FLORIDA PROJECTS

• Aquifer Characterizations

• Availability of Water

• Climate Change and Hydrologic Extreme Events
• Effects of Climate Extremes on Central Florida Lakes
• Predicting the Effects of Sea-Level Rise on Spring Creek Ecology
• The Evapotranspiration (ET) Network in Florida

• Ecosystems

• Hydrologic Modeling

• Surface Water

• Water Quality Conditions

• Wetlands

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Evapotranspiration Network in Florida

Project Chief: David Sumner, Amy Swancar, Barclay Shoemaker
Cooperators: Miami Dade County, Priority Ecosystem Studies, Reedy Creek Improvement District, South Florida Water Management District, Southwest Florida Water Management District, St Johns River Water Management District, Tampa Bay Water
Period of Project: October 2000 – September 2012

Problem Statement

Micrometeorological station at Starkey pasture, Pasco County, Florida.

Evapotranspiration (ET) is a large part of the hydrologic budget in Florida, ranging from 30 to over 100% of average precipitation. In the past, the accuracy of hydrologic models, basin-scale studies, water budgets, and other hydrologic analyses throughout the State was reduced because of the lack of accurate estimates for this large water loss. Scientists and water managers in Florida would benefit from having a network of consistently operated high-quality ET stations from representative land use areas using state-of-the-science methods. Another recurring problem in hydrologic simulation and water allocation strategies in Florida has been inconsistencies between the five State of Florida Water Management Districts in methods for computing the potential and reference ET. Potential ET (PET) is a necessary data input for most hydrologic simulation models. Reference ET (RET) is a necessary input for WMD water allocation to water users.

Objectives

1) Measure actual ET from representative land covers in Florida

2) Develop predictive models to estimate ET from environmental variables such as depth to water, season, and net radiation

3) Provide 2-km gridded satellite-based estimates of potential and reference ET on a daily time scale for the entire State

Components of the surface-energy balance used to estimate evapotranspiration.

Approach

For ET stations, evapotranspiration and other variables are measured for between 2 and 10 years to develop relations between measured ET and environmental factors such as weather, groundwater levels, and plant cover conditions. Data collected included:

Results

Annual ET rates at land-based sites vary from a low of 570 mm (22.4 inches) at a pasture with a deep water table to 1340 mm (53 inches) at a sawgrass marsh. Rates at open-water sites exceed 1500 mm (59 inches). Daily values of ET are archived in the USGS NWIS database and can be accessed at http://fl.water.usgs.gov/et/etdata.html

The daily PET and RET datasets, by year and county from 1995 through 2010, can be accessed at http://fl.water.usgs.gov/et/

Information Products

Shoemaker, W. B., Lopez, C. D., Duever, M. J., 2011, Evapotranspiration over spatially extensive plant communities in the Big Cypress National Preserve, southern Florida, 2007-2010: http://pubs.usgs.gov/sir/2011/5212/

Sumner, D.M., 2001, Evapotranspiration from a Cypress and Pine Forest Subjected to Natural Fires in Volusia County, Florida, 1998-99: U.S. Geological Survey Water-Resources Investigations Report 01-4245, 55 p.

Shoemaker W.B., S. Huddleston, A.M. O'Reilly, and C. Boudreau, 2008. Sensitivity of wetland saturated hydraulic heads and water budgets to evapotranspiration, Wetlands, Vol. 28, No. 4, December 2008, pp. 1040-1047.

Shoemaker W. B., D. M. Sumner, and A. Castillo, 2005, Estimating changes in heat energy stored within a column of wetland surface water and factors controlling their importance in the surface energy budget, Water Resources Research, 41, W10411, doi:10.1029/2005WR004037.

Shoemaker W.B., and D.M. Sumner, 2006, Alternate corrections for estimating actual wetland evapotranspiration from potential evapotranspiration, Wetlands, Volume 26, No. 2, pp. 528 – 543.

Mecikalski, J. R., Sumner, D. M., Jacobs, J. M., Pathak, C. S., Paech, S. J., and Douglas, E.M., 2011, Use of Visible Geostationary Operational Meteorological Satellite Imagery in Mapping Reference and Potential Evapotranspiration over Florida: in Evapotranspiration, edited by Leszek Labedzki, Intech, http://www.intechopen.com/books/show/title/evapotranspiration, 26 p.