Fact Sheet 2013–3061

September 2013

U.S. Department of the Interior

U.S. Geological Survey

Prepared in cooperation with the Louisiana Department of Transportation and Development 

Water Resources of Assumption Parish, Louisiana

Introduction 

Information concerning the availability, use, and quality 

of water in Assumption Parish, Louisiana (fig. 1), is critical for 

proper water-supply management. The purpose of this fact sheet 

is to present information that can be used by water managers, 

parish residents, and others for management of this vital 

resource. Information on the availability, past and current use, 

use trends, and water quality from groundwater and surfacewater sources in the parish is presented. Previously published 

reports (see Cited References section) and data stored in the 

U.S. Geological Survey’s National Water Information System 

(http://waterdata.usgs.gov/nwis) are the primary sources of the 

information presented here. 

In 2010, about 21.4 million gallons per day (Mgal/d) of 

water were withdrawn in Assumption Parish, including about 

12.4 Mgal/d from surface-water sources and 9.03 Mgal/d from 

groundwater sources1

 (table 1). Withdrawals for industrial 

use accounted for about 16.4 Mgal/d or 76 percent of the total 

water withdrawn (table 2). Other categories of use included 

public supply, rural domestic, livestock, general irrigation, 

and aquaculture (Sargent, 2011). Water-use data collected at 

5-year intervals from 1960 to 2010 (fig. 2) indicated that water 

withdrawals peaked in 2000 at about 29.7 Mgal/d. 

1

Tabulation of numbers in text and tables may result in different totals 

because of rounding; nonrounded numbers are used for calculation of totals. 

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

Paincourtville

Napoleonville

Donaldsonville

Belle Rose

Pierre

 Part

Thibodaux

Labadieville

Lake

Verret

ASSUMPTION PARISH

ASCENSION

PARISH

TERREBONNE PARISH

ST. MARTIN PARISH

SAINT MARY

PARISH

ST. MARY

IBERIA PARISH

IBERVILLE PARISH

LAFOURCHE

PARISH

SAINT JAMES PARISH

ST. JAMES

30°00'

29°50'

29°40'

91°10'

91°00'

90°50'

0 5 10 KILOMETERS

0 5 10 MILES

EXPLANATION

Area where Mississippi

 River alluvial aquifer

 contains saltwater—

 Water with a chloride

 concentration greater 

 than 250 milligrams

 per liter

Approximate altitude of 

 base of fresh groundwater,

 in feet below National Geodetic

 Vertical Datum of 1929 (modified 

 from Cardwell and others, 1965)—

 Freshwater contains 250 milligrams

 per liter or less of chloride

 100 to 199

 200 to 299

 300 or deeper

07381002

07380400

Surface-water discharge

 site and number

Surface-water quality site

 and number

Base modified from U.S Geological Survey digital data

Universal Transverse Mercator, zone 15

North American Datum of 1983

TEXAS

ARKANSAS MISSISSIPPI

LOUISIANA

ASSUMPTION

PARISH

1

90

398

70

Bayou Lafourche

Grand Bayou

Bayou Lafourche

Mississippi Riv e rMississippi Riv e r

Lake

Palourde

Grassy

Lake

07380401

295500091100000

07381002

Figure 1. Location of study area, Assumption Parish, Louisiana.
Table 1. Water withdrawals, in million gallons per day, by source 

in Assumption Parish, Louisiana, 2010 (modified from Sargent, 

2011).

Aquifer or

surface-water body Groundwater Surface water

Mississippi River

alluvial aquifer

6.81

Norco aquifer 2.22

Bayou Lafourche 10.08

Lake Verret 1.99

Other water bodies 0.31

Total 9.03 12.39

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

category in Assumption Parish, Louisiana, 2010 (modified from 

Sargent, 2011).

Category of use Groundwater Surface 

water Total

Public supply 0.00 3.90 3.90

Industrial 8.59 7.79 16.37

Rural domestic 0.18 0.00 0.18

Livestock 0.00 0.01 0.01

General irrigation 0.07 0.11 0.19

Aquaculture 0.19 0.58 0.76

Total 9.03 12.39 21.42

Groundwater

Surface water

EXPLANATION

Year

Annual withdrawal, in million gallons per day

0

5

10

15

20

25

30

1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010

Figure 2. Water withdrawals in Assumption Parish, Louisiana, 1960–2010.
Groundwater Resources 

The Mississippi River alluvial aquifer (the shallowest 

aquifer underlying Assumption Parish) is the primary source 

of fresh groundwater (water with a chloride concentration of 

250 milligrams per liter [mg/L] or less) in the parish. Deeper 

aquifers underlying the parish, including the Norco aquifer, 

contain only saltwater (water with a chloride concentration 

greater than 250 mg/L). Recharge to aquifers in the parish is 

from infiltration of precipitation; lateral leakage from adjacent 

aquifers; and seasonal flow from rivers, canals, and lakes to the 

aquifers. Discharge from the aquifers is by natural flow into 

rivers, canals, and lakes; lateral leakage into adjacent aquifers; 

and withdrawals from wells. 

