This paper presents an impact of hydro-meteorological extreme events and urban catchment to water quality in small rivers in Białystok (Poland). The results from a five-year study have taken into account droughts, continuous precipitation, and storm precipitation causing flash floods. Extreme hydro-meteorological events has a different impact on the physical and chemical parameters of water. It was found that the largest change in water quality occurs on the 2nd day after the rainfall and changed concentration of some chemical parameters persists for a long time. The majority but, what’s important, not all of them are diluted after floods and concentrated after droughts. Flash flooding results in a large increase concentrations of DOC and selected forms of phosphorus. Higher values of EC, Eh, Mg²⁺, HCO₃^-, Cl^-, SiO₃^2-, NO₃^-N, TN were observed during drought compared to the average values from 2014–2018. A high degree of naturalness of the river valley and increased water retention results in a decreased concentration of NH₄⁺-N, DOC and phosphorus forms. The buffer zone plays an important role in limiting the inflow of pollutants and nutrients from the catchment area. That is why it is worth undertaking restoration of river valleys in urban areas.

This study describes changes in the trophic status of 12 lakes within Suwałki Landscape Park (SLP). All of the trophic classifications of the lakes were based on the trophic continuum division. Trophic status was determined by means of multiparameter indices using several diverse criteria. In this study, the assessment of the trophic status of lakes included water quality; abundance and biomass of bacterioplankton, phytoplankton, and zooplankton; and primary production of phytoplankton. The Carlson trophic state index (TSI) describes the level of water fertility and indicated the dominance of moderately eutrophic waters. Lakes Perty, Jeglówek, and Hańcza have a trophic status that indicates mesotrophy (TSI <50). The trophic status of the studied lakes was determined based on the bacterial abundance and clearly showed a lack of oligotrophic lakes in SLP. Based on the number of bacteria, only Lake Szurpiły can be classified as β-mesotrophic, whereas Lake Linówek can be characterized as hypertrophic with some features typical for humic waters. The greatest value of gross primary production was observed in Lake Linówek (126.4 mg C/m³/h). The phytoplankton trophy index varied from 1.59 to 2.28, and its highest value, which indicated eutrophy, was determined for Lake Udziejek. In the case of Lakes Hańcza, Szurpiły, Perty, Jeglówek, and Kojle, the index ranged from 1.25 to 1.74, which indicated mesotrophy. The majority of the lakes were classified as mesoeutrophic (1.75–2.24). The highest trophic status was assessed for lakes with a marked dominance of cyanobacteria (Lake Przechodnie, Lake Krajwelek, Lake Udziejek, and Lake Pogorzałek), which is commonly recognized as an indicator of high trophic status. Considering all of the indices of trophic status, the analysis of rotifer community structure indicates that the studied group of lakes is mesoeutrophic or eutrophic. The values of crustacean zooplankton indices indicated that the trophic status of the studied lakes was close to that determined using a TSI. The parameters of zooplankton abundance and species structure allowed for the observance of changes in the tropic levels of lakes, which are difficult to detect by a chemical assay alone.

Many freshwater ecosystems face severe threats from anthropogenic disturbances. In the field, we investigated the morphology of spring niches and the species richness of vascular plants and bryophytes in 16 springs, draining the quaternary aquifers, located in two different environments—an urban area (city of Białystok) and a protected area (Knyszyn Forest Landscape Park, NE Poland). In total, 47 vascular plant and 45 bryophyte species were recorded, representing mostly crenophytes including protected species. The most important water quality parameters that can be used to evaluate variations of the spring water chemistry in NE Poland are the mineral-related parameters (electrolytic conductivity, Ca²⁺, SO₄²⁻, and Cl⁻). The organic-related parameters (DOC) and nutrients (TP, NO₃⁻-N) were negatively involved in water quality variations. Our results show that anthropogenic activity significantly affects the biodiversity of plant communities in lowland springs. The presence or absence of crenophytes and bryophytes is indicative of the ecological status of the groundwater outflow complexes.

This paper presents an object-oriented approach for analysing and characterising the urban landscape structure and its influence on the quality of surface waters and shallow groundwater. We investigated springs, streams and ponds from an urban area. The land cover classification was adopted with the conceptual framework of urban land cover (HERCULES model). This study has demonstrated that water quality in the urban area is strongly related to land cover, and the degree of its transformation is not the same in all types of waters. The land with forests and shrubs does not have many extreme values in water chemical characteristics. Statistical analyses indicated that the main environmental factors influencing water chemistry are impermeable surfaces such as buildings. They are an essential element which deteriorates water quality. The patches with buildings and pavements were characterised by a wide gradient of nutrient concentration in rivers and ponds. Shallow groundwater had a limited effect on surface water quality.

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.