GEOLOGICAL SURVEY 

CIRCULAR 601-1

Water Facts and

Figures for

Planners and Managers

Water Facts and

Figures for

Planners and Managers

By J. H. Feth

WATER IN THE URBAN ENVIRONMENT

GEOLOGICAL SURVEY CIRCULAR 601-1

Washington 1973
United States Department of the Interior

CECIL D. ANDRUS, Secretary

Geological Survey

H. William Menard, Director

First printing 1973 

Second printing 1973

Third printing 1974 

Fourth printing 1978

Free on application to Branch of Distribution, U.S. Geological Survey 

1200 South Eads Street, Arlington, Ma. 22202
FOREWORD

Urbanization the concentration of people in urban areas and the 

consequent expansion of these areas is a characteristic of our time. It has 

brought with it a host of new or aggravated problems that often make new 

demands on our natural resources and our physical environment. Problems 

involving water as a vital resource and a powerful environmental agent are 

among the most critical. These problems include the maintenance of both 

the quantity and quality of our water supply for consumption, for 

recreation, and general welfare and the alleviation of hazards caused by 

floods, drainage, erosion, and sedimentation.

A prerequisite to anticipating, recognizing, and coping intelligently with 

these problems is an adequate base of information. This series of reports is 

intended to show the relevance of water facts to water problems of urban 

areas and to examine the adequacy of the existing base of water information.

E. L. Hendricks, 

Chief Hydrologist

111

CONTENTS

Foreword _ .

Abstract _ .

Introduction -

How it's presented -

A bit about water -

What is water? .

Where is water? .

Ground water .

Surface water .

To recapitulate .

Conjunctive use .

How much water? .

Domestic demands 

Commercial and industrial use

Patterns of change 

Water-data units and equivalents _-

This metric business _________

Water-quantity data _________

Water-quality units _________

Physical units _____ 

Water temperature ____

Sampling 

Scales 

Specific conductance

Page 

III 

II

1

2

2

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3

4

6

7

8

8

8

10

12

13

13

13

16

16

16

16

18

18

Water-data units and equivalents Continued 

Water-quality units Continued 

Physical units Continued

pH __ -__-_- .---_.

A warning 

pH ranges 

Turbidity . _____

Sediment __.

Powers of ten 

Chemical units - 

ppm versus mg/1 _.

flg/l tO pg/1 

Biological units 

Introduction 

MPN _____________

MPN Index ______.

Colony count method _ 

Caveat emptor 

DO BOD TOC COD? ______

Radiological units 

Water-quality standards and criteria 

Glossary __ 

References _ 

Page 

118 

19 

19 

19 

19 

21 

21

21

22

22

22

22

22

23

23

24

25

26

27

29

ILLUSTRATIONS

Page 

FIGURE 1. Sketches of water as a gas, liquid, and solid_____________-_______________ 12

2. Diagram of water molecule showing one atom of oxygen and two of hydrogen _ ___ 3

3. Sketch of some elements of earth's water cycle _______ __ __ _____ __ 5

4. Sketches showing concepts of surface water-ground-water relations and conjunctive use including artificial recharge ____________________________________________ 9

5. Graphs showing hourly trends in water use on maximum day (July 12) of use in 1954 of public water supply of Kansas City, Mo _________________________________ 11

6. Graph showing range in per capita use of water in 100 largest cities of the United States,

1962 _______________________________________________________ 12

7. Nomograph for converting water-measurement units _ ____ 17

8. Diagram showing pH ranges in relation to use __________ - 20

9. Sketch showing weight-volume equivalents for pure water ____ _____ 23
TABLES

Pace

TABLE 1. Distribution of world's estimated water supply 14

2. Quantity of water used by manufacturers 12

3. Hydrologic effects during a selected sequence of changes in land and water use associated with

urbanization _ 14

4. Round-number conversions, English and metric units 15

5. Miscellaneous equivalents _ 16

6. Temperature conversion _______ 18

7. Powers of 10 ___________________ 21

8. Comparison of chemical constituents in the drinking water standards of the World Health

Organization and the U.S. Public Health Service 27

VI
Water in the Urban Environment

Water Facts and Figures for Planners and Managers

By J. H. Feth

ABSTRACT

Water is defined in terms of its chemical composition and dominant physical properties, such as expansion on freezing and high surface tension. Water on 

the earth is about 97 percent in the seas, 2 percent in 

glacier ice, principally Greenland and Antarctica. Man 

is left with less than 1 percent as liquid fresh water 

to sustain his needs. This is possible under good management because water moves cyclically. Conjunctive 

use of surface and ground water is advocated, as is 

reuse of wastewater. Water needs for domestic and 

light industrial use can be reasonably forecast for 

planning purposes. Heavy-industry needs must be determined on a site-by-site basis.

The units commonly used by hydrologists with respect to quantities and quality of water are denned; 

their significance in water management is outlined, 

and metric-english equivalents are given for many. 

A glossary of terms concludes the report which is intended as a reference work for use by planners and 

managers.

INTRODUCTION

Because water is such an ever-present, pervasive substance in our lives we are constantly 

concerned with it. Any plan for land use requires consideration of water how to get it, 

how to use it, how to dispose of it. Every new 

subdivision must have domestic water and facilities to dispose of wastewater. Every industrial site must have provision for potable water, 

for process or cooling water or both, and for 

disposal of wastes. A city or rural park? We 

need water for visitors to drink, water for 

waste disposal, and often water for a lake or 

pond that will serve the recreational purposes 

for which it is intended. Solid-waste disposal? 

Unless the planning is correct, water seeping 

through the wastes can carry pollutants to

streams, lakes, or bodies of ground water that 

someone else wants to use. The problems are 

inescapable.

Not everyone wants to, or needs to, be an 

expert on water. But especially today when 

environmental concern is great and growing 

the private citizen, the planner, the politician, 

and the manager and decision-maker need to 

know enough to listen and respond with understanding and intelligence to the consultant and 

staffer.

The planner and decision-maker must constantly compromise. The dedicated preservationist may suggest solutions ideal for him; 

the developer may suggest uses and solutions 

ideal for him. The planner and decision-maker 

must weigh these against the feasible, with 

quality of life for everyone in mind, and find 

or devise the land-use compromise, the master 

plan, the grading ordinance, the modified-use 

permit that in his studied judgment provides 

the best land-use pattern.

Water is so all-pervasive that it enters into 

virtually all such decisions one way or another.

This circular is intended to provide the basic 

information that goes into considerations of 

water. It is concerned mostly with the language used in dealing with water. It is long on 

terminology, numbers, and equivalents and 

correspondingly short on theory and principles. 

It is a handbook where one finds the meaning 

of many water terms all packaged together 

with a suggestion of their significance and 

interrelations. Not all terms are easy to understand, even when digested and capsulized as 

well as possible. But water itself is complex in

II
its behavior. I hope the user will find this circular handy at his elbow when he reads a consultant's report, a staffer's briefing or just 

browses in publications concerned with water 

and water problems.

HOW IT'S PRESENTED

The circular is organized into four main 

parts. First there is a section telling a little 

about water and our demands for it not exhaustively, but enough to remind us what water 

is, how it occurs, and how much we need. 

Second is a section on water-quantity terms. 

The third section considers water-quality 

terms the physical, chemical, and biological 

terms most often encountered in discussions of 

water quality as related to use. And finally 

there is a glossary which provides a condensed 

summary of definitions pertaining to the technical terms that are discussed just a bit more 

fully in the other sections of the circular. The 

glossary, then, is the dictionary section. Reference citations appear here and there in the 

text as (Leopold and Langbein, 1960), for 

instance. The full citation will be found at the 

back of this circular in "References."

A BIT ABOUT WATER

WHAT IS WATER? 1

What is water? Water is a common liquid. 

We see it as rain, snow, and fog and in the 

seas, lakes, streams, springs and what comes 

gushing out of the tap when we turn it on.

Water is made up of countless molecules, each 

consisting of two atoms of hydrogen and one 

of oxygen. Hydrogen and oxygen under many 

conditions are gases, but when combined in 

these proportions they form water.

In 1934, Dr. Harold Urey discovered minute 

portions of a third component in water. He 

called the material deuterium, which is a 

heavier isotope of hydrogen. Later another 

hydrogen isotope, tritium, was found to be a 

part of water. Deuterium and tritium are special hydrogen atoms that weigh more because 

they contain extra neutrons.

Water can appear as solid, gas, or liquid 

(fig. 1). In fact, water is the only substance on

1 Condensed and modified from a U.S. Geological Survey pamphlet of the same title, available on request from Information 

Officer, U.S. Geological Survey, Washington, B.C. 20244.

FIGURE 1. Water as a gas, liquid, and solid.

earth that appears in three distinct forms of 

matter within the normal range of climatic 

conditions. The form it takes depends on the 

vigor of motion of its molecules. At low temperature, the molecules are relatively quiet, 

literally because they have less energy. This is 

the condition that produces ice, the solid form 

of water. When frozen, the water molecules 

form in hollow circles, as shown. At moderate 

temperatures, when the molecules are activated 

by the extra heat energy, water is liquid. The 

molecules are close together, yet they slip 

around freely. This is what gives liquid its flowing motion. At high temperatures, the molecules 

move about violently, colliding with one another 

and forming vapor, an invisible gas.

