REFERENCES

Akers, K.K.B, Schnoebelen, D.J., Savoca, M.E., Roberts, L.R., and Becher, K.D., 1999, Water-quality assessment of the Eastern Iowa Basins—Hydrologic and biologic data, September 1995 through September 1996: U.S. Geological Survey Open-File Report 99–66, 154 p.

Akers, K.K.B, Montgomery, D.L., Christiansen, D.E., Savoca, M.E., Schnoebelen, D.J., Becher, K.D., and Sadorf, E.M., 2000, Water-quality assessment of the Eastern Iowa Basins—Hydrologic and biologic data, October 1996 through September 1998: U.S. Geological Survey Open-File Report 00–67, 300 p.

Alexander, R.B., Smith, R.A., and Schwarz, G.E., 2000, Effect of stream channel size on the delivery of nitrogen to the Gulf of Mexico: Nature, v. 403, p. 758–761.

Becher, K.D., Schnoebelen, D.J., and Akers, K.K.B., 2000, Nutrient concentrations and yields in surface water in Eastern Iowa: Journal of the American Water Resources Association, v. 36, no. 1, p. 161–173.

Brigham, A.R., and Sadorf, E.M., 2001, Benthic invertebrate assemblages and their relation to physical and chemical characteristics of streams in the Eastern Iowa Basins, 1996–1998: U.S. Geological Survey Water-Resources Investigations Report 00–4256.

Bruce, B.W., and McMahon, P.B., 1996, Shallow ground-water quality beneath a major urban center—Denver, Colorado, USA: Journal of Hydrology, v. 186, p. 129–151.

Cambardella, C.A., Moorman, T.B., Jaynes, D.B., Hatfield, J.L., Parkin, T.B., Simpkins, W.W., and Karlen, D.L., 1999, Water quality in Walnut Creek watershed— Nitrate-nitrogen in soils, subsurface drainage water, and shallow groundwater: Journal of Environmental Quality, v. 28, p. 25–34.

Gilliom, R.J., Alley, W.M., and Gurtz, M.E., 1995, Design of the National Water-Quality Assessment Program—Occurrence and distribution of water-quality conditions: U.S. Geological Survey Circular 1112, 33 p.

Goolsby, D.A., Battaglin, W.A., Lawrence, G.B., Artz, R.S., Aulenbach, B.T., Hooper, R.P., Keeney, D.R., and Stensland, G.J., 1999, Flux and sources of nutrients in the Mississippi—Atchafalaya River Basin Topic 3 Report for the Integrated Assessment on Hypoxia in the Gulf of Mexico: National Oceanic and Atmospheric Administration Decision Analysis Series No. 17, 130 p.

Heydens, W.F., Wilson, A.G., Kraus, L.J., Hopkins, W.E., and Hotz, K.J., 2000, Ethane sulfonate metabolite of alachlor—Assessment of oncogenic potential based on metabolic and mechanistic considerations: Toxicological Sciences, v. 55, p. 36–43.

Hilsenhoff, W.L., 1987, An improved index of organic stream pollution: The Great Lakes Entomologist, v. 20, no. 1, p. 31–39.

Hoyer, B.E., and Hallberg, G.R., 1991, Groundwater vulnerability regions of Iowa: Iowa Department of Natural Resources, Geological Survey Bureau Special Map Series II, 1 sheet.

Iowa Department of Natural Resources, 1999, Animal waste control facilities with operating permits in Iowa, digital data, accessed August 1999 at URL http://www.igsb.uiowa.edu/nrgis/gishome.htm

_____2000a, Final approved Iowa 1998 303(d) list: accessed September 2000 at URL http://www.state.ia.us/epd/wtresrce/303dnotc.htm

_____2000b, Methyl tertiary-butyl ether (MTBE) occurrence in Iowa: Iowa Department of Natural Resources Report for the 2000 Session of the Seventy-Eighth General Assembly, 29 p. accessed June 2000 at URL http://www.state.ia.us/ government/dnr/organiza/epd/ust/gwprof/021500.htm.

