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| Titel |
A multi-source satellite data approach for modelling Lake Turkana water level: calibration and validation using satellite altimetry data |
| VerfasserIn |
N. M. Velpuri, G. B. Senay, K. O. Asante |
| 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 ; 16, no. 1 ; Nr. 16, no. 1 (2012-01-03), S.1-18 |
| Datensatznummer |
250013108
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| Publikation (Nr.) |
 copernicus.org/hess-16-1-2012.pdf |
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| Zusammenfassung |
| Lake Turkana is one of the largest desert lakes in the world and is
characterized by high degrees of inter- and intra-annual fluctuations. The
hydrology and water balance of this lake have not been well understood due
to its remote location and unavailability of reliable ground truth datasets.
Managing surface water resources is a great challenge in areas where in-situ
data are either limited or unavailable. In this study, multi-source
satellite-driven data such as satellite-based rainfall estimates, modelled
runoff, evapotranspiration, and a digital elevation dataset were used to
model Lake Turkana water levels from 1998 to 2009. Due to the unavailability
of reliable lake level data, an approach is presented to calibrate and
validate the water balance model of Lake Turkana using a composite lake
level product of TOPEX/Poseidon, Jason-1, and ENVISAT satellite altimetry
data. Model validation results showed that the satellite-driven water
balance model can satisfactorily capture the patterns and seasonal
variations of the Lake Turkana water level fluctuations with a Pearson's
correlation coefficient of 0.90 and a Nash-Sutcliffe Coefficient of
Efficiency (NSCE) of 0.80 during the validation period (2004–2009). Model
error estimates were within 10% of the natural variability of the lake.
Our analysis indicated that fluctuations in Lake Turkana water levels are
mainly driven by lake inflows and over-the-lake evaporation. Over-the-lake
rainfall contributes only up to 30% of lake evaporative demand. During
the modelling time period, Lake Turkana showed seasonal variations of 1–2 m.
The lake level fluctuated in the range up to 4 m between the years
1998–2009. This study demonstrated the usefulness of satellite altimetry
data to calibrate and validate the satellite-driven hydrological model for
Lake Turkana without using any in-situ data. Furthermore, for Lake Turkana,
we identified and outlined opportunities and challenges of using a
calibrated satellite-driven water balance model for (i) quantitative
assessment of the impact of basin developmental activities on lake levels
and for (ii) forecasting lake level changes and their impact on fisheries.
From this study, we suggest that globally available satellite altimetry data
provide a unique opportunity for calibration and validation of hydrologic
models in ungauged basins. |
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