Jake Rubin's Continuing Influence on ET Research In the U.S. Geological Survey

While the Pecos River evapotranspiration (ET) study (1980-82) was the first major project resulting from Jake Rubin's efforts to promote USGS adoption of micrometeorological methods to measure ET, the use of these methods has since grown immensely, largely replacing the earlier emphasis on water-budget methods. This trend accelerated after 1997 with the development of a US-made “waterproof” sonic anemometer. Prior to 1997, ET research was often hampered by the need to replace water-damaged parts after rainfall, before data collection could resume. Consequently, early field campaigns in remote areas typically were limited to days at a time, necessitating frequent site visits to capture seasonal variability. One such USGS National Research Program (NRP) study attempted to quantify the ET salvaged by lowering the water table beneath scrub vegetation in the San Luis Valley, Colorado, during 1985-88. During this same period, NASA and other agencies began tackling the challenge of quantifying ET through remote sensing, and in 1987 held the first in a series of large-scale field experiments, known as FIFE, where legions of micrometeorological flux stations provided ground-truth for airborne and satellite sensors. The USGS NRP played a substantial role in this and ensuing experiments (Monsoon '90, Little Washita, BOREAS) through the mid-1990s. The USGS State District offices also displayed a growing interest in micrometeorological methods during the 1990s, with notable studies in such varied locations as Florida, Nevada, Washington, and New Mexico. In the last ten years, programs in Nevada and Florida have grown substantially, with additional studies occurring in California, Colorado, Nebraska, Oklahoma, Oregon, Tennessee, and Texas. Currently, USGS hydrologic studies involving ET rely heavily on micrometeorological methods. Although some of this reliance is due to recent technological advances, much of the impetus can surely be traced back to Jake Rubin's early advocacy of the methods.