Abstract:
Past experience on evapotranspiration has provided sound theoretical knowledge and practical applications that have been validated through field measurements. In spite of its ubiquity, the estimation of evapotranspiration at regional scale in currently used models is based on point source information pertaining to meteorological data. This is mainly due to the difficulty involved in measuring it over a large diverse area or lack of spatial information to estimate it. Remote sensing offers a potential means of measuring outgoing fluxes, surface temperature and leaf area index. In this paper, a remote sensing based methodology is presented to estimate regional evapotranspiration. The methodology is based on surface energy balancing and utilizes the digital data in visible and infrared region alongwith the ancillary meteorological data to derive various fluxes involved in the computation. The developed methodology is utilized to estimate regional evapotranspiration using Landsat-TM data for a part of the Western Yamuna Canal (WYC) command in the State of Haryana, India. Results reveal that the error involved in the estimated average evapotranspiration by the proposed methodology is about 10 % as compared to the estimate obtained by using the Penman-Monteith approach for well-watered crop. The methodology described in this paper is computationally stable, and can be used in practice for most real life applications without sacrificing much accuracy.
