Graduation Year

2006

Document Type

Dissertation

Degree

Ph.D.

Degree Granting Department

Civil Engineering

Major Professor

Mark A. Ross, Ph.D.

Keywords

West Central Florida, Vadose zone hydrology, Shallow water table, Potential ET, Groundwater ET

Abstract

A new methodology is proposed for estimation of evapotranspiration (ET) flux at small spatial and temporal scales. The method involves simultaneous measurement of soil moisture (SM) profiles and water table heads along transects flow paths. The method has been applied in a shallow water table field site in West-Central Florida for data collected from January 2002 through June 2004. Capacitance shift type moisture sensors were used for this research, placed at variable depth intervals starting at approximately 4 in. (10 cm) below land surface and extending well below the seasonal low water table depth of 59 in. (1.5 m). Vegetation included grassland and wetland forested flatwoods. The approach includes the ability to resolve multiple ET components including shallow and deep vadose zone, surface interception capture and depression storage ET. Other components of the water budget including infiltration, total and saturation rainfall excess runoff, net runoff, changes in storage and lateral groundwater flows are also derived from the approach. One shortcoming of the method is the reliance on open pan or other potential ET estimation techniques when the water table is at or near land surface. Results are compared with values derived for the two vegetative covers from micrometeorological and Bowen ratio methods. Advantages of the SM method include resolving component ET.

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