Monday, 7 November 2005
18

Quantifying a Shallow Groundwater Leachate Flux in a Non –Tilled Drained System.

Timothy Gish1, King-Jau Kung2, Craig S. Daughtry3, Tammo S. Steenhuis4, Eileen Kladivko5, Thomas J. Nicholson6, and Ralph E. Cady6. (1) USDA-ARS Hydrology and Remote Sensing Lab., Building 007, Room 104, BARC-West, Belstville, MD 20705, (2) Department of Soil Science, University of Wisconsin, Madison, WI 53706, (3) USDA/ARS Hydrology & Remote Sensing, B-007, R-101, BARC West, 10300 Baltimore Ave., Beltsville, MD 20705-2350, (4) Cornell University, 206 Riley-Robb Hall, Ithaca, NY 14853, (5) Purdue University, Purdue University, 615 W. State St., West Lafayette, IN 47907-2053, (6) US NRC, Mail Stop T-9C34, Washington, DC 20555

To accurate quantify solute transport, determine relevance or develop theory to accurately describe chemical behavior, it is crucial to first quantitatively determine a total solute flux, including preferential flow. A protocol extending a flux method previously developed for tile-drained systems was tested for shallow ground water systems without a tile drain. Bromide was surface broadcast applied around three shallow observation wells and irrigated at 4.1 mm/h. Throughout the study the water table height, soil moisture profiles were continuously monitored along with water flows from pumped observation wells. The bromide flux monitored represented a treated soil area of about 30 m2 per well. Results indicated that: 1) about 98 percent of the applied bromide tracer was recovered; 2) at 4.1 mm/h over half of the surface-applied bromide was recovered at a depth of 1.6 m after only 280 mm of irrigation; and 3) at this location, bromide fluxes were dominated by preferential flow when subjected to a 4.1 mm/h irrigation rate. Preliminary results suggest this protocol may be a useful tool for quantifying solute transport fluxes in non tile-drained systems that contain a shallow groundwater system.


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