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| Titel |
Integration of vegetation indices into a water balance model to estimate evapotranspiration of wheat and corn |
| VerfasserIn |
F. L. M. Padilla, M. P. González-Dugo, P. Gavilán, J. Domínguez |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1027-5606
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| Digitales Dokument |
URL |
| Erschienen |
In: Hydrology and Earth System Sciences ; 15, no. 4 ; Nr. 15, no. 4 (2011-04-12), S.1213-1225 |
| Datensatznummer |
250012747
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| Publikation (Nr.) |
 copernicus.org/hess-15-1213-2011.pdf |
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| Zusammenfassung |
| Vegetation indices (VIs) have been traditionally used for quantitative
monitoring of vegetation. Remotely sensed radiometric measurements of
visible and infrared solar energy, which is reflected or emitted by plant
canopies, can be used to obtain rapid, non-destructive estimates of certain
canopy attributes and parameters. One parameter of special interest for
water management applications, is the crop coefficient employed by the
FAO-56 model to derive actual crop evapotranspiration (ET). The aim of this
study was to evaluate a methodology that combines the basal crop coefficient
derived from VIs with a daily soil water balance in the root zone to
estimate daily evapotranspiration rates for corn and wheat crops at field
scale. The ability of the model to trace water stress in these crops was
also assessed. Vegetation indices were first retrieved from field hand-held
radiometer measurements and then from Landsat 5 and 7 satellite images. The
results of the model were validated using two independent measurement
systems for ET and regular soil moisture monitoring, in order to evaluate the
behavior of the soil and atmosphere components of the model. ET estimates were
compared with latent heat flux measured by an eddy covariance system and
with weighing lysimeter measurements. Average overestimates of daily ET of 8
and 11% were obtained for corn and wheat, respectively, with good
agreement between the estimated and measured root-zone water deficit for
both crops when field radiometry was employed. When the satellite sensor
data replaced the field radiometry data the overestimation figures slightly
changed to 9 and 6% for the same two crops. The model was also used to
monitor the water stress during the 2009 growing season, detecting several
periods of water stress in both crops. Some of these stresses occurred
during stages like grain filling, when the water stress is know to have a
negative effect on yield. This fact could explain the lower yield reached
compared to local yield statistics for wheat and corn. The results showed
that the model can be used to calculate the water requirements of these
crops in irrigated areas and that its ability to monitor water stress
deserves further research. |
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