The Nation's Water Resources, 1975-2000

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Second

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Water Assessment

U.S. Water Resource

by the

s Council Generated for member (North Carolina State University) on 2013-03-26 16:07 GMT / http://hdl.handle.net/2027/pur1.32754076370653 Public Domain, Google-digitized / http://www.hathitrust.org/access_use#pd-google r

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U.S. WATER RESOURCES COUNCIL

Secretary of the Interior,

Chairman:

Secretary of Agriculture:

Secretary of the Army:

Secretary of Commerce:

Secretary of Housing and

Urban Development:

Secretary of Energy:

MEMBERS

Secretary of Transportation:

Administrator. Environmental

Protection Agency:

ALTERNATES

Assistant Secretary of the Interior:

Assistant Secretary of Agriculture:

Deputy Under Secretary of the

Army:

Deputy Assistant Secretary of

Commerce:

Deputy Assistant Secretary of

Housing and Urban Development:

Assistant Secretary of Energy:

The Commandant, U.S.

Coast Guard:

Assistant Administrator,

Environmental Protection

Agency:

DIRECTOR

Director, Water Resources

Council:

Cecil D. Andrus

Bob Bergland

Clifford L. Alexander, Jr

Juanita M. Kreps

Patricia Roberts Harris

James R. Schlesinger

Brock Adams

Douglas M. Costle

Guy R. Martin

M. Rupert Cutler

Michael Blumenfeld

James W. Curlin

Yvonne S. Perry

George Mcisaac

Admiral J. B. Hayes

Thomas C. Jorling

Leo M. Eisel Generated for member (North Carolina State University) on 2013-03-26 16:07 GMT / http://hdl.handle.net/2027/pur1.32754076370653 Public Domain, Google-digitized / http://www.hathitrust.org/access_use#pd-google THE NATION’S WATER RESOURCES

1975-2000

Volume 4: Lower Mississippi Region

Second National

Water Assessment

by the

U.S. Water Resources Council

[§>

December 1978 Generated for member (North Carolina State University) on 2013-03-26 16:07 GMT / http://hdl.handle.net/2027/pur1.32754076370653 Public Domain, Google-digitized / http://www.hathitrust.org/access_use#pd-google I

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

Washington. D.C. 20402

Stock Number 052-045-00066-5 Generated for member (North Carolina State University) on 2013-03-26 16:07 GMT / http://hdl.handle.net/2027/pur1.32754076370653 Public Domain, Google-digitized / http://www.hathitrust.org/access_use#pd-google Foreword

The Water Resources Planning Act of 1965 (Public Law 89-80) directs

the U.S. Water Resources Council to maintain a continuing study of the

Nation's water and related land resources and to prepare periodic assess-

ments to determine the adequacy of these resources to meet present and

future water requirements. In 1968, the Water Resources Council reported

the results of its initial assessment. The Second National Water Assess-

ment, a decade later, provides a comprehensive nationally consistent data

base for the water resources of the United States. The results of the

Second National Water Assessment were obtained by extensive coordination

and collaboration in three phases.

Phase I: Nationwide Analysis

The Council member agencies researched, analyzed, and prepared esti-

mates of current and projected water requirements and problems and the

implications of the estimates for the future.

Phase II: Specific Problem Analysis

Regional sponsors, one for each of the 21 water resources regions,

surveyed. and analyzed State and regional viewpoints about (1) current

and future water problems, (2) conflicts that may arise in meeting State

and regionalobjectives,and (3)problemsandconflictsneeding resolution.

Phase III: National Problem Analysis

The Council conducted this final phase in three steps: (1) An evaluation

of phases I[ and II, (2) an analysis that identified and evaluated the

Nation's most serious water resources problems, and (3) the preparation

of a final report entitled "The Nation's Water Resources--1975-2000."

The final report of the Second National Water Assessment consists of

four separatevolumesznsdescribed below. These volumes can assist Fed-

eral, State, local, and other program managers, the Administration, and

the Congressimlestablishingauuiimplementing water resources policies and

programs.

Volume 1, Summary, gives aux overview of the Nation's water supply,

water use, andcriticalvmter problemsfor 1975, 1985, and 2000 and sum

marizes significant concerns.

Volume 2, Water Quantity, Quality, and Related Land Considerations,

consists of one publication with five parts:

Part I,"Introduction,"outlinesthe origin of the Second Nation-

al Water Assessment, states its purpose and scope, explains the

numerous documents that are part of the assessment, and ident-

i Generated for member (North Carolina State University) on 2013-03-26 16:07 GMT / http://hdl.handle.net/2027/pur1.32754076370653 Public Domain, Google-digitized / http://www.hathitrust.org/access_use#pd-google ifies the individuals and agencies that contributed to the as-

sessment.

II, "Water-Management Problem Profiles," identifies ten gen-

eral water problem issues and their implications and potential con-

sequences.

Part III, "Water Uses," focuses on the national perspectives re-

garding existing ("1975") and projected (1985 and 2000) require-

ments for water to meet instream, instream, and flow-management

needs. State-regional and Federal perspectives are compared.

Part IV, "Water Supply and Water Quality Considerations," analyzes

the adequacy of fresh-water supplies (ground and surface) to meet

existing and future requirements. It contains a national water

budget; quantifies surface- and ground-water supplies, reservoir

storage, and transfers of water within and between subregions;

describes regional requirements and compares them to supplies;

evaluates water quality conditions; and discusses the legal and

institutional aspects of water allocation.

Part V, "Synopses of the Water Resources Regions," covers existing

conditions and future requirements for each of the Zlwater re-

sources regions. Within each regional synopsis is a discussion of

functional and location-specific water-related problems; regional

recommendations regarding planning, research, data, and institu-

tional aspects of solving regional water-related problems; a

problem-issue matrix; and a comparative—analysis table.

