AbstractIn territories without settlements, major livestock production or industry, and from territories devoted to row‐crop agriculture (diffuse pollution sources), the annual mean concentrations of total phosphorus compounds in waterways were found to be 17 to 43 μg · 1−1P. Where there are point or hybrid pollution sources in watersheds, the annual average concentrations vary from 56 to 410 μg · 1−1P. It was found that annual average total phosphorus concentration values obtained from three‐week sampling intervals can be used to show the presence of diffuse, hybrid and point pollution sources. The main sources of the high and permanent total phosphorus concentrations were densely populated areas, industrial works, agriculture, inadequately managed farms and disposal sites for solid and li