Modeling of Sediment Transportation in Ichkeul Lake for the Estimation of the Influence of the Constructions of the Reservoirs in the Upper Streams
Rich ecosystems such as estuaries and brackish lakes are vulnerable to the effects of human activities and are prone to environmental changes. In particular, the salt environment, which is the backbone of the environment, might be affected not only by direct modifications such as dredging but also i...
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MDPI AG
2022-06-01
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| Series: | Water |
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| Online Access: | https://www.mdpi.com/2073-4441/14/13/1984 |
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| author | Mitsuteru Irie Hirotoshi Kotegawa Atsushi Kawachi Hajel Ouni Jamila Tarhouni |
| author_facet | Mitsuteru Irie Hirotoshi Kotegawa Atsushi Kawachi Hajel Ouni Jamila Tarhouni |
| author_sort | Mitsuteru Irie |
| collection | DOAJ |
| description | Rich ecosystems such as estuaries and brackish lakes are vulnerable to the effects of human activities and are prone to environmental changes. In particular, the salt environment, which is the backbone of the environment, might be affected not only by direct modifications such as dredging but also in ways that were not initially envisioned. Ichkeul Lake, located in the northern part of Tunisia, is a shallow brackish lake registered as a UNESCO World Natural Heritage Site. The construction of reservoirs upstream of the inflowing river in the 1980s reduced the amount of freshwater inflow. That only had been thought to be the cause of the increase in salinity in Ishkeul Lake. On the other hand, the sedimentation in the reservoirs upstream was remarkable, and the supply of sediment from the reservoirs upstream to the Ichkeul Lake was stopped. Changes in sediment outflow may have reduced lakebed altitude and enhanced seawater intrusion. However, the environmental protection measures for the lake so far have focused only on improving the water budget and have not been quantitatively evaluated for sediment transportation. In this study, we first estimated the water budget of the lake. Then the re-suspension by wind disturbance in the lake was estimated from the correlation with the wind speed based on laboratory experiments and field measurements. The outflow of the sediment estimated with these two models was compared with the sediment volume trapped in the upstream reservoirs that would have flowed into the lake if there had been no construction of the dams. Based on this, we evaluated whether the lake is currently erosive or cumulative. As a result, the estimated annual outflow of sediment to the sea was 4300 tons/year. It was estimated that the construction of the reservoirs upstream changed the trend of lakebed height from accumulation to erosion. |
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| institution | Directory Open Access Journal |
| issn | 2073-4441 |
| language | English |
| last_indexed | 2024-03-09T10:24:30Z |
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| series | Water |
| spelling | doaj.art-a2ee0aab64bc4e00b7684ecc9732f4972023-12-01T21:45:04ZengMDPI AGWater2073-44412022-06-011413198410.3390/w14131984Modeling of Sediment Transportation in Ichkeul Lake for the Estimation of the Influence of the Constructions of the Reservoirs in the Upper StreamsMitsuteru Irie0Hirotoshi Kotegawa1Atsushi Kawachi2Hajel Ouni3Jamila Tarhouni4Faculty of Engineering, University of Miyazaki, Miyazaki 889-2192, JapanMaeda Construction Co., Ltd., Tokyo 102-8151, JapanToken C.E.E. Consultant, Tokyo 170-0004, JapanInstitut National Agronomique de Tunisie, Université de Carthage, Tunis 1082, TunisiaInstitut National Agronomique de Tunisie, Université de Carthage, Tunis 1082, TunisiaRich ecosystems such as estuaries and brackish lakes are vulnerable to the effects of human activities and are prone to environmental changes. In particular, the salt environment, which is the backbone of the environment, might be affected not only by direct modifications such as dredging but also in ways that were not initially envisioned. Ichkeul Lake, located in the northern part of Tunisia, is a shallow brackish lake registered as a UNESCO World Natural Heritage Site. The construction of reservoirs upstream of the inflowing river in the 1980s reduced the amount of freshwater inflow. That only had been thought to be the cause of the increase in salinity in Ishkeul Lake. On the other hand, the sedimentation in the reservoirs upstream was remarkable, and the supply of sediment from the reservoirs upstream to the Ichkeul Lake was stopped. Changes in sediment outflow may have reduced lakebed altitude and enhanced seawater intrusion. However, the environmental protection measures for the lake so far have focused only on improving the water budget and have not been quantitatively evaluated for sediment transportation. In this study, we first estimated the water budget of the lake. Then the re-suspension by wind disturbance in the lake was estimated from the correlation with the wind speed based on laboratory experiments and field measurements. The outflow of the sediment estimated with these two models was compared with the sediment volume trapped in the upstream reservoirs that would have flowed into the lake if there had been no construction of the dams. Based on this, we evaluated whether the lake is currently erosive or cumulative. As a result, the estimated annual outflow of sediment to the sea was 4300 tons/year. It was estimated that the construction of the reservoirs upstream changed the trend of lakebed height from accumulation to erosion.https://www.mdpi.com/2073-4441/14/13/1984sediment transportationresuspensionbrackish lakewater budgetSWAT |
| spellingShingle | Mitsuteru Irie Hirotoshi Kotegawa Atsushi Kawachi Hajel Ouni Jamila Tarhouni Modeling of Sediment Transportation in Ichkeul Lake for the Estimation of the Influence of the Constructions of the Reservoirs in the Upper Streams Water sediment transportation resuspension brackish lake water budget SWAT |
| title | Modeling of Sediment Transportation in Ichkeul Lake for the Estimation of the Influence of the Constructions of the Reservoirs in the Upper Streams |
| title_full | Modeling of Sediment Transportation in Ichkeul Lake for the Estimation of the Influence of the Constructions of the Reservoirs in the Upper Streams |
| title_fullStr | Modeling of Sediment Transportation in Ichkeul Lake for the Estimation of the Influence of the Constructions of the Reservoirs in the Upper Streams |
| title_full_unstemmed | Modeling of Sediment Transportation in Ichkeul Lake for the Estimation of the Influence of the Constructions of the Reservoirs in the Upper Streams |
| title_short | Modeling of Sediment Transportation in Ichkeul Lake for the Estimation of the Influence of the Constructions of the Reservoirs in the Upper Streams |
| title_sort | modeling of sediment transportation in ichkeul lake for the estimation of the influence of the constructions of the reservoirs in the upper streams |
| topic | sediment transportation resuspension brackish lake water budget SWAT |
| url | https://www.mdpi.com/2073-4441/14/13/1984 |
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