Volume 3, Analytical Data, describes the methods and procedures used to

collect, analyze, and describe the data used in the assessment. National sum-

mary data are included with explanatory notes. Volume 31$ supplemented by

five separately published appendixes that contain data for the regions and

subregions;

Appendix I, Social, Economic, and Environmental Data, contains

the socioeconomic baseline ("1975") and growth projections (1985

and 2000) on which the water—supply and water—use projections

are based. This appendix presents two sets of data. One set,

the National Future, represents the Federal viewpoint; the other

set, the State—Regional Future, represents the regional sponsor

and-or State viewpoint.

Appendix II, Annual Water Supply and Use Analysis, contains base-

line water-supply data and baseline and projected water withdrawal

and water-consumption data used for the assessment. Also included

are a water adequacy analysis , a natural flow analysis , and a crit-

ical—month analysis.

Appendix III, Monthly Water Supply and Use Analysis, contains

monthly details of the water-supply, water-withdawal, and water-

H Generated for member (North Carolina State University) on 2013-03-26 16:07 GMT / http://hdl.handle.net/2027/pur1.32754076370653 Public Domain, Google-digitized / http://www.hathitrust.org/access_use#pd-google consumption data contained in Appendix II and includes an analy-

sis of monthly water adequacy.

Appendix IV, Dry-Year Conditions Water Supply and Use Analysis,

contains both annual and monthly baseline and projected water-

withdrawal and water-consumption data for dry conditions. Also,

a dry conditions water-adequacy analysis is included.

Appendix V, Streamflow Conditions, contains detailed background

information on the derivation of the baseline streamflow inform-

ation. A description of streamflow gages used, correction fac-

tors applied, periods of record, and extreme flows of record,

are given for each subregion. Also included is the State-Regional

Future estimate of average streamflow conditions.

Volume 4, Water resources Regional Reports, consists of separately

published reports for each of the 21 regions. Synopses of these reports

are given in Volume 2, Part V.

For compiling and analyzing water resources data, the Nation has been

divided into 21 major water resources regions and further subdivided into 106

subregions. Eighteen of the regions are within the conterminous United

States; the other three are Alaska, Hawaii, and the Caribbean area.

The Zlwater resources regions are hydrologic areas that have either

the drainage area of a major river, such as the Missouri Region, or the

combined drainage areas ofa series of rivers, such as the South Atlantic-

Gulf Region, which includes a number of southeastern States that have rivers

draining directly into the Atlantic Ocean and the Gulf of Mexico.

The 106 subregions, which are smaller drainage areas, were used exclu-

sively in the Second National Water Assessment as basic data-collection

units. Subregion data point up problems that are primarily basinwide in

nature. Data aggregated from the subregions portray both regional and

national conditions, and also show the wide contrasts in both regional and

national water sources and uses.

The Second National Water Assessment and its data base constitute a

major step in the identification and definition of water resources problems

by the many State, regional, and Federal institutions involved. However,

much of the information in this assessment is general and broad in scope;

thus, its application should be viewed in that context, particularly in the

area of water quality. Further, the information reflects areas of defici-

encies in availability and reliability of data. For these reasons, State,

regional, and Federal planners should view the information as indicative,

and not the only source to be considered. When policy decisions are to be

made, the effects at State, regional, and local levels should be carefully

considered.

In a national study it is difficult to reflect completely the regional

variations within the national aggregation. For example, several regional Generated for member (North Carolina State University) on 2013-03-26 16:07 GMT / http://hdl.handle.net/2027/pur1.32754076370653 Public Domain, Google-digitized / http://www.hathitrust.org/access_use#pd-google reviewers did not agree with the national projections made for their

regions. These disagreements can be largely attributed either to different

assumptions by the regional reviewers or to lack of representation of

the national data at the regional level. Therefore, any regional or State

resources-management planning effort should consider the State-regional

reports developed during phase II and summarized in Volume 4 as well

as the nationally consistent data base and the other information presented

in this assessment.

Additional years of information and experience show that considerable

change has occurred since the first assessment was prepared in 1968. The

population has not grown at the rate anticipated, and the projections of

future water requirements for this second assessment are considerably lower

than those made for the first assessment. Also, greater awareness of envi-

ronmental values, water quality, ground-water overdraft, limitations of

available water supplies, and energy concerns are having a dramatic effect

on water-resources management. Conservation, reuse, recycling, and weather

modification are considerations toward making better use of, or expanding,

available supplies.

iv Generated for member (North Carolina State University) on 2013-03-26 16:07 GMT / http://hdl.handle.net/2027/pur1.32754076370653 Public Domain, Google-digitized / http://www.hathitrust.org/access_use#pd-google CONTENTS

Physlogrephy

Description

Geology and Topography

Climate

People and the Resources

Population

Economy

Land Resources

Agriculture

Energy

Navigation

Environment

Water

Surface Flows

Ground Water

Water Withdrawals

Water Consumption

lnstream Uses

Water Supply and Demand

Comparative Analysis

Problems

Flooding

Navigation

Water Quality

Water Quantity

Erosion and Sedimentation

Water Surface

Environmental Quality

Coastal and Estuarine Areas

Excessive Wetness

Individual Problem Areas

Summary

Conclusions and Recommendations -ii

Illustrations

Figure 8-1. Region Map

Figure 8-2. Present Land Use

Figure 8-3. Navigation System

Figure 8-4. Environmental Resources

Figure 8-5. Streamflow

Figure 8-6. Major Aquifers

ﬁgure 8-7. Withdrawals and Consumption

Figure 8-8a. Problem Map

Figure 8-8b. Problem Matrix

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3 Generated for member (North Carolina State University) on 2013-03-26 16:07 GMT / http://hdl.handle.net/2027/pur1.32754076370653 Public Domain, Google-digitized / http://www.hathitrust.org/access_use#pd-google

