Unusual hydrograph characteristics, upper Rio Chagres, Panama

Date of Completion

January 2007

Keywords

Hydrology|Engineering, Environmental

Degree

Ph.D.

Abstract

Inaccessible locations and inhospitable working conditions have resulted in a lack of detailed hydrological knowledge in the tropics. I have established a new field observatory located near the town of Gamboa, Panama, adjacent to the mid-point of the Panama Canal. This observatory allowed detailed measurements of the hydrologic cycle at the first-order catchment scale. My investigations reveal that competing runoff production mechanisms are responsible for the observed streamflow. Both of these mechanisms are strongly dependent upon rainfall rate and secondarily upon cumulative rainfall volume. I have identified a small but hydrologically significant riparian zone that is decoupled from the hillslope. In contrast to the remainder of the catchment this riparian zone shows signs of frequent overland flow. Upslope regions occasionally produce overland flow during high-intensity rainfall. Parallel to the small scale studies in Gamboa, sub-watersheds of the 414 km2 upper Rio Chagres were instrumented. These gages showed that the Rio Chagres rarely reacts uniformly; instead, the observed runoff is usually the result of a limited portion of the watershed. Based on inspiration from field research a new conceptual model, Sac3, was developed. Sac3 was successfully calibrated and verified on several study watersheds. Sac3 was also used to explore the relationship deep groundwater storages had on seasonal changes in baseflow runoff behavior. ^

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