Evaluation of hydrology, suspended sediment and Nickel loads in a small watershed in Basque Country (Northern Spain) using eco-hydrological SWAT model

Suspended sediment transportation and associated pollutants from catchment to stream networks are responsible for aquatic habitat degradation, reservoir sedimentation and the transportation of sediment bound pollutants. Quantifying suspended sediment loads from lands to watercourses is essential in controlling soil erosion and in implementing appropriate mitigation practices to reduce stream sediment and associated pollutant loads, and hence improve surface water quality downstream.The main objective of this study is to evaluate the temporal variability of hydrology, sediment and nickel loads using Soil and Water Assessment Tool in Oka watershed located in north Spain. Model simulation was completed using 11 years historical records (2001-2009 for validation and 2009-2012 for calibration) of streamflow and suspended sediment concentration (SSC). Thestreamflow, SSC and sediment load estimated from the model were compared with observed data using statistical parameters, which indicates a successful simulation. The annual production of simulated sediments shows variability between 662 and 1515 t, with a mean specific yield of 33 t km(-2) y(-1). The annual load of nickel simulated ranged from 32 to 72 kg, representing a mean specific of 1.63 kg km(-2) year(-1). The information obtained from this research is of interest to understand long term interannual variability of suspended sediment and nickel yield.