Water Self-Purification in the Mozhaisk Reservoir in Winter

The results of determinations of the concentration and demand of oxygen for the decomposition of organic substances in water masses and bottom sediments of the low-flowage Mozhaisk reservoir are presented. The considerable spatiotemporal variability of these characteristics within this ice-covered water body is shown to be controlled by differences in the temperature, salinity, and organic matter content of different water masses constituting this ecosystem. It is noted that this water body forms a winter-type density stratification and oxygen-bearing circulation of waters that is caused by a density current. On the basis of daily O^sub 2^ budgets calculated by means of a quasi-two-dimensional hydrological model of the reservoir, the processes of the winter self-purification of water are shown to account for 50% of the oxygen supply. The discrepancy of this model was shown to be < 5.5% both for the entire water body and for its four constituent regions.[PUBLICATION ABSTRACT]