Flushing of a lake means reducing the pollution by clean inflow with an equivalent outflow of polluted water, a process by which clean water both displaces and mixes with the polluted water. Parameters influencing the effectiveness of the cleansing stream, most important and manageable under laboratory conditions, were investigated. Parameters studied were: inlet velocity, inlet width, depth, and basin shape. Testing was conducted on two depths, two inlet widths, three inlet velocities, and four elliptical basins. Primary purpose of the project was to evaluate the various parameters to determine their influences on flushing efficiency, and develop prediction equations based on geometric and flow characteristics of the systems tested. Analyses were completed to develop a test program, analyze the system for comparison with experimental results, and develop prediction equations which incorporate analytical and experimental results of the study.