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Communication dans un congrès

Dissolved load transport in the Ebro River Basin (Spain): Impact of main lithologies and role of tributaries

Abstract : This study aims to evaluate, over more than 20 years, the export fluxes for dissolved loads at the Ebro River catchment scale. Data are compiled from the of the Confederacion Hidrografica del Ebro (CHE) databank. The spatial and temporal distribution of daily discharges, physico-chemical parameters and chemical data covering the last two decades (1981-2003) were investigated on five monitoring stations along the Ebro River (Mendavia, Castejon, Zaragoza, Sastago and Tortosa), as well as six stations at the outlet of the main tributaries (Arga, Aragon, Gallego, Jalon, Cinca and Segre). The dissolved load of the rivers at the Ebro Basin scale was characterized through the Electrical Conductivity (EC), total dissolved solids (TDS) and the major elements chemical data. The surface water can be classified into three main categories, a clear dominance of Ca-SO4 water type, a Ca-HCO3 type mainly encountered in the upper part of the basin and some data presenting a Na-Cl water type. The TDS values are highly variable, both in time and in space, in the range 390-1360 mg/L. The dissolved exportations to the Mediterranean Sea and the relative contribution of the different tributaries were calculated. The Ebro basin in its upper part (upstream Mendavia) contributes around 22.4% of the total exported flux near the outlet (Tortosa) over the studied period. The tributaries that mainly contribute to the total exported dissolved load are the Cinca and Segre (19% and 17% respectively). The Aragon, Gallego and Jalon contributions are very low, often less than 5% of the total exported flux. The specific TDS flux at the outlet of the Ebro is 70 +/- 23 t/km2/year and 108 +/- 24 t/km2/year upstream in Mendavia while the highest chemical erosion rate was calculated for the Arga with 251 +/- 55 t/km2/year. The dissolved export fluxes represent the major export from the Ebro basin, and the respective contribution of carbonate and evaporite (gypsum) with respect to the TDS was then calculated using the major element concentrations and discharge data. In the upper part of the Ebro Basin, carbonate weathering is dominant compared to gypsum weathering while downstream the dissolved exportations are dominated by gypsum weathering. For the tributaries, most of them are dominated by evaporite weathering. The exportation rates at the outlet of the watershed shows dissolved exportation derived from gypsum weathering, that are about 1.5 times that derived from carbonate weathering
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Communication dans un congrès
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https://hal-brgm.archives-ouvertes.fr/hal-00738253
Contributeur : Emmanuelle Petelet-Giraud <>
Soumis le : mercredi 3 octobre 2012 - 18:37:06
Dernière modification le : jeudi 23 avril 2020 - 12:24:47

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  • HAL Id : hal-00738253, version 1

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Citation

Emmanuelle Petelet-Giraud, Philippe Négrel. Dissolved load transport in the Ebro River Basin (Spain): Impact of main lithologies and role of tributaries. AGU Fall Meeting, Dec 2012, San Francisco, United States. pp.H31B-1110. ⟨hal-00738253⟩

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