Publications

Wells in the Gettysburg National Military Park, Eisenhower National Historic Site, and Gettysburg Borough supply drinking water to the park staff and, annually, more than 1 million visitors. These water resources are vulnerable to contamination by pollutants from activities in and outside park boundaries. This report describes the hydrogeology and ground-water quality of a 12-square-...

All water that reaches watershed systems comes directly or indirectly from precipitation. Normally, this water contains very small amounts of dissolved solids and is only slightly acidic. As a result of chemical reactions in watersheds, however, stream water generated from precipitation normally is less acidic and contains larger concentrations of dissolved solids than does the...

Baltic clams (Macoma balthica) were the predominant food items of 323 canvasbacks (Aythya valisineria) collected throughout Chesapeake Bay during 1970–1979. Natural vegetation constituted 4% of the food volume. Widgeongrass (Ruppia maritima) and redhead grass (Potamogeton perfoliatus) constituted the greatest percent volume and frequency of occurrence among the plant species, whereas...

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The characteristics and distributions of near-surface bottom sediments and of nutrients in the sediments provide information on modern sediment and nutrient sources, sedimentation environments, and geochemical reactions in the tidal Potomac system, Maryland and Virginia. This information is fundamental to an improved understanding of sedimentation and eutrophication problems in the tidal...

The distribution and abundance of phytoplankton in the fresh, tidal Potomac River, Md., was different during 1979-81 from that observed in the 1960's and 1970's. Concentrations of phytoplankton in the 1960's and 1970's reached maximum attainable levels that were limited only by self-shading. A sag in phytoplankton abundance, apparent during the summers of 1980 and 1981 between Rosier...

The direct and indirect effects of human activities, including environmental contamination, upon bird populations in San Francisco Bay and Chesapeake Bay are imperfectly understood, and few data are available. that allow a comparison of the contamination levels in birds from these two areas. Certain trace elements and organochlorine compounds have been found at sufficiently high...

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The U.S. Geological Survey is conducting a water quality study as part of the nationally implemented Rural Clean Water Program in the headwaters of the Conestoga River, Pennsylvania. The study, which began in 1982, was designed to determine the effect of agricultural best management practices on surface--and groundwater quality. The study was concentrated in four areas within the...

The Potomac River at Chain Bridge is the major riverine source of dissolved silica (DSi) to the tidal Potomac River and Estuary. DSi concentrations at Chain Bridge are positively correlated with river discharge; river discharge is an important factor controlling rates of supply, dilution, and residence time. When river flow is high, the longitudinal DSi distribution is conservative. When...