Developing Optimum Drainage Design Guidelines For The Red River Basin: Final Report

Artificial subsurface drainage has produced some of the most productive soils in the world and continues to be a common water management practice in Minnesota, the upper Midwest, and throughout the world. The agronomic and environmental benefits of subsurface agricultural drainage are many, including improved crop growth and yield, improved soil trafficability and field operations, and a decrease in sediment and phosphorus losses from poorly drained agricultural fields. A significant percentage of agricultural soils in the Red River Basin (RRB) may potentially benefit from subsurface drainage because of persistent high water tables, particularly during springtime, and a relatively short growing season. Installation of new subsurface drainage systems continues to increase in the RRB. In Minnesota and elsewhere in the region, the design approach for new drainage systems has changed little since the mid-1900's. For example, the Minnesota Drainage Guide lists drain spacings for Minnesota soils, for four drainage coefficients (0.25, 0.375, 0.5, 0.75 inches/day) and two drainage depths (3 and 4 ft), but provides no guidance to drainage practitioners on how these drainage depth x spacing combinations influence profitability and hydrology. We have recently calibrated (tested) the drainage simulation model, DRAINMOD, using data from the Southern Research and Outreach Center – Waseca drainage project1. The results obtained show a close agreement between the observed and the simulated values of both drainage volume and crop yield. Based on these results, we are currently conducting a research project, supported by the Minnesota Corn Research and Promotion Council, to investigate optimum drainage design guidelines for major soils in the Minnesota River Basin. Sands and Canelon2 recently conducted uncalibrated DRAINMOD simulations using estimated properties for three soils in the RRB. The goal of this work was to develop a more sophisticated hydrologic model for important soils in the RRB using measured soil parameters, by pursuing the following three objectives: (1) conducting sampling and analysis for up to six soils in the RRB; (2) performing DRAINMOD computer simulations for these soils for three locations, three drainage depths, and several drainage intensities (drain spacings); (3) disseminating the project results and conclusions through Extension channels.