The most extended and deepest belt of macrophytic vegetation, the belt which almost without exceptions define the lower limit of littoral region of Lake Ohrid, consists algae from the family Characeae. Permanent presence of sunlight, well oxygen saturation, their density which decreases the waves action, together with the facts that these algae are food and shelter for the numerous endemorelic species from the very rich fauna of macro invertebrates, make the stonworts the most attractive life habitat in Lake Ohrid. Our results are found on researching of three types facies from four different localities in Lake Ohrid: sandy-muddy facies without of stoneworts, facies covered by stoneworts and facies covered by Gastropod and Bivalvia shells, also without of stoneworts. Without exceptions, in all four localities we approved the mentioned affirmation about the great importance of the stoneworms as life habitats, both by the number of present taxa and the density of the macro invertebrate communities.

The basic purpose of Gruza accumulation is to supply the town of Kragujevac and its vinicity with drinking water. The accumulation occupies large area, comparing with its relatively shallow water and low water mass, which is essential for water eutrophication. The aim of this research is to determine water quality, through index of phosphatase activity at five locations in one year period. According to the results obtained for index of phosphatase activity, water of Gruza lake belongs to 3rd A category. The maximum obtained value (19.60 micromol/s/cubic dm) was determined in the shallow part, at mouth of the river Gruza in July, 2000, and the minimum one (0.39 micromol/s/cubic dm) in the deepest part of accumulation, at location Brana in March, 2001.

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.

Every country must to concern the biodiversity of flora and fauna, especially in ecosystems rich with endemic and relict species. Such ecosystem is the Lake Ohrid.

In this paper, we present the results from both quantitative and qualitative composition of the Gastropod fauna from Lake Ohrid (profile HBZ-Radozda) with their vertical distribution in littoral and sublittoral region of the lake. The results of our investigations shows some changes in biodiversity and the density of gastropod communities that settle this profile, compared with the investigations made 30 years ago.

The paper deals with pilot-scale investigations of the effect of preozonation on NOM removal from groundwater by coagulation and flocculation processes. It was found that the preozonation increased the efficiency of organic matter removal by coagulation and flocculation from 23.6 to 47.2% as judged on the basis of KMnO4 values. From the aspect of the change of content of trihalomethanes precursors preozonation exhibits both the positive and negative effects if their content in the water after coagulation is considered in dependence of the applied ozone dose. The obtained values siggest the necessity of careful optimization of the processes of preozonation, coagulation, and flocculation, especially from the aspect of the change in content of the precursors of disinfection byproducts.

Heavy metals contamination of the muscular tussue of nase (Chondrostoma nasus), bream (Alburnus brama) and bleak (Alburnus alburnus) fish species from the Medjuvrsje water reservoir (the Zapadna Mora river), was examined. With the expection of the nase muscular tissue where cadmium (Cd) and mercury (Hg) concentrations above and slightly below MPC, respectively, were detected, the rest of the samples were safe. With the aim of conducting more thorough monitoring of these pollutants, a greater number of elements and a larger number of organisms should be included in the analyses.

The paper presents results of research on hydrophilic flora of the Grosnica reservoir in the Kragujevac basin (Serbia, Serbia&Montenegro). The obtained results confirm that the development of hydrophilic vegetation is dependent on the time, manner, and place of reservoir formation, as well as on the extent of human influence. Analysis of floristic composition of hydrophilic plants of this reservoir indicates presence of 30 species belonging to 20 families. Floristic composition of the hydrophilic flora with flora elements, life forms and ecological factors are presents.

In the period October 2001 through November 2002 in six series parallely with physico-chemical and hydrobiological analyses, the content of photosynthetic pigments was determined in algae in the region of flow-through reservoirs of "Djerdap 1" and "Djerdap 2" on the profiles of Smederevo, Ram, Veliko Gradista, Donji Milanovac, Tekija, Kladovo and Radujevac. The samples were taken by a pump from the river midstream at the depth of 1-0 m (composite sample), while in the vegetation period April, June and September, the samples were taken at the depth of 5 m. The peak concentration of chlorophyll-a, the biological indicator of trophic condition, was recorded in the month of April in the Smederevo profile (30.2 mg/cubic meter) at the depth of 1-0 m. The lowest values of chlorophyll-a in all studied cycles were recorded in the Radujevac profile (below the dams) with the mean annual value of 1.8 mg/cubic meter. Chlorophyll-c occurs as the subdominant photosynthetic pigment. Values of chlorophyll-c were higher than chlorophyll-a in the month of June on the Donji Milanovac profile in the analysed sample taken at the depth of 5 m. Higher values of chlorophyll-b were recorded in the course of the vegetation period in the month of June on the profiles of Smederevo, Ram, Veliko Gradiste and Donji Milanovac at the depth of 1-0 m.

According to Water Plan of the Republic of Serbia the area between Kovin and Dubovac was marked as a possible place for water source for regional water supply of towns and industry of South Backa Region (Serbia). Commencement of underwater coal exploitation was at the beginning of 1990's in the Danube riparian zone near Dubovacka Ada. Potential influence of long-term underwater coal exploitation from "Kovin" trial coal pit on Dubovacka Ada on quality and quantity of groundwater that will be extracted from regional water source is analysed in this article.