Most substances shrink as they get colder 

until they finally freeze, but water expands 

slightly just before it freezes and during the 

freezing process. Because of this expansion, 

ice is lighter than water, whereas almost all 

other compounds are heavier when frozen. This 

is fortunate, because if ice were heavier than 

liquid water, lakes and streams would freeze 

from the bottom up instead of from the top 

down. They would become solid ice and in cold 

climates the deepest layers might not melt even 

in the summer. Solid freezing would have a 

disastrous effect on fish and water plants, which 

could not live through the winter at all.

Another remarkable fact about water is its 

heat capacity. Heat capacity is the ability of 

a substance to absorb a great deal of heat without itself becoming extremely hot. Water's heat 

capacity is the highest of all substances in 

nature except ammonia. For instance, an empty

12
pan on a gas flame will very quickly become 

red-hot and then burn black. But if some water 

is placed in the pan over the same flame, the 

water will absorb heat from the pan. The pan 

will become hot, but not red-hot, and the temperature of the water will rise only a few 

degrees, comparatively speaking.

The heat capacity of water enables the oceans 

to be huge reservoirs of solar warmth and to 

keep our weather from going to great extremes 

of either heat or cold. The moderating effect of 

water is noticeably lacking in the desert where 

days tend to be very hot and nights chilly to 

downright cold.

Water has an extremely high surface tension. 

Surface tension is the ability of a substance to 

stick to itself. A drop of water falling from a 

spout clings to the tap and stretches very thin 

before finally letting go. Immediately it forms 

a sphere and this sphere resists deformation. 

To split water apart and make it form two new 

surfaces, tremendous force is necessary.

Because of its high surface tension, a water 

surface can support objects heavier than itself a needle, for instance, or insects that 

"skate" around on the water.

But perhaps water's most remarkable property is its action as a solvent. Given enough 

time, water can and does dissolve everything 

exposed to it.

Water is a great mover and doer. It is constantly modifying the landscape, generally very 

slowly, but now and again catastrophically as 

in times of floods and mudslides. Each drop of 

rain is an independent sphere, like a tiny bullet, which can break away minute fragments 

of even the hardest rock provided the rock surface has been weakened by chemical breakdown 

(also engineered by water) of the mineral 

grains of the rock. As they strike the earth 

and become a flowing liquid, the raindrops surround and move fine particles of soil. Water 

carries the soil particles into streams and finally 

down to the flood plains, deltas, and the sea.

All these striking aspects of water depend 

on a process called chemical bonding. All molecules have an electronic cohesiveness tending 

to hold their atoms together. In the case of 

water this force is relatively great and makes 

for an extremely tight structure. This force 

results from the fact that an atom of oxygen

has two unpaired electrons, whereas the two 

hydrogen atoms lack an electron each. The 

hydrogen atom with its single electron is eager 

to obtain another one. The mutual need of the 

atoms for paired electrons draws them irrestably together, and the bond thus formed is 

extraordinarily strong. You can see from the 

diagram (fig. 2) that the hydrogen and oxygen 

atoms share two unpaired electrons.

FIGURE 2. Diagram of water molecule showing one 

atom of oxygen and two of hydrogen.

Strong chemical bonding accounts for water's 

remarkable ability to adhere to substances (or 

"wet" them, as we ordinarily say), and thus 

eventually to dissolve them. Bonding also effects 

the boiling point of water and is responsible 

for its freezing process. The importance of this 

bonding to life processes is great indeed, for 

without it water would not have the unique 

properties already described.

WHERE IS WATER? 2

Most of the world's supply of water the 

estimate is more than 97 percent is in the 

oceans. Most of the rest is locked up in the 

ice caps of Greenland and Antarctica more 

than 2 percent. So man is left with something 

less than 1 percent of the supply to work 

with except insofar as he has begun to tap 

the oceans for industrial cooling water and is 

beginning to desalinize a little ocean water for 

his use. Even so, there seems to be enough 

fresh, liquid water on the earth to supply

2 This discussion is abridged and modified from the U.S. Geological Survey pamphlet "Water of the World" available from the 

Information Officer. U.S. Geological Survey, Washington, D.C. 

20244.

13
present and projected needs far into the next 

century at least, provided we will bear the cost 

of making it clean, keeping it clean, storing and 

transporting it, and increasingly recycling it 

for use more than just one time.

It is rather convenient, and quite accurate, 

to look at the total supply of fresh water on 

the earth as recycled sea water water that has 

evaporated from the surface of the oceans 

leaving the salt behind; water that is in the 

atmosphere and in lakes and rivers; or water 

that is in the soil or deeper in the aquifers 

(water-bearing strata) that underlie the land 

in many places and supply water to wells and 

springs. Wherever it is, and though it may take 

awhile to get there, the fresh water is enroute 

back to the sea again. The cycle is illustrated 

in figure 3.

GROUND WATER

Table 1 shows an estimate by the U.S. Geological Survey of the distribution of the world's 

total supply of water. Notice that of the liquid 

fresh water, an overwhelming proportion is 

ground water that is water in layers of rocks 

beneath the land surface. The deep-lying ground 

water is commonly salty, costly to extract and 

use, and doubtfully renewable in any reasonable 

time span because water underground moves 

slowly at best and to recharge (refill) the deep 

aquifers would take centuries.

Ground water in shallow aquifers ("within 

a depth of half a mile," as shown in table 1) 

is commonly fresh and moves more rapidly than

the deeper ground water. Its movement, however, is general throughout the broad rock formation and not in underground lakes and rivers 

as is sometimes said. In areas of heavy precipitation, shallow ground water is rather rapidly 

recharged, and the ground-water system is 

analogous to a surface reservoir that can be 

drawn upon with assurance that the supply 

will be renewed in a reasonable time when the 

rains come. In semiarid areas, the ground-water 

supply may represent the accumulation of recharge from hundreds or even thousands of 

years. There, the renewal rate is very slow, and 

as far as man's life span is concerned, the 

ground-water supply is a one-time-only source. 

In such areas, when the ground water is depleted, alternative sources of supply must be 

found, usually at great cost.

The quantities of ground water used reach 

sizable proportions, although estimates are inexact because the records are incomplete. But 

the U.S. Geological Survey estimated groundwater use in southern Arizona to be nearly 5 

million acre-feet per year about l 1/^ trillion 

gallons. For the San Joaquin Valley, California, 

the estimate for 1966 was 9 ]/2 million acrefeet nearly twice that in Arizona, and equal to 

about 3 cubic miles of water.

Not all the water stored underground can be 

extracted for use. Earlier, we saw that one of 

its outstanding characteristics is that of wetting surfaces. The same property causes some 

of the water to cling to the surfaces of whatever rock materials it is stored in, and thereTABLE 1. World's estimated water supply

Location

Surface area 

(square miles)

Water volume 

(cubic miles) 1

Percentage of 

total water

Surface water:

Fresh-water lakes _ ____ 

Saline lakes and

inland seas _ _ _ _ _ _ _ 

Average in stream channels __

Subsurface water:

Water in unsaturated zone

(includes soil moisture) _____

Ground water within a 

depth of half a mile _ _ __

Ground water deep lying __

Other water locations :

Icecaps and glaciers _ _______

Atmosphere (at sea level) _____

World ocean _ _____ __ __

Totals (rounded) _________

330,000

270,000

!

f

50,000,000 j

(

6,900,000

_ 197,000,000

139,500,000

30,000

25,000

300

16,000

1,000,000

1,000,000

7,000,000

3,100

317,000,000

326,000,000

0.009

.008

.0001

.005

.31

.31

2.15

.001

97.2

100

1 A cubic mile of water equals 1.1 trillion gallons.

14
' ;':.- ' ' ;V;'y' ' ':'. '. ' ' .-' ' ' '_ ;' '; '.' Water-vapor transport, ocean to 

'. .';' ' ' : .V'- '.' :'.'' :'.':' ':.':': ' ' '. '.'. .' .' .v.'.'v'/Jand and ocean to ocean /.-'.-

Evaporation and

transpiration by plants

FIGURE 3. Sketch of some elements of earth's water cycle.
fore, it cannot be removed completely. Also, as 

ground water moves slowly, a pumping well 

dewaters the aquifer in its vicinity first and 

water from other parts of the aquifer moves 

slowly to refill the dewatered zone around the 

well. Therefore, wells would have to be spaced 

uneconomically close to one another to extract 

in a reasonable time all the water that was not 

clinging to the rock materials.

All the foregoing says that ground water is 

a large and highly valuable resource for man. 

But its modes of occurrence and movement 

must be understood so that the resource can 

be used and managed advantageously. More on 

this subject will be said in the section "Conjunctive Use."

SURFACE WATER

Surface water is what first comes to mind 

when "water supply" is mentioned. It is the 

water we see in ponds, lakes, reservoirs, or 

flowing in streams. It is the water historically 

first used except in those arid areas where 

there are few or no streams and where what 

lakes may exist are brackish or highly saline.

Surface water originates as rain or melting 

snow locally as melting glacier ice. The processes involved, however, are not simple.

Considered as a continuous body of fluid, the 

atmosphere is another kind of ocean. Yet, in 

view of the total amount of precipitation on 

land areas in the course of a year, one of the 

most astonishing world water facts is the very 

small amount of water in the atmosphere at 

any given time. The volume of the lower 7 miles 

of the atmosphere the realm of weather phenomena is roughly four times the volume of 

the world ocean, but the atmosphere contains 

only about 3,100 cubic miles of water, chiefly 

in the form of invisible vapor, some of which 

is transported over land by air currents. If all 

vapor were suddenly precipitated from the air 

onto the earth's surface it would form a layer 

only about 1-inch thick. A heavy rainstorm on 

a given area may remove only a small percentage of the water from the air mass that 

passes over. How, then, can some land areas 

receive, as they do, more than 400 inches 

of precipitation per year? How can several 

inches of rain fall during a single storm in a 

few minutes or hours? The answer is that rainyielding air masses are in motion, and as the 

water-depleted air moves on, new moistureladen air takes its places above the area of 

precipitation.

