Summary Appraisals of the 

Nation's Ground-Water ResourcesLower Mississippi Region 

G E 0 L 0 G I C A L S U R V E Y P R 0 F E S S I 0 N A L P A P E R 8 1 3-N 

SUMMARY APPRAISALS OF THE NATION'S 

GROUND-WATER RESOURCES, 

LOWER MISSISSIPPI REGION 
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HAWAII 

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CARIBBEAN 

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Water Resources 

Regions 

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Letters indicate chapter 

designations 

Chapters are published or in press in U.S.G.S. 

Professional Paper 813 

series 

Geographic lndex to the Series, U.S. Geological Survey Professional Paper 813, Summary Appraisals of the Nations Ground-Water Resources. 

Boundaries shown are those established by the United States Water-Resources Council for Water-Resources Regions in the United States. 
Summary Appraisals of the 

Nation's Ground-Water ResourcesLower Mississippi Region 

By]. E. TERRY, R. L. HOSMAN, and C. T. BRYANT 

G E 0 L 0 G I C A L S U R V E Y P R 0 F E S S I 0 N A L P A P E R 813-N 

An emphasis on the region's large available 

supply of ground water and on the water-resource 

management practices directed toward 

deriving the maximum benefit from 

this large water supply 

:' . ,., ) - - . ~--. ,., ,. ( ' ,, . 

'I 
UNITED STATES DEPARTMENT OF THE INTERIOR 

CECIL D. ANDRUS, Secretary 

GEOLOGICAL SURVEY 

H. William Menard, Director 

Terry, J. E. 

Summary appraisals of the nation's ground-water resources, lower Mississippi region. 

(Geological Survey Professional Paper 813-N) 

Bibliography: p.39-41. 

I. Water, Underground-Gulf coast (United States) 2. Water, Underground-Mississippi Valley. I. Hosman, R. L., joint author. 

II. Bryant, C. T., joint author. III. Title. IV. Series: United States. Geological Survey. Professional Paper 813-N 

GB1017.T47 553'.79'0976 78-31887 

For sale by the Superintendent of Documents, U.S. Government Printing Office 

Washington, D.C. 20402 

Stock Number 024-001-03146-9 
CONTENTS 

Abstract 

Introduction 

Page 

N1 

1 

Location and size of area ------------------------------ 1 

The new land ---------------------------------------- 1 

Purpose and scope ------------------------------------ 3 

The water-resources scene -------------------------------- 3 

Hydrologic boundaries -------------------------------- 7 

Surface water ---------------------------------------- 7 

Ground water ---------------------------------------- 7 

Why is ground water of importance in the Lower Mississippi 

Region? -------------------------------------------- 11 

Widespread accessibility ------------------------------ 11 

Large amount available ------------------------------ 16 

Acceptable for many uses------------------------------ 19 

Why are we not getting maximum benefit from ground water? 26 

Inadequate consideration ------------------------------ 26 

Improper development -------------------------------- 26 

Fractional use of available supply______________________ 29 

Page 

How can we obtain maximum benefit from ground water? -- N29 

Expand information base, and use it ------------------ 29 

Use modern technology-------------------------------- 31 

Aquifer modeling -------------------------------- 31. 

Artificial recharge -------------------------------- 32 

Blending of water -------------------------------- 32 

Control and use of saltwater ---------------------- 33 

Recycling ---------------------------------------- 34 

Geothermal energy ------------------------------ 34 

Plan properly ---------------------------------------- 34 

What are the possible consequences of increased ground-water 

use? ---------------------------------------------- 35 

Hydraulic changes ------------------------------------ 36 

Water-quality changes -------------------------------- 36 

Aquifier-framework changes -------------------------- 36 

In summary-Is the·outlook optimistic? ------------------ 38 

Selected references -------------------------------------- 39 

ILLUSTRATIONS 

Page 

FRONTSPIECE. Geographic index to the series, U.S. Geological Survey Professional Paper 813. 

FIGURE 1. Location map, Lower Mississippi Region ------------------------------------------------------------------------ N2 

2. Map showing normal annual precipitation and temperature ------------------------------------------------------ 4 

3. Map showing average annual-potential evapotranspiration -------------------------------------------------------- 5 

4. Map showing mean annual runoff ----------------------------~------------------------------------------------- 6 

5. Geologic map -------------------------------------------------------------------------------------------------- 8 

6. Generalized geologic sections ______ ------------------------------------------------------------------------------ 9 

7. Map showing base of freshwater in Coastal Plain aquifers -------------------------------------------------------- 10 

8. Map showing freshwater aquifers underlying the Lower Mississippi Region ---------------------------------------- 12 

9. Map showing the availability of fresh ground water -------------------------------------------------------------- 13 

10. Map showing the ranges in well yields throughout the region ---------------------------------------------------- 14 

11. Diagrams showing ground water-surface water relations -------------------------------------------------------- 17 

12. Map showing the locations of stream-gaging stations where the 7-day, 10-year low flow has been defined ------------ 18 

13. Diagrams showing how a well located near a stream can utilize induced recharge from the stream ---------------- 20 

14. Diagrams showing relationship of recharge to aquifer utilization -------------------------------------------------- Z1 

15. Map showing dissolved-solids concentration of available ground water -------------------------------------------- 22 

16. Map showing prevalent chemical types of water in streams at low flow -------------------------------------------- 23 

17. Map showing prevalent dissolved-solids concentration of water in streams at low flow ------------------------------ 24 

18. Map showing areas covered in ground-water-related reports ------------------------------------------------------ 26 

19. Diagrams showing well construction without adequate research of available information -------------------------- 27 

20. Diagrams depicting contamination of freshwater aquifers by abandoned, deep test holes ---------------------------- 27 

21. Sketch showing how to locate a new well in the vicinity of existing wells ---------------------------------------- 28 

22. Map showing areas of severe water-level declines ---------------------------------------------------------------- 30 

23. Graph showing estimated ground-water use ---------------------------------------------------------------------- 31 

24. Sketch depicting a discharge-recharge barrier-well system for the control of saltwater encroachment ---------------- 33 

25. Hydrographs showing water-level <leclines in the Memphis Sand and the Sparta Sand ------------------------------ 37 

26. Sketch of the Baton Rouge, La., area, where a fault at least partially controls the advance of a saltwater front ______ 38 

TABLE 

Page 

TABLE 1. The 7-day, 10-year low flow at stream-gaging stations plotted in figure 12 ------------------------------------------ N19 

v 

SUMMARY APPRAISALS OF THE NATION'S GROUND-WATER 

RESOURCES-LOWER MISSISSIPPI REGION 

By J. E. TERRY, R. L. HosMAN, and C. T. BRYANT 

ABSTRACT 

The Lower Mississippi Region comprises an area of 102,400 

square miles (265,200 square kilometers). Almost all this area is in 

the physiographic province known as the Gulf Coastal Plain. Three 

small areas on the northwest boundary of the region are in the 

Interior Highlands. 

The Lower Mississippi Region has an abundance of ground water. 

The geologic structure in that part of the region within the Coastal 

Plain is an elongated trough which has been filled with permeable 

materials, resulting in vast subsurface reservoirs. Except in local 

areas where continued large withdrawals have caused significant 

water-level declines, these reservoirs are full. 

Recharge to the region's aquifers is primarily from rainfall. Annual rainfall in most of the region is well distributed throughout 

the year and is sufficient to satisfy evapotranspiration requirements 

and still provide recharge to the aquifers. 

An estimated 844 billion cubic feet (24 billion cubic meters) of 

fresh ground water is available for withdrawal annually in the region. Only about one-third of this quantity is being utilized. Therefore, on this basis alone, the region still has much potential for 

ground-water development. 

The Coastal Plain aquifers within the Lower Mississippi Region 

contain large reserves of saltwater in the downdip limits of the 

aquifers. The quantity of saltwater in the region is several times 

that of freshwater. As desalinization techniques are developed and 

as more uses are found for saltwater, this reserve could become an 

important source of water for the region. 

At present (1976), the most productive and potentially productive 

aquifers or aquifer systems in the region are the Mississippi River 

valley alluvial aquifer of Quaternary age and the Sparta Sand and 

the Memphis aquifer (Memphis Sand in Tennessee) of Tertiary age. 

The Sparta Sand and the Memphis aquifer are heavily utilized and 

have shown significant water-level declines. However, selected well 

hydrographs indicate that water levels may be stabilizing under 

present pumping conditions. The Mississippi River valley alluvial 

aquifer is the most extensive high-yielding aquifer in the region; 

yields of several thousand gallons per .minute may be obtained at 

depths of less than 200 feet (61 meters). 

To obtain maximum benefit from the vast quantities of ground 

water in the region, adequate attention must be given to the effects 

of proposed development upon the ground-water regime. Knowledge 

of the geologic structure and hydraulic properties of the aquifer systems is essential to an evaluation of the effects of such development. 

Some studies have been made in sufficient detail to provide this 

knowledge, but additional studies are needed. 

Activities that could cause significant changes in the groundwater regime should be undertaken only after all available information has been considered. Failure to seek out and use such 

information may result in inefficient development of the groundwater resource and, in some instances, degradation of the quality of 

the resource. 

Some changes always result from ground-water development. The 

possible changes can be grouped into three categories: hydraulic, 

water quality, and those affecting the physical framework of the 

aquifers. Generally, they are small in magnitude and areal extent. 

Because these changes occur below the ground surface, they are 

unknown to the ground-water user unless they noticeably affect the 

quantity or quality of water produced or cause obvious physical effects, such as land subsidence. 

Great advances have been made in hydrologic technology in recent years. Predictive models have been developed that make it possible for the hydroiogist to simulate aquifer responses to proposed 

development or other stresses. These models would be invaluable 

tools in progressive water-resources planning and management. 

INTRODUCTION 

LOCATION AND SIZE OF AREA 

The Lower Mississippi Region, as defined by the 

Water Resources Council, 1970, includes all the 

drainage basin of the Mississippi River downstream 

from its confluence with the Ohio River, except those 

parts of drainage basins of the Arkansas, Red, and 

White Rivers upstream from the backwater limits of 

the Mississippi River. It also includes the floodprotected areas at Cairo, Ill., and the Louisiana 

coastal area. The region comprises parts of Arkansas, 

Illinois, Kentucky, Louisiana, Mississippi, Missouri, 

and Tennessee, and encompasses about 102,400 mi2 

(265,200 km2 ). Drainage from almost half of the conterminous United States culminates in the Lower 

Mississippi Region (fig. 1). The Mississippi River terminates at the lower end of the region, completing a 

river course totaling 2,348 mi (3,778 km) (U.S. 

Geological Survey, 1970). 

THE NEW LAND 

Explorers, traders, and hunters who sought adventure and fortune were the first to travel the valley of 

the Mississippi River. Following the trails they 

blazed, immigrants came to farm the river soil and to 

settle the wilderness. These early settlers in the 

Lower Mississippi Region found the Mississippi River 

to be both friend and foe. The river provided a mode of 

transportation and fertile soil for farming, yet it beN1 
N2 SUMMARY APPRAISALS OF THE NATIONS GROUND-WATER RESOURCES 

FIGURE 1.-The Lower Mississippi Region. 

came a destructive force during floods. Since the time 

when the first plots of land were cleared for farming, 

agriculture has played a major role in both the 

economic and the cultural development of the region, 

and because the most productive land for farming lies 

along the Mississippi and its major tributaries, flood 

control has been the object of much concern and effort. 

In more recent years, industry has greatly increased 

in the region. From Cairo, Ill., to the Gulf of Mexico, 

and between New Orle.ans and Lake Charles, La., are 

found petroleum refineries and related facilities, industrial and agricultural chemical plants, grain 

elevators, processing plants for food and kindred 

products, shipyards, textile mills, manufacturers of 

paper and related products, powerplants, cement 

plants, and aluminum-producing complexes. The reliance of many of these industries upon the river for 

movement of raw materials and finished products continues to focus regional attention upon the surfacewater resource. 
LOWER MISSISSIPPI REGION N3 

PURPOSE AND SCOPE 

In contrast to the recognition given to surface water, only minor attention has been given to ground 

water in the Lower Mississippi Region since the early 

1900's. The purpose of this report is to direct attention 

to the region's large ground-water resource so that it 

will not be overlooked when plans for water-resourcerelated changes within the region are devised and implemented. The pertinent questions about ground 

water that should be considered in developing and 

implementing water-management plans are: 

1. Where is the ground water? 

2. How much ground water is available? 

3. What is the quality of the ground water? 

4. What effects will development and use of ground 

water have on the total water resources and environment in the region? 

And, inasmuch as ground water is such an important 

part of the total water resources of the region and 

should be considered in planning5. What kinds of data are needed, and where are data 

insufficient, to permit full consideration of 

ground water in water-resource planning? 

This report supplies answers to these questions by 

presenting a regional assessment of the ground-water 

resource with emphasis on its significance. The scope 

is intended to be sufficient to permit evaluation of 

broad concepts of water planning for the region and to 

determine whether ground water has been adequately 

considered. This report is also intended to provide 

sufficient detail to serve as a basis for planning and 

program development. 

All unreferenced quantitative values in this report 

were taken from either the "Lower Mississippi Region 

Comprehensive Study," by the Lower Mississippi Region Comprehensive Study Coordinating Committee 

(1974), or the "1975 National Water Assessment: 

Ground Water in the Lower Mississippi Region," by 

Boswell (1979). 

Most numbers in this report are given in inchpound units followed by metric units in parentheses. 

The conversions to metric units were made as follows: 

Multiply 

Inch-pound unit Inch-pound 

abbreviation 

Acre ----------------acre Acre-foot ------------ acre-ft 

Cubic foot ------------ ft' Cubic foot per second -------------- fP/s Foot ------------------ ft Gallon --------------gal 

Gallon --------------gal Gallon per minute ____ gal/min 

Inch ------------------in. Mile ---------------- mi Square mile ---------- mj2 

By 

Conversion factor 

0.4047 

.0012335 

.02832 

.02832 

.3048 

3.7854 

.0037854 

.06309 25.4 

1.6093 

2.59 

To obtain 

Metric 

unit Metric abbreviat ion 

Hectare ------------ ha Cubic hectometer ____ hm3 

Cubic meter -------- m3 Cubic meter per 

second ------------ m3/s 

Meter -------------- m Liter ---------------- L Cubic meter ________ m3 Liter per second ____ lls 

Millimeter ---------- mm Kilometer __ ________ km 

Square kilometer ____ km' 

Chemical concentrations are given only in metric 

units-milligrams per liter (mg/L). For concentrations 

less than 7,000 mg/L, the numerical value is about the 

same as for concentrations in the inch-pound unit, 

parts per million. 

