The diffusion of erosive processes in Serbia and frequency of torrential floods are the factors of degradation of environment. Communities in Serbia are obliged to make Plans for announcement of erosive regions and for protection by torrential floods on water courses out of regular system of defense. An example of Belgrade is presented in this paper, where the Plans for announcement of erosive regions and defense by torrential floods were carried out. These documents are the basis for water protection and usage of natural resources on the concept of sustainability.

A new concept for the determination of reference low flows of natural watercourses - the guaranteed minimum - has recently been introduced into the water management practice. Appreciating the significance underlying the definition of low flows in all segments of water management (municipal and industrial water supply, wastewater discharge, irrigation, navigation, hydropower, water protection, etc.), the author believes that all aspects of the problem must duly be considered, examined and identified. The doubts and issues raised by the guaranteed minimum concept in the domain of random-probabilistic phenomena, such as river discharge, are discussed in the paper.

One-year monitoring program was organized with the aim to assess the quality of sediment and water in some protected areas in Vojvodina regarding metal content (Cr, Cd, Cu, Ni, Pb, Zn, Hg) in them. Water was class 1/2 according to national requirements. Canadian probable effect guideline value for sediment quality is occasionally or constantly exceeded for all metals. Obtained results gained preliminary overview of water endangerment in watercourses.

In this paper we have presented the results of the investigation of phytoplankton carried out in the Hydrosystem DTD (Danube - Tisza - Danube) in Banat region from April 2003 till November 2004. Accordingly, halophilic algae community of eutrophic type has been described. Seasonal distribution and presence of algae taxa in the investigated water varied significantly. The diatoms were mostly represented by periphytic forms in the huge quantities, which was particularly the case with an avalanche of the eutrophic species such as: Bacillaria paradoxa, Anomoeoneis sphaerophora, Nitzschia acicularis, N. palea, Navicula cryptocephala, Fragilaria ulna, Melosira varians, Surirella ovalis, etc. The significant number of Cyclotella meneghiniana during summer and Euglenophyta in autumn revealed high trophic status in some sections of HS DTD.

The river Crnojevica is a subject of lasting manny years physicochemical and microbiological investigations, which show worring pollutants presence into the water current. This work represent preliminary investigations of Crnojevica river water algal flora (phytoplankton and phytoperiphyton), carrying out over summer period of 2004. Aim of the investigation was to point, based on algal analysis, as reliable indicators of water quality and ecological status of an aquatorius, the need to protect the river from permanent communal and industrial waste water pollution. The hyperproduction of phytoplankton in the investigation period was stated, but it varys along the current, in accordance with efluent inflow. On the base of saprobiological analysis of phytoplankton, determinated water quality was in class 2, till the worse was noted at T2 measure place, on the inflow place of Rijeka Crnojevica settlements sewage.