Effects of Urban Sprawl on the Water Resources of Northern U.S. Geological Survey, 1730 E. Parham Rd., Richmond, VA 23228 Karen C. Rice ([email protected])

Effect of Urbanization on Sediment Quality – Results of a Nationwide USGS Study Water Quality – Accotink Creek, Fairfax County USGS analyzed the concentrations of nine trace elements in 541 streambed sediment samples collected by the Ground Water – Loudoun County National Water-Quality Assessment (NAWQA) Program across the country from 1992 through 1996 (Rice, 1999). Accotink Creek, which flows through heavily developed areas in Fairfax County, The population of Loudoun County has increased by about 150% violates the Virginia standard for fecal coliform bacteria. in the past 20 years. This population growth is leading to increased Population density was positively related to the sum of concentrations of copper, mercury, lead and zinc. demands for water. Because surface-water supplies are limited, ground USGS is determining the dominant sources of fecal coliform bacteria in water from the fractured rocks of the Piedmont and Blue Ridge Median concentrations of cadmium, chromium, copper, mercury, lead, nickel, and zinc were significantly Accotink Creek using ribotyping. This technique uses genetic "fingerprints"–consisting of Physiographic Provinces will be expected to meet these demands. greater (p = 0.00) at urban sites compared to nonurban sites. the section of DNA coded for ribosomal RNA production that is unique to each warm-blooded animal species–to positively identify the bacteria sources in streamwater. In FY 2000, the USGS inventoried existing digital data and produced These trace elements are considered very toxic, are relatively accessible in the environment, and are on the preliminary maps of the depth of the bedrock and the altitude of the top USEPA's list of 126 Priority Pollutants. of the bedrock in Loudoun County. County officials will use this information Ribotyping Bacteria Sources in Accotink Creek in an assessment of the sustainability and vulnerability to contamination Water Source Samples Samples 30 of the region's ground-water resources. 25 0.9 250 Isolated Isolated 20 Urban sites Urban sites E. coli E. coli 15 0.8 Non-urban sites Non-urban sites ercent P 10 200 0.7 eight

5 eight

rRNA rRNA rRNA rRNA rRNA rRNA g/g 1,000 µ y w C B A Dog Human Goose 0 y w 0.6 k

bit 150 Cat Dog g/g dr Deer Duc g/g dr

0.5 µ Rab µ Goose Human Rodent Sea Gull Raccoon 0.4 100 ation, in ation, in 0.3 (Cu+Hg+Pb+Zn), in

Σ 100

0.2 Concentr

Concentr 50

0.1

0 0 Many pesticides were detected in water samples collected from Accotink Creek 1 10 100 1,000 Cd Hg Cr Cu Pb Ni Zn from 1992 to 1996 (Ator and others, 1998). These pesticides are used on rights-of-way, Population Density, in Number of People/km2 turf, golf courses, and as additives to asphalt and other building materials.

Pesticides detected in Accotink Creek Distribution of Wells in Loudoun Land Use, circa 1995 County, 1996 atrazine MCPA2 carbaryl metolachlor chlorpyrifos oryzalin2 diazinon1 prometon malathion1 simazine3 1 detected at the highest concentration measured USGS scientist making Streamflow Characteristics – Urban vs Forested in Northern Virginia in the Basin streamflow measurement in a Streamflow data collected by USGS show the effects of impervious areas related to urban development. 2detected at the highest concentration measured Harpers Potomac R. Northern Virginia Ferry nationwide * For all storms, the peak flow (per square mile) in Accotink Creek is higher than that of , which flows through 3 detected at the highest frequency and at the highest Winchester a largely wooded and undeveloped area south of the Quantico U.S. Marine Corps Reservation. concentrations in the basin, occasionally exceeding Frederick the maximum contaminant level of 4 µg/L Clarke Flow-duration curves for Accotink Creek divided into three periods–pre-development (1948-63), active development Leesburg (1964-80), and post-development (1981-98)–indicate that the lowest flows became lower and the highest flows became e Loudoun higher over time, i.e., the "flashiness" of the stream increased as a result of development (Rice, in preparation).

