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United States Department of Agriculture

Agricultural Research Service

Title: Non-Destructive Site Investigation of Preferential Pathways

Authors
item Truman, Clinton
item Bosch, David
item Fletcher, Ricky

Submitted to: Transactions of the ASAE
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 2, 1999
Publication Date: December 2, 1999
Citation: TRUMAN, C.C., BOSCH, D.D., FLETCHER, R.G. NON-DESTRUCTIVE SITE INVESTIGATION OF PREFERENTIAL PATHWAYS. TRANSACTIONS OF THE AMERICAN SOCIETY OF AGRICULTURAL ENGINEERS. PAPER #99-2144.1999. IN PROCEEDINGS OF THE ADVANCES IN WATER QUALITY MODELING. K. KING ED. INTERNATIONAL MEETING OF THE ASAE, TORONTO, CANADA. PP. 116-120. 1999.

Interpretive Summary: Soils in the Coastal Plain region of Georgia vary with depth. Soil properties influence water and agrichemical movement. Understanding water and agrichemical movement through these soils requires non- destructive methods to determine depth to and lateral extent of subsurface soil properties. We evaluated ground-penetrating radar (GPR) as a tool for identifying and determining the spatial variability of soil subsurface properties causing preferential flow of water and agrichemicals and identifying locations which can be instrumented to accurately and efficiently evaluate preferential transport of water and agrichemicals. GPR was used on a 1 ha plot, composed of Troup and Eustis sands, grided at 10 m intervals. Depth and lateral extent of clay horizons, geologic materials, and depositional sand lenses were accurately measured by GPR. GPR, along with ground-truth data, were used to identify and strategically locate eight sites which were instrumented to evaluate water and agrichemical movement. GPR is a valuable research tool that provides a continuous, non-destructive profile of subsurface properties found in Coastal Plain soils responsible for preferential flow in relatively short periods of time.

Technical Abstract: Soils in the Coastal Plain region of Georgia vary in depth, texture, depth to water table, and other chemical, physical, and morphological properties. These soil subsurface features and/or properties influence water and agri- chemical movement through these soils. Understanding water and agri- chemical movement in Coastal Plain soils requires non-destructive methods to determine depth to and lateral extent of subsurface featues or proper- ties. Objectives were to evaluate ground-penetrating radar (GPR) as a tool for 1) identifying and determining spatial variability of soil sub- surface featues or identifying locations which can be instrumented to accurately and efficiently evaluate prefrential transport of water and agrichemicals. A subsurface interface radar was used on a 1 ha plot (Troup and Eustis sand) grided at 10 m intervals. Depth and lateral extent of subsurface features (argillic horizons, clay layers, and sand lenses) which hhave contrasting dielectric properties were accurately measured by GPR. GPR and ground-truth data were used to identify and strategically locate eight sites which were instrumented to evaluate preferential transport of water and agrichemicals. GPR provides a continuous, non-destructive profile of many subsurface features found in Coastal plain soils responsi- ble for causing preferential flow in relatively short periods of time.

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