The paper contains preliminary results of investigations on transformations of organic and biogenic compounds in small water reservoir. The reservoir Górny Młyn near Końskie (Świętokrzyskie District) located on the Czysta river was chosen as an object of investigations. The bases of analysis were hydrological and chemical investigations covering measurements of water volume inflowing and flowing from the reservoir as well as determination of its chemical composition. The investigations which covered six measurements series were carried out between May and July in the year 2006. The following indicators of pollution were determined in laboratory by means of reference methods in taken samples of water: BOD2, P-PO4, N-NH4, N-NO2 and N-NO3. Hydrometric measurements showed that the main source of alimentation of investigated reservoir is the reservoir Szawelnia located above, from which inflow to the Górny Młyn reservoir fluctuated between 0,003 do 0,120 m3⋅s-1. Taking into account small stream „without name”, the total amount of water inflowing to the reservoit during investigations was on an average 0, 055 m3⋅s-1, while the amount of flowing from the reservoir was on an average 0,051 m3⋅s-1. The crucial influence on quality of water inflowing and flowing from the decanter had concentration of nitrite nitrogen, which several ...
