Case Study on the Accuracy and Cost/Effectiveness in Simulating Reference Evapotranspiration in West-Central Florida

The objective of this study was to conduct an accuracy and cost/effectiveness analysis of various reference evapotranspiration (ETo) estimation equations that rely solely upon the collection of meteorological data. A meteorological station was established in an open grassland near Ft. Meade, Florida. The ASCE Penman-Montieth (PM) equation (full ASCE-PM equation) was set as the standard to which nine variants of five equations were compared. The number of parameters that had to be measured for each equation ranged from five (full ASCE-PM equation) to one (Hargreaves equation). ETo was calculated on daily time steps. A variant of the ASCE-PM equation with solar radiation, wind speed, relative humidity, and temperature measured and the Simple equation with only solar radiation measured were most accurate and cost/effective. The most accurate and cost/effective alternative equations were those in which some of the less-important energy and mass-transfer terms were omitted and/or calculated from less-expensive instrumentation. The Simple equation instrumentation required only 33% of the cost of the full ASCE-PM, while only reducing the effectiveness by similar to 10%. With the Simple equation's minimal data requirements and superior accuracy and cost/effectiveness, the Simple equation could be a viable tool for the estimation of ETo in situations where funding is limited.