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.

The paper contains description of potential approaches to better defining of distribution curves parameters for low water levels on water courses that sporadically dry up, also including additional information on the length of dry period. Computed results are given for the example of minimum annual discharge on several rivers in the Velika Morava basin, Serbia (Serbia and Montenegro).

Wastewater from the Novi Sad Oil Refinery, Serbia (Serbia and Montenegro) had been previously discharged to the Danube river between the raw water wells. In order to protect water supply source, the collector discharge was displaced downstream, outside the raw water wells area. In 2004, the quality of Danube river water and sediment was monitored at the sites of the old and new collector discharge of the Oil Refinery wastewaters, as well as at two control (reference) sites. The paper presents chemical quality parameters of water and sediment, characterizing oil contamination. Significantly increased contents of oil contaminant were measured in the Danube river sediment at the old discharge site compared to other sampling points, which is a consequence of many-year accumulation, as well as in the Danube river water at the new discharge site, as a consequence of the present wastewater discharge.

During the 2004 research of Moraca river water quality was conducted onto six localities: Pernica, Zlatica, Gradska plaza, Kolektor, Grbavci and Vukovci. Physical, chemical and microbiological properties were analyzed. Physical and chemical analyses done were: water temperature, air temperature, pH, electro-conductivity, KMnO4 consumption, dissolved O2 and BCO5 (biological consumption of oxygen in five days). Microbiological analysis included determination of the total number of aerobic mezophyll bacteria, oligotrophic and heterotrophic bacteria, as well as the most probable number of colliform bacteria. In addition to distribution and population dynamics, identification of the bacteria was also done. Microbiological water analysis were performed using standard bacteriologic methods and identification of the bacteria using INVIC or, when needed, using API diagnostics.

During 2004 the referent monitoring of chemical quality of surface water and sediments in some protected areas in Vojvodina 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 water and sediments. It is concluded that the water quality satisfies the criteria of class 1/2 according to national legislation. With regard to contamination of sediments with organic micropollutants the sediment of Lake Ludos may be considered as potentially problematic because the Canadian empiric effect guideline value as well as sediment quality reference values according to Dutch legislation were exceeded for DDT and its derivatives.

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 research of phytoplankton in water of Hydrosystem DTD in Banat region (canal complex and the rivers Zlatica, Old Begej) has been carried out seasonally i.e. in the spring, summer, autumn and winter of 2003 and 2004. According to guidance of Anon (2003) we selected biological element - phytoplankton in establishing referral body of water with maximum ecological potential (MEP) of the Danube-Tisza-Danube Hydrosystem also classified as artificial/heavily modified water. Classification was made according to Sorensen indices of similarity. Reference conditions with MEP were assigned to the HS DTD, canal Banatska Palanka - Novi Becej, Novi Becej - Melenci stretch. As determined by phytoplankton analyses, investigated canals and rivers could be classified as waters of good ecological potential, except the rivers Zlatica, Stari Begej (Old Begej) and some sections of the Canal Plovni Begej (Navigable Begej) what was designated to moderate ecological potential.

According to the Programme of systematic examination of surface water quality of the Republic Hydrometeorological Service of Serbia the examinations of Medjuvrsje water reservoir have been carried out during October 2002 and August 2003. The examinations have been carried out at the dam, in central part and at the entrance of the water reservoir, on three depths. This paper shows the results on phytoplankton composition, chemicophysical properties and the trophic status of water reservoir. The qualitative analysis of the phytoplankton shows the presence of 96 taxa from six divisions of algae. Following the standard of Swedish Agency for Environmental Protection, the high concentrations of primary nutrients belong to the fifth class, by the categorization. According to OECD classification trophic status of water reservoir may be characterized as eutrophic and hypereutrophic.

In the last few years, in Montenegro there were positive movements into fulfilling the principles of sustainable marine fishery, primarily throught introducing the Law on Marine Fishing and its rules. Institure of Marine Biology in Kotor, Montenegro, in cooperations with the Ministry for Agriculture, Forestry and Water Management of the Republic of Montenegro, works on undertaking of the measures that may ensure optimal regulation of fishing. These measures were based on scientific research, particularly on the estimates of parameters of population dynamics, biomass and maximum biologically sustainable utilization of economically important species on Montenegrin coast.

In this paper modern instrumental techniques for monitoring, control and determination of water and waste water quality parameters are presented. The efficient and reliable control of quality of water can be achieved by integrating the central, referee laboratory, the laboratory on-field for quick and adequate responses, and in-field laboratory, as well as the measurements enabled with the use of chemical sensors that are installed on the places with the highest contamination. Beside equipped laboratories every monitoring system has to be connected with the latest informational systems which beside data base provide adequate response when the water is exposed to higher contamination.