Madison, Wisconsin: Wisconsin Department of Natural Resources
Summary
Studies of the magnitude and variation of nitrate and nitrite concentrations in private well water were made in the central Wisconsin farm area of Marathon County, and 55% of the wells contained nitrate concentration of 45 mg/l or more. Among 242 wells investigated, 82 private wells were sampled 2 times/month for a period of 14 months. Nearly 70% of the 82 wells contained nitrate levels of 45 mg/l or greater at one time or another during the sampling period and about 45% of the wells contained nitrate levels of 45 mg/l or more throughout the period. The variations in nitrate concentration were closely related to amount of precipitation and concentration was highest during heavy rainy season and lowest during dry period for the majority of wells examined.