A number of large hydropower dams are currently under development or in an advanced stage of planning in the Magdalena River basin, Colombia, spelling uncertainty for the Mompós Depression wetlands, one of the largest wetland systems in South America at 3,400 km.

Annual large-scale inundation of floodplains and their associated wetlands regulates water, nutrient, and sediment cycles, which in turn sustain a wealth of ecological processes and ecosystem services, including critical food supplies. This study implements an integrated approach focused on the key attributes of ecologically functional floodplains, to provide an explicit quantification of the nonlinear or direct response relationship of those considerations with hydropower development.

A number of hydropower dams are under development in Colombia’s Magdalena River. Photo: Flickr/Erik Cleves Kristensen

This proposed framework was used to develop a comparative analysis of the potential effects of the hydropower expansion necessary to meet projected 2050 electricity requirements. The study included an enhancement of the Water Evaluation and Planning System (WEAP).

For the Mompós Depression wetlands, the results indicate that the potential additional impacts of new hydropower infrastructure with respect to baseline conditions can range up to one order of magnitude between scenarios that are comparable in terms of energy capacity. Fragmentation of connectivity corridors between lowland floodplains and upstream spawning habitats and reduction of sediment loads show the greatest impacts, with potential reductions of up to 97.6 and 80 %, respectively, from pre-dam conditions.