ND Drain Computer Software for Lateral Effect Evaluation of a Subsurface Drain

Abstract

The USDA-NRCS computer program, ND Drain, calculates the lateral effect of a subsurface drain or drainage ditch based on soil hydraulic properties. Lateral effect is defined as the minimum distance between a drain and a wetland necessary to maintain wetland hydrology conditions required by the National Food Security Act (1985). Soil hydraulic properties are calculated using van Genuchten (VG) parameters for conductivity and water retention as predicted by the Rosetta model (Schaap, 2000). Rosetta, a hierarchal model, allows five levels of VG parameter predictions. The fifth, or highest, level of prediction of VG parameters can be performed using the following information for each soil layer: depths to top and bottom of the soil layer; sand, silt, and clay percentages; dry bulk density; and 33 and 1500 kPa moisture contents. This combination of laboratory and field soils data is available from the NRCS National Soil Information System (NASIS) and also from the NRCS Web Soil Survey. ND Drain provides a choice of four drainage equations for calculation of lateral effect. ND Drain predictions apply to saturated soil conditions only and do not apply to hydrology conditions involving surface ponding or runoff interactions.