Grasslands

Wetlands

Urban

Explanation

Forest

Shrubland

Agricultural

Water

Other

Investigating the Environmental Effects of Agriculture 

Practices on Natural Resources

Scientific Contributions of the U.S. Geological Survey to Enhance

the Management of Agricultural Landscapes

Land cover map of the conterminous United 

States from early 1990s data (Vogelmann and 

others, 2001; Nakagaki and Wolock, 2005).

Printed on recycled paper U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2007–3001

January 2007

 U.S. Geological Survey (USGS) enhances and protects the 

quality of life in the United States by advancing scientific knowledge to facilitate effective management of hydrologic, biologic, and 

geologic resources (http://www.usgs.gov). Results of selected USGS 

research and monitoring projects in agricultural landscapes are 

presented in this Fact Sheet. Significant environmental and social 

issues associated with agricultural production include changes in 

the hydrologic cycle; introduction of toxic chemicals, nutrients, and 

pathogens; reduction and alteration of wildlife habitats; and invasive 

species. Understanding environmental consequences of agricultural 

production is critical to minimize unintended environmental consequences. The preservation and enhancement of our natural resources 

can be achieved by measuring the success of improved management 

practices and by adjusting conservation policies as needed to ensure 

long-term protection. 

Interdisciplinary USGS research and monitoring plays a key 

role in providing independent scientific information needed for the 

understanding, management, and mitigation of short- and long-term 

effects of agricultural practices on natural and human resources. 

USGS scientific information is used by a variety of stakeholders 

that include public, private, and special-interest groups, agricultural 

producers, and State, Tribal, and Federal governments that manage 

the Nation’s natural resources. 

Effects of land use change and habitat fragmentation on wildlife.

Balancing conflicting urban and agricultural water demands.

Influence of air and ground-water and surface-water interactions on 

water quality.

Effects of agricultural drainage, irrigation, and return flow on water 

quality.

Development and implementation of innovative farming techniques to 

conserve soil and water and to improve water quality.

Effects of genetically modified organisms on native species and habitats.

Tools for identifying sources of agricultural contamination and rapid 

assessment techniques.

Effects of pesticides, nutrients, and sediments on fish and wildlife 

health and habitat quality.

Effects of watershed characteristics—soils, riparian forests, and wetlands—effects on nutrient uptake, retention, and cycling.

Transport and fate of endocrine disrupting compounds, veterinary 

antibiotics, feed additives, hormones, and pathogens in terrestrial and 

aquatic ecosystems.

•

•

•

•

•

•

•

•

•

•

Over half of the land in the Nation’s lower 48 States is in 

crops, pasture, and range (Lubowski and others, 2006). By 2004, 

half of the original wetlands in the lower 48 states was converted 

to mostly agricultural uses (Claassen, 2004). From the start of 

European settlement until 1954, about 42 percent of original wetlands were drained and filled and used for settlement and agriculture. From 1954 to 1974, wetland loss was reduced by half (Wiebe 

and Golleron, 2006). Nearly all of the pre-settlement forest, prairie, and wetland areas in the Midwestern and Great Plains States 

have been converted to or affected by agricultural production.

Technological advances in agricultural production methods 

over the past 60 years have dramatically changed the character 

of agriculture. The number of farms declined from 6.8 million in 

1935 to 2.1 million in 2002. Whereas small family-owned farms 

once produced the majority of the Nation’s agricultural products, 

in 2003 small farms accounted for 91 percent of farms, but only 

27 percent of total agricultural production. By 2002, half of the 

farm sales came from 2 percent of farms and 11 percent of the 

land in farms (Wiebe and Golleron, 2006). Support of this intensified agriculture requires larger fields, reduction in the types and 

rotations of crops, and greater reliance on agrichemicals (nitrogen, 

phosphorus, pesticides) to maintain high productivity. 

Significant environmental and social issues associated with 

agricultural production include changes in the hydrologic cycle; 

introduction of toxic chemicals, nutrients, and pathogens; reduction 

and alteration of wildlife habitats; and invasive species. Understanding environmental consequences of agricultural production 

is critical to minimize unintended environmental consequences. 

