Transformations in the amount and quality of organic matter (humus) during bank filtration of surface water were studied by analyzing the changes in total organic carbon (TOC), non-purgeable organic carbon (NPOC), chemical oxygen demand (COD), color of water, and UV absorbing humus fractions. The amount of organic matter expressed as TOC, NPOC, and COD depended on temperature and filtration distance from lake water. The color of water and the UV absorbing humus peaks presenting different humus molecule fractions decreased more effectively than other parameters measuring the amount of organic matter in water. The ratio of COD to TOC decreased when the filtration distance of water increased. Our observations indicated that bank filtration of humus-rich lake water changed more the quality of organic matter than its total amount.