Throughout this report references to small, moderate, and large quantities of water in relation to 

aquifer yields have the following meaning: small, 

0-50 gal/min (0-30 Lis); moderate, 50-500 gal/min 

(3-30 L/s); large, greater than 500 gal/min (30 Lis). 

THE WATER-RESOURCES SCENE 

The Lower Mississippi Region is indeed water rich. 

Precipitation throughout the region is generally 

abundant and well distributed areally. The normal 

annual precipitation ranges from 44 in. (1,100 mm) in 

the northern part of the region to 64 in. (1,600 mm) in 

the southeastern part (fig. 2). Seasonally, precipitation maximums occur in the winter in the northern 

part and in the summer in the southern part. A part 

of this precipitation is returned to the atmosphere by 

evapotranspiration, part infiltrates to the aquifers, 

and part becomes runoff. 

Potential evaportranspiration is the combination of 

evaporation from the ground surface and transpiration from plants that would occur if there were complete vegetation coverage and adequate soil moisture. 

In the Lower Mississippi Region, average annual potential evapotranspiration ranges from 30 in. (760 

mm) in the north to 44 in. (1,100 mm) in the south 

(fig. 3). Because periods of limited soil-moisture 

availability occur from time to time and vegetation 

coverage is not complete in many areas, actual 

evapotranspiration throughout a long period averages 

only about 70 to 90 percent of the potential value. 

Runoff, including base runoff and direct runoff, 

combines with surface inflow to the region to make up 

streamflow and maintain water levels in surfacewater impoundments. Runoff ranges from 18 in. (460 

mm) in the north to 26 in. (660 mm) in the south (fig. 

4). 

Recharge to the confined aquifers occurs primarily 

in the outcrop areas. In the alluvial unconfined aquifers, recharge occurs in areas where the vertical hydraulic conductivity of the overlying material is sufficient to allow downward movement of water. When 

evapotranspiration requirements are met and soilmoisture storage maximums are exceeded, water infiltrates to the aquifers. An estimate of available recharge can be expressed by: 

Recharge = preci p - (ET + direct runoff), 

where 

precip = precipitation, 

ET = evapotranspiration, and 

direct runoff = direct surface runoff. 
N4 SUMMARY APPRAISALS OF THE NATION'S GROUND-WATER RESOURCES 

"93° 

EXPLANATION 

-52- Line of equal average annual precipitation. 

Interval4 inches (102 mm) 

91 ° 90° 

Line of equal average annual temperature. 

Interval as shown, in degrees Celsius 

Regional boundary 

89° 

·~ 'i'c. + 30° 

• Base from U.S. Geological Survey, 1965 

United States base map, 1965 

0 50 100 150 200 250 KILOM ETE RS rl -'TILl +LI f

1

1--,- 1,--_IL_ __ __j_l ,

1

,--_ __ji __ -,I.JI 

0 50 100 150 MILES 

FIGURE 2.- Normal annual precipitation and temperature (modified from Lower Mississippi Region Comprehensive 

Study, 1974, v. 1, app. C). 
' 29'<+----

94° 93° 92° 

0 50 100 

I I I I I I I I I I I I 

0 50 

LOWER MISSISSIPPI REGION 

91° 

150 200 

I I 

I 

100 

EXPLANATION 

90° 

250 K I LOM ETE RS 

I 

I 

150 MI LES 

INCHES 

48 

42 

36 

30 

1 Base from U.S. Geological Survey, 1965 

United States base map, 1965 

FIGURE 3.-Average annual potential evapotranspiration (from Thornthwaite, 1948). 

N5 
N6 SUMMARY APPRAISALS OF THE NATION'S GROUND-WATER RESOURCES 

94° 

I 

I I . oj ' 29 - -- - --------+- ------·- .. , 9~ 9~ 9~ 

0 I' I I 

0 

50 

I [ 

I 

50 

100 

I 

150 

I I 

100 

200 

I 

EX PLANA TJON 

Line of equal average annual 

--16- runoff. Interval 2 inches 

(51 mm) 

250 Kl LOMETERS 

I I 

150 MILES 

Regional boundary 

FIGURE 4.-Mean annual runoff, in inches. 
LOWER .MISSISSIPPI REGION N7 

HYDROLOGIC BOUNDARIES 

The Lower Mississippi Region does not constitute a 

single or discrete hydrologic system. Although the regional boundaries are located primarily on drainagebasin divides, three major streams in addition to the 

Mississippi River bring substantial quantities of 

water across the regional boundary. In addition, and 

of even more significance in this region, underlying 

aquifers extend into adjacent areas and ground water 

moves into and out of the region. Because the regional boundaries are not completely hydrologically 

restrictive, the water resources of the region are affected by hydrologic events outside the region. 

SURFACE WATER 

The Lower Mississippi Region's surface-water supply is derived from precipitation and runoff within the 

region, streamflow including ground-water discharge 

entering the region from adjacent areas, and 

ground-water discharge to streams within the region. 

The total mean annual inflow in major streams entering the region is nearly 550,000 ft3/s (15,600 m3fs). 

The mean annual stream discharge generated within 

the region is about 120,000 ft3/s (3,400 m3/s). 

Each of the 29 controlled surface-water reservoirs 

within the region has a capacity of 5,000 acre-ft (6 

hm3) or more. The reservoirs have a combined storage 

of about 10 million acre-ft (12,300 hm3). 

Mean-annual stream outflow from the region is 

about 670,000 ft3/s (19,000 m3/s). Theroretically, this 

is the ultimate quantity of surface water available for 

use. However, because of the small number of available storage sites and the increased evaporative losses 

of surface water that occur with development, this 

quantity is not realistically obtainable. The dependable surface-water yield must therefore be defined on 

the basis of the percentage of time a given flow is 

available. For the Lower Mississippi Region, the 95-

percent-duration flow (the flow that will be equaled or 

exceeded 95 percent of the time) is 216,400 ft3/s (6,100 

m3/s), or 160 million acre-ft (197,000 hm3) per year. 

In 1970, regional surface-watet withdrawals averaged 22,000 ft3/s (620 m3/s) or 16 million acre-ft 

(20,000 hm3) per year. The total water returned to 

streams, including ground water withdrawn and not 

consumed, was 18,000 ft3/s (510 m3/s). The result was 

a net streamflow loss of 4,000 ft3/s (113 m3/s). 

GROUND WATER 

Ground water occurs in large quantities in the 

Lower Mississippi Region and is readily accessible because of the regional geological framework. Almost all 

the region is within the Gulf Coastal Plain physiographic province; three small areas along the northwest boundary are in the Interior Highlands (fig. 5). 

The Lower Mississippi Region includes most of the 

Mississippi embayment, a northeast-trending structural trough underlying part of the Coastal Plain. The 

Coastal Plain and the embayment received sediment 

during the Cretaceous, Tertiary, and Quaternary 

Periods. The older deposits generally consist of alternating layers of sand and clay; the Quaternary beds 

contain considerable gravel. The more permeable sand 

and gravel deposits now form the extensive and productive aquifers that underlie the Lower Mississippi 

Region. 

The Cretaceous and older Tertiary units in the 

northern or embayment part of the area dip toward 

the axis of the Mississippi embayment, which coincides approximately with the present course 6f the 

Mississippi River. In the southern part of the area, the 

younger Tertiary deposits dip gulfward. Quaternary 

alluvium blankets most of the area and forms a 

gulfward-thickening wedge in the southern part (fig. 

6). 

Except in areas of outcrop and where local dewatering has taken place, water in the Cretaceous and Tertiary aquifers is confined under pressure; that is, 

water levels in wells tapping these aquifers rise above 

the top of the aquifer. Most of the Quaternary aquifers 

are also confined. In some areas, hydrostatic pressures 

are sufficient to produce natural flows from wells; in 

some areas, wells that once flowed no longer flow due 

to pressure declines. Although most of the declines 

have been caused by heavy pumping, a contributing 

and in places Fritical factor has been the practice of 

allowing uncapped wells to flow unregulated. 

Recharge to the aquifers is primarily from rainfall. 

The movement of water in the confined aquifers generally is downdip unless affected by large withdrawals. In the alluvial aquifers, movement is toward 

points of discharge. The base of freshwater in the 

Coastal Plain aquifers is shown in figure 7. All aquifers locally contain some saltwater: Quaternary aquifers in coastal areas and the older aquifers in their 

downdip areas. · 

The vast reserves of saltwater in the Coastal Plain 

aquifers may prove to be an asset to the area as desalinization technology advances. The quantity of 

saltwater available is several times that of freshwater. Some saltwater is now used for purposes such as 

industrial cooling. Similar uses that can tolerate 

water of this quality will further enhance the value of 

the resource. 

Aquifers in the parts of the Lower Mississippi Region that lie in the Interior Highlands do not repre-
NB SUMMARY APPRAISALS OF THE NATION'S GROUND-WATER RESOURCES 

' i 

i ---·----··· .. 93° 92° 

COASTAL 

PLAIN 

0 50 100 150 200 250 KILOMETERS 

rl ~'r,'-rLI rll_ir-lr-~1----~1-rl --~IL_ ___ I~I 

0 50 100 150 MI LES 

EXPLANATION 

Qua ternary loess 

Quaternary terrace and alluvial 

deposits 

Pliocene and Miocene. Series 

undifferentiated 

Vicksburg Group, Forest Hill Sand, 

and Jackson Group 

Claiborne Group 

Wilcox Group 

Midway Group 

Cretaceous rocks, undifferentiated 

Paleozoic and Precambrian rocks, 

undifferentiated 

Boundaries are dashed where 

inferred or approximate 

Base from U.S. Geological Survey, 1965 

United States base map, 1965 

FIGURE 5.-Geologic map (modified from Lower Mississippi River Comprehensive Study, 1974, v. 1, app. C). 
LOWER MISSISSIPPI REGION 

N 

1 

Geologic sections in part from Cushing, 1963 

iii 

a: ...J 

UJ UJ 

f- > UJ UJ 

::;; ...J 

;:-t 

UJ UJ 

wen 

u.z 

~~ 

w· ::;; 

0 ~ ::J 0 f- ...J 

La.lMiss. 

D I D' 

MEAN SEA Ouaternar I 

LEVEL 

Tertiary 

2000 (610) 

4000 (1219) 

6000 ( 1829) 

5~ 8000(2438) L---------------~ 

<t 

iii F 

IM. La.1 tss. 

a: ...J 

ww MEAN SEA I 

f-> Ww LEVEL 

::;; ...J 

f- <t 2000 (610) 

w UJ 

UJ en u. z 4000 (1219) z <t - UJ 

w' ::;; 6000 (1829) 0~ 

::J 0 f- ...J -w 8000 (2438) 

'Jro 0 50 100 

<t 

0 50 

iii 

a: ...J 

WUJ 

f- > ww 

::;; ...J 

;:-t 

wW 

wen 

u.z 

~ ~ w·::;; 

0~ 

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" iii :2 "' lt_j a: ::- ww "' ~ f-> > c w w ~ ~ ol >. ::;; ...J A o ~::;::~~ A' 

;:-t ~ ::> 

wW MEAN SEA U O I wen 

u.z LEVEL 

z <t - w 

w'::;; 2000 (610) 

0 ~ "' "' ::JO :2 

iii f- ...J a: w a: ...J f- Cll ww ...J 

f-> <t ww B' B ::;; ...J 

MEAN SEA ;:-t 

w w LEVEL wen 

u.z 2000 (610) z <t - w 

w'::;; 

0 ~ ::JO 

f- ...J - w ':i Cll I <t Ark.:Miss. c c' 

MEAN SEA I 

LEVEL 

2000 (610) 

4000 (1219) 

iii E £' lt...J 

ww 

f- > w w 

::;; ...J 

MEAN SEA J;;=:::::=::=::=::::=:=:Q=u=a::t::e::r n:::a::r;::y:J::\=::::~::} LEVEL I -:: 

;:-t 

wW 

wen 

u. z 

~~ 

w'::;; 

0 ~ ::JO 

f-...J 

~~ 

<t 

2000 (610) 

Tertiary 

4000 (1'219) 

6000 (1829) 

8000(2438)L---------------------~ 

Miss.:Ark. 

I I .II ·I. 

,.:1·1 C::jj ~~~ 

~~I ~1~1 IF' 

I Quaternary I I ,_.II I 

200 300 400 .KILOMETERS 

200 MILES 

FIGURE 6. -Generalized geologic sections in the Lower Mississippi Region (modified from Lower Mississippi River Comprehensive Study, 1974, v. 1, app. C). 

N9 
NlO SUMMARY APPRAISALS OF THE NATION'S GROUND-WATER RESOURCES 

93° g'2o 

0 50 100 

I I I I I I I I I I I I 

0 50 

150 200 

I I 

I 

100 

EXPLANATION 

- ··- Ground-water boundary 

~ Area where intermediate beds may 

contain saltwater 

tiill] Area where fresh ground water is not 

available in significant quantities 

Interior Highlands- Paleozoic and 

Precambrian rocks,undifferentiated 

Contour on the base of freshwater. 

Contour interval 500 feet (152 m). 

Datum is mean sea level 

Base from U.S. Geological Survey, 1965 

United States base map, 1965 

250 Kl LOMETERS 

I I 

150 MILES 

FIGURE 7.-Base of freshwater in Coastal Plain aquifers (modified from Lower Mississippi River Comprehensive 

Study, 1974, v. 1, app. C). 
LOWER MISSISSIPPI REGION Nll 

sent a significant resource to the region. Rocks in 

these areas are of Paleozoic age, mostly hard 

sandstone and shale, and the ground water they contain occurs in openings along fractures and bedding 

planes. The interstitial porosity and permeability that 

make the unconsolidated aquifers of the Coastal Plain 

so productive do not exist in the Interior Highlands. 

An estimated 347,000 billion ft3 (9,800 billion m3 ) 

or 7,900 million acre-ft (10 million hm3 ) of freshwater 

underlies the Lower Mississippi Region. Of this total, 

about 844 billion ft3 (24 billion m3 ) or 19 million acreft (23,900 hm3 ) is available annually for development, 

using conventional methods. In 1970, regional groundwater withdrawals averaged about 8,300 ft3/s (240 

m3/s) or 6 million acre-ft (7,400 hm3 ) per year. 

