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Occurrence and Transport of Agricultural Chemicals in Leary Weber Ditch Basin, Hancock County, Indiana, 2003–04

U.S. Geological Survey, Scientific Investigations Report 2006-5251

By Nancy T. Baker, Wesley W. Stone, John T. Wilson, and Michael T. Meyer

National Water-Quality Assessment Program

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Abstract

Leary Weber Ditch Basin, Hancock County, Indiana, is one of seven first-order basins selected from across the United States as part of the Agricultural Chemicals: Source, Transport, and Fate study conducted by the National Water-Quality Assessment Program of the U.S. Geological Survey. The nationwide study was designed to increase the understanding of the links between the sources of water and agricultural chemicals (nutrients and pesticides) and the transport and fate of these chemicals through the environment.

Agricultural chemicals were detected in Leary Weber Ditch and in every associated hydrologic compartment sampled during 2003 and 2004. Pesticides were detected more frequently in samples collected from overland flow and from the ditch itself and less frequently in ground-water samples. The lowest concentrations of pesticides and nutrients were detected in samples of rain, soil water, and ground water. The highest concentrations of pesticides and nutrients were detected in samples of tile-drain water, overland flow, and water from Leary Weber Ditch. Samples collected from the tile drain, overland flow and Leary Weber Ditch soon after chemical applications to the fields and coincident with rainfall and increased streamflow had higher concentrations of pesticides and nutrients than samples collected a longer time after the chemicals were applied.

A mass-balance mixing analysis based on potassium concentrations indicated that tile drains are the primary contributor of water to Leary Weber Ditch, but overland flow is also an important contributor during periods of high-intensity rainfall. When maximum rainfall intensity was 0.5 inches per hour or lower, overland flow contributed about 10 percent and tile drains contributed about 90 percent of the flow to Leary Weber Ditch. When maximum rainfall intensity was 0.75 inches per hour or greater, overland flow contributed about 40 percent and tile drains contributed about 60 percent of the flow to the ditch. Ground-water flow to Leary Weber Ditch was negligible.

Tile drains are an important agricultural-chemical transport path to Leary Weber Ditch, based on the hydrologic contributions of overland flow and tile drains to the ditch. Overland flow is also an important agricultural-chemical transport pathway during high-intensity rainfall; however, storms with high-intensity rainfall are sporadic throughout the year. Tile drains and the soil water moving to the tile drains are the primary transport pathway for agricultural-chemical transport to Leary Weber Ditch during most storms as well as between storms.

Contents

Foreword

Abstract

Introduction

Purpose and Scope

Description of Basin and Sampling Sites

Methods of Investigation

Field Methods

Laboratory Analyses, Data Presentation, and Quality-Control Assurance

Data Analysis

Occurrence of Agricultural Chemicals in Leary Weber Ditch Basin

Rain

Soil Water

Ground Water

Tile-Drain Water

Overland-Flow Water

Leary Weber Ditch

Transport of Agricultural Chemicals in Leary Weber Ditch Basin

Mixing Analysis

Uncertainty in Results of Mixing Analysis

Summary

Acknowledgments

References Cited

Figures

1-2. Maps showing:

