The Impact of Land Cover on Selected Water Quality Parameters in Polish Lowland Streams during the Non-Vegetative Period

The search for the best landscape predictors explaining the spatial variability of stream water chemistry is one of the most important and recent research issues. Thus, in the current study, relationships between land cover indices and selected water quality parameters were evaluated regarding the example of 54 lowland temperate streams located in central Poland. From November 2021 to March 2022, water samples were collected in the monthly timescale, and the concentrations of NH₄⁺, NO₃⁻, and NO₂⁻, as well as electrical conductivity, were correlated with the percentage of land cover types calculated for total catchment area, buffer zones, cut buffer zones, and radius. For such computing, Corine Land Cover 2018 and Sentinel 2 Global Land Cover datasets were used. In the case of both datasets, results indicate significant dependence of NO₃⁻, and NO₂⁻ concentrations, as well as EC values on cover metrics. Overall, agricultural lands favored higher concentrations of NO₃⁻ and NO₂⁻, whereas mainly coniferous forests reduced nitrogen pollution. Significant correlations were not documented in the case of NH₄⁺ ions, the concentrations of which could be linked to point sources from municipal activity. Correlation performance was slightly better in the case of the S2GLC dataset, while the best spatial scales were generally seen for wider buffer zones (250 and 500 m) and total catchment area. The study provided spatially extensive insight into the impact of land cover predictors at different scales on nitrogen compounds in a lowland landscape.