U.S. Department of the Interior

U.S. Geological Survey

Fact Sheet 2009–3064

Revised February 2012

In cooperation with the Louisiana Department of Transportation and Development 

Water Resources of St. Tammany Parish

D O TD

APED TR MENT OF TRANSPORTATION AND DEVELOPMENT

Bayou Lacombe

Mandeville

ST. TAMMANY 

PARISH

WASHINGTON

PARISH

Madisonville

M

I

S

S

I

S

S

I

P

P

I

90°15' 90°00' 89°45'

30°45'

30°30'

30°15'

TANGIPAHOA

PARISH

ST. JOHN THE 

BAPTIST 

PARISH

ST. CHARLES

PARISH

JEFFERSON

PARISH

ORLEANS

PARISH

89°30'

10 KILOMETERS

0 10 MILES

0

Slidell

Sun

Covington

Folsom

Abita 

Springs

Lacombe

Pearl 

River

Eden Isle

Hickory

Talisheek

A

A ́

ST-563

L O U I S I A N A A R K A N S A S

M I S S I S S I P P

T

I

E X A S

G U L F O F M E X I C O

ENLARGED AREA

Base modified from Official Map of Louisiana, Louisiana Department of Transportation and Development, 1986

Bogue

Chitto

Bogue

River

River

River

River

River

River

Falaya

Tchefuncte

Abita

Pearl

Pearl

West

Lake Pontchartrain

Lake

Borgne

The Rigolets

EXPLANATION

2,000 to 2,499

2,500 to 2,999

Approximate altitude of the base of 

 fresh groundwater, in feet below 

 National Geodetic Vertical Datum of 1929 

ST-563 Well for which hydrograph

 is shown (see fig. 4)

A A' Trace of hydrogeologic

 section (see fig. 3)

3,000 to 3,499

3,500 to 3,599

Introduction 

St. Tammany Parish, located in southeastern Louisiana 

(fig. 1), contains fresh groundwater and surface-water 

resources. In 2005, about 22.8 million gallons per day (Mgal/d) 

were withdrawn from water sources in St. Tammany Parish 

(fig. 2). Almost 100 percent (22.7 Mgal/d) was withdrawn 

from groundwater, and less than 1 percent (0.06 Mgal/d) was 

withdrawn from surface water (table 1). Withdrawals for public 

supplies accounted for 70 percent (16 Mgal/d) of the total 

water withdrawn (table 2). Withdrawals for domestic use were 

28 percent (6 Mgal/d). Generally, water withdrawals in the 

parish increased from 1960 to 1970, decreased from 1970 to 

1985, and again increased from 1985 to 2005 (fig. 2). 

This fact sheet summarizes basic information on the 

water resources of St. Tammany 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.

Figure 1. Location of study area, St. Tammany Parish, Louisiana.

Printed on recycled paper
natural flow into rivers, leakage into underlying aquifers, and 

withdrawal from wells. 

Fresh groundwater (water with a chloride concentration 

less than 250 milligrams per liter [mg/L]) is present from land 

surface to about 3,000 to 3,500 ft below National Geodetic 

Vertical Datum of 1929 (NGVD 29) in most of northern St. 

Tammany Parish (fig. 1) and to about 2,400 to 3,200 ft below 

NGVD 29 in southeastern parts of the parish; however, some 

intermediate sands at depths less than 2,500 ft near Lake 

Pontchartrain may contain saltwater (water with a chloride 

concentration that exceeds 250 mg/L). Freshwater from aquifers 

in St. Tammany Parish is soft (less than 60 mg/L, as calcium 

carbonate [CaCO3]) and generally does not exceed the U.S. 

Environmental Protection Agency’s (EPA) 2006 Secondary 

Maximum Contaminant Levels (SMCLs)1 for drinking water for 

chloride, iron, manganese, and dissolved solids. Some aquifers 

may contain iron or manganese concentrations that exceed the 

EPA’s SMCLs. 