The basic source of most atmospheric water 

is the ocean, from which it is derived by evaporation. Evaporation, vapor transport, and precipitation constitute a major arc of the hydrologic cycle the continuous movement of water 

from ocean to atmosphere to land and back to 

the se'a. Rivers return water to the sea along 

one chord of the arc. In a subterranean arc of 

the cycle, underground bodies of water discharges some water directly into rivers and 

some directly to the sea.

Estimated average annual evaporation from 

the world ocean is roughly 39 inches. The conterminous 48 United States receive an average of 30 inches of precipitation every year, 

or about 1,430 cubic miles in total volume. 

EVapotranspiration returns approximately 21 

inches of this water to the atmosphere (about 

1,000 cubic miles). Obviously, some rain is 

water that was vaporized from the land areas 

and is being reprecipitated. Evidently the global 

hydrologic cycle, which sends water from sea 

to air to land areas and back to the sea again, 

has short circuits. These are called subcycles.

There are many complexities and variations 

in the fate of water that falls as rain or snow. 

For example, high in the central Rocky Mountains of North America, the Yellowstone River 

heads in Yellowstone National Park just east 

of the Continental Divide. The river water discharges through the Missouri and Mississippi 

Rivers into the Gulf of Mexico about 1,600 airline miles distant from the head.

On the west side of the Continental Divide, 

not far from the Yellowstone, rises the Snake 

River, which flows across Idaho to join the 

Columbia near Pasco, Washington, and its 

waters eventually reach the Pacific Ocean about 

700 airline miles from their source and about 

2,200 miles from the mouth of the Mississippi.

This is a good example of the continuous 

mixing and transfer of water in the hydrologic cycle. An air mass moving eastward across 

the Rocky Mountains contains water evaporated 

from the Pacific Ocean. Some of the water falls 

as rain or snow to the west and some to the 

east of the Continental Divide. Thus, two drops

16
of rain falling almost side by side along the 

continental backbone may end up, one in the 

Pacific, the other in the Atlantic Ocean, although both were derived from the Pacific.

No one known how much water moves from 

the Pacific to the Atlantic Ocean by vapor 

transfer, precipitation, and runoff, but we do 

know a great deal about runoff itself. Estimated total flow into the sea from rivers in 

the 48 conterminous United States takes place 

at the rate of about 1,803,000 cubic feet per 

second (a cubic foot is about 7V& gallons), 

which amounts to approximately 390 cubic 

miles per year.

Crude estimates have indicated that the total 

amount of water that is physically present in 

stream channels throughout the world at a 

given moment is about 300 cubic miles. The 

world's river channels themselves contain on 

the average only enough water to maintain 

their flow for about 2 weeks. Some have much 

more water, others much less, but it seems to be 

a fair average. How, then, do rivers maintain 

a flow throughout the year, even during rainless periods much longer than 2 weeks?

The answer is that during rainless periods 

the flow in streams generally is from ground 

water. Aquifers adjacent to streams will, if 

full, discharge water from underground storage 

and augment or sustain streamflow. However, if water levels in aquifers are lower than 

levels in adjacent streams, water tends to move 

from the streams into the aquifers. Together, 

the streams and aquifers really constitute one, 

interlocking system. At those times when nearly 

all water in a stream is from ground-water 

sources, hydrologists say the stream is at baseflow. Although baseflow period normally represents the lowest period of streamflow, the 

mineral content of the stream water is commonly (but not always) at its highest. Determination of quantities and quality of baseflow 

is, therefore, a necessary step in planning to 

use and manage flow in streams.

The earth's land area's are dotted with hundreds of thousands of lakes. Wisconsin, Minnesota, and Finland contain some tens of thousands each. Some Alaskans claim that their 

State alone has a million lakes. If so, quite a 

few small ponds must be included in the count. 

These lakes, important though they may be

locally, hold only a minor part of the world 

supply of fresh surface water, most of which 

is contained in a relatively few large lakes on 

three continents.

North American lakes are a major element 

in the earth's water balance. The Great Lakes, 

plus other large lakes in North America (chiefly 

in the 48 States and Canada) contain about 

7,800 cubic miles of water 26 percent of all 

liquid fresh surface water in existence.

Similarly, the large lakes of Africa contain 

8,700 cubic miles, or nearly 29 percent of the 

total fresh-water surface supply. Asia's large 

lakes contain about 6,400 cubic miles, or 21 

percent of the total, nearly all of which is in 

Lake Baikal.

Lakes on these three continents account for 

roughly 75 percent of the world's fresh surface 

water. Large lakes on other continents 

Europe, South America, and Australia have 

only about 720 cubic miles, or roughly 2 percent 

of the total. All that remains to fill the hundreds 

of thousands of rivers and lesser lakes that are 

found throughout the world is less than onefourth of the total fresh surface water.

Saline lakes are equivalent in magnitude to 

fresh-water lakes. Their total area is 270,000 

square miles and their total volume is about 

25,000 cubic miles. The distribution, however, 

is quite different. About 19,240 cubic miles (75 

percent of the total saline volume) is in the 

Caspian Sea, and most of the remainder is in 

Asia. North America's shallow Great Salt Lake 

is comparatively insignificant with 7 cubic 

miles.

TO RECAPITULATE

About 97 percent of all water in the world 

is in the oceans. Most of the remainder is frozen 

on Antarctica and Greenland. Thus, man must 

get along with the less than 1 percent of the 

world's water that is directly available for 

fresh-water use. Obviously, he must find much 

more effective ways of management if he is 

to prosper.

Water is a global concern, and the water 

cycle recognizes no national boundaries. Man 

has become so numerous and his activities so 

extensive that he has begun to affect the water 

cycle certainly on a regional scale and very 

likely on a global scale.

17
CONJUNCTIVE USE

Surface water and ground water and precipitation, for that matter are all part of a 

single, closely interrelated resource, fresh 

water. What is damaging to part of the system, 

damages the whole system. The idea behind 

conjunctive use is to manage all components 

of the system, insofar as possible, in such a 

way as to use the whole resource to maximum 

advantage (fig. 4). In times past, the tendency 

has been to develop and use surface water without regard to its interrelation with ground 

water; or to develop a ground-water supply 

without much regard for its relation to surface 

supply in the region. Consideration was rarely 

if ever given to wastewater as part of the total 

supply.

Conjunctive use can be looked at as a carefully planned and managed system of tradeoffs.

For instance, in some areas of the West, precipitation is highly seasonal heavy in winter, 

sparse the rest of the year. We've long ago 

learned to manage part of the system by storing water in surface reservoirs when it was 

abundant, and releasing the stored water during the rest of the year. But we are running 

out of surface-storage sites and still have (1) 

increasing demands for water, and (2) locally 

seasonal surpluses that flow unused to the sea.

In those circumstances, one answer is deliberately to put water in storage underground 

through the process of artificial recharge. In 

some places, surplus water is put underground 

through recharge wells. In parts of Long Island, 

N.Y., and southern California, treated wastewater is put down recharge wells to build a 

water barrier against sea-water intrusion of 

used aquifers. Elsewhere, seasonally surplus 

surface water is recharged through spreading 

grounds or ponds underlain by sand and gravel 

that allow the water applied to infiltrate readily 

and to percolate rapidly downward and become 

recharge to ground water.

Such programs of water management have 

several aims protection of aquifers as mentioned, stopping land subsidence, and storing 

water in aquifers where it is virtually free from 

loss by evaporation. The processes of artificial 

recharge are basically simple, but management 

is often complicated by complex aquifers 

geology, siltation of the spreading surfaces,

clogging of wells, and, in some places, the incompatible quality of the recharge water with 

respect to water already in subsurface storage 

or to the mineralogy of aquifer materials.

In ideal situations, conjunctive use may involve putting seasonally surplus water underground and using surface supplies, then as 

surface water becomes scarce, using water from 

wells. This is the simplest and most direct 

trade off. Again, conjunctive use is a management concept and process, designed to use to 

optimal advantage both surface and subsurface 

components of the water resource. In a few 

places, and somewhat sporadically so far, attempts have been made, and continue, to modify 

the timing and quantities of precipitation by 

cloud seeding.

HOW MUCH WATER?

Good, hard facts with wide transfer value 

are hard to come by for per capita, or other 

unit, use of water. This dilemma stems from 

variations in demand imposed by variations in 

climate, income, tradition, and industrial processes. There may be other factors as well.

It is widely recognized that patterns of industrial water demand are changing as it becomes more economical to recycle and reuse 

process water than to use and discharge water 

on a once-through basis. The change reflects 

both the increasing cost of supplying new 

process water and the rapidly growing demand 

that industry clean up its wastewater before 

discharging it.

The following survey is not intended to be 

exhaustive. The use data cited have been 

gleaned from a variety of available sources and 

represent a state-of-the-art evaluation.

DOMESTIC DEMANDS

Strictly in-home use tends to be fairly modest, ranging from perhaps 10 gpcd (gallons 

per capita per day) to 80 gpcd. The low values 

are found in home not served by electricity. 

