A simplified continuous receiving water quality model has been developed as a planning guide to permit preliminary screening of areawide wastewater management strategies. The model simulates the hypothetical response of the stream or tidal river system to the separate and combined effects of waste inputs from upstream sources, dry-weather urban sources and wet-weather urban sources. The total hours of runoff-producing rainfall throughout a year are separated into storm events. For a given storm event, the runoff and pollutant loads are summarized, and critical dissolved oxygen concentrations are estimated as a function of several hydrodynamic and biochemical parameters. An application to the Des Moines River at Des Moines, Iowa, is presented.