U.S. Department of the Interior

U.S. Geological Survey Open-File Report 2010–1229

Unintended Consequences of Biofuels Production: The Effects 

of Large-Scale Crop Conversion on Water Quality and Quantity

By Heather L. Welch, Christopher T. Green, Richard A. Rebich, Jeannie R.B. Barlow, and Matthew B. Hicks 

Printed on recycled paper

I

n the search for renewable fuel alternatives, biofuels have 

gained strong political momentum. In the last decade, 

extensive mandates, policies, and subsidies have been adopted 

to foster the development of a biofuels industry in the United 

States. The Biofuels Initiative in the Mississippi Delta resulted 

in a 47-percent decrease in cotton acreage with a concurrent 

288-percent increase in corn acreage in 2007. Because corn 

uses 80 percent more water for irrigation than cotton, and more 

nitrogen fertilizer is recommended for corn cultivation than 

for cotton, this widespread shift in crop type has implications 

for water quantity and water quality in the Delta. Increased 

water use for corn is accelerating water-level declines in 

the Mississippi River Valley alluvial aquifer at a time when 

conservation is being encouraged because of concerns about 

sustainability of the groundwater resource. Results from a 

mathematical model calibrated to existing conditions in the 

Delta indicate that increased fertilizer application on corn also 

likely will increase the extent of nitrate-nitrogen movement 

into the alluvial aquifer. Preliminary estimates based on 

surface-water modeling results indicate that higher application 

rates of nitrogen increase the nitrogen exported from the Yazoo 

River Basin to the Mississippi River by about 7 percent. Thus, 

the shift from cotton to corn may further contribute to hypoxic 

(low dissolved oxygen) conditions in the Gulf of Mexico.

Top photograph: Furrow irrigation of corn acreage in the 

Mississippi Delta. Photograph courtesy of the Mississippi State 

University Extension Service.

Bottom photograph: Water-level monitoring of an alluvial aquifer 

well in Bolivar County, Mississippi. Photograph by Michael A. 

Manning, U.S. Geological Survey.

Why has the Production of Biofuels Become 

Important?

Biofuels are fuels produced directly or indirectly from 

organic materials such as plants and animal waste. Corn-based 

ethanol is the most common type of biofuel produced in 

the United States—approximately 34 billion liters (L) were 

produced in 2008 (data accessed on June 7, 2010, at 

http://www.afdc.energy.gov/afdc/ethanol/production.html). 

Biofuels have received considerable support because they 

use renewable resources and have the potential to reduce 

greenhouse gas emissions. However, there are some environmental concerns attributed to the increase in corn acreage for 

biofuels production, such as the need for irrigation in some 

areas, the application of increased amounts of nitrogen fertilizers and water-soluble pesticides, and soil erosion from the 

tillage of crops (National Research Council of the National 

Academies, 2008). 
The Biofuels Initiative (BFI), which was implemented by 

the U.S. Department of Energy (DOE) Biomass Program in late 

2006, was developed by the DOE Office of Energy Efficiency 

and Renewable Energy to help meet the goals of the Energy 

Independence and Security Act (EISA; Public Law Number 

110-140). The goal of the EISA is to increase the production 

of renewable and alternative fuels and reduce dependence on 

foreign oil within the United States. Two primary goals for the 

BFI and Biomass Program are to (1) produce 230 billion L of 

ethanol to replace 30 percent of current gasoline levels by 2030 

and (2) reduce ethanol costs to prices that are competitive with 

gasoline by 2012. 

The Mississippi Delta—Consequences of Biofuels 

Production from a Local Perspective

The Yazoo River Basin is the largest river basin in Mississippi, with a drainage area of 34,590 square kilometers (km2

), 

and is divided equally between lowlands and highlands. An 

area referred to locally as the “Delta” covers about 18,130 km2

of the lowlands part of the Yazoo River Basin in northwestern 

Mississippi. The U.S. Geological Survey’s (USGS) National 

Water-Quality Assessment (NAWQA) Program has spent much 

of the last two decades studying the relation between agriculture 

and water quality and quantity in the Mississippi Delta (fig. 1). 

Because of fertile soils and a long growing season, about 

90 percent of the land is used for agriculture, including the 

cultivation of cotton, corn, rice, and soybeans. Although the 

climate is humid and subtropical, and the average rainfall ranges 

from 114 centimeters per year (cm/yr) in the north to 152 cm/yr 

in the south, about 28 percent of the rainfall occurs during the 

growing season (Snipes and others, 2005). Thus, irrigation is 

needed to maximize crop production. 

