Investigation of Temporal and Spatial Variation of Evapotranspiration by Remote Sensing in Semi-Arid Regions

Document Type : Research Paper

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Abstract

Accurate estimation of evapotranspiration plays an important role in
quantification of the water balance at regional scale for better planning
and managing water resources. Evapotranspiration can be obtained from
either estimation of potential ET using data of meteorological stations or,
directly, from field measurements. ET is subject to rapid changes in time
and space, attributable to the wide spatial variability of precipitation,
hydraulic characteristics of soils, and vegetation types and densities.
Therefore, it is nearly impossible to determine its spatial and temporal
distributions over large areas only from lysimeter and precise measuring
instruments. Thus, researchers have used remote sensing data to estimate
areal actual ET. In this study, actual evapotranspiration variations of
Neyshabour plain was investigated by algorithm of energy balance of the
earth since 2000 to 2013 by using MODIS images and meteorological
data. Also, the determined evapotranspiration was compared and evaluated
with Penman-Monteith and Hargreaves-Samani models. Low amount of
coefficients of the error between Penman-Monteith model and SEBAL
algorithm showed the accuracy of SEBAL model in the estimation of
evapotranspiration and its parameters. The results derived from
comparison of evapotranspiration and NDVI vegetation index indicated a
good correlation between vegetation and evapotranspiration (R2=0.908).
Also, the variations of NDVI index, land surface temperature, and
evapotranspiration in the studied fields showed that evapotranspiration
increased by lower land surface temperature and higher densities of
vegetation.

Keywords

Journal of Water Research in Agriculture
Volume 29, Issue 2 - Serial Number 2
August 2015
Pages 221-234

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