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| Titel |
Parameterization of potential evapotranspiration approaches for distributed hydrologic modeling |
| VerfasserIn |
Matthias Zink, Juliane Mai, Matthias Cuntz, Luis Samaniego |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250094907
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| Publikation (Nr.) |
 EGU/EGU2014-10342.pdf |
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| Zusammenfassung |
| Reliable soil moisture products are needed for the estimation of plant available water or
agricultural droughts. For the simulation of hydrological states, e.g. soil moisture, the
estimation of evapotranspiration is crucial since it has the largest contribution to the water
balance besides precipitation. In hydrological modeling the evapotranspiration is usually
estimated based on potential evapotranspiration (PET). The common approaches for PET
estimation and their parameterization are sufficient at the point or field scale for
which they have been developed. But for spatially distributed estimations on the
mesoscale, e.g. 4 km, their robust parameterization is still a challenge in current
research.
The aim of this study is to find scale and location independent parameters for three
different potential evapotranspiration formulations, which are applied in the mesoscale
Hydrologic Model (mHM). PET is estimated using the 1) Hargreaves-Samani, 2)
Priestley-Taylor, and 3) Penman-Monteith equations. The Hargreaves-Samani method is a
temperature driven approach, whereas the other two methods are based on radiation. For
estimating the parameters of the above mentioned PET formulations, the Multiscale
Parameter Regionalization technique is used. This technique accounts for subgrid variabilities
by connecting morphological terrain properties, which are available in a higher resolution
than the model resolution, with the parameters for the particular PET approach. The
parameters, which needed to be estimated, are the coefficient of the Hargreaves-Samani
equation, the Priestley-Taylor coefficient, and the aerodynamic and bulk surface resistance for
the Penman-Monteith equation. The Hargreaves-Samani coefficient is regionalized based on
the aspect of the terrain. The Priestley-Taylor coefficient as well as the aerodynamic and bulk
surface resistance have been estimated using static land cover information combined with leaf
area index (LAI) development curves and thus an approximation for vegetation
information.
This new parameterized PET approaches are evaluated in six different German river
basins ranging from 6,000 km2 to 38,000 km2 including a spatial variety from catchments in
the northern German lowlands to alpine catchments in the south.
The comparison of the results is focusing on evapotranspiration, soil moisture and
discharge. Whereas only slight changes in the discharge hydrograph have been observed in
the comparison of the three PET equations, the impact on soil moisture is significant.
Especially during the summer period the soil moisture is lower for the Priestley-Taylor and
Penman-Monteith formulation compared to the Hargreaves-Samani equation. This effect is
due to higher estimates in PET for those two methods. Furthermore a validation against eddy
covariance measurements showed that the dynamics of evapotranspiration is captured well by
the three methods. |
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