Cooling Water Density Wedges in Streams

The length of warm water density wedges measured in streams receiving power plant discharges is adequately predicted by equations based on two-layer flow theory when proper evaluation of the variables involved is made. The formation of density wedges in the vicinity of power plant discharges is an important consideration in both the design of cooling water intakes and the possible thermal pollution of the receiving water body. Equations have been developed by other authors which may be solved for the length of a density wedge given the density of the wedge, the initial depth of the wedge, and the magnitude of the frictional forces involved. Wedge length data obtained from four power plant sites are compared to the prediction of the equations. The predicted wedge length is found to be least sensitive to the initial wedge depth chosen, more sensitive to the magnitude of the frictional forces chosen, and most sensitive to the density chosen. Densities based on plant discharge temperature are found to always be less than that actually measured in the wedge.