Complex hydrodynamics and thermal regimes of temperate lakes have a major impact on temporal and spatial distributions of water quality indices. Transport processes in lakes are driven primarily by external forces such as wind and solar radiation but also depend on the inflow and outflow regimes. This paper presents a simplified ID model developed to calculate seasonal variations in vertical distributions of temperature and dissolved oxygen in Lake Zavoj in southern Serbia. Model results that were based on monthly averaged meteorological data are in good agreement with measured vertical profiles of temperature and dissolved oxygen. The simplified model is an efficient tool for long-term prediction of water quality indices in deep, medium and long residence time lakes.

In order to determine the stable isotope content of hydrogen (2H/1H) and oxygen (18O/16O) from surface water and the Zavoj Lake, a sampling campaign was carried out in November 2011. Vertical profiles of water samples were collected in the sections close to the dam to check whether there was any detectable influence from the inflowing Visočica River and wheter there was a vertical isotopic stratification of the lake water. Temperature gradient of up to 5.5 deg C between surface and about 60 m depth is observed. Dominant process of mixing the inflowing Visočica River and water leaking from diversion tunnel appear close to the dam.

Investigation in this study should indicate to importance of aquatic macrophytes in accumulation of toxic metals in aquatic ecosystems and control of their pollution, as well as to establish which plants are well hiperacumulators and test species for remediation, in order to protection, regeneration and conservation of the Gruža lake as reservoir that is important for water supply and as particular natural ecosystem. Obtained results showed that species Lemna gibba L. was reliable indicator of surrounding conditions (environment), as well as good accumulator of heavy metals, so it could be used to remediate aquatic ecosystems.

The Djerdap 1 Hydropower Plant (Djerdap 1 HPP) was joint projects of Yugoslavia and Romania, based upon the principles of equal benefits. The primary functions of the Djerdap 1 HPP are to effectively utilize the available hydropower potential of the Danube and to provide a full navigational capability under any hydrologic conditions. The utilization of the hydropower potential was conditional upon the provision of a Riparian Land Protection System for the Djerdap 1 reservoir, and the timely prevention of any adverse impacts due to the alternation of the natural regime as a result of backwater. ongoing enhancement of the Riparian Land Protection System and study of the various impacts have enabled a continual backwater increase and a resulting increase in the output of high quality power, with no significant risk of adverse impacts.