EEF - Peter Donovan - Remote sensing of evapotranspiration can map and chart change in water cycling

We seldom think of the power of the sunlight-driven water cycle, unless we're talking about falling water through a turbine. We don't usually think of the WORK (force times distance, or force against resistance) that it takes to produce ET, that is provided by sunlight, that eventually goes through the turbines at Lower Granite, etc. At constant temp and pressure -- which may not be a good description of actual conditions such as vapor pressure deficit-- it takes roughly 774,000 kilowatt-hours of the sun's work, or about a million horsepower-hours, to produce 1 acre-foot of ET. 

Bottom line: ET is a transformative metric for the WORK of sunlight, and that work feeds everybody, grows spongy soils that can support plants when it doesn't rain every day, produces biodiversity, cools the earth's surface, etc. etc. (Corollary: beavers, and humans, can leverage some BIG horsepower by influencing ET.)

The perspective of energy and work (which is the currency of relationships) helps us cross the chasm from single species management or problem-solving to whole-landscape function.