Snow, snowmelt, and the effects of frozen conditions on soil water processes are not considered in DRAINMOD.  Therefore, application is confined to periods when the soil is not frozen. The program was designed for use in humid regions and its routine application is limited to those regions.  It may be used for irrigated arid regions where the water table is shallow and drainage is required.  The rainfall files or the irrigation routine must be modified to insure that the irrigation amounts and timing are correct for this application of the model.