Short-Term Evaporation Estimating From Complex Small Lakes In Arid And Semi-Arid Regions

Abstract

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. 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 air-water surface . The model takes into account advection, oasis effect and stability conditions of ABL in the heat exchange process. To have a precise estimation of evaporation the effects of the terrain surrounding the water body, the water body size and the effects of the available fetch of water body were implemented in the model. The governing equations of the model have been solved by OpenFOAM ; an open source, freely available CFD toolbox and easily extended to run in parallel. The estimated evaporation values were compared against the field measurements and they showed reasonable agreement.