Land use sediment production response under different climatic conditions in an alpine–prealpine catchment

Abstract

Loss of soil and subsequent export of sediments to streamflows by water erosion constitute significant environmental threats because of the areal extent typically involved and the agricultural activities that they support. Climate change is expected to impact on the availability of water and therefore on soil resources. In this context, hydrological and soil erosion models allow for the mapping and quantifying of soil redistribution and sediment productions for different land uses and climatic scenarios that can be used for valuable projections for catchment management. A simulation experiment was achieved by using the Soil and Water Assessment Tool (SWAT) model in the mountainous catchment of the Barasona reservoir (1509km2, Central Spanish Pyrenees), which is characterized by a heterogeneous climate and topography, that brings it a varied mosaic of soil types and land uses. In order to investigate differences in sediment productions from the land uses under different climatic conditions the sediment produced from the land uses was assessed for two years. 2003 and 2005 were selected to represent contrasted precipitations and wet and dry conditions, respectively. Moreover, the distribution of land uses and climate in the catchment enabled the division of the catchment into two parts which allowed the assessment of the sediment productions in the northern alpine and the southern Mediterranean parts of the catchment. The specific sediment yield varied largely in relation with precipitation, seasons, land use types and catchment parts, from 0 to 243tha−1year−1. Furthermore, according to the prediction of the IPCC and climatic studies for the region an increase of 2°C was simulated to assess the impact on sediment yield. Different responses to the temperature increment were observed between wetter (2003 and northern part) and drier (2005 and southern part) conditions and also for the land use types. Great decreases in sediment production were observed for the 2°C increase scenario in wetter conditions, whereas low decreases with some increments occurred in the drier conditions. The proposed model proved useful for the assessment of the behaviour in sediment production from the land uses under different climatic conditions in large alpine–prealpine catchments at a regional level.