1.  Water-level data used to construct the potentiometric-surface map of the massive, upper, and “200-foot” sands of the Chicot aquifer system, June 2000

[Aquifer code: 112CHCT, massive sand; 112CHCTU, upper sand; and 11202LC, “200-foot” sand. --, no data] 

Figure 4.  Water levels in the Chicot aquifer system for wells Ev-229 (Evangeline Parish), Ac-326 (Acadia Parish), and JD-485A (Jefferson Davis Parish).

8�6��'(3$570(17�2)�7+(�,17(5,25

8�6��*(2/2*,&$/�6859(<

/RXLVLDQD�*URXQG�:DWHU�0DS�1R�����

3RWHQWLRPHWULF�6XUIDFH�RI�WKH�&KLFRW�$TXLIHU�6\VWHP�LQ�6RXWKZHVWHUQ�/RXLVLDQD��-XQH�����

-RKQ�.��/RYHODFH��&��3DXO�)UHGHULFN��-DUHG�:��)RQWHQRW��DQG�0�6��1DDQHV

By

����

:$7(5�5(6285&(6�,19(67,*$7,216�5(3257��������

/RYHODFH��-�.���)UHGHULFN��&�3���)RQWHQRW��-�:���DQG��1DDQHV��0�6���������/RXLVLVQD�*URXQG�:DWHU�0DS�1R�����

3RWHQWLRPHWULF�6XUIDFH�RI�WKH�&KLFRW�$TXLIHU�6\VWHP�LQ�6RXWKZHVWHUQ�/RXLVLDQD��-XQH�����

3UHSDUHG�LQ�FRRSHUDWLRQ�ZLWK�WKH

/28,6,$1$�67$7(�81,9(56,7<�$*5,&8/785$/�&(17(5

&223(5$7,9(�(;7(16,21�6(59,&(�$1'�7+(

/28,6,$1$�5,&(�5(6($5&+�%2$5'

INTRODUCTIONThe Chicot aquifer system is the principal source of fresh ground water in 

southwestern Louisiana.  Figure 1 shows the extent of freshwater in the Chicot aqui-fer system in southwestern Louisiana and areas where rice usually is grown; rice irrigation is a major use of water from the aquifer system.  In 1995, approximately 550 Mgal/d of water were withdrawn from the Chicot aquifer system (Lovelace and Johnson, 1996, p. 90).  Withdrawals have lowered water levels in the Chicot aquifer system, creating an elongated cone of depression in the water-level surface over much of the region (Zack, 1971, p. 7-9 and pl. 2).

During the first six months of 2000, rainfall in southwestern Louisiana averaged 19.4 in., which was 8.4 in. below the long-term average, and rainfall in south-central Louisiana averaged 14.4 in., which was 14.2 in. below the long-term average (Louisiana Office of State Climatology, 2000).  Much of southwestern Lou-isiana was in a moderate to severe drought as categorized by the long-term Palmer Drought Severity Index (National Oceanic and Atmospheric Administration Cli-mate Prediction Center, 2000).  Because of the lack of freshwater flushing that nor-mally occurs after precipitation, saltwater from the Gulf of Mexico intruded into many coastal streams and canals that normally are used for irrigation during the rice-growing season, making them unusable for irrigation (Louisiana State Univer-sity Agricultural Center, 2000).

  In 1995, about 565 Mgal/d of water were withdrawn from ground and sur-face sources for rice irrigation in southwestern Louisiana.  Of these withdrawals, approximately 250 Mgal/d were supplied from surface sources, and 315 Mgal/d were supplied from the Chicot aquifer system (Lovelace and Johnson, 1996), which was more than one-half of the total water withdrawn from the aquifer system.  Esti-mates of the amount of water required for rice cultivation in southwest Louisiana range from 32 to 46 in. of water per acre of rice field during the primary growing season (February through June).  During an average year, about half of this water is supplied by precipitation and half is supplied by irrigation (Covay and others, 1992, p. 6).  Data from a survey of farmers conducted during May 2000 indicated a wide-spread increase in per-acre application of ground water from the Chicot aquifer sys-tem for rice irrigation during the 2000 growing season (B.P. Sargent, U.S. Geological Survey, written commun., Dec. 2000), presumably due to the below-nor-mal rainfall.  Zack (1971) showed that the amount of ground water withdrawn in southwestern Louisiana in any particular year is inversely proportional to the total rainfall during the rice-growing season.

