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| Titel |
Sensitivity of simulated global-scale freshwater fluxes and storages to input data, hydrological model structure, human water use and calibration |
| VerfasserIn |
H. Müller Schmied, S. Eisner, D. Franz, M. Wattenbach, F. T. Portmann, M. Flörke, P. Döll |
| 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 ; 18, no. 9 ; Nr. 18, no. 9 (2014-09-10), S.3511-3538 |
| Datensatznummer |
250120464
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| Publikation (Nr.) |
 copernicus.org/hess-18-3511-2014.pdf |
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| Zusammenfassung |
| Global-scale assessments of freshwater fluxes and storages by hydrological
models under historic climate conditions are subject to a variety of
uncertainties. Using the global hydrological model WaterGAP (Water – Global Assessment and Prognosis) 2.2, we
investigated the sensitivity of simulated freshwater fluxes and water
storage variations to five major sources of uncertainty: climate forcing,
land cover input, model structure/refinements, consideration of human water
use and calibration (or no calibration) against observed mean river
discharge. In a modeling experiment, five variants of the standard version
of WaterGAP 2.2 were generated that differed from the standard version only
regarding the investigated source of uncertainty. The basin-specific
calibration approach for WaterGAP was found to have the largest effect on
grid cell fluxes as well as on global AET (actual evapotranspiration) and discharge into oceans for the
period 1971–2000. Regarding grid cell fluxes, climate forcing ranks second
before land cover input. Global water storage trends are most sensitive to
model refinements (mainly modeling of groundwater depletion) and
consideration of human water use. The best fit to observed time series of
monthly river discharge or discharge seasonality is obtained with the
standard WaterGAP 2.2 model version which is calibrated and driven by daily
reanalysis-based WFD/WFDEI (combination of Watch Forcing Data based on ERA40
and Watch Forcing Data based on ERA-Interim) climate data. Discharge computed by a calibrated
model version using monthly CRU TS (Climate Research Unit time-series) 3.2 and
GPCC (Global Precipitation Climatology Center) v6 climate input reduced the
fit to observed discharge for most stations. Taking into account
uncertainties of climate and land cover data, global 1971–2000 discharge
into oceans and inland sinks ranges between 40 000 and 42 000 km3 yr−1.
Global actual evapotranspiration, with 70 000 km3 yr−1, is rather unaffected by climate and land cover
uncertainties. Human water use reduced river discharge by 1000 km3 yr−1,
such that global renewable water resources are estimated to range
between 41 000 and 43 000 km3 yr−1. The climate data sets WFD
(available until 2001) and WFDEI (starting in 1979) were found to be
inconsistent with respect to shortwave radiation data, resulting in
strongly different actual evapotranspiration. Global assessments of
freshwater fluxes and storages would therefore benefit from the development
of a global data set of consistent daily climate forcing from 1900 to present. |
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