Simulating Subsurface Tile Drainage Water Outflow Using Drainmod in Atlantic Canada.

Artificial subsurface drainage installation helps to maintain water table levels and provide optimum crop moisture. Subsurface tile drainage is a common practice in the cool moist environment of Atlantic Canada and other moist regions around the world. The main objective of this study is to evaluate the performance of DRAINMOD in simulating water table levels and water outflow from tile-drained agricultural fields. DRAINMOD, a process-based, distributed and field-scale model, was evaluated with field measurements taken in a conventional, subsurface- drained field growing mixed forages in Newfoundland, Canada. This site is on the Avalon Peninsula of Eastern Newfoundland with a rolling landscape and predominantly poorly drained Podzolic soils. The tiles were installed at 0.8 m deep and spaced 12 m apart. Drainage outflows (two per plot) from twelve experimental plots (32 m x 60 m each) were monitored for two years. The results revealed that the simulated water table depths and drainage volumes responded similarly to the measured outflows on this site but additional sites needs to be assessed in this cool wet climate. Based on the results of this study, DRAINMOD gave a clear insight into the possibility of using this modeling tool for designing or evaluating subsurface drainage systems in Atlantic Canada. However, further evaluation of DRAINMOD is necessary with careful calibration and validation in order to obtain optimum drainage design parameters for the major agricultural soils in this cold wet climate.

Keywords: DRAINMOD, Subsurface drainage, Forage mixtures, Modeling, Agriculture