Water Quality – in Reston, Fairfax County Lake Anne Peak Flows Increase in Urban Streams Urbanization Alters Flow Characteristics This "real-estate lake" is located in a densely populated watershed, and the lake Washington, DC e 100 100 120 Warren

Reston Accotink Creek near Annandale 1948-63 shoreline is surrounded by dwellings. Lake outflow drains to the Potomac River. 2 2 100 1964-80 Accotink Creek near Annandale Fairfax Accotink Creek near Annandale 1981-98 ork Shenandoah R.

, in cfs/mi 80 USGS hydrologist Karen Rice compared concentrations of arsenic and copper 10 , in cfs/mi 10

Fairfax , in cfs Manassas 60 in samples of precipitation and streamwater collected from Bear Branch, North F Fauquier

Accotink Discharge a forested watershed on Catoctin Mountain, Md. (Church and others, 1998), 1 1 40 Creek ork Shenandoah R. 20 Instantaneous Discharge

to samples from the Lake Anne watershed (Rice, in preparation). Instantaneous Discharge Aquia Creek near Garrisonville Aquia Creek near Garrisonville

0.1 0.1 0 South F Prince 6/5/00 6/5/00 6/6/00 6/6/00 6/7/00 6/7/00 6/20/00 6/20/00 6/21/00 6/21/00 6/22/00 6/22/00 6/23/00 6/23/00 6/24/00 6/24/00 6/25/00 0 10 20 30 40 50 60 70 80 90 100 While precipitation loadings of arsenic at Lake Anne were similar to those William 0:00 12:00 0:00 12:00 0:00 12:00

0:00 12:00 0:00 12:00 0:00 12:00 0:00 12:00 0:00 12:00 0:00 at Bear Branch, loadings of copper were 1.5-fold higher at Lake Anne. Percent of Time Indicated Discharge was Equaled or Exceeded

e Fluxes of total arsenic were up to 5,800 times higher and fluxes of total copper Quantico References Aquia were up to 10,000 times higer in Lake Anne streams compared to Bear Branch. Creek Ator, S.W., Blomquist, J.D., Brakebill, J.W., Denis, J.M., Ferrari, M.J., Miller, C.V., and Zappia, Humbert, 1998, Water quality in t he Potomac River Basin, , , Virginia, , and the District of Columbia, 1992-96: The source of the copper in the Lake Anne watershed is primarily brake linings Stafford USGS Circular 1166, 38 p. on motor vehicles while much of the arsenic is leached from pressure-treated lumber used as building material. Church, T.M., Scudlark, J.R., Conko, K.M., Bricker, O.P., and Rice, K.C., 1998, Transmission of atmospherically deposited trace Fredericksburg elements through an undeveloped, forested Maryland watershed: Maryland Dept. of Natural Resources, Chesapeake Bay Research and Both arsenic and copper are on the list of 126 Priority Pollutants and are considered Monitoring Division, 87 p. very toxic and relatively accessible in the environment. Arsenic is classified as a carcinogen, and the USEPA's drinking water standard was recently lowered Rice, K.C., 1999, Trace-element concentrations in streambed sediment across the conterminous : Environmental Science and from 50 µg/L to 5 µg/L. Technology, vol. 33, no. 15, p. 2499-2504.

Rice, K.C., in preparation, Historical reconstruction of the deposition of lake sediments and associated arsenic and copper concentrations during land-use change from forested to suburban in a northern Virginia catchment: Ph.D. Dissertation, University of Virginia Department of Environmental Sciences.

Graphics, editing, and layout by Martha Erwin, Theodore Samsel, III, and R. Brent Banks, III; Computer support by Willet Wilson