35 Generated for member (North Carolina State University) on 2013-03-26 16:07 GMT / http://hdl.handle.net/2027/pur1.32754076370653 Public Domain, Google-digitized / http://www.hathitrust.org/access_use#pd-google VOLUME 4 | 1

Physiography

Description

The Lower Mississippi Region includes the drainage basin of the Missis-

sippi River below its confluence with the Ohio River, except for portions of

the Arkansas, Red, and White River subbasins above the backwater limits of

the Mississippi River. It also includes the Ouachita, Boeuf, and Tensas

Basins and the Louisiana coastal area which drains into the Gulf between the

Pearl and Sabine River divides (Figure 8-1). Its northern extremity near

Cairo, Illinois, is about 600 miles (954 miles traveling the Mississippi

River) inland from the Gulf of Mexico. The region averages 170 miles in

width. It encompasses a total area of approximately 105,140 square miles

(67.3 million acres) and includes portions of the States of Missouri,

Tennessee, Kentucky, Arkansas, Mississippi, and Louisiana (Figure 8-2).

About 4 percent of the area is water surface.

Geology and Topography

The Lower Mississippi River and its alluvial valley became deeply

incised in the coastal plains area during the last glacial advance of the

Pleistocene, when sea level was several hundred feet lower than at present.

During time subsequent to this period, the valley was gradually filled

with alluvium deposited by the river. The Mississippi has therefore been

a major influence in building and shaping the physical environment.

All of the region, except for the area of the Ouachita Mountains and

the Ozark Plateau, is located in the Central Gulf Coastal Plains Province.

This extensive lowland overlies unconsolidated sand, gravel, clay,

silt, marl, and limestone. The alluvial valley, containing about one-

third of the region's area, is a gently sloping and undulating lowland

bordering the river from Cape Girardeau, Missouri, to the Gulf.

East of the valley, an uplands area extends from the northern por-

tion of the region into southeastern Louisiana. The uplands area west

of the valley is less distinctive and more gently rolling. It extends

southward from the Arkansas River to within a few miles of Alexandria,

Louisiana.

The natural marshes stretch along the Louisiana coast and extend

about 35 miles inland from the Gulf. These marshes cover about 2.4 mil-

lion acres and include fresh, salt, and brackish water.

1 This is the sum of the areas of counties used to approximate the hydro-

logic area of the region. Land-use and other socioeconomic data are

related to this area. The drainage area within the hydrologic boundary

is 103,520 square miles. Generated for member (North Carolina State University) on 2013-03-26 16:07 GMT / http://hdl.handle.net/2027/pur1.32754076370653 Public Domain, Google-digitized / http://www.hathitrust.org/access_use#pd-google LOWER MISSISSIPPI REGION

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Present Land Use

Figure 8-2. Generated for member (North Carolina State University) on 2013-03-26 16:07 GMT (150ppi) / http://hdl.handle.net/2027/pur1.32754076370653 Public Domain, Google-digitized / http://www.hathitrust.org/access_use#pd-google 4 | LOWER MISSISSIPPI REGION

Both the Ouachita Mountains and the Ozark Plateau are located out-

side the Central Gulf Coastal Plains Province and are therefore quite

different topographically from the rest of the region. The terrain is

very rugged and elevations extend to 2,000 feet or more.

The Ozark Plateau in Missouri is an area characterized by sharply

dissected limestone plateaus, with narrow rolling ridgetops. Local relief

ranges from less than 100 feet to several hundred feet.

Climate

The climate of the region is humid and subtropical, except for the

northern part which is classified as temperate. Long, hot, humid summers

and short, moderate winters are experienced throughout most of the region.

Precipitation is abundant and well distributed, ranging from less than

50 inches in the extreme northern portions to more than 60 inches along

the southeastern coastal section (Figure 8-4). Although droughts do occur,

extended periods of severe drought are uncommon. In the northern portion,

maximum precipitation occurs during winter or early spring; in the southern

section, it occurs during the summer. Average annual runoff varies from

10 to 22 inches, with a regional mean of 16 inches.

January temperatures average 40° F in the north and 55° F in the south,

and average temperatures in July are 78° F and 82° F, respectively

(Figure 8-5). The Frost-free period ranges from 182 days in the extreme

north to 353 days in the extreme south.

Snow and sleet are minor throughout most of the region, averaging

from 12 inches in the extreme north to less than 1 inch from central Louisiana

southward.

Tornadoes are common in the region and occur primarily during April,

May, and June. Hurricanes and tropical storms are especially damaging

to the coastal area between May and October. These storms are sometimes

accompanied by violent winds in excess of 100 miles per hour, massive inun-

dations of broad sections of the coastal area 10 to 15 feet above mean gulf

level, and rainfalls of 10 inches to more than 20 inches in 24 hours, which

produce extensive flooding in interior areas. Generated for member (North Carolina State University) on 2013-03-26 16:07 GMT / http://hdl.handle.net/2027/pur1.32754076370653 Public Domain, Google-digitized / http://www.hathitrust.org/access_use#pd-google VOLUME 4 | 5

People and the Resources

Population

The Lower Mississippi Region historically has been rural, but recent

shifts in employment from agriculture to other types of work have resulted

in approximately 60 percent of the region's population living in urban

areas. This trend is expected to continue so that by the year 2000 about

70 percent of the population will live in urban areas. The large metropoli-

tan centers such as Memphis, Baton Rouge, and New Orleans are expected

to grow much faster than others, with these three urban areas alone projected

to include as much as one-half the region's population within the next

40 years.

