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Temporal Trends of Selected Agricultural Chemicals in Iowa's Groundwater, 1982-95: Are Things Getting Better?

Dana W. Kolpin, Debra Sneck-Fahrer, George R. Hallberg, and Robert D. Libra

FIGURES

Figure 1 | Figure 2 | Figure 3 | Figure 4 | Figure 5 | Figure 6

Figure 1. Location of the 1,1019 Iowa municipal wells used for this study.

Figure 2. Location of the 89 Iowa municipal wells having the longest record of agricultural-chemical data available for this study.

Figure 3. Statistical summary of the concentration differential for selected agricultural chemicals. This concentration differential was calculated by a subtraction of the median 1992-95 concentration from the median 1992 to 1995 concentration for the 89 wells having the longest record of agricultural-chemical data. If a particular well had no chemical data for the 1987-91 time period, the median 1982 to 1986 concentration was subtracted from the 1992 to 1995 concentration.

 Figure 4. Statistical summary of the concentration differential for selected agricultural chemicals by well depth. This concentration differential was calculated by a subtraction of the median 1987 to 1991 concentration from the median 1992 to 1995 concentration for the 89 wells having the longest record of agricultural-chemical data. If a particular well had no chemical data for the 1987 to 1991 time period, the median 1982 to 1986 concentration was subtracted from the 1992 to 1995 concentration.

Figure 5 Statistical summary of the concentration differential for selected agricultural chemicals by aquifer type. This concentration differential was calculated by a subtraction of the median 1987 to 1991 concentration from the median 1992 to 1995 concentration for the 89 wells having the longest record of agricultural-chemical data. If a particular well had no chemical data for the 1987 to 1991 time period, the median 1982 to 1986 concentration was subtracted from the 1992 to 1995 concentration.

Figure 6 Summation of alachlor + atrazine + cyanazine + metolachlor (SUM) for the 89 Iowa municipal wells having the longest record of agricultural-chemical data available for this temporal study.

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