ABSTRACT
This term includes the total net short wave radiation over the free surface, that is to say, the difference between the radiation received and emitted. (It has been directly measured).
Net long wave absorbed radiation
The long wave radiation received can be calculated by the StefanBoltzmann law. Taking into acount the value of the physical parameters involved, it can be expressed as:
where TA is the temperature of the air (K)
Long wave emitted radiation
The long wave radiation emitted by the river can also be evaluated by the Stefan-Boltzmann law:
where Ts is the water temperature on the free surface (K)
Heat loss by evaporation
Taking into account the expression obtained by Seco and Garmendia [2]:
where:
Heat loss by conduction
It is possible to reach a proportionality between heat conduction to the atmosphere and heat loss by evaporation. This proportionality is known as Bowen's ratio; using the expression obtained for the evaporation:
Heat exchanged with the subgrade
The subgrade in the bed of the river has an important contact surface with the water: there is a heat exchange across this surface, with a large amount of thermal energy (Miller [3]).