Higher values appear to be representative of 

rural, suburban, and urban use in homes that 

are served by electricity. Suburban use may be 

larger than urban if water for yard irrigation 

is included (Leopold and Langbein, 1960). A

18
Nonaquifer

Water-saturated but impermeable 

(nonaquifer)

Gaining stream Losing stream

Some streams alternately gain and lose in different parts of their courses. Similarly some streams gain in the rainy 

season when the water table is high and lose in the dry season when the water table is low.

Well pumped when 

streamflow is deficient

 "/: ; ;':! ;:::V.-VX-'Water table'. 

vV-': Aquifer V ':' : .'. ' .'-V '.'-.': '.'.'.

Artificial recharge using spreading ponds when streamflow exceeds current needs

Artificial recharge using injection wells

FIGURE 4. Concepts of surface water-ground water relations and conjunctive use including artificial recharge.

19
few specific use factors cited by those authors 

(p. 32) are as follows:

Use

Flush a toilet ________6 gallons (revised est. 1973 

Tub bath ___________30-40 gallons 

Shower bath ___________.20-30 gallons

Wash dishes _ 10 gallons 

Run washing machine __.._ 20-30 gallons

Wastes 

Dripping faucet __ _ One drop per second=

4 gallons per day 

"Humming" toilet leak _ 1% gallons per hour=

13,000 gallons per year 

Water the yard 

Humid areas 6 inches per year

8,000 sq ft= 30,000 gallons per year 

Semiarid areas 20 inches per year

8,000 sq ft= 100,000 gallons per year 

Desert areas 36 inches per year 

8,000 sq ft= 180,000 gallons per year

Peak-use rates diverge markedly from the average rate, and need to be accommodated in design of municipal water systems. Leopold and 

Langbein (1960, p. 33) sketched the pattern 

as follows:

Water use varies during the day and during the 

week in a way to reflect most interesting details of 

American home life. Use is, of course, low during the 

night but increases rapidly to a maximum between 8 

and 9 o'clock in the morning. Another peak use occurs 

at suppertime between 6 and 8 o'clock in the evening. 

Though there is variation in maximum peak between 

cities, this difference is interpreted to mean that more 

people take baths in the morning than at bedtime. Also, 

an extra heavy peak occurs on Saturday night in 

many cities; so it appears that the Saturday night 

bath is still a reality.

A more graphic indication of variation in 

load is shown in the accompanying graphs (fig. 

5) compiled by M. P. Hatcher and cited by 

Savini and Kammerer (1961, p. A-13).

COMMERCIAL AND INDUSTRIAL USE

The graphs (fig. 5), of course, introduce the 

commercial and industrial demands that may 

be imposed on municipal water systems. At this 

stage of the game, a separation needs to be 

made of those industries that draw fairly 

modest quantities of water from municipal 

systems and industries whose needs for water 

are so large that it is economical for them to 

develop their own supplies. That distinction 

should be kept in mind and thoroughly ironed 

out between planners and industrialists anytime a new industry seeks to move into a site 

within a land-use planner's purview. The

intricate physical, economic, and legal problems involved in such decisions go far beyond 

the scope of this discussion.

In 1960, average use by commerce and industry in the United States was about 70 gpcd. 

Public use on top of that, use for firefighting, 

street cleaning, public-building use, and maintenance of public parks was some 10 gpcd. And 

leaks from water mains, unmeasured leaks from 

faucets, and errors in measurement account for 

an additional and seemingly almost irreducible 20 percent of the total municipal supply. 

In sum, the average per capita use of water in 

American cities was about 150 gpcd (Leopold 

and Langbein, 1960, p. 33). In 1970, per capita 

use from public water supplies was about 180 

gpd (Murray and Reeves, 1972, fig. 8). Total 

use including water withdrawn for irrigation 

and industry was about 1,800 gpcd. McKinney 

(1962, p. 167) confirmed these general values in 

his estimates of sewage discharge as follows:

50 gpcd domestic sewage, purely residential

area. 

75 gpcd as above, but heavy concentration of

electrical appliances. 

100 gpcd residential community with business and

light industry.

Special problems in planning for commercial 

use in the growing numbers of places in the 

country that depend on special-interest uses 

and tourism, are indicated by the following 

paragraph from Flack (1971, p. 757).

A special word may be in order with respect to seasonally occupied areas. The unsteady loading of water 

systems in tourist oriented locations creates severe 

problems in terms of water supply and in terms of 

waste water disposal. High impact loading in winter 

in the ski areas and in the summer season in mountain and seaside resort areas can create extreme supply and treatment problems. Populations that increase 

from several hundred to the thousands and ten thousands for a short season can wreak havoc on a water 

and wastewater system. This area of specialized water 

use requires specialized water design and probably 

different sorts of criteria for design than are customarily used. A different kind of design criteria is needed 

for a community that goes most of the year with a 

couple of hundred people and suddenly jumps to several 

thousand, than for a similar city that has a stable 

population all year around.

Light industrial use of water is accommodated in previous paragraphs use such as 

might typically come from municipal supplies. 

Heavy industry is another story, and a few 

facts may demonstrate the magnitude of its

110
CO

Z 

O

80

O

rr 60

« 

LL 

O

CO 

Z 

2 20

UJ 0 

CO

^ 30

LL 

O

UJ 20

r-

^ 10

Lawn sprinkling

O

QC 

UJ 

OL

CO

Z 

O

60

40

20

LL 

O 

CO

1 " 

d ="

Z 40

Commercial and industrial 

(Exclusive of air conditioning)

I 

Household

CO

D

u. 

O

< 

cc

30

20

10

Air conditioning

12PM 6AM 12AM 6PM 12PM 12PM 6AM 12AM 6PM 12PM

FIGURE 5. Hourly trends in water use on maximum day (July 12) of use in 1954 of public water 

supply of Kansas City, Mo. Based on data prepared by M. P. Hatcher for 1955 conference of 

American Water Works Association (from Savini and Kammerer, 1961, p. A13).

needs. Ninety-four percent of water used by 

industry is used for cooling, and most of this 

can be used again. But repeated reuse for cooling may have drastic effects on receiving 

streams, as is shown by the example of the 

Mahoning River, Ohio. Several steel mills use. 

the Mahoning, and in July 1941 a stream-water 

temperature of 117°F (47°C) was measured. 

Even in winter, a temperature of 84°F (29°C) 

was recorded. The importance of water temperature is discussed in the section of this 

report on physical quality of water.

The electric-power industry presently uses 

by far the largest amount of cooling water in 

its fuel-powered generators. (The large use of 

water in hydroelectric turbine generation is 

disregarded as that is flow-through use and 

has no, or negligible, effect on water quality 

for reuse.) The chemical industry is second but 

uses only about one-tenth as much water as 

does power-generation cooling.

Some of the major industrial uses of water 

are shown in (table 2). Note that the use 

ranges from 79 gped (gallons per employee per 

day) for furniture and fixtures to 25,157 gped 

for petroleum and coal products and that from 

67 to 95 percent of the intake water reappears 

in the wastewater stream (right-hand column, 

table 2).

Geographic distribution seems to offer no 

valid clues as to per capita use of water. The 

results of a survey (Durfdr and Becker, 1964, 

p. 74-77) are shown graphically (fig. 6). The 

per capita use ranges from 65 to 370 gpd, 

Spokane, Wash., having the highest and Fresno, 

Calif., the next highest. About 100 miles north 

of Fresno, but under almost identical climatic 

conditions, Sacramento, Calif., showed about 

100 gped less use than Fresno. Seattle, Wash., 

showed a use of 140 gped, and neighboring 

Tacoma 290 gped. Chicago reported use of 

230 gped and adjacent Gary, Ind., only 100

111
TABLE 2. Quantity of water used by manufacturers

[Data gathered for manufacturing establishments with 6 or more employees. Adapted from Reid, 1971,

p. 250-051]

Industry Group

Processing Industries: 

SIC 

20 Food and kindred products 

24 Lumber and wood products 

26 Paper and allied products 

28 Chemicals and allied products __ 

29 Petroleum and coal products 

30 Rubber and plastic products 

32 Stone, clay, and glass products __ 

33 Primary metal industries 

Weighted average _ 

Fabricating Industries: 

SIC 

21 Tobacco products ___ __ 

22 Textile mill products _ __ 

25 Furniture and fixtures _ 

31 Leather and leather products 

34 Fabricated metal industries _ 

35 Machinery, except electrical 

36 Electrical machinery _ _ _ 

37 Transportation equipment 

38 Instruments and related products 

39 Miscellaneous manufacturing _

Weighted average 

Number 

of 

employees

1,589,380 

489,354 

583,234

734,261 

152,470 

406,777 

550,451 

1,122,911

76,989

854,543

360,882

322,747 

1,058,954 

1,424,432 

1,502,324

1,593,285

301,650 

371,858

Annual water 

intake 

(billions 

of gal)

812 

161 

2,078

3,899 

1,400 

168 

264 

4,587

4

158

8

20 

76 

172 

114

252

31 

19

Gallons per 

employee 

per day 

( thousands )

1.400 

1.146 

9.762

14.584 

25.157 

1.439 

1.434 

11.196

6.507

.168

.644

.079

.215 

.249 

.421 

.264

.551

.363 

.175

.378

Intake 

 wteter 

appearing as 

wastewater 

(percent)

91 

82 

94

94 

94 

95 

88 

94

67

91

94

94 

93 

95

87

95

90 

93

15-

10-

5-

0-

i

X

X

X

X

X

X

X

X

X

X

X X

X XX XXX

X

X

X

X

X

X

X

x

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

X

x

X

X

X

X

X

X

X

X

X

X

X

1

X

X

X

X

X

X

X

X

X

X

X

x

X

X

X

X

X

X

x

X X

X X

XXX

XXX

-1 1 1 _________ 1 _________

Public water supplies, 100 largest U.S. cities

x

x x x x

xxxxxx x x xx

UJ

O

CC 

UJ

m

50 100 150 200 250 300 350 400

GALLONS PER CAPITA PER DAY 

FIGURE 6. Range in per capita use of water in 100 largest cities of the United States, 1962.

gpcd. Although the graph shows a strong 

enough central tendency, there is broad spread 

in the data. The only apparent explanation is 

that municipal systems that show high per 

capita use values are tapped to a considerable 

degree by industry. The lower use values 

including Gary, for instance seem to imply 

that industrial water is self-supplied.

