HR: 08:30h
AN: H51A-03    [PDF]
TI: Runoff Production in the Upper Rio Chagres Catchment, Panama
AU: * Niezialek, J M
EM: justinn@engr.uconn.edu
AF: Dept. of Civil and Environmental Engineering, 261 Glenbrook Rd, U-2037 University of Connecticut, Storrs, CT 06269 United States
AU: Ogden, F L
EM: ogden@engr.uconn.edu
AF: Dept. of Civil and Environmental Engineering, 261 Glenbrook Rd, U-2037 University of Connecticut, Storrs, CT 06269 United States
AB: Runoff production in watersheds in the seasonal tropics is governed by a number of factors. The mountainous 414 sq. km upper Rio Chagres watershed offers a unique opportunity to better understand the runoff production mechanisms in seasonal tropical catchments through data analysis and modeling. The upper Rio Chagres catchment provides the majority of inflows to the Panama Canal, has been monitored for over 60 years as part of canal operations. Discharge data are available at both the catchment outlet (Chico gaging station) and an internal catchment location (Rio Piedras gaging station). There are also seven tipping bucket recording rain gages in and around the catchment. Analysis of runoff data reveals anomalously-high runoff production efficiencies early in the wet season. Furthermore, the existence of two quasi-stable base flow regimes during the wet season imply critical threshold storages. Initial field studies have shown that the soils are water repellent during the dry season. Runoff data from the 80 sq. km Rio Piedras subcatchment reveal ephemeral flows throughout the wet season, indicating significant heterogeneity in runoff production and deep groundwater circulation. Preliminary hydrologic modeling is performed with the Sacramento Soil Moisture Accounting Model (SAC-SMA), calibrated using data from 1988 and verified using data from 1989. Further modeling on the flood of 28-31 December, 2000 is also performed. Modeling using the distributed parameter GSSHA model combined with the Sacramento groundwater module allows simulation of distributed runoff. However, the role of interception by the triple-layer tropical canopy and the magnitude of evapotranspiration are uncertain. New data collection is proposed in the Rio Chagres catchment to help quantify interception and evapotranspiration. This instrumentation will include measurements of rainfall above the canopy, cloud stripping, stemflow, throughfall, soil moisture, groundwater, interflow, evapotranspiration and overland runoff. Intensive field observations during the transition from dry to wet season are proposed to develop predictive understanding of unusually-high runoff production efficiencies.
DE: 1818 Evapotranspiration
DE: 1836 Hydrologic budget (1655)
DE: 1860 Runoff and streamflow
DE: 1866 Soil moisture
SC: Hydrology [H]
MN: 2003 Fall Meeting