4.1. Effects of land use on TSS leaching and inorganic nutrient concentrations
In recent years, watershed modelers have put increasing emphasis on simulating internal watershed processes as realistically as possible (Nasirzadehdizaji et al., 2022; Senent-Aparicio et al., 2021). For the correct diagnosis of agricultural production in hilly terrain, the prediction of erosion losses is crucial ( Basha et al., 2015; Smoroń et al., 2009), and water quality can be improved by using the catchment area effectively (Abeysingha et al., 2015; Bedla and Król 2014; Louis et al., 2011). A large effect on erosion is related to the way the adjacent area has been used and developed. In forest areas in small mountain catchments, land changes are less pronounced (Woo et al., 2021).
SAR has revealed the specific associations between adjacent areas and water indicators. For instance, permanent grasslands limit the supply of weathered material, and there is a linear relationship between permanent grassland and the leaching of N-NH4+in the Smugawka stream (Table 5). Since forests slow soil erosion, they are an important source of protection against water erosion (Stępniewski et al., 2010). Additionally, the adopted methods for assessing the intensity of water erosion are influenced by modern morphogenetic processes, and the physiographic features of the catchment area play a major role in determining soil losses (Halecki et al., 2018 a).
The leaching effect of inorganic nutrients can also be limited by increased vegetation. The SAR results revealed that the area covered by permanent grasslands exhibited the lowest inorganic nutrient losses (Fig. 6). Moreover, despite low concentrations of the inorganic nutrients in the tributaries, their concentrations in the main stream gradually increases (Fig. 7).