The preservation and enhancement of our natural resources can 

be achieved by measuring the success of improved management 

practices and by adjusting conservation policies as needed to ensure 

long-term protection. 

Science Issues and Needs Identified by the USGS, as Related to 

Environmental Impacts of Agricultural Practices

The
PUMPED WELL

RECHARGE AREA

Stream DISCHARGE AREA

Days

Years

Years

Days

Centuries

Millennia

Confining bed

Confining bed

Confined

aquifer

Unconfined

aquifer

Confined

aquifer

Water table

Movement of Agricultural Chemicals Through the 

Hydrologic System

The key to understanding and managing effects of agriculture-associated chemicals, bacteria, and pathogens involves tracing the movement of compounds from where they are applied, 

knowing their persistence in the environment, measuring their 

transport and fate, and measuring their bioavailability and 

potential effects on humans and wildlife. Transport by air and 

water-soil mixtures are the two primary ways for compounds to 

travel from agricultural lands into surrounding environments. 

Effects of agricultural chemicals can vary widely depending on 

local topography, hydrology, soils, geology, and the rate and 

timing of applications relative to precipitation. 

The USGS studies the movement of agricultural chemicals 

in the entire hydrologic cycle. Many studies of the behavior 

of chemicals applied to crops and soils have focused on crop 

uptake, soil quality, and surface runoff, and do not include the 

movement of these chemicals in the atmosphere, below the root 

zone, through the unsaturated zone, into ground water, and 

eventually into streams. USGS studies have shown that watersheds with large ground-water inflows generally respond more 

slowly to changes in chemical application rates than watersheds dominated by surface-water inflows (Bohlke, 2002). Tile 

drainage intercepts downward flow, or recharge, and delivers 

it quickly to streams, reducing the potential for nutrient reduction. Understanding the interaction of these processes is key to 

understanding associated movement of natural and agricultural 

chemicals. The amounts of chemicals transported can vary by 

several orders of magnitude due to fluctuations in precipitation, 

streamflow, and ground-water movement. It can be difficult to 

predict or measure the response of a watershed to changes in 

management if the watershed response to those changes is equal 

to or less than changes caused by natural variability. Understanding the hydrologic setting and its controlling variables can 

improve the design and efficiency of monitoring programs and 

models that measure or estimate watershed response to changes 

in management practices.

Nutrients

Nutrient concentrations in streams and shallow ground 

water within agricultural areas are often elevated due to multiyear inputs of nutrients from fertilizers and manure (U.S. Geological Survey, 1999). Stream and shallow ground-water nitrate 

concentrations are especially elevated in the Midwest, where 

soils are often artificially drained to improve crop production.

The U.S. Department of Agriculture (USDA) estimates 

that 50 percent of cropland in Indiana has been artificially 

drained, and Indiana ranks second in total area artificially 

drained (U.S. Department of Agriculture, 1987). Most nitrogen 

transport through tile drains corresponds to the flow of water 

through the drains (Brouder and others, 2005). Thus, control of 

tile drainage is important in reducing stream and ground-water 

nitrate concentrations. 

In addition, tile drainage changes soil chemistry, which 

can have long-term effects. Cropland that is removed from 

production and restored to wetland habitat may not fully 

recover to native vegetation because of soil chemistry changes 

from tile drainage. 

The USGS is also examining impacts of agricultural practices on streams and reservoir quality in the Fort Cobb watershed, Oklahoma. Agriculture is the primary land use, with row 

crops, pasture grazing of cattle, and several large concentrated 

animal feeding operations (CAFOs) for hog production present 

within the watershed. Ground water is highly contaminated with 

nitrate, and Fort Cobb reservoir is highly eutrophic, meaning 

that it has high concentrations of nutrients that promote excessive plant growth and low oxygen levels (Fairchild and others, 

2004). USGS research to determine the sources of nutrients to 

the reservoir will guide State land management agencies in the 

development and application of best management practices to 

reduce the levels of nutrients in the reservoir.

Ground-water flow paths vary greatly in length, depth, and 

travel time from points of recharge to points of discharge in 

the ground-water system. From Winter and others (1998).