The region's population in 1975 was 6.417 million people (3 percent

of the Nation's population). By the year 2000, the population is pro-

jected to increase to 7.142 million, an increase of 11 percent compared

to the projected national population increase of 24 percent.

Economy

Historically, economic activity in the Lower Mississippi Region has

been oriented toward the production of row and close-seeded crops, valuable

forest species, and livestock and livestock products. Although these

activities continue to play very important roles in the regional economy,

there has been a significant trend in recent years in industrial development

and a greater diversification and expansion of the economy. As a result,

emphasis has shifted from the agricultural base to other major forms

of activities, such as mining, quarrying, petroleum production, and the

manufacturing of food, chemical, and paper products. Between 1950 and

1970,for example, agricultural employment declined from 50 percent of

the regional total to only 10 percent, while employment in the manufacturing

groups tripled.

About 2.3 million people were employed in the region in 1975. The

1975 total personal income was about $30.7 billion or about $4,783 per

capita, compared to $6,233 per capita nationwide. Incomes were lowest

in Subregion 802, which averaged about $4,157 per capita, some 33 percent

lower than the national average. While per capita incomes are projected

to more than double by the year 2000, they will still lag behind the

Nation. Major earnings were from manufacturing, which accounted for

21.6 percent of the total. The "other" category shown in Table 8-1 includes

the following individual categories: wholesale and retail trade with 17

percent of the total regional earnings, government with 17 percent, and

services with 14 percent. Agriculture accounted for 9.7 percent of the

total regional earnings. Total earnings of the region are estimated to

have been $23.9 billion in 1975 and are projected to be $55.4 billion

by the year 2000, an increase of 131 percent. Generated for member (North Carolina State University) on 2013-03-26 16:07 GMT / http://hdl.handle.net/2027/pur1.32754076370653 Public Domain, Google-digitized / http://www.hathitrust.org/access_use#pd-google 6 | LOWER MISSISSIPPI REGION

Table 8-1.--Lower Mississippi Region earnings-1975, 1985, 2000

(million 1975 dollars)

Earnings A 1975 1985 2,000 ,

Manufacturing ------5,158 7,680 12,579

Agriculture ------2 ,309 2 ,286 2 ,670

Mining ------737 843 980

Other ------15, 680 23,079 39,212

Total ------23 ,884 33,888 55 ,441

The largest users of water in the region are in subregions 802 and

803'. Large pulp and paper mills are numerous in subregion 802, and

total water demand is four times that of subregion 801. In subregion 803,

with 1975 manufacturing earnings approximately equal those of subregion

801, the manufacturing sector is dominated by petroleum refineries and

petrochemical plants, and water demands are nearly 20 times as large

as those in subregion 801. In the assessment of the impact of industry on

the region's water resources, it is obvious that the mix of industries that

constitute the manufacturing sector is more important than the actual

manufacturing earnings of the sector.

Land Resources

The lands of the Lower Mississippi Region can support a diverse range

of land-dependent activities. Much of this capability is directly related

to the region's climate and abundant precipitation. Bumper dryland crops

are consistently produced on its rich delta soils without requiring irriga-

tion. About 40 percent of the region is forested, with both fast-growing

pine and high quality bottomland hardwoods covering extensive tracts. The

region's land cover supports a bountiful and diverse wildlife resource;

some species were more numerous prior to the arrival of the region's first

European settlers (Figure 8-3).

Land use is perhaps the best indicator of the state of development of

the land resources. In 1975, about 53 percent of the region's land was used

primarily for growing crops and raising livestock, and an additional 14

percent, although forested, was also used for grazing livestock. Land-use

categories are listed in Table 8-2.

'Subregions used in this report are shown on Figure 8-1. The boundary

of a subregion lies along the outer boundary of counties included in

the subregion. These boundaries are intended to approximate boundaries

of hydrologic subregions and generally do not conform to boundaries of

States. Generated for member (North Carolina State University) on 2013-03-26 16:07 GMT / http://hdl.handle.net/2027/pur1.32754076370653 Public Domain, Google-digitized / http://www.hathitrust.org/access_use#pd-google VOLUME 4 | 1

Agriculture

Agriculture has historically played a very important role in the

economy of Thelma Mississippi Region. This is one of the major food-

and fiber-producing areas in the Nation. Its output includes a variety

of high-yield cropsznuiforestspecies,livestock, and livestock products.

Table 8-2.--Lower Mississippi Region surface area and 1975 land use

Surface area or land use type 1,000 acres Percentage of

total surface area

Surface area

Total ------67,292 100.0

Water ------2,783 4.1

Land ------64,509 95.9

Land use

Cropland ------20,409 30.3

Pasture and range ------9,928 14.8

Forest and woodland ------27,099 40.3

Other agriculture ------3,828 5.7

Urban ------895 1.3

Otherl ------2,350 3.5

includes small water areas.

The thriving agricultural economy is largely due to a bountiful water

supply, good farmland, an abundant labor pool, and the water transport

system provided by the Mississippi River.

The forecasted reduction of the agricultural employment base is largely

the result of rapid gains in agricultural technology. By the year 2000

agricultural employment is expected to be about one-half the present level,

yet agricultural output is expected to increase almost 40 percent.

Crops now account for about 80 percent of marketing receipts, and

livestock livestock products make up the remainder. Soybeans, cotton,

rice, hay, and corn collectively constitute more than 90 percent of the

harvested acreage.

Since nearly 64 percent of the surface area of the region is classed

as suitableforagriculturalcropuse,thepotentialexistsfor even greater

production increases than are projected should demands for food and fiber

products generally increase.