The foregoing data, sketchy as they are, indicate the general magnitude of domestic and 

commercial water-supply needs. The load on 

municipal water-supply and sewage-disposal

systems imposed by industry is highly variable 

and not amenable to averaging. The planner 

thus must plan on a site-by-site basis in terms 

of the foreseeable types of industry involved, 

their size, and their impact on supply and disposal facilities. No easy job. But there are no 

shortcuts in sight.

PATTERNS OF CHANGE

For all the variations in detail with location, 

climate, land forms, natural resources, and

112
natural hazards, there is a general pattern that 

relates urbanization and its parallel changes in 

land and water use, to the hydrologic systems 

that operate in any given region. Before considering water units, their significance, and 

the wonderously varied terms in which they 

are expressed, it is well to bear the overall 

pattern in mind. Savini and Kammerer (1961, 

p. A6-A7) tabulated the hydrologic effects of 

progressive urbanization (table 3), and defined 

several stages in the process.

In the early-urban stage, city-type homes are 

built on large plots and are interspersed here 

and there with schools, churches, or shopping 

centers. Water supply is usually obtained by 

pumping from individual wells, the rubbish is 

burned, the garbage buried, and sewage is disposed of in septic tanks or cesspools. The 

middle-urban stage is characterized by largescale housing developments, more schools and 

shopping centers, some industrial buildings, 

and enlarged networks of streets and sidewalks. 

Municipal systems to supply water of acceptable 

purity and sewers to dispose of sewage may be 

built. However, some domestic sewage may still 

be discharged to septic tanks and subsurface 

disposal systems. Domestic food wastes may be 

collected by truck or discharged through 

kitchen-disposal units to septic tanks or sewer 

systems. The late or advanced, urban stage is 

characterized by a large number of homes, 

apartments, commercial and industrial buildings, and streets and parking lots. A large part 

of the area is roofed or paved. Sanitary sewers 

and large, but frequently inadequate, storm 

sewers remove human and industrial wastes 

and provide drainage. The smallest streams are 

eliminated entirely and the slightly larger 

streams are confined to artificial channels and 

canals and may be obstructed by bridge piers. 

Buildings and other structures encroach upon 

the natural stream floodway and even into the 

channel. The hydrologic and hydraulic effects 

of these changes are quite severe.

We have now looked at what water is, how 

and where it occurs, how much is needed, and 

man's impact on water. Now let's go on to 

consider the language used by hydrologists, 

engineers, and chemists when they discuss 

quantity and quality of water.

WATER-DATA UNITS AND EQUIVALENTS

Those who use, distribute, analyze, and 

evaluate water speak in many tongues. There 

are cfs (cubic feet per second), mVsec (cubic 

meters per second), mgd (million gallons per 

day), miners' inches, and acre-feet.

In water-quality terms, there are such units 

as ppm (parts per million), mg/1 (milligrams 

per liter), and MPN (most probable number) 

not to mention picocuries per liter, grains per 

gallon, and degrees Fahrenheit or Celsius. 

Confusing? Of course!

The purpose of this section is to introduce 

and define many of the diverse units of measurement of quantity and quality of water that 

are'used. Where appropriate, a little bit is said 

about the interpretation and significance of 

data reported in the several units. And an attempt is made to show how the units 'relate 

one to another. This section is to be browsed 

in, or more often, consulted as a capsule reference when an unfamiliar term crops up.

The sources of information are given in 

parentheses. They provide much more authoritative information on the subjects than is given 

in this section.

THIS METRIC BUSINESS 

One symptom of the increasing use in the 

United States of the nearly worldwide metric 

system is the increasing frequency with which 

chemical quality of water is discussed in terms 

of milligram per liter, rather than in parts per 

million, the units that used to prevail. Another 

sign is the growing use of degrees Celsius 

(centigrade) along with, or in place of, degrees 

Fahrenheit. These matters are discussed in a 

later section on chemical-quality units.

We have yet to "go metric" in this country 

in terms of volume units. Meanwhile, the scientific and planning literature from overseas 

and from Central and South America commonly 

uses metric units. So, in the section on quantity, some equivalents that may be useful are 

included.

WATER-QUANTITY DATA

How much water is there? How good is it?

These are the questions that must be answered in evaluating the suitability of a water 

supply for any planned use. This section deals

113
TABLE 3. Hydrologic effects during a selected sequence of changes in land and water use associated with

urbanization

Change in land or water use Possible hydrologic effect

Transition from preurban to early-urban stage:

Removal of trees or vegetation, Construction of 

scattered city-type houses and limited water 

and sewage facilities.

Drilling of wells _ _ _______________

Construction of septic tanks and sanitary drains _

Transition from early-urban to middle-urban stage:

Bulldozing of land for mass housing; some topsoil 

removal; farm ponds filled in.

Mass construction of houses; paving of streets; 

building of culverts.

Discontinued use and abandonment of some shallow 

wells.

Diversion of nearby streams for public water 

supply.

Untreated or inadequately treated sewage discharged into streams or disposal wells.

Transition from middle- to late-urban stage:

Urbanization of area completed by addition of 

more houses and streets, and of public, commercial, and industrial buildings.

Larger quantities of untreated waste discharged 

into local streams.

Abandonment of remaining shallow wells because 

of pollution.

Increase in population requires establishment of 

new water-supply and distribution systems, construction of distant reservoirs diverting water 

from upstream sources within or outside basin.

Channels of streams restricted at least in part to 

artificial channels and tunnels.

Construction of sanitary drainage system and 

treatment plant for sewage.

Improvement of storm drainage system ___,_ 

Drilling of deeper, large-capacity industrial wellsIncreased use of water for air conditioning

Drilling of recharge wells ________.

Wastewater reclamation and utilization

Decrease in transpiration and increase in storm flow. 

Increased sedimentation of streams.

Some lowering of water .table.

Some increase in soil moisture and perhaps a rise in 

water table. Perhaps some waterlogging of land 

and contamination of nearby wells or streams from 

overloaded sanitary drain system.

Accelerated land erosion and stream sedimentation 

and aggradation. Increased flood flows. Elimination 

of smallest streams.

Decreased infiltration, resulting in increased flood 

flows and lowered ground-water levels. Occasional 

flooding at channel constrictions (culverts) on remaining small streams. Occasional over-topping or 

undermining of banks of artificial channels on small 

streams.

Rise in water table.

Decrease in runoff between points of diversion and 

disposal.

Pollution of streams or wells. Death of fish and 

other aquatic life. Inferior quality of water available for supply and recreation at downstream 

populated areas.

Reduced infiltration and lowered water table. Streets 

and gutters act as storm drains creating higher 

flood peaks and lower base flow of local streams.

Increased pollution of streams and concurrent increased loss of aquatic life. Additional degradation 

of water available to downstream users.

Rise in water table.

Increase in local streamflow if supply is from outside 

basin.

Increased flood damage (higher stage for a given 

flow). Changes in channel geometry and sediment 

load. Aggradation.

Removal of additional water from area, further reducing infiltration recharge of aquifer.

Lowered water-pressure surface of artesian aquifer; 

perhaps some local overdrafts and land subsidence. 

Overdraft of aquifer may result in salt-water encroachment in coastal areas and in pollution or contamination by inferior or brackish waters.

Overloading of sewers and other drainage facilities. 

Possibly some recharge to water table, owing to 

leakage of disposal lines.

Raising of water-pressure surface.

Recharge to ground-water aquifers. More efficient use 

of water resources.

114
with the first question; a following section 

deals with the second.

In talking about "how much" we must first 

look at the complex of units used in defining 

"how much." For starters, let's browse a little.

One gallon per minute doesn't sound like a 

lot. But that much flow from a spring or well 

provides 1,440 gpd (gallons per day) enough 

for a family of five with lawn watering thrown 

in, or for 10-15 people otherwise. At least 100 

people could survive awhile on that amount, 

provided the water is all caught and stored for 

use as needed.

We have just used two quantitative terms, 

gallons per minute and gallons per day. Let's 

look at these and other terms in common use, 

and compare one with another, starting with 

the exotic.

Back when the West was young, and in places 

where gold could be had for the taking, hydraulic miners established their water rights 

in terms of the miner's inch. The miner's inch 

is defined as the quantity of water that will 

flow through an orifice 1 inch square under a 

stated pressure head that ranges from 4 to 6*/2 

inches in different places. The variance led, 

naturally, to confusion. So the value of the 

miner's inch has been set by statute in most 

of the Western States as follows:

50 miner's inches=1 cfs (cubic foot per second) 

in Idaho, Kansas, Nebraska, New Mexico, North 

Dakota, South Dakota, 

Utah, Washington, and 

northern California.

