U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2010–3048

Revised July 2011

In cooperation with the Louisiana Department of Transportation and Development 

Water Resources of Lafayette Parish

D O TD

APED TR MENT OF TRANSPORTATION AND DEVELOPMENT

Figure 1. Location of study area, Lafayette Parish, Louisiana.

Introduction

Fresh groundwater and surface water resources are 

available in Lafayette Parish, which is located in south-central 

Louisiana (fig. 1). In 2005, more than 47 million gallons per 

day (Mgal/d) were withdrawn from water sources in Lafayette 

Parish (table 1). About 92 percent (43.7 Mgal/d) of withdrawals 

was groundwater, and 8 percent (3.6 Mgal/d) was surface water 

(table 2). Public-supply withdrawals accounted for nearly 49 

percent (23 Mgal/d) of the total groundwater use, with the cities 

of Lafayette and Carencro using about 21 Mgal/d. Withdrawals 

for other uses included about 10.4 Mgal/d for rice irrigation 

and about 8.4 Mgal/d for aquaculture. Water withdrawals in 

Lafayette Parish increased from 33 Mgal/d in 1995 to about 47 

Mgal/d in 2005 (fig. 2).

This fact sheet summarizes information on the water 

resources of Lafayette Parish, La. Information on groundwater 

and surface-water availability, quality, development, use, and 

trends is based on previously published reports listed in the 

references section.
Groundwater Resources 

The primary groundwater resources of Lafayette Parish 

include the Chicot aquifer system and the Atchafalaya aquifer 

(fig. 3). The Chicot aquifer system is divided into four sand 

units: the shallow sand, the undifferentiated sand, the upper 

sand, and the lower sand. The upper and lower sands merge near 

the northern parish line and form the undifferentiated sand. The 

limited extent and lack of data on water use and water quality 

for the undifferentiated sand in Lafayette Parish preclude further 

discussion. Groundwater withdrawals by category are listed 

in table 2.

The base of fresh groundwater generally ranges from about 

700 to 999 feet (ft) below the National Geodetic Vertical Datum 

of 1929 (NGVD 29) (sea level), with depths greater than 1,000 

ft in central parts of the parish (fig. 1). Recharge to aquifers is 

from rainfall in outcrop areas northwest of Lafayette Parish, 

infiltration from the Atchafalaya River into the Atchafalaya 

aquifer, vertical leakage through surficial clays, and to a 

lesser extent, upward leakage from the underlying Evangeline 

aquifer. Discharge from the aquifers is by natural flow into 

rivers, leakage into underlying aquifers, and withdrawal from 

wells. State well-registration records indicate that in 2009 there 

were about 4,800 active wells in Lafayette Parish, including 

4,028 domestic, 361 public-supply, 321 irrigation, and 80 

industrial wells.

Shallow Aquifers

The shallow aquifers in Lafayette Parish consist of the 

shallow sand of the Chicot aquifer system and the Atchafalaya 

aquifer. Most of the parish is underlain by a shallow or nearsurface clay layer known as the Chicot surficial confining 

unit. Within the surficial confining unit, scattered sand lenses 

are present and are collectively called the shallow sand of the 

Chicot aquifer system. These scattered sands 

are generally less than 20-ft thick. In 2009, 

there were about 110 active wells screened in 

the shallow sand in Lafayette Parish, and all 

were used for domestic purposes. Withdrawal 

estimates for the shallow sand were not available.

The Atchafalaya aquifer is located along the 

eastern edge of Lafayette Parish and primarily 

consists of coarse sand with interbedded layers 

of gravel. Well yields in the aquifer range from 

4 to 150 gallons per minute (gal/min). The 

Atchafalaya aquifer and the Chicot aquifer 

system (upper sand) are hydraulically connected 

in the eastern part of the parish. Water levels 

in the Atchafalaya aquifer change with the 

Atchafalaya River stage and are generally higher 

near the river, causing water to move down 

gradient to the west, toward Lafayette Parish 

and into the Chicot aquifer system. In 2009, 

there were about 120 active wells screened in 

the Atchafalaya aquifer in Lafayette Parish, and 

all were used for domestic purposes. In 2005, 

withdrawals from the Atchafalaya aquifer were 

about 0.57 Mgal/d.

YEAR

196019651970

197519801985

1990

1995

20002005

A

N

N

U

AL WIT

H

D

R

AW

AL,

IN

MILLIO

N

G

ALLO

N

S

PER

D

AY

0

10

20

30

40

50

Surface water

Groundwater

Figure 2. Water withdrawals in Lafayette Parish, La., 1960–2005.

Table 2. Water withdrawals, in million gallons per day, by 

category in Lafayette Parish, La., 2005 (Sargent, 2007).

