Changes in capacity of water reservoir Cedzyna during its exploitation since 1972 till 2003 are presented in the paper. Analyses were based on cross sections of the reservoir’s basin from before its fulfillment (1967) and those measured with the echo sounder Ceeducer in 2003. Silting of reser-voir was predicted based on empirical methods. The volume of reservoir was found to decrease by 112.8 thousand m3 during 31 years of its exploitation and reservoir’s life span was assessed at 685 years. An error analysis was additionally made of calculating the surface area of a cross section at varying number of sounding sites. It was found that there was no need to note too many coordinates and depths and for the Cedzyna reservoir the distance between measurement sites up to 16 m was sufficient.

The main objective of the study was to evaluate if macrophytes structure and trophic status of dam reservoir Kraśnik on a small lowland river Wyżnica are determined by phosphorous loadings. Studies were conducted seasonally in May, July and October during the years 2008-2009. Samples were taken at four sites: Site 1 - inflow of the Wyżnica River to pre-dam, Site 2 − pre-dam, Site 3 − dam reservoir and Site 4 - outflow of the Wyżnica River from dam reservoir. Physical and chemical parameters (temperature, Secchi disc depth, dissolved oxygen, pH, conductivity, total suspension, chlorophyll-a, TP and P-PO4) were measured in water samples. Together with water parameters there were estimated biomass of phytoplankton and species composition and biomass of emergent, floating-leaved and submerged macrophytes. Concentrations of TP, chlorophyll-a and Secchi disc depth were used to calculate trophic state index of Carlsson for dam reservoir and its pre-dam. Based on mean water current, mean residence time of water in dam reservoir and concentrations of TP and P-PO4 loadings (g m-2) flowing into dam reservoir with the Wyżnica River were calculated. The results showed visible negative effect of phosphorous loadings on both macrophytes composition and trophic state of the reservoir. The marked changes concerned soft vegetation. High P loadings (7.74 g m-2 of TP and 6.03 g m-2 P-PO4) during the spring of 2008 caused the disappearance of characeans meadows. In 2009, the presence of rigid hornwort (Ceratophyllum demersum L.), the species typical for eutrophic lakes was noted. This unrooted submerged plant uptakes dissolved orthophosphates directly from the water column.

Values of Carlsson index (51.4 ≤ TSI ≤ 68.2) indicate the eutrophic state of dam reservoir Kraśnik. During summer season in dam reservoir there were observed algal blooms (biomass of phytoplankton exceed 10 mg WW dm-3) and low water transparency (Secchi disc depth ranged from 0.4 to 0.65 m). During the two-year studies in dam reservoir Kraśnik a high reduction of P loadings, mostly dissolved orthophosphates was observed. Dependently on season, reduction of P-PO4 loadings ranged from 52% (July 2008) up to 91% (May 2009). The reduction of TP was lower and reached values from 15% (May 2008) to 48% (July 2009).

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.

The study presents the results of the research into different phosphorus forms in the bottom sediments of anthropogenic limnic ecosystems i.e. the reservoirs of Pławniowice, Rybnik and Goczałkowice (SP). The bottom sediments of dam reservoirs were investigated by chemical extraction procedure for phosphorus forms. The lowest value of the mean AAP form percentage in the Pławniowice bottom sediments reflected the effect of reclamation with the hypolimnetic removal that had been conducted in the reservoir since 2003. The highest percentage of the RDP form (2%) was found in the Goczałkowice bottom sediments. The order of the specific speciation forms in the bottom sediments of the examined reservoirs was:

Rybnik: AAP > EP > WDP > RDP; 4,630> 3,740 > 117 > 65 > 3.5 mgP/kg

Pławniowice: AAP > EP > WDP > RDP; 916 > 783 > 107 > 15 > 1.4 mgP/kg

Goczałkowice: AAP > WDP > EP > RDP; 686 > 628 > 51 > 7 > 0.14 mgP/kg

The mutual correlations between the phosphorus speciation forms (AAP : EP : WDP : RDP) were as follows:

Rybnik: 1,323 : 1,068 : 33 : 18 : 1;

Pławniowice: 654 : 559 : 76 : 11 : 1;

Goczałkowice: 4,900 : 4,485 : 364 : 50 : 1.

The comparison of the mean concentration values for specific phosphorus forms in the bottom sediments of the three investigated reservoirs demonstrated that the Rybnik sediments had the highest contents of phosphorus. The contents in Pławniowice and Goczałkowice were 5-7 times lower