Effect of Rainfall on Water Parameters in Recreational Lakes in Heidelberg, Germany

Abstract

This study evaluates the impact of precipitation on water quality in Heidelberg, Germany’s recreational lakes during sporadic rainfall events from August to September 2023. Data were collected from five stations, monitoring physicochemical properties and nutrient levels before and after rainfall. Measurements of dissolved oxygen, pH, conductivity, and redox potential were conducted in situ, while turbidity, nitrates, phosphates, sulphates, zinc, and copper levels were analyzed in the SRH Heidelberg water laboratory. Findings indicate pH levels increased due to dilution effects, while conductivity rose due to runoff, enhancing ion concentration in the lakes. Dissolved oxygen levels also increased, attributed to aeration from rainfall-induced surface turbulence. Redox potential decreased, reflecting atmospheric oxygen dissolution. Nutrient concentrations, including nitrates and phosphates, along with sulphates, declined post-rainfall, suggesting a dilution effect without significant impact from surface runoff. This outcome implies the absence of major nutrient and sulphate sources upstream. Heavy metals like zinc and copper also decreased in concentration, indicating no introduction through runoff or sediment transport. The study underscores the variability of water quality parameters across different lakes, influenced by factors such as water sources, surrounding land use, geological conditions, and lake characteristics. Overall, water quality improved post-rainfall, making the lakes suitable for recreational activities, with the study establishing a non-linear correlation among the water quality parameters and deducing the P ratio for each parameter.