U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2007–3084

November 2007

Water and Agricultural-Chemical Transport 

in a Midwestern, Tile-Drained Watershed: 

Implications for Conservation Practices

Printed on recycled paper

The study of agricultural chemicals is one of five national priority topics being addressed by the National Water-Quality Assessment 

(NAWQA) Program in its second decade of studies, which began in 2001. Seven watersheds across the Nation were selected for the 

NAWQA agricultural-chemical topical study. The watersheds selected represent a range of agricultural settings—with varying 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). Chemicals selected for study include 

nutrients (nitrogen and phosphorus) and about 50 commonly used pesticides. This study design leads to an improved understanding of 

many factors that can affect the movement of water and chemicals in different agricultural settings. Information from these studies will 

help with decision making related to chemical use, conservation, and other farming practices that are used to reduce runoff of agricultural chemicals and sediment from fields (Capel and others, 2004). This Fact Sheet highlights the results of the NAWQA agricultural 

chemical study in the Leary Weber Ditch Watershed in Hancock County, Indiana. This watershed was selected to represent a tiledrained, corn and soybean, humid area typical in the Midwest. 

Introduction

An understanding of water movement and chemical properties is necessary for understanding how agricultural chemicals 

(nutrients and pesticides) move from the field surface to streams 

and ground water. Effective conservation practices should 

account for the interdependent influences between water movement and chemical properties to reduce agricultural-chemical 

transport to streams and ground water. Environmental managers need to understand that conservation practices designed to 

control agricultural-chemical transport along one pathway, for 

example in runoff, may have an undesirable effect in controlling 

transport along another pathway, for example through soils. 

Leary Weber Ditch in Hancock County, Indiana (fig. 1) 

was used as a case study to demonstrate the importance of 

understanding water movement in chemical transport to streams 

and ground water in a tile-drained, Midwestern, agricultural 

watershed. Leary Weber Ditch Watershed is typical of many 

areas throughout Indiana and the Midwest in terms of farming 

practices and watershed characteristics. Leary Weber Ditch is 

a 2.73-mi2

, intensively farmed watershed dominated by poorly 

drained soils and a nearly flat land surface (Lathrop, 2006). 

Corn and soybeans are grown on 87 percent of the watershed. 

Growing crops on this land requires lowering the water table 

and removing ponded water by draining the fields through subsurface drains (commonly referred to as tile drains). 

Study Area

Figure 1. Location of Leary Weber Ditch Watershed, Hancock 

County, Ind.

Indiana

Indiana

Hancock County

Leary Weber Ditch 

Watershed

Indianapolis
Water-Transport Pathways

Water enters the Leary Weber Ditch Watershed through 

precipitation (rain and snow); most of the water entering the 

watershed is lost through evaporation and plant uptake (evapotranspiration) (fig. 2). Because the land surface is flat and tile 

drained, most of the excess water (30 percent) moves through 

soils (infiltrates) to tile drains and ground water (fig. 2). In general, tile drains tend to decrease surface runoff while increasing 

infiltration (Kladivko and others, 2001).

Water that infiltrates moves through soils by preferential 

and matrix flow. Preferential flow is water that drains quickly 

through large pores in the soil (such as shrink-swell cracks, 

worm burrows, and root casts). Matrix flow is water that drains 

slowly through small pores between soil particles. Once water 

reaches the tile drain it quickly flows into the ditch. In the Leary 

Weber Ditch Watershed, tile drains typically stop flowing in 

July. Excess water in the soils has drained and crops are mature 

enough to take up most of the moisture provided by rainfall 

(Baker and others, 2006).

Less than 10 percent of water entering the watershed flows 

across the land surface as runoff that flows directly into the 

ditch (fig. 2). Runoff contributes water to the ditch during highintensity rainfall; however, storms with high-intensity rainfall 

are sporadic throughout the year. The total annual contribution 

of water from surface runoff to the ditch is much less than the 

tile-drain contribution (Baker and others, 2006).

Ground water is not a major source of water to Leary 

Weber Ditch (Baker and others, 2006). Field observations show 

that the ditch stops flowing when the tile drains stop flowing, 

indicating that the tile drains are the primary source of water to 

the ditch between storms (Baker and others, 2006). 

?

Field

Ground

Water

Tile

Drain

Precipitation

Leary Weber

Ditch Water

Surface Runoff

Evapotranspiration

(60%)

(< 10%)

(30%)

(< 1%)

(100%)

Figure 2. Water-transport pathways in Leary Weber Ditch 

Watershed, Hancock County, Ind. Numbers in parenthesis are 

relative average yearly transport amounts. Arrow is dashed and 

queried where pathway is uncertain.
Nutrient-Transport Pathways

Nutrients primarily enter the watershed through application of fertilizers to crops (fig. 3). The greatest loss of nitrogen 

applied to crops leaves the watershed through plant uptake and 

harvest; most of the phosphorus applied to crops attaches to 

soil particles and remains in the soil (fig. 3) (Schnepf and Cox, 

2006). 

