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 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, Mg 2+ , HCO 3-, Cl-, SiO 3 2-, NO 3-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 NH 4 +-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. A growing interest in extreme weather events is reflected in many papers examined rainfall, flooding, heat, and drought. The research encompass all continents, but less than 10% of studies were focused in urban areas. This is surprising because urbanized areas are most exposed to hydrometeorological extremes due to the high concentration of people and infrastructure 1. Extreme events are defined across six major disciplines that examine them (climatology, earth science, hydrology, ecology, engineering and social science) 1. In our work, we focus on the definition, which is based on the assignment of any flow amplitude thresholds that identify floods and low flows in such a way that exceeding these thresholds is understood as the beginning of an extreme hydrological event. Floods resulting from storm precipitation refer to zone of high water levels. Floods resulting from continuous precipitation refer to above average multi-year flows. Continuous precipitation causes a slight increase in water levels in the river, but significantly affects its quality 2. The analysis of no-rain periods concerns the zone of low water levels. Extreme hydro-meteorological events, such as heavy precipitations or lack thereof, floods and droughts, are becoming more intense and frequent due to climate change and can strongly impact water quality 3. Most studies focus on the amount of water, on whether it is too little or too much 4 , but there also numerous studies on the effects of climate extremes on water quality. It is common knowledge that urbanisation drastically affects changes in river hydro-morphology and water quality. The problem of extreme hydro-meteorological phenomena is intensifying in the area of changing climatic conditions 5. Urbanisation affects the change of the water...

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.

Stawy Dojlidzkie (The Dojlidy Ponds) are located in the north-eastern part of Poland, near the capital of the Podlasie province, in Białystok. The Dojlidy Ponds (DP) are a complex of more than 20 reservoirs arranged adjacent to one another in an area of about 140 hectares. The largest recreation reservoir (Plażowy) is located within the city limits. Its total area is 34 hectares, it has a capacity of 597 040 m3 and a maximum depth of approximately 2.5 m. DP are supplied by a tributary of the Dojlidy Górne and the River Biała, the principal river of Bialystok. Water tests of a limnic and lenitic character in the upper part of River Biała catchment in Bialystok were conducted from March to October 2014. Referring the obtained results to the actual norms, it can be concluded that most of the parameters analyzed in DP can be assigned to the first class of surface waters. Exceptions were the iron ions, orthophosphates (SRP), total phosphorus (TP), Kjeldahl nitrogen, and also water color and DOC. According to the evaluation of trophic status, the water of DP is eutrophic. The average value of TSI was 55 in the water of the tested objects. The obtained results show that the ecological status of water in the largest pond within the DP complex, in accordance with, the Ecological State Macrophyte Index (ESMI) represent to the good state.

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