About 65 percent of the ground water withdrawn in 

the region is used for irrigation, about 15 percent by 

industry, and about 8 percent for municipal supply. 

The remaining 12 percent is used for domestic supply, 

livestock watering, and other uses. 

WHY IS GROUND WATER OF IMPORTANCE IN 

THE LOWER MISSISSIPPI REGION? 

WIDESPREAD ACCESSIBILITY 

Ground water is available beneath the entire Lower 

Mississippi Region. Except for small areas in the 

Interior Highlands and the coastal area of Louisiana, 

one or more major aquifers (fig. 8) make moderate to 

large quantitites of freshwater available throughout 

the region (fig. 9, 10). 

The three areas in the region that are in the Interior Highlands are the Arkansas Valley and the 

Ouachita Mountains in west-central Arkansas and 

the Ozark Plateaus in southeast Missouri. In these 

areas, small quantities of ground water are available 

from Paleozoic rocks (figs. 9, 10). 

Aquifers of Cretaceous age underlie the northern 

part of the region. Except for relatively small areas in 

Arkansas, Tennessee, Mississippi, and Missouri, the 

Cretaceous material is overlain by Tertiary and (or) 

Quaternary aquifers (fig. 6) that can yield moderate to 

large quantitites of water to individual wells. For this 

reason, the deeper Cretaceous aquifers are not utilized 

extensively. 

The major Cretaceous aquifer is the McNairy Sand 

Member of the Ripley Formation in Mississippi (equivalent to the MeN airy Sand in Tennessee, Missouri, 

Illinois, and Kentucky, and the Nacatoch Sand in Arkansas). These aquifers are present throughout the 

northern one-fifth of the region within the Coastal 

Plain and in a small area in southwest Arkansas, a 

total area of nearly 20,000 mi 2 (52,000 km2). Withdrawals have been restricted to areas where the 

Vertical distribution of major aquifers 

~ Quaternary '---------"' 

L~ Mio-Pliocene aquifer 

~ Cockfield Formation '-----~ 

t Memphb "'""" 

'---------"'~ Sparta Sand 

~ Carrizo Sand ,____ _ ______,. 

'---------"'~ Lower Wilcox aquifer 

'---------"'~ Ripley Formation 
N12 SUMMARY APPRAISALS OF THE NATION'S GROUND-WATER RESOURCES 

EXPLANATION 

Number of major freshwater aquifers 

(or aquifer systems) available 

Do 

-

llE]] 2 or 3 

a 4or5 

0 50 100 150 200 250 KILOMETERS L'~'~'r'YLI ,_,_~IL---~1_,--~1----,JI I I I 1 l I I . . 

0 50 100 150 MILES 

Base from U.S. Geological Survey, 1965 

United States base map, 1965 

FIGURE B.-Multiple freshwater aquifers underlie 90 percent of the Lower Mississippi Region. 
LOWER MISSISSIPPI REGION 

· y, in 1,000 gallons per day per square mile 

(1.46 cubic meters per day per square kilometer) 

90° 

0 No fresh ground water 

0 Less than 1 

!illiilll 1-5 

!ill]] 5-25 

- 25-125 

- 125-250 

l!!!!m 250 or more 

Base from U.S. Geological Survey , 1965 

United States base map, 1965 

0 50 100 150 200 250 KILOMETERS 

11-t,' ,.LI -t' _ll--rl~~___ll __ _ll-,-_li __ ,JI I I I I l I . 0 50 100 150 MILES 

FIGURE 9.-Availability of fresh ground water. 

N13 
N14 SUMMARY APPRAISALS OF THE NATION'S GROUND-WATER RESOURCES 

93° 

j 

i 

92° 91° 

EXPLANATION 

Yield of wells 

(in gallons per minute) 

l'E3 0-50 

- 50-500 

0 More than 500 

111111111 Only saltwater available 

90° 

Base from U.S. Geological Survey, 1965 

United States base map, 1965 

0 50 100 150 200 250 KILOMETERS 

~~',~'1',~'~,1~,~~~~----~~-~r---~1----~1 I 

0 50 100 150 MILES 

FIGURE 10.-Ranges in well yields throughout the region; only in small areas do wells yield less than 500 gallons per 

minute (modified from Boswell, 1975). 
LOWER MISSISSIPPI REGION N15 

aquifers are present at moderate depths and water 

levels have been practically unaffected by pumping. 

Other Cretaceous aquifers are important in some 

areas where they are the best or only sources of 

ground water available. In north-central Mississippi 

and parts of west Tennessee, the Coffee Sand is 

utilized. It is the best or only source of ground water 

in many places in this area where the underlying 

Eutaw Formation is too thin or yields highly mineralized water, or where Paleozoic rocks do not contain 

aquifers. The Gordo Formation underlies the Eutaw 

Formation in north-central Mississippi, primarily 

south of the downdip limit of the Coffee Sand. Water 

in the Gordo Formation generally is good quality and 

is the best available in this area. 

Tertiary aquifers under lie virtually the entire 

Lower Mississippi Region, except for three small areas 

on the western border, two in Arkansas and one in 

Missouri, and a small strip on the eastern border in 

Tennessee and Mississippi. The Tertiary aquifers 

north of a line approximately through Vicksburg, 

Miss., to Colfax, La., are of Eocene age. South of this 

line, Miocene aquifers overlie the Eocene deposits. 

These beds dip southward and are, in turn, overlain 

by Pliocene deposits south of the 31st parallel. 

The significant Eocene aquifers, in ascending order 

of their occurrence, are: the lower Wilcox aquifer, the 

Carrizo Sand (and its stratigraphic equivalent, the 

Meridian Sand Member of the Tallahatta Formation), 

the Sparta Sand, and the Cockfield Formation. 

The lower Wilcox aquifer, the basal unit of the Wilcox Group, occurs throughout the northern one-third 

of the Lower Mississippi Region and in a strip across 

central Arkansas. It crops out in a narrow belt in 

north -Mississippi and west Tennessee (Fort Pillow 

Sand in the subsurface of west Tennessee) and occurs 

as a subcrop beneath the Quaternary alluvium in Arkansas and Missouri. The lower Wilcox aquifer is a 

source of water for several cities in northeast Arkansas and northwest Mississippi. 

Except for the lower Wilcox aquifer, the Tertiary 

aquifers mentioned previously are in the Claiborne 

Group. The basal unit of the Claiborne is the Carrizo 

Sand in Arkansas and Louisiana and its equivalent in 

Mississippi, the Meridian Sand Member of the 

Tallahatta Formation. This unit crops out in a narrow 

band in central Mississippi and southwest Arkansas 

and is a relatively minor aquifer in central Arkansas 

and in west Mississippi north of the latitude of Vicksburg. Separating the Carrizo from the overlying 

Sparta Sand is the Cane River Formation and its 

equivalents, composed mostly of clay and a few thin 

beds of fine, almost impermeable sand. The Cane 

River and its equivalents contain only very minor 

aquifers in south-central and southwest Arkansas and 

in west-central Mississippi. In northwest Mississippi, 

the Winona Sand (equivalent to the Cane River Formation) becomes more significant and merges into the 

Memphis aquifer. The Sparta Sand underlies the entire central part of the region. It crops out on the eastern side in a wide belt, from southwest Kentucky 

through Tennessee and Mississippi, and on the west 

side in northeast and south-central Arkansas. The 

Sparta occurs as subcrops beneath the Quaternary al-. 

luvium in some areas in Arkansas and Mississippi. 

The Sparta is a very productive aquifer throughout 

the northern three-fourths of the region. The Cook 

Mountain Formation, which is not an aquifer, overlie~ 

the Sparta Sand and separates it from the uppermost 

unit of the Claiborne Group, the Cockfield Formation. 

The Cockfield Formation directly underlies the 

Quaternary alluvium in most of the central part ofthe 

region. It includes productive aquifers in Arkansas, 

Louisiana, and Mississippi. The Cockfield crops out in 

small areas in southeast Arkansas, along the ArkansasLouisiana State boundary, in northwest Louisiana, 

and in central Mississippi. 

North of approximately the 35th parallel, the Memphis aquifer (Memphis Sand in Tennessee) comprises 

all Claiborne units from the base of the Carrizo Sand 

to the top of the Sparta Sand. This part of the 

Claiborne section is a massive sand several hundred 

feet thick which constitutes a vast ground-water reservoir. As such, the Memphis aquifer is second only 

to the Mississippi River valley alluvial aquifer as a 

potential source of large quantities. of ground water. 

Aquifers of Oligocene age in the Forest Hill Sand 

and the overlying Vicksburg Group occur in a small 

area in the southern half of the Lower Mississippi Region. These aquifers, although they are not extensive, 

are the only sources of fresh ground water in the 500 

ft (150 m) or more of sediments between the top of the 

Claiborne Group and the base of the Miocene Series. 

Aquifers of Miocene age occur south of a line approximately through Vicksburg, Miss., to Colfax, La. 

South of approximately the 31st parallel, the Miocene 

deposits are overlain by the Pliocene Series. These 

two series are lithologically similar and are referred 

to in Louisiana, where they occur together, as the 

Mio-Pliocene aquifer. In Mississippi, the Miocene deposits are divided into the undifferentiated upper 

Miocene aquifer and the Catahoula Sandstone. Both 

the Miocene and Pliocene Series are overlain by 

Quaternary deposits and, except for Miocene outcrops 

in west-central and southwest Louisiana, are not exposed at the surface. Both of these series are good 

present and potential sources of moderate to large 

quantities of fresh ground water. Near the Louisiana 
N16 SUMMARY APPRAISALS OF THE NATION'S GROUND-WATER RESOURCES 

coast, water in both series becomes salty gulfward. 

Deposits of Quaternary age cover most of the Lower 

Mississippi Region. Sediments of Pleistocene and 

Holocene age compose the Mississippi River valley 

alluvial aquifer, the most extensive source of ground 

water in the region. The Pleistocene deposits contain 

gravel at the base, grading upward to finer sand, and 

are the most productive parts of the aquifer. The overlying Holocene material is composed of very fine sand, 

silt, and clay. In many areas it forms a confining layer, 

although it is permeable to varying degrees. 

Large quantities of water are available from the 

Mississippi River valley alluvial aquifer throughout 

most of the region. The aquifer's value is enhanced in 

that, generally, only shallow well depths are required, 

pumping lifts are small, and recharge conditions are 

favorable. Throughout most of the Lower Mississippi 

Region, recharge to the alluvial aquifer is by precipitation. In some areas, where overlying fine-grained 

materials are nearly impermeable, the aquifers are 

recharged by underflow. Along the coast in Louisiana, 

especially in the southeastern part of the State, the 

alluvial aquifer contains saltwater. 

Ground water can be obtained with relative ease 

almost everywhere in the Lower Mississippi Region. 

For this reason, most public, industrial, and agricultural supplies are from wells. In most areas within the 

region, obtaining adequate quantities of water from 

surface-water supplies would be economically unfeasible. Ofthe total102,400 mi2 (265,200 km2 ) within the 

Lower Mississippi Region, about 5 percent is covered 

by surface water. In contrast, 90 percent of the region 

is underlain by two or more aquifers that can yield 

100 gal/min (6L/s) or more to individual wells. 

In contrast to surface reservoirs that inundate 

many acres of land, large quantities of water are 

stored in subsurface reservoirs without loss of surface 

area. Some disadvantages of surface reservoirs are 

high construction costs, cost of land purchase, loss of 

land use, and maintenance. Another consideration is 

that some terrain is not suited for large reservoir construction. Much of the area within the southern half 

of the Lower Mississippi Region could be classified as 

unsuitable because of the absence of deep, broad 

stream valleys that could be dammed. For these reasons, much dependence is placed on the region's subsurface reservoirs. 

LARGE AMOUNT AVAILABLE 

Approximately 347,000 billion ft 3 (9,800 billion m3 ) 

of water, containing less than 3,000 mg/L dissolved 

solids, is stored in the subsurface of the Lower Mississippi Region. This quantity of water is more than 16 

times the average annual surface-water outflow from 

the region, and if contained in a reservoir it would 

cover an area the size of the entire region to a depth of 

120 ft (37 m). Of this total, about 844 billion ft 3 (24 

billion m 3) is available annually for development, 

based on withdrawals consistent with economically 

and environmentally acceptable water-level declines. 

The primary containars of ground water in the 

lower Mississippi Region are the extensive unconsolidated sand-and-gravel aquifers of Tertiary and 

Quaternary age. The ability of these aquifers to store 

and transmit water varies due to differences in thickness and hydraulic conductivity. However, single 

aquifers that can yield 500 gal/min (32 L/s) or more to 

individual wells underlie about 90 percent of the region (fig. 10). The highest yields, often several thousand gallons per minute, are from wells screened in 

sand and gravel of the Quaternary alluvial-terrace 

deposits. The alluvial and terrace deposits account for 

two-thirds of the potential ground-water supply in the 

region. 

Within most of the Lower Mississippi Region, 

water-table aquifers commonly discharge water to 

streams that are connected with them (fig. 11A). Also, 

some streams that have sufficient hydraulic connection with a confined aquifer may receive contributions 

from the aquifer. Such a condition occurs when the 

altitude of the water surface in the stream is less than 

the head (potentiometric surface) in the aquifer (fig. 

11B). Under dry, low-flow conditions, perennial 

streams are sustained completely by discharged 

ground water. The lowest flow that occurs in a stream 

for 7 consecutive days once every 10 years is commonly accepted to be composed of discharged ground 

water. U.S. Geological Survey stream-gaging stations, 

within the region, where the 7-day, 10-year low-flow 

has been defined, are shown in figure 12. Table 1 contains the 7-day, 10-year low-flows for the stations 

plotted in figure 12. 

Where there is good connection between a major 

stream and an aquifer, advantage can be taken of the 

relationship by locating wells near the stream. When 

a well is pumped, one of two things will occur. If 

movement has been from the aquifer to the stream, 

gradients will flatten and may reverse in the vicinity 

of the well, utilizing water normally discharged to the 

stream and even taking water from the stream if the 

gradient reverses. If movement has been from the 

stream to the aquifer, the gradient will become 

steeper as the head in the aquifer near the well is reduced by pumping. In either instance, some water is 

diverted from the stream, thereby reducing the stress 

on the aquifer (fig. 13). 