Well-registration records from the Louisiana Department 

of Transportation and Development (DOTD) indicate that there 

are about 10,860 active wells screened in the aquifers in St. 

Tammany Parish, including about 9,740 domestic, 650 publicsupply, 430 irrigation, and 40 industrial wells. About 23 Mgal/d 

of groundwater was withdrawn in St. Tammany Parish in 2005, 

and most was for public-supply (16 Mgal/d) and domestic (6 

Mgal/d) use. 

The Chicot Equivalent Aquifer System

The Chicot equivalent aquifer system in St. Tammany 

Parish consists of two adjacent, near-surface aquifers: the 

upland terrace aquifer in the northern half of the parish and the 

upper Ponchatoula aquifer in the southern half of the parish. 

The base of the aquifer system ranges from about 0 to 500 ft 

below NGVD 29. 

In 2005, about 26 percent (6.0 Mgal/d) of the groundwater 

used in St. Tammany Parish was withdrawn from the Chicot 

equivalent aquifer system. Most of the water was withdrawn 

from the upland terrace aquifer (3.8 Mgal/d) and the upper 

Ponchatoula aquifer (2 Mgal/d). About 5.3 Mgal/d of the total 

groundwater withdrawn in this system were for domestic use, 

and about 0.6 Mgal/d were for public-supply use. 

The base of the Chicot equivalent aquifer system ranges 

from about 0 ft below NGVD 29 in northern St. Tammany 

Parish to 500 ft below NGVD 29 in the southern parts of 

the parish. Aquifers in the Chicot equivalent aquifer system 

typically consist of 50- to 300-ft-thick units of sand and gravel. 

The Chicot equivalent aquifer system contains waterbearing units throughout St. Tammany Parish. Aquifers in 

the system typically yield fresh water that is soft and does 

not exceed the EPA’s SMCLs (table 3). Water from aquifers 

in this system generally exceeds the SMCL for iron, and 

water from the upland terrace aquifer may exceed the SMCL 

for manganese. 

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

source in St. Tammany Parish, Louisiana, 2005 (Sargent, 2007).

Aquifer, aquifer system, 

or major water body Groundwater

Surface 

water

Chicot equivalent aquifer system 5.99

Evangeline equivalent aquifer system 12.32

Jasper equivalent aquifer system 4.39

Surface water bodies 0.06

Total 22.7 .06

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

category in St. Tammany Parish, Louisiana, 2005 (Sargent, 2007). 

Groundwater Surface 

water Total

Public supply 15.89 0 15.89

Industrial .14 0 .14

Power generation 0 0 0

Rural domestic 6.44 0 6.44

Livestock .06 .04 .11

Rice irrigation 0 0 0

General irrigation .13 .01 .15

Aquaculture .03 0 .03

Total 22.7 .06 22.76

Figure 2. Water withdrawals in St. Tammany Parish, Louisiana, 1960–2005.

0

10

20

30

40

Annual withdrawal,

 in million gallons per day

Groundwater

Surface water

1960

1965

1970

1975

1980

1985

1990

1995

2000

2005

Year

Groundwater Resources 

The groundwater resources of St. Tammany Parish, 

from near surface to deepest, include the Chicot equivalent 

aquifer system, the Evangeline equivalent aquifer system, and 

the Jasper equivalent aquifer system (fig. 3). Aquifers in the 

parish generally dip and thicken to the south. Recharge to the 

aquifers is from rainfall, leakage from overlying aquifers, and 

seasonal input from rivers. Discharge from the aquifers is by 
Covington aquifer

Slidell aquifer

Mandeville Slidell

Upper Ponchatoula aquifer

?

Big Branch aquifer

Abita aquifer

?