The primary source of water for irrigation in the region 

is the Mississippi River Valley alluvial (MRVA) aquifer—a 

relatively thin hydrogeologic unit with an average thickness of 

41 meters (m) and an areal extent of approximately 85,470 km2. 

The aquifer is composed of highly permeable layers of sand, 

gravel, and silt (with minor amounts of clay) that underlie parts 

of Arkansas, Louisiana, Mississippi, Missouri, and to a lesser 

extent Illinois, Kentucky, and Tennessee (fig. 1). In Mississippi, 

the aquifer is overlain by a relatively impervious clay layer, and 

therefore, only a small percentage of precipitation infiltrates 

the soils to directly recharge the aquifer. Estimates of recharge 

to the aquifer from precipitation range from 5.8 to 10.9 cm/yr 

(Arthur, 2001; Green and others, 2009; Welch and others, 2009). 

Because the Delta is a low, flat area with low permeability, 

the remaining precipitation is lost through evapotranspiration 

and to streamflow, which is supplemented by irrigation return 

flow during the summer months. During the winter, most of the 

runoff from rainfall drains into streams.

Approximately 15 million cubic meters per day (m3/d) of 

water are withdrawn from the MRVA aquifer during the May to 

August growing season in Mississippi, which makes it the most 

heavily used aquifer in the State (Maupin and Barber, 2005). 

Owing to the large amount of withdrawal, water levels in the 

aquifer have been declining since at least 1980. The average 

groundwater level has declined 0.1 meter per year (m/yr) or less 

in most areas, but has declined as much as 0.5 m/yr in some 

areas. Overall, the total volume of water stored in the aquifer 

has declined since 1980 (Arthur, 2001), and current withdrawals 

from the alluvial aquifer exceed recharge. From October 1987 

to October 2009, there was an average annual loss in storage of 

approximately 355 million cubic meters (m3) from the MRVA 

aquifer in the Mississippi Delta (Mark Stiles, Yazoo Mississippi 

Delta Joint Water Management District, written commun., 2010; 

fig. 2). 

Figure 1. Areal extent of the Mississippi River Valley alluvial aquifer 

and the location of the Mississippi Delta in northwestern Mississippi.

Figure 2. Annual (October-to-October) change in storage of the 

Mississippi River Valley alluvial aquifer in the Mississippi Delta, 

2002–2009. Red line denotes the 22-year average change in storage 

for the aquifer (Mark Stiles, Yazoo Mississippi Delta Joint Water 

Management District, written commun., 2010).

MISSISSIPPI

ARKANSAS

TN

0 25 50 MILES

0 25 50 KILOMETERS

Mississippi River Valley 

alluvial aquifer

EXPLANATION

MO

IL

KY

TN

AR

LA

MS

boundary

Delta

Mississippi 

Yazoo River Basin

91 90

35

33

Scale 1:100,000

Albers conic equal-area projection

Jackson Pearl

Mississippi

River

River

Vicksburg

Greenville

Clarksdale

Yazoo

City

Memphis

Greenwood

2002 2003 2004 2005 2006 2007 2008 2009

OCTOBER-TO-OCTOBER CHANGE IN STORAGE,

IN MILLION CUBIC METERS

1,500

1,000

500

0

–500

–1,000

–1,500

2
Increased Withdrawals for Corn and Soybeans 

Are Accelerating Groundwater Declines in the 

MRVA Aquifer 

Withdrawals from the MRVA aquifer have increased due 

to market-driven land conversion from cotton to corn and 

soybeans. The increase in corn prices driven by demand for 

ethanol-based biofuels resulted in a 47-percent reduction in 

cotton acreage concurrent with a 288-percent increase in corn 

acreage in 2007 relative to 2006 (fig. 3). From 2007 to 2009, 

corn acreage decreased by 21 percent and soybean acreage 

increased by 46 percent in response to rising demand for soybeans to replace corn as feed for livestock (fig. 3). Groundwater 

withdrawal rates (and application rates) for a particular crop 

vary from year to year, depending on weather conditions, irrigation methods, and other factors. For example, withdrawals for 

corn increased from 219 million m3 in 2006 to 566 million m3 

in 2007, whereas withdrawals for cotton decreased from 855 to 

282 million m3 during this same period. Although corn acreage 

increased in 2007, groundwater application rates (withdrawal 

volume per unit land area in production) were about 30 percent 

lower in 2007 than in 2006 because of timely precipitation 

(fig. 3; table 1). Because soybean production uses nearly as 

much water as corn production, the 2008 to 2009 shift in 

crop further increased the demand for groundwater from the 

MRVA aquifer.

