Publications

Measurements of δ(13C) determined on CO2 with an isotope-ratio mass spectrometer (IRMS) must be corrected for the amount of 17O in the CO2. For data consistency, this must be done using identical methods by different laboratories. This report aims at unifying data treatment for CO2 IRMS by proposing (i) a unified set of numerical values, and (ii) a unified correction algorithm, based on...

In 2007 an invasive dreissenid mussel species, Dreissena bugensis (quagga mussel), was discovered in Lake Mead reservoir (AZ–NV). Within 2 years, adult populations have spread throughout the lake and are not only colonizing hard substrates, but also establishing in soft sediments at depths ranging from 1 to >100 m. Dreissena bugensis size class and population density distribution differs...

A prolonged drought in the High Plains of Nebraska prompted the use of groundwater for cooling at the largest coal-fired power plant in the State. Prior to the drought, groundwater was used primarily for irrigation and the power plant relied exclusively on surface water stored in a nearby reservoir for cooling. Seepage from the reservoir system during the past ∼75 a has resulted in the...

Concentrations of weathering products in streams often show relatively little variation compared to changes in discharge, both at event and annual scales. In this study, several hypothesized mechanisms for this “chemostatic behavior” were evaluated, and the potential for those mechanisms to influence relations between climate, weathering fluxes, and CO2 consumption via mineral weathering...

The maps and graph in this summary describe streamflow conditions for water-year 2009 (October 1, 2008 to September 30, 2009) in the context of the 80-year period 1930-2009, unless otherwise noted. The illustrations are based on observed data from the U.S. Geological Survey's National Streamflow Information Program. The period 1930-2009 was used because prior to 1930, the number of...

The influence of environmental factors on biotic responses to nutrients was examined in three diverse agricultural regions of the United States. Seventy wadeable sites were selected along an agricultural land use gradient while minimizing natural variation within each region. Nutrients, habitat, algae, macroinvertebrates, and macrophyte cover were sampled during a single summer low-flow...

Alteration of natural flow regimes is generally acknowledged to have negative effects on native biota; however, methods for defining ecologically appropriate flow regimes in managed river systems are only beginning to be developed. Understanding how past and present water management has affected rivers is an important part of developing such tools. In this paper, we evaluate how existing

In order to investigate the interactions between turbulence and suspended sediment transport in natural aqueous environments, we ideally require a technique that allows simultaneous measurement of fluid velocity and sediment concentration for the whole flow field. Here, we report on development of a methodology using the water column acoustic backscatter signal from a multibeam echo...

An assessment of nitrate concentrations in groundwater in the United States indicates that concentrations are highest in shallow, oxic groundwater beneath areas with high N inputs. During 1991-2003, 5101 wells were sampled in 51 study areas throughout the U.S. as part of the U.S. Geological Survey National Water-Quality Assessment (NAWQA) program. The well networks reflect the existing...

Throughout American history water resources have played integral roles in shaping patterns of human settlement and networks of biological and economic exchange. In turn, humans have altered hydrologic systems to meet their needs. A paucity of climate and water discharge data for the seventeenth and eighteenth centuries, however, has left America's preindustrial hydrology largely...

The fluorescent properties of dissolved organic matter (DOM) are often studied in order to infer DOM characteristics in aquatic environments, including source, quantity, composition, and behavior. While a potentially powerful technique, a single widely implemented standard method for correcting and presenting fluorescence measurements is lacking, leading to difficulties when comparing...

An aerobiology sampling flight at 20 km was conducted on 28 April 2008 over the Pacific Ocean (36.5° N, 118–149° W), a period of time that coincided with the movement of Asian dust across the ocean. The aim of this study was to confirm the presence of viable bacteria and fungi within a transoceanic, atmospheric bridge and to improve the resolution of flight hardware processing techniques...