Atmospheric Oxygenation in a Simulated Stream

A simulated stream channel was used in laboratory investigations to determine a rational expression relating stream variables and fluid properties which define the reaeration rate constant, k2. Direct measurement of the reaeration coefficient at controlled depths and stream velocities enabled the development of a dimensionally homogeneous expression for k2. The developed expression accounts for variations in k2 due to changes in temperature as well as changes in fluid flow conditions. For the rectangular cross section employed in these studies, the reaeration rate constant, k2, was found to be directly proportional to average stream Telocity, and inversely proportional to the average stream depth raised to the 3/2 power. The constant of proportionality was found to be 3.053. When the same analytical approach was applied to the best available natural stream data, the proportionality constant obtained was 3.739. Both analyses yielded highly acceptable correlation coefficients. It is believed that the difference in the values of the proportionality constant is due primarily to differences in channel geometry, i.e., smooth rectangular laboratory channel versus irregular-shaped natural river channels.