HR: 1340h
AN: B43C-0297    [Abstracts]
TI: Effects of Urban Development on Water Quality in the Piedmont of North Carolina: Association of Landscape Variables With Water Quality
AU: * Harned, D A
EM: daharned@usgs.gov
AF: U.S. Geological Survey, 3916 Sunset Ridge Road, Raleigh, NC 27607 United States
AU: Cuffney, T F
EM: tcuffney@usgs.gov
AF: U.S. Geological Survey, 3916 Sunset Ridge Road, Raleigh, NC 27607 United States
AB: An assessment of effects of urban development on water quality in the Piedmont of North Carolina is part of the U.S. Geological Survey National Water-Quality Assessment (NAWQA) Program. Thirty sites along a gradient of undeveloped to fully urbanized basins were selected using geographic information analysis to control variability in natural factors that influence water quality. Data collected include nutrient, pesticide, ion, and dissolved-oxygen concentrations, temperature, pH, specific conductance, streamflow, stage, habitat characteristics, and algal, benthic invertebrate, and fish communities. Sampling for water chemistry ranged from two samples (at 20 sites) to six samples (at 10 sites) per year from October 2002 to September 2003. Geomorphic and biological data were collected once in each basin. An index that integrates information on human influences, including land cover, population, and socioeconomic characteristics was used to define the urban gradient and to select sites. Relations among landscape, streamflow, temperature, and water-chemistry variables were analyzed to define urban effects on water quality. Distinct patterns of association occurred between landscape variables and water quality. An increase in urban index is associated with increases in pH (r=0.60), specific conductance (0.72), sulfate (0.68), a multiple-constituent chemical index (0.91), and a pesticide index (0.76). Landscape characteristics correlated with water quality in a similar manner. Increasing basin population density is associated with higher pH (0.55, 1990; 0.56, 2000), specific conductance (0.71, 1990), chloride (0.66, 1990), sulfate (0.72), and pesticides (0.71, 1990; 0.68, 2000). This pattern also is reflected in household density (pH (0.60), chemical index (0.87), and pesticide index (0.68)); in the total percentage of developed land in the basin (specific conductance (0.85), chloride (0.77), sulfate (0.81), total nitrogen (0.50), chemical index (0.84), and pesticide index (0.74)); percentage of the basin in commercial, industrial, and transportation land uses (specific conductance (0.90), chloride (0.83), sulfate (0.81), chemical index (0.84), and pesticide index (0.74)); in high-intensity residential land use (pH (0.56), specific conductance (0.82), chloride (0.71), sulfate (0.78), nitrite plus nitrate (0.58), total nitrogen (0.62), chemical index (0.88), and pesticide index (0.74)); and in low-intensity residential land use (specific conductance (0.74), chloride (0.71), sulfate (0.70), and chemical index (0.80)). This pattern of association also occurred in the percentage of a 200-meter-wide riparian buffer in urban land cover (specific conductance (0.78), chloride (0.74), sulfate (0.78), pesticide index (0.86) and chemical index (0.86)) and in basin road density (pH (0.57), specific conductance (0.74), chloride (0.69), sulfate (0.72), pesticide index (0.73), and chemical index (0.89)). Instantaneous stream discharge decreased with increased urban index (-0.60), population density (-0.54, 1990; -0.53, 2000), household density (-0.52), developed land (-0.50), and road density (-0.53). Greater basin forested land cover was associated with decreased specific conductance (-0.78), chloride (-0.70), sulfate (-0.74), total nitrogen (-0.59), chemical index (-0.80), and pesticide index (-0.67). A delay in response of pH, sulfate, and chemical index is evident up to an urban index value of 30. A threshold at this index value corresponds to an impervious area of less than 5 percent and a population density below 250 people per square mile.
UR: http://nc.water.usgs.gov/albe/General/ulug/index.html
DE: 0478 Pollution: urban, regional and global (0345, 4251)
DE: 0493 Urban systems
DE: 0496 Water quality
DE: 1632 Land cover change
DE: 1834 Human impacts
SC: Biogeosciences [B]
MN: Fall Meeting 2005