Lower Ponchatoula

aquifer

Chicot Equivalent

Aquifer System 

Evangeline Equivalent

Aquifer System 

Jasper Equivalent

Aquifer System

Lower Ponchatoula aquifer

Big Branch 

aquifer

Lower Ponchatoula

aquifer

Covington

aquifer

EAST

A'

WEST

A

Lower Ponchatoula aquifer

Bend in

Section

Bend in

Section

The Tchefuncte, Hammond, Amite, and Ramsay 

aquifers are not shown on this section.

FEET

200

-2,400

-2,200

-2,000

-1,800

NGVD 29

-200

-400

-600

-800

-1,000

-1,200

-1,400

-1,600

10 MILES

10 KILOMETERS

0

0

-2,800

-2,600

EXPLANATION

Clay

Freshwater in sand–

 dashed where approximate

VERTICAL SCALE GREATLY EXAGGERATED

Figure 3. Generalized west-to-east hydrogeologic section through St. Tammany Parish, Louisiana (Griffith, 

2003). Trace of section shown on figure 1.

About 9,300 wells are screened in the Chicot equivalent 

aquifer system, and most are used for domestic (8,505), publicsupply (406), irrigation (363), or industrial (22) purposes. 

Reported well yields from wells screened in the aquifer system 

generally range from about 3 to 80 gallons per minute (gal/min). 

The Evangeline Equivalent Aquifer System

The Evangeline equivalent aquifer system underlies the 

Chicot equivalent aquifer system and in St. Tammany Parish 

consists of, from near surface to deepest, the lower Ponchatoula, 

Big Branch, Abita, Covington, and Slidell aquifers. In 2005, 

about 54 percent (12.3 Mgal/d) of the groundwater used in 

the St. Tammany Parish was withdrawn from the Evangeline 

equivalent aquifer system. Most of the water was withdrawn 

from the Slidell aquifer (6.5 Mgal/d), the Abita aquifer (2.7 

Mgal/d), and the lower Ponchatoula aquifer (2.3 Mgal/d). 

About 10.4 Mgal/d of the total groundwater withdrawn in this 

system were for public-supply, and about 1.2 Mgal/d were 

for domestic use. 

The Evangeline equivalent aquifer system contains waterbearing units throughout St. Tammany Parish. The base of the 

aquifer system ranges from about 1,800 to possibly about 3,000 

ft below NGVD 29 south of Slidell. Aquifers in the Evangeline 

equivalent aquifer system typically consist of 50- to 200-ft-thick 

units of medium to very coarse sand. 

Freshwater from aquifers in the Evangeline equivalent 

aquifer system is typically soft and does not generally exceed 

the EPA’s SMCLs; however, some freshwater may contain 

iron and manganese concentrations that exceed those SMCLs 

(table 3). Saltwater is present in the Big Branch aquifer near 

Lacombe and the Lake Pontchartrain shoreline. 

About 10,860 wells are screened in the Evangeline 

equivalent aquifer system, and most are used for domestic 

(9,740), public-supply (654), irrigation (429), or industrial 

(38) purposes. Reported well yields from wells screened in the 

Evangeline equivalent aquifer system generally range from 

about 4 to 300 gal/min. 

Water levels in the lower Ponchatoula and Big Branch 

aquifers are about 20 to 35 ft above NGVD 29 and have 

declined by as much as about 0.3 ft per year from 1996 to 2005. 

Water levels in the Abita, Covington, and Slidell aquifers are 

about 50 to 70 ft above NGVD 29 and have declined by as 

much as about 1.3 ft per year from 1978 to 2005 (fig. 4). 
Table 3. Summary of selected water-quality characteristics for freshwater in the Chicot equivalent aquifer system and the Jasper and 

Evangeline equivalent aquifer systems in St. Tammany Parish, Louisiana, 1939–2007 (U.S. Geological Survey, 2008b). 

