As part of the Chesapeake Bay-Susquehanna River Basins Project, the Chesapeake Technical Support Laboratory of the Middle Atlantic Region, Federal Water Pollution Control Administration has undertaken an extensive water quality management study of the Potomac River Basin. A significant part of this study has been to determine the effect of organic matter including nutrients on the water quality in the upper Potomac Estuary. The study was limited to diffusion, dispersion, and dilution effects of the receiving water. Two dye releases were made in the main channel of the Potomac Estuary to simulate the movement of the effluent from the proposed outfall of the Piscataway Wastewater Treatment Plant.