Water quality analyses were performed on littoral water samples, collected on Lake Ohrid in 2002 (January, February, June, July, August and September). Several microbiological parameters were compared. The number of Escherichia coli, the number of organotrophic bacteria and the phosphatase activity index were measured. Samples were collected along the shore of Lake Ohrid, i.e. at the village of Pestani, at Hotel Metropol, in Ohrid Bay and at the lake inflow of River Velgoska. The results of the study show that the different parameters are not compatible in terms of water quality characterization. The differences found are discussed below.

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.

The activities acid, neutral and alkaline phosphatases, as well as total phosphatases activities were estimated in the water of the Lake Ohrid tributaries Sateska, Koselska, Velgoska and Cherava. The same analyses were performed in the littoral zones where the tribitaries enter Lake Ohrid. The study covers the period from September 2000 to October 2001. The obtained results show that different types of phosphatase effect different extracellular activities, an observation which is probably the result of differences in the location within the cells and the way of intracellular synthesis.