40 miner's inches=l cfs in Arizona, Montana,

Oregon, and southern California. 

38.4 miner's inches=l cfs in Colorado.

Clearly, the miner's inch is an unhandy unit 

of measure and is nearly obsolete. It is of historic interest and is the basis of various water 

rights still in existence in the West.

In irrigation practice, the acre-foot is a 

common unit of volume. It is the quantity of 

water that will cover 1 acre to a depth of 1 

foot and is equal to 43,560 cubic feet or nearly 

326,000 gallons. An acre-foot equals about 

1,230 m3 (cubic meters) and 3.07 acre-feet 

make up 1 million gallons.

Flow rates in public water-supply systems 

are commonly reported in gallons per minute 

(gpm) or millions of gallons per day (mgd). 

Flow rates in rivers are commonly stated in 

second-feet (=cfs=cubic feet per second; the 

British call this unit the "cusec"). Flow at the 

rate of 1 cfs=449 gpm=0.645 mgd. Also, 1 

cfs=28.3 1/s (liters per second)-=0.0283 ma /s 

(cubic meters per second).

Precipitation, whether as rain or as snow, is 

generally reported in this country in inches of 

depth per year. Precipitation intensity may be 

expressed as inches per hour. Elsewhere, the 

common measure of precipitation is the millimeter (mm=thousandth of a meter). There are 

25.4 mm per inch.

Some of the equivalent units are shown in 

the following nomograph (fig. 7) and tables 4 

and 5.

TABLE 4. Round-number conversions, English and metric units

[Prepared by H. E. Thomas]

Length

Meter _ _______

Kilometer _ _ _

Foot _________

Mile ______ .

Symbol

. mm

 m

 in

______ ft

mm

I

1,000

25.4

305.8

m 

0.001 1

1,000

.0254

 me

1,610

km

0.001 1

1.61

in 

0.039

39.4

39,400

1

12

63,360

ft 

0.003

3.28

3,280

.083

1

5,280

mi

0.621

1

Area

£

Square meter ___ .

Hectare _____ _ __ _

Square kilometer _ 

Square foot _____

Acre __ _ _ _ __,__

Square mile _______

Symbol 

. W3

. ha km2 

. ft2

miB

m*

1

10,000

1,000,000 

.093

4,050

2.590.000

ha

1

100

.405

259

km*

1

2.59

/«*

10.76

107,600

10,760,000

1

43,560

acre 

0.000247

2.47

247

1

640

mi*

0.00386

.386

.00156

1

115
TABLE 4. Round-number conversion, English and 

metric units Continued

Volume

1 km3 (cubic kilometer) =811,000 acre-ft

(acre-feet) 

= 1,000,000,000 ms

(cubic meters) 

1 m" (cubic meter) =35.3 ft3 (cubic

feet)

=264. U.S. gallons 

= 1,000 1 (liters) 

1 1 (liter) =0.0353 ft3 (cubic

foot)

=0.264 U.S. gallon

1 mg (million U.S. gallons) =3.07 acre-ft

(acre-feet) 

1 acre-ft (acre-foot) =1,233 m" (cubic

meters) 

=43,560 ft3 (cubic

feet) 

=325,900 U.S.

gallons 

1 ft3 (cubic foot) =0.0283 ms (cubic

meters)

= 7.48 U.S. gallons 

=28.3 1 (liters) 

1 gal (U.S.) =0.134 ft8 (cubic

foot) 

= 3.78 1 (liters)

Flow Rate

1 kmVyr (cubic kilometer/year) =811,000 acre-ft/yr

(acre-feet/year) 

=723 mgd (million

U.S. gallons/day) 

=31.7 mVs (cubic

meters/second) 

1 mgd (million U.S. gallons/day) =694 gpm (U.S.

gallons/minute) 

= 1.55 cfs (cubic

feet/second) 

=0.044 mVs (cubic

meter/second) 

1 gpm (U.S. gallon/minute) =0.063 1/s (liter

per second) 

1 mVs (cubic meter/second) =22.8 mgd (million

U.S. gallons/day) 

= 15,800 gpm (U.S.

gallons/minute) 

=35.3 cfs (cubic

feet/second) 

= 1,000 1/s (liters/

second)

1 cfs (cubic foot/second) =0.645 mgd (million U.S. gallons/

day) 

=449. gpm (U.S.

gallons/minute) 

=0.0283 mVs (cubic

meter/second) 

=28.3 1/s (liters/

second)

1 1/s (liter/second) =15.8 gpm (U.S. 

gallons/minute) 

=0.0353 cfs (cubic 

feet/second)

TABLE 5. Miscellaneous equivalents

[Prepared by H. E. Thomas]____________

1 inch of rain yields about 27,200 gallons per acre.

1 inch of rain yields about 100 tons per acre.

1 gallon of water weighs 8.34 pounds.

1 cubic foot of water weighs 62.43 pounds.

1 liter is nearly equivalent to 1% pints or Vs gallon.

1 imperial gallon (in the United Kingdom and Canada,

for instance) =nearly 1 Vs U.S. gallon. 

1 million gallons per day=1.547 cubic feet per second. 

1 cubic mile=3,379,200 acre-feet=lX1012 (1 followed

by 12 zeros) gallons. 

1 cubic foot per second=1.98 (nearly 2) acre-feet per

day.

WATER-QUALITY UNITS

What with chemical quality, biological quality, physical quality, radiological quality, there 

is a plethora of units used to discuss water 

quality. Atop all that, there are some units 

fading from use (grains per gallon), and a 

transition well along toward the use of metric 

units.

In this section we'll try to (1) make units 

useful by pointing out their origins and limitations, and (2) give indications of how units in 

one system relate to those in another system or 

to show that conversion from one system to 

another cannot be made. The discussion takes 

up the more common physical, chemical, biological, and radiological units.

PHYSICAL UNITS 

WATER TEMPERATURE

Water temperature is of concern to just about 

everyone from the industrialist seeking cooling 

water, through the swimmer or fisherman (one 

likes it warm, one likes it cold), to the commercial ice manufacturer or the bon vivant, for 

despite folk tales to the contrary, block ice and 

ice cubes freeze faster from cold water than 

from warm. Temperature exercises major control over solubility of oxygen in water, so sanitarians are concerned. And, by now, we are all 

concerned with "thermal pollution," or "thermal enrichment," depending on local circumstances and personal point if view. Measurement of water temperature at one point in a 

water body and one moment in time is easy 

just dunk in a thermometer or thermistor and 

read it off.

SAMPLING

However, planners and managers should always keep in mind the fact that a single read116
1200-

1100-

600-

550-

500-

450-

400-

350-

300-

250-

200-

.55-

.50-

.45-

.40

.35

.30-

3.5

2.5-

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0 1.9- 

O

CO

1.7

ec.

IK 1.6-

0.

1.5

IM 1.4

UJ

u.

1.3

O

1.2

CD 

O 

O 1.1

.45

3000

2500

1100

750

700-

550

500

450

400

350

FIGURE 7. Nomograph for converting water-measurement units (by William Back).

117
ing is not a sound basis for planning or decision. Water-temperature measurements, like all 

water-quality determinations, are samples that 

may or may not represent conditions in the 

whole water body. More likely there are variations with depth and laterally across and 

throughout the stream or lake. And there are 

changes with time hourly often, seasonally 

for sure. Hardware is now available to monitor 

water temperature and other properties either 

continuously or at selected time intervals. If 

the relations between temperature at the sampling point and throughout the water body of 

interest are known, such continuous records 

can be used to great advantage in water management.

SCALES

The water cooler in an office puts out water 

at 8°C sounds tooth-chilling, doesn't it? But 

46°F, which it is, is just nice, cool, and refreshing. Lake trout spawn in water at comparable temperatures; salmon and stream trout 

in water a bit warmer but not higher than 

13°C; but largemouth bass, bluegill, and the 

like, spawn when water temperatures approach 

32°C, which is 90°F.

What are °C? They make up the metric temperature scale, of course, in which 0° is the 

freezing point of water and 100° (at sea level) 

the boiling temperature. Long called "centigrade," because of the 100-degree span from 

freezing to boiling, the scale now is frequently 

called the Celsius scale, after Anders Celsius, 

an 18th century Swedish astronomer who devised it. Like other metric measures, the Celsius 

scale is being used more and more in this 

country. Table 6 gives the temperature equivalents for the Fahrenheit and Celsius scales for 

the normal range of natural water temperatures.

SPECIFIC CONDUCTANCE

A common way to express general mineral 

content of water is by its specific electrical 

conductance that is, its capacity to conduct 

an electric current. Truly pure water has almost 

no such capacity. Dissolved substances that 

ionize (form electrically charged particles) in 

water increase its capacity to conduct a current. So as dissolved-solids concentrations increase, the specific conductance (sometimes 

called electrical conductivity) also increases.

TABLE 6. Temperature conversion

[To nearest °C]

op

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

50

51

52

53

54

«C

0

1

1

2

2

3

3

4

4

5

 6

6

7

7

8

8

9

9

10

11

11

12

12

op

55

56

57

5£

59

60

61

62

63

64

65

66

67

68

69

70

71

72

73

74

75

76

77

«C

13

13

14

14

15

16

16

17

17

18

18

19

19

20

21

21

22

22

23

23

24

24

25

op

78

79

80

81

82

83

84

85

86

87

88

89

90

91

92

93

94

95

96

9.7

98

99

100

°C

26

26

27

27

28

28

29

29

30

31

31

32

32

33

33

34

34

35

36

36

37

37

38

op

101

102

103

104

105

106

107

108

109

110

111

112

113

114

115

116

117

118

119

120

121

122

°C

38

39

39

40

41

41

42

42

43

43

44

44

45

46

46

47

47

48

48

49

49

60

The ratio DSrSp.cond. (dissolved solids to specific conductance) varies a bit but is generally 

in the range 0.6 to 0.7 dissolved-solids concentration (in mg/1) is six-tenths to seventenths the value of specific conductance (in 

micromhos) determined in a standard conductance cell. So, specific conductance of 1,000 

suggests dissolved-solids concentration of GOO700 mg/1; 400 sp.cond. suggests 240-280 mg/1, 

and so on.

