Estimation crop Evapotranspiration using Remote Sensing and GIS

What is it about?

Determination of reference evapotranspiration (ET0 ) is a key factor for estimation of crop water requirement, water balance and irrigation scheduling. The FAO-56 Penman–Monteith equation has been accepted universally for estimating of reference evapotranspiration (ET0 ). This method demands a number of climatic parameters that are not always available. The determination of water needed for irrigating crops is one of the main parameters for correct irrigation planning. In this context the FAO Penman – Monteith (FAO– PM) has been recommended as the best for the evapotranspiration (ETo ) estimates. The traditional methods require several meteorological and crop data even for estimation of point ET0 . Remote sensing images have recently been applied to estimate temporal and spatially distributed ET0 very effectively and timely. The determination of actual evapotranspiration of specific crops needs acquisition and routine processing of daily remote sensing images, which seems time consuming and expensive. In present study, daily, monthly, and yearly ETo were determined for 2 stations namely Godhra, and Veganpur located in Panam canal command, middle Gujarat region using long period (11 Year) weather data applying FAO-56 Penman-Monteith and Hargreaves equations. Further, in this study actual ET was estimated using MOD16 remote sensing data. The present study was also undertaken to estimate and compare the crop water requirement (ETc) of maize crops using field methods and remote sensing data based estimation in winter season of Panam command region, Gujarat. The growth stage wise crop coefficients (Kc) taken for daily climatic variation were used to estimate the daily ETc for the maize crops. It was found in this study that remote sensing based data has very similar performance for estimation of ET0 as compared to point estimation using field studies.

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Why is it important?

The motivation behind this research was to attempt a validation of the MOD16 ET product on a regional scale against validated ET maps with the same spatial and temporal resolution.