Introduction

Abstract

The main concern of this book is the evaporation of water in the natural environment. In general, evaporation is the phenomenon by which a substance is converted from the liquid or solid state into vapor. In the case of a solid substance, the phenomenon is often referred to as sublimation. The vaporization of water through the stomata of living plants is called transpiration. Over land transpiration from vegetation and direct evaporation from the soil and small water surfaces are difficult to separate in computations; therefore these two terms are often combined in the term evapotranspiration. All these distinctions are useful at times; however, the term evaporation is usually adequate to cover all processes of vaporization, unless specified otherwise.