The topic of the thesis is focused on the assessment of the risks of the water source for the supply of drinking water to the population in the selected area of Demänovská dolina. The diploma thesis contains an overview of legal norms, introduces a system of risk analysis of water distribution systems, risk structure of drinking water supply, individual steps for processing of drinking water supply risks, quality management and emergency drinking water supply. The practical part is devoted to the processing of natural conditions in the selected area Demänovská dolina, water resource capacity, evaluation of water quality and subsequent categorization and ultimately the assessment of the risks of the water source, which is the main goal of the thesis. According to the drinking water categorization, it was found that the majority of drinking water indicators of the monitored source meet the requirements.