ABSTRACT: Understanding the water budget of the Everglades system is crucial to the success of restoration and management strategies. Although the water budget is simple in concept, it is difficult to assess quantitatively. Models used to simulate changes in water levels and vegetation resulting from management strategies need to accurately simulate all components of the water budget.
One of the most important components of the Everglades water budget is evapotranspiration (ET). ET is water removed from the surface and soils by direct evaporation and plant transpiration. In South Florida, ET rates may exceed 40 in/yr (inches per year) on the average; during dry years, the ET could exceed rainfall (about 50 in/yr). Thus, most of the water that falls on the land surface as rainfall is returned to the atmosphere by ET. Despite the importance of ET in the Everglades water budget, our knowledge of ET is, at present, only semi-quantitative. Recent advances in instrumentation and measurement techniques have made it possible to continuously measure ET, so that an accurate evaluation of ET in the Everglades can be made.
In 1995, a study to measure and model ET in the Everglades (fig. 1) was begun as part of the South Florida Ecosystem Program (McPherson and others, 1995). The principle objective of the study is to develop an understanding of ET within the Everglades drainage unit, excluding forested agricultural and brackish environments. To achieve this, a network of eight ET-measurement sites was established, representing the various types of hydrologic and vegetative environments. Continuous measurement of ET at these sites for at least a 2-year period (October 1995 through September 1997) will be used to develop regional models of ET that can be used to estimate ET at other times throughout the Everglades.
This fact sheet describes the basic principles of ET measurement, and the locations and features of the ET stations operated as part of this study.