In 1975, there were 20.4 million acres of cropland in the Lower Mississ-

ippi Region. By the year 2000, another 2.1 million acres of land will be

converted to cropland. About 89percentof the cropland in the region is

harvested. Irrigated cropland is expected to increase from 2.0 billion

acres to 2.9 million acres between 1975 and 2000 (Table 8-3). Generated for member (North Carolina State University) on 2013-03-26 16:07 GMT / http://hdl.handle.net/2027/pur1.32754076370653 Public Domain, Google-digitized / http://www.hathitrust.org/access_use#pd-google 8 | LOWER MISSISSIPPI REGION

Table 8-3.-—Projected changes in cropland and irrigated farmland in the

Lower Mississippi Region--1975, 1985, 2000

(1,000 acres)

Land category 1975 1985 2000

Total cropland ------20,409 21,919 22,538

Cropland harvested ------18,223 20,464 18,120

Irrigated farmland ------1,968 2,508 2,862

Energy

About 53,811 gwh of electric power was generated in the region in 1975;

99 percent was generated by 36 fossil fuel steam electric plants (Table 8-4) .

About 78 percent of the generating capacity employs once-through cooling

water, discharging 206 trillion Btu's per year to fresh surface waters

and 15 trillion Btu's to saline waters.

By the year 2000, it is projected that about 366,000 gwh of electric

power will be generated annually by seven nuclear and 29 fossil fuel

generating stations. At that time,50 percent of the generating capacity

will be employing once-through cooling. The heat discharged to fresh

surface waters will have decreased to 667 trillion Btu's per year; heat

discharged to saline water will increase to 404 trillion Btu's.

The Lower Mississippi Region maintains ea very important position

in the production of nneral fuels to umet the Nation's energy needs.

In 1969, regional mineral production accounted for a substantial part

of the Nation's liquid and gaseous fuel, specifically, 34 percent of the

natural gas output,31 percent of the natural gas liquids, and 25 percent

of the petroleum. 'Itis expected that the production of mineral fuels in

the region will nearly double by the year 2000.

Table 8-4.--Lower Mississippi Region electric power generation--1975,

1985, 2000

j (gigawatt-hours)

Fuel source j j ,1975 j 1985 2000 j

Fossil ------53,363 80,349 72,488

Nuclear ------0 40,140 293,220

Conventional hydroelectric power -- 448 365 365

Total generation ------53,811 120,854 366,073

Navigation

According tx>1975 State estimates, 345 million tons of commerce were

shipped over the navigable waterways of thelowerbflssissippiregion. This

comprised l out of every 5 tons of waterborne commerce in the United

States. In terms of ton-miles of commerce moved,the region accounted for

nearly 120 billion ton-miles, more than one-fourth the U.S. total. Most Generated for member (North Carolina State University) on 2013-03-26 16:07 GMT / http://hdl.handle.net/2027/pur1.32754076370653 Public Domain, Google-digitized / http://www.hathitrust.org/access_use#pd-google VOLUME 4 I 9

of this activity occurred on the Mississippi River and the Gulf Intra-

coastal Waterway and involved the port of New Orleans. Important commodities

moved were petroleum and petroleum products, industrial chemicals, grain

and grain products, iron and steel products, nonmetallic minerals, and

unprocessed marine shells.

The vast navigational network of the region includes the main stem of

the Mississippi River from Cairo, Illinois, to the Gulf, plus 12,000 miles

of shallow draft navigation channels. (Figure 8-3). From Cairo to Baton

Rouge (720 miles), the Mississippi River is maintained at a minimum depth

of 9 feet, and from Baton Rouge to the Gulf, the channel is maintained

at a minimum depth of 40 feet. An alternate deep-water route from New Orleans

to the Gulf is provided by way of the 76-mile tidewater channel, the Mis-

sissippi River-Gulf Outlet. In the southwest part of the region, a 35 mile-

long channel connects the port of Lake Charles with the Gulf. The Gulf

Intracoastal Waterway complements the Mississippi River system by providing

east-west access to shallow-draft traffic moving from Florida to the Texas-

Mexico border. The 300-mile segment that crosses the Lower Mississippi

Region is the hub of the waterway. In addition to these features, numerous

access channels and harbors are maintained along the Mississippi River and

other major streams, as well as along the coast.

The rapid growth of waterborne commerce and the transportation industry

has resulted in the improvement of more than 3,000 miles of waterways, the

expansion of existing facilities at 13 shallow-draft ports, and construction

of navigation locks at 20 locations.

The principal types of vessels on shallow-draft waterways are towboats

and tugs, barges, barge tows, and other craft such as fishing boats, oil

field crew and supply boats, and offshore construction and drilling vessels.

Deep-draft vessels have traditionally been grouped in three categories

as general cargo vessels, bulk carriers, and tankers. Today, a rapidly

changing marine technology has evolved--the container ship, the large

carrying vessel, and the combination oil-bulk-ore carrier. The conventional

general cargo vessels, which require a 500-foot berth and a transit shed

embracing about 4 acres of land, are giving way to the container ship,

which may require up to 800 feet of dock, plus a minimum of 22 acres of

marshaling and service area.

Environment

Human impact on land and water resources has altered the natural

environment, for better or worse. Adverse effects have resulted from the

clearing and drainage of land for cultivated crops and pastures, harvesting

of lumber, mining of mineral resources, and construction of roads, ditches,

recreational facilities, industrial sites, and urban and built-up areas.