Most aquifers in the Lower Mississippi Region are 

full; consequently much potential recharge is rejected 
A 

B 

LOWER MISSISSIPPI REGION 

Water table 

Water-table aq~Jifer 

Stream io hydraulic connection with a water-table aquifer. Under normal conditions the stream receives 

some water from the aquifer. 

Water-table aquifer 

The same stream during low-flow conditions. The only flow in the stream is ground-water discharge. 

surface -----------

Stream in hydraulic connection with an artesian aquifer. Under normal conditions the stream is receiving some water from the aquifer. 

surface 

._.------

The same stream during low-flow conditions. The only flow in the stream is ground-water discharge. 

FIGURE 11.-Ground water-surface water relations during normal and dry conditions. 

N17 

and evapotranspired or discharged to streams. When 

an aquifer is tapped and water is withdrawn, changing head relations can cause the aquifer to become receptive to recharge (fig. 14). Under the most favorable 
N18 SUMMARY APPRAISALS OF THE NATION'S GROUND-WATER RESOURCES 

0 I' I I 

0 

50 

I I I 

!'10 

100 

I 

150 

I 

I 

100 

200 

I 

EXPLANATION 

A7- 2895 Continuous-record gaging station., Numeral beside 

symbol is abbreviated station number 

250 Kl LOMETERS 

I 

I 

150MILES 

Base from U.S. Geological Survey, 1965 

United States base map, 1965 

FIGURE 12.-Selected 7-day, 10-year low-flow sites. 
LOWER MISSISSIPPI REGION N19 

TABLE 1.-The 7-day, 10-year low flow at selected stream-gaging stations plotted in figure 12 

Number 

07022500 

07022600 

07023000 

07023500 

07023700 

07024000 

07024500 

07025500 

07026000 

07027500 

07028100 

07029100 

07029500 

07030050 

07030280 

07030500 

07031700 

07032000 

07037500 

07040100 

07040450 

07041000 

07042000 

07042500 

07044000 

07046600 

07047000 

07047500 

07047600 

07047800 

07047900 

07047902 

07047950 

07047970 

07076850 

07077000 

07077500 

07077700 

07077800 

07077930 

07264500 

07265000 

07265450 

07266000 

07268000 

07271000 

07274000 

07282000 

07283000 

07287000 

07288500 

07289500 

07290000 

Station 7-day, 10-yr low flow Name (ft3/s) 

Perry Creek near Mayfield, Ky ---------------------------- 0.0 Mayfield Creek at Mayfield, Ky ---------------------------- 0 Mayfield Creek at Lovelaceville, Ky ------------------------ 7.7 Obion Creek at Pryorsburg, Ky ---------------------------- 0 Obion Creek near Arlington, Ky -------------------------- 3.3 Bayou du (de) Chien near Clinton, Ky ---------------------- 6.3 South Fork Obion River near Como, Tenn ------------------ 79 North Fork Obion River near Union City, Tenn ____________ 90 

Obion River at Obion, Tenn -------------------------------- 260 South Fork Forked Deer River at Jackson, Tenn ____________ 80 South Fork Forked Deer River near Halls, Tenn ____________ 145 North Fork Forked Deer River at Dyersburg, Tenn __________ 93 

Hatchie River at Bolivar, Term ---------------------------- 122 Hatchie River at Rialto, Tenn ------------------------------ 284 Loosahatchie River at Brunswick, Tenn -------------------- 58 

Wolf River at Rossville, Tenn ------------------------------ 124 Wolf River at Raleigh, Term ------------------------------ 158 Mississippi River at Memphis, Tenn ------------------------ 99,000 St. Francis River near Patterson, Tenn -------------------- 14.7 St. Francis River at St. Francis, Ark ---------------------- 76 St. Francis River at Lake City, Ark ------------------------ 97 Little River Ditch 81 near Kennett, Mo -------------------- 15 Little River Ditch 1 near Kennett, Mo ---------------------- 17 Little River Ditch 251 near Lilbourn, Mo ------------------ 30 Little River Ditch 251 n~ar Kennett, Mo -------------------- 69 Right Hand Chute of Little River at Rivervale, Ark ________ 146 St. Francis River floodway near Marked Tree, Ark __________ 0 

St. Francis River at Marked Tree, Ark -------------------- 97 Tyronza River near Tyronza, Ark -------------------------- 27 St. Francis River at Parkin, Ark -------------------------- 284 St. Francis Bay at Riverfront, Ark ------------------------ 38 St. Francis River at latitude of Wittsburg, Ark ______________ 405 

L'Anguille River at Palestine, Ark ------------------------ <.1 Mississip_pi River at Helena, Ark -------------------------- 102,000 

Cypress Bayou near Beebe, Ark ---------------------------- 0 White River at DeValls Bluff, Ark ------------------------ 4,830 Cache River at Patterson, Ark ---------------------------- 33 Bayou DeView at Morton, Ark ---------------------------- <.1 White River at Clarendon, Ark ---------------------------- 3,530 

Big Creek near Moro, Ark -------------------------------- 0 Bayou Meto near Stuttgart, Ark ---------------------------- 0 Crooked Creek near Humkhrey, Ark ------------------------ 0 Mississippi River near Ar ansas City, Ark __________________ 115,000 

Cane Creek near New Albany, Miss ------------------------ .4 Tallahatchie River at Etta, Miss -------------------------- 8.6 Clear Creek near Oxford, Miss ---------------------------- 4.2 Yocona River near Oxford, Miss ---------------------------- 7.2 Yalobusha River at Calhoun City, Miss ____________________ <.1 

Skuna River at Bruce, Miss -------------------------------- 2.0 Yazoo River at Greenwood, Miss -------------------------- 720 Sunflower River at Sunflower, Miss ------------------------ 94 Big Black River at Pickens, Miss -------------------------- 41 Big Black River near Bovina, Miss ------------------------ 75 

management conditions, withdrawal should not be 

greater than average annual recharge. 

Ground water has a low evaporation loss compared 

with surface water. Evaporation loss varies with the 

hydraulic conductivities of materials overlying the 

water-bearing zone and approaches zero as water 

levels deepen. 

The same protective covering that minimizes evaporation losses from ground water also tends to filter 

the water and protect it from contamination under 

natural conditions. However, this attribute should not 

be taken too much for granted. For example,, the 

dumping of concentrated pollutants in or near recharge areas, or the discharge of such pollutants into 

streams that may be recharging an aquifer, could 

have drastic effects on the quality of water in the 

aquifer. 

Water-well development, operation, and maintenance are relatively economical in most of the Lower 

Mississippi Region. With two or more freshwater 

aquifers underlying most of the region, good-quality 

Number 

07290650 

07291000 

07292500 

07295000 

07356000 

07356500 

07357000 

07359500 

07359800 

07360000 

07360800 

07361000 

07361200 

07361500 

07361600 

07362000 

07362100 

07362500 

07363000 

07363300 

07363500 

07364100 

07364150 

07364200 

07364300 

07364700 

07365000 

07365500 

07365800 

07365900 

07366200 

07367000 

07367700 

07368000 

07368500 

07369000 

07369500 

07370000 

07370500 

07371000 

07372000 

07372200 

07372500 

07373000 

07375000 

07375500 

07376000 

07376500 

07378500 

07381500 

07385500 

08012000 

08015500 

Station 

Name 

7-day, 10-yr low flow (ft3/s) 

Bayou Pierre near Wi.llows, Miss -------------------------- Homochitto River at Eddiceton, Miss ----------------------

Homochitto River at Rosetta, Miss -------------------------- Buffalo River (Bayou) near Woodville, Miss ----------------

Ouachita River near Mount Ida, Ark ---------------------- South Fork Ouachita River at Mount Ida, Ark -------------- Ouachita River near Mountain Pine, Ark ------------------ Ouachita River near Malvern, Ark ------------------------ Caddo River near Alpine, Ark ------------------------------ Ouachita River at Arkadelphia, Ark ------------------------ Muddy Fork Creek near Murfreesboro, Ark _______________ _ 

Little Missouri River near Murfreesboro, Ark -------------- Ozan Creek near McCaskill, Arlt -------------------------- Antoine River at Antoine, Ark ---------------------------- Little Missouri River near Boughton, Ark ------------------ Ouachita River at Camden, Ark ---------------------------- Smackover Creek near Smackover, Ark -------------------- Moro Creek near Fordyce, Ark ---------------------------- Saline River at Benton, Ark ------------------------------ Hurricane Creek near Sheridan, Ark ---------------------- Saline River near Rye, Ark -------------------------------- Ouachita River near Arkansas-Louisiana State Line _______ _ 

Bayou Bartholomew near McGee, Ark ---------------------- Bayou Bartholomew near Jones, La ------------------------ Chemin-a-Haut Bayou near Beekman, La ------------------ Bayou de Loutre near Laran, La -------------------------- Bayou D'Arbonne near Dubach, La ------------------------ Middle Fork Bayou D'Arbonne near Bernice, La ___________ _ 

Cornie Bayou near Three Creeks, Ark ---------------------- Three Creeks near Three Creeks, Ark ---------------------- Little Corney Bayou near Lillie, La ------------------------

Ouachita River at Monroe, La ------------------------------ Boeuf River near Arkansas-Louisiana State line ------------ Boeuf River near Girard, La ------------------------------ Big Colewa Bayou near Oak Grove, La -------------------- Bayou Lafourche near Crew Lake, La ---------------------- Tensas Bayou at Tendal, La -------------------------------- Bayou Macon near Delhi, La ------------------------------ Castor Creek near Grayson, La ---------------------------- Garrett Creek at Jonesboro, La ---------------------------- Dugdemona River near Winnfield, La ---------------------- Little River near Rochelle, La ------------------------------ Bayou Funny Louis near Trout, La ------------------------

Big Creek at Pollock, La ---------------------------------- Tchefuncta River near Folsom, La -------------------------- Tangipahoa River at Robert, La ---------------------------- Tickfaw River at Holden, La ------------------------------ Natalbany River at Baptist, La ---------------------------- Amite River near Denham Springs, La -------------------- Atchafalaya River at Krotz Springs, La -------------------- Bayou Teche at Arnaudville, La ---------------------------- Bayou Nezpique near Basile, La ---------------------------- Calcasieu River near Kinder, La --------------------------

19 

31 

140 

20 

6.0 

0 

19 

73 

13 

110 0 

3.6 

0 

0 

27 

175 .1 

0 

1.1 

.1 

11 

780 4.5 

39 

<.1 

2.4 

.1 

.1 

<.1 

<.1 

.1 780 

21 

17 

0 

4.6 

4.0 

33 

<.5 

0 

.2 16 

<.1 

6.9 

35 

270 

23 

2.5 290 24,000 

90 .4 200 

water in adequate amounts generally can be obtained 

at moderate depths. Thus, construction and pumping 

costs tend to be moderate. 

ACCEPT ABLE FOR MANY USES 

The quality of ground water in the Lower Mississippi Region varies from aquifer to aquifer and in 

some instances with geographic or vertical location 

within the aquifer. However, at almost any location 

within the region, ground water that has a total 

dissolved-solids concentration of less than 1,000 mg/L 

can be obtained (fig. 15). The exceptions are areas 

along the Louisiana coast and a small area in westcentral Louisiana, where all the ground water is 

saline to varying degrees. The prevalent chemical 

types and dissolved-solids concentrations of water in 

the shallow aquifers control the quality of water in 

streams at low flow (figs. 16, 17). 

Under most conditions, the quality of water in an 

aquifer will remain unchanged. If the ground water 

being withdrawn is of good quality, with proper man-
N20 SUMMARY APPRAISALS OF THE NATION'S GROUND-WATER RESOURCES 

Well 

Water surface 

Water-'table ·aquifer 

If a pumping well is located near a losing stream, increased quantities of water will move 

from the stream to the aquifer in the vicinity of the well. 

Well 

Artesian aquifer 

Well 

Water table 

Water-table aquifer 

If a pumping well is located near a gaining stream, the direction of movement of water in 

the vicinity of the well may change and water normally discharged to the stream will be 

utilized by the well. 

FIGURE 13.-Utilization of streamflow by nearby wells. 
LOWER MISSISSIPPI REGION 

Precipitation on the outcrop provides 

recharge to the aquifer 

Pressure in the aquifer is great enough to maintain a head above the water-surface altitude in streams connected with the 

aquifer; therefore most potential recharge is discharged to the streams before it can move downdip. 

Precipitation on 

the outcrop 

When water is withdrawn from the aquifer, pressure (and, thus, head) is reduced, allowing previously 

rejected potential recharge to move downdip . 

FIGURE 14. -Full aquifers reject recharge; movement of water downdip increases with utilization of the aquifer. 

N21 
N22 SUMMARY APPRAISALS OF THE NATION'S GROUND-WATER RESOURCES 

0 50 100 150 200 I' I I I I I I I I i I 

0 50 

I I I 

100 

EXPLANATION 

Milligrams per liter 

c=J 0-1,000 

k I I 1,000-3,000 

.. Greater than 3,000 

Base from U.S. Geological Survey, 1965 

United States base map, 1965 

250 Kl LOMETERS 

I I 

150 MILES 

FIGURE 15.-Dissolved-solids concentration of available ground water (from Boswell, 1975). 
0 I' I I 

0 50 

LOWER MISSISSIPPI REGION 

EXPLANATION 

Calcium magnesium carbonate 

bicarbonate type 

Calcium magnesium sulfate 

chloride type 

- So:i~=b~::::s~~;e carbonate 

150 

I I 

100 

200 

I 

-

250 Kl LOMETERS 

I I 

150 MILES 

Sodium potassium sulfate 

chloride type 

Boundary line 

Base from U.S. Geological Survey, 1965 

United States base map, 1965 

FIGURE 16.-Prevalent chemical types of water in streams at low flow (modified from Rainwater, 1962). 

N23 
N24 SUMMARY APPRAISALS OF THE NATION'S GROUND-WATER RESOURCES 

93° 92° 

0 50 100 r I I I I I I I I I I I 

0 50 

150 200 

I I I 

100 

EXPLANATION 

500 700 900 

Milligrams per liter 

Base from U.S. Geological Survey, 1965 

United States base map, 1965 

250 Kl LOMETERS 

I I 

150 MILES 

FIGURE 17. -Prevalent dissolved-solids concentration of water in streams at low flow (modified from Rainwater, 1962). 
LOWER MISSISSIPPI REGION N25 

agement it is quite likely to remain so; if the ground 

water being withdrawn requires treatment, it is not 

likely that, with proper management, treatment 

facilities will have to be changed significantly due to 

changes in the ground-water quality. 

