Abstract:
In this study, remote sensing-based algorithm, METRIC is used to
estimate evapotranspiration (ET) over a mountainous watershed
in the lesser Himalayas in Uttarakhand, India. ET estimates of
METRIC are compared with the ET values determined by using
FAO Penman-Monteith equation and crop coefficients. In its original
form, METRIC underestimated the ET values considerably
with mean absolute error (MAE) of 0.95mm/day. A modification is
incorporated in METRIC for better representation of the effect of
rainfall on the ET process. The proposed modification estimates
ET at the hot pixel using daily rainfall and meteorological data.
Using the modification, the MAE is reduced to 0.44mm/day and
underestimation of ET is reduced from 20.9% to 8.4%. This study
contributes to the better understanding of ET in the lesser
Himalayas of Uttarakhand. It also underlines the importance of
accurate assignment of ET to the hot pixel for accurate estimation
of ET using METRIC.
