Water reservoir "Gruza" is used forthe water supply of the town of Kragujevac and it's surroundings. The paper shows a comparative overview of physical, chemical and microbiological parameters during the period of 1987-1989, and 1997-1998. Variations of physical, chemical and microbiological parameters are given in the paper.

During 2001, water from river Cerava and from the littoral where the river flow into lake Ohrid, were examined. Bacteriological analysis included ecological and sanitary aspekt of water state. Heterotrophic, proteolytic, amylolytic and phosphomineralizing bacteria, most probable number of total coliforms (MPN) and presence of Escherichia coli and Clostridium perfringens were determined. The results of investigations shows organic and faecal pollution and permanent negative anthropogenic effects.

In the scope of complex physical-chemical and biological water examination of Bocac water reservoir, the river Vrbas and trbutaries Ugar and Crna Rijeka, examination of standard microbiological indexes of water quality (aerobic organotrophs at 22-26 deg C and 37 deg C, total colliforms and colliforms of fecal origin) was performed during 2002 (March-November). Number of examined microbiological parameters was mainly in the scope of the 2nd water category (beta-mesosaprobic water) with worse water quality in upstream part of the reservoir. Ugar tributary had the best water quality, while Crna Rijeka had the worst status with obvious anthropogenic influence.

Bacteriological examination have been carried out within the comprehensive hydrochemical and hydrobiological investigation of river Koselska during 2002. The aim of investigations is to confirm condition of bacteriological communities and water quality of river Koselska. The results of investigations shows pollution by organic matter. In order to prevent further eutrophication processes, certain measures of river water protection and conservation should be undertaken. Also, the regular monitoring of water quality should be established.

As a consequence of bombing of Novi Sad Oil Refinery, Serbia (Serbia&Montenegro), the spillage of large amounts of oil and derivatives caused hydrocarbons pollution of the area surrounding the Refinery and the river Danube, thus directly endangering the entire water source "Ratno ostro". As a measure of protection in the division zone of the Refinery and the water source area, a hydraulic barrier was constructed. Within the process of monitoring piezometer water quality and the water supplied by protection system wells, microbiological analyses of water were carried out with the aim of supervising the barrier functioning. The results have shown that bacterial populations in polluted areas exhibit a duel role: they act as bioindicators of a certain pollution, but at the same time they take part in the process of selfpurification.