HR: 08:15h
AN: H51A-02    [PDF]
TI: Overland Flow Generation and Soil Hydraulic Properties in Two Catchments in Central Panama
AU: * Godsey, S
AF: University of Cincinnati, Dept. of Civil and Environmental Engineering P.O. Box 210071, Cincinnati, OH 45221-0071 United States
AU: Elsenbeer, H
AF: Institute of Geoecology, University of Potsdam, PO Box 60 15 53, Potsdam, 14415 Germany
AU: Stallard, R
AF: USGS-WRD, 3125 Marine St. (RME127), Boulder, CO 80303-1066 United States
AB: Land management decisions in the Panama Canal watershed directly impact the hydrological functioning of the canal itself. Knowledge of the hydrological conditions in the forested portions of the watershed provides a baseline comparison for future land use changes. We chose to work on two streams on Barro Colorado Island that are representative of large regions of the watershed. These two streams respond differently to the same storm events: Conrad Trail Stream exhibits a fairly subdued and delayed response and Lutz Creek stream is flashier. In order to understand these differences, we investigated the soil saturated hydraulic conductivity (Ks) of the two catchments and studied the frequency of overland flow generation. The Ks measurements in dominant geologies in Lutz Creek as well as in Conrad Trail Stream are great enough at shallow depths (median Ks = 29.7, 65.6 and 38.3 mm/hr) that Hortonian overland flow is rare, but a marked decrease in Ks in Lutz Creek catchment at 30 cm (to 1.4 and 5.8 mm/hr) indicates that a perched water table leading to saturated overland flow is the likely runoff mechanism in Lutz Creek. In Conrad, Ks does not decrease as markedly with soil depth, and a perched water table would form at about 60 cm below the surface (median Ks = 0.7 mm/hr). Therefore, more water is able to infiltrate into the soil in Conrad Trail Stream and saturated overland flow is less common. Overland flow was generated much more frequently in Lutz Creek than in Conrad Trail Stream, with lower thresholds of storm magnitude, duration, antecedent wetness and intensity required to generate overland flow. We also quantified the importance of microtopographic features such as concentrated flow lines and the results have implications for experimental design at other field sites. The Lutz Creek and Conrad Trail stream information will provide a useful baseline for land management decisions.
DE: 1860 Runoff and streamflow
DE: 1866 Soil moisture
SC: Hydrology [H]
MN: 2003 Fall Meeting