The water quality of the Pregel at Tsernyahovsk (3.72-3.86) was "very polluted” during that period, but at Kaliningrad (1 km from the rivers mouth) it was clearly worse, falling in the “extremely polluted” Russian quality class, with the value ranging from 5.36 to 7.25. There is a great anthropogenic load on the Pregcl, especially in the part close to the mouth of the river. In the Polish part of the basin, 93% of the population is not served by public sewerage networks.