State well-registration records listed 72 active water wells 

in Assumption Parish in 2009, including 33 industrial, 20 

general irrigation, and 19 rural-domestic wells. Withdrawals 

from the Mississippi River alluvial aquifer were about 6.81 

Mgal/d and 2.22 Mgal/d came from the deeper Norco aquifer 

(table 1). Industrial use accounted for about 95 percent of 

groundwater withdrawals; less than 5 percent was withdrawn 

for domestic use, general irrigation, and aquaculture (table 2). 

Mississippi River Alluvial Aquifer 

The Mississippi River alluvial aquifer is present throughout 

Assumption Parish but contains freshwater only in the north 

and central parts of the parish in an area extending southward 

from the northern parish line to the town of Labadieville in 

the eastern part of the parish (fig. 1). The base of freshwater in 

the Mississippi River alluvial aquifer extends from about 300 

feet (ft) below the National Geodetic Vertical Datum of 1929 

(NGVD 29) in the north to about 100 ft below NGVD 29 in the 

south. The aquifer generally is composed of fine to medium 

sand at the top and grades to coarse sand and gravel at the base 

(Tomaszewski, 2003). A clayey surficial confining unit overlies 

the alluvial aquifer. 

North of the town of Paincourtville, along Bayou 

Lafourche (fig. 1), the Mississippi River alluvial aquifer 

contains mostly freshwater with only 5–10 ft of saltwater at 

its base. The proportion of saltwater to freshwater increases 

southward and laterally away from Bayou Lafourche. Locally, 

the chloride concentration can increase in wells pumped for 

prolonged periods at rates of 500 gallons per minute [gal/min] 

and greater as saltwater is drawn upwards from the base of the 

aquifer (Cardwell and others, 1965). 

State well-registration records listed 68 active water 

wells screened in the Mississippi River alluvial aquifer in 

Assumption Parish in 2009, including 29 industrial, 20 general 

irrigation, and 19 rural-domestic wells. Well depths ranged from 

158 to 315 ft below land surface with a median depth of 212 ft. 

Reported yields from wells screened in the Mississippi River 

alluvial aquifer underlying Assumption Parish have ranged 

from about 20 to 2,870 gal/min. In 2010, about 6.81 Mgal/d 

were withdrawn from the Mississippi River alluvial aquifer in 

Assumption Parish, including about 6.37 Mgal/d for industrial 

use, 0.18 Mgal/d for rural-domestic use, 0.07 Mgal/d for general 

irrigation, and 0.19 Mgal/d for aquaculture. 

Regionally throughout its extent, the Mississippi River 

alluvial aquifer contains water of a calcium bicarbonate type, 

which is hard to very hard.2

 Iron concentrations in the water 

usually are high, generally exceeding the U.S. Environmental 

Protection Agency’s (USEPA) Secondary Maximum 

Contaminant Level (SMCL)3

 of 0.3 μg/L for drinking water 

(Tomaszewski, 1992). In Assumption Parish, manganese 

concentrations in water from the alluvial aquifer generally 

exceed the SMCL of 0.05 mg/L (Tomaszewski, 1992). 

A statistical summary of selected water-quality characteristics for freshwater samples collected from 30 wells screened 

in the Mississippi River alluvial aquifer in Assumption Parish is 

listed in table 3. Based on median values of constituents, freshwater from the aquifer generally exceeds the SMCL for color. 

The pH of the water is generally within the SMCL range of 

6.5–8.5 standard units. Hardness ranges widely but is generally 

moderately hard or very hard. 

Norco Aquifer

The Norco aquifer contains only saltwater in Assumption 

Parish but provided water for industrial purposes in 2010. In 

Assumption Parish, the Norco aquifer is separated from the 

overlying Mississippi River alluvial aquifer by a clay or silty 

clay bed ranging from 10 to 50 feet in thickness. The base of 

the Norco aquifer has an average depth of about 600 ft below 

NGVD 29 within the parish (Cardwell and others, 1965). The 

aquifer generally contains fine to coarse sand and may contain 

fine gravel in some places (Tomaszewski, 2003). 

State well-registration records listed four active water 

wells screened in the Norco aquifer in Assumption Parish in 

2009. The four wells, classified for industrial use, have depths 

ranging from 533 to 561 ft below land surface. Water-quality 

data available from samples from two of the wells, located 

about 3 miles west of Paincourtville (fig. 1), indicated that water 

from the Norco aquifer is very hard and chloride concentrations 

are greater than 700 mg/L. In 2010, about 2.22 Mgal/d were 

withdrawn from the Norco aquifer in Assumption Parish for 

industrial use. 