Additional knowledge about ground-water flow and effects of increased withdrawals on the Chicot aquifer system are needed to assess ground-water-devel-opment potential and to protect the resource. To meet this need, the U.S. Geological Survey (USGS), in cooperation with the Louisiana State University Agricultural Center Cooperative Extension Service and the Louisiana Rice Research Board, established a study to monitor water-level changes in wells completed within the Chicot aquifer system and to evaluate changes in the potentiometric surface (water levels).  Results are to be reported periodically; this is the first such report.

This report presents a map and data that describe the potentiometric surface of the massivJune 2000.  Hsystem are prof ground-wathe ground-wRouge, La.

The 9,000 mi2 aneron, EvangeSt. Mary, Verand temperateture is about 2Atmospheric tivation is theplanted in sou2000).

The numerous pubto be measureHoward CormLouisiana Coland owners aauthors thankDepartment owas used to s

The Chicot aquifer system underlies most oparts of the Texas coastal lowlands.  The aquifer sysilt, sand, and gravel interlayered with deposits of ctowards the south and southeast. The sand deposits sand and gravel to finer sediments and become incrunits. The Chicot aquifer system also thickens eastwRiver area, and is hydraulically connected to alluviaand Mississippi Rivers (Nyman, 1984, p. 4).

The Chicot aquifer system has been dividedana based on the occurrence of major clay units.  Inarea, the aquifer system is comprised mainly of a siimate southern boundary of the massive sand is shomassive sand, from eastern parts of Calcasieu and Claya River, the aquifer includes upper and lower san1963, p. 10).  In central and western Calcasieu and aquifer is subdivided into the “200-,” “500-,” and “their depths of occurrence in the Lake Charles area foot” sand is stratigraphically equivalent to, and conFigure 2 shows a partial hydrogeologic column of aana.

Recharge to the Chicot aquifer system occudeposits crop out in southern Rapides and Vernon PBeauregard, and Evangeline Parishes (fig. 1).  In thesandy soil and moves slowly downdip toward pointrecharge is supplied from vertical leakage downwarthrough underlying clay confining units, and from athe Atchafalaya River, which are laterally adjacent and others, 1990, p. 14).  A computer simulation ofthat, under 1981 conditions, more than 90 percent oaquifer system is withdrawn by wells, and 65 percerice-growing area originated as infiltrated precipitatp. 33).

