Assessing the potential effect of different land cover management practices on sediment yield from an abandoned farmland catchment in the Spanish Pyrenees

Abstract

Purpose Sediment delivery from headwater catchments to reservoirs is a serious threat to reservoir sustainability and is a critical issue in Mediterranean environments where water resources are scarce. In this study we assessed the consequences of two landscape management scenarios (natural vegetation recovery and scrub clearance) on soil erosion and sediment yield. The results were analyzed in relation to predicted and measured rates of soil erosion and sediment yield, with the aim of promoting better management practices. Materials and methods The study area was the Arnás River catchment (284 ha), which is located in the central Spanish Pyrenees; the area includes abandoned and poorly managed fields. The combination of the RUSLE and SEDD models of soil erosion and sediment delivery was evaluated in terms of its ability to predict annual rates of sediment yield, using field measurement data for seven water years at the gauging station. The consequences of natural plant succession in other areas of the Spanish Pyrenees and scrub clearance practices implemented by certain regional governments to increase grazing meadow areas and reduce the incidence of wildfires were spatially analyzed using GIS. The main sediment source areas were identified, and their specific and total sediment yields were calculated. Results and discussion The predicted soil loss under existing conditions was 2.6 Mg ha −1 year −1 , with 5% of the surface area affected by rates greater than 2 Mg. The measured sediment yield range was 69-534 Mg year −1 . The maximum sediment yield detected was associated with an extraordinary debris flow. The predicted rates were strongly correlated to measured rates (Nash-Sutcliffe coefficient= 0.72). The main sources were alluvial deposits [specific sediment yield (SSY)=51 Mg ha −1 year −1 ], bare soil (SSY= 12), unpaved trails (SSY=11), lots (SSY=4), and pastures (SSY=1). Under a scenario of vegetation recovery, decreases of 3%, 17%, and 16% in soil loss and sediment delivery and yield (respectively) are predicted, whereas increases of 15%, 5%, and 2% are predicted following scrub clearance practices. Conclusions Coupling the RUSLE and SEDD models enabled estimation of annual values of soil erosion and sediment delivery in monitored and unmonitored catchments of small and medium size, making this approach a useful tool for risk analysis. Management practices that combine fire-risk control, by the implementation of scrub clearance practices, with the effects of plant succession on sediment production are suggested as the best management strategy.

Integrating Extensive Livestock and Soil Conservation Policies in Mediterranean Mountain Areas for Recovery of Abandoned Lands in the Central Spanish Pyrenees. A Long‐Term Research Assessment

“…Nevertheless, experiences in other Spanish regions suggested that the clearing of shrubs in abandoned fields increases livestock potential, improves the quality of the landscape and reduces the risk of fire because of the creation of a mosaic of vegetation and topography that breaks the homogeneity that is a feature of the slopes of abandoned fields (Lasanta et al ., , , ). On the other hand, the application of predictive models in a small experimental catchment characterized by abandoned land in the Spanish Pyrenees (Arnás catchment), covered by shrubs and small forest areas, showed that clearing shrubs for conversion into grazing meadows would simply increase the erosion rates (López‐Vicente et al ., ).…”

Comparing catchment sediment fingerprinting procedures using an auto-evaluation approach with virtual sample mixtures

“…4) was not unexpected due to changes in land uses that occurred in the past century. This reflects likely succession states between former agricultural areas that are partly reverting to natural forests after land abandonment (e.g., López-Vicente et al, 2011) which could contribute to overlapping source data. Also the influence of similar lithological characteristics of the three overlapping points from forest source with those from the agricultural source may also account for the lack of discrimination between these two sources.…”

Evolución morfo-sedimentaria del tramo medio del río Segre

“…En este contexto cabe señalar los efectos de los cambios de los usos del suelo en la cuenca sobre la producción de sedimentos y generación de escorrentía, tal y como indican numerosos trabajos en España en diferentes contextos hidroclimáticos (por ej. Beguería et al, 2006;García-Ruíz, 2010;López-Vicente et al, 2011;Sanchis-Ibor y Segura-Beltrán, 2014). De especial interés además es el estudio de los efectos de la regulación de los caudales por embalses, sobre todo en un contexto climático mediterráneo, donde las presas son un elemento clave en la gestión de los recursos hídricos superficiales.…”