Withdrawal of water from surface water network should be concerned with preservation of the environment, meaning that the low flow regime in streams should be preserved within the range of natural regime. In order to formulate criteria for minimal allowed flows in streams, it was necessary to perform statistical analysis of low flows in rivers in Serbia (Yugoslavia). The criteria for water withdrawal are proposed on the basis of characteristic ratios between minimum and mean flows. Different criteria are proposed for cold and warm seasons.

Paper points the present water quality of the Moraca river (Montenegro, Yugoslavia), from rivermouth of Zeta to Skadarsko jezero lake. Hydrological analysis, level of water pollution are also presented, together with proposed water quality protection measures regarding the Yugoslav federal regulations for surface waters.

The investigations of the macrozoobenthos of the Crvena Reka river (Serbia, Yugoslavia), left tributary to the Nisava river, were performed during July in 1999. Samples were collected from 15 localities, from the spring of the Crvena Reka river (originating from Toponicka and Vetska rivers) to the lower course, the aim being to investigate the diversity of macrozoobenthos of these running waters which had not been investigated. The community of macroinvertebrates of the Crvena Reka river and the streams, which make it, consists of 54 determined taxa (at species and genus level) from 16 animal groups. Larvae of Ephemeroptera and Trichoptera have the greatest diversity, each having ten determined taxa. The middle course of the Topnicka river (locality T4) is characterized by the greatest diversity (25 taxa), while the springs (due to constant ecological parameters) have poor diversity with two and one determined taxa in locality V1 and V2, respectively. The water quality of the investigated river and streams, which make it, on the basis of the results of saprobiological analysis, is of beta-mezosaprobic quality, i.e. second class of quality in most localities.

This paper points out the role and significance of civil engineering in dealing with the problems related to the water environment. Examples presented consider hydraulic structures and their impact on the aeration level in the watercourse. Aeration and reaeration have the most important effect on the oxygen water quality parameters and therefore on the entire living world in the particular ecosystem.

This paper is an abstract of the operative program for water protection in the Republic of Serbia (Yugoslavia) for the next five-year period of time (2001-2005). There is a short review on the present water protection status, particularly status of wastewater treatment plants. It includes layouts of water protection solutions in different fields, by priorities, as well as assessment of necessary capital investments for their implementation.

The paper deals with the results of the phytoplankton investigations carried out in the 7 localities along the Yugoslav section of the Tisza river in the period of 13 Februar - 3 March 2000, after accidental pollution with the cyanide and heavy metals. Although certain decrease in the density of the phytoplankton and variation in the qualitative and quantitative composition were recorded, there are no significant differences in comparison with the data before accident. The short-term and possible long-term consequences were recognized, having in mind ability of algae to accumulate pollutants into their cells, and that algae are the first link on food chains. Since the content of pollutants increases with every next member in the chain, it is easy to assume cumulative effect of the all previous members.

Aerobic bioremediation of oil contaminated soil was investigated on laboratory-scale for purpose of pilot-plant installation. Mineral oil was analysed using IR spectroscopy. Sediment was qualitative analysed on GC/MS. Research also included microbiological analysis.

The photocatalytic degradation of the insecticide fenitrothion was performed in the water solution in the presence of TiO2 by UV illumination. NMR spectrocopy showed that the decomposition of the initial substrate and all intermediates formed to the mineralization end products is completed in 66.3 hours. This fact was used to establish the possible mechanisms of the degradation process. The obtained results show that this method may have an important application in the removal of fenitrothion from water.

During complex studies of phytoplankton, the role of particular phytoplankton groups was examined, as one of important indicators of eutrophic processes in the Bay of Boka Kotorska (Adriatic sea, Montenegro (Yugoslavia)). Throughout summer 1999, investigations have been performed at representative locations (Kotor, Tivat and Hercegnovi bays) at the depths of 0, 5, 10 and 20 m. Maximal values of microphytoplankton were found in Kotor Bay in July (2.1 x 10**6 cells/cubic dm). In Tivat Bay, maximal values of microphytoplankton were found in June, although they were ten times lower (2.4 x 10**5 cells/cubic dm). In the Bay of Hercegnovi, mean values were lower, while maximal quantity of microphytoplankton was found in August (2.6 x 10**3 cells/cubic dm). In the Boka Kotorska Bay, the maximal percentage of 95% of the group Bacillariophyceae was found in the most productive surface layers at the depths of 0 and 5 m. The impact of eutrophication was the most visible in the Kotor Bay. It decreased towards the open sea. Diatoms populations (Bacillariophyceae) were dominant in the Bay, while the participations of other groups is insignificant. Consequently, it means that Bacillariophyceae are the most adapted group to the eutrophic conditions of the Boka Kotorska Bay.