Browsing by Author "Daniil, Ekaterini I."
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Item Dissolved Oxygen Investigation Coon Rapids Hydroelectric Redevelopment Project(St. Anthony Falls Hydraulic Laboratory, 1988-05) Olivier, Cecilio; Daniil, Ekaterini I.; Gulliver, John S.The Coon Rapids Dam is located in Hennepin County, Minnesota, on the Mississippi River approximately four miles downstream from the City of Anoka and approximately twelve miles upstream from the downtown section of Minneapolis. The structure was transferred to the Hennepin County Park Board by Northern States Power Company in 1969. Since 1969 the structure has undergone considerable modifications to make the facility meet its new recreational role, with the installation of walkways and observation platforms. The hydropower redevelopment at Coon Rapids will send between 1,000 and 8,000 cfs (the range of discharge for the turbines), which previously passed over the spillway, through the turbine units. This will have an impact on downstream D.O. concentrations because the spillway is an excellent aerator, increasing D.O. concentrations, while the turbines do not add any air to the water.Item Impact Assessment of Hydropower Development on Dissolved Oxygen at the Byllesby Dam(St. Anthony Falls Hydraulic Laboratory, 1989-03) Daniil, Ekaterini I.; Thene, John R.; Gulliver, John S.Lake Byllesby Dam is located along the boundary between Dakota and Goodhue Counties, on the Cannon River, approximately 2 miles west of the City of Cannon Falls, Minnesota.Item Influence of Waves on Air-water transfer of low solubility gases(1987-12) Daniil, Ekaterini I.; Gulliver, John S.Water quality of rivers and reservoirs or lakes is a main component of the quality of life in a state like Minnesota, where free surface waters are abundant. A major key to managing water quality is dissolved oxygen concentration. Low oxygen concentrations result in fish kills, gaseous . releases from sediments, and the release of toxic chemicals from sediments. The understanding of oxygen dynamics is therefore imperative in order to predict the impact of future developments along a river. One of the main ways of oxygen replenishment is the transfer of oxygen from air into the water through the water surface (reaeration). Reaeration in river reservoir systems. occurs most effectively through the turbulence of flowing water, turbulence and surface waves caused by the wind, and air entrainment caused by flow over hydraulic structures. Recent studies of air-water gas transfer and comparisons between large and small wind wave flume data have indicated the potential importance of waves in the gas transfer process. Experimental evidence is presented in this paper showing that. non-breaking deep-water gravity waves significantly influence gas transfer. Experiments were performed in a flume with a mechanical wave maker. Oxygen was used as a tracer gas, and the flume was chemically deoxygenated. Oxygen concentrations and wave characteristics were recorded over time at various locations along the flume. Horizontal mass transport was determined from conductivity measurements, using salt as a conservative tracer. Semi-empirical correlations of the transfer velocity and the wave characteristics were obtained. The transfer velocity is shown to increase proportionally to both wave height and frequency. Comparison against data reported in the literature indicates that approximately 50 percent of the observed gas transfer in wind wave flume experiments can be attributed to non-breaking waves. The presence of bubbles or bubble entraining breaking waves enhances the transfer velocity considerably. Visual correlation between breaking intensity and the transfer coefficient was very good, although the relation has not been quantified.