Groundwater Surface water Total

Public supply 22.98 0.00 22.98

Industrial 0.53 0.00 0.53

Power generation 1.69 0.00 1.69

Rural domestic 2.99 0.00 2.99

Livestock 0.16 0.00 0.16

Rice irrigation 8.48 1.92 10.40

General irrigation 0.14 0.02 0.16

Aquaculture 6.73 1.68 8.41

Total 43.70 3.62 47.32

Table 1. Water withdrawals, in million gallons per day, by source 

in Lafayette Parish, La., 2005 (Sargent, 2007).

Aquifer, aquifer system, or 

major water body Groundwater

Surface

water

Atchafalaya aquifer 0.57

Chicot aquifer system 43.13

Bayou Queue de Tortue 1.19

Vermilion River 1.19

Other water bodies 1.24

Total 43.70 3.62
0

0

10 MILES

10 KILOMETERS

5

5

NGVD 29

-200

-400

-600

-800

-1,000

-1,200

FEET

200

Chicot aquifer upper sand unit

EAST

A’

WEST

A

Chicot aquifer lower sand unit

Chicot aquifer lower sand unit

Atchafalaya aquifer

Land Surface

Broussard

Vermilion

River

Vertical datum is National Geodetic Vertical Datum of 1929 (NGVD 29)

Shallow sand

Chicot aquifer

surficial confining unit

Bayou Ile

des Cannes

EXPLANATION

Mostly clay

Freshwater in sand

Saltwater in sand

Figure 3. Generalized west-to-east hydrogeologic section through Lafayette Parish, La. (modified from Lovelace, 1999). Trace of section 

shown on figure 1.

Few water-quality data were available for the shallow 

aquifers in Lafayette Parish; however, in the shallow sand in 

St. Landry and St. Martin Parishes, located north and east of 

Lafayette Parish, iron concentrations generally exceed 5,000 

micrograms per liter (μg/L), and hardness often exceeds 250 

milligrams per liter (mg/L), which is considered very hard. 

Specific conductance and pH values in the shallow sand in 

St. Landry and St. Martin Parishes are similar to values in the 

upper sand of the Chicot aquifer system.

Upper Sand

The upper sand of the Chicot aquifer system in Lafayette 

Parish consists mostly of coarse sand, grading to gravel near 

the base of individual beds. The sand beds are generally 

several hundred feet thick and are separated in places by thick, 

discontinuous clays. Reported well yields in the upper sand have 

been as high as 3,500 gal/min, but most yields (93 percent) were 

less than 1,000 gal/min. Water levels in the upper sand generally 

fluctuate a few feet seasonally, as shown in the hydrograph for 

well Lf-662 (fig. 4), located in the city of Lafayette. Water levels 

declined about 8–10 ft during the period 1999–2001. This decline 

may be due to decreased rainfall and increased withdrawals 

from nearby wells during this period (Don Broussard, Lafayette 

Utilities System, oral comm., December 2008).

A summary of selected water-quality characteristics of 

samples from the upper sand is provided in table 3. Water from 

the upper sand ranges in hardness from soft (60 milligrams 

per liter [mg/L] or less as calcium carbonate [CaCO3]) to 

very hard (greater than 180 mg/L as CaCO3) but in general is 

moderately hard (61–120 mg/L as CaCO3). The water tends to 

be slightly acidic (pH < 7.0) but generally does not exceed the 

U.S. Environmental Protection Agency’s Secondary Maximum 

Contaminant Levels (SMCLs)1 for drinking water for pH and 

color, as well as concentrations of chloride, iron, and dissolved 

solids. Locally, iron concentrations can greatly exceed the 

SMCL of 300 μg/L. Manganese concentrations generally 

exceed the SMCL of 50 μg/L.

State well-registration records indicate that in 2009 there 

were about 4,000 active wells screened in the upper sand of the 

Chicot aquifer system. Of these 4,000 wells, about 3,400 were 

used for domestic purposes.

1

The SMCLs are nonenforceable Federal guidelines regarding cosmetic 

effects (such as tooth or skin discoloration) or aesthetic effects (such as taste, 

odor, or color) of drinking water. At high concentrations or values, health 

implications as well as aesthetic degradation might exist. SMCLs were 

established as guidelines for the States by the U.S. Environmental Protection 

Agency (1992).
Table 3. Summary of selected water-quality characteristics of freshwater in the upper and lower sand units of the Chicot aquifer system in 

Lafayette Parish, La. (U.S. Geological Survey, 2008b).

[Values are in milligrams per liter, except as noted. oC, degrees Celsius; PCU, platinum cobalt units; μS/cm, microsiemens per centimeter; SU, standard units; 

CaCO3, calcium carbonate; μg/L, micrograms per liter; <, less than; NA, not applicable; SMCL, Secondary Maximum Contaminant Level established by the U.S. 