The University of Wisconsin Discovery Farm and Pioneer Farm Programs are designed 

to gather on-farm and water quantity and quality information from a variety of farming 

systems within different environmental settings to better understand the effects of 

agriculture on water resources. Here, USGS personnel participate in an educational 

program to explain findings to agricultural producers. 
Pesticides and Emerging Chemicals 

Pesticides and their degradates can be found almost any 

time of the year in streams draining extensive agricultural or 

urban areas. They are also often found in shallow ground water 

(Gilliom and others, 2006). Samples collected from 1992 to 

2001 showed that at least one pesticide compound was detected 

97 percent of the time in streams and 61 percent of the time in 

shallow ground water. 

Atrazine is a commonly used herbicide that controls broadleaf weeds for a wide variety of crops. It has an estimated annual 

application of 76 million pounds. Atrazine is also an endocrine 

disrupting chemical that can cause reproductive problems in 

mammals, amphibians, and fish. It has a high potential for entering 

surface and ground waters because it is relatively persistent in soils 

and is moderately soluble in water. Gilliom and others (2006) 

documented that atrazine was the most commonly detected pesticide 

in both streams and ground water. Rates of atrazine occurrence 

were found to be similar in both agricultural and urban areas. 

The USGS conducted a multi-year study to determine 

population-level implications of atrazine on metabolic pathways 

related to endocrine regulation (Tillitt and others, 2006). The 

study developed, characterized, and validated biomarkers that 

identify atrazine occurrence in liver and gonad tissues. These 

biomarkers are used in environmental assessments of the effects 

of atrazine in mammals, amphibians, and fish.

The USGS also has developed innovative passive sampling techniques for detecting persistent organic contaminants 

(organochlorine pesticides), current use pesticides, and emerging contaminants (pharmaceuticals, hormones, and wastewater 

chemicals). Passive samplers are deployed in surface water and 

provide information on the time-weighted average concentration 

of the bioavailable fraction of these organic chemicals. These 

techniques can be used in combination with bioindicator tests to 

provide a toxicological assessment of compounds present in a 

watershed. A USGS study (Petty and others, 2004) utilized these 

passive samplers for tracking chemicals from treated wastewater 

into and out of a wetland. This study helped State and Federal 

agencies determine the effectiveness of these wetlands in 

removing contaminants.

Apprehension about the effects of emerging contaminants, 

such as antibiotics and hormones, entering the environment from 

animal and human waste has raised questions about the likely 

occurrence of these chemicals in streams and ground water. The 

USGS began studies to examine the occurrence of many emerging contaminants used in veterinary medicine based on research 

of emerging contaminants in the United Kingdom and the Netherlands (Boxall and others, 2003). Common veterinary medicines 

include anti-microbials, anti-parasitic and anti-fungal medicines, 

hormones, growth promoters, anti-inflammatory medicines, anesthetics, and tranquilizers.

The persistence and toxicity of these medications are affected 

by environmental conditions such as temperature, pH, and soil 

type; consequently, these chemicals may degrade quickly or persist 

longer than expected (Boxall and others, 2003). Compounds may 

be transported quickly to surface waters via runoff or they may be 

transported slowly and persist months after use. Environmental 

concentrations of emerging compounds generally occur in amounts 

that are an order of magnitude lower than acute toxicity levels. 

 The USGS is conducting 

 interdisciplinary research in the 

watershed of Fort Cobb Reser

voir, Oklahoma, to better under

stand relations between 

 land use and water quality. 

 Pesticide concentrations exceeded human-health benchmarks 

in about 10 percent of stream samples and about 1 percent of 

shallow ground-water samples. Aquatic-life benchmarks were 

exceeded in 57 percent of stream samples and 31 percent of 

bed-sediment samples. Wildlife benchmarks were exceeded in 87 

percent of whole fish collected. Urban areas had similar concentrations due to domestic use of pesticides for lawn care, gardening, 

and household uses (Gilliom and others, 2006).