Evangeline Parish

Ev- 23 303521 923250 112CHCT 51.06 360 6-1 104.19 -53.13

Ev- 79 303727 922657 112CHCT 55.00 250 6-1 125.66 -70.66

Ev- 229 304120 922630 112CHCT 65.66 231 6-1 109.56 -43.90

Ev- 500 305130 922636 112CHCT 117.52 120 6-1 50.16 67.36

Ev- 547 304745 922045 112CHCT 113.38 80 6-1 52.60 60.78

Ev- 606 304111 921629 112CHCT 75.00 255 6-27 104.84 -29.84

Ev- 623 305036 922058 112CHCT 137.20 96 6-1 68.86 68.34

Ev- 665 304435 921845 112CHCT 59.29 100 6-1 71.80 -12.51

Ev- 667 305055 923306 112CHCT 122.20 91.5 6-1 48.39 73.81

Ev- 673 303800 922504 112CHCT 60.00 247 6-1 128.32 -68.32

Ev- 679 305335 921835 112CHCT 46.00 70 6-1 7.34 38.66

Ev- 680 305714 922551 112CHCT 120.00 89 6-1 56.97 63.03

Ev- 751 303301 923037 112CHCT 53.00 275 6-1 125.18 -72.18

Ev-UR008 303247 922331 112CHCT 56.00 -- 6-1 124.22 -68.22

Ev-UR009 303222 922206 112CHCT 58.00 -- 6-27 117.61 -59.61

Iberia Parish

I- 19 295748 915710 112CHCTU 9.72 460 6-9 18.96 -9.24

I- 93 300035 914433 112CHCTU 18.53 585 6-9 22.14 -3.61

Jefferson Davis Parish

JD- 33 300517 924931 112CHCTU 7.18 350 6-7 50.97 -43.79

JD- 98 301813 924824 112CHCTU 35.00 -- 6-22 88.37 -53.37

JD- 222 300236 925435 112CHCTU 4.61 300 6-7 43.62 -39.01

JD- 353 302334 930011 112CHCT 25.00 300 6-28 41.79 -16.79

JD- 401 301110 925651 112CHCTU 14.00 282 6-7 72.32 -58.32

JD- 406 302852 924150 112CHCT 50.00 450 6-22 82.09 -32.09

JD- 445 302602 924638 112CHCT 47.82 262 6-16 79.32 -31.50

JD- 470 301106 924254 112CHCTU 10.00 325 6-7 68.17 -58.17

JD- 485A 301300 925845 112CHCTU 21.36 290 6-7 80.85 -59.49

JD- 493 302509 925321 112CHCT 37.95 220 6-6 57.09 -19.14

JD- 702 302101 924746 112CHCT 35.00 236 6-6 85.31 -50.31

JD- 740 302137 924010 112CHCT 35.00 264 6-6 90.04 -55.04

JD- 751 300547 924426 112CHCTU 10.00 193 6-7 56.56 -46.56

JD- 772 301354 924455 112CHCTU 27.00 340 6-16 86.38 -59.38

JD- 826 301513 925314 112CHCTU 26.00 225 6-28 76.27 -50.27

JD- 835 302008 925414 112CHCTU 31.00 280 6-28 53.94 -22.94

Lafayette Parish

Lf- 524 300605 915935 112CHCTU 25.00 174 6-9 27.25 -2.25

Lf- 662 301426 920006 112CHCTU 40.37 152 6-8 51.09 -10.72

Lf- 823 301127 920822 112CHCTU 30.00 363 6-9 59.02 -29.02

Lf- 914 301407 921042 112CHCTU 30.00 250 6-8 68.11 -38.11

Lf- 958 301922 920102 112CHCTU 50.00 115 6-8 54.72 -4.72

St. Landry Parish

SL- 142 302732 921029 112CHCT 50.00 235 6-7 83.84 -33.84

SL- 179 304116 920836 112CHCT 55.23 94 6-5 56.85 -1.62

SL- 190 303725 920830 112CHCT 74.36 175 6-6 84.78 -10.42

SL- 331 303200 921005 112CHCT 62.00 119 6-6 91.46 -29.46

SL- 347 302959 922418 112CHCT 50.00 300 6-1 119.18 -69.18

SL- 392 302455 920320 112CHCT 46.74 126 6-7 55.39 -8.65

SL- 566 303134 921908 112CHCT 51.00 250 6-7 103.23 -52.23

St. Martin Parish

SMn- 109 301304 914240 112CHCTU 11.34 375 6-22 9.74 1.60

St. Mary Parish

SM- 57U 294749 914023 112CHCTU 8.72 638 6-28 11.02 -2.30

Vermilion Parish

Ve- 28 294705 921150 112CHCTU 6.74 260 6-6 7.13 -0.39

Ve- 442 295650 922450 112CHCTU 5.42 281 6-6 36.68 -31.26

Ve- 460 295645 921655 112CHCTU 9.78 300 6-20 29.01 -19.23

Ve- 501 300117 920056 112CHCTU 21.62 227 6-5 29.51 -7.89

Ve- 579 300003 921704 112CHCTU 14.00 239 6-20 40.76 -26.76

Ve- 586 300240 920832 112CHCTU 15.40 259 6-5 34.88 -19.48

Ve- 629L 294825 922020 112CHCTU 1.79 487 6-6 10.83 -9.04

Ve- 629U 294825 922020 112CHCTU 1.79 457 6-6 9.70 -7.91

Ve- 630U 295031 922032 112CHCTU 4.75 498 6-6 15.66 -10.91

Ve- 637L 295345 921007 112CHCTU 4.06 243 6-7 14.69 -10.63

Ve- 637U 295345 921007 112CHCTU 4.06 198 6-7 13.56 -9.50

Ve- 639 293845 922649 112CHCTU   5.84 608 6-6 11.30 -5.46

Ve- 654 295504 923201 112CHCTU 9.60 267 6-20 33.82 -24.22

Ve- 764 300030 922109 112CHCTU 15.00 250 6-20 43.84 -28.84

Ve-1134 300042 922933 112CHCTU 5.00 190 6-20 45.55 -40.55

Ve-1152 300501 921534 112CHCTU 10.00 235 6-20 56.57 -46.57

Well no.

