Reducing the Vulnerability of Societies to Water Related Risks at the Basin Scale (Proceedings of the third International Symposium on Integrated Water Resources Management, Bochum, Germany, September 2006). IAHS Publ. 317, 2007, 123–129.

Impounded rivers: aridification and geomorphological risks

CARMEN DE JONG

The Mountain Institute, University of Savoie, F-73376 Le Bourget du Lac Cedex, France

carmen.dejong@institut-montagne.org

Abstract Within Integrated Water Resources Management, river impound­ment by large dams is rarely considered in terms of aridification and geo­morphological risks. Since transdisciplinary impacts of dams are not analysed with holistic approaches a diversity of problems remains untouched. The lifetime of a dam progresses unavoidably from its juvenile into mature stage ending with its final decay. Impacts include those upstream, within and downstream of reservoirs and as far as terminal lakes and coasts. In semi-arid regions aridification downstream of dams is a major cause of salinization or total desiccation of inland wetlands, lakes and deltas. Geomorphological risks are a function of sediment transport, stability of reservoir slopes and sediment trapping within the reservoir. Reduction in reservoir capacity finally causes the reservoir to be abandoned. The environmental and economic costs of hydrological and geomorphological change such as channel incision, degradation of flood plains or loss of coastal beaches should be considered in future Integrated Water Resources Management programmes.

Key words aridification; China; coastal; dams; geomorphological; Morocco; sedimentation; upstream–downstream