Large-scale impacts of hydropower development on the Mompós Depression wetlands, Colombia

Abstract

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. Annual large-scale inundation of floodplains and associated wetlands regulates water-, nutrient-, and sediment cycles, which in turn sustain a wealth of ecological processes and ecosystem services, including critical food 15 supplies. In this study, we present a comparative analysis of the potential effects of hydropower expansion to meet projected electricity requirements by 2050, in terms of 1) basin-level implications of cumulative changes in streamflow regime, sediment trapping, and loss of river connectivity, and 2) the impact of upstream regulation on the hydrologic dynamics of the Mompós Depression wetlands at a monthly to decadal scale. To this end, we developed an enhancement of the Water Evaluation and Planning system (WEAP) that allows resolution of the Mompós Depression floodplains water balance at a 20 medium scale (~1000 to 10 000 km 2 ) and evaluation of the potential impacts of upstream water management practices. Our results indicate that 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. In some 25 development scenarios, the amount of water regulated and withheld by upstream infrastructure is of similar magnitude to existing fluxes involved in the episodic inundation of the floodplain during dry periods and, thus, can also induce substantial changes in floodplain seasonal dynamics of average-to-dry years in some areas of the Mompós Depression.

Is Overfishing the Main or Only Factor in Fishery Resource Decline? The Case of The Magdalena River Fishery and Its Correlation with Anthropic Pressures

“…Considering this context, we propose that the habitat loss, the blockage of migratory routes and the loss of connectivity associated with the fragmentation of corridors between flood plains, have altered and are still altering the reproductive habitat as well as the fish recruitment and, consequently, fishing production. This is aligned with what has also been discussed and published by various authors (14,(34)(35)(36)(37)(38) for similar systems. When evaluating gold production as a proxy for mercury pollution, we consider that the intensive extraction that took place in the late 80s, led to a prolonged impact (contamination), as the accumulation in the sediments and bioaccumulation in the food chain continued to affect fish populations in later periods.…”

Effects of selective fishing on a small scale multi-species and multi-gear freshwater fishery in the Magdalena River Basin (Colombia)

“…We are aware that the main current factor of pressure on fishery production is the environmental degradation reported for the basin by Restrepo and Restrepo (2005); Garzón and Gutiérrez (2013); Angarita et al (2018); however, this study was conducted in view of the need for research that questions the effects of selective fishing. The first hypothesis is that selective fishing had ecological impacts on fish populations, affecting the dynamics of fish production in the Basin, and the second is that fishermen responded successfully to changes in fishery production.…”