The energy transferred from the water by the energy for evaporation equals:
where is the specific heat capacity of water (cal/gm/°C) and is an arbitrarily chosen base temperature, in general 0 degrees Celsius, while is the latent heat of vaporization (590 cal/gm).
Re-combining the first two equations, we obtain:
with incoming solar radiation and reflected solar radiation and net long wave radiation from the water body to the atmosphere, net energy advected into the lake by flows of water, change of energy storage in the lake. R is the Bowen Ratio.
As the total amount of energy used for evaporation is:
where is the density , evaporation from an open water surface can be expressed in terms of the energy balance components and conditions at the lake surface:
References Dunne, T. & Leopold, L. B. (1978). Water in Environmental Planning. New York: Freeman and Company.