Estimation of Evapotranspiration from Wetlands Using Geospatial and Hydrometeorological Data

Over recent decades, wetlands have been recognized increasingly for their high biodiversity and for the important hydrological functions, including flood alleviation, low-flow support, nutrient cycling and groundwater recharge (Thakur, 2010; Thakur et al., 2011). Wetland hydrology is a primary driving force influencing wetland ecology, its development and persistence (Mitsch and Gosselink, 1993). For most wetlands, evapotranspiration (ET) is the major component of water loss, and when considered as its energy equivalent, the latent heat flux (LE), the largest consumer of incoming energy (Reynolds et al., 2000; Wilson et al., 2001). The radiation and the turbulent heating drive the dynamics of the land-atmosphere energy exchanges in the wetlands. Estimation of these radiation and turbulent heating through mass energy balance equations is the core of numerical weather forecast, climate research, water resources and environmental management and long-term agriculture production. Most of the conventional methods which use point measurement in measuring the energy balance, such as Bowen ratio, Penman-Monteith, Priestley and Taylor, give results that can be efficient on local level but could not be extended to large scale or global scale measurement in time and space (Stewart, 1989).