Quality of groundwater in rural homesteads and agricultural land in the catchment of Lake Miedwie

The paper presents the impact of pollutants from areas intensively used for agriculture on the quality of shallow groundwater in the drainage basin of Lake Miedwie, which is the main source of potable water for the city of Szczecin. This groundwater, due to the poor insulation against the penetration of contaminants from the surface, is a good indicator of the environmental pressure level from agriculture. The aim of the study was to analyze the chemical composition as well as the pH and electrolytic conductivity of waters of the first Quaternary aquifer in the catchment area of Lake Miedwie, located in the municipality of Warnice, which is characterized by intensive farming. The results indicate that there has been a noticeable improvement over the last ten years in the quality of groundwater, and periodic increases in the levels of certain chemical parameters such as ammonium nitrogen (6.070 mg dm-3), nitrate nitrogen (225.1 mg dm-3), phosphate phosphorus (2.635 mg dm-3) or potassium (452.0 mg dm-3) can be explained by negligence or insufficient knowledge of farmers with respect to manure storage and rational use of mineral fertilizers. Correlation analysis of the sum of chemical parameters regarding conductivity demonstrated a virtually absolute relationship (r=0.948 at p=0.001), confirming a close relationship of groundwater’s chemical parameters with the properties of the physical parameter such as specific electrolytic conductivity. Moreover, it was shown that the specific electrolytic conductivity of groundwater of 8 piezometric intakes tested was mainly shaped by the concentrations of sodium (Na), potassium (K) and magnesium (Mg) for all chemical parameters analyzed.