Lati-tude 

(degrees)

Longi-tude 

(degrees)Aquifer

 code

Altitude of land surface (feet relative 

to sea level)

Depth of 

well (feet)Date

Depth to water level  (feet 

below land 

surface)

Altitude of water 

level (feet relative 

to sea level)

Copies of this report can be purchased from:

U.S. Geological SurveyBranch of Information ServicesBox 25286Denver, CO 80225E-mail: infoservices@usgs.govFax: (303) 202-4188Telephone (toll free): 1-888-ASK-USGS

For additional information, contact:

District ChiefU.S. Geological Survey3535 S. Sherwood Forest Blvd., Suite 120Baton Rouge, LA 70816E-mail: dc_la@usgs.govFax:  (225) 389-0706Telephone:  (225) 389-0281

Figure 2.  Partial hydrogeologic column of aquifers in southwestern Louisiana(modified from Lovelace and Lovelace, 1995, p. 10).

Figure 3.  Potentiometric surface of the massive, upper, and “200-foot” sands of the Chicot aquifer system in southwestern Louisiana, June 2000.

CONVERSION FACTORS AND VERTICAL DATUM

Multiply By To obtain

inch (in) 25.4 millimeterfoot (ft) 0.3048 meter

square mile (mi2) 2.590 square kilometermillion gallons per day (Mgal/d) 3,785 cubic meter per day

acre 4,047 square metermile 1.609 kilometer

Sea level:  In this report, “sea level” refers to the National Geodetic Vertical Datum of 1929--a geodetic datum derived from a general adjustment of the first-order level nets of both the United States and Canada, formerly called Sea Level Datum of 1929.

1996 1997 1998 1999 2000

-100

-25

-100

-75

-50

WA

TE

R-L

EV

EL

AL

TIT

UD

E,IN

FE

ET

RE

LA

TIV

ET

OS

EA

LE

VE

L

1996 1997 1998 1999 2000-100

-25

-100

-75

-50

Ac- 326

JD-485A

1996 1997 1998 1999 2000

-75

0

-75

-50

-25

Ev-229

Jones, P.H., Turcan, A.N., Jr., and Skibitzke, H.E., 1954, Geology and ground-water resources of southwestern Louisiana:  Louisiana Department of Conservation Geological Bulletin no. 30, 285 p.

Louisiana Cooperative Extension Service, 2000, Louisiana summary:  Agriculture and natural resources, 1999:  Baton Rouge, Louisiana, Louisiana State University Agricultural Center, 320 p.

Louisiana Office of State Climatology, 2000, Louisiana monthly climate review:  Baton Rouge, Louisiana, Louisiana State University, v. 20, no. 1-6.

Louisiana State University Agricultural Center, 2000, Saline waters pose risks to cattle, crops; producers urged to monitor water supplies: accessed December 28, 2000, at URL http://www.agctr.lsu.edu/3NWS1012.htm

Lovelace, J.K., and Johnson, P.M., 1996, Water use in Louisiana, 1995:  Louisiana Department of Transportation and Development Water Resources Special 

o. 11, 127 p.

nd Lovelace, W.M., 1995, Hydrogeologic unit nomenclature and er codes for aquifers and confining units in Louisiana:  Louisiana 

ent of Transportation and Development Water Resources Special o. 9, 12 p.

 and Atmospheric Administration, 1995, Climatological data annual y:  Asheville, North Carolina, National Oceanic and Atmospheric stration, National Climatic Data Center, 23 p.

 and Atmospheric Administration Climate Prediction Center, 2000,   t monitoring, past Palmer Drought Severity Index maps by week for cessed June 19, 2000, at URL http://www.cpc.ncep.noaa.gov/

s/analysis_monitoring/regional_monitoring/palmer/2000

4, The occurrence of high concentrations of chlorides in the Chicot system of southwestern Louisiana:  Louisiana Department of rtation and Development Water Resources Technical Report no. 33, 

lford, K.J., and Martin, Angel, Jr., 1990, Geohydrology and on of flow in the Chicot aquifer system of southwestern Louisiana:  na Department of Transportation and Development Water Resources al Report no. 50, 58 p.

86, Louisiana hydrologic atlas map no. 2:  Areal extent of freshwater r aquifers of Louisiana:  U.S. Geological Survey Water-Resources ations Report 86-4150, 1 sheet.

and Kilburn, Chabot, 1963, Ground-water conditions in stern Louisiana, 1961 and 1962, with a discussion of the Chicot in the coastal area:  Department of Conservation, Louisiana cal Survey, and Louisiana Department of Public Works Water es Pamphlet no. 12, 32 p.

