Application of the SWAT model to the hydrological modeling of the Nfifikh watershed (Morocco): study of the dynamics of surface and groundwater and their relationship with soil properties

Abstract

This paper presents the application of the SWAT model to the Nfifikh watershed (Morocco) to analyze the dynamics of surface and groundwater flows and their relationships with soil properties, topography, and land use. The model was implemented using local and global climate data, a Digital Elevation Model (DEM, 30 m), soil maps, and land use/cover (LUC) data, followed by spatiotemporal calibration and validation. The results revealed a typical water balance for a semi-arid basin characterized by a limited hydrological budget: annual precipitation of about 420 mm, of which 280 mm (67%) is lost by evapotranspiration, while 110 mm (26%) is discharged by the hydrographic network, divided into 55 mm of surface runoff, 25 mm of lateral flow and 30 mm of baseflow. The model also estimated a groundwater recharge of 70 mm to the shallow aquifer. Spatially, marked flood peaks and higher sediment inputs occur on the steep and exposed eastern slopes, while prolonged baseflow and net sediment deposition are observed towards the intermediate and downstream reaches. The model performance was found to be excellent (high NSE and R² values), confirming the effectiveness of the spatial calibration of soil and channel parameters. This study provides quantitative evidence of surface water-groundwater interactions and spatial variability of hydrological responses in a Moroccan semi-arid basin, highlighting the relevance of HRU-based spatial calibration to simultaneously explain peak discharge, baseflow and sediment production, thus improving the transferability of the approach to similar basins.