Hydrological foretelling uncertainty evaluation of water balance components and sediments yield using a multi-variable optimization approach in an external Rif's catchment. Morocco

Sedimentary and aquatic dynamics are currently causing major environmental problems in the Mediterranean countries, water and soil resources are steadily decreasing over time. Therefore, simulation and estimation of flows and sediments have currently a direct implication in the sustainable management of water and soils. In the present study, a Mediterranean watershed (North-West of Morocco) was benefited from the functionalities of Hydrological Model SWAT, version 2012 (semi-distributed and physically based), by adopting a monthly simulation. The main objective of this study is to calibrate and validate the SWAT model in the Arbaa Ayacha watershed (18,854 ha) between 1980 and 2000 by a multi-objective optimization approach using the Sufi-2 algorithm of the SWAT-CUP program. The performance of the model was tested using three objective functions NSE, PBIAS and R2, while the sensitivity analysis of the model was performed by adjusting 19 parameters of sensitivities related to flow rates and sediment concentrations. The results obtained are satisfactory with a significant correlation between the observed and simulated values of variables flow and sediments. The results also show that evapotranspiration and surface runoff are predominante in the basin compared to the other components of the water balance, while the sediment yield was estimated at 28.09 t/ha/year. Since the model is validated in the study area, it will later be used to simulate the evolution of scenarios based on climate change and land use. It will also help to determine the best managment practices in the watershed.