This study aims (1) to determine the regulated carbonaceous disinfection by-products formation potentials under five disinfection scenarios for extremely low specific ultraviolet absorbance water sources, (2) to monitor the spatial and temporal variations of carbonaceous disinfection by-products in two full-scale drinking water distribution system for one-year, and (3) to evaluate carcinogenic and non-carcinogenic health risks of carbonaceous disinfection by-products through multi-pathways. Formation potentials of trihalomethanes and haloacetic acids were in the order of chlorination > ozonation/chlorination > chloramination > ozonation/chloramination > ozonation. Trihalomethanes were the most prevalent disinfection by-products followed by haloacetic acids. Chloroform was the dominant species of trihalomethanes, whereas trichloroacetic acid and dichloroacetic acid were the predominant species of haloacetic acids. No clear seasonality changes in carbonaceous disinfection by-products level were observed in water source with lower dissolved organic carbon values, and higher carbonaceous disinfection by-products values were observed in summer for water sources with higher dissolved organic carbon values. Also, there were no clear correlations between carbonaceous disinfection by-products formations and tested surrogate water quality parameters. Although the non-cancer risk of carbonaceous disinfection by-products was below permissible recommended levels, the average lifetime carcinogenic risk levels for trihalomethanes and haloacetic acids were 6.9E-05 and 5.8E-05, respectively, which were above the negligible risk level.