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Runoff Generation on Barro Colorado Island (BCI), Panamá
| Title: | Runoff Generation on Barro Colorado Island (BCI), Panamá |
| Author: | Godsey, Sarah |
| Description: | Identification of the location of source areas of overland flow (OF) and quantifying the flow is important for understanding the hydrology and hydrochemistry of a catchment. A review of more than thirty years of research on overland flow in humid forests reveals that (1) the variable source area (VSA) concept should be modified slightly to describe all OF in these areas, and (2) the methodology for quantifying OF is insufficient in some cases. Inconsistencies in the definition and application of the VSA model suggest modifications are necessary to improve experimental design and conceptual understanding. The methodology employed in each reviewed study is also summarized, and recommendations are made for future OF research in humid forests. Based on this review, I sought to quantify overland flow in two lithologically distinct rainforest catchments. Two streams on Barro Colorado Island in central Panamá respond with marked differences to the same storm events. Lutz creek is quite flashy and Conrad stream exhibits a more subdued and delayed response. To understand these differences, I investigated the soil saturated hydraulic conductivity (Ks) of the two catchments and studied the frequency of overland flow generation. Ks measurements in dominant geologies in Lutz as well as in Conrad 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 catchment at 30 cm (to 1.4 and 5.8 mm/hr) indicates that a perched water table leading to saturated overland flow is likely the principal runoff mechanism in Lutz. 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 and saturated overland flow is less common. Overland flow was generated much more frequently in Lutz than in Conrad, with lower thresholds of storm magnitude, duration, antecedent wetness and rainfall intensity required to generate overland flow. I also quantified the importance of microtopographic features such as concentrated flow lines. |
| Permanent Link: |
http://rave.ohiolink.edu/etdc/view?acc_num=ucin1059398714
http://hdl.handle.net/2374.OX/11681 |
| Date: | 2003 |
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