In the period of 1993-1996 water quality of the Bajski canal (Serbia, Yugoslavia) was followed using certain chemical and biological parameters. Oxygen control ranged from its deficiency to its supersaturation recorded in spring and early summer which moved down in summer and early autumn. A smaller amount of suspended particles points to a sedimentation process provoked also in the canal bed, clearing the way for the development of macrophytes. A diverse zooplankton showed typical seasonal variations. A total of 73 species was recorded including 13 Protozoa (17.8%), 44 Rotatoria (60.3%), 10 Cladocera (13.7%), and 6 Copepoda (8.2%). In summary, the process of water quality deterioration is less evident in this section of the DTD (Danube-Tisza-Danube) hydrosystem (Serbia, Yugoslavia).

Drainage of industrial and communal effluents, directly into the water flow, as many hydrotechnical activities, significantly influence the schedule and balance of the processes that take place into water. In this paper, there are represented the results of systematic control of the water quality of the Danube river and DTD (Danube-Tisza-Danube) channel on the parts Vrbas-Bezdan and Becej-Bogojevo, at the control station network of the Republic Weather Bureau (the Republic of Serbia), for the period of 1991-1996. The results show that the most adverse influence of anthropogenic factor is on the part of the flow of the DTD (Danube-Tisza-Danube) channel from Vrbas to the flow into Tisza river.

During one-year examination of the Vlasina river and its main tributaries, the Luznica and Gradska rivers, Serbia (Yugoslavia), in May 1996, the samples were taken for biological and chemical analysis of the watercourse in the spring aspect. Sampling was performed on the five localities of the Vlasina river, and two tribute localities near the mouth thus including all critical points where the changes of physico-chemical water parameters and qualitative/quantitative biocenoses compositions due to the increasing anthropogenic influence could occur. Data on phytoplankton, zooplankton, periphyton and benthos were analysed together with the physico-chemical water parameters in order to determine communities composition and structure and bioindicator species. Based on these results the status of aquatic environment i.e. water quality, was evaluated.