Evaporation from a water body is driven by the vapor pressure gradient between the water surface and the overlying air, and can be estimated three ways: direct pan measurement (scaled to lake evaporation by an empirical pan coefficient, since pan evaporation systematically exceeds lake evaporation due to differences in heat storage, exposure, and boundary effects), empirical equations relating evaporation to vapor pressure deficit and wind speed, or theoretical mass/energy balance equations. The theoretical water-budget equation conserves mass over a water body (inflows minus outflows minus storage change equals evaporation), while the theoretical energy-budget equation conserves energy at the water surface (net radiation minus sensible heat, transferred via the Bowen ratio, minus ground/storage/advected heat terms equals the energy consumed by evaporation). This belongs to engineering hydrology, specifically the sub-area of the hydrologic cycle concerned with quantifying evaporation and evapotranspiration losses.
Evaporation from a water body is driven by the vapor pressure gradient between the water surface and the overlying air, and can be estimated three ways: direct pan measurement (scaled to lake evapora…