (GPR) for landmine detection. These parameters affect the velocity and attenuation of the radar signal as well as the strength of the reflection form the mine. The dielectric properties of the soil depend on the soil texture and bulk density as well as the soil water content. In previous work, we have simulated the unsaturated water flow around a landmine. In this paper we summarize a collection of models that can be used to predict the dielectric constant, velocity of the GPR signal, attenuation, and reflection coefficient form soil type and soil water content. These models have been integrated into a MATLAB software package. Using these models, we can determine whether or not field conditions are appropriate for use of GPR. Under dry conditions, the soil water content may be too low for good GPR performance. If the soil is too dry, we can select an appropriate level of soil water content and design a watering scheme to bring the soil water content up the desired level. We present a case study in which a soil watering scheme was designed, simulated, and the performed at a field site.