Ground water is believed to be generally free of bacteria and chemical pollution. This belief is generally 

valid because ground water moves through natural 

soil and rock filtering media which can reduce natural 

bacterial pollution to almost zero. No widespread occurrence of bacterial pollution of ground water in the 

Lower Mississippi Region has been observed. However, locally, individual wells may yield bacterially 

contaminated water due to faulty well construction or 

location. 

By definition, ground water is considered to be 

naturally "polluted" when natural mineral concentrations exceed established criteria for various uses; 

so, whether water from a particular aquifer is considered to be polluted depends upon the intended use. If a 

use problem arises, it can generally be solved by 

treatment of the water or, in some places, by tapping 

another available aquifer containing water that is 

more suitable. 

WHY ARE WE NOT GETTING MAXIMUM 

BENEFIT FROM GROUND WATER? 

INADEQUATE CONSIDERATION 

Although ground water is being widely utilized, regionally much of its potential is not fully realized. 

Because of flooding problems and the need for navigation, high priority has generally been given to detailed studies of the region's surface-water systems. 

As a result, steps have been taken to alleviate most of 

the severe flooding problems, and good watertransportation systems have been developed. The 

characteristics of most of the major streams in the region are well defined, and consequently the behavior 

of these streams during periods of flood and drought is 

reasonably predictable. 

Knowledge of the behavior of the region's subsurface water systems (aquifers) under natural or imposed stresses is also important in water resources 

management. The ability to predict with some precision the effects of additional ground-water development is needed. Data such as aquifer characteristics, 

interaquifer relations, and stream-aquifer relations 

must be available in order to make such predictions. 

At least as much effort should be made to define and 

control our subsurface waters as has been made to 

control our surface waters. Detailed ground-water 

studies, whose end results are predictive models, cover 

only small parts of the Lower Mississippi Region (fig. 

18). 

There is a general lack of public awareness of the 

overall significance of ground water and the possible 

widespread effects of ground-water development. 

Many times the proper information is not sought or is 

not properly analyzed before a ground-water-related 

development is started. There is also a lack of public 

awareness concerning specific problems, such as the 

possible impact upon the local ground-water regime of 

certain seemingly unrelated activities, such as land 

clearing, excavations, and the proximity of sewage 

facilities to shallow wells. 

IMPROPER DEVELOPMENT 

Improper ground-water development.may entail one 

or any combination of the following: 

1. Drilling below the base of freshwater. 

2. Finishing a well above the most suitable aquifer. 

3. Locating a well too near other pumping wells. 

4. Locating a well too near a source of contamination. 

5. Overdevelopment. 

Some of these development problems may be due to an 

information deficit, as mentioned in the preceding section, but often available information is adequate but 

it is not given due consideration. 

Sometimes when a new well is drilled, available information is not considered to determine the depth of 

the water best suited to the need. Drilling below the 

base of freshwater, for example, is generally a waste 

of time and money (fig. 19A) and will increase the 

chances of well contamination, as head is reduced by 

pumping (fig. 19B). Of course, the reverse is also true; 

when a driller does not have adequate knowledge of 

the section he is drilling, he may stop short of the best 

water-bearing zone. 

Deep test holes, such as those drilled by oil companies, commonly pass through both freshwater 

aquifers and aquifers containing undesirable water 

(fig. 20A). If these holes are not properly plugged, they 

may become conduits through which undesirable 

water may leak into the freshwater zones that have 

lower hydrostatic heads (fig. 20B). Such leakage has 

caused saltwater pollution in local areas in the Lower 

Mississippi Region. The Mississippi River valley alluvial aquifer in northeast Louisiana has experienced 

some saltwater pollution due to leaky abandoned 

wells (Whitfield, 1975). 

Interference between wells occurs when they are located too near each other and are screened in the 

same aquifer. The cones of depression, sometimes 

termed "zones of influence," created by continued 

withdrawal from the wells, may coalesce. This condi-
N26 SUMMARY APPRAISALS OF THE NATION'S GROUND-WATER RESOURCES 

0 50 100 I' I I I I I I ) I I t 

0 50 

150 200 I I I 

100 

250 Kl LOMETERS 

I I 

150 MILES 

EXPLANATION 

Detailed coverage by intensive studies 

such as analog or digital modeling 

Relatively detailed coverage by inventory 

or appraisal studies 

Generalized coverage by reconnaissance 

studies 

Base data only 

Base from U.S. Geological Survey, 1965 

United States base map, 1965 

FIGURE lB.-Delineation of areas covered in ground-water-related reports. 
LOWER MISSISSIPPI REGION N27 

Land surface surface 

FIGURE 19.-Disregard of available information can be expensive economically and ecologically. 

0 "' 

.l: 

FIGURE 20.-Abandoned, deep test holes cause contamination by interaquifer water exchange if not properly plugged. 
N28 SUMMARY APPRAISALS OF THE NATION'S GROUND-WATER RESOURCES 

tion will significantly reduce the amount of water the 

aquifer will yield to these wells. Observe wells A, B, 

and C shown in figure 21. Well A depicts a very poor 

location for a new well; well B depicts a fair location, 

if pumping is not increased significantly from either 

the new or the existing well; well C depicts the best 

location of the three for the conditions indicated. 

The development of a new water-supply well for a 

city within the region provides an example of both 

poor well spacing and disregard of information about 

the depth of the best water-bearing zone available. 

The city's existing water supply is from two wells 

screened at depth intervals of 365 ft (111 m) to 405 ft 

(123 m) and 370 ft (113 m) to 410 ft (125 m), in the 

upper part of the Claiborne Group. These wells each 

produce about 600 gal/min (38 Lis). About 300 ft (91 

m) from one of these existing wells, the new supply 

well has been drilled to a depth of 575ft (175m). This 

well is screened in the 364-ft (111-m) to 398-ft (121-m) 

interval, the same water-bearing zone as the existing 

wells. It is intended that the well produce 1,000 gall 

min (63 Lis), which is the capacity of a new watertreatment plant that the city is now building. Before 

the well was screened, a gamma-ray log, run by the 

Factory 

~'~" 

Geological Survey on the pilot hole, indicated the 

presence of a possible aquifer 120 ft (37 m) thick 

below the lower confining layer of the thin (35 ft to 45 

ft or 11 m to 14m) aquifer now being used. Based on 

the piezometric surface in other wells tapping this 

aquifer, the pressure in this lower aquifer would have 

been sufficient to cause flow at ground surface. Further testing could have determined the potential of 

this lower sand. 

Some wells are located too near freshwatersaltwater interfaces. When withdrawals are made 

from such wells, head(pressure) in the vicinity of the 

well is reduced, allowing saltwater to move toward 

the well. This problem can be avoided or possibly 

solved if adequate information about the aquifer is 

available. Although saltwater is the most common 

pollutant associated with ground water in the Lower 

Mississippi Region, the proximity of proposed well 

sites to other sources of contamination should be carefully considered before locating a well. 

"Overdevelopment" of an aquifer is a relative term. 

In local areas where water levels have been lowered 

enough to significantly increase pumping lifts and 

costs, the term "overdevelopment" is often applied (fig. 

Good 

location 

Fair 

location 

FrGURE 21. - A simplified sketch of how a well location should be selected. 
LOWER MISSISSIPPI REGION N29 

22). If water levels around such pumping centers continue to decline, the zone of influence will spread, resulting in increased pumping costs for users in the 

area even though they do not significantly contribute 

to the cause of the decline. I 

Another cause of some loss in artesian pressure in 

aquifers within the region is the practice of allowing 

some naturally flowing wells to flow to waste. In 

southwest Arkansas, many wells that tap Cretaceous 

aquifers originally flowed at and above the land surface. Very few of these wells were capped and today, 

due at least in part to this waste, heads in these wells 

have dropped considerably and many of them have 

ceased to flow. 

FRACTIONAL USE OF AVAILABLE SUPPLY 

The availability of fresh ground water varies 

throughout the Lower Mississippi Region (fig. 9). Because annual ground-water withdrawal in the region 

is about one-third of the annual amount available (fig. 

23), rejected potential recharge constitutes a loss of 

water that would have entered the subsurface (fig. 14) 

if storage space were available. A maximum continuous withdrawal that could be sustained from an 

aquifer would be that quantity of water necessary to 

reduce the hydrostatic pressure and maintain it at 

such a level that the con trolling factor on recharge to 

the aquifer becomes either the amount of recharge 

available or the ability of the aquifer to transmit 

water. 

As desalinization technology advances and as more 

uses are found for saltwater, the amount of usable 

ground water that is available in the region will increase several times. Utilization of saltwater will 

have a twofold effect-a reduction in demands placed 

upon freshwater aquifers, making more freshwater 

available for uses requiring better quality water, and 

a reduction of pressure in saltwater zones, thus allowing more freshwater to be withdrawn near saltwater 

interfaces without inducing coning or encroachment 

problems. 

HOW CAN WE OBTAIN MAXIMUM BENEFIT 

FROM GROUND WATER? 

Merely increasing the usage of ground water does 

not assure that the most benefit will be obtained from 

the available supply; in fact, unwise development 

could result in the opposite effect. The determination 

to protect, as well as utilize, ground water can prevent 

the waste that has resulted from misuse and mismanagement of some of our other natural resources. 

EXPAND INFORMATION BASE, AND USE IT 

Ground-water management in the future should 

consider not only the local aspects of a planned development but also the regional framework into which 

the development must fit. To do this there should be 

an adequate information base containing at least the 

following kinds of data: physical and hydraulic conditions within the aquifers, the quality of water in the 

aquifers, and interaquifer hydraulic relations. 

Comprehensive planning or the development of 

proper planning tools cannot be done without knowing the size and properties of the ground-water container involved. The vital statistics of an aquifer that 

must be determined are its thickness, areal extent, 

configuration, and texture. Also, the quality of water, 

and any areal or vertical changes in quality within an 

aquifer, should be known. In addition to the physical 

features, the hydraulic conditions within the aquifer 

must be understood, that is, the movement of water as 

influenced by recharge and discharge. 

The hydraulic characteristics of an aquifer are those 

properties that determine its ability to store and 

transmit water. Aquifer characteristics, such as hydraulic conductivity and transmissivity, control the 

well yields, the amount of drawdown incurred to produce a specified yield, and the magnitude of waterlevel declines produced by pumping. With this information, the probable effects of a planned development 

can be predetermined, and well fields can be designed 

to minimize well interference. In addition, these 

aquifer characteristics can be used to estimate the 

gross yield available from an aquifer throughout a 

large area under a prescribed set of conditions. 

Interaquifer relations-the way aquifers interact 

hydraulically with one another-must also be determined regionally and locally. Some aquifers receive 

recharge through or from other aquifers. Confining 

beds may be sufficiently permeable to permit exchange of water between aquifers. The movement of 

water into an aquifer that is being pumped can significantly affect water levels and water quality. In 

fact, in some areas where such conditions exist, the 

quality of water in an aquifer may be manipulated by 

carefully planned pumping patterns and schedules. 

The extent of hydraulic connection between aquifers 

must be known for other reasons, too. For example, if 

poor-quality water or waste were to be injected into an 

aquifer for storage, a hydraulic connection with 

another aquifer could induce contamination of the 

second aquifer. Because of interaquifer hydraulic connections, aquifers considered to be separate entities 

locally may actually be part of a large system when 

considered regionally. 

Much of the information base needed for planning 

can be provided by regional aquifer studies. Such 

studies have been made in most of the Lower Missis-
N30 

r 

i 

I 

I 

29~+.- -------- 940 

SUMMARY APPRAISALS OF THE NATION'S GROUND-WATER RESOURCES 

---+20----

89° 

:0-~-30° ~u 1 

EXPLANATION 

POTENTIOMETRIC CONTOUR - Dashed 

where approximately located. Contour 

interval 40 feet (12 m). Datum is mean 

sea level. 

