Spatial variability of the sediment transport in the headwater catchment of the Aragón river

Abstract

The Aragón river was dammed at the foothills of the Pyrenean Inner Depression in 1959. Since then sediments are accumulated and its initial water storage capacity has been reduced. In this work, a study of the transport of sediments in the hydrological network of the Aragón river catchment until the Yesa reservoir has been undertaken based on the sampling of surface waters in 44 sites representative of the main subcatchments of the Aragón river. Three surveys were carried out in winter and summer. Total suspended sediments, electrical conductivity as an expression of dissolved solids content and pH were analysed in the water samples. Records of discharges at gauging stations of the water authorities were used as controls. The highest concentrations of suspended sediments occur during the winter sampling in the Esca river (54.4 mg l -1) and also after the storm events during the summer sampling in the headwaters of the Aragón river (21.7 mg l -1). The estimation of the dissolved solids indicates that the transport of materials in solution is much lower (0.08 - 0.25 mg l -1) than the suspended sediment load. The results provide information on the features of the transport of suspended and dissolved materials across the basin. The role played by lithology, vegetation cover, land use and drainage characteristics in the transport of sediments is examined for the different periods of sampling. Information gained with this research can be of interest as the headwater catchments in mountain areas are the main sources of water to lowlands. The knowledge on the process of sediment transport can be applied for the management of water bodies to prevent reservoir siltation.