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Kansas Geological Survey, Public Information Circular (PIC) 14
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Occurrence of Nitrate in Kansas Ground Water

Studies in Kansas show that many factors affect nitrate concentration in ground water. These include soil characteristics, land-use practices, depth to the water table, depth of the well, age and construction of the well, and the amount of irrigation. Generally, areas such as south-central Kansas, which have relatively permeable (sandy) soils, a shallow water table, shallow wells, and irrigated farming, are most susceptible to nitrate contamination.

Recent data compiled by the Kansas Geological Survey suggest that water in older (pre-1975) wells has higher concentrations of nitrate-N than newer wells. In 1975, regulations were adopted concerning water-well construction and abandonment by KDHE.

During the 1990's, Survey staff performed nitrate-N analyses on 36 irrigation wells that had been sampled in the 1970's. All wells are located in western or south-central Kansas. In the majority of the samples, nitrate-N concentrations increased from the 1970's to the 1990's, indicating that nitrate is moving from the surface to ground water (fig. 3). This may be a function both of long-term irrigated farming in the area and the age of the wells. (Wells built before 1975 generally have the annular space filled with gravel pack to near land surface, potentially allowing for near-surface water flow down the well-bore to ground water).

Figure 3--Comparison of nitrate-N concentrations in 36 irrigation wells sampled in the 1970's and in the 1990's. The 1:1 line shows where the values would plot if there were no change from the 1970's to the 1990's. Points above the line indicate an increase in nitrate-N concentrations; those below indicate a decrease. Box at 10 mg/L indicates U.S. EPA drinking-water limit.

Most samples show an increase in nitrate-N from 1970s to 1990s.

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Kansas Geological Survey, Public Outreach
1930 Constant Ave., Lawrence, KS 66047-3726
Phone: (785) 864-3965, Fax: (785) 864-5317
Web version July 1999