DRAINMOD is a computer simulation model developed by Dr.Wayne Skaggs at the Department of Biological & Agricultural Engineering, North Carolina State University, Raleigh, NC in 1980. The model simulates the hydrology of poorly drained, high water table soils on an hour-by-hour, day-by-day basis for long periods of climatological record (e.g. 50 years). The model predicts the effects of drainage and associated water management practices on water table depths, the soil water regime and crop yields. It has been used to analyze the hydrology of certain types of wetlands and to determine whether the wetland hydrologic criterion is satisfied for drained or partially drained sites. The model is also used to determine the hydraulic capacity of systems for land treatment of wastewater. The model has been successfully tested and applied in wide variety of geographical and soils conditions. In the last 20 years, the model's capability has been extended to predict the effects of drainage and water management practices on the hydrology and water quality of agricultural and forested lands both on field and watershed scale.
The latest version, DRAINMOD 6.0 , combines the original DRAINMOD hydrology model with DRAINMOD-N (nitrogen sub-model) and DRAINMOD-S (salinity sub-model) into a Windows based program. The new version includes a graphical user interface that allows easy preparation of input data sets, running simulations as well as displaying model outputs. In addition to organizing the hydrology, nitrogen, and salinity components of DRAINMOD, the interface facilitates analyses of the effect of drainage system design on subsurface drainage, surface runoff, SEW30, crop yield, and nitrogen loss in surface and subsurface drainage by automatically editing drainage design parameters (e.g. drain spacing & drain depth) over a specified range, simulating the different designs and graphically displaying the results. The interface also calculates the runoff volume from surrounding areas that drain to a site and adds that runoff volume to a DRAINMOD water balance of the site. Version 6.0 also includes routines for soil temperature modeling and considers freezing and thawing effects on drainage processes.