Occurrence and Transport of Agricultural 

Chemicals in Leary Weber Ditch Basin, 

Hancock County, Indiana, 2003–04

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

National Water-Quality Assessment Program

Scientific Investigations Report 2006–5251

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

Dirk Kempthorne, Secretary

U.S. Geological Survey

Mark D. Myers, Director

U.S. Geological Survey, Reston, Virginia: 2006

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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. 
Foreword

The U.S. Geological Survey (USGS) is committed to 

providing the Nation with credible scientific information that 

helps to enhance and protect the overall quality of life and 

that facilitates effective management of water, biological, 

energy, and mineral resources (http://www.usgs.gov/). Information on the Nation’s water resources is critical to ensuring 

long-term availability of water that is safe for drinking and 

recreation and is suitable for industry, irrigation, and fish and 

wildlife. Population growth and increasing demands for water 

make the availability of that water, now measured in terms 

of quantity and quality, even more essential to the long-term 

sustainability of our communities and ecosystems.

The USGS implemented the National Water-Quality 

Assessment (NAWQA) Program in 1991 to support national, 

regional, State, and local information needs and decisions 

related to water-quality management and policy (http://water.

usgs.gov/nawqa). The NAWQA Program is designed to 

answer: What is the condition of our Nation’s streams and 

ground water? How are conditions changing over time? How 

do natural features and human activities affect the quality of 

streams and ground water, and where are those effects most 

pronounced? By combining information on water chemistry, 

physical characteristics, stream habitat, and aquatic life, the 

NAWQA Program aims to provide science-based insights 

for current and emerging water issues and priorities. From 

1991–2001, the NAWQA Program completed interdisciplinary assessments and established a baseline understanding of 

water-quality conditions in 51 of the Nation’s river basins and 

aquifers, referred to as Study Units (http://water.usgs.gov/

nawqa/studyu.html). 

Multiple national and regional assessments are ongoing 

in the second decade (2001–2012) of the NAWQA Program 

as 42 of the 51 Study Units are reassessed. These assessments 

extend the findings in the Study Units by determining status 

and trends at sites that have been consistently monitored for 

more than a decade and filling critical gaps in characterizing 

the quality of surface water and ground water. For example, 

increased emphasis has been placed on assessing the quality 

of source water and finished water associated with many of 

the Nation’s largest community water systems. During the 

second decade, NAWQA is addressing five national priority topics that build an understanding of how natural features 

and human activities affect water quality and establish links 

between sources of contaminants, the transport of those 

contaminants through the hydrologic system, and the potential 

effects of contaminants on humans and aquatic ecosystems. 

Included are topics on the fate of agricultural chemicals, 

effects of urbanization on stream ecosystems, bioaccumulation 

of mercury in stream ecosystems, effects of nutrient enrichment on aquatic ecosystems, and transport of contaminants 

to public-supply wells. These topical studies are conducted in 

those Study Units most affected by these issues; they comprise a set of multi-Study-Unit designs for systematic national 

assessment. In addition, national syntheses of information 

on pesticides, volatile organic compounds (VOCs), nutrients, 

selected trace elements, and aquatic ecology are continuing. 

The USGS aims to disseminate credible, timely, and 

relevant science information to address practical and effective 

water-resource management and strategies that protect and 

restore water quality. We hope this NAWQA publication will 

provide you with insights and information to meet your needs 

and will foster increased citizen awareness and involvement 

in the protection and restoration of our Nation’s waters. 

The USGS recognizes that a national assessment by a 

single program cannot address all water-resource issues of 

interest. External coordination at all levels is critical for costeffective management, regulation, and conservation of our 

Nation’s water resources. The NAWQA Program, therefore, 

depends on advice and information from other agencies—

Federal, State, regional, interstate, Tribal, and local—as well 

as nongovernmental organizations, industry, academia, and 

other stakeholder groups. Your assistance and suggestions are 

greatly appreciated.

 Robert M. Hirsch

 Associate Director for Water

iii
Contents

Foreword ........................................................................................................................................................iii

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................1

Purpose and Scope ..............................................................................................................................2

Description of Basin and Sampling Sites .........................................................................................2

Methods of Investigation..............................................................................................................................5

Field Methods........................................................................................................................................5

Laboratory Analyses, Data Presentation, and Quality-Control Assurance.................................8

Data Analysis ......................................................................................................................................10

Occurrence of Agricultural Chemicals in Leary Weber Ditch Basin ..................................................11

Rain........................................................................................................................................................12

Soil Water.............................................................................................................................................12

Ground Water......................................................................................................................................22

Tile-Drain Water..................................................................................................................................24

Overland-Flow Water.........................................................................................................................26

Leary Weber Ditch..............................................................................................................................26

Transport of Agricultural Chemicals in Leary Weber Ditch Basin.......................................................27

Mixing Analysis...................................................................................................................................28

Uncertainty in Results of Mixing Analysis......................................................................................31

Summary........................................................................................................................................................33

Acknowledgments.......................................................................................................................................33

References Cited..........................................................................................................................................33

iv

Figures

1.-2. Maps showing:

1. Location of Leary Weber Ditch Basin, Indiana, and sampling sites within 

the basin.........................................................................................................................................3

2. Approximate tile-drain locations in Leary Weber Ditch Basin, Indiana..............................4

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.........................................6

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 .....................7

5. Example standard schematic boxplot showing central tendency and variability 

of water-quality concentrations.................................................................................................8

6. Diagrams showing quality-control results for field-blank samples for pesticides, 

nutrients, and major ions collected in Leary Weber Basin, Indiana, 2003-04 ....................9
Figures—Continued

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 .............................................................................................................10

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)............................................................................................11

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..........13

10. Boxplots showing distribution of concentrations of selected pesticide parent 

and pesticide degradate compounds in Leary Weber Ditch and in each 

hydrologic compartment sampled in Leary Weber Ditch Basin, Indiana, 2003–04 .........14

11. Graphs showing relation of selected pesticide concentrations to streamflow 

for the hydrologic compartments sampled in Leary Weber Ditch Basin, Indiana, 

2003–04 .........................................................................................................................................17

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 ....................................................................................................19

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...........................................................................................................20

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....................................................................22

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 ...................................23

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 ....................25

17. Comparison of alachlor concentrations measured in rain and overland-flow 

water during storm 5 in Leary Weber Ditch Basin, Indiana, 2004 ......................................26

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..........................................................29
vi

Tables

1. Pesticide parent compounds and pesticide degradates analyzed for in 

water samples from Leary Weber Ditch Basin, Indiana, 2003–04......................................36

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 .............................39

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 ....................................................................................................28

4. Estimates of overland flow contributions to Leary Weber Ditch, Indiana, 

for selected storms, 2003–04 ....................................................................................................32

Vertical coordinate information is referenced to the North American Vertical Datum of 1998 

(NAVD 88).

Altitude, as used in this report, refers to distance above the vertical datum.

Concentrations of chemical constituents in water are given either in milligrams per liter (mg/L) 

or micrograms per liter (μg/L).

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

inch (in.) 25.4 millimeter (mm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

acre 0.4047 hectare (ha)

acre 0.004047 square kilometer (km2)

square mile (mi2) 259.0 hectare (ha)

square mile (mi2) 2.590 square kilometer (km2) 

Volume

gallon (gal) 3.785 liter (L)

gallon (gal) 0.003785 cubic meter (m3)

cubic foot (ft3) 0.02832 cubic meter (m3)

Flow rate

cubic foot per second (ft3/s) 0.02832 cubic meter per second (m3/s)

gallon per minute (gal/min) 0.06309 liter per second (L/s)

inch per hour (in/h) 0.0254 meter per hour (m/h)

Conversion Factors and Datum
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.

Introduction

Leary Weber Ditch Basin in 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 Team (ACT) study (Capel and others, 

2004) conducted by the National Water-Quality Assessment 

(NAWQA) Program of the U.S. Geological Survey (USGS). 

The goal of the ACT study is to assess the fate and transport 

of chemicals applied to crops in agricultural basins across the 

Nation. Chemicals selected for nationwide ACT study include 

nutrients (nitrogen and phosphorus), major ions, and about 

43 commonly used pesticides and 39 degradation products 

(including triazine herbicides such as atrazine and simazine, 

acetanilide herbicides such as acetochlor and metolachlor, 

and organophosphorus insecticides such as chlorpyrifos and 

diazinon). Because the herbicide glyphosate is so important in 

the Midwest, glyphosate and its degradate aminomethylphosphonic acid (AMPA) also were selected for analysis in the 

Leary Weber Ditch study in 2004 as part of the USGS Toxic 

Substances Hydrology Program.

The basins in the ACT study represent a variety of 

agricultural settings with different crop types and agricultural 

practices related to tillage, irrigation, artificial drainage, and 

chemical use, as well as a range of landscapes with different 

geology, soils, topography, climate, and hydrology (Capel and 

others, 2004). Leary Weber Ditch Basin was selected for study 

because it is typical of an artificially drained (subsurface tile 

drains) Midwestern basin with corn and soybean row cropping. In areas with poorly drained soils, tile drains are used to 

Occurrence and Transport of Agricultural Chemicals 

in Leary Weber Ditch Basin, Hancock County, Indiana, 

2003–04

By Nancy T. Baker, Wesley W. Stone, John T. Wilson, and Michael T. Meyer 
facilitate access to and cultivation of agricultural land. During 

the 1980s, the U.S. Department of Agriculture (USDA) estimated that approximately 50 percent of all cropland in Indiana 

was drained; tiles drain approximately 70 percent of that cropland. The USDA estimated that Indiana ranked second in the 

U.S. in total land area where artificial surface and subsurface 

drainage is used (U.S. Department of Agriculture, 1987).

The ACT study is designed to increase the understanding of the links between the sources of water and agricultural 

chemicals (nutrients and pesticides) and the fate and transport 

of these chemicals through the environment. Understanding the fate and transport of these chemicals in the study 

basins may help predict the fate and transport of agricultural 

chemicals in other agricultural areas. This information will 

help managers target the implementation of best management 

practices to those hydrologic compartments that are the most 

conducive to the transport of agricultural chemicals.

Purpose and Scope

This report documents the occurrence of agricultural 

chemicals in Leary Weber Ditch and in the major hydrologic 

compartments of the Leary Weber Ditch Basin during 2003 

and 2004. Hydrologic compartments that contribute water and 

agricultural chemicals to Leary Weber Ditch are rain water, 

overland-flow water, soil water, tile-drain water, and ground 

water. Water samples were collected during four storms in 

2003 and three storms in 2004 from the Tile Drain, Overland 

Flow, and Leary Weber Ditch sites. In addition, stable-flow 

samples were collected between storms at the Tile Drain and 

Leary Weber Ditch sites. Weekly composite rain samples 

were collected for 13 weeks in 2003 and 2004. Soil-water and 

ground-water samples were collected at selected times during 

2003 and 2004. The samples were analyzed for selected pesticides, nutrients, and major ions. This report also describes the 

transport of water and chemicals from the major hydrologic 

compartments to Leary Weber Ditch based on a mass-balance 

mixing analysis and analyses of hydrologic and chemical data 

from each of the hydrologic compartments.

Description of Basin and Sampling Sites

Leary Weber Ditch is a 2.73 mi2 intensively farmed 

drainage basin dominated by poorly drained soils in Hancock 

County, east-central Indiana (fig. 1). The USGS maintains 

streamflow gaging station 03361638, Leary Weber Ditch 

at Mohawk, IN (hereafter referred to as the gaging station). 

Agriculture is the principal land use, with 87 percent of the 

total land area in row crops. Leary Weber Ditch is an intermittent stream and a tributary to Sugar Creek. The ditch has been 

dredged along much of its reach to facilitate drainage of the 

shallow water table. Successful farming requires lowering the 

water table and removing ponded water by artificially draining 

the fields through tiles. Flow in Leary Weber Ditch is sustained primarily from tile-drain contributions. Large changes 

in flow are tied to snowmelt and rainfall, with flow diminishing quickly between periods of precipitation. A more complete 

description of the basin can be found in Lathrop (2006).

Tile-drain systems are extensive in the basin; field reconnaissance showed 58 tile-drain outlets along the 2.86-mi 

length of Leary Weber Ditch. This number of outlets is conservative because 0.3 mi of the ditch was not accessible during 

the reconnaissance. The drains typically are installed 3 to 

4 ft below the land surface, with an average outlet spacing of 

200 ft. Tile-drain outlets represent individual tiles or collector 

tiles that combine discharge water from a network of tiles that 

may drain several fields. Approximate locations of tile drains 

in the basin are shown in figure 2. Tile locations were derived 

from landowner recollection, tile-drain outlets, and infrared 

aerial photography. Because it was not possible to verify tile 

locations derived from infrared aerial photography, precedence 

for estimating locations was given to landowner recollection 

and tile-drain outlets. 

The Leary Weber Ditch Basin is topographically flat. A 

few land areas adjacent to the ditch have overland runoff; areas 

farther away hold ponded water, unless they too are drained 

by tile drains. The areas where overland runoff can occur are 

usually small field-size depressions that drain directly into the 

ditch, commonly through a culvert that runs beneath the berm 

of the ditch bank. The Overland Flow site is one of 17 overland flow culverts along the length of Leary Weber Ditch. 

The Overland Flow site is a 3.5-acre depression with a culvert 

for drainage at the mouth. The contributing area for runoff is 

variable and dependent upon the magnitude and intensity of 

rainfall. Field observations during rainfall indicate that runoff 

occurs mainly as sheet and rivulet flow to the discharge point. 

The potential contributing areas of the other 16 culverts were 

not determined. 

A sampling plan was established so that chemicals in 

Leary Weber Ditch Basin could be accounted for from their 

point of entry into the basin, their storage or degradation 

within the basin, or until their departure by flow out of the 

basin through Leary Weber Ditch (Lathrop, 2006). A wide 

variety of water-quality sampling sites were established 

throughout the basin to evaluate the occurrence and movement 

of water and chemicals into Leary Weber Ditch and between 

the hydrologic compartments: rain, soil water, ground water, 

tile-drain water, and overland-flow water. Five monitoring 

sites were established to characterize Leary Weber Ditch and 

the various hydrologic compartments: the North, South, Tile 

Drain, Overland Flow, and Leary Weber Ditch sites (fig. 1). 

The North site was equipped to monitor rain quantity and 

quality, and both the North and South sites were equipped to 

monitor soil-water levels, soil-water quality and ground-water 

quality. The Tile Drain and Overland Flow sites were equipped 

to monitor both flow and quality of the water flowing from 

those hydrologic compartments. The Leary Weber Ditch site 

was equipped to monitor flow and water quality. A moredetailed site and instrumentation list is available in appendix 1 

of Lathrop (2006).

   Occurrence and Transport of Agricultural Chemicals in Leary Weber Ditch Basin, Hancock County, Indiana, 2003–04
39

o

51'00"

85

o

51'00" 85

o

50'00"

39

o

52'00"

County boundary

Basin boundary

Overland Flow basin boundary

Town

Water-quality station

Streamflow-gaging station

0 0.5 1 Kilometer

0 0.5 1 Mile

Leary

Weber Ditch

Sugar Creek

Base From 2003 National Agricultural Imagery Program,

County Tiles for Indiana, Hancock, County.

Universal Transverse Mercator projection, Zone 16,

North American Datum, 1983

Tile Drain

Leary Weber

Ditch

Overland Flow

North Site

South Site

Figure 1. Location of Leary Weber Ditch Basin, Indiana, and sampling sites within the basin.

MoMhh

Mohawk

Indiana

Indiana

Ohio

EXPLANATION

Hancock County

Sugar Creek

Leary Weber

Ditch Basin

Mohawk

Oxford

Indianapolis

Introduction 3
Leary Weber Ditch Basin

Tile drain

Tile-drain outlet

Overland-flow outlet

39

o

51'00"

85

o

51'00"

85

o

50'00"

39

o

52'00"

0 0.5 1 Kilometer

0 0.5 1 Mile

Leary

Weber

Ditch

Base from Hancock County, Ind.,

2-foot-contour digital elevation data, 2001.