2

Hardness ranges, expressed as milligrams per liter of calcium carbonate, are 

as follows: 0–60, soft; 61–120, moderately hard; 121–180, hard; greater than 

180, very hard (Hem, 1985). 3

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 constituent concentrations or values, 

health implications as well as aesthetic degradation may be present. SMCLs 

were established as guidelines for the states by the U.S. Environmental 

Protection Agency (1992).
Table 3. Summary of selected water-quality characteristics for freshwater in the Mississippi River alluvial aquifer in Assumption 

Parish, Louisiana (U.S. Geological Survey, 2012a).

[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; —, insufficient data; NA, not applicable; SMCL, Secondary Maximum Contaminant Level established 

by the U.S. Environmental Protection Agency (2012)]

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)

Mississippi River alluvial aquifer, 1939–93 (30 wells)

Median 20.5 30 923 7.3 180 68 654

10th percentile 19.5 14 777 6.8 94 23 —

90th percentile 22.0 95 1,150 7.7 350 150 —

Number of samples 11 16 14 14 30 30 2

Percentage of samples 

that do not exceed 

SMCLs

NA 12.5 NA 93 NA 100 50

SMCLs

NA 15 NA 6.5 - 8.5 NA 250 300

Surface-Water Resources 

In 2010, about 12.4 Mgal/d of surface water were 

withdrawn in Assumption Parish for public-supply, industrial, 

livestock, general irrigation, and aquaculture uses (table 2). 

Most surface water withdrawn by industry is used for cooling 

purposes and returned to its source after use (Sargent, 2011). 

Bayou Lafourche and Lake Verret (fig. 1) are principal sources 

of fresh surface water in Assumption Parish.

 Bayou Lafourche is supplied by water from the 

Mississippi River at Donaldsonville. The bayou flows through 

southwestern Ascension Parish, northeastern Assumption 

Parish, and into Lafourche Parish (fig. 1). Bayou Lafourche 

was a distributary channel of the Mississippi River until 

February 23, 1904, when flow from the river was cut off by 

a dam at Donaldsonville to alleviate flooding. The dam cut 

off nourishment and replenishment to a large area of coastal 

wetlands and turned Bayou Lafourche into a stagnant channel. 

In 1955, a pumping plant at Donaldsonville began diverting 

about 250 cubic feet per second (ft3

/s) from the Mississippi 

River into Bayou Lafourche by a combined siphoning and 

pumping operation (Cardwell and others, 1965). During the 

period 1996–2013, the average daily discharge for Bayou 

Lafourche southwest of Donaldsonville (station 07380401) 

(fig. 1) was about 224 ft3/s (145 Mgal/d). The maximum daily 

discharge was 399 ft3/s (258 Mgal/d) and the minimum daily 

discharge was -107 ft3

/s (-69.2 Mgal/d) (U.S. Geological 

Survey, 2013). In 2010, about 10.1 Mgal/d were withdrawn 

from Bayou Lafourche in Assumption Parish, including about 

3.90 Mgal/d for public supply, 5.99 Mgal/d for industrial use, 

and 0.19 Mgal/d for aquaculture. 

Water samples analyzed during the period 1996–99 

indicated that water in Bayou Lafourche below the weir at 

Thibodaux in neighboring Lafourche Parish is generally 

hard and does not exceed SMCLs for pH or concentrations 

of chloride, sulfate, and iron (table 4). Dissolved oxygen 

concentration is generally greater than 5 mg/L, which is 

considered the minimum value for a diversified population 

of fresh, warmwater biota, including sport fish (Louisiana 

Department of Environmental Quality, 2008). 

Lake Verret has an area of about 22 square miles and 

is primarily used for recreation and commercial fishing 

(Shampine, 1970). In 2010, about 1.99 Mgal/d were withdrawn 

from Lake Verret in Assumption Parish, including 1.80 Mgal/d 

for industrial use and 0.19 Mgal/d for aquaculture. 

Water in Lake Verret is a calcium-bicarbonate type and 

is highly colored (Cardwell and others, 1965). Water samples 

collected during the period 1975–86 indicated that water in 

Lake Verret near Pierre Part is generally moderately hard (from 

61 to 120 mg/L as calcium carbonate) and does not exceed the 

SMCLs for chloride, sulfate, and iron concentrations (table 4). 

The pH of the water usually does not exceed the SMCL but 

occasionally may exceed 8.5 standard units. Dissolved oxygen 

concentration is generally greater than 5 mg/L. 
Table 4. Summary of selected water-quality characteristics for Bayou Lafourche below weir at Thibodaux, Louisiana, and Lake Verret 

near Pierre Part, La.

