WRIR 96-4083

You can DOWNLOAD THIS REPORT (1,220 KB) in Portable Document Format (PDF)
The Adobe PDF Reader program is available for free from Adobe.

Crandall, C.A., 1996, Shallow Ground-Water Quality in Selected Agricultural Areas of South-Central Georgia, 1994: Water-Resources Investigations Report 96-4083, 23 p.


The Georgia-Florida Coastal Plain National Water-Quality Assessment Program began an agricultural land-use study in March 1994. The study area is located in the upper Suwannee River basin in Tift, Turner, Worth, Irwin, Wilcox, and Crisp Counties, Ga. Twenty-three shallow monitoring wells were installed in a 1,335-square-mile area characterized by intensive row-crop agriculture (peanuts, corn, cotton, and soybeans). The study focused on recently recharged shallow ground water in surficial aquifers to assess the relation between land-use activities and ground-water quality. All wells were sampled in March and April (spring) 1994, and 14 of these wells were resampled in August (summer) 1994.

Shallow ground water in the study area is characterized by oxic and acidic conditions, low bicarbonate, and low dissolved-solids concentrations. The median pH of shallow ground water was 4.7 and the median bicarbonate concentration was 1.7 mg/L (milligrams per liter). Dissolved oxygen concentrations ranged from 3.0 to 8.0 mg/L. The median dissolved-solids concentration in samples collected in the spring was 86 mg/L. Major inorganic ion composition was generally mixed with no dominant cation; nitrate was the dominant anion (greater than 60 percent of the anion composition) in 14 of 23 samples. Only concentrations of bicarbonate, dissolved organic carbon, and nitrate had significant differences in concentrations between samples collected in the spring and the background samples. However, median concentrations of some of the major ingredients in fertilizer (including magnesium, chloride, nitrate, iron, and manganese) were higher in water samples from agricultural wells than in background samples. The median concentration of dissolved solids in ground-water samples collected in the spring (86 mg/L) was more than double the median concentration (41 mg/L) of the background samples.

The median nitrate as nitrogen concentration of 6.7 mg/L in the spring samples reflects the effects of agricultural activities on ground-water quality. Samples from 30 percent of the wells exceeded the maximum contaminant level (MCL) for nitrate in drinking water (10 mg/L as N). Nitrogen isotope ratios ranged from 2.4 to 9.0 parts per thousand and indicate that most nitrogen in shallow ground water is probably from inorganic fertilizer. In addition, nitrate concentrations were positively correlated (p-values all less than 0.01) with concentrations of some of the major ingredients in fertilizer, such as potassium,



Purpose and Scope
Description of the Study Area
Land Use and Agricultural Practices Methods
Ground-Water Quality
Major Inorganic Constituents
Nitrogen and Phosphorus
Ammonia, Organic Nitrogen, Phosphorus, and Orthophosphate
Organic Compounds
Radon and Uranium
Effects of Fertilizer Application on Water Quality
Summary and Conclusions
References Cited
Appendix: A. Volatile Organic Compounds Analyzed for Ground-Water Samples for the Study-Unit Survey; and B. Pesticides Analyzed in Ground-Water Samples by the U.S. Geological Survey

[an error occurred while processing this directive]