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Estimation of Actual Evapotranspitration by Remote Sensing

S. A. Kadam, S. D. Gorantiwar, S. N. Das and A. K. Joshi

As evapotranspiration is one of the main components of hydrologic cycle, its estimation is very important. Remote sensing technologies can assist to improve the estimation accuracy also providing means for computing evapotranspiration geographical distribution. In the present study, the daily actual evapotranspiration was calculated for wheat crop in Rabi season during the crop growth cycle uniformly. FAO Penman-Monteith method adapted to satellite data was used for the estimation of actual crop evapotranspiration for wheat crop using satellite data together with ground meteorological measurements. Satellite data, following the necessary processing, were used in conjunction with surface data from the nearest meteorological station. The IRS LISS-III satellite images were used to calculate, albedo NDVI and LAI required for the estimation of actual crop evapotranspiration (ETc) for wheat crop. The actual crop evapotranspiration for wheat crop varied from 0.95 to 3.43 mm/day during the crop growth period. The ETc values estimated from satellite data by direct application of FAO Penman Monteith method are on an average 16.54% lower than ETc values estimated as multiplication of Kc from lysimeter data and ETr from meteorological data. It is obvious that ETc sourcing from IRS LISS-III and meteorological data is always less than that of the FAO. The reason for this could be the low resolution of IRS LISS-III pixel. The difference is insignificant, when both the values were compared with t-test for paired two sample means.