, Ground-water pumpage and related effects, southwestern a, 1970, with a section on surface-water withdrawals:  Department 

ervation, Louisiana Geological Survey, and Louisiana Department of orks Water Resources Pamphlet no. 27, 33 p.

Aquifer

Lake Charles area Rice growing area

“200-foot” sand of Chicot aquifer, upper Lake Charles area sand unit

“500-foot” sand of Chicot aquifer, lower Lake Charles area sand unit“700-foot” sand of Lake Charles area

Aquifer

Chicot aquifer system

System Series 

Qua

tern

ary

Plei

stoc

ene

Longi-tude 

(degrees)Aquifer

 code

Altitude of land surface (feet relative 

to sea level)

Depth of 

well (feet)Date

Depth to water level  (feet 

below land 

surface)

Altitude of water 

level (feet relative 

to sea level)

Acadia Parish

921939 112CHCT 50.00 338 6-6 111.69 -61.69

922426 112CHCT 41.00 284 6-27 109.18 -68.18

922029 112CHCT 43.00 -- 6-1 107.88 -64.88

922138 112CHCTU 25.84 -- 6-14 90.38 -64.54

921040 112CHCTU 36.00 -- 6-14 72.48 -36.48

923607 112CHCTU 25.00 260 6-14 78.63 -53.63

923457 112CHCTU 31.00 250 6-7 89.38 -58.38

922345 112CHCTU 25.80 202 6-6 89.98 -64.18

922949 112CHCTU 12.00 280 6-14 63.72 -51.72

922742 112CHCTU 15.00 280 6-8 73.07 -58.07

922705 112CHCTU 36.00 315 6-27 102.07 -66.07

923326 112CHCTU 11.00 292 6-8 65.74 -54.74

922822 112CHCTU 21.00 256 6-6 82.11 -61.11

923420 112CHCT 42.00 203 6-7 104.78 -62.78

922727 112CHCT 40.00 248 6-27 104.67 -64.67

922656 112CHCTU 22.00 248 6-6 85.16 -63.16

922053 112CHCTU 25.00 211 6-8 86.26 -61.26

922051 112CHCT 40.00 249 6-7 106.70 -66.70

922346 112CHCTU 15.00 176 6-20 68.40 -53.40

921518 112CHCT 43.00 265 6-8 97.91 -54.91

923431 112CHCT 37.00 275 6-7 97.75 -60.75

Allen Parish

Al- 6 303845 924443 112CHCT 80.00 -- 6-28 67.2112.79

Al- 59 303454 923812 112CHCT 73.00 250 6-28 93.95-20.95

Al- 215 304052 923848 112CHCT 70.00 207 6-28 78.79-8.79

Al- 241 303004 925411 112CHCT 42.97 62 6-19 34.658.32

Al- 283 303443 925028 112CHCT 62.00 93 6-20 40.8421.16

Al- 290 303853 925616 112CHCT 65.00 103 6-23 18.9446.06

Al- 293 304337 925040 112CHCT 100.00 84 6-22 32.9267.08

Al- 294 303150 925756 112CHCT 48.00 142 6-19 26.2721.73

Al- 304 304901 924616 112CHCT 114.00 104 6-23 20.2193.79

Al- 396 303147 930228 112CHCT 57.00 315 6-23 32.8624.14

Beauregard Parish

Be- 367 302513 931552 112CHCT 45.00 455 6-27 71.20-26.20

Be- 430 303644 930204 112CHCT 120.00 123 6-1 59.6860.32

Be- 431 304055 930242 112CHCT 70.00 84 6-1 6.7063.30

Be- 433 305145 930356 112CHCT 132.00 82 6-1 7.62124.38

Be- 435 305019 932924 112CHCT 129.00 124 6-1 20.39108.61

Be- 439 304556 931425 112CHCT 169.00 189 6-1 48.27120.73

Be- 440 305251 932114 112CHCT 212.00 169 6-1 45.07166.93

Be- 446 303933 933536 112CHCT 83.00 157 6-1 26.7056.30

Be- 457 303606 933842 112CHCT 95.00 155 6-1 48.2546.75

Be- 469 302923 931246 112CHCT 84.00 380 6-21 71.3712.63

Calcasieu Parish

Cu- 395 301634 931402 11202LC 12.00 200 6-27 40.21-28.21

Cu- 642 301641 930359 11202LC 19.00 287 6-1 64.32-45.32

Cu- 768 301036 931244 11202LC 11.53 306 6-14 68.83-57.30

Cu- 771 301336 931830 11202LC 17.76 241 6-8 63.21-45.45

Cu- 843 301148 931932 11202LC 12.00 205 6-8 56.01-44.01

Cu- 854 300643 930447 11202LC 20.00 430 6-8 83.64-63.64

Cu- 962 300812 931658 11202LC 11.00 287 6-21 53.36-42.36

Cu- 967 301147 931419 11202LC 12.00 240 6-14 58.95-46.95

Cu- 968 300557 932504 11202LC 10.00 276 6-28 40.18-30.18