Universal Transverse Mercator projection,

Zone 16, North American Datum, 1983

EXPLANATION

Figure 2. Approximate tile-drain locations in Leary Weber Ditch Basin, Indiana

4 Occurrence and Transport of Agricultural Chemicals in Leary Weber Ditch Basin, Hancock County, Indiana, 2003–04
The crops and agricultural practices were the same for 

the fields at the North, South, Tile Drain, and Overland Flow 

sites during 2003 and 2004. Corn was grown on the study-site 

fields in 2003. Fertilizer as anhydrous ammonia was applied to 

the fields at the North, South, Tile Drain, and Overland Flow 

sites in late April 2003. The herbicides atrazine and acetochlor 

were applied to those fields in mid-May 2003. Soybeans were 

grown in the study-site fields in 2004. Glyphosate was applied 

to those fields in mid-May 2004. All of the crops in study-site 

fields were harvested in late October and early November of 

both years. More-detailed estimates of chemical usage for the 

entire basin for 2003 and 2004 are given in Lathrop (2006).

Methods of Investigation

Methods used for this study encompass field activities, 

laboratory procedures, and data analysis. Discussion of the 

field-activity methods includes the water sampling plans used 

for each hydrologic compartment in the study. Discussion 

of laboratory-procedure methods includes references to the 

preparation and handling of the samples and the analytical 

procedures used for the targeted chemicals. Water samples 

were analyzed for pesticides, nutrients, and major ions. Discussion of data-analysis methods includes the description of a 

mass-balance mixing analysis used in this report.

Field Methods

Water samples were collected manually or by automatic sampler throughout the planting (April–May), growing 

(June–September), and harvest (October–November) periods 

in 2003 and 2004. Discrete water samples were collected by 

automatic sampler from the Tile Drain, Overland Flow, and the 

Leary Weber Ditch sites during storms. For chemical analysis, three to five samples, based on their relation to the rise, 

peak, and recession of flow were selected from each storm. 

Samples were collected throughout the growing season during 

four storms in 2003 and during three storms in 2004 (fig. 3A). 

Because of equipment failure, tile-drain samples were not collected during most of storm 3 in 2003. Overland-flow samples 

were collected only during storms 4 (partial collection), 5, and 

6. There was no surface runoff at the Overland-Flow site during storms 1, 2, and 7. The Overland Flow site instrumentation 

was flooded during storms 3 and 4 (partial collection), limiting 

the number of overland-flow samples collected during these 

storms. Samples collected during storm 7 were analyzed only 

for nutrients. Between storms and during periods of stable 

flow, water samples were collected manually at the Tile Drain 

and the Leary Weber Ditch sites. 

Discrete samples were collected from lysimeters (pan 

and suction) and wells at selected times during 2004 (fig. 3B 

and C). Pan lysimeters are designed to intercept water moving down the soil profile through macropores. Pan lysimeters 

(installed only at the North site) were constructed by inserting 

a 1-ft2 flat pan into the soil profile, 2 ft below the land surface. Soil water drained by gravity into the pan; from there, 

it drained into a collection chamber that could be evacuated 

for sampling with a peristaltic pump. Suction lysimeters are 

designed to pull water from the soil matrix. Suction lysimeters were constructed with a combination internal chamber 

and porous ceramic cup at one end, and sampling tubes at the 

other end. Samples were collected by applying suction to the 

lysimeter, thereby creating a negative pressure in the internal 

chamber and drawing soil moisture through the ceramic cup 

into the internal chamber. Suction was applied to the lysimeter 

24 hours prior to evacuating the internal chamber to allow 

enough time for the soil moisture to be drawn into it. Suctionlysimeter samples were collected from the North and South 

sites at depths of 3, 4, 5, and 6 ft below the land surface. 

Wells at the North and South sites were installed to collect samples from soil water and ground water in 2003 and 

2004. At these two sites, the first appearance of saturated 

sand-and-gravel aquifer material was generally 9 ft or greater 

below land surface (fig. 4). The wells installed with screens 

less than 9 ft below land surface were used to characterize water in the soils and the shallow water table. The wells 

installed with screens greater than 9 ft below land surface were 

used to characterize ground water. Screen lengths in all wells 

were 2 ft. This allowed discrete sampling from the following 

approximate intervals, 3 to 5 ft, 5 to 7 ft, 7 to 9 ft, 9 to 11 ft, 

and 12 to 14 ft below land surface. Soil-water and groundwater samples were analyzed for pesticides, nutrients, and 

major ions.

A refrigerated wet-deposition sampler at the North site 

collected weekly composite rain samples for 13 weeks in 2003 

and 2004; these samples were analyzed for pesticides. Rain 

samples were not analyzed for major ions or nutrients in 2003. 

Rain samples were analyzed for nitrate in 2004 but were not 

analyzed for major ions or other nutrients. Rain samples were 

analyzed only if there was enough rain water collected for the 

analytical method. 

The timing of tile-drain, overland-flow, and Leary Weber 

Ditch water-quality sample collection was targeted at characterization of agricultural-chemical movement during storms 

throughout the growing season and not on a fixed frequency 

during 2003 and 2004. In contrast, the soil-water and groundwater sample collection was done on a fixed frequency, regardless of the timing of the storms. The tile-drain, overland-flow, 

and Leary Weber Ditch samples may be biased high relative 

to soil-water and ground-water samples because storms were 

targeted and sampling was not done on a fixed frequency. 

Methods of Investigation 
STREAMFLOW, IN CUBIC FEET PER SECOND

3

0.1

1.0

10

100

300

0.05

HYDROLOGIC COMPARTMENT DEPTH BELOW LAND SURFACE, IN FEET

Figure 3. 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 and samplecollection times in the soil-water and ground-water hydrologic compartments.

Storm: 1 2 4 5 6 7

Rain

Soil

Ground

water

Tile

drain

Overland

flow

Leary

Weber

Ditch

0.0

1.0

2.0

3.0

4.0

5.0

6.0

7.0

2003

Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

2004

2003

Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

2004

2003

Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

2004

A

B

C

Sample-collection

 times

EXPLANATION

Agricultural chemical group

 sampled

Major ions

Pesticides

Nutrients

Group not sampled

EXPLANATION

EXPLANATION

Storms targeted for 

 water-quality sampling

Streamflow

Water level

Figure 3. 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.

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

WELL 1C WELL 1D WELL 1B WELL 1A

Land surface

Sand and gravel zone

Screened interval RELATIVE DISTRIBUTION OF PARTICLE SIZE

14

12

10

8

6

4

2

DEPTH BELOW LAND SURFACE, IN FEET

W E

WELL 2D WELL 2A WELL 2B WELL 2C

Land surface

Sand and gravel zone

Hard clay and silt

NORTH SITE

SOUTH SITE

0

14

12

10

8

6

4

2

DEPTH BELOW LAND SURFACE, IN FEET

0

16

Gravel

Sand

Silt

Clay

EXPLANATION

Water level on June 24, 2003

Horizontal position not to scale

Horizontal position not to scale

Figure 4. Depths of the screened intervals of wells used to sample soil water and ground water and relative 

distribution of particle sizes in soil cores sampled at the North and South sites in Leary Weber Ditch Basin, 

Indiana.

Figure 4. 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.

Methods of Investigation 
Laboratory Analyses, Data Presentation, and 

Quality-Control Assurance

The handling, filtering, and preparation of water samples 

followed standard USGS sample-collection procedures 

(U.S. Geological Survey, variously dated). Samples were 

iced and shipped overnight for analysis at the USGS National 

Water Quality Laboratory (NWQL) in Denver, Colo., and 

the Organic Geochemistry Research Laboratory (OGRL) 

in Lawrence, Kans. NWQL analyzed the water samples for 

major ions, nutrients, and pesticides, following the methods 

described by Fishman (1993), Fishman and Friedman (1989), 

and the American Public Health Association (1998). Nitrate 

concentrations reported here are the combination of nitrate 

and nitrite as nitrogen (N). Of 163 samples analyzed for 

nitrite plus nitrate and nitrite only, the average contribution 

of nitrite to nitrate plus nitrite was 0.8 percent, with a median 

of 0.0 percent. Therefore, the use of nitrate plus nitrite to 

represent nitrate concentrations appears valid. OGRL analyzed 

the water samples for pesticide degradates, following methods described in Lee and Strahan (2003). In addition, OGRL 

analyzed for glyphosate, following the methods described in 

Lee and others (2002).

The NWQL and OGRL place and store analytical results 

in the USGS National Water Information System (NWIS). 

The water-quality data used in this report were retrieved from 

NWIS on October 27, 2005. The unedited pesticide, nutrient, 

and major ion data are available in USGS Digital Data Series 

214 at URL http://pubs.usgs.gov/ds/2006/214/.

The unedited data were processed to facilitate analysis 

and presentation in this report. Specifically, the data were 

edited so that all values with a “less than” (<) remark code 

(not detected) were set to a zero value. All values with a 

remark code of “E” (estimated value) were unchanged in the 

editing process. Reporting levels for some pesticides were 

lowered by NWQL and OGRL during the second year of the 

study. This change in reporting levels from 2003 to 2004 could 

affect the frequency-of-detection discussion because more 

detections may occur with the lower reporting level in the 

second year than in the first year. A list of all pesticides and 

pesticide degradates and their most common reporting levels 

for 2003 and 2004 are given in table 1 (at back of report).

For graphical presentation of chemical concentrations, 

the data were edited so that the “less than” remark code 

equaled the most common reporting level for that chemical 

during the 2-year study. All values with a remark code of “E” 

were unchanged in the editing process. Edits of the data and 

the changes in reporting levels for some chemicals biases the 

presentation of some of the results toward the most common 

reporting level. 

Standard schematic boxplots were used in this report 

to show graphically the central tendency and distribution of 

concentrations for selected agricultural chemicals within each 

hydrologic compartment (fig. 5). Boxplots provide a visual 

summary of the center of the data (the median, centerline of 

the box), the variation or spread (interquartile range, the box 

height), the skewness (quartile skew, the relative size of box 

halves), and the presence or absence of unusual values (Helsel 

and Hirsch, 1992). The whiskers on the boxplots extend only 

to the last observation within one step (1.5 times the height 

of the box) beyond either end of the box (adjacent values) 

(fig. 5). Observations between one and two steps from the box 

in either direction are plotted with an X (outside values); and 

observations farther than two steps beyond the box are plotted with a small circle (detached values) (Helsel and Hirsch, 

1992). 

x

x

o

o

Upper adjacent

75th percentile

Median

25th percentile

Lower adjacent

Lower outside

Lower detached

Upper detached

Upper outside

0.1

1

10

CONCENTRATION

0.01

Figure 5. Example standard schematic boxplot showing

central tendency and variability of water-quality

concentrations.

Figure 5. Example standard schematic boxplot 

showing central tendency and variability of waterquality concentrations. 

Quality-control (QC) methods were used to evaluate the 

sampling bias and variability for samples collected for this 

study. The three QC methods used for this study are collection 

and analysis of field replicates, field blanks, and equipment 

replicates. Procedures used for collecting QC samples are 

explained in Mueller and others (1997) and Koterba and others 

(1995). Field replicates are used to assess the variability or 

reproducibility associated with water-quality sample collection 

and laboratory procedures. A large number of field-replicate 

QC samples are needed to determine adequately the variability 

in samples. Because all NAWQA sample-collection methods follow protocols and are collected in the same manner, 

it is more useful to analyze all of the field-replicate samples 

collected by all NAWQA study units across the U.S. An 

assessment of the variability and reproducibility of NAWQA 

samples is given for pesticides in Martin (2001) and for nutrients in Mueller and Titus (2005). QC methods specific to this 

study include field-blank and equipment-replicate samples. 

Field blanks were analyzed to assess the degree of contamination introduced during field processing and handling 

and laboratory handling and analysis of samples. Field blanks 

 Occurrence and Transport of Agricultural Chemicals in Leary Weber Ditch Basin, Hancock County, Indiana, 2003–04
were prepared by subjecting a blank solution (water known to 

contain none of the target analytes at quantifiable concentrations) to all aspects of sample collection, field processing, 

preservation, transportation, and laboratory handling and 

analyses that the non-QC samples (hereafter referred to as 

environmental samples) were subjected. A total of eight field 

blanks were prepared during the course of the study. Atrazine 

and metolachlor were detected in the blank samples but both 

concentrations were below the most common reporting level 

for the pesticides detected (fig. 6). Total nitrogen was detected 

in all of the blank samples, and orthophosphate was detected 

in 33 percent of the blank samples. Total nitrogen concentrations in blank samples were 100 times lower than average total 

nitrogen concentrations in environmental samples; orthophosphate concentrations in the blank samples were about 10 times 

lower than average orthophosphate concentrations in environmental samples (fig. 6). Calcium and magnesium ions were 

detected in all of the blank samples, and sodium ions were 

detected in 66 percent of the blank samples. Concentrations, 

however, were well below the average concentrations measured in the environmental samples (fig. 6).

Equipment-replicate samples were collected and analyzed 

to determine if the automatic sampler intake lines and bottles 

influenced chemical concentrations in the environmental 

samples. Replicates were grab samples collected simultaneously with the automatic sampler. After collection, both sets 

of samples were handled and processed identically. A total of 

11 replicate samples were collected at the Tile Drain, Overland 

Flow, and Leary Weber Ditch sites during the study. Analysis 

of the replicate samples and the corresponding environmental 

samples showed that, for pesticides, there was more variability 

between the replicate and environmental samples at concentrations greater than 2 μg/L but a consistent bias was not present 

(fig. 7). The variability between replicate and environmental 

samples for nutrients and major-ion analyses was low, and a 

consistent bias was not present (fig. 7). 

0 20 40 60 80 100

Atrazine

Metolachlor

Orthophosphate

Total Nitrogen

Calcium

Magnesium

Sodium

FREQUENCY OF DETECTION, PERCENT

Pesticides

Nutrients

Major ions

A

0.001 0.01 0.1 1 10 100

Atrazine

Metolachlor

Orthophosphate

Total Nitrogen

Calcium

Magnesium

Sodium

CONCENTRATION (PESTICIDES, IN MICROGRAMS PER LITER, 

AND NUTRIENTS AND MAJOR IONS, IN MILLIGRAMS PER LITER)

Pesticides

Nutrients

Major ions

Most common reporting level

Maximum field-blank concentration

Average environmental sample concentration

B

Figure 6. Quality-control results for field-blank samples for pesticides, nutrients, and major ions collected in Leary Weber Basin, 

Indiana, 2003-04. Graphs include only target analytes detected in field-blank samples. Graph A shows the frequency of detection in 

percent. Graph B shows the relation between the most common reporting level, the maximum concentration detected in the field-blank 

sample, and the average concentration of the target analyte for all environmental samples collected.

Methods of Investigation 
PESTICIDES

0

2

4

6

8

0 2 4 6 8

ENVIRONMENTAL SAMPLE, PESTICIDE 

CONCENTRATION, IN MICROGRAMS PER LITER

REPLICATE SAMPLE

PESTICIDE CONCENTRATION,

IN MICROGRAMS PER LITER

NUTRIENTS

0

5

10

15

20

0 5 10 15 20

MAJOR IONS

0

50

100

150

200

0 50 100 150 200

ENVIRONMENTAL SAMPLE, MAJOR-ION 

CONCENTRATION, IN MILLIGRAMS PER LITER

REPLICATE SAMPLE

MAJOR-ION CONCENTRATION,

IN MILLIGRAMS PER LITER

ENVIRONMENTAL SAMPLE, NUTRIENT 

CONCENTRATION, IN MILLIGRAMS PER LITER

REPLICATE SAMPLE

NUTRIENT CONCENTRATION,

IN MILLIGRAMS PER LITER

Figure 7. 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. Replicate samples were collected by the grab 

method at the same time a corresponding sample was collected by the automatic sampler for Tile Drain, 

Overland Flow, and Leary Weber Ditch sites. Graphs include all target compounds analyzed in each group: 

pesticides, nutrients, and major ions.

