Dynamics of riparian vegetation as impacted by sedimentation in reservoirs

Riparian vegetation along the rivers is one of the ways that allows restoration of surface water quality, stabilizing the banks, reducing erosion risks and offering habitat to flora and fauna. The modification of these ecosystems affects sediment transport and deposition in rivers. Sediments retained in a reservoir suggest an impact on the dynamics of the erosion processes and on the equilibrium of riparian ecosystems. If this tendency continues, it will not only affect the generation of electricity, but it will also impact ecosystems, either due to the excess of sediments or to lack of them. This paper analyzes the dynamics of the riparian ecosystems, upstream and downstream of “El Caracol”, a hydroelectric dam located in Guerrero, Mexico, based on Landsat TM and ETM + images corresponding to early spring (March-April) for the period of 1984-2010. The analysis was established by mapping the dynamics of the NDVI as an indicator of the areas affected by the migration of the vegetation and the erosion of the margins. The results show a decrease in NDVI in the study period. While degraded areas have a negative NDVI trend, there are areas within the same reservoir, where the index increases, indicating an increase in sediment deposition being an important factor in explaining vegetation migration.