co" . Base from U.S. Geological Survey, 1965 

United States base map, 1965 

0 50 100 150 200 250 KILOMETERS 

~~~'TiLii-Li ~11-r-.1--~l ______ ~l-rl----~~----~~~1 

0 50 100 150 MILES 

FIGURE 22. -Areas where extensive lowering of water levels has occurred in the Sparta Sand in Arkansas and Louisiana (contours 

based on 1974-75 data) and in the Memphis Sand in the area of Memphis, Tenn. (contours based on 1973 data). 
LOWER MISSISSIPPI REGION N31 

>- 1200 

<( 

Q { 50 percent of a conservative estimate 1100 

a: 8000 of the dependable daily yield of w aquifers in the region (.) c.. 1000 iii Cl) 

z 7000 ::> 

0 (.) 

...J 900 z ...J 0 <( 6000 800 ...J <!) ...J >- z - <( 0 700 ~ Q 

...J 5000 ~ a: ...J 600 • w 

~ w c.. CI)CI) 

~ 4000 500 ::> a: 

a:w w· w 1- Cl) 1-W ::> 3000 400 <( ~ 

a: ~ w 300 Q 

1- z <( 2000 ::> ~ 200 0 

Q a: 

z 1000 <!) 

::> 

0 100 

a: 

<!) 0 0 1900 1910 1920 1930 1940 1950 1960 1970 

YEARS 

FIGURE 23. -Estimated ground-water use. 

sippi Region. Most of the area north of the 32d parallel is included in studies of the water resources of the 

Mississippi embayment (Cushing and others, 1963, 

1964; Boswell and others, 1965, 1968; Hosman and 

others, 1968). The reports describe the Cretaceous, 

Tertiary, and Quaternary aquifer systems. Further 

studies by Payne (1968, 1970, 1972, 1975) describe the 

hydrologic significance of lithofacies of aquifers of the 

Claiborne Group in Arkansas, Louisiana, Mississippi, 

and Texas. Much of the information necessary for the 

development of predictive aquifer models is provided 

by these studies. The only major aquifer systems in 

the Lower Mississippi Region that have not been 

studied regionally are the vast coastal aquifers of 

Miocene, Pliocene, and Pleistocene age. 

A large amount of water-quality information is 

available in the Lower Mississippi Region, and regionally the water quality in the different aquifers is 

well known. Consideration of this information by 

water managers would help them in choosing a suitable source of water. However, the quality of the 

water in some aquifers varies in short distances, and 

substantial additional testing may be necessary at 

these localities. Water-quality testing is also advisable 

in the proximity of saltwater interfaces. Monitoring 

networks can be used to detect anticipated waterquality changes, such as an advancing saltwater 

front, before the change affects the pumping center. 

Information on water quality will become increasingly 

important as concerned management organizations 

seek measures to conserve and protect the resource. 

In addition to the regional aquifer studies mentioned previously, local ground-water studies have 

been, and are being, made throughout the region. The 

areas investigated range in size from a few square 

miles to one or more counties (or parishes) or a river 

basin. Most of these studies are conducted by the 

Geological Survey in cooperation with State agencies. 

Reports based on these studies, plus abundant data in 

Geological Survey and State agency files, represent a 

sizable background of ground-water information for 

the region. Additional investigations should be undertaken in areas within the region where information is 

insufficient, especially where only reconnaissance 

studies or basic data are available (fig. 18). These investigations should provide information concerning 

aquifer properties sufficient for the development of 

predictive aquifer models. 

USE MODERN TECHNOLOGY 

In the past, ground-water technology was almost 

entirely oriented toward locating and developing 

supplies of potable water. Little attention was given 

to the possible consequences of such developments. As 

the science evolved, techniques were developed (and 

are still being developed) that meant to our groundwater resource and its users what reforestation 

technology meant to our timberlands and the lumber 

industry. With proper use and coordination of these 

techniques and the continued development of new 

techniques, benefits from use of ground water will approach a maximum, and our ground-water resource 

will be protected for future users. 

AQUIFER MODELING 

Aquifer models are the best-available predictive 

tool for ground-water planners and managers. Among 

the early models was the analog type: using a network 

of resistors and capacitors to simulate hydraulic properties, it simulated electrically the effects of pumping 

,stresses on an aquifer. The early analog model was 

the predecessor of the digital model. Construction of 

the digital model has been made possible by the 

sophistication of the digital computer and the development of numerical methods for the solution of 

the equations of ground-water flow. Use of the digital 

model requires adequate knowledge of the physical 

and hydraulic properties of the aquifers, pumping information, and a history of water-level fluctuation for 

calibration of the model. After the model has been calibrated to reproduce verifiable results, the planner 

and manager can use it to predict the effect of proposed development upon the ground-water system. 

Models can also be used to predict the movement of a 

saltwater front or fluids injected into the aquifer. 
N32 SUMMARY APPRAISALS OF THE NATION'S GROUND-WATER RESOURCES 

Aquifer modeling is still in a relatively early stage of 

development, and the degree of sophistication of the 

technology is steadily increasing. 

Within the Lower Mississippi Region, four groundwater studies that utilized either analog or digital 

modeling techniques have been completed. Two additional studies are currently underway. Each of these 

studies was, or is being, conducted by the Geological 

Survey in cooperation with another Federal, or a 

State, agency. Two of the completed studies used only 

analog models. One of these completed studies predicted the effects that the imposition of navigation 

structures on the Arkansas River would have on the 

ground-water regime (Bedinger, 1970), and the other 

simulated water-level declines in the Sparta Sand in 

the Mississippi embayment (Reed, 1972). Two of the 

completed studies used only digital models. In the 

Ruston, La., area a digital model was used to predict 

the effects of projected pumping upon water levels in 

the Sparta Sand (Sanford, 1973). Digital models were 

used to predict the effects that the construction of 

locks and dams on the Red River in Louisiana would 

have upon ground-water levels in the Red River alluvial aquifer (A. H. Ludwig, oral comm., 1976). One of 

the ongoing studies will model the hydrology of the 

Bayou Bartholomew alluvial aquifer-stream system in 

Arkansas. Originally, an analog model was constructed (Broom and Reed, 1973); however, adequate 

controlling parameters could not be incorporated into 

the analysis by analog methods. Today, development 

of a more versatile digital model is underway. The 

other ongoing study will determine, with the aid of a 

digital model, the effects of pumping stress upon 

ground-water levels in the Memphis Sand in the area 

of Memphis, Tenn. 

ARTIFICIAL RECHARGE 

Artificial recharge may be used to augment natural 

recharge. It has been used to salvage excess 

streamflow and has also been applied to problems associated with ground-water development, such as 

overdevelopment and subsidence. Artificial recharge 

is done by two basic methods: (1) impounding surface 

water where it can infiltrate a permeable part of the 

aquifer that is exposed at land surface and (2) injecting water into the aquifer through a well. 

A method that combines injection with surfacewater impoundment has been tried in some areas outside the Lower Mississippi Region, primarily in the 

West, with only limited success. In such experiments, 

playa lakes with relatively impermeable beds were 

used as catch basins. Wells drilled through the lake 

bottom and into the aquifer were intended to allow 

the accumulated water that otherwise would be lost to 

evaporation to drain by gravity into the aquifer. Problems with well plugging, both at the intake and in 

the screened interval, reduced the efficiency of this 

method to an unacceptable level. Whether or not this 

hybrid technique could be made feasible in the Lower 

Mississippi Region might be worth investigating. 

Extensive experiments in which treated surface 

water was injected into the Quaternary aquifer in the 

Grand Prairie region of Arkansas were conducted by 

Sniegocki and others (1963). Heavy pumping for rice 

irrigation had depleted the ground-water supply in 

the shallow aquifer, and natural recharge to the 

aquifer was impeded by an extensive overlying clay 

layer. The conclusions of the experimental study were 

that the costs of the extensive treatment necessary to 

render raw surface water suitable for injection, without plugging the well screen or the aquifer, are 

economically prohibitive with present technology. 

However, well injection may become feasible in the 

Lower Mississippi Region, either through some 

technological advance or by locating a compatible 

combination of aquifer conditions and a surface-water 

recharge source of such quality that the cost of treatment to prevent well-screen and aquifer plugging 

would be acceptable. 

At present, water spreading seems to offer the best 

hope for artificial recharge at places where water 

levels have been drawn down in the recharge area and 

where excess surface water is readily available. Aside 

from possible technical problems, a major consideration may be the high cost or unavailability of 

adequate land for water spreading. However, recharge 

by water spreading should be given consideration as a 

management option, wherever additional replenishment to the aquifer would be beneficial. 

BLENDING OF WATER 

The blending of waters from more than one source 

can enable the use of water that would require treatment if used by itself. The waters to be blended could 

come from different aquifers or from ground and surface sources if the waters are chemically compatible. 

The resulting concentration of chemical constituents 

in the blend will be in direct proportion to the quantity of each of the contributed waters. For example, a 

blend containing equal amounts of two types of water 

would have an average chemical composition of the 

two. 

Considering the types of ground water in the Lower 

Mississippi Region, water blending could prove to be 

an extremely beneficial practice. The hard, high-iron, 

low-chloride water in the Quaternary aquifers is plentiful in most of the region; however, the water generally requires treatment for iron removal and soften-
LOWER MISSISSIPPI REGION N33 

ing. A soft, high-chloride, low-iron water occurs at 

depth in most aquifers; this water generally remains 

unused because of the difficulty in lowering the 

chloride concentration to acceptable levels. A blending 

of these two waters would dilute the iron concentration of one, the chloride concentration of the other, 

and produce an intermediate hardness. Blends could 

be designed that would require little or no treatment 

for most uses. Excesses in iron, chloride, and hardness 

represent the most common chemical-quality problems with ground water in the Lower Mississippi Region. Before considering a water blend, competent professional advice should be sought to determine the 

chemical compatibility of the different waters. 

CONTROL AND USE OF SALTWATER 

The potential for saltwater encroachment exists 

where withdrawals are large in the proximity of saltwater interfaces. However, if it is necessary to plan a 

large development of wells near an interface, techniques are avaihible for maintaining a dependable 

supply of freshwater at the pumping center. 

Barrier wells, either discharge or recharge, have 

been the most successful means of arresting saltwater 

encroachment. In a discharge-well system, a line of 

pumping wells between the saltwater front and the 

pumping center intercepts the migrating saltwater 

and forms a low-pressure trough in the potentiometric 

surface beyond which the saltwater cannot pass. The 

water discharged by the barrier wells will become increasingly salty. If the saltwater cannot be used, it 

must be disposed of, possibly by injection into a 

deeper, saltwater-bearing aquifer. Recharge barrier 

North Discharge 

well 

Recharge 

well 

---....- / - " <Potentiometric 

surface as altered 

by. discharge - recharge well 

system 

South 

Land surface 

inal potentiometric 

surface 

~ Direction of water movement in aquifer 

FIGURE 24. -A discharge-recharge barrier well system to control 

saltwater encroachment (modified from Rollo, 1969.) 

wells, also located between the pumping center and 

the saltwater, require a supply of freshwater that is 

chemically compatible with water in the receiving 

aquifer. The injected water creates a high-pressure 

ridge in the potentiometric surface and retards the 

advancement of the saltwater. 

A barrier-well system, combining both discharge 

and recharge wells, has many attractive features and 

solves most of the problems created by either of the 

separate systems. In such a system, the discharge 

wells pump into the recharge wells, which are located 

between the discharge wells and the interface (fig. 24). 

Thus, both a high-pressure ridge and a low-pressure 

trough are formed as an effective barrier to the saltwater. The problems of disposal of water from the discharge wells and a source of compatible water for the 

recharge wells solve each other, and there is no net 

loss of water from the aquifer. Although this combined discharge-recharge barrier system is not known 

to have been tried, its practical features may make it 

the most economic long-term technique for arresting 

saltwater encroachment. 

Aside from functioning as a control tool, the combined barrier-disposal well system offers an additional 

application. Water from the discharge wells can be 

used elsewhere until it becomes too saline; then it can 

be diverted to the recharge wells. If the pressure ridge 

formed by the recharge wells effectively stops the 

progressive saltwater movement, water in the aquifer 

between the two lines of wells will gradually become 

fresh. When the chloride concentration in water from 

the discharge wells decreases to an acceptable level, 

the water can again be used elsewhere until it becomes too saline. The possibility that the combined 

barrier system could produce usable water cyclically 

is a distinct advantage over the discharge-well system 

that produces only saltwater. 

Saltwater also presents problems in areas where it 

underlies freshwater in an aquifer. This condition 

exists mostly in coastal aquifers, as a result of the 

gentle gulfward dip of the aquifers and the low angle 

of the freshwater-saltwater interface. In a thick sand, 

the area in which freshwater overlies saltwater can be 

large. A well screened in the upper (freshwaterbearing) part of the aquifer will produce freshwater. 

The length of time it will continue to produce freshwater depends upon the rate and duration of pumping, 

the hydraulic characteristics of the aquifer, and the 

proximity of the saltwater. When the well is pumped, 

water in the aquifer moves toward the well. The underlying saltwater moves upward and can eventually 

reach the well if it is pumped hard enough and long 

enough. One method of producing freshwater under 

these conditions is to use several low-producing wells 
N34 SUMMARY APPRAISALS OF THE NATION'S GROUND-WATER RESOURCES 

screened at the top of the aquifer. Although this 

method can be successful, it can also be expensive because of the number of wells and the amount of land 

required for proper well spacing. 

A more economical way to withdraw large quantities of freshwater from a zone that is underlain by 

saltwater is through the use of a scavenger well 

(Long, 1965). The scavenger well is installed next to 

the supply well, but it is screened lower in the aquifer. 

The supply well can be pumped until the saltwater 

reaches it. At this time, the scavenger pump is turned 

on to intercept the saltwater, and the supply well will 

then produce freshwater. Of course, the saltwater 

from the scavenger well must be disposed of. It could 

be injected into a deeper aquifer or possibly into the 