A

B

C

Figure 7. 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. Replicate samples were collected by the 

grab method at the same time a corresponding sample 

was collected by the automatic sampler for Tile Drain, 

Overland Flow, and Leary Weber Ditch sites. Graphs 

include all target compounds analyzed in each group: 

pesticides, nutrients, and major ions.

Data Analysis 

The relative contributions of water and chemicals from 

each of the hydrologic compartments to Leary Weber Ditch 

were determined through examination of ancillary data and 

the use of a mass-balance mixing analysis. A mass-balance 

mixing analysis, based on the efforts of Stone and Wilson 

(2006), was used to determine the overland-flow and tiledrain contributions to Leary Weber Ditch. Stone and Wilson 

(2006) used a two-source mass-balance mixing approach with 

chloride as a conservative chemical tracer to separate tile-drain 

flow into preferential and soil-matrix flows for storm hydrographs. The mass-balance mixing analysis can be used for 

more than two sources; however, the analysis requires the total 

chemical tracers to number one less than the total number of 

sources included in the analysis. Because two sources dominate flow in Leary Weber Ditch, the mass-balance mixing 

analysis required only one chemical tracer, which simplified 

the calculations. 

Leary Weber Ditch potassium concentrations and flow 

values were used with the assumed potassium concentrations 

representing tile-drain and overland-flow water in the following conservation of mass equations to estimate the contributions from both sources:

Qlwd = Qtd + Qof

QlwdClwd = QtdCtd + QofCof

The use of the above conservation of mass equations 

assumes there are no other major sources or sinks of potassium or water to Leary Weber Ditch. The terms Qlwd, Qtd, and 

Qof, represent flow from Leary Weber Ditch, tile drains, and 

overland flow areas, respectively. Clwd, Ctd, and Cof, represent 

the potassium concentrations in Leary Weber Ditch, tile-drain, 

and overland-flow water. The values of Qlwd were measured. 

The value used for Ctd was the median Leary Weber Ditch 

potassium concentration when flow was between the 50th and 

100th percentiles, where Cof was the median of the chloride 

concentrations measured in overland flow. The Clwd values 

were linearly interpolated between the discrete samples. The 

computed flow values for the tile drains and overland flow 

then were plotted against time to produce the separated storm 

hydrographs.

Potassium was used as the chemical tracer because its 

concentrations in overland-flow water and tile-drain water 

were stable and different enough to evaluate mixing based on a 

mass-balance approach. Chloride concentrations, which Stone 

and Wilson (2006) used as a tracer in their mixing analysis 

were too variable in the tile-drain water to use as the chemical tracer for the separation of tile-drain flow and overland 

flow in Leary Weber Ditch. Even though potassium is not as 

conservative as chloride, it is a better tracer for this analysis 

because it does not move well through the soil profile. This 

results in lower amounts of potassium being present in soil 

water and ground water (Mallarino, 2006). Degradation of 

organic materials and field application of potash make potas10 Occurrence and Transport of Agricultural Chemicals in Leary Weber Ditch Basin, Hancock County, Indiana, 2003–04
sium levels higher in overland flow than in the other hydrologic compartments; rainfall, with its lower pH, mobilizes 

potassium in overland flow. The median tile-drain potassium 

concentration was 0.37 mg/L, with a range of 0.22 mg/L to 

1.03 mg/L. At low flows, Leary Weber Ditch water is entirely 

from tile drains. Figure 8 shows potassium concentrations in 

Leary Weber Ditch for four selected ranges of flow duration. 

The median concentration of potassium in Leary Weber Ditch 

(0.96 mg/L), for samples collected when flow was between 

the 50th and 100th percentiles, was used to represent tile-drain 

contributions of potassium. The median overland-flow potassium concentration was 5.24 mg/L, with a range of 2.39 mg/L 

to 9.65 mg/L. The median concentration of potassium at 

the Overland Flow site was used to represent overland-flow 

contributions to Leary Weber Ditch. Stone and Wilson (2006) 

used a relation between specific conductance and chloride 

to estimate chloride concentrations throughout the tile-drain 

storm hydrographs; however, the analysis in this report did 

not have a mechanism to estimate potassium concentrations 

throughout the Leary Weber Ditch storm hydrographs. Linear 

interpolation between discrete samples on the storm hydrograph was used to estimate contributions from tile drains and 

overland flow.

Occurrence of Agricultural Chemicals 

in Leary Weber Ditch Basin

The hydrologic compartments in Leary Weber Ditch 

Basin are defined by chemical and physical similarities and 

are linked inherently, such as soil water and tile drains. For the 

purposes of this report, the hydrologic compartments are rain, 

soil water (sampled with lysimeters and wells placed within 

the top 9 ft of the soils in non-aquifer materials), ground water 

(wells screened in the first available aquifer material [saturated 

sand and gravel] greater than 9 feet below land surface), tiledrain water, overland-flow water (surface runoff), and Leary 

Weber Ditch (the receiving stream for water flowing through 

or from the hydrologic compartments). 

Agricultural chemicals were detected in Leary Weber 

Ditch and in every associated hydrologic compartment 

sampled during 2003 and 2004 (Baker and Lathrop, 2006). As 

noted previously, samples were collected from the tile-drain, 

overland-flow, and Leary Weber Ditch during storms, rather 

than at a fixed frequency throughout the 2 years. This targeted 

sample collection likely provided a high bias in terms of the 

frequency of detection of the agricultural chemicals in those 

POTASSIUM CONCENTRATION, IN MILLIGRAMS PER LITER

xx

o

0-5 5-10 10-50 50-100

21 9 23 5 7

6

5

4

3

2

1

0

8.1-17.3

Percent exceedance

>17.3 0.7-8.1 <0.7 Cubic feet per second

23

x

x

o

o

EXPLANATION

Number of values

Upper detached

Upper outside

Upper adjacent

75th percentile

Median

25th percentile

Lower adjacent

Lower outside

Lower detached

FLOW DURATION, IN PERCENT EXCEEDANCE AND

STREAMFLOW, IN CUBIC FEET PER SECOND

Figure 8. Distribution of potassium concentrations at selected ranges of flow duration and streamflow for 

U.S. Geological Survey streamflow-gaging station at Mohawk, IN (03361638).

Occurrence of Agricultural Chemicals in Leary Weber Ditch Basin 11
samples. The lowest concentrations of pesticides and nutrients were in the rain, deep lysimeter, and deep well (soil and 

ground water) samples. The highest concentrations of pesticides and nutrients were in the tile-drain, overland-flow, and 

Leary Weber Ditch samples.

Rain

Numerous pesticides were detected in rain samples, 

including several that were not detected in samples from 

Leary Weber Ditch or in any other hydrologic compartment 

considered in this study (Baker and Lathrop, 2006). Pesticides applied outside the basin may have volatilized or drifted 

through the air and, subsequently, may have been deposited 

in the basin through rainfall. Of the 84 pesticide parent or 

pesticide degradate compounds (table 1) that were evaluated, 

26 were detected in rain samples (table 2, at back of report). 

Pesticide parent or pesticide degradate compounds in more 

than 75 percent of rain samples include aminomethylphosphonic acid (AMPA) (100 percent of the samples), glyphosate (91.2 percent), atrazine (84.6 percent), acetochlor (80.8 

percent), and metolachlor (80.8 percent) (table 2, fig. 9). In 

2004, AMPA was detected in every rain sample and glyphosate was detected in most rain samples. Alachlor, diazinon, 

malaoxon, malathion, metolachlor, pendimethalin, phosmet, 

prometon, and simazine were detected in rain samples (table 

2, fig. 9). These compounds, however, were not applied to the 

fields at the study sites. In general, concentrations of pesticide 

parent compounds were higher than concentrations of their 

degradates. Atrazine and glyphosate concentrations were 

usually higher than their degradates in most samples from 

rain water (fig. 10). Atrazine and glyphosate concentrations 

in rain samples, although not insignificant, were generally 

lower than in tile-drain, overland-flow, or Leary Weber Ditch 

samples (fig. 10). Acetochlor and alachlor concentrations in 

rain samples were similar to overland-flow samples (fig. 10). 

Metolachlor concentrations in rain samples were similar to 

those in Leary Weber Ditch samples (fig. 10). The highest concentrations of all pesticides detected in rain samples occurred 

shortly after chemicals were applied to the fields in the spring 

(fig. 11). Acetochlor and chlorpyrifos concentrations often 

exceeded tile-drain and Leary Weber Ditch concentrations 

(fig 11). The highest atrazine concentration in a rain sample, 

6.58 μg/L, occurred soon after chemical application in 2003 

(fig. 11).

Nutrients and major ions in rain have been studied since 

1984 by the National Atmospheric Deposition Program 

(NADP) (National Atmospheric Deposition Program/National 

Trends Network, 2005) at sites in and near Indiana. Those 

agricultural chemicals were not included for analysis in rain 

samples collected for this study. Rain samples were analyzed 

for nutrients (nitrate only) in 2004 to provide a comparison 

between the NADP samples and samples collected for this 

study. Nitrate as N was detected in every rain sample collected 

in 2004; concentrations ranged from 0.18 to 0.48 mg/L as N 

(Baker and Lathrop, 2006). Concentrations of nitrate in NADP 

samples collected at Oxford, Ohio, (approximately 60 mi 

southeast of the Leary Weber Ditch basin; fig. 1) during the 

same period ranged from 0.50 to 2.22 mg/L as N (National 

Atmospheric Deposition Program/National Trends Network, 

2005). Nitrate concentrations in rain samples were significantly different (Wilcoxon rank-sum p-values < 0.01) than 

those in any other hydrologic compartment. Nitrate concentrations in rain samples were higher than those in overland-flow 

and ground-water samples; they were approximately 10 to 

20 times lower than concentrations in unsaturated soil-water, 

tile-drain water, and Leary Weber Ditch samples (fig. 12).

Soil Water

The soil-water hydrologic compartment was sampled 

with lysimeters and in wells drilled and completed in the soil 

to a depth of 9 ft below land surface in predominantly silt- and 

clay-sized material (fig. 4). In 2003 and 2004, the water table 

in the soil-water hydrologic compartment frequently rose 

above the depths of the lysimeters and well screens (fig. 3C). 

This section describes results of the analyses of samples collected from lysimeters during saturated (water table above the 

depth of the lysimeter) and unsaturated (water table below the 

depth of the lysimeter) conditions. Samples collected from 

wells screened in the soil-water hydrologic compartment are 

considered to represent saturated conditions.

Discrete water samples were collected from soil water 

in 2004. Of the 84 pesticides analyzed, 20 were detected in 

soil-water samples (table 2, fig. 9). Pesticide degradates were 

detected more often than the pesticide parent compounds. 

Pesticide parent and pesticide degradate compounds with a 

75-percent frequency of detection or higher were acetochlor 

ethanesulfunic acid (acetochlor ESA) (100 percent of samples), acetochlor oxanilic acid (acetochlor OXA) (80.4 percent), and alachlor ethanesulfunic acid (alachlor ESA) 

(81.2 percent) (fig. 9). The highest concentrations of alachlor 

ESA were detected in the soil-water hydrologic compartment 

in saturated and unsaturated conditions (fig. 10). For alachlor, 

metolachlor, and acetochlor and their degradates, the concentrations were similar for saturated and unsaturated conditions 

(fig. 10). Concentrations of acetochlor ESA, alachlor ESA, 

and metolachlor ESA were higher than the parent compounds 

in soil-water samples (fig. 10). Atrazine and 2-chloro-4-

isopropylamino-6-amino-s-triazine (deethylatrazine) were 

detected at higher concentrations in soil-water samples collected under saturated conditions than in samples collected 

under unsaturated conditions (fig. 10). Atrazine was detected 

in shallow lysimeters (2 and 3 ft) but not in deeper lysimeters 

(4, 5, and 6 ft) (fig. 13). 

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

Phosphonic

Acid (AMPA)

Alachlor

SAA

Alachlor

OXA

Alachlor

ESA-2nd amide

Alachlor

ESA

Alachlor

Acetochlor/

Metolachlor

ESA-2nd amide

Acetochlor

SAA

Acetochlor

OXA

Acetochlor

ESA

Acetochlor

2-Ethyl-6-methylaniline

1-Naphthol

Figure 9. 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.

FREQUENCY OF DETECTION,

IN PERCENT

100

80

60

40

20

0

n

Malaoxon

Glyphosate

Dimethenamid

OXA

Dimethenamid

ESA

Dimethenamid

Diazinon

Deethylatrazine

Dacthal

Chlorpyrifos

Carbaryl

Azinphosmethyl

Atrazine

25 35 4 31 12 47 26 35 4 31 14 48 26 27 4 31 14 48 23 32 4 30 14 47 23 32 4 30 14 47 23 32 4 30 14 47 12 32 4 14 14 18 26 16 4 31 12 48 23 32 4 30 14 47 12 32 4 14 12 18 23 32 4 30 14 47 23 32 4 30 14 47 12 32 4 14 12 19

26 35 4 31 14 48

FREQUENCY OF DETECTION,

IN PERCENT

100

80

60

40

20

0

n 26 35 4 31 14 48 26 11 4 31 14 49 26 35 4 31 14 49 26 35 4 31 14 48 26 25 2 31 14 48

FREQUENCY OF DETECTION,

IN PERCENT

100

80

60

40

20

0

n 26 29 4 31 14 48 26 25 4 31 14 48

n

*Selected pesticides include those pesticide parent compounds or pesticide degradates detected in at least 10 percent of the samples in at least one hydrologic compartment. See table 2 for a complete list of pesticides for which samples were analyzed and the number of samples collected, number of detections, and frequency of detections.

Leary Weber Ditch water

Ground water

Tile drain water Soil water

Overland flow water Rain

EXPLANATION

Number of samples

Trifluralin

Terbuthylazine

Tebuthiuron

Simazine

Prometon

Phosmet

Pendimethalin

Metolachlor

OXA

Metolachlor

ESA

Metolachlor

Methyl

parathion

Malathion

26 35 4 31 14 49 23 32 4 30 14 47 23 32 4 30 14 47 26 30 4 31 14 48 25 23 4 28 14 45 26 35 2 31 12 49 26 35 4 31 13 48 26 35 4 31 14 48 26 34 4 31 14 48 26 35 4 31 14 48

26 35 4 31 14 49 26 35 4 31 14 48 12 32 4 14 12 18 23 32 4 30 14 47 23 32 4 30 14 47 12 28 2 14 12 19

Figure 9. 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.*Selected pesticides include those pesticide parent compounds or pesticide degradates detected in at least 10 percent of the samples in at least one hydrologic compartment. See table 2 for a complete list of pesticides for which samples were analyzed and the number of samples collected, number of detections, and frequency of detections.

Occurrence of Agricultural Chemicals in Leary Weber Ditch Basin 13
Alachlor ESA reporting level

Alachlor reporting level

Figure 10. Distribution of concentrations of selected pesticide parent and pesticide degradate compounds in Leary 

Weber Ditch and in each hydrologic compartment sampled in Leary Weber Ditch Basin, Indiana, 2003-04.

