Use of a calibrated SWAT model to evaluate the effects of agricultural BMPs on sediments of the Kalaya river basin (North of Morocco)

Abstract

Soil erosion from agricultural fields is a worldwide problem, to influence water quality, soil fertility and reservoir sedimentation especially in Mediterranean countries such as Morocco. In fact, this work assesses the effects of Best Management Practices (BMPs) on sediments using the Soil and Water Assessment Tool (SWAT) model in the Kalaya watershed in Northern Morocco, to recommend the most appropriate practice. This study is based on the use of three most usable practices: contouring, strip-cropping and terracing, by the calibrated SWAT model. The general parameters of the model have been modified to reflect the implementation of different agricultural BMPs used. Resulting sediment yield were compared with the baseline scenario, for validation. However, the effective measures to reduce sediment losses at the watershed level are organized according to their effectiveness, and these are terracing (28% reduction and the value is 15t/ha/yr) followed by strip-cropping (9% reduction and the value is 5t/ha/yr). In contrast, measurements performed by the contouring are inappropriate for the study area because they have contributed to increasing the soil erosion (more than 31% of losses and the value is 17t/ha/yr more than existing conditions). Therefore, the model illustrates that the terrace is effective for reducing sediment losses and limiting soil erosion especially on steep slopes. Thus, the results provide useful information for targeted management in order to implement the most effective agricultural BMPs in the watershed. Keywords: Modeling, Agricultural BMPs, Sediment, SWAT, Kalaya river basin, North Morocco