The experimental catchments of Arnás and san salvador in the central spanish pyrenees : discharge and sediment transport

Abstract

The experimental catchments of Arnás and San Salvador, located in the Upper Aragón River Basin, have been monitored with a weather station, a flume and instruments to continuously measure the discharge and the sediment carried out (as solutes and suspended sediment). A sediment trap at the flume allows to weight periodically the bedload. The results obtained confirm the existence of great hydrological and geomorphological differences between the forest covered catchment (San Salvador) and the farmland abandoned catchment (Arnás). The former shows a much more moderate response due basically to the process of interception and to a greater soil depth. Relationships between precipitation and peak flow, as well as between this latter and suspended sediment concentration are very low, increasing notoriously if cold season floods are considered isolately. Runoff generation is mainly due to saturation processes. Fi1ially, sediment sources are located in the channel and its closeness.