Much of the nitrogen that is not taken up by plants moves 

through soils (as nitrate) to tile drains which flow to the ditch 

(Baker and others, 2006). Runoff is not the major pathway 

for the movement of nitrate to Leary Weber Ditch; tile drains 

decrease surface runoff losses of nitrate while increasing losses 

through tile-drain water (Kladivko and others, 2001). Also, 

because nitrogen fertilizer may be injected into the soil, the 

direct runoff of nitrate to streams is small and the potential for 

nitrate movement to tile drains is further increased. 

The highest nitrate concentrations in the watershed were 

measured in samples collected from water in the soils (Baker 

and others, 2006). While some nitrate moves directly to tile 

drains, excess nitrate also may accumulate in the soil over a 

period of months to a few years before moving into tile drains 

and streams after rainfall (Eckert, 1995). The potential for 

nitrate movement is greatest during and immediately after 

rainfall regardless of when the nitrate was applied (Kladivko 

and others, 1999). Very low nitrate concentrations were found 

in ground-water samples in the watershed (Baker and others, 

2006). This is because the small amount of nitrate that moves 

below tile drains converts to gaseous forms of nitrogen (undergoes denitrification) in the saturated ground-water soils (Schnepf and Cox, 2006, and Johnson and others, 2005). 

Producer

Nitrogen (N)

Phosphorus (P)

?

Field

Ground

Water

Tile 

Drain

Precipitation

Leary Weber

Ditch Water

Infiltration

(25% N and 1% P)

Crop Harvest

(50% N and 

15% P)

Release to Atmosphere

(15% N)

Accumulation 

in Soil

(5% N and 

80% P) Surface Runoff (5% N and P)

Figure 3. Nutrient transport pathways in Leary Weber Ditch 

Watershed, Hancock County, Ind. Numbers in parenthesis are 

approximate transport amounts for a typical rain-fed watershed 

(Schnepf and Cox, 2006). Arrow is dashed and queried where 

pathway is uncertain.

Most of the phosphorus that has not accumulated in soils or is not taken up by plants moves in runoff to the ditch (fig. 3). Phosphorus concentrations increase in tile drains in response to increased rainfall; however, concentrations are only one tenth as large in 

the tile drain as in runoff (Baker and others, 2006). Phosphorus concentrations are low in tile drains between storms, indicating that 

phosphorus moving in matrix flow attaches to soils before reaching tile drains. For the same reason, negligible amounts of phosphorus 

move into ground water. 

Understanding Nutrients

The specific chemical form that nitrogen and phosphorus 

take in the environment determines how readily these nutrients 

attach to soil particles.

•	 Nitrogen occurs naturally in many different organic or inorganic forms. Inorganic nitrogen, found in commercial fertilizers, is usually applied to crops as urea, urea ammonium 

nitrate, or anhydrous ammonia. Nitrogen from fertilizers is 

eventually converted to nitrate by the process of nitrification. 

Nitrate does not readily attach to soils, readily dissolves in 

water, and can be taken up by plants. Denitrification occurs in 

saturated soils when bacteria use nitrate as an oxygen source 

resulting in the conversion of nitrate to gaseous forms of 

nitrogen (Johnson and others, 2005). 

•	 Inorganic phosphorus, found in commercial fertilizers, can 

be taken up by plants. It readily reacts with iron, aluminum, 

and calcium ions to form substances that can attach to soil 

particles, reducing the potential for transport through soils 

(Hyland and others, 2005). 
Producer

Pesticides that readily 

dissolve in water

Pesticides that readily 

attach to soil particles

?

Field

Ground

Water

Tile 

Drain

Precipitation

Leary Weber

Ditch Water

Release to Atmosphere

Surface Runoff

Plant Uptake Accumulation 

in Soil

Figure 4. Pesticide transport pathways in Leary Weber Ditch 

Watershed, Hancock County, Ind. Size of arrow indicates relative 

transport amounts and is dashed and queried where pathway is 

uncertain. 

Pesticide-Transport Pathways

Pesticides are applied to fields to control weeds, insects, 

or fungi on crops. Pesticides move from the field into the air, in 

runoff, or through soils to tile drains or ground water (fig. 4). 