Withdrawal rates for cotton production ranged from 

0.09 million cubic meters per square kilometer per year 

(m3/km2/yr) in 2004 to 0.25 million m3/km2/yr in 2006 (table 1). 

The average annual withdrawal rate from 2002 to 2009 was 

0.15 million m3/km2/yr for cotton, 0.22 million m3/km2/yr for 

soybeans, and 0.27 million m3/km2/yr for corn (table 1; Yazoo 

Mississippi Delta Joint Water Management District, 2009). 

Based on these averages, which normalize withdrawals for 

inter-annual differences in weather, converting 1 km2 of cotton 

to 1 km2 of corn results in a 0.12 million m3/km2/yr increase 

in withdrawals from the MRVA aquifer. Corn production in 

the Delta increased from 598 km2 in 2006 to 2,321 km2 in 

2007, while cotton production fell from 3,505 km2 in 2006 

to 1,853 km2 during the same period (fig. 3; http://www.

nass.usda.gov/Statistics_by_State/Mississippi/index.asp; 

accessed April 10, 2010). Assuming that about 1,652 km2

of cotton were converted to corn between 2006 and 2007, 

the additional increase in groundwater withdrawn, based on 

the measured 2007 application rates, was 165 million m3. 

A similar analysis for the entire 2008 through 2009 period, 

including changes in soybean production, indicates that an 

additional 270 million m3 of water were withdrawn from the 

MRVA aquifer from 2008 through 2009 as a result of crop 

conversions—a total of 435 million m3 more groundwater 

withdrawn for the entire 2007 to 2009 period.

Two scenarios for the volume of change in storage of the 

MRVA aquifer from 2007 to 2009 indicate that the conversion from cotton to corn and soybean acreage increased 

storage loss in the MRVA aquifer. A change in water 

withdrawals for cotton, corn, and soybeans was calculated 

for 2007 to 2009, using average withdrawal rates (table 1), 

in reference to 2006, the year prior to the large-scale crop 

conversion. In 2007, storage loss in the aquifer would have 

been approximately 250 million m3 if the conversion from 

cotton to corn acreage had not occurred (fig. 4). In 2008, 

storage loss in the aquifer would have been approximately 

210 million m3 if the conversion from cotton to corn and 

soybean acreage had not occurred (fig. 4). A slight increase 

in storage of 18 million m3 occurred in 2009 because of 

decreased groundwater withdrawals during the growing 

season as a result of timely rainfall. However, potential 

storage would have been 189 million m3 if further increases 

in total acreage for soybean and corn, relative to 2006 levels, 

had not occurred (fig. 4).

Figure 3. Crop acreage and total growing season precipitation in the 

Mississippi Delta, 2002–2009.

Table 1. Groundwater withdrawal rates for cotton, corn, and 

soybean acreage in the Mississippi Delta, 2002–2009.

[Source: Yazoo Mississippi Delta Joint Water Management District (2009). 

All values are in million cubic meters per square kilometer per year]

Year Cotton Corn Soybeans

2002 0.15 0.28 0.22

2003 0.15 0.19 0.19

2004 0.09 0.12 0.12

2005 0.15 0.31 0.19

2006 0.25 0.37 0.31

2007 0.15 0.25 0.25

2008 0.19 0.37 0.31

2009 0.09 0.25 0.19

8-year average 0.15 0.27 0.22

Cotton acreage

Corn acreage

Soybean acreage

Growing season

precipitation,

May to August

2002 2003 2004 2005 2006 2007 2008 2009

ACREAGE, IN SQUARE KILOMETERS

GROWING SEASON PRECIPITATION, IN CENTIMETERS

7,000

6,000

5,000

4,000

3,000

2,000

1,000

0

70

60

50

40

30

20

10

0

3
Increased Agrichemical Application Rates Have Affected 

Groundwater Quality

The USGS developed a mathematical advection-reaction 

water-quality model for a study site in the Delta to investigate 

changes in fertilizer application rates resulting from an increase 

in corn production and corresponding decrease 

in cotton production. The model was calibrated 

to existing conditions to assess fluxes of water 

and chemicals from agricultural fields to 

groundwater (Green and others, 2009; Welch 

and others, 2009). As with many other agricultural sites across the country, nitrate-nitrogen 

(N) contamination was found in shallow 

groundwater as a result of the leaching of 

chemical nitrogen (fig. 5). At this site, nitrate-N 

was absent in samples at depths of 4.4 m below 

the water table and deeper due to a biodegradation reaction known as denitrification. The depth 

of leached nitrate-N was controlled largely 

by the slow downward movement of water, 

which is a function of soil properties, and the 

annual nitrogen fertilizer application rate to 

the overlying farm fields. Because of the link 

between fertilizer application rates and the 

degree of nitrogen contamination in groundwater, potential changes in nitrogen application 

rates in response to crop conversion for biofuels 

production have important implications for 

groundwater quality in the Mississippi Delta.