Well-drained soils that do not have artificial drainage are 

estimated to have the most number of atrazine detections in 

shallow ground water (for example, western Iowa and eastern 

Nebraska). Gilliom and others (2006) identified the major factors controlling the presence of atrazine in shallow ground water 

to be soil-infiltration rates, presence and extent of artificial 

drainage, water-holding capacity of soils, soil permeability, 

quantity of ground-water irrigation, the proportion of the landscape in agricultural land, and the quantity of atrazine applied 

(Stackelberg and others, 2005). These factors were used to 

predict frequency of atrazine occurrence across the U.S. 
Management controls required to minimize these compounds in 

the environment will depend on a greater understanding of the 

toxic effects of these chemicals on wildlife and humans.

Veterinary antibiotics and hormones have been found at 

low levels in streams in agricultural areas, but the effect of 

mixtures of many compounds and degradates, which may 

also be toxic, is not well understood. It is important to assess 

the presence and movement of these chemicals, as well as the 

short- and long-term risk to wildlife and humans.

Bacterial Indicators and Pathogens

Animal agriculture can contribute excess bacteria and 

pathogens to streams and ground water if not properly managed. 

Practices such as grazing, storing manure in lagoons, and 

applying manure to fields must be properly sited and conducted 

under conditions that minimize the potential for microbial 

movement to streams and ground water. Fecal coliform 

bacteria in poultry litter survived for as long as 8 weeks in a 

Missouri stream that drained fields where litter was applied 

(Schumacher, 2003). CAFOs require particular attention 

because they house large numbers of animals in a small area. 

High numbers of bacteria and pathogens also can be introduced 

by other animals, such as large populations of wildlife or domestic 

pets in urban areas. A description of pathogens that relate to 

animal agriculture is available at http://lpe.unl.edu/pathogen.html

Development of techniques for determining the sources 

of bacteria and for analyzing pathogens directly helps to 

identify agricultural activities or areas that need better control. 

These techniques also are used to differentiate bacteria sources 

contributed by municipal and domestic sewage from those 

contributed by animal agriculture. Although many agencies and 

researchers are using source tracking of fecal contamination, 

the techniques can produce false identifications, and better tools 

need to be developed. The use of multiple lines of evidence, 

such as chemical and hydrologic evidence to identify transport 

pathways in addition to source-tracking techniques, provides 

the most reliable information on bacterial sources (Stoeckel and 

others, 2004).

Wetlands Ecosystem Services

Research began in 1967 at Cottonwood Lake, North 

Dakota, to understand the dynamic processes that support 

waterfowl and prairie wetlands in the prairie pothole region of 

the northern Great Plains (Swanson, 1987). Studies of soils, 

hydrology, water chemistry, and biotic communities (aquatic 

invertebrates and plants, amphibians, and birds) have demonstrated that hydrologic function and climate, in concert with the 

geochemical characteristics of prairie soils, are primary drivers 

of ecosystem function (Winter, 2003; Euliss and others, 2004).

Composition of wetland biological communities can shift 

drastically in response to climatic variations, which underscores 

the need to separate natural ecosystem drivers from agricultural 

influences (Euliss and Laubhan, 2005). Prairie wetlands cycle 

between climatic extremes of droughts and floods, which causes 

variability in wildlife habitat, flood-water storage, water-quality 

improvement, carbon sequestration, and ground-water recharge 

over time. The understanding gained through long-term study at 

Cottonwood Lake has implications for evaluating the effectiveness of USDA land conservation programs as well as providing 

guidelines for reestablishing, restoring, and preserving wetland functions that meet Farm Service Agency (FSA), Natural 

Resources Conservation Service (NRCS), and Department of 

Interior (DOI) objectives for wetland conservation. 

Effects of Crops and Harvesting Practices on Waterfowl and 

Migratory Birds

Changes in agricultural practices and harvesting methods 

can have important effects on food sources of migratory birds 

and other wildlife dependent on agricultural lands. A USGS 

study (Krapu and others, 2004) in the Central Platte River Valley and Rainwater Basin area of Nebraska, important staging 

areas for bird migration, found that increased efficiency of 

corn harvest (up 47 percent over 25 years) and greater acreage 

devoted to soybeans has reduced availability of waste grains 

as a food source. The increased harvest efficiency resulted in 

decreased storage of fat by sandhill cranes and waterfowl on 

migration staging areas enroute to breeding grounds. Ongoing 

management discussions are evaluating how to provide adequate 

waste corn and high-energy foods to meet crane and waterfowl 

needs. Where possible, a wide distribution of roosting habitat is 

maintained in the Central Platte River Valley to disperse cranes 

and make food available near the river, shortening the distance 

that cranes fly to forage. Another strategy being considered is 

to establish scattered fields of corn grown specifically for crane 

needs; these fields would not be harvested until March to prevent waterfowl from consuming the corn before cranes arrive. 

