Figure 1: Geographical localization of the studied sites P1-P4, delimited by colored lines in the four side images and reported as rectangles in the central image, where the whole analyzed watershed is also shown.

Data collection

For the realization of a complete SWAT model several datasets are required as inputs data. The Digital Elevation Model (DEM), needed for the delineation of the main watershed, river network, and sub-basin generation, was provided by the Shuttle Radar Topography Mission (SRTM), with a cell resolution of 10 x10 m. The land cover was obtained from the Corine Land Cover database (CLC, 2018), while the soil classification was extracted from Direcção-Geral de Agricultura e Desenvolvimento Rural (DGADR, 2013) with a scale of 1:25,000 (12.5 x 12.5 m). The information on soil characteristics, like saturated hydraulic conductivity (Ks), available water content (AWC), and bulk density (BD) were defined with the Harmonized World Soil database (FAO, 2012) a vectorial geodatabase obtained from a 30” resolution map and further refined using 3,000 soil columns from the World Soil Information Service (Batjes et al., 2017, 2020; Ribeiro et al., 2020) and literature data (Grilli et al., 2021), while other missing soil’s parameters were obtained from SWAT’s default dataset (Table S2). Data of streamflow and sediments load for the period 1985-1989 utilized to calibrate and validate the model were obtained from four hydrometric stations located inside the watershed named Albernoa, Monte da Ponte, Oeiras, and Entradas (Fig. 1) (SNIRH, 2006).