Rainfall and runoff immediately following application generally 

cause the greatest movement of pesticides (Kladivko and others, 

1999). Pesticides transported in runoff reach the ditch soon after 

rainfall begins; concentrations typically peak when flow in the 

ditch peaks (Baker and others, 2006). 

Infiltration through the soils to tile drains also is a major 

pathway for pesticides that readily dissolve in water such as 

acetochlor and atrazine (Baker and others, 2006). These pesticides are transported in preferential flow in greater quantities 

than pesticides that readily attach to soil particles. Concentrations of atrazine were much lower in normal tile flow than 

concentrations found in peak flow in tiles (Baker and others, 

2006). Because of its persistence (fig. 5), atrazine has a greater 

potential to move to ground water than less persistent pesticides; 

however, pesticides were rarely detected (the few detections that 

occurred were low concentrations) in ground water in Leary 

Weber Ditch Watershed (Baker and others, 2006).

Infiltration through the soils is not a major transport mechanism for pesticides such as chlorpyrifos and glyphosate. When 

transport does occur, it is primarily in runoff and eroded soils. 

These pesticides readily attach to soil particles and are retained 

in the upper soil layers. Tile drains decrease surface runoff and 

erosion resulting in an overall decrease in the transport of these 

pesticides (Kladivko and others, 2001). Glyphosate and chlorpyrifos were found in tile drains at much lower concentrations than found in runoff. Glyphosate and chlorpyrifos transport through soils 

generally occurs by preferential flow soon after rainfall (Stone and Wilson, 2006); however, very low concentrations of glyphosate 

were found in some ground-water samples indicating that small amounts of glyphosate can be transported relatively long distances 

through soils (Baker and others, 2006). 

Understanding Pesticides

Pesticides detected most frequently in streams and ground 

water are primarily those with the greatest use, mobility, and 

persistence (Gilliom and others, 2006). Pesticides that are 

most commonly used on corn and soybeans are the herbicides 

acetochlor, alachlor, atrazine, glyphosate, and metolachlor, and 

the insecticide chlorpyrifos (Gilliom and others, 2006). 

•	 Pesticides that readily dissolve in water can move to streams 

and ground water in greater quantities than chemicals that 

readily attach to soil particles (Kladivko and others, 2001). 

•	 Persistent pesticides remain in their original form in the 

environment for long periods and may be transported for long 

distances or accumulate in soils, sediment, or biota (Gilliom 

and others, 2006). 

Acetochlor

Alachlor

Glyphosate

Chlorpyrifos

Metolachlor

Atrazine

Atrazine

Alachlor

Metolachlor Acetochlor

Chlorpyrifos

Glyphosate

Persistent in Soils

Least Readily Attaches to Soil Particles Most

Least Most

[Pesticide trade names: atrazine, Aatrex; acetochlor, Harness; alachlor,

Lasso; chlorpyrifos, Lorsban; glyphosate, Roundup; metolachlor, Dual]

Figure 5. Relative persistence and ability to attach to soil particles 

for commonly used pesticides on corn and soybeans. Sources: 

Gilliom and others, 2006; Accinelli and others, 2004; European 

Commission, 2002. 
What are the Implications for Conservation 

Practices?

Many conservation practices have been developed to 

manage soil, water, nutrients, and pesticides. The goal of these 

conservation practices is to reduce soil erosion which prevents 

the loss of valuable soil and nutrients, and to protect water 

quality by reducing sediment, nutrient and pesticide transport to 

streams and ground water. Nutrients that enter surface water can 

cause excessive algae growth that depletes oxygen (hypoxia) 

and may cause harm to animals in the water. Excess nutrients 

from the Midwest have been linked to hypoxia in the Gulf of 

Mexico (Alexander and others, 2000). Pesticides in water may 

be toxic to plants and animals living in or drinking the water. 

Interactions between water and chemical transport, 

chemical properties, and conservation practices are complex in 

agricultural areas like the Leary Weber Ditch Watershed. By 

understanding that conservation practices designed to control 

concentrations of one environmental contaminant may affect 

concentrations of another, environmental managers may better 

weigh the pros and cons of implementing a specific conservation practice. For example, conservation tillage may decrease 

sediment erosion but may cause increased atrazine usage and 

subsequent movement into streams (Devlin and others, 2000). 

Environmental gains from decreased runoff of sediment and 

attached nutrients may help water quality in agricultural areas 

but cause greater problems for downstream drinking-water 

facilities needing to remove the atrazine. 

Implications

•	 For pesticides, reducing their use (pesticide management) is 

likely to be an effective way to reduce their concentrations 

in watersheds, particularly in streams (other approaches also 

may be effective) (Gilliom and others, 2006).