These strategies are critical for determining the best ways to 

maintain agricultural production while providing for the migratory and reproductive needs of bird species. 

Another USGS study in the lower Mississippi River alluvial valley investigated the effects of changes in rice production 

practices on the availability of waste rice seed for wintering 

waterfowl. Stafford and others (2006) sampled 150 rice fields 

over 3 years to determine the amount of seed remaining seasonally. This study has led to experiments comparing post-harvest management practices (such as disking and burning) that 

conserve waste rice following harvest with practices that would 

allow a second rice crop to be left in the field as waterfowl 

food. Regional managers have used these types of data to meet 

objectives for conserving foraging habitat as established by the 

Lower Mississippi Valley Joint Venture (LMVJV Migratory 

Bird Science Team, 2002).

Allowing livestock stream access increases 

the presence of excess nutrients, bacteria, 

pathogens, antibiotics, and hormones in 

the water.
Sandhill cranes feeding in harvested cornfield 

in Central Platte Valley.

Science Understanding Enhances Protection of 

Natural Resources

The USGS relies on the complementary disciplines 

of biology, chemistry, geology, and hydrology to provide a 

multidisciplinary understanding of agricultural watershed 

processes. Monitoring the environmental consequences of 

agricultural land use and conservation effectiveness leads 

to improved scientific understanding of environmental 

conditions in both monitored and unmonitored areas. Identifying and understanding watershed processes is critical in 

identifying areas of the landscape that are most sensitive to 

contamination and in improving management practices.

Scientific results from USGS monitoring and research 

are freely available to the public and private sectors through 

published reports and Web-based sources. Landowners, 

scientists, and local, State, and Federal agencies with responsibilities for land, water resources, and wildlife can use 

this information to improve management of the Nation’s 

natural resources.

Science-based management practices, refined through 

continued research and monitoring by the USGS and its 

partners, will lead to enhanced protection of the Nation’s 

natural resources while maintaining an economically viable 

agricultural industry.

Integrating Conservation into Agricultural 

Landscapes

In recent decades there has been a growing need for attention 

by the USDA for integration of effective conservation practices 

into agriculturally dominated landscapes (U.S. Department of 

Agriculture, 2001; Allen and Vandever, 2005). To be acceptable and 

more widely adopted by landowners, conservation programs must 

not present economic burdens in their application, and positive 

results must be observable to those participating. Since 1997, the 

USGS and the FSA have collaborated on research for maximizing 

management of over 34 million acres of land enrolled in the Conservation Reserve Program (CRP) to meet multiple environmental 

and landowner objectives. These studies focus on effects of grassland and conservation management practices (such as grazing, 

haying, buffers, and farmed wetlands) that address long-term 

quality of wildlife habitats associated with agricultural land use 

while meeting the expectations and limitations of operators enrolled 

in the program. Results from these CRP-focused studies have 

implications for management of lands enrolled in other USDA 

conservation programs such as the Environmental Quality Incentives Program (EQIP) and the Conservation Security Program 

(CSP). USGS studies have documented improvements that these 

conservation programs have made to increase wildlife populations, 

reduce soil erosion, and provide economic stability and social 

benefits to agricultural producers and the public (Allen and 

Vandever, 2003).
Cover and inside background images courtesy of Agricultural Research Service; other photographs are from the USGS.

References

Allen, A.W., and Vandever. M.W., 2003, A 

national survey of Conservation Reserve 

Program (CRP) participants on environmental effects, wildlife issues, and 

vegetation management on program lands: 

Biological Science Report, USGS/BRD/

BSR-2003-0001, U.S. Government Printing Office, 51 p.

