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| Titel |
Effects of hydrologic conditions on SWAT model performance and parameter sensitivity for a small, mixed land use catchment in New Zealand |
| VerfasserIn |
W. Me, J. M. Abell, D. P. Hamilton |
| 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. 10 ; Nr. 19, no. 10 (2015-10-13), S.4127-4147 |
| Datensatznummer |
250120824
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| Publikation (Nr.) |
 copernicus.org/hess-19-4127-2015.pdf |
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| Zusammenfassung |
| The Soil Water Assessment Tool (SWAT) was configured for the Puarenga Stream
catchment (77 km2), Rotorua, New Zealand. The catchment land use is
mostly plantation forest, some of which is spray-irrigated with treated
wastewater. A Sequential Uncertainty Fitting (SUFI-2) procedure was used to
auto-calibrate unknown parameter values in the SWAT model. Model validation
was performed using two data sets: (1) monthly instantaneous measurements of
suspended sediment (SS), total phosphorus (TP) and total nitrogen (TN)
concentrations; and (2) high-frequency (1–2 h) data measured during
rainfall events. Monthly instantaneous TP and TN concentrations were
generally not reproduced well (24 % bias for TP, 27 % bias for TN, and
R2 < 0.1, NSE < 0 for both TP and TN), in contrast to SS
concentrations (< 1 % bias; R2 and NSE both > 0.75)
during model validation. Comparison of simulated daily mean SS, TP and TN
concentrations with daily mean discharge-weighted high-frequency
measurements during storm events indicated that model predictions during the
high rainfall period considerably underestimated concentrations of SS
(44 % bias) and TP (70 % bias), while TN concentrations were comparable
(< 1 % bias; R2 and NSE both ~ 0.5). This comparison highlighted the potential for
model error associated with quick flow fluxes in flashy lower-order
streams to be underestimated compared with low-frequency (e.g. monthly)
measurements derived predominantly from base flow measurements. To address
this, we recommend that high-frequency, event-based monitoring data are
used to support calibration and validation. Simulated discharge, SS, TP and
TN loads were partitioned into two components (base flow and quick flow)
based on hydrograph separation. A manual procedure (one-at-a-time
sensitivity analysis) was used to quantify parameter sensitivity for the two
hydrologically separated regimes. Several SWAT parameters were found to
have different sensitivities between base flow and quick flow. Parameters
relating to main channel processes were more sensitive for the base flow
estimates, while those relating to overland processes were more sensitive
for the quick flow estimates. This study has important implications for
identifying uncertainties in parameter sensitivity and performance of
hydrological models applied to catchments with large fluctuations in stream
flow and in cases where models are used to examine scenarios that involve
substantial changes to the existing flow regime. |
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