Kalkhoff, S.J., Kolpin, D.W., and Thurman, E.M., 1998, Degradation of chloroacetanilide herbicides—The prevalence of sulfonic and oxanilic acid metabolites in Iowa ground and surface waters: Environmental Science and Technology, v. 32, no. 11, p. 1738–1740.

Kalkhoff, S.J., and Van Metre, P.C., 1997, Organochlorine compounds in a sediment core from the Coralville Reservoir, Iowa: U.S. Geological Survey Fact Sheet 129–97, 4 p.

Kolpin, D.W., Kalkhoff, S.J., Goolsby, D.A., Sneck-Fahrer, D.A., and Thurman, E.M., 1997, Occurrence of selected herbicides and herbicide degradation products in Iowa’s ground water, 1995: Ground Water, v. 35, no. 4, p. 679–688.

Melnick, R.L., and others, 1997, Interagency assessment of oxygenated fuels, Chap. 4, Potential health effects of oxygenated gasoline: Washington, D.C., Office of Science and Technology Policy, p. 4–1—4–38.

Olcott, P.G., 1992, Ground water atlas of the United States— Segment 9, Iowa, Michigan, Minnesota, Wisconsin: U.S. Geological Survey Hydrologic Investigations Atlas 730–J, 31 p.

Omernik, J.A., 2000, Draft aggregations of level III eco-regions for the National Nutrient Strategy: accessed September 2000 at URL http://www.epa.gov/ost/standards/ecomap.html.

Osborne, L.L., and Kovacic, D.A., 1993, Riparian vegetated buffer strips in water-quality restoration and stream management: Freshwater Biology, v. 29, p. 243–258.

Porter, S.D., Harris, M.A., and Kalkhoff, S.J., 2001, Influence of natural factors on the quality of midwestern streams and rivers: U.S. Geological Survey Water-Resources Investigations Report 00–4288.

Porter, S.D., 2000, Upper Midwest river systems—Algal and nutrient conditions in streams and rivers in the upper Midwest region during seasonal low-flow conditions, in Nutrient criteria technical guidance manual, rivers and streams: Washington, D.C., U.S. Environmental Protection Agency, Office of Water, Office of Science and Technology, EPA–822–B–00–002, p. A–25—A–42.

Prior, J.C., 1991, Landforms of Iowa: Iowa City, University of Iowa Press, p. 30–75.

Rabalais, N.N., 1996, Nutrient changes in the Mississippi River and system responses on the adjacent continental shelf: Estuaries, v. 19, p. 386–407.

Roberts, L.R., 1997, Occurrence of selected organochlorine compounds in fish tissue from eastern Iowa streams, 1995: U.S. Geological Survey Fact Sheet 027–97, 4 p.

Sadorf, E.M. Linhart, S.M., and Savoca, M.E., 2000, Water quality of alluvial aquifers in eastern Iowa and southern Minnesota, 1998: U.S. Geological Survey Water-Resources Investigations Report 00–4106, 46 p.

Sands, J.K., and Holden, H.R., 1996, Iowa agricultural statistics: Des Moines, Iowa, U.S. Department of Agriculture and Iowa State University Extension, 97 p.

Savoca, M.E., Tobias, J.L., Sadorf, E.M., and Birkenholtz, T.L., 1997, Herbicides and nitrates in the Iowa River alluvial aquifer prior to changing land use, Iowa County, Iowa, 1996: U.S. Geological Survey Fact Sheet 085–97, 4 p.

Savoca, M.E., Sadorf, E.M., Akers, K.K., 1999, Ground-water quality in the eastern part of the Silurian-Devonian and Upper Carbonate aquifers in the Eastern Iowa Basins, Iowa and Minnesota, 1996: U.S. Geological Survey Water-Resources Investigations Report 98–4224, 31 p.

