Water and sediment yield in two representative Mediterranean catchments under different land uses in the Catalan Coastal Ranges

Abstract

The objectives of the research are to assess the impact of forestry and agriculture land uses in runoff, storm runoff and water quality in a Mediterranean mountain environment. The study area is located in the North end of the Catalan Coastal Ranges. The research is based on the monitoring of two small nested catchments, Bosc under forestry and Campàs under forestry and agriculture. Data has been collected since 1993 but the records are not always continuous. While variability of the parameters is high in both catchments, mean discharges may be estimated in 6 l/s in the forested catchment and in 8 l/s in the forest and agricultural catchment which generates mean runoff coefficients around 8 %, in Bosc and on 9 % in Campàs. Hydrological response to rainfall after summer drought is not produced until November or December and runoff lasts until April or May. Floods may represent up to 80% of total water volume throughout the year, with a maximum of 469 l/s en Bosc and of 879 l/s in Campàs. The impact of agricultural practices is more consistent in solutes concentration, which may vary from 105 mg/l up to 152 mg/l. Suspended material has a higher irregular response depending on especific anthropic actions (ploughing and track’conservation), reaching concentrations up to 0.75 mg/l and yielding 4.3 kg/ha/yr in Campàs and 2,5 kg/ha/yr in Bosc. It is in the Campàs where the agricultural fields and mjor number of tracks are located.