Glossary
Reference Evapotranspiration
The evapotranspiration from a standardised, well-watered grass surface — the reference used by FAO-56. It is not the same as open-water evaporation and must be adapted before it represents a reservoir.
Reference ET is a vegetated-surface concept with its own albedo and surface resistance. Applying it directly to open water over-predicts loss; the albedo and resistance terms must be substituted first.