Allen, A.W., and Vandever, M.W., eds., 2005, 

The Conservation Reserve Program—

planting for the future: Proceedings of 

a National Conference, Fort Collins, 

Colorado, June 6–9, 2004: U.S. Geological Survey Scientific Investigations Report 

2005-5145, 248 p.

Bohlke, John-Karl, 2002, Groundwater recharge 

and agricultural contamination: Hydrogeology Journal, v. 10, p. 153-179.

Boxall, A.B.A., Kolpin, D.W., Sorensen, B.H., 

and Tolls, J., 2003, Are veterinary medicines 

causing environmental risks?: Environmental Science and Technology, p 287-294.

Brouder, S., Hofmann, B., Kladivko, E., Turco, 

R., Bongen, A., and Frankenberger, J., 2005, 

Interpreting nitrate concentrations in tile 

drainage water: Purdue University Extension Agronomy Guide, AY-318-W, 7 p.

Claassen, Roger, 2004, In the Long Run—Wetland Losses: U.S. Department of Agriculture Economic Research Service Amber 

Waves, v. 2, Issue 3.

Euliss, N.H., Jr., LaBaugh, J.W., Frederickson, 

L.H., Mushet, D.M., Laubhan, G., Swanson, G.A., Winter, T.C., Rosenberry, D.O., 

and Nelson, R.D., 2004, The wetland 

continuum: a conceptual framework for 

interpreting biological studies: Wetlands, 

v. 24, p. 448-458.

Euliss, N.H., Jr., and Laubhan, M.K., 2005, 

Quantifying the environmental benefits 

of CRP on prairie wetlands: separating 

Acts of Nature from Acts of Congress, in 

A.W. Allen and M.W. Vandever, eds., The 

Conservation Reserve Program—planting 

for the future: Proceedings of a National 

Conference, Fort Collins, Colorado, June 

6–9, 2004: U.S. Geological Survey Scientific Investigations Report 2005-5145, p. 

11-15.

Fairchild, J., Lakish, B., Echols, K., Chapman, 

D., Johnson, B., and Jones, S., 2004, An 

integrated assessment of the trophic status 

of Fort Cobb Reservoir, Oklahoma, Final 

report: U.S. Bureau of Reclamation, 93 

p., available at http://www.cerc.usgs.gov/

pubs/center/pdfDocs/Fort_Cobb.pdf

Gilliom, R.J., Barbash, J.E., Crawford, C.G., Hamilton, P.A., Martin, J.D., Nakagaki, N., 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.

Krapu, G.L., Brandt, D.A., and Cox, R.R., Jr., 

2004, Less waste corn, more land in soybeans and the switch to genetically modified 

crops: trends with important implications 

for wildlife management: Wildlife Society 

Bulletin, v. 32, p.127-136.

LMVJV Migratory Bird Science Team, 2002, 

Developing and refining the biological 

foundation of the Lower Mississippi Valley 

Joint Venture: an assessment of biological 

planning, monitoring, and evaluation issues: 

Vicksburg, Miss., Lower Mississippi Valley 

Joint Venture Office, 16 p.

Lubowski, R.N., Vesterby, Marlow, Bucholtz, 

Shawn, Beez, Alba, and Roberts, M.J., 2006, 

Major Uses of Land in the United States, 

2002: U.S. Department of Agriculture Economic Research Service Economic Information Bulletin No. (EIB-14), 54 p., available 

at www.ers.usda.gov/publications/eib14/

Nakagaki, Naomi, and Wolock, D.M. 2005, 

Estimation of agricultural pesticide use in 

drainage basins using land cover maps and 

county pesticide data: U.S. Geological Survey Open-File Report 2005-1188, 46 p.

Petty, J.D., Huckins, J.N., Alvarez, D.A., Brumbaugh, W.G., Cranor, W.L., Gale, R.W., Rastall, A.C., Jones-Lepp, T.L., Leiker, T.J., Rostad, C.E., and Furlong, E.T., 2004, A holistic 

passive integrative sampling approach for 

assessing the presence and potential impacts 

of waterborne environmental contaminants: 

Chemosphere v. 54, p. 695-705. 

