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| Titel |
Swath-altimetry measurements of the main stem Amazon River: measurement errors and hydraulic implications |
| VerfasserIn |
M. D. Wilson, M. Durand, H. C. Jung, D. Alsdorf |
| 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. 4 ; Nr. 19, no. 4 (2015-04-22), S.1943-1959 |
| Datensatznummer |
250120692
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| Publikation (Nr.) |
 copernicus.org/hess-19-1943-2015.pdf |
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| Zusammenfassung |
| The Surface Water and Ocean Topography (SWOT) mission, scheduled for launch
in 2020, will provide a step-change improvement in the measurement of
terrestrial surface-water storage and dynamics. In particular, it will
provide the first, routine two-dimensional measurements of water-surface
elevations. In this paper, we aimed to (i) characterise and illustrate in
two dimensions the errors which may be found in SWOT swath measurements of
terrestrial surface water, (ii) simulate the spatio-temporal sampling scheme
of SWOT for the Amazon, and (iii) assess the impact of each of these on
estimates of water-surface slope and river discharge which may be obtained
from SWOT imagery. We based our analysis on a virtual mission for a
~260 km reach of the central Amazon (Solimões) River,
using a hydraulic model to provide water-surface elevations according to SWOT
spatio-temporal sampling to which errors were added based on a
two-dimensional
height error spectrum derived from the SWOT design requirements. We thereby
obtained water-surface elevation measurements for the Amazon main stem as may
be observed by SWOT. Using these measurements, we derived estimates of river
slope and discharge and compared them to those obtained directly from the
hydraulic model. We found that cross-channel and along-reach averaging of
SWOT measurements using reach lengths greater than 4 km for the
Solimões and 7.5 km for Purus reduced the effect of systematic height
errors, enabling discharge to be reproduced accurately from the water height,
assuming known bathymetry and friction. Using cross-sectional averaging and
20 km reach lengths, results show Nash–Sutcliffe model efficiency values of
0.99 for the Solimões and 0.88 for the Purus, with 2.6 and 19.1 %
average overall error in discharge, respectively. We extend the results to
other rivers worldwide and infer that SWOT-derived discharge estimates may be
more accurate for rivers with larger channel widths (permitting a greater
level of cross-sectional averaging and the use of shorter reach lengths) and
higher water-surface slopes (reducing the proportional impact of slope errors
on discharge calculation). |
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