0.01

0.1

1

ALACHLOR AND ALACHLOR ESA

3

0.003

2003 2004 2004 2004 2004 2003 2004 2003 2004 2003 2004

Alachlor

Alachlor ESA

CONCENTRATION, IN MICROGRAMS PER LITER

13 11 13 12 9 21 7 11 4 4 17 16 14 14 2 2 12 12 30 29 18 18

o o

o

x

o

o o

o

o

o

o

o

o

o

o

o

o

x

o

o

o

x

x

o

o

o

o

+ o

+

Rain

2003 2004

Ground

water

Tiledrain

water

Overlandflow water

Leary

Weber

Ditch

water

2004 2004 2004 2003 2004 2003 2004 2003 2004

Acetochlor ESA reporting level

0.01

0.1

1

10

ACETOCHLOR AND ACETOCHLOR ESA

Acetochlor reporting level

0.003

CONCENTRATION, IN MICROGRAMS PER LITER

Acetochlor

Acetochlor ESA

o

x

o

x

x

x

o

o o

13 11 13 12 18 21 9 11 4 4 17 16 14 14 2 2 12 12 30 29 18 18

o o o o +

+ 14

x

x

o

o

EXPLANATION

Number of values

Upper detached

Upper outside

Upper adjacent

75th percentile

Median

25th percentile

Lower adjacent

Lower outside

Lower detached

Unsaturated soil

water

Saturated

soil

water

Rain Ground

water

Tiledrain

water

Overlandflow water

Leary

Weber

Ditch

water

Unsaturated soil

water

Saturated

soil

water

Figure 10. Distribution of concentrations of selected pesticide parent and pesticide degradate compounds 

in Leary Weber Ditch and in each hydrologic compartment sampled in Leary Weber Ditch Basin, Indiana, 

2003–04.

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

Atrazine reporting level 0.01

0.1

1

10

100

CONCENTRATION, IN MICROGRAMS PER LITER

2003 2004 2004 2004 2004 2003 2004 2003 2004 2003 2004

0.001

ATRAZINE AND DEETHYLATRAZINE

x

oo oo

o

o

o

o o o

13 13 13 13 24 24 11 11 4 4 17 17 14 14 30 30 18 18

Atrazine

Deethylatrazine

2 2 12 12

x

+ +

+ +

0.1

1

100

1000

GLYPHOSATE AND AMPA

10

0.01

Glyphosate and AMPA reporting level

CONCENTRATION, IN MICROGRAMS PER LITER

12 18 21 10 11 2 4 14 14 12 12 19 19

x

x

o

o oo

oo

o ooo o o

Glyphosate

AMPA

12

14

x

x

o

o

EXPLANATION

Number of values

Upper detached

Upper outside

Upper adjacent

75th percentile

Median

25th percentile

Lower adjacent

Lower outside

Lower detached

Figure 10. Distribution of concentrations of selected pesticide parent and pesticide degradate compounds in Leary 

Weber Ditch and in each hydrologic compartment sampled in Leary Weber Ditch Basin, Indiana, 2003-04.-Continued

Rain Ground

water

Tiledrain

water

Overlandflow water

Leary

Weber

Ditch

water

Unsaturated soil

water

Saturated

soil

water

2004 2004 2004 2004 2004 2004 2004

Rain Ground

water

Tiledrain

water

Overlandflow water

Leary

Weber

Ditch

water

Unsaturated soil

water

Saturated

soil

water

Figure 10. Distribution of concentrations of selected pesticide parent and pesticide degradate compounds 

in Leary Weber Ditch and in each hydrologic compartment sampled in Leary Weber Ditch Basin, Indiana, 

2003–04.—Continued

Occurrence of Agricultural Chemicals in Leary Weber Ditch Basin 15
2003 2004 2004 2004 2004 2003 2004 2003 2004 2003 2004

0.01

0.1

1

METOLACHLOR AND METOLACHLOR ESA

Metolachlor reporting level

CONCENTRATION, IN MICROGRAMS PER LITER

0.003

3

Metolachlor

Metolachlor ESA

x

o

o

13 11 13 12 24 21 11 11 4 4 17 16 14 14 12 12 31 29 18 18

Metolachlor ESA reporting level

2 2

o o

o

o

x

o

o

o o

o

o

x

o

o

o

o

o

o

x

+

+

30

x

x

o

o

EXPLANATION

Number of values

Upper detached

Upper outside

Upper adjacent

75th percentile

Median

25th percentile

Lower adjacent

Lower outside

Lower detached

Figure 10. Distribution of concentrations of selected pesticide parent and pesticide degradate compounds in Leary 

Weber Ditch and in each hydrologic compartment sampled in Leary Weber Ditch BasinIndiana2003-04-Continued

Rain Ground

water

Tiledrain

water

Overlandflow water

Leary

Weber

Ditch

water

Unsaturated soil

water

Saturated

soil

water

Figure 10. Distribution of concentrations of selected pesticide parent and pesticide degradate compounds 

in Leary Weber Ditch and in each hydrologic compartment sampled in Leary Weber Ditch Basin, Indiana, 

2003–04.—Continued

16  Occurrence and Transport of Agricultural Chemicals in Leary Weber Ditch Basin, Hancock County, Indiana, 2003–04
0.1

1

10

100

300

0.05

ATRAZINE

CONCENTRATION, IN MICROGRAMS PER LITER

STREAMFLOW, IN CUBIC FEET PER SECOND

Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 

2003 2004

Storm 2

EXPLANATION

Figure 11. Relation of selected pesticide concentrations to streamflow in rain, overland-flow, tile-drain, and Leary 

Weber Ditch water in Leary Weber Ditch Basin, Indiana, 2003-04.

Streamflow

Leary Weber 

 Ditch water

Overland-

 flow water

Rain

Tile-drain

 water

0.01

0.1

1

10

Atrazine reporting level

60

0.004

0.1

1

10

100

300

0.05

ACETOCHLOR

Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 

2003 2004

CONCENTRATION, IN MICROGRAMS PER LITER

STREAMFLOW, IN CUBIC FEET PER SECOND

Acetochlor reporting level

0.01

0.1

1

3

0.004

Pesticide application

Storm 1

Storm 3

Storm 4

Storm 5

Storm 6

Storm 7

Pesticide application

Storm 2

Storm 1

Storm 3

Storm 4 Storm 5

Storm 6

Storm 7

Pesticide application

Pesticide application

Figure 11. Relation of selected pesticide concentrations to streamflow for the hydrologic compartments 

sampled in Leary Weber Ditch Basin, Indiana, 2003–04. 

Occurrence of Agricultural Chemicals in Leary Weber Ditch Basin 17
0.1

1

10

100

0.05

300

GLYPHOSATE*

Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 

2003 2004

CONCENTRATION, IN MICROGRAMS PER LITER

STREAMFLOW, IN CUBIC FEET PER SECOND

Glyphosate reporting level 0.1

1

10

100

700

0.04

0.1

1

10

100

0.05

300 CHLORPYRIFOS

Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 

2003 2004

Storm 2

CONCENTRATION, IN MICROGRAMS PER LITER

STREAMFLOW, IN CUBIC FEET PER SECOND

Chlorpyrifos reporting level

0.01

0.1

0.004

0.2

Figure 11. Relation of selected pesticide concentrations to streamflow in rain, overland-flow, tile-drain, and Leary 

Weber Ditch water in Leary Weber Ditch Basin, Indiana, 2003-04.-Continued

EXPLANATION

Streamflow

Leary Weber 

 Ditch water

Overland-

 flow water

Rain

Tile-drain

 water

Storm 1

Storm 3

Storm 4

Storm 5

Storm 6

Storm 7

Storm 2

Pesticide application

Pesticide application

Storm 1

Storm 3

Storm 4

Storm 5

Storm 6

Pesticide application

Pesticide application

Storm 7

*Glyphosate not analyzed in 2003

Figure 11. Relation of selected pesticide concentrations to streamflow for the hydrologic compartments 

sampled in Leary Weber Ditch Basin, Indiana, 2003–04.—Continued 

18  Occurrence and Transport of Agricultural Chemicals in Leary Weber Ditch Basin, Hancock County, Indiana, 2003–04
0.1

1

NITRATE PLUS NITRITE (N)

Figure 12. Distribution of nutrient concentrations in Leary Weber Ditch and in each hydrologic compartment 

sampled in Leary Weber Ditch Basin, Indiana, 2003-04.

10

0.1

1

0.01

ORTHOPHOSPHATE (P)

x o

x

x

x

x

oo

11 22 13 6 42 14 61

TOTAL NITROGEN

0.1

1

10

CONCENTRATION,

IN MILLIGRAMS PER LITER

0.001

CONCENTRATION,

IN MILLIGRAMS PER LITER

0.05

15

CONCENTRATION,

IN MILLIGRAMS PER LITER

15

0.05

xx

x

o

xx

o

x x

x

x

x

o

o

22 13 6 42 14 61

x

xx

o

o xx

22 13 6 42 14 61

22

x

x

o

o

EXPLANATION

Number of values

Upper detached

Upper outside

Upper adjacent

75th percentile

Median

25th percentile

Lower adjacent

Lower outside

Lower detached

Ground

water

Tiledrain

water

Overlandflow

water

Leary

Weber

Ditch Unsaturated

water soil water

Saturated

soil water

Rain

Ground

water

Tiledrain

water

Overlandflow

water

Leary

Weber

Ditch Unsaturated

water soil water

Saturated

soil water

Rain

Ground

water

Tiledrain

water

Overlandflow

water

Leary

Weber

Ditch

water

RainNot analyzed in rain Not analyzed in rain

Unsaturated

soil water

Saturated

soil water

Figure 12. Distribution of nutrient concentrations in Leary Weber Ditch and in each hydrologic 

compartment sampled in Leary Weber Ditch Basin, Indiana, 2003–04. 

Occurrence of Agricultural Chemicals in Leary Weber Ditch Basin 19
0.005

0.009

0.013

0.017

2 4 6 8 >9

DEPTH BELOW LAND SURFACE, IN FEET

0.00

0.10

0.20

0.25

CONCENTRATION,

IN MICROGRAMS PER LITER

0.10

0.11

0.12

0.13

0.14

Reporting level

ATRAZINE

ACETOCHLOR

GLYPHOSATE

Figure 13. Concentration of selected pesticide parents 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.

3 5 7

2

0

0

0

6

2

0

0

7

1

1

0

7

0

0

0

2

4

2

0

0

0

1

0

0

0

0

4

NUMBER OF SAMPLES

0.05

0.15

2 4 6 8 >9

DEPTH BELOW LAND SURFACE, IN FEET

3 5 7

0.021

2

0

0

0

5

2

0

0

5

0

1

0

5

0

0

0

1

3

2

0

0

0

1

0

0

0

0

4

NUMBER OF SAMPLES CONCENTRATION, IN MICROGRAMS PER LITER

Reporting level

2

0

0

0

4

2

0

0

5

0

1

0

6

0

0

0

1

4

2

0

0

0

1

0

0

0

0

2

NUMBER OF SAMPLES

Reporting level

2 4 6 8 >9

DEPTH BELOW LAND SURFACE, IN FEET

3 5 7

CONCENTRATION,

IN MICROGRAMS PER LITER

EXPLANATION

Saturated soil water

 (lysimeter)

Saturated soil water (well)

Ground water (well)

Unsaturated soil water

 (lysimeter)

Figure 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. 

20 Occurrence and Transport of Agricultural Chemicals in Leary Weber Ditch Basin, Hancock County, Indiana, 2003–04
0.0

0.4

0.8

1.2

0.00

0.05

0.10

0.15

0.10

0.15

0.20

0.25

0.30

DEETHYLATRAZINE

ACETOCHLOR ESA

AMPA

0.20

2

0

0

0

6

2

0

0

7

1

1

0

7

0

0

0

2

4

2

0

0

0

1

0

0

0

0

4

NUMBER OF SAMPLES

2 4 6 8 >9

DEPTH BELOW LAND SURFACE, IN FEET

3 5 7

Reporting level

CONCENTRATION,

IN MICROGRAMS PER LITER

2 4 6 8 >9

DEPTH BELOW LAND SURFACE, IN FEET

3 5 7

CONCENTRATION,

IN MICROGRAMS PER LITER

2

0

0

0

5

2

0

0

6

1

1

0

7

0

0

0

1

4

2

0

0

0

1

0

0

0

0

4

NUMBER OF SAMPLES

Reporting level

2

0

0

0

5

3

0

0

6

0

1

0

7

0

0

0

1

4

2

0

0

0

1

0

0

0

0

4

NUMBER OF SAMPLES CONCENTRATION, IN MICROGRAMS PER LITER

2 4 6 8 >9

DEPTH BELOW LAND SURFACE, IN FEET

3 5 7

Reporting level

Figure 13. Concentration of selected pesticide parents 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.-Continued

EXPLANATION

Saturated soil water

 (lysimeter)

Saturated soil water (well)

Ground water (well)

Unsaturated soil water

 (lysimeter)

Figure 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. —Continued

Occurrence of Agricultural Chemicals in Leary Weber Ditch Basin 21
Atrazine and deethylatrazine were detected in all soil-water 

well samples (fig. 13). Glyphosate was detected in one sample 

from the deep (6 ft) lysimeter and one sample from the 

6-ft-deep well at the South site under saturated conditions; it 

was not detected in other lysimeter or well samples (fig. 13). 

This presence was likely a result of the rapid transformation 

of glyphosate to AMPA and the strong adsorption of glyphosate on the soil matrix (Vereecken, 2005). AMPA was in the 

2-, 4-, 5-, and 6-ft lysimeters under saturated and unsaturated 

conditions. The highest AMPA concentrations were in the 

6-ft lysimeter samples from the South site under saturated 

conditions. The frequency and number of samples collected 

from the soil-water hydrologic compartment were not large 

enough to determine if a corresponding rise in the concentrations of pesticides in this hydrologic compartment was a result 

of increased amounts of rainfall.

Nitrate was detected in samples collected from nearly 

every lysimeter and soil-water well in 2004 (Baker and 

Lathrop, 2006). Nitrate concentrations in lysimeter samples 

collected under unsaturated conditions were significantly different (Wilcoxon rank-sum p-values < 0.01) than in samples 

collected under saturated conditions. Nitrate concentrations 

were higher in samples collected under unsaturated conditions 

than in those collected under saturated conditions (fig. 14). 

Orthophosphate concentrations were low in unsaturated and 

saturated soil-water samples (fig. 12). The major-ion chemistry of saturated soil-water samples showed a slightly different 

chemical signature than that of unsaturated soil-water samples 

(fig. 15A). A higher percentage of sulfate ions generally was 

detected in unsaturated soil-water samples than saturated soilwater samples. The concentrations of calcium, magnesium, 

potassium, and sulfate in saturated soil-water samples differ 

significantly (Wilcoxon rank-sum p-values <0.01) from the 

concentrations of these constituents in samples collected from 

Leary Weber Ditch and from the other hydrologic compartments (ground water, tile-drain water, and overland-flow 

water). (Rain water was not analyzed for major-ion chemistry.)

Ground Water

Discrete ground-water samples were collected from wells 

screened deeper than 9 ft below land surface in 2004. Of the 

84 pesticide parent and pesticide degradate compounds for 

which the samples were analyzed, 6 were detected in groundwater samples (table 2, fig. 9). Glyphosate was the only pesticide parent compound in the ground-water samples, and it was 

detected in one of two samples. Alachlor ESA-2nd amide, alachlor OXA, and AMPA were the pesticide degradates detected 

most frequently in ground-water samples (fig. 9).

0.1

1

10

NITRATE PLUS NITRITE (N)

0.02

40

2

0

0

0

6

2

0

0

6

1

1

0

7

0

0

0

1

4

4

0

0

0

1

0

0

0

0

6

NUMBER OF SAMPLES CONCENTRATION, IN MILLIGRAMS PER LITER

2 4 6 8 >9

DEPTH BELOW LAND SURFACE, IN FEET

3 5 7

EXPLANATION

Saturated soil water

 (lysimeter)

Saturated soil water (well)

Ground water (well)

Unsaturated soil water

 (lysimeter)

Figure 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. 