basal part of the same aquifer. The basic scavengerwell technique offers interesting opportunities for innovative approaches. 

RECYCLING 

The possibilities for recycling water, or returning it 

to the subsurface for reuse, must be considered in 

order to derive maximum benefit from the groundwater resource. The water used for many processes is 

only slightly altered, sometimes only thermally, and 

could be reused, reclaimed for reuse, put to other uses, 

or returned to the same or another aquifer. Recycling 

should become a standard practice as far as is feasible 

for the sake of conservation. The advantages of recycling should be emphasized now, rather than at some 

future time when a shortage may force conservation 

measures. 

GEOTHERMAL ENERGY 

Harnessing geothermal energy is a newly developing technology, insofar as the United States is concerned. Whether or not development of geothermalenergy resources is feasible in the Lower Mississippi 

Region has not been determined. In this area, extremely deep strata contain hot water as a result of 

the natural geothermal gradient. Experiments with 

hot water from an abandoned, deep gas well in southern Louisiana are being planned to determine the 

feasibility of geothermal development. If results of the 

study are favorable, this would indicate similar possibilities in approximately the southern one-third of 

the region. The only other known source of hot ground 

water in the region is in the Hot Springs, Ark., area. 

The temperature of the water issuing from the hot 

springs is 145°F (62°C), which is sufficient only for 

space heating. The heat source for the springs does 

not seem to be large, and hotter water probably would 

not be available by drilling. Tapping the source of the 

water at depth probably would diminish the natural 

flow of the springs (Bedinger and others, 1974), and 

whether or not the energy that might be available 

would offset the loss to the tourist industry is questionable. The deep-seated, superheated water in the 

southern part of the region seems to offer the best potential for geothermal energy sources and may be 

more economically accessible where abandoned, deep 

oil and gas wells are available. 

PLAN PROPERLY 

Proper planning will be the key to maximizing benefits from the ground-water supply in the lower Mississippi Region. Planning must include provisions for 

management so as to prevent waste and assure conservation and protection of the resource. Plans must 

be coordinated within the region, as well as with adjacent regions, because most of the aquifers cross regional boundaries. 

To coordinate work, planners should establish 

communications with all local, State, and Federal 

agencies that manage or investigate water resources 

(see following list). The main function of wateroriented agencies has been investigation. However, 

because of the need for planning and management, 

regulatory bodies are being formed and others are 

planned. Regulation should be based on cooperative 

planning by regions, States, and local districts in 

order to form workable management plans that account for hydrologic reality. 

The underlying philosophy for planning and management efforts should be to promote wise use, conservation, and protection of the ground-water resource. Conservation measures, such as reuse or recycling, pumping controls, and blending, should be 

combined with measures to protect the ground-water 

supply, primarily from man's activities. One potentially harmful activity is the underground injection of 

liquid wastes. Saltwater-bearing aquifers are generally considered to be suitable receptacles for waste. 

However, as the result of advances that are being 

made in developing economical desalinization techniques, saline aquifers may eventually become important sources of water. Therefore, in addition to the 

other indirect hazards associated with waste injection, 

such as leakage through wells or confining beds, there 

is also the risk of directly contaminating a potential 

water supply. These practices should be of as much 

concern as is the dumping of waste into streams or the 

Gulf of Mexico. 

Strip mining in the region is a possible future activity that should be evaluated for its potential effect on 

ground water. Most of the environmental concern 

with strip mining is about disturbance of the landscape; however, the geohydrologic effects could be far 

more serious. Mining companies now contemplate the 
LOWER MISSISSIPPI REGION N35 

Selected agencies within the Lower Mississippi Region that manage or investigate ground-water resources 

Arkansas 

Arkansas Department of Pollution Control and Ecology 

Arkansas Division of Soil and Water Resources 

Arkansas Geological Commission 

U.S. Geological Survey, Water Resources Division 

U.S. Army Corps of Engineers 

Louisiana 

Capitol Area Water Conservation Commission 

Capitol Region Planning Commission 

Louisiana Department of Public Works 

Louisiana Geological Survey 

U.S. Geological Survey, Water Resources Division 

U.S. Army Corps of Engineers 

Mississippi 

Mississippi Air and Water Pollution Commission 

Mississippi Board of Water Commissioners 

Mississippi Geological Economic and Topographical Survey 

Mississippi Research and Development Center 

Mississippi State Board of Health 

Environmental Protection Agency 

U.S. Geological Survey, Water Resources Division 

U.S. Army Corps of Engineers 

Tennessee 

Chickasaw Basin Authority 

Memphis, Arkansas, Tennessee Council of Governments, Memphis 

Delta Development District (MATCOG MDDD) 

Memphis Department of Public Works 

Memphis Light, Gas, and Water Development 

Memphis Planning Commission 

Memphis-Shelby County Health Commission 

Shelby County Conservation Board 

Utility Districts in cities in west Tennessee 

Tennessee Department of Health 

Division of Water Quality Department 

Division of Solid Waste Management 

County Health Superintendents 

Tennessee Division of Water Resources 

U.S. Geological Survey, Water Resources Division 

U.S. Army Corps of Engineers 

Kentucky 

Department for Natural Resources and Environmental Protection 

Kentucky Geological Survey 

U.S. Geological Survey, Water Resources Division 

U.S. Army Corps of Engineers 

Missouri 

Missouri Department of Natural Resources 

U.S. Geological Survey, Water Resources Division 

U.S. Army Corps of Engineers 

removal of as much as 200ft (61 m) of overburden in 

order to mine small lignite layers. The current emphasis on locating new sources of energy has 

awakened interest in mining coal from deposits that 

heretofore have been considered uneconomical to develop. The Wilcox Group is such a deposit; it consists 

of complexly interbedded sands, silts, clays, and thin 

lignite beds. The sands are water bearing and are interconnected to varying degrees. Large, deep excavations in Wilcox deposits would act as sumps and would 

drain the sands. Such draining could have widespread 

effects, which would be difficult to predict, depending 

upon the size of the excavation and the extent and degree of hydraulic connection between the sands. The 

effects of such drainage would range from lowering 

the water level in aquifers to the removal of ground 

water from a sizable part of the aquifer system, thus 

endangering many existing wells, as well as future 

well development. Drainage of freshwater-bearing 

sands into excavation sites could also adversely affect 

the quality of the ground water downdip from the excavation by introducing contaminated water into the 

aquifer or by inducing the advance of saltwater into 

freshwater zones. Much of the damage to the 

ground-water regime caused by strip mining may be 

irreversible. Although refilling the excavations would 

help to restore the esthetic quality of the area, the 

continuity and interconnection of aquifers necessary 

to conduct recharge downdip probably could not be 

reestablished. 

Conservation of ground water should go beyond 

eliminating the more obvious forms of waste, such as 

disposing of usable water once it has served a purpose. 

Water is also wasted when a superior-quality water is 

used where an inferior-quality water would sufficefor example, using potable water for industrial cooling. Obviously, if only one or two aquifers are available for supply in an area, there may be little or no 

choice as to which aquifer is to be used for which purpose. However, at most locations in the Lower Mississippi Region, several aquifers (fig. 8) that contain 

water of differing chemical quality are available. 

Under such conditions, water-use priorities keyed to 

water quality should be established for different-use 

categories. Each category would be assigned water of 

the lowest acceptable quality; however, drinking 

water would be assigned the top priority. 

It is apparent that there is a need to plan carefully 

for the use of ground water. The resource is of no 

value unless used, and it should receive its due consideration. However, while use of ground water is to 

be encouraged, care must be taken to prevent its 

abuse. Development should be guided by sound precepts. The consequences of other planned activities 

that could affect the ground-water regime should be 

weighed carefully as are the more commonly recognized environmental consequences. Ground water is 

an unseen part of the environment but, like the visible part, it must not be neglected. 

WHAT ARE THE POSSIBLE CONSEQUENCES OF 

INCREASED GROUND-WATER USE? 

When considering the development of ground-water 

supplies, managers should not overlook possible consequences to the resource. Development of largeproducing wells without an adequate knowledge of the 

aquifer system could result in undesirable changes in 

the system. These changes may be in the hydraulics of 

the system, in the quality of water in the aquifer, and 

(or) in the framework of the water-bearing unit. 
N36 SUMMARY APPRAISALS OF THE NATION'S GROUND-WATER RESOURCES 

HYDRAULIC CHANGES 

When a well is pumped, the water level in the vicinity of the well is lowered. The lowering of the water 

level may be temporary if the pumping is cyclical or 

seasonal, or it may be permanent if the pumping is 

continuous. If recharge to the aquifer is increased or 

discharge is decreased to compensate for the water 

discharged from the well, the water level in the vicinity of the well should stabilize. Otherwise, the water 

level will continue to decline, and pumping lifts and 

pumping costs will increase. 

Water levels in several aquifers have been lowered 

in sizable areas of the Lower Mississippi Region. The 

aquifers most affected are the Sparta Sand and the 

Memphis aquifer in Louisiana, Arkansas, and Tennessee (fig. 25). Other affected aquifers include the 

upper Wilcox in northwest Mississippi, the lower Wilcox at Memphis, Tenn., the Chicot-Atchafalaya 

aquifer near Lake Charles, La., and alluvial deposits 

of Quaternary age in the Grand Prairie region in 

Arkansas. 

Normally, aquifers in the Lower Mississippi Region 

are recharged by streams only during high flows. 

Ground water discharges to streams during normal 

and low flows. However, continuous pumping from an 

aquifer in the vicinity of a stream may reverse the 

hydraulic gradient so that water is demanded from 

the stream (fig. 13). Inducing the flow of water from a 

stream to the aquifer can be of benefit if the stream 

carries sufficient quantities of water to meet both the 

normal surface-water demands and the demands of 

aquifer recharge. 

Where an aquifer over lies another and the two are 

separated by a confining layer, movement of water 

from one aquifer to the other is minimal if a near balance of pressure (head) exists in the aquifers. When 

water is pumped from one of these aquifers, the head 

imbalance between the aquifers may induce flow 

through the confining layer. After continuous pumping, a stable pumping level will be reached in the 

receiving aquifer at a higher level than would be 

reached in the absence of recharge from the adjacent 

aquifer. Also, the head will be reduced in the contributing aquifer even if this aquifer is not being pumped 

directly. Reports by Hosman and others (1968), Whitfield (1975), and Boswell (1979) have pointed out several areas in the Lower Mississippi Region where 

water moves from one aquifer to another through a 

confining layer. 

WATER QUALITY CHANGES 

Where aquifers are hydraulically connected, as discussed previously, and where pumping of one aquifer 

has induced a change in the flow system, waterquality changes may occur. Inducing flow from a 

stream to an aquifer may also cause changes in the 

quality of water in the aquifer. Because the ground 

water generally will be of better quality than water in 

the stream, any significant change will probably be 

detrimental. However, an improvement in quality 

could result if water in the stream is of exceptionally 

good quality. Changes in quality should be carefully 

considered before inducing recharge from streams or 

from other aquifers. 

Saltwater encroachment could occur in many places 

in the Lower Mississippi Region. Northward saltwater 

migration has been occurring for several years in the 

Chicot aquifer in southwest Louisiana due to pumpage in the Lake Charles area (Zack, 1971). However, 

the movement of saltwater thus far observed is small. 

Many aquifers in the interior of the Lower Mississippi Region contain saltwater downdip. Under 

natural conditions, the saltwater is either virtually 

static or is moving very slowly downdip. However, 

heavy pumping of these aquifers near the saltwaterfreshwater interface can reverse the hydraulic gradient and cause saltwater to move toward the point of 

withdrawal. This condition has occurred in the vicinity of Baton Rouge, where heavy industrial pumping 

has caused northward movement of saltwater in several aquifers (Rollo, 1969). In at least one place, the 

saltwater is moving across a fault south of the area of 

pumping. Conversely, the same fault acts as a barrier 

and protects some other aquifers from saltwater encroachment (fig. 26). Although saltwater has been 

moving toward the withdrawal point, no saltwater has 

yet migrated into the zone affected by pumping. The 

dense saltwater in the basal part of the aquifer appears to take a circuitous rout6 because of irregularities in the base of the aquifer. Because the nature of 

these irregularities is not known, the time required 

for the saltwater to reach pumping centers is not predictable with any degree of accuracy. 

AQUIFER-FRAMEWORK CHANGES 

Large water-level declines caused by withdrawals of 

ground water may result in major changes in the 

framework of an aquifer. Major aquifers in the Lower 

Mississippi Region are composed principally of sand 

and gravel interbedded with clays and silts, and when 

large amounts of water are withdrawn, the finegrained materials can become compacted. 

Land-surface subsidence is the most visible effect of 

compaction due to pumping. In areas outside the region, land surfaces have been lowered in amounts 

ranging from a few feet to a few tens of feet. In the 
w 

(.) 

<( 

LL. 

a: 

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en 

Q 

z 

<( 

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s: 

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en 

a: 

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~ 

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w 

w 

LL. 

z 

-'. 

w 

> 

w 

-' 

a: 

w 

1-

<( 

s: 

70 (21) 

90 (27) 

110 (34) 

130 (40) 

150 (46) 

30 (9) 

50 (15) 

70 (21) 

90 (27) 

110 (34) 

100 (30) 

140 (43) 

180 (55) 

220 (67) 

180 (55) 

220 (67) 

260 (79) 

300 (91) 

340 (104) 

80 (24) 

120 (37) 

160 (49) 

200 (61) 

240 (73) 

280 (85) 

..... 

M 

0') 

LOWER MISSISSIPPI REGION 

Well in Memphis Sand at Memphis, Tenn. 

Depth 488 feet ( 149 m) 

Well in Sparta Sand near Stuttgart, Ark. 

Depth 929 feet (283m) 

High irrigational us1~ 

Well in Sparta Sand at Pine Bluff, Ark. 

0 

~ ~ 

Depth 906 feet (276m) 

High industrial and irrigational use 

Well in Sparta Sand at El Dorado, Ark. 

0 

LO 

0') 

~ 

Depth 540 feet ( 165 m) 

LO 

LO 

0') 

~ 

0 

co 

0') 

~ 

Composite of wells in Sparta Sand at Ruston, La. (after Sanford, 197.3) 

Municipal use (declines dut3 

mostly to industrial 

pumping in surrounding 

