In the presented work the limnological characteristics of the Reservoir Nakło-Chechło elaborated on the basis of investigations carried out in 1996 has been shown. The results of investigations on thermal and oxygenic conditions existing in the Reservoir and the change dynamics of selected physico-chemical indicators of water quality in the Reservoir Nakło-Chechło are described. The paper describes aspecific example of acidotrophy of the Nakło-Chechło Reservoir as a result of anthropopressure. The results of chemical analysis of water in the Nakło-Chechło Reservoir and evaluation of the dynamic changes of various indicators with the atmospheric precipitation quantity on the basin superficies have shown that the Reservoir is under strong hydrological and chemical influence of the precipitation, which generally is acidic and has a very low total hardness. The exceptional vulnerability for acidification due to deficiency in water buffering capacity was, however, the decisive factor. The discharged weak buffering capacity of the Reservoir water facilitates the influence of direct precipitation and through superficial run off. The results of chemical analysis show high state of water quality in the Reservoir Nakło-Chechło as regards amount of indicators which describe water mineralization degree.

The aim of the present work was to analyse the results of investigations on the heavy metals content in the water of the Nakło-Chechło Reservoir. In this study the importance of this element in the characteristic of aquatic environment is stressed. Small content of heavy metals has excluded the possibility of the discharge of municipal and industrial sewage. All of these toxic substance included in water have confirmed that the Nakło- Chechło Reservoir is under strong hydrological and chemical influence of the precipitation and surface run off from the Reservoir basin area.

The paper presents the conversion dynamics of basic nitrogen and phosphorus forms as main factors initiating eutrophication process in Naklo-Chechlo reservoir. Limnological investigations of recreation reservoir were carried out in the period from January to December 1996. The results of chemical analyses of water samples taken in two collecting points of the reservoir and a composition of surface run-off from the basin area, have been presented.

The article presents changes in the thickness and duration of the ice cover found in the restored anthropogenic water reservoir of Pławniowice. It also defines the role the ice cover plays in the formation of the reservoir limnological cycle. Characteristic and significant changeability of the ice cover thickness and duration was observed. The changes in the ice cover demonstrate that they are cyclical but not regular. The ice cover did not always form in the analyzed period. It happened twice, i.e. in 1988 and 2007 (a gap of 20 years). The longest lake freezing period lasted 119 days. Changes in the ice cover duration also show certain periodicity. The shortest periods occurred approx. every 7 years. Maximum values of the ice cover thickness ranged between 10 and 52 cm. There is a relation between the ice cover thickness and its duration period. The rate of increase in the ice cover thickness varied between 0.296 and 3.6 cm/d. The hypolimnion removal impact on the ice cover duration period and thickness was not observed. On the other hand, the ice cover duration period affects the spring circulation duration. Thus, it has an influence on the oxygen balance of the limnic ecosystem.