Conductance is the reciprocal of resistance 

so conductance is reported in reciprocal ohms, 

called mhos. Natural waters have specific conductance so much less than 1 mho that they are 

reported in micromhos, the observed value in 

mhos multiplied by one million.

For more detail on these subjects, see Hem 

(1970, p. 96-103).

pn

The pH of a solution (such as water) is defined as the negative logarithm, to the base 10, 

of the hydrogen-ion activity. That's a fact that 

you can file and forget. But what pH can tell 

about the usefulness of water is critically important to the user and manager of water.

The pH scale runs from 0-14. And pH is 

generally determined with a meter hooked up 

to two electrodes that are immersed in the 

water being tested. On the scale, 7.0 is neutral 

and is the pH of pure water. A pH less than 7 

indicates an acidic-solution, and a pH greater 

than 7 a basic solution.

118
The pH scale and some of its areas of significance are illustrated in figure 8. The pH 

scale is logarithmic that is, each unit change 

in pH represents a 10-fold change in hydrogenion concentration.

Partly because the pH is sensitive to many 

environmental influences, this property of 

water is a very useful index to the balance of 

chemical forces in the water in its natural state. 

The reactions of water with various substances, 

as a function of pH, depend on the thermodynamic properties of those substances. Though 

the reactions indicated toward the upper and 

lower limits of the pH scale may appear anomalous, they can be explained in chemico-physical 

terms, although not simply.

A WARNING

Although pH can be, and often is, precisely 

determined to two decimal places, many 

probably most reported pH values should not 

be taken exactly at face value. This is because 

the pH of a solution changes, sometimes drastically and very rapidly with exposure to air, 

with changes in temperature, with biological 

activity in the sample bottle, and in response to 

many other influences. Therefore, a pH determination made in the laboratory may not represent very well the pH of water in a river or 

lake, underground in an aquifer that supplies 

water to a well, or in a municipal waterdistribution system for that matter. Where pH 

cannot be measured in place, it should be determined in the field just as soon as the water 

sample is taken. If a water supply is corrosive, 

but the lab reports show normal pH values, a 

field pH check may help to locate the trouble.

pH RANGES

Figure 8 shows that unpolluted natural 

waters tend to have a narrow pH range not 

far from neutrality. Narrow ranges, near neutrality, are the rule for most beneficial uses of 

water. The range in water used for public 

supply is surprisingly wide, a testament again 

to man's great adaptability he can tolerate a 

wider pH range than most fish, for instance. 

Perhaps recognizing that, the U.S. Public 

Health Service (1962) did not set pH limits 

in its drinking-water standards.

The vast pH range of untreated wastewaters 

illustrates their potential impact on receiving

waters. In addition to high organic loads, 

toxicity, content of heavy metals, and other 

characteristics that may be present, the extremes in pH of some wastewaters impose 

damaging conditions on sewage-treatment 

plants. The microorganisms die off or become 

ineffective in sewage treatment when pH becomes either too high or too low. Discharge of 

untreated waste may, of course, change the pH 

of lakes, streams, and estuaries to ranges outside the tolerance of some or all organisms 

present.

So, as said before, the technical definition of 

pH may be of little interest to planners and 

managers, but the relation of pH to use of 

water must be recognized.

TURBIDITY

Turbid water looks muddy. Actually, turbidity is defined as capacity to scatter light, 

and is measured by passing a beam of light 

through a tube containing a water sample and 

measuring the intensity of light scattered to a 

sensor set at right angles to the path of the 

beam.

Turbidity is expressed in arbitrary JTU 

(Jackson turbidity units), and the limits for 

water for domestic use are variously set at 1 

to 5 JTU by different authorities. According 

to some criteria (FWPCA, 1968), wastewater 

discharges should not cause turbidity in receiving water greater than 50 JTU in warmwater streams, 25 JTU in warm-water lakes, 

or 10 JTU in cold-water streams or lakes. 

Turbidity is controlled by coagulation, sedimentation, and filtration.

The determination is not exact because the 

particles of clay, microorganisms, and other 

materials that cause turbidity have different 

capacities for scattering light.

SEDIMENT

Sediment consists of those particles of solid 

matter mostly mineral that are transported 

by flowing water. In size, the particles may 

range from grains of clay virtually invisible 

to the naked eye to huge boulders, but generally 

when we speak of sediment we refer to suspended sediment those particles of clay, silt, 

and sand small enough to be transported 

throughout the water body rather than those

119
0 1

1 1

Hydrogen-ion activity increases 

"Acidity" increases

2 3

i i

456

i i i

w 

<D -*

7 8

i i

Normal range i

streams and lakes 1

Hydrogen-ion 

"Basic

9 10 

i i 

Normal range

Acid mine drainage

Corrosive to concrete and 

ferrous metals

ground water 

Full known range for ground water

Primary contact

recreation 

Renge for public water supply, raw and finished

Range for fresh-water fish

Optimum for aquatic

plants for waterfowl food1 

Range for marine I

and estuarine water I

Minimum for 

boiler feed ,

09

O

Varies with 

pressure

Range for irrigation water

Recommended for

milkhouse use 

General range for industrial

process water 

Metal-plating industry

Chemical, explosives, miscellaneous industries

Pulp, paper, paperboard industries

Cotton and wool proc

Food processing, beverage industries

Domestic

sewage

FIGURE 8. pH ranges in relation to use. References: White, Hem, and Waring (1963), FWPCA (1968), Hem (1970), 

Comp (1963).
moved along in contact with the bed of the 

stream (those are called bedload).

"Drinking Water Standards" says nothing 

about sediment. It is assumed that public water 

supplies are adequately filtered. Any tiny particles that might get through are then included 

in "turbidity" as far as "Standards" goes. 

Sediment, however, and the processes that produce it are important factors in overall water 

quality and in planning. In 1968-69, for instance, landslides and mudflows cost individuals 

and taxpayers at least $25 million in the San 

Francisco Bay region alone (Taylor and Brabb, 

1972).

H. P. Guy (1970, p. E3-E4) summarized 

urban erosion and sediment problems. Following are some of the major concerns of sediment 

to the urban planners and managers. According 

to Guy (1970), sediment may affect public 

health as harmful bacteria, toxic chemicals, 

and radionuclides tend to be adsorbed and concentrated on sediment particles; sediment may 

also clog drainage ditches and form favorable 

spots for mosquitos to breed. Sheet, rill, and 

gully erosion is promoted in newly graded 

areas; undesirable changes in those areas may 

result, and the load of sediment may cause damage when deposited downstream. Raindrop impact on bare soil seals the land surface, reducing infiltration, increasing stream runoff, and 

decreasing ground-water recharge. Streams and 

other bodies of water are made unsightly by 

heavy loads of sediment. Their recreation 

potential is materially diminished. Watertreatment costs are increased as sediment concentrations go up. Erosion or deposition of 

sediment may cause bridge or culvert failure 

as well as serious ecological changes by alteration or destruction of the original habitat on 

the bed of the stream or lake. Sediment deposition during floods increases maintenance costs 

for streets, highways, and other public facilities. But perhaps the most serious urban sediment problem is the general deterioration of 

the total environment.

Areas with steep slopes are especially susceptible to erosion when the surface cover is 

disturbed, as during construction. The underlying materials whether rock or sand or clay 

of course strongly influence the erosibility. It 

is desirable when feasible to plan construction for periods when little intense rain is to 

be expected. Prompt restoration of cover of 

one kind or another over soil bared by erosion 

also is always a requisite.

POWERS OF TEN

Powers of ten are a handy and much-used 

device for expressing very large and very small 

numbers. A few "power" expressions are scattered through this circular, especially in the 

sections immediately following. Therefore, for 

ready reference, table 7 lists the powers of ten 

equivalents.

TABLE 7. Powers of fen

One billion 1,000,000,000

One million 1,000,000

One thousand 1,000

One hundred . 100

Ten 10

One 1

0.1

0.01

0.001

0.0001

0.00001

0.000001

0.000000001

IX10' 

1X10" 

IX10* 

1X102 

1X101 

1X10° ixio-1 

ixio-8

ixio-3 

ixio-4 

ixio-5 

ixio-a 

ixio-9

One tenth 

One onehundredth 

One onethousandth 

One tenthousandth 

One hundredthousandth 

One onemillionth 

One one-billionth

Note that the value of zero cannot be expressed 

in powers of ten. As examples of the use of 

the table, 3.4xl03=3,400; 4.9xl05=490,000; 

2.3X~3=0.0023; and 5xl06=0.000005.

