Ocena jakości wody zbiornika Włodzienin w pierwszym roku funkcjonowania

This paper presents water quality assessment of the Włodzienin water reservoir in the river Troja in the first period of its operation. We analyzed the quality of the water supply (Troja river and Lewicki brook) and the outflow from the reservoir as well as the quality of stored water in the reservoir. Presented results of water quality tests were performed on the dates: November 2007, January, March, July and August 2008. The tests were aimed at determining: NO3-, NO2-, NH4+, PO43-, BOD5, water pH, electrolytic conductivity, water temperature and total suspension . In addition, at the test points by the dam the measurements were performed of: water transparency (Secchi disk visibility), dissolved oxygen, and once the chlorophyll „a” was marked in July 2008. The study of water quality showed that the water flowing into the reservoir and the outflow, due to the presence of nitrate, BOD5 and total suspension, was classified into surface waters that exceed water quality class II. In addition, the tested water from the reservoir Włodzienin was considered as eutrophic water due to the presence of nitrates, and it was found that the water is not sensitive to nitrogen compounds from agricultural sources. During the study it was found that the water reservoir was subjected to thermal stratification. The abrupt changes in temperature and dissolved oxygen has been reported and they were increasing with the water depth. According to studies the quality of the water passing through the Włodzienin water reservoir improves, and it especially regards to the content of nitrates and phosphates. The reduction of the: BOD5, electrolytic conductivity, water temperature, and total suspension has been observed. Currently, Włodzienin reservoir is on the first stage of reservoir operation, that is destroying river and land complexes. In order to make better observation and characteristics of the next steps of the reservoir operation, the study of water quality and ecosystem of the reservoir should be continued.