Estimation of Evapotranspiration and Water Budget Components Using Continuous Soil Moisture and Water Table Monitoring

Simultaneous measurements of soil moisture (SM) and water table heads were used to estimate evapotranspiration (ET) in a shallow water table environment. The study was conducted in West-Central Florida from January 2002 to June 2004. Frequency Domain Reflectometery (FDR) SM probes, installed in close proximity to water table monitoring wells, were used to derive changes in soil moisture profile. A one dimensional finite difference model was developed and interfaced with integrated SM changes for estimation of vertical and lateral fluxes along the flow domain. Two distinct landuse covers were investigated: grassland and alluvial wetland forest. The average annual ET varied from approximately 850mm to 1,100mm respectively. Quantitative estimates of other components of a water budget, e.g., infiltration, interception capture, total rainfall excess, and runoff were also made on a quarterly and annual basis. Novelty of this approach permitted comprehensive estimate of all ET components and other water budget fluxes.