The results of a mathematical model indicate that increased 

nitrogen fertilization due to additional corn production will 

expand the area of nitrate-N contamination of groundwater in 

Mississippi Delta groundwater. Figure 5 shows two hypothetical 

scenarios for future agriculture and water quality. In scenario 1, 

the crop types and fertilizer application in the Delta remain at 

2006 levels (fig. 5B). Nitrogen fertilizer application rates for 

this scenario are based on county agricultural chemical use 

from 1960 to 2008 (U.S. Department of Agriculture, 2010). 

Under scenario 1, steady-state conditions are reached after 

35 years, at which point predicted nitrate-N concentrations 

exceed the U.S. Environmental Protection Agency Maximum 

Contaminant Level (MCL) of 10 milligrams nitrate-N per liter 

(U.S. Environmental Protection Agency, 2006) in the upper 2 

m of groundwater, and nitrate-N is transported to a maximum 

depth of 7 m below the water table (fig. 5A). Once steady-state 

conditions are reached, the maximum depth of contamination 

remains at 7 m because the rate of downward transport reaches 

equilibrium with the rate of denitrification. In scenario 2, 

an increase in corn production results in a rapid increase in 

nitrogen application rates to 269 kilograms nitrate-N per hectare 

per year based on recommended fertilizer application rates from 

the Delta Planning Budget for corn acreage in Mississippi (fig. 

5B; Mississippi State University Department of Agricultural 

Economics, 2009). Under this scenario, steady-state conditions 

are reached after 95 years, at which point nitrate-N concentrations in ground-water are much higher than in scenario 1 and 

exceed the MCL up to 14 m below the water table. Nitrate-N 

migrates downward to a maximum depth of 18 m below the 

water table. Other hydrologic factors not considered in the 

model could result in an increase in the depth of migration of 

nitrate-N in the aquifer. For example, downward groundwater 

velocities could increase as a result of increased withdrawals.

Figure 5. Two model scenarios for future agricultural practices and resulting water 

quality at the study site in the Mississippi Delta: (A) measured (indicated by green 

squares) and simulated nitrate-nitrogen concentrations in groundwater at various 

depths below the water table, and (B) fertilizer application for both scenarios over 

time. Scenario 1 assumes crop acreage and fertilizer application remain at 2006 levels, 

whereas scenario 2 is an immediate conversion to 100 percent of the recommended 

nitrogen application rate for corn. 

Figure 4. October-to-October change in Mississippi River Valley 

alluvial aquifer storage that can be attributed to the crop conversion 

from cotton to corn and soybeans, 2007–2009. For 2007, only the crop 

conversion from cotton to corn is considered.

Change in aquifer storage without crop conversion from

 cotton to corn and soybeans

Change in aquifer storage with crop conversion from 

cotton to corn and soybeans

Average change in storage, 1987–2009

2007 2008 2009

500

400

300

200

100

0

–100

–200

–300

–400

–500

OCTOBER-TO-OCTOBER CHANGE IN STORAGE, IN MILLION CUBIC METERS

A B

0

2

4

6

8

10

12

14

16

18

20

scenario 1

scenario 2

Exceeds U.S. Environmental

Protection Agency Maximum

Contaminant Level

DEPTH BELOW WATER TABLE, IN METERS

0 10 20 30 40 50

NITRATE-NITROGEN CONCENTRATION,

IN MILLIGRAMS PER LITER

0

300

250

200

150

100

50

1940 1960 1980 2000 2020 2040

NITROGEN APPLICATION RATE,

IN KILOGRAMS PER HECTARE PER YEAR

scenario 1

scenario 2

4
Nitrogen Export to the Gulf of Mexico Has Increased

Since at least 1980, a hypoxic zone has formed during the 

summer in the Gulf of Mexico off the coast of Louisiana. The 

zone has increased in size since measurements began in the 

early 1980s, and its extent is positively related to the annual 

amount of nitrogen entering the Gulf from the Mississippi River 

(Rabalais and others, 2002). 