These activities in varying degrees have displaced or eliminated wildlife,

increased water and air pollution levels, altered recreational values,

changed stream patterns, stripped forest lands, decreased soil productivity,

damaged or destroyed archeological and historical remains, and diminished

scenic and other esthetic values. Generated for member (North Carolina State University) on 2013-03-26 16:07 GMT / http://hdl.handle.net/2027/pur1.32754076370653 Public Domain, Google-digitized / http://www.hathitrust.org/access_use#pd-google 10 I LOWER MISSISSIPPI REGION

.___§§° 90"

us. WATER RESOURCES COUNCIL

LOWER MISSISSIPPI REGION

Arkansas

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Figure 8-3. Navigation System Generated for member (North Carolina State University) on 2013-03-26 16:07 GMT / http://hdl.handle.net/2027/pur1.32754076370653 Public Domain, Google-digitized / http://www.hathitrust.org/access_use#pd-google VOLUME 4 | 11

Not all human activities, however, have been harmful. The region

has been improved by various erosion-control measures and by the con-

struction of drainage and flood-protection works. Some manmade water

areas, such as navigation canals along the coast, barrow pits adjacent to

levees, and reservoirs, have added visual variety and scenic qualities to

the landscape and have often provided additional recreational opportuni-

ties. Major portions of the Ouachita Mountains area are still wild in

character, with few roads and a sparse population. Nearly 1-1/2 million

acres have been set aside in national forests, providing valuable wildlife

habitat and outdoor recreation opportunities. Thousands of acres of coastal

dunes, marshes, and wetlands remain relatively undisturbed and of good

environmental quality, providing habitat for many birds and small animals.

State and national parks throughout the region preserve areas of scenic,

historic, or recreational significance, and wildlife refuges and sanctuaries

in the region are among the world's largest.

A substantial portion of the region's surface-water area has been

identified as having significant environmental values because of natural

splendor, esthetic quality, or other attributes. Included are 446,000 acres

of lakes and about 28,000 acres of rivers and streams (or about 2, 363 miles).

About l out of every 3 miles of environmentally significant rivers and

streams has already been named in enacted or pending scenic rivers legis-

lation of the States, and virtually all of the lake acreage is under

some form of protective ownership or management. Many of the lakes,

in addition to their scenic attributes, harbor unique ecosystems. In

many instances, full enjoyment of scenic rivers and lakes is hampered by

the lack of legal access.

The region is also rich in archeological and historical resources.

The total number of archeological sites of man's early occupancy is un-

known, but more than 5,000 sites have been recorded to date and are

believed to represent but a small fraction of the total. Some 100 sites

have been excavated, but fewer than 12 have been extensively investigated.

Recent surveys have recorded some 2,400 sites in the region as historically

significant, of which 237 have been mapped. These include battlegrounds,

historic dwelling places, legendary sites, natural landscape features,

roads, trails, waterways, cemeteries, machines and manmade structures,

and cultural sites. In 1970 there were 176 sites listed in the National

and an additional 61 were recognized as historic assets by States of

the region.

Other important environmental features in the region include

wilderness areas, beaches and shores, wetlands, unique geological systems,

bottomland hardwoods, and open and green space. There is a total of

12.4 million acres of land in the region classified as environmentally

significant, 5.1 million acres of which are in need of additional management

or protection to insure their availability for the enjoyment of future

generations (Figure 8-4). Generated for member (North Carolina State University) on 2013-03-26 16:07 GMT / http://hdl.handle.net/2027/pur1.32754076370653 Public Domain, Google-digitized / http://www.hathitrust.org/access_use#pd-google 12 | LOWER MISSISSIPPI REGION

95» m__ _,______so»

U.S. WATER RESOURCES COUNCIL

T LOWER MISSISSIPPI REGION

LEGEND

IMPORTANT

I ENVI RONM ENTAL COM PONENTS

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Unique Ecological Systems

Wilderness Area

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Figure 8-4. Environmental Resources Generated for member (North Carolina State University) on 2013-03-26 16:07 GMT / http://hdl.handle.net/2027/pur1.32754076370653 Public Domain, Google-digitized / http://www.hathitrust.org/access_use#pd-google VOLUME 4 | 13

Water

The Lower Mississippi Region can be considered water-rich. It not

only receives abundant rainfall that replenishes ground water and feeds

its many interior streams and lakes, but also has vast untapped ground-

water reserves. Moreover, there is tremendous inflow to the region from

the huge drainable system of the upper Mississippi River and tributaries

and from the Arkansas, White, and Red Rivers. However, the fact that the

region has been endowed with a plentiful supply of water does not mean

that it is without management problems. Availability of water of the

quanitity and quality needed at specific locations at specific times often

causes serious problems in various locations throughout the region.

Surface Flows

The total area drained by the Mississippi River and it tributaries

covers more than 1,244,000 square miles and includes all or parts of

31 States and two Canadian provinces. Water from as far east as New York

and as far west as Montana flows into the lower Mississippi. This drainage

area constitutes 41 percent of the surface area of the conterminous United

States. Interior drainage from about 50,000 square miles within the

region flows into the Mississippi River through major tributary streams.

Most of the region's remaining area drains through the Ouachita, Boeuf,

and Tensas Basins to the Red River, and from there,into the Atchafalaya

River, which empties into the gulf. The Calcasieu, Mermentau, and Vermi-

lion Rivers west of the Atchafalaya River in southwestern Louisiana and

minor drainage basins in southeastern Louisiana also empty directly into

the gulf. The Amite, Tickfaw, Natalbany, Tangipahoa, and Tchefuncta Rivers

contribute water to the gulf by way of Lake Pontchartrain.

