the conversion of water, whether surface water, soil moisture (both by evaporation), or within plants (by transpiration) into water vapor that is released to the atmosphere —note potential evapotranspiration can be estimated from simplified heat energy considerations of readily measured meteorological phenomena; actual evapotranspiration may be the result of various factors, e.g., restricted water supplies or plant physiological processes modifying that potential This definition last updated 07/31/2008