A COMMUNITY-BASED SAMPLING PROGRAM FOR EVALUATING 
LONG-TERM FLOOD IMPACTS ON RURAL WELL-WATER QUALITY

Illinois State Water Survey
 

Abstract 

A two-year educational and cost-effective program for assessing the long-term effects of the 1993 flood and other more recent flooding events on nitrate and coliform bacteria contamination in rural domestic wells has been completed. Following the methodology used by Karny (1996), the Illinois State Water Survey (ISWS), in cooperation with five Future Farmers of America (FFA) chapters along the Mississippi and Illinois Rivers, provided free, confidential well-water testing for nitrate and coliform bacteria to rural well owners in their school districts. Three schools—North Greene, Unity-Mendon, and Payson-Seymour—participated in two sampling events in their school districts that resulted in 110, 151, and 193 samples being submitted for analysis, respectively. Two schools—Valmeyer and Calhoun Community—participated in three sampling events that resulted in 128 and 226 samples being submitted for analysis. The total number of samples for all five schools was 808. 

Each well owner completed a questionnaire that provided information about farming practices and site factors that might influence well-water quality. Overall, 5.0% of the samples had nitrate levels above 10 mg/l as N, 49.4% of the samples had coliform bacteria, and 15.2% of the samples tested positive for E. coli. When comparing individual factors that might affect well-water quality, such as well type, well depth, and farming practices, nitrate results were mixed, with some indication that a particular factor may indicate an increased vulnerability to nitrate contamination. A higher percentage of samples collected in the spring versus samples collected in the fall had nitrate values over 3 mg/l and 10 mg/l. The same was true for samples collected at active farms versus those from rural residences. Samples from wells where pesticides were mixed with the well water also show some influence on nitrate levels. For coliform bacteria, several factors seem to have had a direct influence on the percentage of wells contaminated. Sampling results show that school district (regional geology), well depth, well type, and well treatment (filtering or softening) influenced the percentage of wells contaminated. Dug wells and shallow wells were much more contaminated with coliform bacteria than were drilled wells and deep wells.