Investigations were conducted to determine the characteristics of the withdrawal zone resulting from the release of flow through an orifice from a randomly stratified reservoir in experimental facilities for the purpose of developing means of predicting the quality of water discharged through similar openings in prototype intake structures. Distributions of density, generated by differentials in both temperature and dissolved salt concentration, and velocity were observed at various locations within a 1-ft-wide channel upstream of 0.08- and 0.16-ft-square orifices. These data were used to develop generalized expressions describing the limits of the zone of withdrawal and the distribution of velocities therein. Means were developed (Appendix A) for evaluating the conditions under which these boundaries dictate the limits of the withdrawal zone and for determining the distribution of velocities within a zone of withdrawal restricted by boundary conditions. A sample problem (Appendix B) is presented to illustrate application of the results to determine the maximum discharge that may be released through a square orifice for a given set of conditions without exceeding the limits of a desired hypothetical zone of withdrawal. A FORTRAN 4 program is presented in Appendix C. This program can be used to solve three different approaches to the selective withdrawal problem. The effect of orifice shape on the withdrawal characteristics was tested and analyzed after the draft of this report was prepared. The results were believed to be pertinent and are discussed briefly in the Discussion section of this report. (Author).