ORIGINAL PAPER SWAT manual calibration and parameters sensitivity analysis in a semi-arid watershed in North-western Morocco Youssef Brouziyne 1 & Aziz Abouabdillah 2 & Rachid Bouabid 2 & Lahcen Benaabidate 1 & Ons Oueslati 2 Received: 3 March 2017 /Accepted: 21 September 2017 # Saudi Society for Geosciences 2017 Abstract Being a laborious approach, manual calibration of hydrologic model in a semi-arid context requires in-depth knowledge of the watershed and as much as possible field input data to obtain reliable simulations. In this study, manual calibration and relative sensitivity analysis approaches of the SWAT model (Soil and Water Assessment Tool) were applied for water balance in a 1993 km 2 watershed (on the R’dom river) located in North-western Morocco. The watershed is located in a semi-arid area dominated by agro-forestry activ- ities. The objectives of this study were (i) to perform a local sensitivity analysis of the SWAT model taking into consider- ation the watershed characteristics and (ii) to implement a detailed methodology of manual calibration and validation of the model in a semi-arid context. Sensitivity analysis has been carried out on 12 different SWAT input parameters, and has revealed that 4 input parameters only were the most influ- ential ones on flow components of the R’dom watershed. Model manual calibration was conducted along 2006 and 2007 by comparing measured and predicted monthly and dai- ly discharges and taking Nash-Sutcliffe coefficient (NSE), de- termination coefficient (R 2 ), and percent bias (PBIAS) as goodness-of-fit indicators. Validation has been performed by the same approach through 2008 and 2009 period. All final NSE values were above 0.5, R 2 values exceeded 0.7, and PBIAS lower than 25% demonstrating satisfactory model per- formances over the study watershed conditions. The SWAT model set-up with measured input data, manually calibrated and validated, reflects well the real hydrologic processes oc- curring in the R’dom watershed and can be used to assess current and future conditions and to evaluate alternative man- agement practices. Keywords Sensitivity analysis . Manual calibration . R’dom watershed . SWAT model Introduction In nowadays circumstances, the challenges of environmental management under climate change impacts have made more urgent the need to make technological progress and scientific research results more accessible and ready for use. Proper monitoring, analysis, and management of natural resources (especially water) require the implementation of joined multi- disciplinary approach, in order to come out with rational strat- egies and applied policies for better management scenarios (Cau et al. 2015). With the development of computing technologies, mathe- matical modeling tools are oriented for simulation of environ- mental phenomena that are characterized by considerable complexity and high level of integration. These tools are often supposed to estimate parameters and require significant * Youssef Brouziyne brouziyne@gmail.com Aziz Abouabdillah aabouabdillah@enameknes.ac.ma Rachid Bouabid rbouabid@enameknes.ac.ma Lahcen Benaabidate benaabidate@yahoo.fr Ons Oueslati onsoueslati@yahoo.fr 1 Laboratory of Georesources and Environment, USMBA-Faculty of Sciences & Techniques of Fez, 30000 Fez, Morocco 2 National School of Agriculture of Meknès, BP S/40, 50000 Meknès, Morocco Arab J Geosci (2017) 10:427 DOI 10.1007/s12517-017-3220-9