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

Tile-drain waterOverland-flow water

 100

 80

 60

 40

 20

 0 0

 20

 40

 60

 80

 100 0

 20

 40

 60

 80

 100

 0

 20

 40

 60

 80

 100

 100

 80

 60

 40

 20

 0 100

 80

 60

 40

 20

 0

 0

 20

 40

 60

 80

 100

 0

 20

 40

 60

 80

 100 100

 80

 60

 40

 20

 0

 100

 80

 60

 40

 20

 0

EXPLANATION

Figure 15. 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.

A

B

Unsaturated soil waterSaturated soil waterGround water

EXPLANATION

 100

 80

 60

 40

 20

 0 0

 20

 40

 60

 80

 100

 0

 20

 40

 60

 80

 100

 0

 20

 40

 60

 80

 100

 100

 80

 60

 40

 20

 0

 100

 80

 60

 40

 20

 0

 0

 20

 40

 60

 80

 100

 0

 20

 40

 60

 80

 100

 100

 80

 60

 40

 20

 0

 100

 80

 60

 40

 20

 0

Calcium Chloride, Fluoride, Nitrate

Sulfate plus Chloride

Magnesium

Sulfate

Calcium plus Magnesium

Bicarbonate

Sodium plus Potassium

Calcium Chloride, Fluoride, Nitrate

Sulfate plus Chloride

Magnesium

Sulfate

Calcium plus Magnesium

Bicarbonate

Sodium plus Potassium

PERCENTAGE OF TOTAL MILLIEQUIVALENTS PER LITER

Figure 15. 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. 

Occurrence of Agricultural Chemicals in Leary Weber Ditch Basin 23
The few pesticide detections in ground-water samples 

(figs. 9, 10, and 13) probably can be explained by (1) the long 

time required for pesticides to travel from land surface to the 

shallow aquifers, and (2) the tile drains that divert much of the 

pesticides out of the soil-water hydrologic compartment before 

they reach ground water. Water samples were not analyzed for 

age, but the high silt and clay content of the soils suggests low 

hydraulic conductivity in the absence of macropores. Although 

macropores/preferential-flow paths may be present above the 

tile drains (Stone and Wilson, 2006), they likely do not extend 

much below the level of the tile drains. The soils below the 

tile drains more likely are saturated—and for longer periods; 

therefore, there should be fewer worm burrows, roots, and 

desiccation fractures. 

Nitrate was detected in four of six ground-water samples 

collected in 2004 (Baker and Lathrop, 2006). Nitrate concentrations in ground-water samples were significantly different 

(Wilcoxon rank-sum p-values < 0.01)—and lower—than 

concentrations measured in Leary Weber Ditch and in the 

other hydrologic compartment samples, including soil water 

(figs. 12 and 14). Orthophosphate concentrations were significantly different (Wilcoxon rank-sum p-values <0.01)—and 

lower—in ground-water samples than in the other hydrologic compartments (fig. 12). The major-ion chemistry of the 

ground-water samples suggests that the contact time of water 

with soil particles and aquifer substrate is longer than for soil 

water (fig 15A). Sulfate and calcium concentrations were significantly different (Wilcoxon rank-sum p-values <0.01)—and 

higher—for ground-water samples than for saturated-soil 

water samples. 

Tile-Drain Water

In tile-drain samples, 20 pesticides were detected 

(table 2). In general, pesticide parent compounds were 

detected less frequently than their degradates. Pesticide parent 

and pesticide degradate compounds detected in more than 

75 percent of the samples were atrazine (100 percent of the 

samples), deethylatrazine (100 percent), acetochlor/metolachlor ESA-2nd amide (92.9 percent), AMPA (92.9 percent), 

metolachlor (90.3 percent), acetochlor ESA (86.7 percent), 

glyphosate (85.7 percent) and acetochlor OXA (76.7 percent) 

(fig. 9). Atrazine and acetochlor were applied to the field 

above the tile drain in 2003, and glyphosate was applied in 

2004. Glyphosate and AMPA were detected in almost every 

sample collected from the tile-drain in 2004 (figs. 9 and 10). 

Atrazine and glyphosate concentrations were usually higher 

than their degradates in most samples from the tile-drain 

(fig. 10). Concentrations of acetochlor ESA, alachlor ESA, 

and metolachlor ESA were higher than the parent compounds 

in tile-drain samples (fig. 10). The highest glyphosate concentrations (4.7 μg/L) were detected in samples collected near the 

peak tile-drain flow during storms (Stone and Wilson, 2006). 

Atrazine and acetochlor concentrations were higher in 2003 

when these pesticides were applied with the corn crop rotation 

than in 2004 when they were not applied with the soybean 

crop rotation (fig. 10). Atrazine and acetochlor concentrations 

also were higher during storms after pesticide application than 

at other times of the year (fig. 11). Tile-drain samples were not 

collected during most of storm 3 because of equipment failure. 

Storm 3 was the first intense storm following application of 

atrazine to the field; therefore it is likely that the peak tiledrain atrazine concentrations for this storm would have been 

higher than the single sample (0.979 μg/L) collected during 

storm 3 (fig. 11). Acetochlor ESA and metolachlor ESA were 

detected in higher concentrations than the pesticide parent 

compounds (fig. 10). Neither metolachlor nor alachlor were 

applied to the field above the tile drain in 2003 or 2004, indicating a potential carryover from previous years of application, 

drift from an adjacent field, or deposition from rain.

Median nitrate concentrations in tile-drain samples were 

higher than in samples from any other hydrologic compartment (fig. 12). Nitrate concentrations in tile-drain samples 

averaged slightly more than 10 mg/L as N in 2003 and slightly 

less than 10 mg/L as N in 2004 (fig. 16). Trends in nitrate 

concentrations in tile-drain samples were similar to those in 

Leary Weber Ditch; however, nitrate concentrations in tiledrain samples were higher than those in Leary Weber Ditch 

during April and May 2003 and November and December 

2004 (fig. 16). Nitrate concentrations were lower than those in 

Leary Weber Ditch during May and June 2004 (fig. 16). Most 

of the nitrogen in tile-drain samples was in the form of nitrate. 

Anhydrous ammonia was applied to the field above the tile 

drain in 2003; however, it was not applied to that field in 2004. 

Orthophosphate concentrations were low in tile-drain samples, compared to the overland-flow and Leary Weber Ditch 

samples; the median concentration in the tile-drain samples 

was similar to that in soil-water and ground-water samples 

(fig. 12). The major-ion chemistry of tile-drain samples shows 

a distinct chemical profile, compared to overland-flow and 

Leary Weber Ditch samples (fig. 15B). Tile-drain samples 

are primarily calcium-bicarbonate compositions, with significantly different (Wilcoxon rank-sum p-values <0.01) sodium 

and potassium concentrations than overland-flow and Leary 

Weber Ditch samples. Sodium and potassium concentrations 

in tile-drain samples were lower than concentrations in Leary 

Weber Ditch and overland-flow samples.

24 Occurrence and Transport of Agricultural Chemicals in Leary Weber Ditch Basin, Hancock County, Indiana, 2003–04
0.1

1

10

100

0.1

1

10

100

STREAMFLOW, IN CUBIC FEET PER SECOND STREAMFLOW, IN CUBIC FEET PER SECOND

300

0.04

300

0.04

CONCENTRATION, IN MILLIGRAMS PER LITER

Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 

2003 2004

Mar Apr May Jun Jul Aug Sep Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec 

2003 2004

NITRATE

ORTHOPHOSPHATE

CONCENTRATION, IN MILLIGRAMS PER LITER

Figure 16. Relation of selected nutrient concentrations to streamflow in rain, overland-flow, tile-drain, and Leary 

Weber Ditch water in the Leary Weber Ditch Basin, Indiana, 2003-04.

EXPLANATION

Streamflow

Leary Weber 

 Ditch water

Overland-

 flow water

Rain

Tile-drain

 water

0.1

1

10

0.01

30

0.04

0.5

0.005

0.1

Fertililzer application

Fertililzer application

Fertililzer application

Storm 1 Storm 3

Storm 4 Storm 5

Storm 6

Storm 7

Storm 2

Storm 1

Storm 3

Storm 4

Storm 5

Storm 6

Storm 7

Storm 2

Figure 16. Relation of selected nutrient concentrations to streamflow for the hydrologic compartments sampled in the 

Leary Weber Ditch Basin, Indiana, 2003–04. 

Occurrence of Agricultural Chemicals in Leary Weber Ditch Basin 25
Overland-Flow Water

In overland-flow water, 26 pesticide parent and pesticide 

degradate compounds were detected (table 2, fig. 9). Compounds that were detected in more than 75 percent of overland-flow samples were AMPA (100 percent of samples), atrazine (100 percent), chlorpyrifos (100 percent), deethylatrazine 

(100 percent), glyphosate (100 percent), metolachlor (100 percent), acetochlor (85.7 percent), acetochlor sulfynilacetic acid 

(acetochlor SAA) (85.7 percent), and simazine (84.6 percent) 

(fig. 9). Atrazine, acetochlor, and chlorpyrifos were applied to 

the field at the Overland Flow site in 2003; glyphosate was the 

only chemical applied to the Overland Flow site field in 2004. 

Acetochlor, atrazine, and metolachlor were detected in higher 

concentrations than their degradates (fig. 10). Overland-flow 

and rain water were the only two hydrologic compartments 

where pesticide parent compounds were detected more 

frequently than their degradates. Atrazine and glyphosate concentrations were usually higher than their degradates in most 

samples from overland-flow water (fig. 10). The highest atrazine concentration detected in Leary Weber Ditch Basin was 

52.3 μg/L at the Overland Flow site in 2004 (figs. 10 and 11). 

Atrazine was applied at this site in 2003 but not in 2004. Overland-flow samples, however, were not collected in 2003 until 

more than 3 months after atrazine application. Alachlor was 

detected in overland-flow samples during storm 5 (May 2004) 

even though it had not been applied to the contributing field 

during the 2004 season. It also was detected in rain samples 

indicating that rain may be the source of alachlor in overlandflow samples in 2004 (fig. 17). 

Nitrate concentrations in overland-flow samples were significantly different (Wilcoxon rank-sum p-values <0.01) than 

concentrations measured in either rain-water, soil-water, tiledrain water, or Leary Weber Ditch samples. Nitrate concentrations in overland-flow samples were lower than concentrations 

in rain-water, soil-water, tile-drain water, or Leary Weber 

Ditch samples (fig. 12). Anhydrous ammonia was applied to 

the Overland Flow site in 2003 but was injected below the 

surface and was not available for transport in surface runoff; 

therefore, nitrate concentrations remained low in overlandflow water (fig. 16). Orthophosphate concentrations were 

higher in overland-flow samples than in Leary Weber Ditch 

or any other hydrologic compartment (fig. 12). The major-ion 

chemistry of overland-flow samples shows a different chemical signature than tile-drain and Leary Weber Ditch samples 

(fig. 15B). Overland-flow samples reflect the brief contact 

time of the water with the soils, as compared to tile-drain and 

Leary Weber Ditch samples.

Leary Weber Ditch

In Leary Weber Ditch, 34 pesticide parent and pesticide 

degradate compounds were detected (table 2, fig. 9). Atrazine, 

deethylatrazine, metolachlor, and metolachlor ESA, were 

detected in every Leary Weber Ditch sample (fig. 9). Tebuthiuron, a broad-spectrum herbicide for non-cropland application, 

such as clearing roadsides and rights of way, was detected in 

the ditch water but not in any other hydrologic compartment. 

Atrazine and glyphosate concentrations were higher than their 

degradates; however, acetochlor, alachlor, and metolachlor 

0

0.005

0.01

0.015

0.02

0.025

0.03

0.035

4/27 5/4 5/12 5/18 5/25 6/1

CONCENTRATION,

IN MICROGRAMS PER LITER

Overland flow

Rain (weekly composite)

2004

Reporting level

ALACHLOR

STORM 5

Figure 17. Comparison of alachlor concentrations measured in rain and overland-flow water during storm 5 in 

Leary Weber Ditch Basin, Indiana, 2004. 

26  Occurrence and Transport of Agricultural Chemicals in Leary Weber Ditch Basin, Hancock County, Indiana, 2003–04
concentrations were lower than their degradates (fig. 10). For 

atrazine, these concentrations were likely a result of its greater 

persistence in the environment than acetochlor, alachlor, or 

metolachlor (Boxall and others, 2004; Kalkhoff and others, 2003). It is possible that glyphosate concentrations were 

higher than AMPA concentrations for most Leary Weber Ditch 

samples because glyphosate often is used to control weeds 

on fields as well as fence-row weed control and other noncropped field areas throughout the growing season (Battaglin 

and others, 2005). Glyphosate also tends to persist in the soil 

and is mobilized during rainfall in overland flow or preferential flow to tile drains and consequently into Leary Weber 

Ditch. The highest pesticide concentrations in Leary Weber 

Ditch samples coincide with high streamflow after pesticide 

application (fig. 11).

Nitrate concentrations in Leary Weber Ditch samples 

were similar to those in tile-drain samples (fig. 12). Seasonal 

trends in the Leary Weber Ditch samples showed that nitrate 

concentrations were higher during May, June, November, and 

December 2004, with the highest concentrations in April 2003 

and May and June of both years (with the exception of one 

sample in July) (fig. 16). Lower nitrate concentrations were 

detected in August and September 2003. Leary Weber Ditch 

was not sampled in January, February, or October of both 

years. For most months, the concentrations of nitrate are stable 

through various rates of flow; however, in samples collected 

in May (both years) nitrate concentrations were higher when 

flows were higher. This difference is likely a result of the 

application of nitrogen fertilizer during May, which increases 

the available nitrogen pool for transport. Most of the nitrogen 

in Leary Weber Ditch water is from nitrate. Orthophosphate 

concentrations in Leary Weber Ditch samples were significantly different (Wilcoxon rank-sum p-values <0.01) from 

concentrations in tile-drain, ground-water, and overland-flow 

water samples. Orthophosphate concentrations in Leary Weber 

Ditch samples were higher than those detected in tile-drain 

water and ground-water samples and lower than concentrations detected in overland-flow water samples (fig. 12). Majorion chemistry of Leary Weber Ditch samples falls between 

the two primary sources of water to the ditch, tile drains and 

overland flow (fig. 15B).

Transport of Agricultural Chemicals in 

Leary Weber Ditch Basin

Rain water, overland-flow water, soil water, tile-drain 

water, and ground water are the major hydrologic compartments that potentially contribute water and agricultural chemicals to Leary Weber Ditch. On the basis of the concentrations 

of chemicals present within each hydrologic compartment, it is 

possible to infer transport routes of these chemicals into Leary 

Weber Ditch. The length of time water stays in each compartment and the number of possible sources contributing water to 

Leary Weber Ditch ultimately influence the chemical composition of the stream water. Chemicals may be transported 

quickly from the land surface in overland flow; they may 

volatilize, accumulate, or degrade; or they may adsorb onto 

soil particles as they travel through the soils into tile drains or 

into ground water.

Direct rainfall or air deposition of particulate matter is 

not an important source of water or chemicals to ditch. The 

surface area of the Leary Weber Ditch channel is only about 

0.1 percent of the total area of the basin; therefore, the volume 

of rain falling directly on the channel is small relative to the 

volume of rain that falls throughout the basin. Median concentrations of pesticides in rain samples were lower than median 

concentrations in Leary Weber Ditch, tile-drain, and overlandflow samples (fig. 10). Exceptions to this are the concentrations in rain and overland-flow samples of chemicals that were 

not applied to the overland-flow field. Alachlor was detected 

in rain and overland-flow samples during storm 5 (May 2004), 

even though alachlor was not applied to the overland-flow 

field in 2003 or 2004 (fig. 17). The higher alachlor concentration in overland-flow samples from storm 5, compared to concentrations for the other storms, appears to be a direct result 

of higher alachlor concentrations in the rain during storm 5 

(fig. 17).

