2.4.2. Pedology: Adaptation to the Different Requirements of the Models Used

The pedological composition of the Claise was determined from the Harmonized World Soil Database (HWSD) [52]. For the CORINE model, soil texture was determined using the USDA textural triangle after inputting the respective percentages of sand, silt, and clay for each soil group obtained from the HWSD. Texture was then classified with respect to the CORINE indices. The parameters of depth and stoniness were treated and classified similarly. After obtaining the texture, depth, and stoniness sub-factors, the three layers were input into the "raster calculator" in analogy to Figure 2.

For the SWAT model, the hydrologic soil group of each class was assigned following the United States Department of Agriculture [69] Soil Conservation Service (SCS) soil survey. Bulk densities were computed using the Soil Water Characteristics software following Saxton and Rawl (2006) [70] equations that were shown to have adequate accuracy for bulk density computation by Al Sayah et al. (2019) [71]. Likewise, the available water capacity and saturated hydraulic conductivities were also computed using the same software. Organic carbon content was determined by multiplying the organic matter content derived from the HWSD by 0.58, since organic carbon forms around 58% of the soil's organic matter as a rule of thumb [72]. Sand, silt, and clay percentages, as well as the rock fragment contents were extracted from the HWSD. The USLE\_K factor was computed following the formula presented in the SWAT documentation [55], while soil surface albedo was determined using the following formula [73]:

$$\text{Soil allbedo } (0.3 - 2.8 \text{ \mu m}) = 0.069 \cdot (\text{color } \text{value}) - 0.114 \tag{3}$$

After building the soil database, all parameters were reclassified in SWAT using user-adapted look-up tables for integration into the SWAT database.