The USGS developed the SPAtially Referenced Regressions on Watershed attributes (SPARROW) model to relate 

water-quality measurements to contaminant sources and 

environmental factors that affect both the rates of delivery of 

compounds to streams and their rates of in-stream processing. 

SPARROW has been used to identify the watersheds that are the 

largest contributors of nitrogen to the Gulf of Mexico, which 

includes the Yazoo River Basin (fig. 6; Robertson and others, 

2009). Using regional SPARROW model estimates of both the 

nitrogen application rates and the loss rates for nitrogen for the 

Yazoo River Basin, the conversion of cotton to corn acreage 

(comparing 2002 with 2007) is estimated to have caused a 

7 percent increase in the nitrogen load for the Yazoo River 

(Richard A. Rebich, U.S. Geological Survey, written commun., 

2010). Significant increases in nutrient inputs tied to changes 

in cropping patterns could mask any progress toward meeting 

the 45-percent nutrient reduction target by 2015 as specified by 

the Mississippi River/Gulf of Mexico Watershed Nutrient Task 

Force (2008). 

Figure 6. The extent of the Mississippi/Atchafalaya River Basin 

watersheds and total nitrogen delivered to the Gulf of Mexico from the 

basin. The Yazoo River Basin lies within the bold blue line (Robertson 

and others, 2009; kg-N/km2/yr, kilograms nitrate-nitrogen per square 

kilometer per year).

Figure 7. Annual minimum mean daily flow at the Big Sunflower 

River at Sunflower, Mississippi, showing decline in baseflow most 

evident since groundwater withdrawals from the Mississippi River 

Valley alluvial aquifer increased in the late 1980s. Data are missing 

for 1998 to 2002. 

Figure 8. A Delta stream that is nearly dry during the 

summer because of loss of baseflow. Photograph by Matt 

Hicks, U.S. Geological Survey, September 25, 2007.

Stream Ecosystem Health Is Affected by Declining Water 

Quality and Quantity in Delta Streams

Groundwater input to a stream during periods of low 

rainfall is essential to stream ecosystem health because it 

maintains baseflow, regulates stream temperature, and generally 

is of higher quality than surface-water runoff. Prior to the rapid 

expansion of corn acreage in response to the BFI, baseflow in 

some Delta streams had been declining in recent years because 

of declining water levels in the MRVA aquifer (fig. 7), and some 

stream reaches have remained dry (or nearly so) for months in 

the summer and fall during periods of low rainfall (fig. 8). 

Most streams in the Delta have been hydrologically 

altered, and about 75 percent of the original forested wetlands 

have been cleared or drained, thus changing ecosystem structure 

and function (Creasman and others, 1992). A presumed 

decline in ecosystem health in Delta streams prior to 2007 is 

evidenced by a loss of habitat complexity and structure and a 

change in metabolic dynamics resulting from increased water 

temperatures and decreased dissolved oxygen levels (Kleiss 

and others, 2000). Continued declines in ecosystem health have 

led to further biodiversity losses through substantial changes in 

biological community assemblages and the increasing prevalence of more tolerant, but less desirable, species. The continued 

expansion of corn and soybean acreage in the Delta is expected 

to exacerbate the stresses on stream ecosystems primarily by 

(1) reducing groundwater inflow to streams—a change with 

particularly acute consequences during periods of low flow 

during the summer, and (2) increasing nutrient input to streams 

through increased fertilizer use. DISCHARGE, IN CUBIC METERS PER SECOND

4.5

4.0

3.5

3.0

2.5

2.0

1.5

1.0

0.5

0

9/25/19559/25/1961

9/25/19679/25/19739/25/19799/25/19859/25/19919/25/1997

9/25/2003

12/09/2007

5
Summary—How Has the Biofuels Initiative 

Affected Conditions in the Mississippi Delta? 

• Higher groundwater withdrawals associated with the 

conversion of cotton to corn and soybean crops have 

exacerbated already declining water levels in the Mississippi River Valley alluvial (MRVA) aquifer leading 

to further loss of baseflow in most Delta streams.

• Results from a mathematical water-quality model 

indicate that an increase of nitrogen fertilizer application to rates recommended for corn could increase 

nitrate-N contamination in much of the MRVA aquifer 

to levels that exceed the U.S. Environmental Protection Agency Maximum Contaminant Level. Maintaining fertilization rates at 2006 levels will result in only 

a minor increase in nitrate-N contamination. 

