| In 1932, the Esera river was dammed at the foothills of the Pyrenean External Ranges; since then, sedimentation has
reduced its water storage capacity by a third. This study of the sediments in the Joaquín Costa reservoir has been based on detailed
sedimentological examination and other analysis of mineralogy, grain size distribution and the chemical components of the materials
accumulated at the bottom of the reservoir. Interpretations are based on results from four sediment cores collected at sites representative
of the main environments in the reservoir. Records of known flood events and of reservoir management data have been combined with a
137Cs-derived chronology. Thus, it has been possible to ascribe the sedimentary record at the different reservoir environments to specific
years, as well as some main changes in the facies types and sediment components. This methodology is a first approach to assessing
siltation processes and dynamics in Mediterranean mountain reservoirs.
Keywords: reservoir siltation, mineralogy, sedimentology,sedimentation rates, 137Cs, sediment tracing, mountain reservoir, central Spanish Pyrenees |