Upper Vistula River: Response of aquatic communities to pollution and impoundment. IV. Chemical and bacteriological indices of water quality

The water quality and its changes in Upper Vistula River on the sector between 10.9 and 336.7 km of its course were carried out in annual cycle in the years 1997-1998. The classification of water comprised four classes of purity (I-IV) and based on the 5 biological and 5 chemical features of water. Particular classes were characterized by numerical taxonomic value of pollution (NTVP): 1.0-1.5 - class I, very pure water; 1.5-2.5 - class II, relatively pure water; 2.5-3.5 - class III, polluted water; 3.5-4.0 - class IV, very heavily polluted water. On the investigated section of the Vistula River three stretches might be distinguished: the first one between 10.9 and 66.2 km of the river course; the second from 115.6 to 248.2 km and the third at 336.7 km of the river course. On the basis of the mean annual values of biological and chemical features together, relatively pure water (II class purity) with NTVP ranging from 1.87 to 2.37 was noticed on the first investigated river stretch. The greatest pollution was shown on the second stretch, where NTVP ranged from 2.56 to 2.82 which corresponded to III class of water purity. On the third stretch the water was relatively pure (II class of purity) with NTVP 2.32.