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| Titel |
Independent determination of the maximum root zone storage (SuMax) in conceptual models |
| VerfasserIn |
Hongkai Gao, Fabrizio Fenicia, Nutchanart Sriwongsitanon, Sirikanya Saengsawang, Markus Hrachowitz, Shervan Gharari, Hubert Savenije |
| 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 |
250091039
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| Publikation (Nr.) |
 EGU/EGU2014-5305.pdf |
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| Zusammenfassung |
| The maximum root zone storage in the unsaturated zone is an important parameter in most
conceptual hydrological models, although it is known by different terms such as SuMax
(SUPERFLEX), Wmm′ (Xinanjiang/VIC), FC (HBV), and Srmax (Topmodel), x1 (GR4J).
SuMax is not only used for partitioning precipitation into runoff and infiltration under
different soil moisture conditions, but it is also a key variable determining actual
transpiration. Since SuMax at the scale of conceptual models cannot be directly observed, it
is normally determined by calibration. In this study, we propose an approach to estimate it
directly from the observed hydrograph. The approach makes use of the Ripple diagram
(which is traditionally applied in reservoir storage design) to estimate the root zone
depth required for ecosystem to overcome the driest period in the time series. The
assumption is that ecosystem adjust the root depth in a way that they can survive in a
critical dry period. We applied the SUPERFLEX model with the Xinanjiang/VIC
conceptualization for the unsaturated reservoir to represent the spatial variable
rooting depth. The minimum storage requirement derived from Ripple diagram was
subsequently compared to the average maximum root zone storage in the basin obtained
from model calibration. The storage equals SuMax-(1 + β) in agreement with the
beta function spatial distribution over the basin. Eleven catchments in the Upper
Ping River Basin in Northern Thailand have been selected as a case study to test
our hypothesis. The results suggest that the SuMax-(1 + β) indeed represents the
average root zone storage, which is strongly determined by an extreme dry period
in the time series (approximately once in 10 years). Extreme dry year conditions
determine how deep the roots extend into the soil, which can be interpreted as an
approximation of the storage capacity of the unsaturated reservoir in conceptual
hydrological models. This further suggests that the SuMax-(1 + β) can be directly
inferred from data, thereby considerably reducing the feasible parameter space. |
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