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| Titel |
Predictions of rainfall-runoff response and soil moisture dynamics in a microscale catchment using the CREW model |
| VerfasserIn |
H. Lee, E. Zehe, M. Sivapalan  |
| 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 ; 11, no. 2 ; Nr. 11, no. 2 (2007-02-05), S.819-849 |
| Datensatznummer |
250009218
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| Publikation (Nr.) |
 copernicus.org/hess-11-819-2007.pdf |
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| Zusammenfassung |
| Predictions of catchment hydrology have been performed generally using
either physically based, distributed models or conceptual lumped or
semi-distributed models. In recognition of the disadvantages of using either
of these modeling approaches, namely, detailed data requirements in the case
of distributed modeling, and lack of physical basis of conceptual/lumped
model parameters, Reggiani et al. (1998, 1999) derived, from first
principles and in a general manner, the balance equations for mass, momentum
and energy at what they called the Representative Elementary Watershed (or
REW) scale. However, the mass balance equations of the REW approach include
mass exchange flux terms which must be defined externally before their
application to real catchments. Developing physically reasonable "closure
relations" for these mass exchange flux terms is a crucial pre-requisite
for the success of the REW approach. As a guidance to the development of
closure relations expressing mass exchange fluxes as functions of relevant
state variables in a physically reasonable way, and in the process
effectively parameterizing the effects of sub-grid or sub-REW heterogeneity
of catchment physiographic properties on these mass exchange fluxes, this
paper considers four different approaches, namely the field experimental
approach, a theoretical/analytical approach, a numerical approach, and a
hybrid approach combining one or more of the above. Based on the concept of
the scaleway (Vogel and Roth, 2003) and the disaggregation-aggregation
approach (Viney and Sivapalan, 2004), and using the data set from Weiherbach
catchment in Germany, closure relations for infiltration, exfiltration and
groundwater recharge were derived analytically, or on theoretical grounds,
while numerical experiments with a detailed fine-scale, distributed model,
CATFLOW, were used to obtain the closure relationship for seepage outflow.
The detailed model, CATFLOW, was also used to derive REW scale
pressure-saturation (i.e., water retention curve) and hydraulic
conductivity-saturation relationships for the unsaturated zone. Closure
relations for concentrated overland flow and saturated overland flow were
derived using both theoretical arguments and simpler process models. In
addition to these, to complete the specification of the REW scale balance
equations, a relationship for the saturated area fraction as a function of
saturated zone depth was derived for an assumed topography on the basis of
TOPMODEL assumptions. These relationships were used to complete the
specification of all of the REW-scale governing equations (mass and momentum
balance equations, closure and geometric relations) for the Weiherbach
catchment, which are then employed for constructing a numerical watershed
model, named the Cooperative Community Catchment
model based on the Representative Elementary
Watershed approach (CREW). CREW is then used to carry out
sensitivity analyses with respect to various combinations of climate, soil,
vegetation and topographies, in order to test the reasonableness of the
derived closure relations in the context of the complete catchment response,
including interacting processes. These sensitivity analyses demonstrated
that the adopted closure relations do indeed produce mostly reasonable
results, and can therefore be a good basis for more careful and rigorous
search for appropriate closure relations in the future. Three tests are
designed to assess CREW as a large scale model for Weiherbach catchment. The
first test compares CREW with distributed model CATFLOW by looking at
predicted soil moisture dynamics for artificially designed initial and
boundary conditions. The second test is designed to see the applicabilities
of the parameter values extracted from the upscaling procedures in terms of
their ability to reproduce observed hydrographs within the CREW modeling
framework. The final test compares simulated soil moisture time series
predicted by CREW with observed ones as a way of validating the predictions
of CREW. The results of these three tests, together, demonstrate that CREW
could indeed be an alternative modelling framework, producing results that
are consistent with those of the distributed model CATFLOW, and capable of
ultimately representing processes actually occurring at the larger scale in
a physically sound manner. |
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