Analysis of the recreation conditions in the Tresna reservoir based on the assessment of the fertility state of reservoir water

Abstract

The aim of this research was to analysis of the recreation conditions in the Tresna reservoir water based on the assessment of the degree of fertility and its changes in the reservoir water. Due to the water supply role of the last reservoir in the cascade of the Soła River (the Czaniec Reservoir), the reservoirs situated higher in the cascade (Tresna and Porąbka) should have good water quality. Recreational use of the Tresna Reservoir also obliges to protect it. The trophic state of reservoir water was estimated on the basis of chlorophyll a concentrations and planktonic algae biomass and their taxonomic composition. The research was conducted in 2021 during the growing season at three research points (in the area of Zarzecze, the area of influence of the Łękawka River and the area of the dam). Concentrations of chlorophyll a and phytoplankton biomass were higher in the Zarzecze area and the dam area, and 
in summer period (mainly in August) they exceeded the limit values for eutrophy. In turn, the lowest values were observed in the area of the Łękawka River tributary to the reservoir. In most of the research period, they remained within the oligotrophy and mesotrophy limits. Periodic increase of water fertility to the eutrophy level indicates that the reservoir water should be controlled, especially in summer, due to the sanitary safety of resting people.