The total surface flow in the region in an average year under base

conditions is about 71,400 million gallons per day (mgd). An additional

361,600 mgd is contributed from other regions, resulting in a combined

yearly average outflow of about 433,000 mgd (Figure 8-5). Most of this

flow is discharged through the Mississippi River. In a dry year (80 percent

exceedance flow), the total flow in the region would be reduced to about

11,800 mgd. In a dry year, the total outflow, including the flow contrib-

uted by other regions, would be about 282,000 mgd. Extreme low flows

generally occur in late summer and early fall, while extreme high flows,

including floods, usually occur on the Mississippi River and major tribu-

taries in the spring. Small watersheds produce high runoff of short

duration following summer rainstorms. Localized flooding from such rain-

storms may occur at any time of the year.

Figure 8-5 illustrates the relative magnitude of flows occuring in

the Lower Mississippi Region and their major sources.

Ground Water

Aquifers containing fresh ground water underlie the entire region

except for part of the coastal area of Louisiana and a small area in central Generated for member (North Carolina State University) on 2013-03-26 16:07 GMT / http://hdl.handle.net/2027/pur1.32754076370653 Public Domain, Google-digitized / http://www.hathitrust.org/access_use#pd-google 14 | LOWER MISSISSIPPI REGION

Upper Mississippi

44,100 MGD

178,000 MGD \

Arkansas

27,000 MGD

Subregion 801 \

I Subregion 802 \

Red

19,700 MGD

Subregion 803

7 ' 433,000 MGD

Louisiana. About 80 percent of these aquifers are capable of yielding large

volumes of fresh water (Figure 8-6). Highest yields can be obtained from

sand and gravel alluvial and terrace deposits of Quaternary age. Yields

of several thousand gallons of water per minute are not uncommon. Wells

provide much of the public and industrial water supplies in the region

because ground water of good quality is generally available where needed.

- 345,000 MGD

387,000 MGD

Figure 8-5. Streamflow Generated for member (North Carolina State University) on 2013-03-26 16:07 GMT / http://hdl.handle.net/2027/pur1.32754076370653 Public Domain, Google-digitized / http://www.hathitrust.org/access_use#pd-google VOLUME 4 | 15

95°

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U.S. WATER RESOURCES COUNCIL

LOWER MISSISSIPPI REGION -K Ma Prod A ulfers

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Figure 8-6. Major Aquifers Generated for member (North Carolina State University) on 2013-03-26 16:07 GMT / http://hdl.handle.net/2027/pur1.32754076370653 Public Domain, Google-digitized / http://www.hathitrust.org/access_use#pd-google 16 | LOWER MISSISSIPPI REGION

In a few localized areas, ground-water demands have exceeded or are

approaching the economically practicable limit of available supply, but

in most of the region, the water—supply potential is several times larger

than present requirements. The region's average ground-water use is

conservatively estimated at about 4.8 mgd. This estimate is based on

withdrawals consistent with economically and environmentally acceptable

water-level declines.

Water Withdrawals

Total fresh water withdrawn from surface sources and ground water in

1975 averaged about 14 ,567 million gallons per day (mgd) (Figure 8-7) . Water

for irrigation was the largest withdrawal, about 31 percent of the 1975 with-

drawal. Withdrawals for steam electric power generation plants accounted for

another 29 percent of the total, while manufacturing made up 29 percent.

It is expected that the total fresh-water withdrawals will increase about

70 percent to 24,841 mgd by the year 2000 (Figure 8-7) . The largest increase

will be for steam electric power generation, while manufacturing will show a

significant decrease.

Saline (brackish) water withdrawals in 1975 averaged about 1,253 mgd,

only 8 percent of the total water withdrawals. Manufacturing water use

accounts for about one-half of the saline withdrawals, with the remainder

divided about equally between minerals and steam electric. Withdrawals of

brackish water are expected to increase dramatically and by the year 2000

should account for about 30 percent of total withdrawals.

About 20 percent of the 1975 water withdrawals were pumped from wells.

Many cities and towns utilize ground water because of the inferior quality

of available surface water. Industries also used large volumes of ground

water for similar reasons. About one-third of the ground water pumped was

for those two types of users. Water for crop irrigation was obtained in

about equal volumes from surface sources and from wells. About two-thirds

of the ground water pumped was for this use.

Water Consumption

Total consumption of water by the instream uses is estimated to have

been 4,027 mgd in 1975, and is projected to increase to 5,511 mgd by the

year 2000 (Figure 8-7). Irrigation accounted for 3,065 mgd in 1975,

and is projected to increase to 3,272 mgd in 2000. The minerals extraction

industries, primarily petroleum and natural gas, consumed 206 mgd in

1975 and are projected to increase their consumption of water to 416

mgd in 2000. Manufacturing industries consumed 314 mgd but will increase

340 percent to 1,067 mgd in 2000, to become the second largest user

of water.

Domestic water consumption will increase slightly to over 340 mgd

in 2000. Thermal electric power generation is projected to consume 291 mgd

in the year 2000. Low streamflows occur usually during July and August Generated for member (North Carolina State University) on 2013-03-26 16:07 GMT / http://hdl.handle.net/2027/pur1.32754076370653 Public Domain, Google-digitized / http://www.hathitrust.org/access_use#pd-google VOLUME 4 | 11

ANNUAL FRESHWATER WITH DRAWALS

STEAM

ELECTRIC STEAM

ELECTRIC

MANUFACTURING

Tl IIIII IIIIII IIII

DOMESTIC (‘I T

4 /0 I

omen

MANUFACTURING

MINERALS 5% , OTHER MINERALS

5% DOMESTIC 2% 5%

3°/e

1975 2000

Total Withdrawals — 14,567 MGD Total Withdrawals — 24,841 MGD

ANNUAL FRESHWATER CONSUMPTION

MINERALS OTHER °

5% OTHER 3 /

DOMESTIC

,3 /° DOMESTIC I

MANUFACTURING ANUFACTUFHN

Z av. M G stem

ELECTRIC

< *ELECTRlC

1°/0

1975 2000

Total Consumption — 4,027 MGD Total Consumption — 5,511 MGD

Figure 8-7. Withdrawals and Consumption Generated for member (North Carolina State University) on 2013-03-26 16:07 GMT / http://hdl.handle.net/2027/pur1.32754076370653 Public Domain, Google-digitized / http://www.hathitrust.org/access_use#pd-google 18 | LOWER MISSISSIPPI REGION

(months of high consumption), but the depletion of flows due to the above

regional consumptive uses rarely exceeds 10 percent of the present modified

flow.

