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| Titel |
Historical impact of water infrastructure on water levels of the Mekong River and the Tonle Sap system |
| VerfasserIn |
T. A. Cochrane, M. E. Arias, T. Piman |
| 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. 11 ; Nr. 18, no. 11 (2014-11-17), S.4529-4541 |
| Datensatznummer |
250120526
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| Publikation (Nr.) |
 copernicus.org/hess-18-4529-2014.pdf |
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| Zusammenfassung |
| The rapid rate of water infrastructure development in the Mekong Basin is a
cause for concern due to its potential impact on fisheries and downstream
natural ecosystems. In this paper, we analyze the historical water levels of
the Mekong River and Tonle Sap system by comparing pre- and post-1991 daily
observations from six stations along the Mekong mainstream from Chiang Saen
(northern Thailand), to Stung Treng (Cambodia), and the Prek Kdam station on the
Tonle Sap River. Observed alterations in water level patterns along the
Mekong are linked to temporal and spatial trends in water infrastructure
development from 1960 to 2010. We argue that variations in historical
climatic factors are important, but they are not the main cause of observed
changes in key hydrological indicators related to ecosystem productivity.
Our analysis shows that the development of mainstream dams in the upper
Mekong Basin in the post-1991 period may have resulted in a modest increase
of 30-day minimum levels (+17%), but significant increases in fall rates
(+42%) and the number of water level fluctuations (+75%) observed in
Chiang Saen. This effect diminishes downstream until it becomes negligible
at Mukdahan (northeast Thailand), which represents a drainage area of over
50% of the total Mekong Basin. Further downstream at Pakse (southern
Laos), alterations to the number of fluctuations and rise rate became
strongly significant after 1991. The observed alterations slowly decrease
downstream, but modified rise rates, fall rates, and dry season water levels
were still quantifiable and significant as far as Prek Kdam. This paper
provides the first set of evidence of hydrological alterations in the Mekong
beyond the Chinese dam cascade in the upper Mekong. Given the evident
alterations at Pakse and downstream, post-1991 changes could also be directly
attributed to water infrastructure development in the Chi and Mun basins of
Thailand. A reduction of 23 and 11% in the water raising and falling
rates respectively at Prek Kdam provides evidence of a diminished Tonle Sap
flood pulse in the post-1991 period. Given the observed water level
alterations from 1991 to 2010 as a result of water infrastructure
development, we can extrapolate that future development in the mainstream
and the key transboundary Srepok, Sesan, and Sekong sub-basins will have an
even greater effect on the Tonle Sap flood regime, the lower Mekong
floodplain, and the delta. |
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