Modelling Potential Spawning Grounds for Magdalena Basin Potamodromous Fish: A Tier 1 Tool for Environmental Impact Assessment of Hydropower Projects

Abstract

The Magdalena river basin is inhabited by 23 migratory fish species that withstands the artisanal fisheries and migrate upstream from the floodplains habitats in the low lands to the parental river and its tributaries at maximum 1200 m.a.s.l. to spawn. Hydropower development in the north of South America has been focused in Andean rivers. In Colombia, dams have been constructed below 1000 m.a.s.l. since 1990, due to this the conservation of the migratory cycle is a challenge for Colombian environmental institutions, since our economy depends mainly on hydropower. Thus, management measures to promote fish species conservation must promote habitat connectivity. We estimate the spawning areas of 13 migratory fish species using records from CIUA Ichthyological Collection and records obtained from the National Authority of Environmental Licensing (ANLA). Potential spawning areas were determined based on the estimation of water velocity and average flow time of each stream reach in the whole basin, and then based on embryonic and larval time development, we delimited the drainage network. We quantify the potential impact of hydropower development overlapping the location of hydropower projects (in construction and planned). Spawning grounds represented 42,361 km of rivers, including Strahler order from one to eight (41.9% of the 101,110 km of the total network) and overlaps with 80 hydropower projects (56.7% of the total). With this Tier 1 complementary tool it is possible to analyze hydropower development to choose project configurations that minimize impacts related with potential spawning areas in a basin.