Just as the rain and overland-flow compartments are 

linked, so too are the soil-water and tile-drain water compartments (tile drains discharge soil water to Leary Weber Ditch). 

As mentioned earlier in this report, the soil-water hydrologic 

compartment resembles the tile-drain compartment in terms of 

major-ion chemistry (fig. 15). In terms of water and chemical 

transport to Leary Weber Ditch, the contributions from the 

soil-water compartment are included in the discussion of tiledrain contributions.

Ground-water discharge is not a significant source of flow 

or chemicals to Leary Weber Ditch. The ditch is ephemeral 

and does not receive ground-water discharge during sustained 

dry periods. Field reconnaissance shows that the ditch stops 

flowing when the tile drains stop flowing, indicating that the 

tile drains are the primary source of water in the ditch between 

storms. Upstream from the gaging station on Leary Weber 

Ditch, the channel bottom is primarily fine-textured soils 

and clays for most of its length (U.S. Department of Agriculture, 1978). This type of material limits the ground-water 

to surface-water exchange, thereby limiting contributions of 

ground water to the channel. The farm fields also are underlain 

by fine-textured soils. The absence of well-defined layers of 

coarse-grained sediments in the shallow subsurface (between 

land surface and the bottom of Leary Weber Ditch) decreases 

the potential for lateral flow of soil water and ground water 

to the ditch. The lateral movement of water through soils is 

short-circuited by soil water discharging to the ditch through 

tile drains. Also, the tile drains lower the shallow water table, 

reducing the hydraulic gradient needed to discharge ground 

water to the ditch. Chemically, the ionic composition of water 

in wells deeper than 9 ft is different than water in the shallow wells, water in tile drains, and the water in Leary Weber 

Ditch (fig. 15). On the basis of (1) the lack of a sustained base 

Transport of Agricultural Chemicals in Leary Weber Ditch Basin 27
flow in Leary Weber Ditch, (2) the fine-grained materials that 

limit ground-water and surface-water interaction, and (3) the 

differences between ionic composition in ground water, tiledrain water, and Leary Weber Ditch water, ground water is not 

considered to be a significant source of water and agricultural 

chemicals to Leary Weber Ditch. 

Overland flow and tile drains contribute most of the water 

and chemicals to Leary Weber Ditch. During storms, overland 

flow and tile drains contribute water to the ditch. Between 

storms, tile drains flow until all of the available water in the 

soils above the tile drains is removed. The amount of water 

that passes the Leary Weber Ditch gaging station as a result of 

a storm represents from 13 to 54 percent of the total volume 

of rain that falls in the basin during the storm (table 3). On an 

annual basis, however, the total rainfall is nearly balanced by 

the amount of water flowing through Leary Weber Ditch and 

that lost to evapotranspiration. Therefore, most of the rainfall 

from a storm (46 to 87 percent) is stored in the soil-water 

hydrologic compartment until it is lost through tile drainage, 

evapotranspiration, or recharge to ground water. 

Mixing Analysis

A conservative mixing analysis based on potassium as 

a tracer was used to determine the relative contributions of 

overland flow and tile drains to Leary Weber Ditch during 

seven storms in 2003 and 2004 (fig. 18). Water in Leary Weber 

Ditch and in the tile-drain and overland-flow hydrologic compartments each have different chemical signatures (fig. 15). 

Overland-flow water has a short contact time with surficial 

soils before it flows into Leary Weber Ditch; therefore this 

water has relatively low ionic concentrations and its chemistry 

closely resembles that of rain. The contact time for tile-drain 

water with soils is longer than that of overland flow as it 

travels through the soil-water hydrologic compartment and is 

then routed through the tile drains to the ditch. Comparison of 

the ion chemistry in the samples of tile-drain, overland-flow, 

and Leary Weber Ditch water collected during 2003 and 2004 

shows that the major-ion chemistry of the Leary Weber Ditch 

samples were between those of the tile-drain and overlandflow samples (fig. 15) and is consistent with the theory that 

Leary Weber Ditch water is a combination of water from the 

tile-drain and overland-flow hydrologic compartments.

When the maximum rainfall intensity was 0.5 in/hr or 

lower, overland flow contributed less than 10 percent of the 

Leary Weber Ditch stormflow and tile drains contributed more 

than 90 percent of that flow (storms 1, 2, 5, and 7) (fig. 18). 

The infiltration capacity of the soils was exceeded only 

slightly during these storms because of the light rainfall intensity and the antecedent (pre-storm) soil-moisture conditions. 

When the maximum rainfall intensity was 0.75 in/hr or greater, 

the overland-flow contribution was around 40 percent and the 

tile-drain contribution was around 60 percent of the total flow 

in Leary Weber Ditch (storms 3, 4, and 6) (fig. 18). During 

these storms, the soil-infiltration capacity was exceeded by 

rainfall intensity and near capacity antecedent soil moisture 

conditions. The mixing analysis shows that overland flow 

is an important contributor of water to Leary Weber Ditch 

during periods of high-intensity rainfall and when antecedent 

soil-moisture conditions decrease soil-infiltration capacity. At 

other times, however, tile drains are assumed to be the primary 

contributor of water to Leary Weber Ditch. This understanding 

of which hydrologic compartments contribute water to Leary 

Weber Ditch during different levels of rainfall and streamflow 

facilitates the investigation of chemical transport.

Table 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.

[in., inch; ft, foot; ft3, cubic foot; gage, USGS streamflow-gaging station]

Storm

Total rainfall 

during storm

(in.)

Total rainfall 

during storm 

(ft)

Total rainfall 

over entire basin 

during storm

(thousand ft3)

Total streamflow 

past the gage 

during storm 

(thousand ft3)

Percent 

of rainfall 

flowing past 

the gage 

during storm

1 1.26 0.1053 8,014 2,551 32

2 1.51 .1260 9,590 1,269 13

3 9.38 .7815 59,478 31,398 53

4 5.30 .4419 33,362 8,122 24

5 1.01 .0843 6,416 1,403 22

6 2.26 .1880 14,308 5,409 38

7 2.01 .1673 12,733 6,837 54

28  Occurrence and Transport of Agricultural Chemicals in Leary Weber Ditch Basin, Hancock County, Indiana, 2003–04
0

5

10

15

20

25

30

35

OF = 5 percent

TD = 95 percent

5 6

STORM 1

13

STORM 2

14 15 16 17

May

2003

June

2003

STORM 3

STORM 4

MI = 0.35 inch per hour

OF = <1 percent

TD = >99 percent

0

1

2

3

4

5

6

7

8

0

50

100

150

200

250

5 6 7 8 9

July

2003

10 11 12 13 14 15

1 2

September

2003

3 4

OF = 44 percent

TD = 56 percent

MI = 1.91 inches per hour

Figure 18. Storm hydrographs for U.S. Geological Survey streamflow-gaging station at 

Mohawk, IN (03361078), 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. Relative contributions were estimated using a mixing analysis model 

with potassium as a tracer.

0

10

20

30

40

50

60

70

80

OF = 34 percent

TD = 66 percent

MI = 0.78 inch per hour

OF Overland flow

TD Tile drain

EXPLANATION

STREAMFLOW,

IN CUBIC FEET PER SECOND

STREAMFLOW,

IN CUBIC FEET PER SECOND

STREAMFLOW,

IN CUBIC FEET PER SECOND

STREAMFLOW,

IN CUBIC FEET PER SECOND

MI = 0.40 inch per hour

MI Maximum 1-hour 

 rainfall intensity

Figure 18. Storm hydrographs for U.S. Geological Survey streamflow-gaging station at 

Mohawk, IN (03361638), showing estimated relative contribution of overland flow and tiledrain flow to Leary Weber Ditch and maximum 1-hour rainfall intensity for selected storms, 

2003–04. Relative contributions were estimated using a mixing analysis model with potassium 

as a tracer. 

Transport of Agricultural Chemicals in Leary Weber Ditch Basin 29
STORM 5

19 20 21

May

2004

30 31 1

May

2

June 2004

STORM 6

STORM 7

24 25 26 27 28

2004

29 30 1 2 3 4 5 6

0

2

4

6

8

10

12

14

16

18

OF = 5 percent

TD = 95 percent

MI = 0.45 inch per hour

0

10

20

30

40

50

60

70

80

90

OF = 32 percent

TD = 68 percent

MI = 1.78 inches per hour

0

5

10

15

20

25

30

STREAMFLOW,

IN CUBIC FEET PER SECOND

November December

STREAMFLOW,

IN CUBIC FEET PER SECOND

STREAMFLOW,

IN CUBIC FEET PER SECOND

OF = 4 percent

TD = 96 percent

MI = 0.16 inch per hour

OF Overland flow

TD Tile drain

EXPLANATION

MI Maximum 1-hour 

 rainfall intensity

Figure 18. Storm hydrographs for U.S. Geological Survey streamflow-gaging station 

at Mohawk, IN (03361078), 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. Relative contributions were estimated using a mixing 

analysis model with potassium as a tracer.-Continued

Figure 18. Storm hydrographs for U.S. Geological Survey streamflow-gaging station at 

Mohawk, IN (03361638), showing estimated relative contribution of overland flow and tiledrain flow to Leary Weber Ditch and maximum 1-hour rainfall intensity for selected storms, 

2003–04. Relative contributions were estimated using a mixing analysis model with potassium 

as a tracer.—Continued

30 Occurrence and Transport of Agricultural Chemicals in Leary Weber Ditch Basin, Hancock County, Indiana, 2003–04
Although the total contribution of water to Leary Weber 

Ditch from overland flow on an annual basis is considerably 

smaller than that from the tile drains, overland flow is an 

important source of agricultural chemicals to the ditch. The 

highest concentrations of atrazine and glyphosate measured in 

any hydrologic compartment, including Leary Weber Ditch, 

were in overland-flow samples collected during storm 5 (2004) 

(fig. 11). Glyphosate was the only chemical applied to the field 

draining the overland-flow site in 2004. Atrazine was applied 

to the overland-flow field in 2003. It is possible that the atrazine was in the soil and on the previous season’s corn stubble. 

Glyphosate concentrations in overland-flow samples from 

storm 5 were 300 times greater than glyphosate concentrations in Leary Weber Ditch samples at any time. This suggests 

that the contributions of water to Leary Weber Ditch from 

overland-flow sources during storm 5 were small compared 

to the overall contribution of water from tile drains. Figure 18 

shows that the contributions of overland flow typically reach 

a maximum at or near the time of peak streamflow. Given 

that agricultural-chemical concentrations typically are higher 

in overland-flow water than in tile-drain water (fig. 11), the 

peak percentage contribution of overland flow to Leary Weber 

Ditch should coincide with the peak concentrations of agricultural chemicals measured in the ditch. During some storms, 

the contribution of overland flow was sustained for a longer 

time than during other storms (fig 18). During the storms with 

sustained overland-flow contributions, the concentrations of 

chemicals in the overland flow decrease with time because the 

chemicals available for transport in the surface soils become 

dilute. This, in part, may explain why chemical concentrations 

in Leary Weber Ditch reach maximum values near the peak 

of the hydrograph and then decrease rapidly. The changes in 

chemical concentrations in Leary Weber Ditch water, however, 

also are affected by changes in the tile-drain chemical concentrations.

On an annual basis, tile drains contribute more water to 

Leary Weber Ditch than do any other hydrologic compartment. 

Water reaches tile drains through preferential and displacement flow through the soils (Stone and Wilson, 2006). Preferential flow occurs through macropores in the unsaturated zone 

and provides a route for water and solutes to bypass the soil 

matrix and reach the tile drains faster than would be expected 

through displacement flow. Displacement flow takes place 

through the pore spaces in the soil matrix. A conservative mixing analysis was used to estimate preferential-flow contributions to a tile drain during two storms in May 2004 (storms 5 

and 6). Preferential flow contributed 11 percent and 51 percent 

of total storm tile-drain flow in storms 5 and 6, respectively 

(Stone and Wilson, 2006). Most of the chemical transport in 

the tile drains occurs during peak tile-drain flow following 

application of the chemicals. Stone and Wilson (2006) found 

strong positive relations between glyphosate concentrations 

and preferential-flow contributions for the two storms they 

analyzed, and they suggest, as did Kladivko and others (2001), 

that preferential flow is a major chemical transport pathway to 

the tile drain.

Based on the mixing analysis and the comparison of the 

various hydrologic compartments contributing water to Leary 

Weber Ditch, tile drains (and because they are linked inherently, water moving through the soil to the tiles) are likely the 

primary contributors of water and agricultural chemicals to 

Leary Weber Ditch on an annual basis. Overland flow during 

intense rainfall also is an important transport mechanism for 

agricultural chemicals to the ditch. Because overland flow 

occurs sporadically throughout the year, however, the contribution may be diminished in comparison to the large amount 

of tile-drain water that enters Leary Weber Ditch.

Uncertainty in Results of Mixing Analysis

The estimation or modeling of processes in natural 

systems is always attended by some degree of uncertainty, 

because it is impractical, if not impossible, to measure every 

component of those systems. The greatest degree of uncertainty in the mixing analysis described here is in not knowing 

how accurately the chemistry of the water at the Tile Drain 

and Overland Flow sites represents the chemistry of the water 

in other tile drains and at other overland-flow areas in the 

Leary Weber Ditch basin. 

The mixing analysis described in the previous section is 

based on the assumption that it is possible to determine relative contributions of water from different sources - tile drain 

discharge and overland flow - to the flow of Leary Weber 

Ditch on the basis of the concentrations of certain chemical 

constituents in the water from each of those sources (source 

concentrations). The source concentration of potassium used 

to represent the tile-drain discharge to Leary Weber Ditch was 

0.96 mg /L, a value chosen because it represents the median 

concentration of potassium in the ditch at low-flow conditions, 

and field observations indicate that during such conditions the 

water in the ditch consists almost entirely of tile-drain water. 

The median concentration of potassium in Leary Weber Ditch 

itself at low flow should thus be more representative of the 

water in all the tile drains contributing to the ditch than the 

median concentration of potassium measured specifically at 

the Tile Drain site, so that the use of the potassium value in 

the ditch reduces the uncertainty for this part of the mixing 

analysis. 

The source contribution of potassium used to represent the overland-flow contributions to Leary Weber Ditch, 

5.24 mg/L, was the median concentration of potassium for 

samples collected at the Overland Flow site. To reduce the 

uncertainty in this part of the mixing analysis, several conditions and possibilities must be considered. Potash (muriate 

of potash, KCl), which is applied as a soil amendment to the 

fields in the fall, is the primary source of potassium in overland flow. Typically, potash is applied every other year, and the 

amount applied is based on the results of soil testing. Potassium concentrations in runoff in other overland-flow areas 

may be higher than those at the Overland Flow site because of 

the recent application of potash; conversely, the concentrations 

Transport of Agricultural Chemicals in Leary Weber Ditch Basin 31
of potassium in the other overland-flow areas may be lower 

than those at the Overland Flow site if potash has not been 

applied recently. Potash was applied to the Overland Flow site 

in 2002; however, the concentrations of potassium in runoff 

during the 2003 growing season do not appear to be any higher 

than those for the 2004 growing season. 

To “test” the reliability of the assumption in the mixing 

analysis—that the concentration of potassium at the Overland 

Flow site was representative of the concentration of potassium 

for all overland-flow contributions to Leary Weber Ditch—and 

to further reduce the uncertainty of the analysis, two “scenarios” were considered: (1) that the concentrations of potassium in runoff at the Overland Flow site are higher than those 

(concentrations) in runoff from other overland-flow areas, and 

(2) that the potassium concentrations in runoff at the Overland 

Flow site are lower than those in runoff from the other areas. 