Instream Uses

Instream flow uses are those needs that are satisfied by flows of water

within the streambed. Instream flow is needed for fish and wildlife,

navigation, recreation, waste disposal, hydroelectric power, and salinity

control. These purposes require minimum levels of water quantity and quality

for satisfactory use. On the main stem Mississippi River, flow quantities

are generally adequate to satisfy the regional requirements. During low-

flow conditions, however, the denser saline waters of the Gulf of Mexico

often intrude into the river channel and advance upstream for many miles,

polluting water supply intakes. It has been determined that a flow of

194,000 mgd is required in the lower reaches of the Mississippi River

to prevent such salt-water intrusion. The instream flow approximation at

the mouth of the river plus the other gulf tributaries is 359,033 mgd.

Maintenance of that flow in the river will not only prevent salt-water

intrusion, but will also provide adequate flow to meet other instream

flow needs such as waste disposal, fish and wildlife habitat, navigation,

and recreation.

Instream flow requirements in the coastal Louisiana marsh and estuary

areas is a very complex matter. Salinity alteration and water level

management needs relate to the requirements for maintaining a water chem-

istry and-or vegetative development conducive to high productivity of

fish and wildlife resources. Flow requirements on the major streams

in the coastal area have been determined in order to provide the optimum

conditions for fish and wildlife productivity. The State-regional estimates

of these flow requirements range from a high of 316,000 mgd in April

to a low of 70,000 mgd in November.

Water Supply and Demand

An abundant supply of generally good quality water is available in

the Lower Mississippi Region. The mighty Mississippi River, carrying

runoff from 41 percent of the conterminous United States, provides water

far in excess of the withdrawal and consumptive requirements of the region.

Total annual withdrawals average about 3 percent of total streamflow in

an average year. Total consumption is only about 28 percent of withdrawals

and less than 1 percent of total streamflow. This is without considera-

tion of the vast ground-water supplies which currently constitute about

33 percent of total withdrawals. Even with a 71 percent increase in fresh-

water withdrawals and a 37 percent increase in consumption projected by

the year 2000, there would appear to be little strain on the region's

water resources in the future.

However, while comparisons of annual supplies with annual requirements

for withdrawal and consumption show no indication of a water shortage, this Generated for member (North Carolina State University) on 2013-03-26 16:07 GMT / http://hdl.handle.net/2027/pur1.32754076370653 Public Domain, Google-digitized / http://www.hathitrust.org/access_use#pd-google VOLUME 4 | 19

can be very misleading. Such a comparison is very complicated because of

various localized and functional requirements and-or demands. The demands

for municipal, industrial, and agricultural water are being easily met,

with a few localized exceptions. The requirements for instream flows,

however, commonly exceed available supplies during low flow periods of

the year. The additional needs for supplemental water for estuarine pro-

ductivity and land building could place a tremendous burden on regional

surface flows in the future if water is withdrawn to satisfy these needs.

Such regional demands, coupled with the prospect of increasing upstream

depletions of surface flows in the future, create the possibility of

serious future conflicts concerning the allocation of regional water

supplies. More detailed discussion of the seasonal, geographical, and

functional problems is presented in the section entitled "Problems."

Comparative Analysis

Table 8-5 compares the National Future (NF) and State-Regional Future

(SRF) estimates of streamflows and water use in the Lower Mississippi Region.

In a few functional-use categories, such as steam electric power

generation and agriculture, there is excellent agreement between NF and

SRF withdrawals and consumptive use figures. The category showing the

largest discrepancy is manufacturing. Since manufacturing is one of the

largest water users in the region, the discrepancy is quite significant.

NF data for manufacturing water use were developed by the U.S. Bureau

of Domestic Commerce (BDC) based on surveys of major manufacturing concerns

throughout the Nation, with survey data checked against aggregated totals

published by the Bureau of the Census of the U.S. Department of Commerce.

SRF data were taken from the Lower Mississippi Region Comprehensive Study,

a recently completed interagency study which based its water-use estimates

on water-use surveys, personnel interviews, and published data. The meth-

odology used by the NF and SRF to develop current manufacturing water

use was very similar. On the other hand, the BDC assumed extremely

high recirculation rates for future years, which accounts for the large

differences between SRF and NF manufacturing use in 1985 and 2000.

Other categories of water use in which significant descrepancies exist

include minerals, domestic, and other functional uses. Differences in

data sources and methodology generally account for the differences in min-

erals and domestic water use. As with manufacturing water use, it was

not possible to resolve these discrepancies. In the category of other

functional uses, the SRF data include a large water usage for fish and

wildlife and commercial fishing. There is a significant documented use

of water in these categories which the NF data do not recognize. Generated for member (North Carolina State University) on 2013-03-26 16:07 GMT / http://hdl.handle.net/2027/pur1.32754076370653 Public Domain, Google-digitized / http://www.hathitrust.org/access_use#pd-google 20 I LOWER MISSISSIPPI REGION

Table 8-5.-—Socioeconomic and volumetric data summary: the Lower Mississippi

Region

1975 1985 I 2000