WSES-2-Evaporation from water bodies and its control

Abstract

Evaporation of water has an important role in the hydrologic cycle of nature. It is a natural process and occurs when solar radiation falls on a water body and the energy so transmitted is acquired by water molecules which in turn get separated and move upward causing the evaporation phenomenon. The loss of water from water storage structures like reservoirs, irrigation tanks through the process of evaporation causes considerable reduction in storage. The huge costs involved in the construction of these storage structures make it imperative to utilise every single drop of water stored. Estimation of evaporation loss in the country indicate that the annual evaporation from a water surface in the semi-arid tropics is as high as 2000 mm. Annual average value of evaporation ranges from 1400 mm to 1800 mm over a large portion of the country. More information about spatial variation of evaporation reveals that values exceeding 2000 mm occur over west Rajasthan and parts of Saurashtra and Tamilnadu, while less than 1400 mm is reported at coastal Mysore, Bihar plateau and east M.P.