Stephen F. Blanchard 1983 Water quality data are presented, measured at the Potomac River at Chain Bridge at Washington, D.C. for the 1978 water year. Samples were generally collected twice a week and more frequently during periods of high flow. The samples were analyzed for nitrogen, phosphorus, silica and suspended sediments. (USGS) application/pdf 10.3133/ofr83147 en U.S. Geological Survey, Water quality of the Potomac River at Chain Bridge at Washington, D.C.; hydrologic-data report, 1978 water year reports