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Ohio Water Science Center

Evaluation of Nitrate Concentrations and Sources in the Elk Creek Watershed, Southwestern Ohio, 2003-2004

U.S. Geological Survey, Scientific Investigations Report 20065223

By Thomas L. Schumann and Bruce A. Pletsch1

In cooperation with the Miami Conservancy District

1Miami Conservancy District

This report is available as a 30-page PDF for viewing and printing.


Nitrate concentrations exceeding the U.S. Environmental Protection Agency maximum contaminant level of 10 milligrams per liter have been reported in ground water near the City of Trenton, Ohio, in the southern part of the Elk Creek watershed. A study of nitrate concentrations and sources in surface and ground water within the Elk Creek watershed was conducted during 2003 and 2004.

Nitrate concentrations in the Elk Creek watershed range from less than 0.06 to 11 milligrams per liter. The likely sources of elevated nitrate in the ground water near the City of Trenton appear to be soil organic matter and ammonia fertilizer. Land use is predominantly (93 percent) agricultural, with no identified point sources of nitrate. Likely sources of nitrate in the surface water appear to be manure and septic system effluent, soil organic matter, and ammonia fertilizer.

Water-quality constituents, including nitrate, were sampled in water from 38 wells and at 6 surface-water sites. The wells were all shallow (less than 105 feet deep), with open intervals in aquifers of glacial origin, that include tills, outwash, and alluvium. Nitrate concentrations (median of 0.06 milligrams per liter) in the ground water of the upper section of the watershed were lower than those in the lower section of the watershed (median of 4.2 milligrams per liter).

Nitrate was analyzed for nitrogen and oxygen isotope values. The d15N and d18O range from -22.36 to +32.29 per mil, and -6.27 to +17.72 per mil, respectively. A positive correlation of d15N and d18O enrichment indicates that denitrification is a prevalent process within the watershed.




Study Approach

Purpose and Scope

Geographic and Hydrogeologic Setting of the Study Area

Study Methods

Site Selection

Collection and Analysis of Water-Quality Data

Quality Assurance/Quality Control for Water-Quality Measurements

Chemical and Physical Characteristics of Ground Water and Surface Water

Evaluation of Nitrate Concentrations and Sources in the Elk Creek Watershed



References Cited


1.-6. Maps showing:

1. Location of the Elk Creek watershed (study area), southwestern Ohio.

2. Ground-water and surface-water sampling locations in the Elk Creek watershed.

3. Surficial deposits.

4. Land use, 1994.

5. Potentiometric surface of water in surficial deposits.

6. Nitrate concentrations in ground and surface water.

7. Graph showing nitrogen and oxygen isotope ratios of nitrate in ground water and surface water.

8. Trilinear diagram showing percentages of major ions in ground-water samples from unconsolidated deposits from four wells.


1. Water-quality characteristics of water samples collected from sites in the Elk Creek watershed, southwestern Ohio, September 2003 through October 2004.

2. Physical characteristics of wells sampled.

3. Streamflow measurements at surface-water sites.


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Whole report (3.66 MB) - 30 pages (8.5" by 11" paper)

Suggested Citation:

Schumann, T.L., and Pletsch, B.A., 2006, Evaluation of nitrate concentrations and sources in the Elk Creek watershed, southwestern Ohio, 2003-2004: U.S. Geological Survey Scientific Investigations Report 2006-5223, 30 p.

For more information about USGS activities in Ohio, visit the USGS Ohio Water Science Center home page.

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