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Project Summary Sheet

U.S. Geological Survey, Greater Everglades Priority Ecosystems Science (PES) Initiative

Fiscal Year 2004 Study Summary Report

Study Title: Evapotranspiration Measurements and Modeling in the Everglades
Study Start Date: October 1994 Study End Date: September 2005
Web Sites:
Location (Subregions, Counties, Park or Refuge): Total System Southern Everglades, Dade and Monroe Counties
Funding Source: USGS's Greater Everglades Priority Ecosystems Science (PES) Initiative
Principal Investigator(s): Edward R. German,, 407-865-7575
Study Personnel: None
Supporting Organizations: USGS
Associated / Linked Studies: None

Overview & Objective(s): Evapotranspiration (ET) is one of the most important components of the Everglades water budget. The principal objective of the study is to develop an understanding of ET within the Everglades drainage unit, excluding agricultural and brackish environments. To achieve this, a network of ET-measurement sites was established in the Everglades in 1996, representing the various types of hydrologic and vegetative environments. Eight sites were operated in 1996 and nine sites were operated in 1997. Data from these sites was used to characterize ET and other meteorological conditions in the Everglades, and to develop models of ET as a function of solar radiation and water level. A report describing these findings was published in 2000. Data collection continued at selected sites during 1998-2000 to provide data for other studies involved with understanding water levels and flows in the Everglades. In 2000, new sites were established in Shark Valley Slough, to test transferability of models developed using 1996-97 data, and to refine the understanding of factors related to ET.

Status: All sites were removed by December 2003. Most data processing has been completed and final report is in preparation.

Recent Products: An abstract was submitted for the First National Conference on Ecosystem Restoration, Dec. 2004

Planned Products: The final product consists of an interpretive report describing data and models.

Specific Relevance to Information Needs Identified in DOI's Science Plan in Support of Ecosystem Restoration, Preservation, and Protection in South Florida (DOI's Everglades Science Plan):
This study supports all projects that will utilize hydrologic models to accomplish objectives. These include the Water Conservation Area 3 Decompartmentalization and Sheetflow Enhancement project and the Landscape-Scale Modeling project. Estimates of ET are necessary for all hydrologic models.

Key Findings:

  1. Models based on the Priestley-Taylor principles can be used to estimate ET as a function of water depth, incoming solar energy, and net available energy. In the absence of data on net available energy, air temperature and water depth data can be used to estimate net available energy.
  2. ET is related to water depth, with lowest ET for a given energy input occurring when water levels are below land surface.
  3. Based on data from nine sites in the natural Everglades system, ET ranges from about 42 in/yr in drier locations to as high as 57 in/yr in open-water areas.

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