HR: 1340h
AN: H13C-0450    [Abstracts]
TI: Evaluation of Temporal and Spatial Distribution of Error in Modeled Evapotranspiration Estimates
AU: * Senarath, S U
EM: ssenarat@sfwmd.gov
AF: South Florida Water Management District, 3301 Gun Club Road, West Palm Beach, FL 33406 United States
AB: Evapotranspiration (ET) constitutes a significant portion of Florida's water budget, and is second only to rainfall. Consequently, accurate ET estimates are very important for hydrologic modeling work. However, in comparison to rainfall, relatively few ground stations exist for the measurement of this important model input. Consequently, ET estimates produced by models are often subject to error. Satellite-based ET estimates provide an unprecedented opportunity to measure actual ET in sparsely monitored watersheds. They also provide a basis for comparing errors in modeled actual ET estimates that are induced due to the following reasons: 1) spatial interpolation and data-filling methods; 2) inaccurate and sparse meteorological data; and, 3) simplified parameterization schemes. In this study, satellite-based daily actual ET estimates from the Water Conservation Area 3 (WCA-3) watershed in South Florida, USA, are compared with those obtained from a calibrated finite-volume regional hydrologic model for the 1998 and 1999 calendar years. The satellite-based ET estimates used in this study compared well with measured ground-based actual ET data. The WCA-3 watershed is an integral part of Florida's remnant Everglades, and covers an area of approximately 2,400 square kilometers. It is compartmentalized by several levees and road embankments, and drained by several major canals. It also serves as a major habitat for many wildlife species, a source for urban water supply and an emergency storage area for flood water. The WCA-3 is located east of the Big Cypress National Preserve, and north of the Everglades National Park. Despite its significance, WCA-3 has relatively few ET monitoring stations and meteorological stations. Consequently, it is ideally suited for evaluating and quantifying errors in simulated actual ET estimates. The Regional Simulation Model (RSM) developed by the South Florida Water Management District is used for the modeling of these ET estimates. The RSM is an implicit, finite-volume, continuous, distributed, integrated surface/ground-water model, capable of simulating one-dimensional canal/stream flow and two-dimensional overland flow in arbitrarily shaped areas using a variable triangular mesh. The RSM has several options for modeling actual ET. An empirical parameterization scheme that is dependent on land-cover, water-depth and potential ET is used in this study for estimating actual ET. The parameter-sensitivities of this scheme are investigated and analyzed for several predominant land-cover classes, and dry- and wet-soil conditions. The RSM is calibrated and verified using historical time-series data from 1988 to 1995, and 1996 to 2000, respectively. All sensitivity and error analyses are conducted using estimates from the verification period.
DE: 1818 Evapotranspiration
DE: 1833 Hydroclimatology
DE: 1836 Hydrologic budget (1655)
DE: 1860 Runoff and streamflow
DE: 1890 Wetlands
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting