In many parts of the world, the available water resources are now being used close to their limits. Global climate change, the increasing population of the earth and ever-increasing standards of living and consequent growing demand of water are bringing water sustainability into sharp focus. Evaporation as a major component of the hydrologic cycle, is the largest one of water loss from lakes especially in arid and semi-arid regions. Because of lacking of understanding of the thermodynamics of atmospheric boundary layer(ABL) and heat exchange between the water surface and atmosphere, an accurate estimation of evaporation from water surfaces is almost unknown. It is thus of major importance to have precise estimation of the amount of this undesirable, unrecoverable and unproductive water loss from water body for a good management of available water resources. However, most of the models so far described in the literature are one-dimensional with areal homogeneity assumption and can be used for long-term estimations. These models do not account for advection, the sideways movement of energy which results from differing energy and aerodynamic performance of differing land/water surfaces[4]. In arid and semi-arid regions such as Ghana, it is clear that the evaporation of a small shallow lake will be heavily influenced by hot dry air blowing from land upwind of the dam and therefore the large proportion of advected energy may be expected. Many parameters affect the evaporation from a body of water such as a lake to the surrounding air; these are the temperature of the water, size of the water body, the terrain surrounding the water body that affects the air flow over the lake surface, surface roughness of the water body, the air temperature, velocity and humidity. To account for all these parameters, the process of estimating the evaporation becomes very involved[3]. In the framework of this study, a numerical approach was developed to predict evaporation from shallow and small lakes in (semi-) arid regions considering the heat and water vapor exchanges process between the airwater surface.

Keywords