A MODEL FOR ENHANCED AERATION OF STREAMS BY MOTOR VESSELS WITH APPLICATION TO THE SEINE RIVER

The transport of molecular oxygen, a natural chemical, into water from air is of critical importance in maintaining water quality of bayous, canals, waterways, rivers, harbors, estuaries, etc. Research on this classical environmental engineering intermedia transport process has received considerable attention for decades, however its ongoing significance demands continued research. The Seine river in France is a typical example of a river that serves multiple purposes and a detailed analysis of all the oxygen transport mechanisms is needed. Following a brief review of the known mechanisms of O2 transport a combined momentum balance plus propeller surface aerator model is proposed to account for reaeration by motor vessels moving on waterbodies. The potential importance of this mechanism is put into context through a brief case study of the Seine where flow and dam hydraulics induced reaeration, along with wind-enhanced reaereation, are quantified. The primary objective of this paper is to develop a model for estimating the aeration contributed to streams and waterbodies by vessels moving on the surface. First the general subject of the oxygen balance and stream reaeration is introduced. This is followed by a brief review of the two natural aeration mechanisms, flow and wind, that are active in all streams. The environmental situation at Porcheville, France on the Seine river 75 km downstream of the center of Paris, is parameterized for developing numerical estimates of the aeration process for each mechanism. After the theoretical model for vessel aeration is developed a case study of aeration on the Seine is used to illustrate the potential significance of vessel aeration in the context of other mechanisms including dams. The paper concludes with statements on the state-of-knowledge and the scientific/engineering needs on the subject.