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regional evaluation of evapotranspiration in the everglades
Regional Evaluation of Evapotranspiration in the Everglades
Abstract
One of the most important components of the Everglades (south Florida)
water budget is evapotranspiration (ET). In this area, most rainfall is likely
returned to the atmosphere by ET. A study to quantify and model ET in the
Everglades was begun in 1995. A network of nine ET-evaluation sites was
established that represents the varied hydrologic conditions and vegetative
characteristics of the Everglades. Data from continuous measurements of
parameters for evaluation of ET at the sites for the period January 1996 through
December 1997 were used to develop regional models that can be used to
simulate ET at other times and places throughout the Everglades.
The Bowen-ratio energy budget method was selected for the ET
evaluation. After careful screening to eliminate erroneous data, site and regional
models of ET were calibrated for the nine sites. A modified Priestley-Taylor
model of ET was calibrated for each site. In these models the Priestley-Taylor
coefficient () was expressed as a function of incoming solar energy and water
level. The individual site models were then combined into two regional models:
one is applicable to vegetated wet-prairie and sawgrass-marsh sites in the
natural Everglades system, and the other is applicable to freshwater sloughs and
other open areas with little or no emergent vegetation.
Computed ET totals for all nine sites ranged from 42.78 inches per year at
a sometimes-dry sparse-sawgrass site to 55.54 inches per year at an open-water
site. Differences in annual ET relate to water availability and perhaps to density
of vegetation.
The annual total ET values simulated by the regional models generally are
in relatively close agreement with the computed values. The difference between
computed and simulated ET generally was less than 3 inches per year. The
median difference was about 1.4 inches per year.
(This paper is from the proceedings of the Third International Symposium on Ecohydraulics CDROM) Related information:
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U.S. Department of the Interior, U.S. Geological Survey
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Last updated: 06 December, 2004 @ 05:13 PM(TJE)