ABSTRACT
Construction of the run-of-the-river reservoir of the hydroelectric power plant Djerdap I in the Danube river basin covering 817000 km2, with the flux from 1950-16000 m3/s, and retention time from 6-14 days, the conditions for deposition of big masses of sediments have been established. In the project the deposition and removal of suspensions from the reservoir in a ratio 1: 1, in first 27 years, in an absolute amount of 20 Mt/g, have been foreseen. During exploitation it was found that the total inputs were overrated, but the retention rate was far underestimated, what has particularly been analyzed in this work. During investigations of the water quality changes in the reservoir an exceptionally attractive phenomenon has been ascertained, related to the reduction of primary production and precipitation of planktonic mass from the upstream section into the reservoir. Since the Danube river basin, with tributaries feeding the reservoir, is rich in nutrients and with a high organic production, the total deposited sediments exhibit the high percentage of organic constituent. In the paper have been analyzed conditions of precipitation in the reservoir by use of sedimentological analyses and contents of organic mater, whose participation in the increased efficiency of precipitation was analyzed considering the analysis of changes of the particle's ceta potential in the turbulent flow. The suspended deposit has fixed by itself the numerous toxins, metal ions, organic micro-pollutants (oil derivatives, pesticides, PCBs); that is why the destiny question of these materials in the sediment is of the primordial importance. In the paper have been analyzed solutions of recovery of influence of sediments with the high toxic substance's contents, whose eluation particularly in the intensified process under the increased temperatures, has limited the development of the living world in the reservoir and in the downstream sector.