Cu- 971 300534 925437 112CHCTU 5.00 500 6-13 47.94-42.94

Cu- 975 301941 930356 11202LC 20.00 237 6-13 48.65-28.65

Cu- 990 301059 931251 11202LC 14.00 183 6-14 65.86-51.86

Cu-1017 302719 932342 112CHCT 72.50 351 6-27 75.40-2.90

Cu-1066 301840 934107 11202LC 25.00 255 6-28 34.81-9.81

Cu-1245 301200 934044 11202LC 11.00 136 6-28 16.43-5.43

Cu-1302 302357 932742 11202LC 45.00 180 6-27 43.561.44

Cu-1386 301048 930348 11202LC 24.00 324 6-9 78.75-54.75

Cu-1422 301250 930320 11202LC 22.00 262 6-9 63.06-41.06

Cu-6680Z 301632 930919 11202LC 11.00 170 6-21 43.15-32.15

Cu-7082Z 300816 932805 11202LC 13.00 260 6-28 42.94-29.94

Cameron Parish

Cn- 80L 295846 923811 112CHCTU 4.73 4816-20

39.00-34.27

Cn- 81L 300125 923825 112CHCTU 4.45 4786-20

41.84-37.39

Cn- 90 295611 930448 11202LC 3.19 3966-20

37.48-34.29

Cn- 92 300104 930156 11202LC 5.50 4436-8

49.41-43.91

Cn- 118 294615 930042 112CHCTU 5.00 6386-28

24.02-19.02

Cn- 196 300122 930604 11202LC 10.00 4206-8

59.31-49.31

GYf southwestern Louisiana and 

stem is composed of deposits of lay and sandy clay that dip grade southward from coarse easingly subdivided by clay ard, towards the Atchafalaya l deposits of the Atchafalaya 

 into three subregions in Louisi- the northern part of the study ngle massive sand.  The approx-wn in figure 1.  South of the ameron Parishes to the Atchafa-d units (Whitman and Kilburn, 

Cameron Parishes, the Chicot 700-foot” sands, named after (Jones, 1950, p. 2).  The “200-tinuous with, the upper sand.  quifers in southwestern Louisi-

rs in areas where the aquifer arishes and in northern Allen, se areas, precipitation infiltrates s of discharge.  Additional d through overlying and upward lluvial deposits associated with to the upper sand unit (Nyman  the aquifer system indicated f the water entering the Chicot nt of the water withdrawn in the ion (Nyman and others, 1990, 

e, upper, and “200-foot” sands of the Chicot aquifer system during ydrographs of water levels in selected wells completed in the aquifer 

esented. The potentiometric-surface map can be used for determination ter-flow direction, hydraulic gradients, and effects of withdrawals on ater system. Water-level data are on file at the USGS office in Baton 

Description of the Study Areastudy area, located in southwestern Louisiana, extends across about d includes all or parts of Acadia, Allen, Beauregard, Calcasieu, Cam-line, Iberia, Jefferson Davis, Lafayette, Rapides, St. Landry, St. Martin, milion, and Vernon Parishes (fig. 1).  The climate generally is warm  with high humidity and frequent rain.  The average annual tempera-0oC, and the average annual rainfall is 55 in. (National Oceanic and 

Administration, 1995, p. 7, 9).  Much of the area is rural, and rice cul- primary agricultural activity.  In 1999, 460,000 acres of rice were thwestern Louisiana (Louisiana Cooperative Extension Service, 

Acknowledgmentsauthors gratefully acknowledge the assistance and cooperation of lic water suppliers and private well owners who allowed water levels d in their wells.  The authors thank Eddie Eskew, Keith Fontenot, ier, Ron Levy, Jerry Whatley, and Gary Wicke, County Agents of the 

operative Extension Service, who initiated contacts with many of the nd farmers whose wells were used in this study.  Additionally, the  Z. “Bo” Bolourchi, Chief, Water Resources Section, Louisiana f Transportation and Development, for providing well information that elect wells for this study.