Environmental Protection Agency (2006)]

Temperature 

(°C)

Color,

(PCU)

Specific

conductance, 

field

(μS/cm at 25°C)

pH,

field

(SU)

Hardness 

(as CaCO3)

Chloride,

filtered 

(as Cl)

Iron, 

filtered 

(μg/L as 

Fe)

Manganese, 

filtered

(μg/L as Mn)

Dissolved 

solids, 

filtered

Upper sand unit of the Chicot aquifer system, 1937–2007

Median 21.0 5 298 6.8 100 7.8 30 170 195

10th percentile 19.6 0 128 6.0 34 3.4 <10 1 106

90th percentile 22.9 15 490 7.4 180 19 2,300 730 276

Number of samples 53 21 62 60 65 66 53 45 60

Percentage of samples 

that do not

exceed SMCLs

NA 90 NA 68 NA 100 60 36 97

Lower sand unit of the Chicot aquifer system, 1958–1983

Median 23.5 5 450 7.5 140 11 560 90 287

10th percentile 22.1 0 365 7.0 60 3.4 96 16 234

90th percentile 24.4 15 730 8.0 180 53 760 110 455

Number of samples 13 24 25 25 26 26 24 17 26

Percentage of samples 

that do not

exceed SMCLs

NA 96 NA 96 NA 100 29 18 92

SMCLs

NA 15 NA 6.5–8.5 NA 250 300 50 500

YEAR

1980 1985 1990 1995 2000 2005 2010

W

ATER LEVEL, IN FEET

BELOW LAND SURFACE

40

42

44

46

48

50

52

54

56

No data

Well: Lf-662

Altitude of land surface: 40.37 ft above NGVD 29

Well depth: 152 ft below land surface

Figure 4. Water levels in well Lf-662 screened in the Chicot aquifer system, upper sand unit, in Lafayette Parish, La. (see fig. 1 for well 

location; U.S. Geological Survey, 2008a). Land surface is measured in feet above the National Geodetic Vertical Datum of 1929 (NGVD 29).
 Lower Sand

In Lafayette Parish, the lower sand of the Chicot aquifer 

system is hydrologically similar to the upper sand of the Chicot 

aquifer system. The base of the lower sand contains saltwater 

(greater than 250 mg/L chloride) throughout the parish. In 

2009, about 30 active wells were screened in the lower sand 

in Lafayette Parish. Well yields in the lower sand in the parish 

ranged from 16 to 4,000 gal/min.

Recent water-level data are not available for the lower sand 

of the Chicot aquifer system in Lafayette Parish. Water levels 

at wells screened in the lower sand in adjacent Acadia and 

St. Martin Parishes declined during the mid to late 1990s but 

remained relatively stable from about 2000 to 2009.

A summary of selected water-quality characteristics of 

freshwater in the lower sand is provided in table 3. Water from 

the lower sand is generally hard (hardness of 121–180 mg/L 

as CaCO3). The water generally does not exceed the SMCLs 

for pH and color, as well as for concentrations of chloride and 

dissolved solids. Iron and manganese concentrations generally 

exceed their SMCLs of 300 μg/L and 50 μg/L.

Surface-Water Resources

The Vermilion River and Bayou Queue de Tortue are 

primary sources of fresh surface water in Lafayette Parish (fig. 

1). In 2005, about 3.6 Mgal/d of surface water was withdrawn 

in Lafayette Parish, including about 1.9 Mgal/d for rice 

irrigation and 1.7 Mgal/d for aquaculture (table 2). Other major 

streams in the parish include Bayou Carencro and Bayou Ile 

des Cannes (fig. 1). About 1.2 Mgal/d of water was withdrawn 

from Bayou Queue de Tortue in 2005. No water-quality data 

were available for the stream. 

 In 2005, about 1.2 Mgal/d of water was withdrawn from 

the Vermilion River. The average discharge for the Vermilion 

River at Perry (U.S. Geological Survey station number 

07386980), located downstream from Lafayette Parish in 

adjacent Vermilion Parish (fig. 1), is 1,013 cubic feet per second 

(655 Mgal/d).

Analysis of water samples collected between 1983 and 

1986 from the Vermilion River (table 4) indicate that, in 

general, the water is soft to moderately hard and generally 

does not exceed SMCLs for pH and for concentrations of 

chloride, sulfate, and iron. Dissolved oxygen concentrations are 

generally low (less than 5 mg/L).

References

Lovelace, J.K., 1999, Distribution of saltwater in the Chicot aquifer 

system of southwestern Louisiana, 1995–96: Louisiana Department 

of Transportation and Development Water Resources Technical 

Report no. 66, 61 p.

Nyman, D.J., 1984, The occurrence of high concentrations of chloride 

in the Chicot aquifer system of southwestern Louisiana: Louisiana 

Department of Transportation and Development, Office of Public 

Works Water Resources Technical Report no. 33, 75 p.