•	 Increases or decreases in pesticide use (pesticide management) can result in rapid corresponding changes in pesticide 

concentrations in stream water (and tile-drain water)—generally within 1 to 2 years (Gilliom and others, 2006).

•	 Planting perennial cover crops (nutrient management) results 

in greater plant uptake of nutrients and decreases both nitrogen and phosphorus losses from fields (Schnepf and Cox, 

2006).

•	 Tile drains may help protect ground water, but increase pesticide and nutrient transport to streams (Gilliom and others, 

2006; and Baker and others, 2006) 

•	 Tile drains increase transport of chemicals that readily dissolve in water (nitrate, acetochlor, alachlor, atrazine, and 

metolachlor) and decrease transport of chemicals that readily 

attach to soil particles (phosphorus, chlorpyrifos, and glyphosate) (Schnepf and Cox, 2006).

•	 Controlled drainage reduces nitrate transport (Schnepf and 

Cox, 2006); however, draining a large amount of water at 

the start of the growing season may release nitrate that has 

accumulated in the soil.

•	 Conservation tillage may reduce transport of chemicals that 

readily attach to soil particles (phosphorus, chlorpyrifos, and 

glyphosate) but may increase the transport of chemicals that 

readily dissolve in water (nitrate, acetochlor, alachlor, atrazine, and metolachlor) by increasing infiltration to tile drains 

(Schnepf and Cox, 2006).

•	 Conservation tillage often requires increased pesticide usage 

resulting in increased transport of pesticides (Schnepf and 

Cox, 2006).

•	 Grassed waterways and filter strips filter sediment and may 

reduce the transport of pesticides that attach to soil particles 

(chlorpyrifos and glyphosate); they may not reduce the transport of pesticides that readily dissolve in water (and infiltrate 

soils) (acetochlor, alachlor, atrazine, and metolachlor) (Schnepf and Cox, 2006). 

Conclusions

The interactions between water and chemical transport, 

chemical properties, and conservation practices are complex in 

the Leary Weber Ditch Watershed. Water transport to tile drains 

is the primary controlling factor for much of the agriculturalchemical transport in the watershed. Tile drains reduce surface 

runoff and increase infiltration. Chemicals that readily dissolve 

in water tend to move through soils and preferential flow pathways to tile drains that flow through outlets to the ditch. Runoff 

is a major transport pathway for chemicals that readily attach to 

soils. Runoff also is an important transport pathway for pesticides that readily dissolve in water when rainfall occurs soon 

after application. 

Nutrient and pesticide-management practices that reduce 

the use of agricultural chemicals are likely to be an effective 

way to reduce their concentrations in streams. Conservation 

practices designed to reduce surface runoff and erosion may 

not reduce the transport to tile drains of chemicals that readily 

dissolve in water. These conservation practices may reduce the 

transport of chemicals that readily attach to soils. 

Examples of Typical Conservation Practices in 

Midwestern Watersheds (Schnepf and Cox, 2006)

•	 Pesticide and nutrient management (managing the amount, 

source, placement, form, and timing of the application of 

chemicals) reduces the amount of chemicals available for 

transport to the air, streams and ground water.

•	 Installation of tile drains (laying drainage pipe below the field 

surface connected to outlets at the stream) increases infiltration and reduces surface runoff and erosion.

•	 Controlled drainage-water management (managing tile-drain 

flow so that more water is held in the soils during the nongrowing season and controlling release at planting time to 

drain the fields for planting) raises the water table and keeps 

soils saturated through the non-growing season. This practice 

reduces infiltration to tile drains and increases surface runoff 

during the non-growing season, promotes denitrification, and 

provides more water for evapotranspiration during the growing season. 

•	 Conservation tillage (no-till, mulch-till, and ridge-till) (leaving crop residue on the field) reduces and slows surface 

runoff and soil erosion, and increases infiltration to the soil.

•	 Installation of filter strips (planting vegetation along waterways) increases infiltration and reduces and slows surface 

runoff and soil erosion. 

•	 Installation of grassed waterways (planting vegetation in 

natural drainage areas such as gullies) directs the flow of 

water and reduces gully erosion. The vegetation also may trap 

sediment and absorb some chemicals and nutrients. 
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 (USGS) to install equipment in or near their farm fields. The collection and analysis 

of water samples for glyphosate was made possible with the 

cooperation of the Toxic Substances Hydrology Program and 

the Organic Geochemistry Research Laboratory of the USGS. 

The authors are grateful for the technical reviews by Paul Capel 

(USGS Minnesota Water Science Center) and Ronald Zelt 

(USGS Nebraska Water Science Center).

