Response of Stream Chemistry During Base Flow to Gradients of Urbanization in Selected Locations Across the Conterminous United States, 2002-04

Abstract

The U.S. Geological Survey (USGS) is committed to providing the Nation with credible scientific information that helps to enhance and protect the overall quality of life and that facilitates effective management of water, biological, energy, and mineral resources (http://www.usgs. gov/). Information on the Nation's water resources is critical to ensuring long-term availability of water that is safe for drinking and recreation and is suitable for industry, irrigation, and fish and wildlife. Population growth and increasing demands for water make the availability of that water, now measured in terms of quantity and quality, even more essential to the long-term sustainability of our communities and ecosystems.The USGS implemented the National Water-Quality Assessment (NAWQA) Program in 1991 to support national, regional, State, and local information needs and decisions related to water-quality management and policy (http://water.usgs.gov/nawqa). The NAWQA Program is designed to answer: What is the condition of our Nation's streams and ground water? How are conditions changing over time? How do natural features and human activities affect the quality of streams and ground water, and where are those effects most pronounced? By combining information on water chemistry, physical characteristics, stream habitat, and aquatic life, the NAWQA Program aims to provide science-based insights for current and emerging water issues and priorities. From 1991-2001, the NAWQA Program completed interdisciplinary assessments and established a baseline understanding of water-quality conditions in 51 of the Nation's river basins and aquifers, referred to as Study Units (http://water.usgs.gov/nawqa/studyu.html).Multiple national and regional assessments are ongoing in the second decade (2001)(2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012) of the NAWQA Program as 42 of the 51 Study Units are reassessed. These assessments extend the findings in the Study Units by determining status and trends at sites that have been consistently monitored for more than a decade, and filling critical gaps in characterizing the quality of surface water and ground water. For example, increased emphasis has been placed on assessing the quality of source water and finished water associated with many of the Nation's largest community water systems. During the second decade, NAWQA is addressing five national priority topics that build an understanding of how natural features and human activities affect water quality, and establish links between sources of contaminants, the transport of those contaminants through the hydrologic system, and the potential effects of contaminants on humans and aquatic ecosystems. Included are topics on the fate of agricultural chemicals, effects of urbanization on stream ecosystems, bioaccumulation of mercury in stream ecosystems, effects of nutrient enrichment on aquatic ecosystems, and transport of contaminants to public-supply wells. These topical studies are conducted in those Study Units most affected by these...

Comparison of pesticide concentrations in streams at low flow in six metropolitan areas of the United States

“…4 and 5 have the same legend, but the y axis scales vary.) Similar figures for high base flow and for the other study areas are provided in Sprague et al [13].…”

“…1E), total herbicide concentrations did not follow a clear pattern relative to urban land cover (Fig. 2E) or to any nonurban land cover types or landscape variables at either high or low base flow (data not shown, see Sprague et al [13]), indicating that herbicide concentrations in the Denver basins are influenced by factor(s) not measured in the present study. One possibility may be the extensive water management that occurs in the greater Denver metropolitan area, where a complex network of canals and pipes moves water between different areas for domestic water supply, agricultural irrigation, and power generation [21].…”

“…Water samples were collected using depth‐ and width‐integrating techniques and were processed and preserved onsite using standard methods described by the USGS [12] (http://www.pubs.water.usgs.gov/twri9A). Samples were filtered through a 0.7‐μm pore diameter glass‐fiber filter in the field to remove suspended particulate matter, and analyzed for 61 pesticide compounds (39 pesticides and 22 degradates [13]) at the USGS National Water‐Quality Laboratory in Denver (CO, USA). Compounds were extracted from water samples using C‐18 solid‐phase extraction columns, then were identified and quantified using capillary‐column gas chromatography–mass spectrometry and selected‐ion monitoring [14].…”

“…The derivation and application of benchmarks, which are based on a combination of U.S. EPA ambient water‐quality criteria [20] (http://www.epa.gov/waterscience/criteria/nrwqc-2006.pdf) and aquatic toxicity data from U.S. EPA pesticide risk assessments, are described in Gilliom et al [2]. One or more aquatic‐life benchmarks are available for 34 of the 61 pesticide compounds (32 pesticides and two degradates) analyzed (see Sprague et al [13] for pesticide benchmark values used in the present study). Acute benchmarks were designed for comparison to instantaneous (maximum) contaminant concentrations, and chronic benchmarks for comparison to mean concentrations over a specific (4–60 d) averaging period [2].…”

Periphyton biomass and ecological stoichiometry in streams within an urban to rural land-use gradient

“…In our study, urban streams were more nutrient-rich, had higher pH, greater concentrations of dissolved cations, and greater conductivity. The range of conductivities and nutrient concentrations equal or exceed that observed along other urban-rural land-use gradients in the U.S. (Walker & Pan, 2006;Sprague et al, 2007;Ponader et al, 2008). All of the significant trends in water chemistry along the urban-rural gradient increased from rural to urban areas (Table 1; Figs.…”