Jacob Rubin and Evapotranspiration Research in the U.S. Geological Survey

The USGS has long been involved in evaluating evapotranspiration (ET). Many early studies were conducted to determine water use by riparian vegetation, prompted by the belief that water could be salvaged for other uses by manipulating the vegetation. Through the 1960s, most of these studies used evapotranspirometers--lined tanks filled with native soil and transplanted with the vegetation of interest. By the 1970s, interest in ET salvage waned, due in part to lack of identifiable salvage following eradication of salt cedar from 9,000 hectares of the Pecos River floodplain. Also, results of a water budget study of a reach of the Gila River floodplain indicated only minor ET salvage from salt cedar eradication. Wanting to improve ET science, the USGS reevaluated its program in the early 1970s, with Jake Rubin pushing for adoption of micrometeorological methods. Some were opposed, preferring water-budget methods, but the need for a new approach was tacitly accepted by others. Although implementation faced substantial resistance, Jake vociferously promoted the recruitment of a senior researcher involved with micrometeorological ET methods to speed the process. A substantial effort failed to recruit its target. Nonetheless, results from the Pecos River efforts raised the question: Do salt cedar use less water than estimated, does replacement vegetation use more, or both? A study was begun by in-house personnel, using eddy-correlation techniques, to answer this question. The first such application in remote wild-land environments, the study used equipment developed for the project by a startup company selling micrometeorological products. Instrumentation has advanced greatly since that early study, and much of the impetus for these advancements originated from Jake's insistence upon and support of the use of micrometeorological techniques by the USGS.