A numerical approach to heat and mass transfer in a large water reservoir is
presented. This water reservoir is likened to a parallelepiped reservoir whose
vertical and lower walls are adiabatic and impermeable. The equations that
govern natural convection in water are solved by the finite volume method
and Thomas’salgorithm. The adequacy between the velocity and pressure
fields is ensured by the SIMPLE algorithm. We are going to evaluate the wa-
ter losses by evaporation from three dams in the Nakanbé basin in Burkina
Faso for a period of thirty years, that is to say from January 1, 1991, to March
15, 2020. The three dams have a rate of evaporation greater than 40% of the
volume of water stored. Indeed the rate of evaporation in each dam increases
with the water filling rate in the reservoir: we have observed the following re-
sults for each dam in the Nakanbé basin; for the date of 02/27/1988 to
03/13/2020., the Loumbila dam received a total volume of stored water of 22.02
Mm3 and 10.57 Mm3 as the total volume of water evaporated at the same date.
At the Ouaga dam (2 + 3), it stored a water volume of 4.06 Mm3 and evaporated
2.03 Mm3 of its storage volume from 01/01/1988 to 05/07/2016. Finally, with
regard to the Bagré dam, it stored 745.16 Mm3 of water and 365.13 Mm3 as the
volume of water evaporated from 01/01/1993 to 03/31/2020.

Numerical Study, Evaporation, Meteorological Data, Natural Convection, Ba- sins