Projects

Analysis of Nitrate in Groundwater in Jackson County, Indiana

Overview by Edwin Hartke and Denver Harper
Updated December 2003

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Ground-water quality in the major glacial-outwash aquifer system that occupies the floodplain of the East Fork of the White River, northwest of Seymour in Jackson County, Indiana, has been seriously degraded by anthropogenic nitrate. Most of the shallow (less than 25 feet deep) domestic drinking-water wells produce water with nitrate concentrations that approach or exceed the Drinking Water Standard limits of 10mg/l N, established by the U.S. EPA.

Aerial photograph of the study area, showing a large confined feedlot and the distribution of water wells. The northwestern part of Seymour, Indiana, is also visible.

The aquifer extends for many miles up and downstream; however, the study area was limited to a 15 square mile section that lies northwest of the river. The aquifer is between 30 and 60 feet thick in the study area, where it consists of sand and some fine gravel overlain by 6 to 12 feet of overbank (alluvial) material (fine sand and silt with some clay). The aquifer lies on lake clay and shale.

Installation of a monitoring well at the study site.

The purpose of the project was to identify the sources of nitrogen. Three techniques were employed to identify possible sources of nitrate contamination: (1) an assessment of the hydrogeologic setting, (2) identification of nitrogen inputs related to land-use activities, and (3) analyses of water chemistry and of nitrogen isotopes (del15N/del14N).

Data loggers were installed that continuously monitored rainfall and water elevations in monitoring wells. Water samples were periodically collected for chemical analyses from the monitoring wells and six domestic wells.

The sources of nitrate in the shallow ground water were indicated by spatial variations in nitrate concentrations and isotopic results and their relationships to farm fields receiving fertilizers and to animal-waste sites. Samples collected from wells installed in farm fields indicated inorganic fertilizers or mixed inorganic and animal-waste sources, whereas wells adjacent to and down-gradient from animal feeding operations indicated animal-waste sources.

The results of the project also indicated that denitrification occurs in the aquifer as the vertical component of the ground-water flow system carries the nitrate downward. This indicates that, with the implementation of best management practices (BMPs), naturally occurring denitrification and recharge from precipitation make this aquifer a candidate for remediation.

For a more detailed technical report on the investigation, go to the Jackson Nitrate Project Web page.

The project was sponsored by the Indiana Department of Environmental Management (IDEM). The term of the project was from September 1, 1999 to June 30, 2002.

In October, 2003, an entirely new project commenced within part of the study area. The project is titled "Agricultural BMP Application to Remediate Nitrate Contamination in a Major Outwash Aquifer in Jackson County, Indiana." The project will involve a cooperative effort of the IGS, farmers, and other agencies to implement and evaluate best management practices (BMPs) for fertilizer application and to determine their efficacy in minimizing the entry of nitrate into the aquifer. Demonstration plots will be established, and new monitoring wells will be installed to collect samples of water that leaches from these plots to the aquifer. Changes in nitrate concentrations through time will indicate if the experimental procedures are effective.

For additional information regarding these projects, you should contact Denver Harper (e-mail: dharper@indiana.edu) or Ed Hartke (e-mail: ehartke@indiana.edu) at the Indiana Geological Survey, 611 N. Walnut Grove, Bloomington, IN 47405.