HR: 1340h
AN: H13I-1413    [Abstracts]
TI: Field Scale Dispersion Measured with Tile Drains
AU: * Majs, F
EM: fmajs@uga.edu
AF: Savannah River Ecology Laboratory, Drawer E, The University of Georgia, Aiken, SC 29803 United States
AU: Radcliffe, D E
EM: dradclif@uga.edu
AF: Department of Crop and Soil Sciences, 3111 Miller Plant Sciences Building, The University of Georgia, Athens, GA 30602-7272 United States
AU: Seaman, J C
EM: seaman@srel.edu
AF: Savannah River Ecology Laboratory, Drawer E, The University of Georgia, Aiken, SC 29803 United States
AB: The use of tile drains has been suggested as a method of measuring field-scale transport parameters, but lateral flow to the drains in the saturated zone prevents a simple 1D analysis. Our objective was to fit field data using Hydrus-2D, a computer program that numerically solves Richards equation for describing saturated-unsaturated flow and the convection-dispersion equation for solute transport. Two breakthrough curves, using Cl^- as a tracer, were obtained from a 12.5 by 30.5-m plot drained by five tile drains under two irrigation rates of 0.25 and 0.45 cm h^-1 respectively. The inverse optimization feature of Hydrus-2D was used to optimize saturated hydraulic conductivity and n and α parameters of van Genuchten's (1980) soil water characteristic curve equation and longitudinal dispersivity. Saturated hydraulic conductivity, n, and α parameters were first optimized using tile drain flow data at the two irrigation rates. Longitudinal dispersivity was subsequently optimized using measured tile-drain Cl^- concentrations. The optimized longitudinal dispersivities for the unsaturated zone at the higher irrigation rate were about twice that for the lower irrigation rate. This illustrates the effect of preferential flow on field-scale solute transport.
DE: 1832 Groundwater transport
DE: 1875 Vadose zone
DE: 3333 Model calibration (1846)
SC: Hydrology [H]
MN: Fall Meeting 2005