# Reconstruction of Ancient Lake after Peat Excavation--A Case Study about Water Quality
## 1 Introduction  
Saving water resources is a crucial issue in the twenty first century. Increasing water scarcity in different parts of the world has become an urgent political and economic problem. The measures proposed hitherto include the reduction in water consumption in all aspects of human life and increasing water retention, wherever possible [1]. Additionally, water shortage is often connected with poor water quality, which limits its use in agriculture or recreation [2].  
Specific possibilities for water saving occur in areas with abandoned open pit mines, especially after the excavation of brown coal and peat bog. Post mining lakes are still more frequent in Europe (Germany, Poland, Ireland) and Australia due to the possibility of maintaining water resources in areas that formerly suffered water shortage related to mining activities. Studies on mining's impact on the environment and its consequences after the cessation of excavation are perceived as more environmentally important with every decade. Among them, an interesting subject is the role of post-mining reservoirs and their subsequent impact on the environment [3, 4, 5, 6]. Post-mining reservoirs have become frequent elements of the landscape in many countries [7, 8, 9]. Studies of the water quality of such reservoirs create some methodological problems, especially under acid mine drainage conditions and the maintenance of optimal water quality in such objects is very important for local communities [8].  
Several authors have described the impact of climate changes on water cycle and water quality parameters [10; 11; 12; 13; 14]. Many regions of the world were affected by droughs in recent decades and the insecurity of water availability has stimulated the search for preventing measures [2]. In areas with water shortage, pit lakes can be important sources of water for agriculture and for recreation, provided that the water quality is satisfactory. Central Poland, especially the Wielkopolska region, is characterized with visible water shortage in agriculture, decreasing water levels in lakes, low precipitation (about 500 mm per year) and is inconvenient for farmers' distribution of rainfalls. This situation is partly related to water management strategies in municipalities and in watersheds [15; 16]. The rebuilding and recultivation of small water reservoirs in rural landscape and the creation of pit lakes can be the partial answer to meet the goals of the EU Water Framework Directive [17]. When a peat lake is planned in the place of former mining activities, it is possible to figure out the pit dimensions to facilitate technical works according to establishing close to natural environmental conditions (reservoir morphology, removal of organic matter). It is possible to limit the rate of disappearing water reservoirs in the rural landscape by means of rebuilding former water bodies and such projects are especially needed in areas with water shortage, like central Poland.  
The scientific aims of undertaken studies were to assess the quality of water in the newly built post-peat reservoir and to determine its importance in shaping local biodiversity, as well as to identify the water and littoral plants dominating in the first years after establishing the reservoir. The practical aim was to check the sensibility of building a water reservoir in the place of a former eutrophic post-glacial lake and the possibility of maintaining its good water quality.