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| Titel |
Modeling and sediment study in the watershed Medjerda, Tunisia |
| VerfasserIn |
Fatma Kotti, Gil Mahe, Hamadi Habaieb, Claudine Dieulin, Taoufik Hermassi |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250108206
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| Publikation (Nr.) |
 EGU/EGU2015-7948.pdf |
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| Zusammenfassung |
| Water projects have experienced a major expansion in the late 1980s, and we now have
sufficient perspective to assess their actual performance and their socio-environmental
impacts (Payan, 2007). This study focuses on the great watershed of Tunisia namely
Medjerda which has an area of about 23,600 km2. In the main river of Medjerda some dams
have been created for water retention: Sidi Salem Dam (the largest in the country), El
Aroussia dam, and others on tributaries Mellegue Bouhertma, Siliana, Beni Mtir,
Lakhemess and Kasseb. Since the construction of dams, essentially Sidi Salem and
Siliana, the Medjerda river has undergone significant changes in morphology. The
monitoring of the flow of the major hydrological stations in the pre-estuarine zone
downstream from Sidi Salem dam is used to measure the impact of the constructions on
hydrological regimes: reduction in average rates, reduction in volumes sold, altered
seasonal pattern, and most of all reduction of the sediment transport, which the
highest values are related to extreme events. In this context, the balance of sediment
monitoring appears indispensable for the quantification of sediment transport at the
outlet.
Our approach is to calculate a specific flow rate relative to the area of the basin for every
structure built in the Medjerda watershed, from the information available on transport and
sedimentation rates known, combined with contours of each sub watershed. There are about
ten dams spread throughout Medjerda watershed. The methodology is primarily developed
for the Mellegue dam because we have at this station a long data set from 1955 until 2005.
Other stations will be studied later on. The main objective of this study is to provide a series
of annual variation of theoretical contributions. These calculated values will be compared
with the actual measured sedimentary series. Two cores in the sediments of the
pre-estuarine area are performed to determine past variability in sediment inputs
over a time series than should be about one century. The cores’ analysis results
show a succession of sedimentary layers that likely correspond to different flood
deposits that succeeded on this site, and especially the datation of the cores shows that
the selected area is a very important deposition area. This sedimentary study will
help estimate the sediment dynamics to major estuaries, which is poorly known for
most of the rivers of Maghreb. The reduction of the sediment supply to the sea is
tipped as a major factor to be taken into account for a better understanding of the
dynamics of coastal areas in the context of global climate change and sea level
rise.
Keywords: sediment core, Medjerda watershed, dam, hydrology, modeling, Tunisia |
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