Combining catchment modelling and sediment fingerprinting to assess sediment dynamics in a Spanish Pyrenean river system

The elevated supply and transfer of sediment in river systems can impact on water resource infrastructure, water quality and ecosystem health around the world. Moreover, the loss of reservoir capacity clue to siltation is of particular concern in regions that experience water scarcity, such as the Mediterranean. Therefore, quantifying the sediment production from contributing catchments to reservoirs is of major interest to support the development of management plans for maintaining reservoir sustainability. Within this context, sediment production from a catchment in the central Spanish Pyrenees was investigated by combining the outputs of the Soil and Water Assessment-Tool (SWAT) model with sediment source fingerprinting. The study examined the large alpinepreal pine catchment of the Barasona reservoir, which is an agroforest catchment supplying sediment to the reservoir at an annual rate of around 35 t ha(-1). For the period 2003-2005 the simulated specific sediment yields for the catchment by SWAT model are mostly below 2 t ha(-1) year(-1) with maximum values reaching 250 t ha(-1) year(-1). Simulated sediment production is dependent on (i) land use/cover, (ii) precipitation amounts and (iii) slope gradients. The highest sediment yield was simulated for the badlands, in the wettest year and for the greatest slope gradients. The predicted catchment source contributions obtained for the reservoir sediments were low (<7%) for forest and scrubland sources, greater for agricultural sources and exceeded 50% for subsoil sources. Results from both procedures indicate that badlands are the main sediment source while agricultural land is of secondary importance. This combination of procedures allowed catchment sediment production and source contributions to be linked to reservoir infilling. It also demonstrates the benefits of combined modelling and sediment fingerprinting approaches in complex catchments where siltation threatens water and energy security. (C) 2016 Else B.V. All rights reserved.