[Values are in milligrams per liter, except as noted. μS/cm, microsiemens per centimeter;°C, degrees Celsius; 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 (2012)]

Specific

conductance,

field

(μS/cm

at 25 oC)

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)

Bayou Lafourche below weir at Thibodaux, 1996–991

Median 429 6.5 7.6 150 39 12 21 26 46 <10

10th percentile 337 5.0 7.3 140 36 11 12 14 36 <10

90th percentile 510 10.0 7.9 180 46 15 30 33 58 10

Number of samples 9 8 10 11 11 11 10 10 11 8

Percentage of samples 

that do not exceed 

SMCLs

NA NA 100 NA NA NA NA 100 100 100

Lake Verret near Pierre Part, 1975–862

Median 325 9.0 7.8 110 30 9.1 19 25 24 <10

10th percentile 216 5.9 6.8 74 20 5.9 9.9 13 11 <10

90th percentile 382 12.8 8.8 130 35 12 26 33 39 40

Number of samples 34 33 34 34 34 34 34 33 34 5

Percentage of samples 

that do not exceed 

SMCLs

NA NA 79 NA NA NA NA 100 100 100

 SMCLs 

NA NA 6.5 - 8.5 NA NA NA NA 250 250 300

1

Station number 07381002 (U.S. Geological Survey 2012b; specific data available at http://nwis.waterdata.usgs.gov/la/nwis/qwdata/?site_no=07381002).

2

Station number 295500091100000 (U.S. Geological Survey 2012c; specific data available at http://nwis.waterdata.usgs.gov/la/nwis/qwdata/?site_

no=295500091100000).

Cited References 

Cardwell, G.T., Sloss, Raymond, and Duncan, A.C., 1965, Water, in

Assumption Parish resources and facilities: Louisiana Department of 

Public Works and Assumption Parish Development Board, p. 25–38. 

Hem, J.D., 1985, Study and interpretation of the chemical 

characteristics of natural water (3d ed.): U.S. Geological Survey 

Water-Supply Paper 2254, 264 p., accessed February 20, 2013, at 

http://pubs.er.usgs.gov/publication/wsp2254.

Louisiana Department of Environmental Quality, 2008, Environmental 

Regulatory Code, Title 33, Part IX, Subpart 1, accessed June 9, 

2009, at http:www.deq.louisiana.gov/portal/tabid/1674/Default.aspx.

Sargent, B.P., 2011, Water use in Louisiana, 2010: Louisiana 

Department of Transportation and Development Water Resources 

Special Report no. 17, 133 p. 

Shampine, W.J., 1970, Gazetteer of Louisiana lakes and reservoirs: 

Louisiana Department of Public Works Basic Records Report no. 4, 

31 p. 

Tomaszewski, D.J., 1992, Louisiana hydrologic atlas map no. 

5: Quality of freshwater in aquifers of Louisiana, 1988: U.S. 

Geological Survey Water-Resources Investigations Report 90–4119, 

7 sheets, accessed August 2, 2012, at http://pubs.er.usgs.gov/

publication/wri904119. 

Tomaszewski, D.J., 2003, Ground-water resources along the lower 

Mississippi River, southeastern Louisiana: Louisiana Department of 

Transportation and Development Water Resources Technical Report 

no. 69, 23 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 September 28, 2011, at http://water.epa.gov/drink/

contaminants/secondarystandards.cfm. 

U.S. Environmental Protection Agency, 2012, 2012 Edition of the 

drinking water standards and health advisories: U.S. Environmental 

Protection Agency publication EPA 822-S-12-001, Office of Water, 

12 p., accessed July 27, 2012, at http://water.epa.gov/action/

advisories/drinking/upload/dwstandards2012.pdf. 

U.S. Geological Survey, 2012a, Water quality samples for Louisiana: 

National Water Information System Web Interface, accessed June 

23, 2009, at http://nwis.waterdata.usgs.gov/la/nwis/qwdata/. 

U.S. Geological Survey, 2012b, Water Quality Samples for Louisiana 

[data for USGS 07381002 Bayou Lafourche below weir at 

Thibodaux, LA]: Nation Water Information System Web Interface, 

accessed June 23, 2009, at http://nwis.waterdata.usgs.gov/la/nwis/

qwdata/?site_no=07381002. 

U.S. Geological Survey, 2012c, Water Quality Samples for Louisiana 

[data for USGS 295500091100000 Lk Verret nr Pierre Part, LA]: 

Nation Water Information System Web Interface, accessed June 

23, 2009, at http://nwis.waterdata.usgs.gov/la/nwis/qwdata/?site_

no=295500091100000. 

U.S. Geological Survey, 2013, StreamStats data-collection 

station report [data for site 07380401 Bayou Lafourche SW of 

Donaldsonville, LA]: accessed August 26, 2013, at http://ssdev.

cr.usgs.gov/gagepages/html/07380401.htm. 

By Lawrence B. Prakken and John K. Lovelace 

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.

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