Savoca, M.E., Sadorf, E.M., Linhart, S.M., and Akers, K.K.B., 2000, Effects of land use and hydrogeology on the water quality of alluvial aquifers in eastern Iowa and southern Minnesota, 1997: U.S. Geological Survey Water-Resources Investigations Report 99–4246, 38 p.

Schnoebelen, D.J., Becher, K.D., Bobier, M.W., and Wilton, T., 1999, Selected nutrients and pesticides in streams of the Eastern Iowa Basins, 1970–95: U.S. Geological Survey Water-Resources Investigations Report 99–4028, 65 p.

Schwarz, G.E., and Alexander, R.B., 1995, State soil geographic (STATSGO) data base for the conterminous United States: U.S. Geological Survey Open-File Report 95–489.

Soenksen, P.J., 1996, Transport of agricultural chemicals in surface flow, tileflow, and streamflow of the Walnut Creek watershed near Ames, Iowa, April 1991– September 1993: U.S. Geological Survey Water-Resources Investigations Report 96–4017, 41 p.

Sorenson, S.K., Porter, S.D., Akers, K.K.B., Harris, M.A., Kalkhoff, S.J., Lee, K.E., Roberts, L.R., and Terrio, P.J., 1999, Water quality and habitat conditions in upper Midwest streams relative to riparian vegetation and soil characteristics, August 1997—Study design, methods, and data: U.S. Geological Survey Open-File Report 99–202, 53 p.

Squillace, P.J., Moran, M.J., Lapham, W.W., Price, C.V., Clawges, R.M., and Zogorski, J.S., 1999, Volatile organic compounds in untreated ambient groundwater of the United States, 1985–1995: Environmental Science and Technology, v. 33, no. 23, p. 4176–4187.

Stamper, D.M., and Tuovinen, O.H., 1998, Biodegradation of the acetanilide herbicides alachlor, metolachlor, and propachlor: Critical Reviews in microbiology, v. 24, no. 1, p. 1–22.

Stauffer, J.C., Goldstein, R.M., and Newman, R.M., 2000, Relationship of wooded riparian zones and runoff potential to fish community composition in agricultural streams: Canadian Journal of Fisheries and Aquatic Sciences, v. 57, p. 307–316.

Stoltenberg, D., and Pope, R., 1990, Atrazine management rules for Iowa: Iowa State University Extension Pamphlet Pm–1390, 2 p.

Sullivan, D.J., 2000, Fish communities and their relation to environmental factors in the Eastern Iowa Basins in Iowa and Minnesota, 1995–96: U.S. Geological Survey Water-Resources Investigations Report 00–4195, 20 p.

U.S. Department of Agriculture, 1999, Agricultural chemical usage, 1998 field crops summary: National Agricultural Statistics Service and Economic Research Service accessed August 1999 at URL http://usda.mannlib. cornell.edu/reports/nassr/other/pcu-bb

U.S. Environmental Protection Agency, 1986, Quality criteria for water 1986: Washington, D.C., report 440/5–86–001, 453 p.

_____1994, Acetochlor registration agreement and addendums, accessed August, 2000 at URL http://www.epa.gov/oppefed1/aceto/regagree.htm

_____1996, Drinking water regulations and health advisories: Washington D.C., Report 822–R–96–001, 16 p.

_____2000, Chlorpyrifos revised risk assessment and agreement with registrants: U.S. Environmental Protection Agency Factsheet, Prevention, pesticides and toxic substances (7506C), 4 p., accessed September 2000 at URL http://www.epa.gov/pesticides/ announcement6800.htm

Vannote, R.L., Minshall.G.W., Cummins, K.W., Sedell, J.R., and Cushing, C.E., 1980, The river continuum concept: Canadian Journal of Fisheries and Aquatic Sciences, v. 37, p. 130–137.

Zogorski and others, 1997, Interagency assessment of oxygenated fuels, chap. 2, Fuel oxygenates and water quality: Washington D.C., Office of Science and Technology Policy, p. 2–1—2–80.