Potassium concentrations in Leary Weber Ditch samples 

are used as a guide in evaluating whether the potassium 

concentrations are higher in runoff from the Overland Flow 

site than from the majority of other overland-flow areas in the 

basin (scenario 1). The highest observed potassium concentration in Leary Weber Ditch samples was 4.85 mg/L. The 

potassium concentration used to represent overland flow in 

this scenario was 5.24 mg/L. It is unlikely that the contribution 

from the majority of overland-flow areas in the basin was less 

than 5.24 mg/L, because this would imply that during some 

storms the origin of the flow in Leary Weber Ditch would have 

been nearly 100 percent overland flow (tile-drain source concentration used in the median mixing analysis was 0.96 mg/L). 

Overland flow of nearly 100 percent has not been observed 

during field activities and appears unlikely, given the extensive tile-drain network (fig. 2) in the basin and the presence of 

berms bordering the Leary Weber Ditch channel. Therefore, 

scenario 1 is unlikely to occur and the potassium concentration 

of 5.24 mg/L is adequate to use in the mixing analysis for this 

study. 

If potassium concentrations in runoff from the Overland 

Flow site are lower than those in runoff from the majority of 

other overland-flow areas in the basin (scenario 2), then the 

mixing analysis can be based on a higher potassium concentration to represent this condition. The highest observed potassium concentration at the Overland Flow site, 9.65 mg/L, was 

used as the source concentration in scenario 2. The results of a 

scenario 2 analysis (table 4) compared to the mixing analysis 

used in this report show that the overland-flow contribution 

decreased by approximately 50 percent for all storms. An 

exception is the absence of overland flow during the storm of 

June 13, 2003 (verified through field observations).

This comparison shows that the mixing analysis used 

here may overestimate overland-flow contributions by a factor 

of two. On the basis of field observations, it is unlikely that the 

mixing analysis overestimates overland-flow contributions to 

Leary Weber Ditch by a factor of two.

Comparison of the two scenarios to field observations 

from the Overland Flow site and the basin as a whole support 

the mixing analysis used in this report. The mixing analysis 

results coupled with data from the Overland Flow site, may be 

representative of the average condition of the other overlandflow areas in the basin in terms of potassium concentration in 

runoff.

Table 4. Estimates of overland flow contributions to Leary Weber Ditch, Indiana, for selected storms, 

2003–04. 

Mixing analysis Scenario 2*

Storm Date

Estimated 

overland flow 

(percent) 

Estimated 

overland flow 

(percent)

Percent 

difference

1 May 5,2003 4.7 2.3 -51.1

2 June 13, 2003 .3 .3 .0

3 July 5, 2003 43.8 21.7 -50.5

4 September 9, 2003 33.9 16.9 -50.1

5 May 19, 2004 5.0 2.5 -50.0

6 May 30, 2004 32.4 16.0 -50.6

7 November 24, 2004 3.5 1.7 -51.4

*

A sensitivity analysis test case in which concentrations of potassium in runoff are lower at the Overland Flow site 

than at most of the other overland flow areas in the basin.

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

Leary Weber Ditch Basin is one of seven basins investigated in a nationwide study 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. Hydrologic 

compartments that contribute water and agricultural chemicals 

to Leary Weber Ditch are rain water, overland-flow water, soil 

water, tile-drain water, and ground water. Samples were collected from the Tile Drain, Overland Flow, and Leary Weber 

Ditch sites during four storms in 2003 and three storms in 

2004. Stable-flow samples were collected between storms at 

the Tile Drain and Leary Weber Ditch sites. Weekly composite rain samples were collected for 13 weeks in 2003 and 

2004. Soil-water and ground-water samples were collected at 

select times during 2003 and 2004. Samples were analyzed for 

selected pesticides, nutrients, and major ions. 

Agricultural chemicals were detected in Leary Weber 

Ditch and in every associated hydrologic compartment 

sampled during 2003 and 2004. Pesticide parent compounds 

and pesticide degradates were detected more frequently in 

overland-flow and Leary Weber Ditch samples and less frequently in ground-water samples. Concentrations of pesticide 

parent compounds were generally higher than concentrations 

of pesticide degradates in rain samples and lower than the 

concentrations of the degradates in soil-water and groundwater samples. Atrazine and glyphosate concentrations were 

usually higher than their degradates in most samples from rain 

water, tile-drain water, overland-flow water, and Leary Weber 

Ditch water. Soil-water AMPA concentrations were higher 

than glyphosate concentrations. Concentrations of acetochlor 

ESA, alachlor ESA, and metolachlor ESA were higher than 

their parent compounds in soil-water, tile-drain water and 

Leary Weber Ditch water. The lowest concentrations of pesticides and nutrients were in rain, deep lysimeter, and deep well 

samples. The highest concentrations of pesticides and nutrients were in tile-drain, overland-flow, and Leary Weber Ditch 

samples. High concentrations of pesticides and nutrients in 

overland-flow, tile-drain, and Leary Weber Ditch samples were 

detected soon after application to the fields and coincided with 

rainfall and increased streamflow. Pesticides that were not 

applied in the basin or detected in any other hydrologic compartment were detected in several rain samples. The major-ion 

chemistry of samples from the various hydrologic compartments suggests that ground water differs chemically from 

water in Leary Weber Ditch and from the soil-water, overlandflow, and tile-drain hydrologic compartments. In addition, the 

major-ion chemistry shows that Leary Weber Ditch, tile-drain, 

and overland-flow samples are chemically different and that 

Leary Weber Ditch water is primarily a mixture of overlandflow and tile-drain water.

A conservative mixing analysis, based on potassium 

as a tracer, was used to determine relative contributions of 

overland flow and tile-drain discharge to Leary Weber Ditch 

during seven storms in 2003 and 2004. Results of the mixing analysis suggests that overland flow may be a significant 

contributor of water to Leary Weber Ditch during periods of 

high-intensity rainfall and when soil conditions favor surface 

runoff. Tile drains are likely the primary contributor of water 

to Leary Weber Ditch at other times. When maximum rainfall 

intensity was 0.5 in/hr or lower, overland flow and tile drains 

were estimated to contribute about 10 percent and 90 percent, 

respectively, of the storm flow to Leary Weber Ditch. When 

maximum rainfall intensity was 0.75 in/hr or greater, overland 

flow and tile drains were estimated to contribute about 40 percent and 60 percent respectively of the storm flow to the ditch.

Overland flow is an important agricultural chemical 

transport pathway during high-intensity rainfall; however, 

storms with high-intensity rainfall are sporadic throughout the 

year. During most storms and between storms, tile drains are 

the most important contributors for the movement of agricultural chemicals to Leary Weber Ditch. Based on the hydrologic contributions of overland flow water and tile drain water 

to Leary Weber Ditch, tile drains are the primary agriculturalchemical transport mechanism to Leary Weber Ditch. 

Acknowledgments

This project would not have been possible without the 

cooperation of private landowners, Kenny and Jeff Phares, 

who allowed the U.S. Geological Survey to install equipment in or near their farm fields. The collection and analysis 

of water samples for glyphosate was made possible through 

the cooperation of the Toxic Substances Hydrology Program 

and the Organic Geochemistry Research Laboratory of the 

U.S. Geological Survey. Technical reviews were provided by 

Dana Kolpin and Joseph Fenelon, USGS.

References Cited

American Public Health Association, 1998, Standard methods 

for the examination of water and wastewater (20th ed.): 

Washington, D.C., American Public Health Association, 

American Water Works Association, and Water Environment Federation, Section 3, p. 37–43.

Baker, N.T., and Lathrop, T.R., 2006, Agricultural chemicals 

in Leary Weber Ditch Basin, Hancock County, Indiana, 

2003–04: U.S. Geological Survey Digital Data Series 214, 

at http://pubs.usgs.gov/ds/2006/214/.

Battaglin, W.A., Kolpin, D.A., Scribner, E.A., Kuivila, K.M., 

and Sandstrom, M.W., 2005, Glyphosate, other herbicides, 

and transformation products in midwestern streams, 2002: 

Journal of the American Water Resources Association 

41(2), p. 323–332.

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Boxall, A.B.A., Sinclair, C.J., Kolpin, D., and Maund, S.J., 

2004, When synthetic chemicals degrade in the environment—What are the absolute fate, effects, and potential 

risks to humans and the ecosystem?: Environmental Science 

and Technology, v. 38, no. 19, p. 368A–375A.

Capel, P.D., Hamilton, P.A., Erwin, M.L., 2004, Studies by the 

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agricultural chemicals: U.S. Geological Survey Fact Sheet 

2004–3098, accessed December 15, 2005, at http://pubs.

usgs.gov/fs/2004/3098/. 

Fishman, M.J., ed. 1993, Methods of analysis by the U.S. Geological Survey National Water Quality Laboratory—Determination of inorganic and organic constituents in water and 

fluvial sediments: U.S. Geological Survey Open-File Report 

93–125, 217 p.

Fishman, M.J., and Friedman, L.C., 1989, Methods for determination of inorganic substances in water and fluvial sediments: Techniques of Water-Resources Investigations of the 

United States Geological Survey, book 5, chap. A1, 545 p.

Helsel, D.R., and Hirsch, R.M., 1992, Statistical methods in 

water resources: Amsterdam, Elsevier Science Publishers, 

522 p.

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products in upper Midwest agricultural streams during 

August base-flow conditions: Journal of Environmental 

Quality 32, p. 1,025–1,035.

Kladivko, E.J., Brown, L.C., and Baker, J.L., 2001, Pesticide 

transport to subsurface tile drains in humid regions of North 

America: Critical Reviews in Environmental Science and 

Technology, v. 31, issue 1, p. 1–62.

Koterba, M.T., Wilde, F.D., and Lapham, W.W., 1995, 

Ground-water data-collection protocols and procedures for 

the National Water-Quality Assessment Program—Collection and documentation of water-quality samples and related 

data: U.S. Geological Survey Open-File Report 95-399, 

113 p.

Lathrop, T.R., 2006, Environmental setting of the Sugar 

Creek and Leary Weber Ditch Basins, Indiana, 2002–04: 

U.S. Geological Survey Scientific Investigations Report 

2006–5170, 27 p.

Lee, E.A., and Strahan, A.P., 2003, Methods of analysis by the 

U.S. Geological Survey Organic Geochemistry Research 

Group—Determination of acetamide herbicides and their 

degradation products in water using online solid-phase 

extraction and high-performance liquid chromatography/

mass spectrometry: U.S. Geological Survey Open-File 

Report 03–173, 17 p.

Lee, E.A., Strahan, A.P., and Thurman, E.M., 2002, Methods 

of analysis by the U.S. Geological Survey Organic Geochemistry Research Group—Determination of glyphosate, 

aminomethylphosphonic acid, and glufosinate in water 

using solid-phase extraction and high-performance liquid 

chromatography/mass spectrometry: U.S. Geological Survey Open-File Report 01–454, 13 p.

Mallarino, A.P., 2006, Changing potassium recommendations 

in Iowa and the cornbelt: Paper presented at the Fluid Fertilizer Foundation Forum, February 12–14, 2006, Scottsdale, 

Ariz., 9 p.

Martin, J.D., 2001, Variability of pesticide detections and 

concentrations in field replicate water samples collected for 

the National Water-Quality Assessment Program, 1992–97: 

U.S. Geological Survey Water-Resources Investigations 

Report 01–4178, 84 p.

Mueller, D.K., Martin, J.D., and Lopes, T.J., 1997, Qualitycontrol design for surface-water sampling in the National 

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Mueller, D.K., and Titus, C.J., 2005, Quality of nutrient data 

from streams and ground water sampled during water years 

1992–2001: U.S. Geological Survey Scientific Investigations Report 2005–5106, 27 p.

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Network, 2005, National Atmospheric Deposition Program monitoring station oh09—2004: accessed January 

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Stone, W.W., and Wilson, J.T., 2006, Preferential flow estimates to an agricultural tile drain with implications for 

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35(5), p. 1,825–1,835.

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County, Indiana: U.S. Department of Agriculture Soil Conservation Service, 60 p.

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United States—History, status, and prospects: U.S. Department of Agriculture Economic Research Service, Washington, D.C., Misc. Pub. No. 1455, 186 p.

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book 9, chaps. A1–A9, available online at http://pubs.water.

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review: Pest Management Science, v. 61, p. 1,139–1,151.

34 Occurrence and Transport of Agricultural Chemicals in Leary Weber Ditch Basin, Hancock County, Indiana, 2003–04
Tables 1 and 2

35
Table 1. Pesticide parent compounds and pesticide degradates analyzed for in water samples from Leary Weber Ditch Basin, 

Indiana, 2003–04. —Continued

[--, samples not analyzed for this compound; NWIS, National Water Information System; MCRL, most common reporting level; μg/L, micrograms per liter]

Pesticide 

compound 

name

Use*

NWIS 

parameter 

code

2003 

MCRL

(μg/L)

2004

MCRL

(μg/L)

1-Naphthol Degradate (Carbaryl) P49295 0.0882 0.0882

2,6-Diethyl analine Degradate (Alachlor) P82660 .006 .006

2-[(2-Ethyl-6-methylphenyl)amino]-

1-propanol

Degradate (Metolachlor) P61615 .1256 .1256

2-Chloro-2,6-diethylacetanilide Degradate (Butenachlor) P61618 .005 .005

2-Ethyl-6-methylaniline Degradate (Metolachlor) P61620 .0045 .0045

3,4-Dichloroaniline Degradate (Diuron) P61625 .0045 .0045

4-Chloro-2-methylphenol Degradate (MCPA) P61633 .0056 .0056

Acetochlor Herbicide P49260 .006 .006

Acetochlor ESA Degradate (Acetochlor) P61029 .05 .02

Acetochlor OXA Degradate (Acetochlor) P61030 .05 .02

Acetochlor SAA Degradate (Acetochlor) P62847 .05 .02

Acetochlor/Metolachlor ESA-2nd 

amide

Degradate (Acetochlor) P62850 .02 .02

Alachlor Herbicide P46342 .0045 .005

Alachlor ESA Degradate (Alachlor) P50009 .05 .02

Alachlor ESA-2nd amide Degradate (Alachlor) P62849 .02 .02

Alachlor OXA Degradate (Alachlor) P61031 .05 .02

Alachlor SAA Degradate (Alachlor) P62848 .05 .02

Aminomethylphosphonic acid Degradate (Glyphosate) P62649 -- .10

Atrazine Herbicide P39632 .007 .007

Azinphos-methyl Insecticide P82686 .05 .05

Azinphos-methyl oxon Degradate (Azinphos-methyl) P61635 .07 .07

Benfluralin Herbicide P82673 .01 .01

Carbaryl Insecticide P82680 .041 .041

Chlorpyrifos Insecticide P38933 .005 .005

Chlorpyrifos oxygen analog Degradate (Chlorpyrifos) P61636 .0562 .0562

Cyfluthrin Insecticide P61585 .008 .008

Cypermethrin Insecticide P61586 .0086 .0086

Dacthal Herbicide P82682 .003 .003

Deethylatrazine Degradate (Atrazine) P04040 .006 .006

36  Occurrence and Transport of Agricultural Chemicals in Leary Weber Ditch Basin, Hancock County, Indiana, 2003–04
Table 1. Pesticide parent compounds and pesticide degradates analyzed for in water samples from Leary Weber Ditch Basin, 

Indiana, 2003–04. —Continued

[--, samples not analyzed for this compound; NWIS, National Water Information System; MCRL, most common reporting level; μg/L, micrograms per liter]

Pesticide 

compound 

name

Use*

NWIS 

parameter 

code

2003 

MCRL

(μg/L)

2004

MCRL

(μg/L)

