I couldn't help adding some engineering calculations to this discussion.
To calculate heat gain / loss, you would need to take into consideration the
1. Heat loss due to evaporation. This will be impacted by the surface wave action as this impacts the film layer evaporation due to surface layer humidity.
2. Heat loss due to convection.
3. Heat gain due to short wave radiation (UV solar gain)
4. Heat loss due to long wave radiation (IR losses to the atmosphere)
5. Heat gain due to fresh water additions.
6. Conduction losses to the surrounding ground.
Using the 1st law of thermodynamics,
dH/dt= sigma(Qin-Qout)
you could calclate the heat losses, but this would still only be a guess.
