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Title: MANAGERIAL IMPACTS ON PREFERENTIAL FLUID DYNAMICS

Author
item Gish, Timothy
item KUNG, K - UNIV. OF WI-MADISON
item KLADIVKO, E - PURDUE UNIVERSITY
item STEENHUIS, T - CORNELL UNIVERSITY
item Jaynes, Dan
item SHIRMOHAMMADI, A - UNIV. OF MD, COLLEGE PARK

Submitted to: International Symposium on Preferential Flow
Publication Type: Proceedings
Publication Acceptance Date: 8/20/2000
Publication Date: 1/3/2001
Citation: N/A

Interpretive Summary: There is substantial uncertainty in determining the impact of agriculture on water quality. This uncertainty is a result of the high degree of spatial and temporal variability associated with water movement and chemical transport through soil-making scientific interpretation and policy development difficult. In recent years, preferential flow has been identified as the major contributor to the unexpected transport of agricultural chemicals to groundwater. Unfortunately, the scope and magnitude of preferential flow, as well as its impact on and relevance to field-scale contaminant transport, have not been fully quantified and resolved. These limitations were, in large part, due to conventional sampling protocols which are inappropriate for measuring the impact of soil processes that are highly dynamic in both spatial and temporal domains. A method using tile drains was developed which allows, for the first time, subsurface transport of agricultural chemicals to be accurately determined Management practices, especially irrigation duration and intensity can have a dramatic impact on the transport of agricultural chemicals through soil. This study showed that as the irrigation duration and intensity increased, larger pores within the soil become hydraulically active and preferential flow paths become the dominant flow system governing transport.

Technical Abstract: Preferential flow has been identified as a major contributor to the rapid and unexpected transport of agricultural chemicals to groundwater. Unfortunately, the scope and magnitude of preferential flow, as well as its impact on and relevance to field-scale contaminant transport, have not been quantified and resolved. These limitations were, in large part, due to conventional sampling protocols which are inappropriate for measuring the impact of soil processes that are highly dynamic in both spatial and temporal domains. A method using tile drains was developed which allows subsurface fluxes of surface applied solutes to be accurately determined. Since larger pores may become hydraulically active as the soil profile becomes wetter, the impact of preferential flow paths on contaminant transport may be strongly influenced by rain intensity and duration. This presentation will use data collected from tile drain experiments to demonstrate the relevance and impact of agricultural management, specifically irrigation on preferential fluid dynamics.