Desulfinyl fipronil Degradate (Fipronil) P62170 0.004 0.012

Desulfinyl fipronil amide Degradate (Fipronil) P62169 .009 .029

Diazinon Insecticide P39572 .005 .005

Diazoxon Insecticide P61638 .01 .01

Dichlorvos Insecticide P38775 .0118 .0118

Dicrotophos Insecticide P38454 .0843 .0843

Dimethenamid Herbicide P61588 .02 .02

Dimethenamid ESA Degradate (Dimethenamid) P61951 .05 .02

Dimethenamid OXA Degradate (Dimethenamid) P62482 .05 .02

Dimethoate Insecticide P82662 .0061 .0061

Ethion Insecticide P82346 .004 .004

Ethion monoxon Degradate (Ethion) P61644 .0336 .0336

Fenamiphos Insecticide P61591 .029 .029

Fenamiphos sulfone Degradate (Fenamiphos) P61645 .0077 .007

Fenamiphos sulfoxide Degradate (Fenamiphos) P61646 .031 .031

Fipronil Insecticide P62166 .007 .016

Fipronil sulfide Degradate (Fipronil) P62167 .005 .013

Fipronil sulfone Degradate (Fipronil) P62168 .005 .024

Flufenacet Herbicide P62481 .02 .02

Flufenacet ESA Degradate (Flufenacet) P61952 .05 .02

Flufenacet OXA Degradate (Flufenacet) P62483 .05 .02

Fonofos Insecticide P04095 .0027 .003

Fonofos oxygen analog Degradate (Fonofos) P61649 .0021 .0021

Glyphosate Herbicide P62722 -- .10

Iprodione Fungicide P61593 1.42 1.4223

Isofenphos Insecticide P61594 .0034 .0034

Malaoxon Degradate (Malathion) P61652 .008 .008

Malathion Insecticide P39532 .027 .027

Metalaxyl Fungicide P61596 .0051 .0051

Methidathion Insecticide P61598 .0058 .0058

Table 1 37
Table 1. Pesticide parent compounds and pesticide degradates analyzed for in water samples from Leary Weber Ditch Basin, 

Indiana, 2003–04. —Continued

[--, samples not analyzed for this compound; NWIS, National Water Information System; MCRL, most common reporting level; μg/L, micrograms per liter]

Pesticide 

compound 

name

Use*

NWIS 

parameter 

code

2003 

MCRL

(μg/L)

2004

MCRL

(μg/L)

Methyl parathion Insecticide P82667 0.006 0.015

Methyl-paraoxon Degradate (Methyl parathion) P61664 .0299 .0299

Metolachlor Herbicide P39415 .013 .013

Metolachlor ESA Degradate (Metolachlor) P61043 .05 .02

Metolachlor OXA Degradate (Metolachlor) P61044 .05 .02

Metribuzin Herbicide P82630 .006 .006

Myclobutanil Fungicide P61599 .008 .008

Pendimethalin Herbicide P82683 .022 .022

Permethrin-cis Insecticide P82687 .006 .006

Phorate Insecticide P82664 .011 .011

Phorate oxon Degradate (Phorate) P61666 .0973 .0973

Phosmet Insecticide P61601 .0079 .0079

Phosmet oxon Degradate (Phosmet) P61668 .0553 .0553

Prometon Herbicide P04037 .015 .005

Prometryn Herbicide P04036 .0054 .0054

Pronamide Herbicide P82676 .0041 .004

Propachlor Herbicide P04024 .01 .025

Propachlor ESA Degradate (Propachlor) P62766 .05 .05

Propachlor OXA Degradate (Propachlor) P62767 .05 .02

Simazine Herbicide P04035 .005 .005

Tebuthiuron Herbicide P82670 .016 .016

Terbofos Insecticide P82675 .017 .017

Terbufos-O-analogue sulfone Degradate (Terbofos) P61674 .0676 .0676

Terbuthylazine Herbicide P04022 .0102 .0102

Trifluralin Herbicide P82661 .009 .009

*

For pesticide degradates refer to parent compound (in parenthesis) to determine use of pesticide. 

38  Occurrence and Transport of Agricultural Chemicals in Leary Weber Ditch Basin, Hancock County, Indiana, 2003–04
Table 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. —Continued

Rain Overland-flow water

Compound

Number of

samples

Number of 

detections

Frequency of

detections

Number of

samples

Number of 

detections

Frequency of

detections

1-Naphthol 25 4 16.0 12 0 0.02-Ethyl-6-methylaniline 26 0 0.0 14 0 0.03,4-Dichloroaniline 

(Diuron daugther)

26 0 0.0 14 0 0.0

4-Chloro-2-methylphenol (MCPA daugther) 25 0 0.0 12 0 0.0Acetochlor 26 21 80.8 14 12 85.7Acetochlor ESA 23 1 4.3 14 9 64.3Acetochlor OXA 23 0 0.0 14 8 57.1Acetochlor SAA 23 0 0.0 14 12 85.7Acetochlor/Metolachlor 

ESA-2nd amide 

12 0 0.0 12 1 8.3

Alachlor 26 15 57.7 14 7 50.0Alachlor ESA 23 1 4.3 14 8 57.1Alachlor ESA-2nd 

amide 

12 0 0.0 12 0 0.0

Alachlor OXA 23 0 0.0 14 6 42.9Alachlor SAA 23 0 0.0 14 2 14.3Atrazine 26 22 84.6 14 14 100.0Azinphos-methyl 26 4 15.4 14 0 0.0Carbaryl 26 6 23.1 14 0 0.0Chlorpyrifos 26 14 53.8 14 14 100.0Chlorpyrifos_ oxygen_ 

analog

26 2 7.7 14 0 0.0

Dacthal 26 8 30.8 14 3 21.4Deethylatrazine 26 19 73.1 14 14 100.0Diazinon 26 8 30.8 14 0 0.0Dimethenamid 12 2 16.7 12 6 50.0Dimethenamid ESA 23 0 0.0 14 2 14.3Dimethenamid OXA 23 0 0.0 14 1 7.1Malaoxon 26 8 30.8 14 0 0.0Malathion 26 14 53.8 14 0 0.0Metalaxyl 26 0 0.0 14 0 0.0

Table 2 39
Table 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. —Continued

Rain Overland-flow water

Compound

Number of

samples

Number of 

detections

Frequency of

detections

Number of

samples

Number of 

detections

Frequency of

detections

Methyl parathion 26 13 50.0 14 2 14.3Metolachlor 26 21 80.8 14 14 100.0Metolachlor ESA 23 0 0.0 14 7 50.0Metolachlor OXA 23 0 0.0 14 7 50.0Metribuzin 26 0 0.0 14 0 0.0Pendimethalin 26 8 30.8 14 1 7.1Phosmet 25 5 20.0 14 0 0.0Prometon 26 16 61.5 12 0 0.0Simazine 26 12 46.2 13 11 84.6Tebuthiuron 26 0 0.0 14 0 0.0Terbuthylazine 26 1 3.8 14 6 42.9Trifluralin 26 1 3.8 14 1 7.1Aminomethylphosphonic Acid (AMPA) 12 12 100.0 12 12 100.0Glyphosate 12 11 91.7 12 12 100.0

The following pesticides were not detected at any site:

2,6-Diethyl analine Ethion_ monoxon Methidathion2-[(2-Ethyl-6-methylphenyl) amino]-1-propanol Fenamiphos Methyl- paraoxon2-Chloro-2,6-diethylacet anilide Fenamiphos_ sulfone MyclobutanilAzinphos-methyl oxon Fenamiphos_ sulfoxide Permethrin- cisBenfluralin Fipronil PhorateCyfluthrin Fipronil_ sulfide Phorate_ oxonCypermethrin Fipronil_ sulfone Phosmet_ oxonDesulfinyl fipronil Flufenacet PrometrynDesulfinyl fipronil amide Flufenacet ESA PronamideDiazoxon Flufenacet OXA PropachlorDichlorvos Fonofos Propachlor ESADicrotophos Fonofos_ oxygen_ analog Propachlor OXADimethoate Iprodione TerbofosEthion Isofenphos Terbufos-O-analogue_sulfone

40 Occurrence and Transport of Agricultural Chemicals in Leary Weber Ditch Basin, Hancock County, Indiana, 2003–04
Table 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. —Continued

Soil water Tile-drain water

Compound

Number of

samples

Number of 

detections

Frequency of

detections

Number of

samples

Number of 

detections

Frequency of

detections

1-Naphthol 35 0 0.0 31 0 0.02-Ethyl-6-methylaniline 35 0 0.0 31 8 25.83,4-Dichloroaniline 

(Diuron daugther)

35 0 0.0 31 0 0.0

4-Chloro-2-methylphenol 

(MCPA daugther)

35 0 0.0 31 0 0.0

Acetochlor 27 1 3.7 31 23 74.2Acetochlor ESA 32 32 100.0 30 26 86.7Acetochlor OXA 32 27 84.4 30 23 76.7Acetochlor SAA 32 13 40.6 30 22 73.3Acetochlor/Metolachlor 

ESA-2nd amide 

32 16 50.0 14 13 92.9

Alachlor 16 0 0.0 31 0 0.0Alachlor ESA 32 26 81.3 30 17 56.7Alachlor ESA - 2nd 

amide 

32 3 9.4 14 0 0.0

Alachlor OXA 32 20 62.5 30 12 40.0Alachlor SAA 32 8 25.0 30 6 20.0Atrazine 35 8 22.9 31 31 100.0Azinphos-methyl 35 0 0.0 31 0 0.0Carbaryl 11 0 0.0 31 0 0.0Chlorpyrifos 35 0 0.0 31 8 25.8Chlorpyrifos_ oxygen_ 

analog

35 0 0.0 31 0 0.0

Dacthal 35 1 2.9 31 0 0.0Deethylatrazine 35 9 25.7 31 31 100.0Diazinon 35 3 8.6 31 0 0.0Dimethenamid 32 0 0.0 14 0 0.0Dimethenamid ESA 32 4 12.5 30 0 0.0Dimethenamid OXA 32 1 3.1 30 0 0.0Malaoxon 25 0 0.0 31 0 0.0Malathion 29 0 0.0 31 0 0.0Metalaxyl 35 0 0.0 31 3 9.7

Table 2 41
Table 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. —Continued

Soil water Tile-drain water

Compound

Number of

samples

Number of 

detections

Frequency of

detections

Number of

samples

Number of 

detections

Frequency of

detections

Methyl parathion 25 0 0.0 31 17 54.8Metolachlor 35 4 11.4 31 28 90.3Metolachlor ESA 32 23 71.9 30 20 66.7Metolachlor OXA 32 15 46.9 30 6 20.0Metribuzin 11 0 0.0 31 0 0.0Pendimethalin 30 0 0.0 31 0 0.0Phosmet 23 0 0.0 28 0 0.0Prometon 35 0 0.0 31 0 0.0Simazine 35 0 0.0 31 13 41.9Tebuthiuron 35 0 0.0 31 0 0.0Terbuthylazine 34 0 0.0 31 0 0.0Trifluralin 35 0 0.0 31 0 0.0Aminomethylphosphonic 

Acid (AMPA)

32 23 71.9 14 13 92.9

Glyphosate 28 13 46.4 14 12 85.7

The following pesticides were not detected at any site:

2,6-Diethyl analine Ethion_ monoxon Methidathion2-[(2-Ethyl-6-methylphenyl) amino]-1-propanol Fenamiphos Methyl- paraoxon2-Chloro-2,6-diethylacet anilide Fenamiphos_ sulfone MyclobutanilAzinphos-methyl oxon Fenamiphos_ sulfoxide Permethrin- cis

Benfluralin Fipronil Phorate

Cyfluthrin Fipronil_ sulfide Phorate_ oxonCypermethrin Fipronil_ sulfone Phosmet_ oxon

Desulfinyl fipronil Flufenacet PrometrynDesulfinyl fipronil amide Flufenacet ESA PronamideDiazoxon Flufenacet OXA Propachlor

Dichlorvos Fonofos Propachlor ESA

Dicrotophos Fonofos_ oxygen_ analog Propachlor OXADimethoate Iprodione Terbofos

Ethion Isofenphos Terbufos-O-analogue_sulfone

42 Occurrence and Transport of Agricultural Chemicals in Leary Weber Ditch Basin, Hancock County, Indiana, 2003–04
Table 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. —Continued

Ground water Leary Weber Ditch water

Compound

Number of

samples

Number of 

detections

Frequency of

detections

Number of

samples

Number of 

detections

Frequency of

detections

1-Naphthol 4 0 0.0 47 0 0.02-Ethyl-6-methylaniline 4 0 0.0 48 5 10.43,4-Dichloroaniline 

(Diuron daugther)

4 0 0.0 48 1 2.1

4-Chloro-2-methylphenol (MCPA daugther) 4 0 0.0 47 1 2.1Acetochlor 4 0 0.0 48 44 91.7

Acetochlor ESA 4 1 25.0 47 45 95.7

Acetochlor OXA 4 0 0.0 47 40 85.1Acetochlor SAA 4 0 0.0 47 38 80.9

Acetochlor/Metolachlor 

ESA-2nd amide 

4 0 0.0 18 17 94.4

Alachlor 4 0 0.0 48 7 14.6

Alachlor ESA 4 1 25.0 47 27 57.4

Alachlor ESA-2nd 

amide 

4 2 50.0 18 1 5.6

Alachlor OXA 4 2 50.0 47 19 40.4

Alachlor SAA 4 0 0.0 47 5 10.6Atrazine 4 0 0.0 48 48 100.0

Azinphos-methyl 4 0 0.0 48 0 0.0

Carbaryl 4 0 0.0 49 4 8.2Chlorpyrifos 4 0 0.0 49 26 53.1

Chlorpyrifos_oxygen_

analog

4 0 0.0 48 0 0.0

Dacthal 4 0 0.0 48 0 0.0

Deethylatrazine 4 0 0.0 48 48 100.0

Diazinon 4 0 0.0 49 5 10.2Dimethenamid 4 0 0.0 18 9 50.0

Dimethenamid ESA 4 0 0.0 47 16 34.0

Dimethenamid OXA 4 0 0.0 47 9 19.1Malaoxon 2 0 0.0 48 0 0.0

Malathion 4 0 0.0 48 0 0.0Metalaxyl 3 0 0.0 48 0 0.0

Methyl parathion 4 0 0.0 48 30 62.5

Table 2 43
Table 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. —Continued

Ground water Leary Weber Ditch water

Compound

Number of

samples

Number of 

detections

Frequency of

detections

Number of

samples

Number of 

detections

Frequency of

detections

Metolachlor 4 0 0.0 49 49 100.0Metolachlor ESA 4 0 0.0 47 47 100.0Metolachlor OXA 4 0 0.0 47 44 93.6Metribuzin 4 0 0.0 48 3 6.3Pendimethalin 4 0 0.0 48 4 8.3Phosmet 4 0 0.0 45 0 0.0Prometon 2 0 0.0 49 18 36.7Simazine 4 0 0.0 48 42 87.5Tebuthiuron 4 0 0.0 48 13 27.1Terbuthylazine 4 0 0.0 48 8 16.7Trifluralin 4 0 0.0 48 1 2.1Aminomethylphosphonic Acid (AMPA)

4 2 50.0 19 15 78.9

Glyphosate 2 1 50.0 19 13 68.4

The following pesticides were not detected at any site:

2,6-Diethyl analine Ethion_ monoxon Methidathion2-[(2-Ethyl-6-methylphenyl) amino]-1-propanol Fenamiphos Methyl- paraoxon2-Chloro-2,6-diethylacet anilide Fenamiphos_ sulfone MyclobutanilAzinphos-methyl oxon Fenamiphos_ sulfoxide Permethrin- cisBenfluralin Fipronil PhorateCyfluthrin Fipronil_ sulfide Phorate_ oxonCypermethrin Fipronil_ sulfone Phosmet_ oxonDesulfinyl fipronil Flufenacet PrometrynDesulfinyl fipronil amide Flufenacet ESA PronamideDiazoxon Flufenacet OXA PropachlorDichlorvos Fonofos Propachlor ESADicrotophos Fonofos_ oxygen_ analog Propachlor OXADimethoate Iprodione TerbofosEthion Isofenphos Terbufos-O-analogue_sulfone

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