During hydrobiological investigations of the river Dulenska (Serbia, Yugoslavia) in June 1996, algological samples were taken at this river. In the algae community are found 34 taxa from two divisio: Bacillariophyta (28) and Chlorophyta (6). While qualitative composition of the algae colony was relativelly uniformed quantitative one was changeable along the course of the Dulenska river. By saprobiological analysis, it was found that the quality of water was changing along the course of the river. At the upper and middle course of river the water belonging to the second class. At lower course of the river (below Rekovac) water quality was getfing worse and it belonging to the third class.

The monitoring the content of organochlorine insecticides and polychlorinated biphenyls in heterogeneous system of water-sediment is of a primary interest for the researching of contamination of the aquatic ecosystem because of high bioconcentration factors of these compounds and their bioaccumulation in flora and fauna of the aquatic basin. The sampling of water and sediment were done in the Boka Kotorska Bay (south Adriatic Montenegro Seaside), and estuary Bojana - Ulcinj, Montenegro (Yugoslavia), in AuTumn of 1995. The residues of organochlorine insecticides and polychlorinated biphenyls were determined by gas chromatography, Varian 3400 with capillary columns OV-101, length 25 m, with ECD. The residues of isomers of HCH (hexachlorocyclohexane), DDT and PCB (polychlorinated biphenyls) were identified in all investigated samples.

Drought characteristics (minimum flows, drought duration and volume deficit) of the Moraca river near Podgorica, Montenegro (Yugoslavia) are analyzed using the peaks over threshold method based on renewal processes. It is also shown that volume deficit and drought duration are highly correlated.

Neither soil nor water has very distinct function when seen in isolation. Therefore, analyses of water and soil can get real value only by their linkages. Taking into consideration irrigated land, water and soil interaction degree can cause different changes of soil, plants and aquifer A. All negative changes which are occur in the soil (in case of using unsuitable water quality for irrigation or applying of not rational fertilizers amount) have influence to the changes aquifer A quality. Interaction between soil and aquifer A are require investigation of groundwater quality changes relating to plant production, especially in irrigation. Intensity and type of aquifer A properties change, in case of different soil use in agricultural production, have been studying since 1991 at the Lysimetric Station Rimski Sancevi (Serbia, Yugoslavia). The results are point out satisfactory quality of aquifer A after irrigation with wastewater and well water, and applying of different mineral fertilizers amount. The soil capability to receive water with unsuitable quality, to influence their change and change of aquifer A quality as the final recipient, are showed by received results.

The work describes optimization on the process of separation of a synthetic dye, methyl orange, from water by sorption on iron(II) hydroxide, using response surface methodology. It was established that the optimum sorption conditions for dye removal on iron(II) hydroxide are: pH 9.1, iron(II) concentration 128 mg/l, dye concentration 10 mg/l, whereby the highest efficiency of dye removal is close to 90%.

Nowadays, different profile of experts are present opinion that surface water quality are exchanged. Type and degree of mineralization content exchange are shown by argumentation. The work have carried out taking into consideration suitability of Danube water for irrigation. The results of chemical investigation from three sample locations (Bezdan, Novi Sad and Banatska Palanka), Serbia (Yugoslavia) during the period 1981-1995, were analyzed. The main statistical parameters and tests of homogeneity are used during the work. Results have pointed put more or less concentration decreasing of analyzed parameters. From statistical point of view, exchange of electrical conductivity and potassium are prominent on all three localities.

The river Tara (Montenegro, Yugoslavia) is under the treatment of the international (UNESCO) and domestic legal protection, so the prescribed quality of its water is the 1st class. Permanent measurement of the water quality of this river shows that due to the influence of the human factor, its quality has been endangered. Examination of the data collected through many years at all the measurement station along its current shows that the quality of water and pollution estimate have changed.

The paper provides a report on the quality of water of the Kolubara river and its tributaries, the Ljig and the Pestan, for the period 1992-1996, on the basis of results obtained in the course of regular examinations carried out by the Republic Hydrometeorological Service of Serbia (Yugoslavia). The examination of the waters of the Kolubara river region is significant in view of the vinicity of developed industry, since the wastewater of such an industry represents a potential pollutant of the adjacent rivers. The paper also provides a separate review of the heavy metals contents of the examined rivers. The obtained results indicate to periodical deviations of the water from the required quality, that represents, without any doubt, the pollution of anthropogenic origin.

Thermal stratification is regularly found in deep lakes, while shallow water bodies remain usually mixed. Despite comparative shallowness, Sava lake (artificial lake), Serbia (Yugoslavia) exibit a prolonged summer stable stratification. Temperature differences between epilimnion and hypolimnion can reach 10 deg C. The steep gradients of up to 3.5 deg C/meter recorded in the metalimnion. The highest differences during a single typical summer day was 1.7 deg C between 0.2 and 0.5 m. Maximum annual thermal accumulation was 112440 J/square cm in 1996.

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.