Evapotranspiration

Drylands are arid and semi-arid zones around the world where water resources are scarce. In the U.S., 40 percent of the land is considered dryland. USGS scientists are researching how predicted climate changes in dryland ecosystems--increases in temperature and declines in precipitation--will affect vegetation and wildlife in these areas as well as the ecosystem services they provide.

The Colorado River supplies water to more than 30 million people, irrigates nearly 4 million acres of cropland in the U.S. and Mexico, and supplies hydropower plants that generate more than 10 billion kilowatt-hours annually. Water from the river also provides for recreation and an array of environmental benefits, supporting a wide diversity of fish and wildlife and their habitats, and preserving...

The USGS EROS approach to ET estimation allows the quantification of ET at two important scales: (1) field and (2) hydrologic basin. Field-scale ET is used for water use estimation to understand and quantify where, by whom, and how much water is being used in the landscape. On the other hand, basin-scale ET assists in understanding basin water balance and water availability.