This paper presents the results of water quality analysis of the rivers Tamis, Plovni and Stari Begej, using the WQI method, for the time periods 1987-1991 and 1998-2002. It also show the trend of water quality of these water streams for two characteristic time periods, through trend of WQI index.

The sampling of Crnojevica river has been carried out, because of estimation the correlation between main water quality parameters and precipitation impacts, as well as adequate hydrological parameters. An appropriate dynamic sampling has been applied. Continuous pollution of river water has been confirmed, as well as source of the pollution. It is estimated strong correlation of water quality parameters from precipitation quantity and water level, especially for sanitary pollution. Change of quality parameters value is discrete and accidental.

Water quality studies of the Danube river in Belgrade region (Serbia and Montenegro) were performed at five locations, in June and September, 2003. Results of the qualitative, quantitative and saprobiological analyses of plankton and macrozoobenthic communities were used for the water quality assessment and the categorization of the watercourse examined. The bioindicator analysis points to the presence of mild organic pollution, water quality varying between the 2nd and 3rd class.

The paper presents the results of investigation of benthic algae of the river Rasina. During April, 2001, it was determined 110 algal taxa from the divisions Cyanophyta, Bacillariophyta and Chlorophyta, which indicate the high biodiversity of algae in this river. With 97 algal taxa, Bacillariophyta is dominant. The community of benthic algae is typical for this kind of aquatic ecosystem during the spring period. Great number of algal bioindicators of highly polluted water indicates the presence of high concentration of organic compounds in this aquatic ecosystem.

Advancement in microbiology reveals new potentially pathogenic water borne microorganisms. Because of inconvenient water works, World Health Organization and legislators necessarily standardize guidelines and codes for potable water examination. Water works with safe water treatments and distribution systems obey the rules of routine control, and that is why they do not recognize more sophisticated sides of microbiological water quality. From that point of view, poorly studied slow growing chemoorganotrophic bacteria resistent to environmental conditions are interesting.

During 2003 the referent monitoring of chemical quality of surface waters and sediments in Vojvodina (Serbia, Serbia and Montenegro) was conducted as a supplement to the regular monitoring program in Vojvodina. The aim of the study was to establish the chemical quality of surface waters and sediments. It is concluded that the water quality satisfies the criteria of the 1st/2nd class according to our legislation, with the exception of a few monitoring stations which showed a slight contamination with mineral oils and polycyclic aromatic hydrocarbons (PAHs)/ With regard to contamination of sediments with PAHs, organochlorine pesticides and polychlorinated biphenyls (PCBs) the Begej-Klek monitoring station may be considered as potentially problematic as the reference values according to Dutch legislation were exceeded for three classes of pollutants.

The paper presents the results of the water quality studies of the Sava river in Belgrade region (Serbia and Montenegro). The investigations were performed in June and September, 2003. The sampling area covered five locations along the 61.5 km of the river course. Studies included the qualitative, quantitative and saprobiological investigations of plankton and macrozoobenthic communities. The bioindicator analysis points to the presence of mild organic pollution indicating thus 2nd and 3rd-2nd class of water quality.

In this paper we have presented the results of the investigations of phytoplankton carried out in the river Old Begey, from April 2003 till February 2004. The presence of 116 algal taxa of which 10 Cyanobacteria, 20 Euglenophyta, 50 Bacillariophyceae, 3 Chrysophyceae, 30 Chlorophyta and 3 Dinophyta was recorded. In the river Old Begey some rarer brackish species Entomoneis alata and Bacillaria paradoxa have also been found. The index of saprobity given on the basis of Pantle-Buck method indicated that the quality of water of the river Old begey belonged to beta-alfa-mesosaprobic category.

One of major direction of algology development in Serbia is completing data about bioindicating values for saprobic system based on the existing list of bioindicators. This work shows the results of several year's investigation of macroalgae in streams that belong to the Danube river watershed. Altogether, 72 taxa belonging to six divisions were found in the investigated streams. They were as follows: Cyanophyta (34 taxa), Rhodophyta (8), Xanthophyta (6), Chrysophyta (1), Chlorophyta (22) and Charophyta (1). Analysis of the list of species found in streams of highland regions of Serbia and the List of Indicatory Species reveals that 50% (36) of the species found have definite indicatory values. This work presents the data obtained for species that are not on the existing lists of indicators.