Field-scale preferential flow at textural discontinuities

Lateral subsurface movement of water and solutes is of considerable interest to researchers and resource managers in many fields. Soil structure and morphology are often the dominant factors that control water and solute movement. In Major Land Resource Area 134 (Southern Mississippi Valley Silty Uplands) extending from southern Illinois to northern Louisiana, loess surface soil covers the underlying paleosol, forming a textural discontinuity that often creates transient saturated conditions. Shallow wells screened at this interface were installed to collect perched water, and bromide was applied as a tracer in 1993, Lateral movement of the bromide was very spatially varied, but bromide persisted in some areas until 1999 in the flow patterns that were initially identified. During the first year following application in 1999, lateral movement of atrazine was similar to the flow paths identified with the tracer; suggesting that the subsurface movement occurred in relatively well defined, but unpredictable areas of flow.