The thesis is concerned with a small reservoir Komorów situated on Mi-likówka Brook in dolnośląskie voivodship. The main function of the reservoir is water retencion for agriculture purposes and recreation. The paper includes the results from the study of the quality of water flowing into the reservoir, water re-tentioned there, and flowing out of the reservoir. The study was conducted between March and October 2009. Following water quality indicators were taken into consideration: nitrates, phosphates, water temperature, dissolved oxygen, electrolitical conductivity, reaction and water transparency. Evaluation of water quality according to the valid Regulation of Minister for the Environment regarding the means of uniform waters status classification and evaluation of waters eu-tophication was described in the thesis. Moreover, it was verified whether waters taken into scrutiny are vulnerable to nitrogen compounds pollution coming from the agricultural sources. The usability of water reservoir was estimated by com-parision of the water indicators with the limit values characterizing water suitable for swimming.The study revealed that waters flowing into the Komorów reservoir, due to the nitrate values exeeds limit values for 1st class waters. Water temperature, dis-solved oxygen, electrolitical conductivity and reaction values classify it as 1st class waters. Waters flowing out of ...