Nyman, D.J., 1989, Quality of water in freshwater aquifers in 

southwestern Louisiana: Louisiana Department of Transportation and 

Development Water Resources Technical Report no. 42, 22 p., 28 pls.

Nyman, D.J., Halford, K.J., and Martin, Angel, Jr., 1990, 

Geohydrology and simulation of flow in the Chicot aquifer system 

of southwestern Louisiana: Louisiana Department of Transportation 

and Development Water Resources Technical Report no. 50, 58 p.

Table 4. Summary of selected water-quality characteristics for the Vermilion River at State Highway 3073 in Lafayette, La., 1983–86.

[Values are in milligrams per liter, except as noted. oC, degrees Celsius; μS/cm, microsiemens per centimeter; SU, standard units; μg/L, micrograms per liter; 

CaCO3, calcium carbonate; NA, not applicable; SMCL, Secondary Maximum Contaminant Level established by the U.S. Environmental Protection Agency (2006)]

Specific 

conductance, 

field

(μS/cm at

25°C)

Oxygen, 

dissolved

pH,

field

(SU)

Hardness

(as 

CaCO3)

Calcium, 

filtered

(as Ca)

Manesium, 

filtered

(as Mg)

Sodium, 

filtered

(as Na)

Chloride, 

filtered

(as Cl)

Sulfate, 

filtered

(as SO4)

Iron,

filtered

(μg/L

as Fe)

Vermilion River, 1983–861

Median 143 5.3 7.1 43 11 4.0 10 12 10 190

10th percentile 87 3.7 6.2 27 7.1 2.2 5.5 6.0 5.2 140

90th percentile 193 6.9 7.6 62 16 5.4 16 19 16 250

Number of 

samples

13 13 13 13 13 13 13 13 13 3

Percentage of 

samples that 

do not exceed 

SMCLs

NA NA 100 NA NA NA NA 100 100 100

SMCLs

NA NA 6.5–8.5 NA NA NA NA 250 250 300

1

Station number 07386935 (http://nwis.waterdata.usgs.gov/la/nwis/qwdata/?site_no=07386935&). 
By Robert B. Fendick, Jr., Jason M. Griffith, and

Lawrence B. Prakken

For additional information, contact: 

Director, USGS Louisiana Water Science Center

3535 S. Sherwood Forest Blvd., Suite 120

Baton Rouge, LA 70816

E-mail: dc_la@usgs.gov

Fax: (225) 298-5490

Telephone: (225) 298-5481

Home Page: http://la.water.usgs.gov

Prakken, L.B., 2003, Quality of water used for domestic supply in 

the Chicot aquifer system of southwestern Louisiana, 1994–2001: 

Louisiana Department of Transportation and Development Water 

Resources Technical Report no. 71, 48 p.

Prakken, L.B., and Wright, L.S., 2009, Water withdrawals and trends in 

ground-water levels and stream discharge in Louisiana, 1996–2005. 

Louisiana Department of Transportation and Development, Water 

Resources Technical Report no. 79, 49 p.

Sargent, B.P., 2007, Water use in Louisiana, 2005: Louisiana 

Department of Transportation and Development Water Resources 

Special Report no. 16, 133 p.

U.S. Environmental Protection Agency, 1992, Secondary Drinking 

Water Regulations—guidance for nuisance chemicals: U.S. 

Environmental Protection Agency publication EPA 810/K-92-001, 

4 p., accessed July 29, 2009, at http://www.epa.gov/safewater/

consumer/2ndstandards.html.

U.S. Environmental Protection Agency, 2006, 2006 Edition of the 

drinking water standards and health advisories: Washington, D.C., 

U.S. Environmental Protection Agency, Office of Water, 12 p.

U.S. Geological Survey, 2008a, Ground-water levels for Louisiana: 

U.S. Geological Survey digital dataset, accessed May 22, 2008, at 

http://nwis.waterdata.usgs.gov/la/nwis/gwlevels.

U.S. Geological Survey, 2008b, Water-quality samples for Louisiana: 

U.S. Geological Survey digital dataset, accessed May 22, 2008, at 

http://nwis.waterdata.usgs.gov/la/nwis/qwdata.

U.S. Geological Survey, 2008c, StreamStats: U.S. Geological Survey 

digital dataset, accessed December 5, 2008, at http://streamstats.

usgs.gov/gagepages/HTML/07386980.htm.

This fact sheet was published by the U.S. 

Geological Survey, in cooperation with the Louisiana 

Department of Transportation and Development 

(DOTD). Thanks are given to Zahir “Bo” Bolourchi, 

Director, Water Resources Programs, Louisiana 

Department of Transportation and Development, who 

contributed to the content and design of the fact sheet.