  1. Location of Leary Weber Ditch Basin, Indiana, and sampling sites within the basin.
  2. Approximate tile-drain locations in Leary Weber Ditch Basin, Indiana.
3. Graphs showing storms targeted for water-quality sampling in Leary Weber Ditch and in the hydrologic compartments of Leary Weber Ditch Basin, Indiana in relation to: (A) streamflow at U.S. Geological Survey streamflow-gaging station Leary Weber Ditch at Mohawk, IN (03361638), (B) agricultural-chemical group sample-collection times for each hydrologic compartment, and (C) water levels in a well screened in the soil horizon at the North site with sample-collection times in the soil-water and ground-water hydrologic compartments.
4. Diagram showing depths of the screened intervals of wells used to sample soil water and ground water with relative distribution of particle sizes in soil cores sampled at the North and South sites in Leary Weber Ditch Basin, Indiana.
5. Example standard schematic boxplot showing central tendency and variability of water-quality concentrations.
6. Diagrams showing quality-control results for field-blank samples for pesticides, nutrients, and major ions collected in Leary Weber Basin, Indiana, 2003-04.
7. Graphs showing quality-control results for equipment-replicate samples for (A) pesticides, (B) nutrients, and (C) major ions collected in Leary Weber Ditch Basin, Indiana, 2003–04.
8. Boxplot showing distribution of potassium concentrations at selected ranges of flow duration and streamflow for U.S. Geological Survey streamflow-gaging station at Mohawk, IN (03361638).
9. Graph showing frequency of detection of selected pesticide parent (in bold) and pesticide degradate compounds for Leary Weber Ditch and for each hydrologic compartment sampled in Leary Weber Ditch Basin, Indiana, 2003-04.
10. Boxplots showing distribution of concentrations of selected pesticide parent and pesticide degradate compounds in Leary Weber Ditch and in eachhydrologic compartment sampled in Leary Weber Ditch Basin, Indiana, 2003–04.
11. Graphs showing relation of selected pesticide concentrations to streamflow for the hydrologic compartments sampled in Leary Weber Ditch Basin, Indiana, 2003–04.
12. Boxplots showing distribution of nutrient concentrations in Leary Weber Ditch and in each hydrologic compartment sampled in Leary Weber Ditch Basin, Indiana, 2003–04.

13.–14. Graphs showing:

  13. Concentration of selected pesticide parent and pesticide degradate compounds in lysimeter and well samples collected in the soil-water and ground-water hydrologic compartments in Leary Weber Ditch Basin, Indiana, 2004.
  14. Concentrations of nitrate plus nitrite (N) in lysimeter and well samples collected in the soil-water and ground-water hydrologic compartments in Leary Weber Ditch Basin, Indiana, 2004.
15. Diagram showing comparison of relative percentages of major ions in (A) soil water and ground water and (B) tile-drain, overland-flow, and Leary Weber Ditch water in Leary Weber Ditch Basin, Indiana, 2003–04.

16.–18. Graphs showing:

  16. Relation of selected nutrient concentrations to streamflow for the hydrologic compartments sampled in the Leary Weber Ditch Basin, Indiana, 2003–04.
  17. Comparison of alachlor concentrations measured in rain and overland-flow water during storm 5 in Leary Weber Ditch Basin, Indiana, 2004.
  18. Storm hydrographs for U.S. Geological Survey streamflow-gaging station at Mohawk, IN (03361638), showing estimated relative contribution of overland flow and tile-drain flow to Leary Weber Ditch and maximum 1-hour rainfall intensity for selected storms, 2003–04.

Tables

  1. Pesticide parent compounds and pesticide degradates analyzed for in water samples from Leary Weber Ditch Basin, Indiana, 2003–04.
  2. Frequency of detection for selected pesticide parent compounds and pesticide degradates for Leary Weber Ditch and each hydrologic compartment sampled in Leary Weber Ditch Basin, Indiana, 2003–04.
  3. Comparison of rain volume for Leary Weber Ditch Basin and streamflow at U.S. Geological Survey streamflow-gaging station at Mohawk, IN (03361638) for selected storms, 2003–04.
  4. Estimates of overland flow contributions to Leary Weber Ditch, Indiana, for selected storms, 2003–04.

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Whole report (5.9 MB) - 44 pages (8.5" by 11" paper)

Suggested Citation:

Baker, N.T., Stone, W.W., Wilson, J.T., and Meyer, M.T., 2006, Occurrence and Transport of Agricultural Chemicals in Leary Weber Ditch Basin, Hancock County, Indiana, 2003–04: U.S. Geological Survey Scientific Investigations Report 2006-5251, 44 p.


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