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

CaCO3, calcium carbonate; μg/L, micrograms per liter; 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

Chicot equivalent aquifer system

Median 22.4 10 256 7.1 12 6.8 165 80 171

10th percentile 21 0 40 5.4 4.7 3.1 <10 .8 43.8

90th percentile 25 50 584 8.6 24.6 27.2 1,085 170 275.6

Number of samples 46 16 41 27 48 50 18 21 17

Percentage of samples 

that meet SMCLs

NA 66 NA 45 NA 100 64 46 100

Jasper and Evangeline equivalent aquifer systems

Median 28.3 5 294.5 8.5 6 4 50 30 195

10th percentile 23 0 182.2 7 1 2.4 6 <10 145.1

90th percentile 34.6 35 634.8 9 20 25 855 190 394.4

Number of samples 100 76 108 81 104 131 66 60 72

Percentage of samples 

that meet SMCLs

NA 76 NA 48 NA 100 83 62 99

SMCLs

NA 15 NA 6.5–8.5 NA 250 300 50 500

Well: ST-563

Altitude of land surface: 10.24 ft above NGVD 29

Well depth: 2,411 ft below land surface

1950 1960 1970 1980 1990 2000 2010

Water level, in feet

below National Geodetic

Vertical Datum of 1929 (NGVD 29) 

Date

130

110

90

70

50

30

Figure 4. Water levels in well ST-563 screened in the Slidell aquifer in St. Tammany Parish, Louisiana (see fig. 1 for well location).

The Jasper Equivalent Aquifer System

The Jasper equivalent aquifer system underlies the 

Evangeline equivalent aquifer system and in St. Tammany 

Parish consists of, from shallowest to deepest, the Tchefuncte, 

Hammond, Amite, and Ramsay aquifers. In 2005 about 19 

percent (4.4 Mgal/d) of the groundwater used in St. Tammany 

Parish was withdrawn from the Jasper equivalent aquifer 

system. Most of the water was withdrawn from the Tchefuncte 

aquifer (1.9 Mgal/d), the Hammond aquifer (2.1 Mgal/d), and 

the Amite aquifer (0.4 Mgal/d). About 4.4 Mgal/d (almost 100 

percent) was withdrawn for public supply use. 

The base of the aquifer system ranges from 2,350 ft below 

NGVD 29 in northern areas of the parish to as deep as 3,300 
Table 4. Summary of selected water-quality characteristics for the Tchefuncte and Bogue Chitto Rivers in St. Tammany Parish, 

Louisiana, 1953–95. 

[Values are in milligrams per liter, except as noted. °C, 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)

Magnesium, 

filtered 

(as Mg)

Sodium, 

filtered 

(as Na)

Chloride, 

filtered 

(as Cl)

Sulfate, 

filtered 

(as SO4)

Iron, 

filtered

(μg/L 

as Fe)

Tchefuncte River below Covington1

Median 512 NA 6.5 38 6.1 2.6 53 126 16 40

10th percentile 57 NA 5.6 8 2 .3 5.3 5.9 1.8 10

90th percentile 2,102 NA 7 180 20 33 290 609.2 72 92

Number of samples 103 0 61 63 61 61 61 103 61 59

Percentage of samples 

that meet SMCLs

NA NA 55 NA NA NA NA 58 100 100

Bogue Chitto River near Bush2

Median 44 8.15 6.4 9 2 .9 4 6.1 2.1 200

10th percentile 36.9 7 5.9 7 1.6 .5 2.7 4.2 1 87.6

90th percentile 49 10 6.9 10.2 2.7 1.1 5.1 7.8 4.3 280

Number of samples 180 160 190 189 178 175 176 186 182 78

Percentage of samples 

that meet SMCLs

NA NA 45 NA NA NA NA 100 100 94

SMCLs

NA NA 6.5–8.5 NA NA NA NA 250 250 300

1

Station number 07375224 (U.S. Geological Survey, 2008b; specific data at http://nwis.waterdata.usgs.gov/la/nwis/qwdata/?site_no=07375224).

