The article presents the results of an inventory of man-made load sources in the drainage basins of Kuibyshevskoe reservoir’s four inflowing rivers − Kazanka, Myosha, Sviyaga, Bolshoy Cheremshan, which differ in the physiogeographic conditions for runoff formation and the intensity of land use in the catchments. The quality and quantities of channelized runoff are monitored by regional departments of the Russian Federal Hydrometeorology and Environmental Monitoring Service. The inventory of external load sources included collection and systematization of information on economic activities within the drainage area of Kuibyshevskoe storage reservoir (888 enterprises). Analysis of the collected material showed that the input of nutrients from the catchment with mineral and organic fertilizers was quite low in the studied basins. The load from point sources estimated from wastewater discharges and pollutant concentrations in them was also low. Stormwater sewerage, random uncontrolled discharges from sedimentation pools, leakage from landfills, non-canalized settlements, as well as the lack of information about the quality and quantity of wastewaters of this category requires that they are classified as non-point pollution. Information has been gathered on non-point pollution sources of both distributed (urbanized and agricultural spaces, landfills, gas stations, industrial sites, etc.) and linear (highways of various categories) types.