Hydrochemical budget of a Mediterranean mountain basin in relation to land use (The Ribera Salada, Catalan Pre-Pyrenees, NE spain)

摘要

The objective of this study is to predict the risk of surface water degradation under changing land use in representative basins of the Catalonian Pre-Pyrenees. Surface water was monitored in the Ribera Salada basin (222.5 km(2)) fortnightly between June 1999 and June 2000, and in four subcatchments (2.6 km(2) to 62.5 km(2)) following a mixed nested/paired catchment fieldwork design. Two hundred water samples were analyzed using Ion-Capillary Electrophoresis. The chemistry of surface waters was controlled by ions derived from the dissolution of CaCO3 and gypsum of the substrate, with additional dilution effect of Na+, NO3- and Cl- during periods of high discharge. The Total Dissolved Solid load ranged from 145 kg ha(-1) to 1920 kg ha(-1). No significant relation was found between chemical concentrations and discharge. The forest along the river network absorbs the N released from pastures and crops. Under the present land management there is no risk of attaining critical levels of N in surface waters (50 mg l(-1)) all over the area. However, despite of the high quality of the water, it is necessary to control land uses on the catchment to avoid water degradation in the future.