The Ukrainian part of the basin of the San River is characterized by a high content of organic substances, ammonia, sulfate, total iron and petroleum compounds. In recent years, in the Shklo River (in the San sub-basin, crossing the border) there is a steady tendency for quality to deteriorate, with increase in nutrients concentration, associated with an increase in discharges of untreated sewage. The town of Yavorov in Ukraine has virtually no working sewage treatment plant.