Studies have indicated that water quality is degraded as a result of long residence times in storage tanks, highlighting the importance of tank design, location, and operation. Computer models, developed to explain some of the mixing and distribution issues associated with tank operation, were successfully used to predict the effect of tank design and operation on various water quality parameters. But because of the diversity of the effects and the wide range of design and environmental conditions, general design specifications for tanks are unlikely. Rather, the authors recommend that modeling be refined to facilitate site-specific analysis. Includes 17 references, table, figures.