Long-term fluxes of dissolved and suspended matter in the Ebro River Basin (Spain)

Abstract

Summary The aim of this study was to evaluate, over a long time period, the export fluxes for dissolved and solid matter loads on the catchment scale of the Ebro River Basin in Spain. Data are compiled from the databank of the Confederacion Hidrografica del Ebro (CHE). The spatial and temporal distribution of physical and chemical parameters, suspended particulate matter (SPM) and major elements were investigated in the Ebro Basin upstream in Mendavia and downstream in Tortosa between 1981 and 2004 using the historical databank. The mean interannual dissolved fluxes were estimated to be 1.6 × 106 t year−1 at Mendavia and 5.9 106 × t year−1 at Tortosa respectively, leading to evaluated specific export rates close to 93 t km−2 year−1 at Mendavia and 69 t km−2 year−1 at Tortosa, respectively. The SPM flow related to the specific mechanical erosion rate over the whole basin was around 1.0 × 105 t year−1, providing an estimate of the specific export rates of around 5.1 t km−2 year−1 at Mendavia and 1.2 t km−2 year−1 at Tortosa, thus highlighting the control of solid transport by the numerous dams within the Ebro River Basin. Calculations were also carried out for the respective contribution of carbonate and evaporite (gypsum) with respect to the total dissolved solids (TDS). It appears that the TDS, over the whole catchment scale, is mostly controlled by SO4, Na and Ca concentrations, reflecting the preferential contribution of both evaporite and carbonate dissolution during chemical weathering within the Ebro River Basin.