EVALUATION OF HARGREAVES BASED ON REMOTE SENSING METHOD TO ESTIMATE POTENTIAL CROP EVAPOTRANSPIRATION

Abstract

In arid and semi-arid regions, agricultural water consumption information is very important to
managing and developing water resources. Potential crop evapotranspiration (ETc) is the major parameter in
agricultural water resources management. Remote sensing techniques were involved in this work to evaluate
Hargreaves method for estimating ETc depending on satellite data. The difference between air temperature
(Tair) and Land Surface Temperature (LST) varies particularly by surface water status. Normalized Difference
Vegetation Index (NDVI) was extracted from NOAA/AVHRR and landsat8 satellite data to calculate
emissivity as an intermediate step for producing LST. Linear relation between Tair and LST was established
and R2 was 0.93. Reference evapotranspiration (ETo) was estimated using agro-meteorological data through
FAO-Penman-Monteith (FPM) which used as standard method and Hargreaves (Har) method. To calibrate
ETo-Har, the ETo-FPM was used under the same conditions. Landsat8 data acquired on 13th of Aug. and 08th of
Aug. 2014 and were used to calculate Crop coefficient (Kc) based on satellite data (Kc-Sat). LST was used to
predict Tair (
o
C) in Aug. 2014. ETo estimated using Har method and was used with Kc-Sat to estimate ETc-Har.
ETo-FPM combined with Kc-Sat to estimate ETc-FPM. ETc-FPM used to evaluate ETc-Har. The relation between ETcFPM and ETc-Har was very strong where R2 as high as 0.99. In arid and semi-arid regions, agricultural water consumption information is very important to
managing and developing water resources. Potential crop evapotranspiration (ETc) is the major parameter in
agricultural water resources management. Remote sensing techniques were involved in this work to evaluate
Hargreaves method for estimating ETc depending on satellite data. The difference between air temperature
(Tair) and Land Surface Temperature (LST) varies particularly by surface water status. Normalized Difference
Vegetation Index (NDVI) was extracted from NOAA/AVHRR and landsat8 satellite data to calculate
emissivity as an intermediate step for producing LST. Linear relation between Tair and LST was established
and R2 was 0.93. Reference evapotranspiration (ETo) was estimated using agro-meteorological data through
FAO-Penman-Monteith (FPM) which used as standard method and Hargreaves (Har) method. To calibrate
ETo-Har, the ETo-FPM was used under the same conditions. Landsat8 data acquired on 13th of Aug. and 08th of
Aug. 2014 and were used to calculate Crop coefficient (Kc) based on satellite data (Kc-Sat). LST was used to
predict Tair (oC) in Aug. 2014. ETo estimated using Har method and was used with Kc-Sat to estimate ETc-Har.
ETo-FPM combined with Kc-Sat to estimate ETc-FPM. ETc-FPM used to evaluate ETc-Har. The relation between ETcFPM and ETc-Har was very strong where R2 as high as 0.99.