HYDROGEOLO

Figure 1. Location of study area in southwestern Louisiana.

Jones, P.H., 1950, Ground-water conditions in the Lake Charles area, Louisiana:  U.S. Geological Survey Open-File Report, 16 p.

Well no.

Lati-tude 

(degrees)

Ac- 3 302623

Ac- 24 302511

Ac- 69 302236

Ac- 189 301050

Ac- 222 301904

Ac- 294 301443

Ac- 296 301839

Ac- 326 301832

Ac- 330 300719

Ac- 369 300850

Ac- 375 302053

Ac- 382 300849

Ac- 391 301628

Ac- 428 302729

Ac- 464 302610

Ac- 500 301635

Ac- 537 301434

Ac- 618 302533

Ac- 669 300615

Ac- 825 302244

Ac- 836 302304

POTENTIOMETRIC SURFACE

A potentiometric-surface map (fig. 3) was constructed using water-level data from wells completed in the massive, upper, and “200-foot” sands of the Chicot aqui-fer system (table 1, fig. 1).  Water levels were measured during June 2000; water lev-els typically decline (due to seasonal withdrawals) to their yearly low during June (fig. 4).  Water levels can fluctuate seasonally as much as 40 ft in some areas in response to pumping for rice irrigation.  Water levels were measured using steel or electrical tapes marked with 0.01 ft gradations; wells in which water levels were mea-sured were not being pumped at the time the measurements were made.

The highest water level, about 167 ft above sea level, was measured in the outcrop area of the Chicot aquifer system in northwestern Beauregard Parish.  Water levels more than 50 ft below sea level were recorded in parts of Acadia, Calcasieu, Evangeline, and Jefferson Davis Parishes.  The lowest water levels, more than 70 ft 

below sea level, extended over an area of about 60 mi2 in southern Evangeline Parish.

Ground water moves through the aquifer system from areas of higher hydraulic head to lower hydraulic head, and the direction of flow is perpendicular to equipotential (contour) lines of the potentiometric surface.  During June 2000, flow in the aquifer was generally towards rice-growing areas of Acadia Parish, Jefferson Davis Parish, southern Evangeline Parish, eastern Calcasieu Parish, and parts of sur-rounding parishes.  In the northern part of the study area, flow in the massive sand generally was towards the south and southeast along the dip of sediments.  In the southern part of the study area, flow in the upper sand and the “200-foot” sand was to the north from coastal areas towards rice-growing areas.  Along the eastern extent of the aquifer system, flow generally trended westward.

SELECTED REFERENCESCovay, K.J., Sturrock, A.M., Jr., and Sasser, D.C., 1992, Water requirements for 

growing rice in southwestern Louisiana, 1985-86:  Louisiana Department of Transportation and Development Water Resources Technical Report no. 52, 14 p.

Report n

Lovelace, J.K., acomputDepartmReport n

National OceanicsummarAdmini

National OceanicDrough2000: acproduct

Nyman, D.J., 198aquifer Transpo75 p.

Nyman, D.J., HasimulatiLouisiaTechnic

Smoot, C.W., 19in majoInvestig

Whitman, H.M., southweaquifer GeologiResourc

Zack, A.L., 1971Louisianof ConsPublic W

- Louisiana Ground-Water Map No. 12:
- Potentiometric Surface of the Chicot Aquifer System in Southwestern Louisiana, June 2000 John K. ...
- By
- 2001
- INTRODUCTION
- Description of the Study Area
- Acknowledgments
- HYDROGEOLOGY
- POTENTIOMETRIC SURFACE
- SELECTED REFERENCES
CONVERSION FACTORS AND VERTICAL DATUM
- Multiply By To obtain
- inch (in) 25.4 millimeter
- foot (ft) 0.3048 meter
- square mile (mi2) 2.590 square kilometer
- million gallons per day (Mgal/d) 3,785 cubic meter per day
- acre 4,047 square meter
- mile 1.609 kilometer
- Sea level: In this report, “sea level” refers to the National Geodetic Vertical Datum of 1929--a ...