• Increased fertilizer application rates on corn have 

increased slightly (about 7 percent) the export of 

nitrogen from the Mississippi Delta to the Mississippi 

River and, ultimately, to the Gulf of Mexico where it 

may further exacerbate the hypoxic zone.

Mississippi River/Gulf of Mexico Watershed Nutrient Task 

Force, 2008, Gulf hypoxia action plan 2008 for reducing, 

mitigating, and controlling hypoxia in the northern Gulf of 

Mexico and improving water quality in the Mississipi River 

Basin, accessed May 5, 2010, at http://www.epa.gov/

owow_keep/msbasin/pdf/ghap2008_update082608.pdf.

Mississippi State University Department of Agricultural 

Economics, 2009, Delta 2010 planning budgets: Budget 

Report 2009–06, 185 p.

National Research Council of the National Academies, 2008, 

Water implications of biofuels production in the United 

States: Washington, DC, The National Academies Press, 61 p.

Rabalais, N.N., Turner, R.E., Wiseman, W.J., Jr., 2002, Gulf of 

Mexico hypoxia, a.k.a. “The Dead Zone”: Annual Review of 

Ecological Systems, v. 33, p. 235–263. 

Robertson, D.M., Schwarz, G.E., Saad, D.A., and Alexander, 

R.B., 2009, Incorporating uncertainty into the ranking of 

SPARROW model nutrient yields from Mississippi/Atchafalaya River Basin watersheds: Journal of the American Water 

Resources Association, v. 45, no. 2, p. 534–549.

Snipes, C.E., Nichols, S.P., Poston, D.H., Walker, T.W., Evans, 

L.P., and Robinson, H.R., 2005, Current agricultural practices of the Mississippi Delta: Mississippi Agricultural and 

Forestry Experiment Station Bulletin 1143, 18 p.

U.S. Department of Agriculture, 2010, Economic Research Service Fertilizer Consumption and Use, accessed January 29, 

2010, at http://www.ers.usda.gov/Data/FertilizerUse/.

U.S. Environmental Protection Agency, 2006, 2006 edition of 

the drinking water standards and health advisories: U.S. Environmental Protection Agency, EPA-822-R-06-013.

Welch, H.L., Green, C.T., and Coupe, R.H., 2009, The fate and 

transport of nitrate through the unsaturated zone at a site 

in northwestern Mississippi [abs.], in Geological Society 

of America 2009 Annual Meeting: Geological Society of 

America Abstracts with Programs, v. 41, no. 7, p. 29. 

Yazoo Mississippi Delta Joint Water Management District, 

2009, Irrigation water use in the Mississippi Delta 2009 

report, accessed April 10, 2010, at http://www.ymd.org/pdfs/

wateruse/2009%20Mississippi%20Delta%20Irrigation%20

Water%20Use%20Report.pdf.

Additional Information

For additional information about the Biofuels Initiative and (or) the 

Mississippi Delta contact: 

U.S. Geological Survey

Mississippi Water Science Center

308 South Airport Road

Jackson, MS 39208-6649

http://ms.water.usgs.gov

References Cited

Arthur, J.K., 2001, Hydrogeology, model description, 

and flow analysis of the Mississippi River alluvial 

aquifer in northwestern Mississippi: U.S. Geological 

Survey Water-Resources Investigations Report 01–4035, 

47 p.

Creasman, L., Craig, N.J., and Swan, M., 1992, The forested 

wetlands of the Mississippi River—An ecosystem in 

crisis: Baton Rouge, Louisiana, The Nature Conservancy, 

23 p.

Green, C.T., Welch, Heather, and Coupe, Richard, 2009, 

Multi-tracer analysis of vertical nitrate fluxes in the 

Mississippi River Valley alluvial aquifer [abs.], in Eos 

Transactions of the American Geophysical Union, v. 90, 

no. 52, H31C-0799.

Kleiss, B.A., Coupe, R.H., Gonthier, G.J., and Justus, B.G., 

2000, Water quality in the Mississippi Embayment, 

Mississippi, Louisiana, Arkansas, Missouri, Tennessee, 

and Kentucky, 1995–1998: U.S. Geological Survey 

Circular 1208, 36 p.

Maupin, M.A., and Barber, N.L., 2005, Estimated withdrawals from the principal aquifers in the United States, 2000: 

U.S. Geological Survey Circular 1279, 46 p.

U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2010

For product and ordering information:

http://www.usgs.gov/pubprod

Telephone: 1-888-ASK-USGS