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| Titel |
Estimation of crop water requirements: extending the one-step approach to dual crop coefficients |
| VerfasserIn |
J. P. Lhomme, N. Boudhina, M. M. Masmoudi, A. Chehbouni |
| 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 ; 19, no. 7 ; Nr. 19, no. 7 (2015-07-30), S.3287-3299 |
| Datensatznummer |
250120772
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| Publikation (Nr.) |
 copernicus.org/hess-19-3287-2015.pdf |
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| Zusammenfassung |
| Crop water requirements are commonly estimated with the
FAO-56 methodology based upon a two-step approach: first a reference
evapotranspiration (ET0) is calculated from weather variables with the
Penman–Monteith equation, then ET0 is multiplied by a tabulated
crop-specific coefficient (Kc) to determine the water requirement
(ETc) of a given crop under standard conditions. This method has been
challenged to the benefit of a one-step approach, where crop
evapotranspiration is directly calculated from a Penman–Monteith equation,
its surface resistance replacing the crop coefficient. Whereas the
transformation of the two-step approach into a one-step approach has been
well documented when a single crop coefficient (Kc) is used, the case of
dual crop coefficients (Kcb for the crop and Ke for the soil) has
not been treated yet. The present paper examines this specific case. Using a
full two-layer model as a reference, it is shown that the FAO-56 dual crop
coefficient approach can be translated into a one-step approach based upon a
modified combination equation. This equation has the basic form of the
Penman–Monteith equation but its surface resistance is calculated as the
parallel sum of a foliage resistance (replacing Kcb) and a soil surface
resistance (replacing Ke). We also show that the foliage resistance,
which depends on leaf stomatal resistance and leaf area, can be inferred
from the basal crop coefficient (Kcb) in a way similar to the
Matt–Shuttleworth method. |
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