Glossary
Albedo
The fraction of incoming solar radiation reflected by a surface. Open water has a low albedo (about 0.06), so it absorbs most incoming sunlight — one reason open-water net radiation, and thus evaporation, differs from that of brighter vegetated or soil surfaces.
Albedo enters evaporation calculations through net radiation: a darker surface absorbs more energy. Substituting a vegetated albedo for the low open-water value is one reason crop-ET equations over-predict open-water loss.