areas) 

32Q(98)ULULUD~~~~~~~~~~~~~~~~~~~~ 

LO 0 0 0 0 0 0 0 

~ m ~ ~ ~ ~ ~ ~ 

FIGURE 25.-Water-level declines in observation wells in the Memphis Sand and Sparta Sand. 

N37 
N38 SUMMARY APPRAISALS OF THE NATION'S GROUND-WATER RESOURCES 

~ 

so 

\ 

\ \ 

\ 

I 1+-

<::) 

~ L; 'f. 

I 

• I I I 

\ 0 1 2 

I ·,• I I I 

0 1 2 3 MILES 

N 

I 

EXPLANATION 

u --0---

Fault 

Dashed where inferred 

U, up thrown side; D,downthrown side 

~ 

Saltwater front 

--40--

Water level in feet below (-) 

or above(+) mean sea level 

Dashed where approximately 

located. Interval 20 feet 

(60 meters1 

___. Inferred direction of 

water movement 

Area where aquifer is 

thin or missing 

• 

Proposed test-drilling site 

1965-66 

FIGURE 26.-Saltwater front, water-level contours, and location of fault in the "2,000-foot" sand as determined during the 1965 

test-drilling program in the Baton Rouge, La., area (from Meyer and Rollo, 1965). 

San Joaquin Valley of California, for example, withdrawals of water for irrigation have allowed compaction of fine-grained materials to the extent that by 

1972 the land surface had subsided as much as 29ft (9 

m). More than 5,000 mi2 (13,000 km2 ) in the valley 

have been affected (Poland and others, 1975). Subsidence can cause damage to roadways and structures 

and allow innundation of low-lying coastal areas. 

Known subsidence in the Lower Mississippi Region 

has been confined to Baton Rouge, La., where large 

withdrawals of ground water have caused the land 

surface to subside a maximum of about 1.5 ft (0.5 m). 

In other areas in the Lower Mississippi Region, where 

hydrostatic pressures have been significantly lowered 

in sand-and-gravel aquifers, compaction probably has 

occurred as a result of drainage from underlying, 

overlying, and interbedded fine-grained materials. Although noticeable subsidence may not have been produced, deformation generally is accompanied by a 

permanent reduction in storage of water in the finegrained materials. Therefore, although subsidence is 

not a major problem in the Lower Mississippi Region 

at present, it should be regarded as a serious potential 

problem. 

IN SUMMARYIS THE OUTLOOK OPTIMISTIC? 

The outlook for additional ground-water use in the 

Lower Mississippi Region is bright. Multiple freshwater aquifers are available throughout most of the region. By conservative estimate, 844 billion ft 3 (24 billion m 3 ) of fresh ground water is available annually in 

the region. Today, nearly two-thirds of this available 

supply is not being utilized, and an additional large 

quantity of water is being lost-water that might 

have infiltrated the surface to become ground water if 

storage space were available. In other words, increased ground-water usage would not only allow 

ground-water benefits to more nearly approach a 

maximum but would also save some water that today 

cannot recharge the aquifers. 

Much of the ground water withdrawn and commonly termed ~~ground water used" could be used 

more than once or put to other uses. As existing 

water-oriented conservation techniques become more 

widely implemented and as new ones are developed, 1 

gallon of water withdrawn may become several gal-
LOWER MISSISSIPPI REGION N39 

Ions used. It is quite conceivable that in the future, 

with the implementation of such practices are recycling, reuse, injection of unaltered ground water back 

into the aquifer, and induced aquifer recharge from 

streams, annual ground-water use (including reuse) 

could exceed the quantity now estimated to be available annually. 

The quantity of subsurface saltwater available in 

the Lower Mississippi Region is several times that of 

freshwater. Further development and utilization of 

desalinization techniques would multiply the region's 

fresh ground-water supply several times. Furthermore, untreated saltwater may be used in some applications instead of freshwater; for example, at places, 

such as some areas of Louisiana, where saltwater 

occurs at shallow depths and is not too warm, it can 

be used for cooling purposes. 

To make maximum use of this vast quantity of 

ground water, adequate information about the subsurface reservoirs and the hydraulics of the system must 

be available. This information, as well as adequate 

legislation, is necessary in order to properly protect 

the quality of the ground water and the physical integrity of the aquifers. 

Today, there is an increasing awareness of the vital 

role that ground water plays in the total waterresources scene in the Lower Mississippi Region. 

Planning and management efforts are beginning to 

reflect this awareness. Interpretive and predictive investigations required by the water manager in order 

to make sound decisions have been, and are being, 

made in the region. Each State in the region maintains active water-resources-study programs of its own, 

as well as cooperative programs with other wateroriented agencies, including support of programs with 

the Geological Survey. All these agencies give considerable attention to ground-water resources. Increased 

cooperation between water-oriented agencies not only 

broadens the information base and helps prevent duplication of effort, but also stimulates new approaches 

to old problems and the recognition of areas where 

attention is needed. 

The technology and methodology for creating useful 

management tools for the water-resource manager 

have greatly advanced in the last 10 years. The 

sophistication of the digital computer and the development of digital-modeling techniques have made 

it possible, with adequate data, to make long-term 

stress-response predictions for a large area in a very 

short time. Also, methods are available for dealing 

with problems that may be encountered when utilizing the ground-water resource; for example, selective 

use based on water quality where multiple aquifers 

are available, barrier-well systems, scavenger wells, 

and artificial recharge. 

In the past, ground water and surface water were 

considered by many people to be separate entities that 

act and react independently. Today, such false ideas 

have been discarded, and the close and dependent relationship of the two resources is accepted. Total 

water-resource planning considers this relationship 

and the ways in which changes in one regime may 

affect the other. 

Each State in the Lower Mississippi Region has 

water laws that directly and indirectly concern 

ground water. These laws are changed and improved 

as legislators are made more aware of the immediate 

need for enforceable guidelines in ground-water development and protection. Each State has an agency 1

that is responsible for the identification and control of 

environmental pollution, including ground-water pollution. Some water-resources groups or agencies function on the local, county, or parish level. For example, 

in Louisiana, the Capital Area Ground-Water Conservation District encompasses a multiparish area in the 

Baton Rouge vicinity. The findings of the Louisiana 

Legislature that precipitated the organization of this 

conservation district are expressed in Article A of Section 3071, Part XIII, Chapter 13, Title 38, of the 

Louisiana Revised Statutes. The article states: uThe 

orderly utilization of groundwater resources is hereby 

found and declared to be a matter of public interest." 

The purpose of the conservation district is, as stated 

in Article B of the same section ttto provide for the 

efficient administration, conservation, orderly development and supplementation of groundwater resources***." The existence and resolve of such local 

groups is good; the extension of these concepts to a 

regional conservation organization concerned with 

ground-water planning and management would be 

even more compatible with the regional nature of 

ground-water occurrence. 

SELECTED REFERENCES 

Bedinger, M.S., 1970, Methods and applications of electrical simulation in ground-water studies in the lower Arkansas and Verdigris River valleys, Arkansas and Oklahoma: U.S. Geol. Survey Water-Supply Paper 1971, 69 p. 

Bedinger, M.S., Emmett, L. F., and Jeffery, H. G., 1963, Groundwater potential of the alluvium of the Arkansas River between 

Little Rock and Fort Smith, Arkansas: U.S. Geol. Survey 

Water-Supply Paper 1669-L, 29 p. 

Bedinger, M. S., Pearson, F. J., Jr., Reed, J. E., Sniegocki, R. T., and 

Stone, C. G., 1974, The waters of Hot Springs National Park 

Arkansas-Their origin, nature, and management: U.S. Geol. 

Survey open-file report, 102 p. 

Boswell, E. H., 1979, 1975 National Water Assessment: Ground 

water in the Lower Mississippi Region: Natl. Water Resources 

Council Rept. (in press). 

Boswell, E. H., Cushing, E. M., and Hosman, R. L., 1968, Quater-
N40 SUMMARY APPRAISALS OF THE NATION'S GROUND-WATER RESOURCES 

nary aquifers in the Mississippi embayment: U.S. Geol. Survey 

Prof. Paper 448-E, 15 p. 

Boswell, E. H., Moore, G. K., MacCary, L. M., and others, 1965, 

Cretaceous aquifers in the Mississippi embayment: U.S. Geol. 

Survey Prof. Paper 448-C, 37 p. 

Broom, M. E., and Reed, J. E., 1973, Hydrology of the Bayou Bartholomew alluvial aquifer-stream system, Arkansas: U.S. Geol. 

Survey open-file report, 91 p. 

Bull, W. B., 1964, Alluvial fans and near surface subsidence in 

western Fresno County, California: U.S. Geol. Survey Prof. Paper, 437-A, 71 p. 

Bull, W. B., and Miller, R. E., 1975, Land subsidence due to 

ground-water withdrawal in the Los Banos-Kettleman city 

area, California, Part 1. Changes in the hydrologic environment conducive to subsidence: U.S. Geol. Survey Prof. Paper 

437-E, 67 p. 

Committee on Geological Sciences, 1972, The earth and human affairs: San Francisco, Canfield Press, 138 p. 

Committee on Resources and Man, 1969, Resources and man: San 

Francisco, W. H. Freeman and Company, 239 p. 

Cushing, E. M., 1963, Water Resources and the Mississippi embayment: U.S. Geol. Survey Circ. 471, 8 p. 

Cushing, E. M., Boswell, E. H., and Hosman, R. L., 1964, General 

geology of the Mississippi embayment: U.S. Geol. Survey Prof. 

Paper 448-B, 28 p. 

Davis, R. W., Lambert, T. W., and Hanson, A. J., Jr., 1973, Subsurface geology and ground-water resources of the Jackson Purchase region, Kentucky: U.S. Geol. Survey Water-Supply Paper 

1987, 66 p. 

Dial, D. C., 1968, Water-level trends in southeastern Louisiana: 

Louisiana Geol. Survey and Dept. Public Works Water Resource Pamph. 22, 11 p. 

Eaton, W. R., 1958, Summary of flow duration and low flow at 

stream gaging stations in Tennessee: Tennessee Div. Geology 

and Div. Water Resources open-file report, 137 p. 

Flawn, P. T., 1970, Environmental geology: New York, Harper and 

Row, 251 p. 

Gabrysch, R. K., and Bonnet, C. W., 1975, Land-surface subsidence 

in the Houston-Galveston region, Texas: Texas Water Devel. 

Board Rept. 188, 19 p. 

Halberg, H. N., 1972, Use of water in Arkansas, 1970: Arkansas 

Geol. Comm. Water Resources Summ. 7, 17 p. 

Harrison, R. W., 1961, Alluvial empire: Little Rock, Ark., Pioneer 

Press, v. 1, 344 p. 

Hines, M. S., 1965, Water-supply characteristics of selected Arkansas streams: Arkansas Geol. Comm. Water Resources Circ. 9, 

43 p. 

--1975, Flow-duration and low-flow frequency determinations 

of selected Arkansas streams: U.S. Geol. Survey Water Resources Circ. 12, 75 p. 

Hosman, R. L., 1969, Geohydrology of the Coastal Plain aquifers of 

Arkansas: U.S. Geol. Survey Hydrol. Inv. Atlas HA-309. 

Hosman, R. L., Long, A. T., Lambert, T. W., and others, 1968, Tertiary aquifers in the Mississippi embayment: U.S. Geol. Survey 

Prof. Paper 448-D, 29 p. 

Long, R. A., 1965, Ground water in the Geismar-Gonzales area, Ascension Parish, Louisiana: Louisiana Geol. Survey and Dept. 

Public Works Water Resources Bull. 7, 67 p. 

Lower Mississippi Region Comprehensive Study Coordinating 

Committee, 1974: Lower Mississippi Region Comprehensive 

Study. 

Meyer, R. R., and Rollo, J. R., 1965, Salt-water encroachment, 

Baton Rouge area, Louisiana: Water Resources Pam ph. 17, 9 p. 

Moore, G. K., 1965, Geology and hydrology of the Claiborne Group 

in western Tennessee: U.S. Geol. Survey Water-Supply Paper 

1809-F, 44 p. 

Morgan, C. 0., and Winner, M. D., Jr., 1964, Salt-water encroachment in aquifers of the Baton Rouge area-preliminary report 

and proposal: Louisiana Dept. Public Works pub., 37 p. 

Newcome, Roy, Jr., 1975, The Miocene aquifer system in Mississippi: U.S. Geol. Survey open-file [map] report. 

Page, L. V., 1963, Water supply characteristics of Louisiana 

streams: Louisiana Dept. Public Works Techn. Rept. 1, April, 

109 p. 

Payne, J. N., 1968, Hydrologic significance of the lithofacies of the 

Sparta Sand in Arkansas, Louisiana, Mississippi, and Texas: 

U.S. Geol. Survey Prof. Paper 569-A, 17 p. 

--1970, Geohydrologic significance of lithofacies of the 

Cockfield Formation of Louisiana and Mississippi and the 

Yeyua Formation of Texas: U.S. Geol. Survey Prof. Paper 

569-B, 14 p. 

--1972, Hydrologic significance of lithofacies of the Cane River 

Formation or equivalents of Arkansas, Louisiana, Mississippi, 

and Texas: U.S. Geol. Survey Prof. Paper 569-C, 17 p. 

--1975, Geohydrologic significance of lithofacies of the Carrizo 

Sand in Arkansas, Louisiana, and Texas, and the Meridian 

Sand of Mississippi: U.S. Geol. Survey Prof. Paper 569-D, 11 p. 

Poland, J. F., Lofgren, B. E., Ireland, R. L., and Pugh, R. G., 1975, 

Land subsidence in the San Joaquin Valley, California: U.S. 

Geol. Survey Prof. Paper 437-H, 77 p. 

Rainwater, F. H., 1962, Stream composition of the conterminous 

United States: U.S. Geol. Survey Hydrol. Inv. Atlas HA-61. 

Reed, J. E., 1972, Analog simulation of water-level declines in the 

Sparta Sand, Mississippi embayment: U.S. Geol. Survey Hydrol. Inv. Atlas HA-434. 

Rollo, J. R., 1966, Ground-water resources of the greater New Orleans area, Louisiana: Louisiana Geol. Survey and Dept. Public 

Works Water Resources Bull. 9, 69 p. 

--1969, Salt-water encroachment in aquifers of the Baton 

Rouge area, Louisiana: Louisiana Geol. Survey and Dept. Public Works Water Resources Bull. 13, 43 p. 

Sanford, T. H., Jr., 1973, Water resources of the Ruston area, 

Louisiana: Louisiana Dept. Public Works Water Resources 

Tech. Rept. 8, 30 p. 

Skelton, John, 1966, Low-flow characteristics of Missouri streams: 

Missouri Geol. Survey and Water Resources Rept. 20, 95 p. 

Sniegocki, R. T., 1963, Problems in artificial recharge through wells 

in the Grand Prairie region, Arkansas: U.S. Geol. Survey 

Water-Supply Paper 1615-F, 25 p. 

--1964, Hydrology of a part of the Grand Prairie region, Arkansas: U.S. Geol. Survey Water-Supply Paper 1615-B, 72 p. 

Sniegocki, R. T., Bayley, F. H., III, and Engler, Kyle, 1963, Equipment and controls used in studies of artificial recharge in the 

Grand Prairie region Arkansas: U.S. Geol. Survey WaterSupply Paper 1615-C, 39 p. 

Sniegocki, R. T., and Reed, J. E., 1963, Principles of siphons with 

respect to the artificial recharge studies in the Grand Prairie 

region, Arkansas: U.S. Geol. Survey Water-Supply Paper 

1615-D, 19 p. 

Speer, P. R., Hines, M. S., Janson, M. E., and others, 1966, Low-flow 

characteristics of streams in the Mississippi embayment in 

northern Arkansas and Missouri: U.S. Geol. Survey Prof. Paper 

448-F, 25 p. 

Swisshelm, R. V., Jr., 1974, Low-flow characteristics of Kentucky 

streams: U.S. Geol. Survey open-file [map] report. 

Tharpe, E. J., 1975, Low-flow characteristics of Mississippi streams: 
LOWER MISSISSIPPI REGION N41 

Mississippi Board of Water Commissioners Bull. 75-1, 60 p. 

Thornthwaite, C. W., 1948, An approach to a rational classification 

of climate: The Geol. Rev., p. 55. 

U.S. Geological Survey, 1970, The National atlas of the United 

States of America: U.S. Geol. Survey, 417 p. 

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subregions for the national assessment of water and related 

land resources: Washington, U.S. Govt. Printing Office, 187 p. 

Whitfield, M. S., Jr., 1975, Geohydrology and water quality of the 

Mississippi River alluvial aquifer, northeastern Louisiana: 

Louisiana Dept. Public Works, Water Resources Tech. Rept. 10, 

26 p. 

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southwestern Louisiana, 1970, with a section on surface-water 

withdrawals: Louisiana Dept. Public Works Water Resources 

Pam ph. 27, 33 p. 

GP0689-035