Improvement of hydrological behaviour of lakes along the Canal del Dique in Colombia for ecological restoration

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Eisse Wijma, Harm Nomden, Marius Sokolewicz

Monday 29 june 2015

17:42 - 17:45h at Europe 1 & 2 (level 0)

Themes: (T) Hydro-environment, (ST) Ecohydraulics and ecohydrology, Poster pitches

Parallel session: Poster pitch: 3G. Environment - Ecohydraulic

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The Canal del Dique is a man-made connection between the Magdalena River and the Caribbean Sea near Cartagena in Colombia. The Canal was developed by creating permanent connections between the Magdalena River and a cascade of marshes and lakes towards the sea. The Magdalena River has a very high suspended sediment load which is partly diverted to the Canal del Dique. At high stages, Canal’s banks are overflowed, with sediments creating natural dikes along the Canal and small deltas in the lakes and marshes. The original Canal as created in 17th century had a more or less a meandering pattern. Large scale works in the 20th century were carried out cutting most of the meander bends, creating a nearly straight, prismatic canal. With the straightening and widening of the Canal, more water from the Rio Magdalena could flow into Canal del Dique, leading to a dramatic increase of sediments transported to the Bay of Cartagena and causing (sometimes catastrophic) floods. Continuous reinforcements of the dikes caused isolation of lakes and marshes. This has subsequently led to great ecological losses due to conversion of land use from wetland to agriculture. Isolation of lakes (cut off from water supply) and dike breaching by local farmers to enhance sedimentation in lakes are used to gain land at the cost of the environment. The project “Environmental restoration of Canal del Dique” aims at improving the conditions in the Canal del Dique for flood protection, sediment management, ecology, navigation while reducing salt water intrusion. Different alternatives for the restoration of the system were developed. Restoration of the original hydrological behaviour of lakes is one of the most important tasks of the project. An important ecological parameter for restoration is the so-called ‘elasticity’, the ability of the lake to vary in both surface and water depth as a result of flooding and drying during the year. This elasticity was strongly reduced in the last 30 years, leading to environmental detoriation. The elasticity was determined after detailed assessment of the hydrological behaviour of lakes and marshes using extensive 1D and 2D hydraulic modelling, field data collection, analysis of satellite imagery, aerial photographs and historical maps. This presentation shows the results of the assessment of the hydrological behaviour of lakes along the Canal del Dique and discusses various restoration measures.