The aim of this study is to conclude the experiences of the maintenance practice of an artificial thermal lake. The first years (2015-2017) of the development of the lake were analysed and evaluated along the following questions: a) What kind of design processes and maintenance interventions are related to the process of fitting the lake into the landscape? b) How have the ecological conditions of the lake evolved in the past period (zonation, succession, plantation and colonization)? c) Which general experiences could be gained from the operation of this artificial thermal lake this far? The authors of the present study were already engaged in the planning process, participating in the preparation of four different design documentations. The planting design and the maintenance instructions were based on a physico-chemical monitoring, phytoplankton, zooplankton and macroinvertebrate sampling, and machrophyte assessment. The significant processes during the three years of the lake are presented by functional groups of biota, separately assessing the characteristics of the changes of macrophytes. In 2017 an individual macroinvertebrate assessment was done, moreover a fish die-off occurred in August 2017, which are mentioned separately as well. The data in total suggested that the water of the lake is highly hypertrophic, further machrophyte introduction can prevent the plant nutriments to be absorbed by algae. Partly the algal growth but also the unlucky coincidence of other factors (e.g. high water temperature, cold weather front, maintenance problems) led to the die-off of the spontaneously overpopulated fish stock in 2017.
Kamencové Lake (also called Alum Lake) located in Chomutov (North Bohemian Brown Coal Basin, Czech Republic) is a worldwide unique for its lake water chemical composition (K Al (SO4)2 12 H2O) that naturally prevents algae growth. The region used to be a centre of heavy industry based on brown coal burning, with a crucial impact on the environment (especially acid rain) in 1980s. This fact was considered the key aspect influencing the lake water quality deterioration in the past, besides the growing popularity of the area for recreational purposes (increased risk of eutrophication) and the significant changes in the lake maintenance (increased risk of eutrophication, excessive bottom sedimentation). Due to the real threat of gradual losing the lake water unique characteristics, scientifically-based systematic measures reducing the potential risk of eutrophication need to be implemented. The present study builds on the results of previous surveys by Geofyzika Brno, Povodí Ohře, s.p. or Hydroprojekt Praha. Its aim is to assess the potential risk of eutrophication in Alum Lake and to propose remedial measures.