2

 Station number 02492000 (U.S. Geological Survey, 2008b; specific data at http://nwis.waterdata.usgs.gov/la/nwis/qwdata/?site_no=02492000).

ft below NGVD 29 near Covington. Aquifers in the Jasper 

equivalent aquifer system typically consist of 50- to 250-ft-thick 

units of fine to coarse sand and some pea gravel. 

The Jasper equivalent aquifer system contains waterbearing units throughout St. Tammany Parish. Saltwater is 

present in some of the aquifers in the system at and to the south 

of Slidell and Lacombe. Aquifers in the system typically yield 

freshwater that is soft and does not generally exceed the EPA’s 

SMCLs; however, some freshwater may exceed the SMCLs for 

pH, iron, and manganese (table 3). 

About 70 wells are screened in the Jasper equivalent 

aquifer system, and most are used for public-supply (32), 

domestic (22), or irrigation (9) purposes. Reported well yields 

from wells screened in the aquifer system generally range 

from about 90 to 1,830 gal/min. In 2006, water levels in the 

Jasper aquifer system generally ranged from about 100 ft above 

NGVD 29 in the northern part of the parish to about 70 ft above 

NGVD in the southern part of the parish. 

Surface-Water Resources 

Lake Pontchartrain and the Pearl, West Pearl, Tchefuncte, 

and Bogue Chitto Rivers are the primary sources of surface 

water in St. Tammany Parish. In 2005, about 0.06 Mgal/d of 

surface water was withdrawn in St. Tammany Parish; about 

0.04 Mgal/d were used for livestock, and about 0.01 Mgal/d 

were used for general irrigation. Other surface water resources 

in the parish include the Abita and Bogue Falaya Rivers. 

Although Lake Pontchartrain is a huge potential source of water 

for St. Tammany Parish, water in the lake is brackish to salty 

and would require treatment for most uses. 

The average discharge for the Pearl and West Pearl Rivers 

at the town of Pearl River was about 9,470 cubic feet per second 

(ft3/s) (6,120 Mgal/d) for the period 1964–70. Water in the Pearl 

and West Pearl Rivers is generally fresh, but during periods 

of low flow, saltwater has intruded 2 to 3 mi upstream from 

Lake Borgne. 

The average discharge for the Tchefuncte River near 

Folsom was about 159 ft3/s (103 Mgal/d) for the period 1944–

2007. Water in the Tchefuncte River is generally fresh, but 

during periods of low flow, saltwater has intruded from Lake 

Pontchartrain upstream to the City of Covington. Water in the 

Tchefuncte River generally is soft but may be moderately hard 

(61–120 mg/L as CaCO3) and slightly acidic (pH less than 6.5 

standard units) (table 4). 

The average discharge for the Bogue Chitto River near 

Bush was about 2,000 ft3/s (1,289 Mgal/d) for the period 1938–

2007. Analyses of water quality samples from the river indicate 

that the water is typically soft but may be slightly acidic and 

exceed the EPA’s SMCL for iron (table 4). 
By Jason M. Griffith 

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

References

Cardwell, G.T., Forbes, M.J., Jr., and Gaydos, M.W., 1967, Water 

resources of the Lake Pontchartrain area, Louisiana: Department 

of Conservation, Louisiana Geological Survey, and Louisiana 

Department of Public Works Water Resources Bulletin no. 12, 105 

p., 7 pls.

Griffith, J.M., 2003, Hydrogeologic framework of southeastern 

Louisiana: Louisiana Department of Transportation and 

Development Water Resources Technical Report no. 72, 21 p., 

18 pls.

Nyman, D.J., and Fayard, L.D., 1978, Ground-water resources of 

Tangipahoa and St. Tammany Parishes, southeastern Louisiana: 

Louisiana Department of Transportation and Development, Office of 

Public Works Water Resources Technical Report no. 15, 76 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 July 28, 2008, at http://streamstats.usgs.

gov/gages/viewer.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.