Soil water flow due to surface topography in research drainage plots

Abstract

Tile drainage is common in the central United States and has resulted in greater storm flashiness. The purpose of this study was to determine if surface topography influenced water table depths, tile outflow, and water flow patterns in experimental plots. Tiles (1.22‐m deep) were installed at the center of each plot, and plastic barriers (1.83‐m deep) were installed between plots. Monitoring wells were installed and were read monthly during the growing season. During times with little rain the well‐drained block had the deepest water table depths (maximum of 4.75 m), and the wettest block had the shallowest water table depths (maximum of 2.15 m). During times with much rain, water table depths were similar for all blocks; however, water table gradients were larger during wet periods than dry periods (for example, 3.0 m m−1 vs. 0.5 m m−1). Mean water table depths for the well‐drained block were below the plastic barrier 47% of the time and below the tile depth 72% of the time. Conversely mean water table depths for the wettest block were deeper than the plastic barrier only 18% of the time and below the tile 54% of the time. There was slow lateral flow below the barriers from the upslope block to downslope plots; some downslope plots still had tile flow when there was lateral flow from upslope.