The Functioning of a Water Body Within a Fluvio-Lacustrine System as an Effect of Excessive Nitrogen Loading—The Case of Lake Symsar and its Drainage Area (Northeastern Poland)

Influence of Cascading River–Lake Systems on the Dynamics of Nutrient Circulation in Catchment Areas

Matter circulates in nature constantly, between terrestrial and aquatic ecosystems, exchanging elements between the biotope and biocenosis. Each aquatic ecosystem is resistant to a specific load, above which its degradation occurs. It seems that the resistance of cascade reservoirs is higher than that of drainless reservoirs. Changes taking place in one part of the river–lake system cause disturbances in the dynamics of nutrient circulation in another. Rivers supplying water to lakes in a river–lake system have a significant impact on their water quality and on the spatial distribution of pollutants in their bottom sediments and in macrophytes located along their route. The assimilation capabilities of cascading river–lake systems result from their reaction to environmental stressors in the form of anthropogenic factors. They act as natural biogeochemical barriers, limiting the transport of pollutants outside ecosystems. In-depth knowledge of the processes taking place in the river–lake systems enables analyses aimed at forecasting the directions and intensity of these changes and predicting the response of the river–lake systems to the loads from the catchment areas. The collected information makes it possible to create simulations of processes occurring in river–lake systems, which allows for effective action to be taken to protect surface waters. This article provides an overview of available literature, presenting significant research results which enable an understanding of these processes.

Analysis of the Theoretical Performance of the Wind-Driven Pulverizing Aerator in the Conditions of Góreckie Lake—Maximum Wind Speed Method

The eutrophication of surface waters is a natural process; however, anthropogenic activities significantly accelerate degradation processes. Most lakes in Poland and in the world belong to the poor and unsatisfactory water quality class. It is therefore necessary to limit negative anthropogenic impacts and introduce restoration methods, in particular those that are safe for the aquatic ecosystem. One of these is a pulverizing aeration Podsiadłowski method that uses only wind energy. The method allows for the moderate oxygenation of hypolimnion water, which maintains the oxygen conditions in the overlying water zone in the range of 0–1 mg O2·dm-1. The purpose of the work was to develop a new method of determining the efficiency of the aerator pulverization unit in the windy conditions of the lake. The method consists in determining the volumetric flow rates of water in the aerator pulverization unit, based on maximum hourly wind speeds. The pulverization efficiency in the conditions of Góreckie Lake was determined based on 6600 maximum hourly wind speeds in 2018. Based on the determined model, the theoretical performance of the machine was calculated, which in the conditions of Góreckie Lake in 2018 amounted to less than 79,000 m3 per year (nine months of the effective aerator operation).