Schumacher, J.G., 2003, Survival, transport, and 

sources of fecal bacteria in streams and 

survival in land-applied poultry litter in the 

Upper Shoal Creek Basin, southwestern 

Missouri, 2001-2002: U.S. Geological Survey Water-Resources Investigations Report 

03-4243, 45 p.

Stackelberg, P.E., Gilliom, R.J., Wolock, D.M., and 

Hitt, K.J., 2005, Development and application 

of a regression equation for estimating the 

occurrence of atrazine in shallow ground 

water beneath agricultural areas of the United 

States: U.S. Geological Survey Scientific 

Investigations Report 2005-5287, 22 p.

Stafford, J.D., Kaminski, R.M., Reinecke, K.J., and 

Manley, S.W., 2006, Waste rice for waterfowl 

in the Mississippi Alluvial Valley: Journal of 

Wildlife Management, v. 70, p. 61-69.

Max M. Ethridge

 Regional Executive for Geography

 U.S. Geological Survey

 1400 Independence Road, MS234

 Rolla, MO 65401-2602

 methridge@usgs.gov

Janice R. Ward

 Senior Hydrologist

 U.S. Geological Survey

 Denver Federal Center, Box 25046, MS401

 Lakewood, CO 80225

 jward@usgs.gov

Elisabeth M. Brouwers

 Central Region Science Officer for Biology

 U.S. Geological Survey

 Denver Federal Center, Box 25046, MS300

 Lakewood, CO 80225

 brouwers@usgs.gov

Stoeckel, D.M., Mathes, M.V., Hyer, K.E., 

Hagedorn, Charles, Kator, Howard, Lukasik, Jerzy, O’Brien, T.L., Fenger, T.W., 

Samadpour, Mansour, Strickler, K.M., and 

Wiggins, B.A., 2004, Comparison of seven 

protocols to identify fecal contamination 

sources using Escherichia coli: Environmental Science and Technology, v. 38, no. 

22, p 6109-6117.

Swanson, G.A., 1987, An introduction to the Cottonwood Lake area: Proceedings of the North 

Dakota Academy of Science, v. 4, p. 25.

Tillitt, D.E., Papoulias, D.M., Whyte, J.J., and 

Richter, C.A., 2006, Effects of atrazine on 

reproductive function in fathead minnow 

(Pimephales promelas): The Society of 

Environmental Toxicology and Chemistry, 

27th annual meeting, abstracts volume, 

p. 383.

U.S. Department of Agriculture, 1987, Farm 

drainage in the United States: History, 

Status and Prospects: U.S. Department of 

Agriculture Economic Research Service 

Miscellaneous Publication 1455.

U.S. Department of Agriculture, 2001, Food 

and agricultural policy, taking stock for a 

new century: U.S. Department of Agriculture, 120 p.

U.S. Geological Survey, 1999, The Quality of 

Our Nation’s Waters—Nutrients and Pesticides: U.S. Geological Survey Circular 

1225, 82 p.

Vogelmann, J.E., Howard, S.M., Yang, L., Larson, C.R., Wylie, B.K., and VanDriel, N., 

2001, Completion of the 1990’s national 

land cover dataset for the conterminous 

United States from Landsat Thematic 

Mapper data and ancillary data sources: 

Photogrammetry Engineering and Remote 

Sensing, v. 67, p. 650–662.

Wiebe, Keith, and Golleron, Noel, eds., 2006, 

Agricultural Resources and Environmental 

Indicators, 2006 Edition: U.S. Department 

of Agriculture Economic Research Service 

Economic Information Bulletin No. EIB16, available at www.ers.usda.gov/publications/arei/eib16/

Winter, T.C., Harvey, J.W., Franke, O.L., Alley, 

W.M., 1998, Ground water and surface 

water—a single resource: U.S. Geological 

Survey Circular 1139, 79 p.

Winter, T.W., ed., 2003, Hydrological, chemical, and biological characteristics of a 

Prairie Pothole Wetland Complex under 

highly variable climate conditions—The 

Cottonwood Lake area, East-Central 

North Dakota: U.S. Geological Survey 

Professional Paper 1675, 109 p.

Contacts: