The Role of the Catchment Area in Shaping Water Quality in the Lowland Springs of the Knyszyn Forest (NE Poland)

The Puszcza Knyszyńska springs are an important element of the environment, conditioning the high geo- and biodiversity in the region. These springs are layered outflows that drain the waters of the Quaternary level. More than 200 outflows have been cataloged, and 80 of them have measured/estimated yields and analyses of their water qualities. During periods of low water levels, the discharge efficiency most often fluctuated within a range of 0.5–2.0 dm³·s^–1. In light of the applicable legal standards, the tested waters were of excellent quality. They belonged to the two hydrochemical types HCO₃-Ca and HCO₃-Ca-Mg, indicating the Quaternary aquifer’s homogeneity in the post-glacial areas. Small concentrations of most of the chemical parameters of water were found in the forest springs. Larger transformations in the chemical composition of water occurred in the outflows located in agricultural land and rural areas. A characteristic feature of the chemical composition of the water in the region’s lowland springs was an increased concentration of biogenic compounds (nitrogen, phosphorus, and carbon compounds), both organic and inorganic. The average concentration of dissolved organic carbon in the water of the lowland springs in summer exceeded 4 mg·dm⁻³. In some outflows, most often of a swamp nature or located in peat areas, the concentration of dissolved organic carbon even exceeded a dozen or so mg·dm⁻³.