References

Accinelli, C., Screpanti, C., Vicari A., and Catizone, P., 2004, 

Influence of insecticidal toxins from Bacillus Thuringiensis 

subsp. kurstaki on the degradation of glyphosate and glufonsinate-ammonium in soil samples: Agriculture, Ecosystems 

and Environment, v. 103, p. 497–507.

Alexander, R.A., Smith, R.B., and Schwarz, G.E., 2000, Effect 

of stream channel size on the delivery of nitrogen to the Gulf 

of Mexico: Nature, v. 403, p. 758–761.

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. Available online at URL http://pubs.usgs.

gov/sir/2006/5251/ .

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

U.S. Geological Survey on sources, transport, and fate of 

agricultural chemicals: U.S. Geological Survey Fact Sheet 

2004–3098, 4 p. Available online at URL http://pubs.usgs.

gov/fs/2004/3098/ .

Devlin, D.L., Regehr, D.L., and Barnes, P.L., 2000, Managing to 

minimize atrazine runoff: Manhattan, Kansas State University 

Agricultural Experiment Station and Cooperative Extension 

Service, MF2208, 12 p. Available online at URL http://www.

oznet.ksu.edu/library/crpsl2/samplers/mf2208.asp 

Eckert, D.J., 1995, Nitrates in surface water: Ohio State University Extension Agronomy Facts AGF-204-95, 3 p. Available 

online at URL http://ohioline.osu.edu/agf-fact/0204.html 

European Commission, Health and Consumer Protection 

Directorate-General, 2002, Glyphosate (6511/VI/99-final): 

Finalized in the Standing Committee on Plant Health at its 

meeting on 29 June 2001, 56 p. Available online at URL 

http://ec.europa.eu/food/fs/ph_ps/pro/eva/existing/list1_

glyphosate_en.pdf 

Gilliom, R.J., Barbash, J.E., Crawford, C.G., Hamilton, P.A., 

Martin, J.D., Nakagaki, Naomi, Nowell, L.H., Scott, J.C., 

Stackelberg, P.E., Thelin, G.P. and Wolock, D.M., 2006, The 

quality of our nation’s waters—Pesticides in the Nation’s 

streams and ground water, 1992–2001: U.S. Geological Survey Circular 1291, 172 p. Available online at URL 

http://pubs.usgs.gov/circ/2005/1291/ .

Hyland, Charles, Ketterings, Quirine, Dewing, Dale, Stockin, 

Kristen, Czymmek, Karl, Albrecht, Greg, and Geohring, 

Larry, 2005, Phosphorus basics—the phosphorus cycle: Cornell University Cooperative Extension Agronomy Fact Sheet 

Series Fact Sheet 12, 2 p. Available online at URL 

http://nmsp.css.cornell.edu/ .

Johnson, Courtney, Albrecht, Greg, Ketterings, Quirine, Beckman, Jen, and Stockin, Kristen, 2005, Nitrogen basics—the 

nitrogen cycle: Cornell University Cooperative Extension 

Agronomy Fact Sheet Series Fact Sheet 2, 2 p. Available 

online at URL http://nmsp.css.cornell.edu/ .

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(1):1-62.

Kladivko, E.J., Grochluska, J., Turco, R.F., VanScoyoc, G.E., 

and Eigel, J.D., 1999, Pesticide and nitrate transport into subsurface tile drains of different spacings: Journal of Environmental Quality, v. 28:997-1,004.

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. Available online at URL http://pubs.usgs.gov/

sir/2006/5170/ .

Schnepf, Max and Cox, Craig, eds., 2006, Environmental benefits of conservation on cropland—the status of our knowledge: Ankeny, Iowa, Soil and Water Conservation Society, 

325 p.

Stone, W.W., and Wilson, J.T., 2006, Preferential flow estimates 

to an agricultural tile drain with implications for glyphosate 

transport: Journal of Environmental Quality, v. 35(5), 

p. 1,825–1,835.

Contacts for additional information or questions

William R. Guertal, Director

Indiana Water Science Center

U.S. Geological Survey

5957 Lakeside Blvd.

Indianapolis, IN 

46278–1996

Email: wguertal@usgs.gov

(317) 290-3333

_____________________________________________

By Nancy T. Baker, Wesley W. Stone,

Jeffrey W. Frey, and John T. Wilson

USGS promotes public access to water-quality 

information

This Fact Sheet is available free of charge on the World Wide 

Web at http://pubs.usgs.gov/fs/2007/3084

Information about the NAWQA Program including national 

summaries of pesticides and nutrients, information on sampling 

designs and methodology analysis is available at http://water.

usgs.gov/nawqa