CHEMICAL UNITS 

ppm VERSUS mg/1

Parts per million (ppm) and milligrams per 

liter (mg/1) are not exactly the same, for 1 

ppm is one part by weight in IXlO6 (one million) parts by weight (see fig. 9 and table 7), 

and 1 mg/1 is one part by weight in IXlO6 

parts (1 liter) by volume. Luckily, up to concentrations of about 7,000 mg/1, substances in 

solution generally don't change the density of 

water (specific gravity=1.0) enough to matter; 

so 1 liter of solution still weighs very close 

to IXlO3 g (1,000 grams). To that limit, then, 

ppm and mg/1 are numerically interchangeable. 

Beyond the limit, a liter of solution weighs

121
enough more than IXlO3 g that densitycorrection factors are needed. But in planning 

we seldom have to deal with water having concentrations that exceed IXlO3 or 2xl03 mg/1 

(except for cooling water), so we can omit 

further complications.

Mg/l TO pg/1

Most of the common ions and non-ionized 

constituents in water are found and reported 

in concentrations of a few tenths of one mg/1 

to a few hundred mg/1 in waters we are concerned with. However, as trace constituents 

such as chromium, zinc, mercury, and the like 

become of more interest, another scale comes 

into play, and we have units such as: 

fj.g/1 (microgram per liter)

mg/1

=10~6g=ppb part per billion.

ng/1 (nanogram per liter)

mg/1 

= =10-9g=ppt=rpart per trillion.

IXlO6

pg/1 (picogram per liter) 

mg/1

=10-12g=(not used).. 

IXlO9

The term "parts per trillion" has pretty 

much dropped out of use; nanogram is holding 

its own an increasing number of analytical 

procedures achieve that sensitivity. Both ppb 

and its equivalent /tg/1 are used in reporting 

trace constituents, both metallic and those of 

organic nature such as pesticides.

BIOLOGICAL UNITS 

INTRODUCTION

"The coliform count * * * is the only commonly used parameter that bears any direct 

relation to the public health" (Camp, 1963, p. 

209-210). Accepting that premise, we shall 

here talk almost solely about the coliform group 

of bacteria that includes fecal coliform bacteria (until recently called Escherichia coli 

and earlier Bacillus coli), and the coli-aerogenes group of microorganisms that are considered to be indicators of fecal pollution. The 

coliform bacteria are not of themselves known 

to be harmful. But they occur in great numbers, and many are found in the gut and feces 

of warm-blooded animals these are fecal coliform bacteria. Currently, methods are available 

(APHA, 1971, p. 635-636) for determination 

of fecal streptococci and enteric viruses, among 

which are major pathogens (disease-causing 

organisms), but the methods remain largely 

provisional. Hence the bacteriological acceptability of water for domestic use, shellfish culture, water-contact sports, and the like is still 

judged largely by the detectable content of 

coliform bacteria.

The rationale behind that judgment is the 

fact that fecal coliform bacteria, fecal streptococci, and enteric viruses all are discharged 

with animal feces. Therefore, the presence of 

any coliform organisms (fecal used to be hard 

to test for separately) was taken to suggest 

that the pathogenic organisms (streptococci 

and viruses) might also be presenj. And that 

brings us to the terms "MPN" and "colonies 

per 100 ml."

MPN

Before going on, let's recognize two warning flags. One was-hoisted by McKinney (1962, 

p. 129) who said: "The MPN value is not an 

absolute number, but it has been so abused by 

sanitary engineers that the MPN value has 

almost taken absolute significance. A single 

MPN value suddenly becomes an absolute number." The second flag is from "Standard Methods" (APHA, 1971, p. 637), which states: 

"Bacteriologic results must be considered in 

the light of information available concerning 

the sanitary conditions surrounding the source 

of any particular sample." In other words, don't 

read a test result and then shoot from the hip.

MPN INDEX

The MPN (most probable number) is that 

number of coliform bacteria statistically most 

likely to produce the test results observed. The 

MPN index per 100 ml is assigned within 95 

percent confidence limits. Both the index and 

the limits vary with the size of sample portions 

used and with test procedures followed. In 

essence, the MPN index is a manufactured 

number a statistical likelihood analogous to 

a number on an actuarial table and not a 

hard and fast fact. "Standard Methods" 

(APHA, 1971, p. 672-676) gives tables from 

which test results can be converted to the 

MPN index.

122
11

(liter) 1000ml

Weight-volume equivalents for pure water

1 X10~3 I

1 X 10~6 I

.1000

1,000.000

0 1 ml 

(milliliter)

o 

X

 1 n\ 

(microliter)

1000

(kilogram) 

ii

o 

X

0 1 g 

(gram)

o 

X

» 1 mg 

(milligram) 

u

o 

X

1 M9 

(microgram)

kilogram 1 X103 g

1 X 10° g

1000

9

1 X10' 3 g

1,000,000

1 X 10~6 g

FIGURE 9. Weight-volume equivalents for pure water.

COLONY COUNT

In recent years, another method for coliform 

determination has gained increasing acceptance. Briefly, this method involves passing a 

portion of water sample with proper precautions to insure sterility of equipment through 

a paper filter. The filter is transferred to a 

base of nutrient in a petri dish and incubated. 

After 22-24 hours the coliform colonies that 

develop are counted, and the count is calculated, 

if necessary, to the number appropriate to 100 

ml by the equation: 

Coliform colonies per 100 ml

coliform colonies counted x 100

ml of sample filtered

Results are reported as total coliform colonies per 100 ml. Because in this method colonies 

of bacteria are observed, there is no ready way

in which to estimate (or determine) the number of individual bacteria. "Standard Methods" (p. 678-685) discusses the membranefilter (colony count) method, including a modification specific for fecal coliform bacteria.

CAVEAT EMPTOR

"Let the buyer beware" is heard normally 

with reference to commerce and the marketplace. But translated as "let the user beware," 

the warning is not inappropriate.

The colony count and the MPN index are not 

interchangeable, nor can one result be translated to an equivalent in the other units.

For reasons stated and suggested above, the 

U.S. Public Health Service (USPHS, 1962, p. 

3-6) set bacteriological-quality standards for 

drinking water "used by carriers subject to the 

Federal Quarantine Regulations" with a flexi123
bility that recognizes the uncertainties inherent 

in methods now available for coliform determinations.

Most planners and managers may want to 

rely on public-health consultants for advice in 

interpreting MPN-index and colony-count data.

DO BOD TOC COD?

This is neither a request for fish, written in 

medieval English, nor an incantation in some 

exotic language. It's a composite of four characteristics of water, closely related to one another, and all related to what's called the 

"health" of lakes, streams, and estuaries.

DO (dissolved oxygen) is, strictly, a chemical-quality term and is reported in mg/1 or 

ppm or in percentage of saturation. The concentration is determined by chemical methods 

or by use of a special electrode. The ability of 

water to retain oxygen in solution is strongly 

dependent on temperature as, at sea level, 

saturation at 10°C is 11.33 mg/1, but at 30°C 

only 7.63 mg/1. In "healthy" warm-water lakes 

or streams, DO should not fall below 5 mg/1, 

and in cold-water lakes or streams, not much 

below 7 mg/1. Normally, natural water does not 

hold in solution more oxygen than the saturation limits indicated above.

The term "oxygen sag" appears frequently 

in discussions of polluted streams. It refers to 

a marked reduction in dissolved-oxygen content 

that may occur in response to various influences. Normal water bodies show an oxygen 

sag daily as the water warms up in the sun. 

Remember that the warmer the water, the less 

oxygen it can hold in solution. The "sag" disappears as the water cools off at night and 

redissolves oxygen from the air. Such sags 

normally are small and do no damage.

More serious sags occur in response to introduction of loads of oxygen-consuming waste 

or of heated water. Such sags are dissipated 

downstream from the waste discharge. But in 

moderately extreme and sudden loadings, the 

sag may become so severe that fish kills result, 

even though the oxygen depletion may last only 

a short time.

In streams and lakes where nutrient concentrations are high commonly polluted 

waters there is a tendency for algae to multiply into what may be "nuisance blooms." In

those circumstances, and even where algae are 

abundant but not to the "nuisance" level, the 

traditional oxygen-sag pattern is reversed. In 

sunlight the algae, being plants, produce oxygen by photosynthesis and the daylight hours 

in consequence are hours of high oxygen content. At night, respiration (the reverse of 

photosynthesis) occurs, the algae take oxygen 

back from the water, and concentrations diminish progressively until daylight restores photosynthetic activity. Eventually, the algae die off 

and the processes of their decay impose a heavy 

oxygen demand on the water, so a long-lasting, 

serious, and sometimes deadly oxygen sag is 

formed.

BOD (biochemical oxygen demand) is a 

laboratory assay of the consumption of DO in 

water samples by oxidation of organic materials or use by microorganisms in metabolic 

processes. The common procedure requires incubation of sample plus oxygen-saturated water 

for 5 days. BOD is, therefore, often reported 

as "5-day BOD." The units are mg/1. The BOD 

is determined by analyzing for the DO remaining in the sample after 5 days of incubation. 

BOD determinations are most useful when 

applied to wastewaters. Values of BOD for 

stream and lake waters are hard to interpret 

because of large differences between the laboratory environment of the test and the natural 

environment from which the samples came. 

However, in broad terms, a high BOD suggests 

a water burdened with organic wastes and 

therefore likely to be deficient in oxygen 

therefore a water in which only certain plant 

and animal life can survive.

TOC (total organic carbon) is recognized in 

the 1971 edition of "Standard Methods" as a 

tentative procedure that involves oxidation of 

organic carbon in the water to CO2 (carbon 

dioxide) and determination of C02 in a gas 

analyzer. Results are reported in mg/1 of carbon. At present, there is no automatic way to 

interpret TOC in terms of BOD or other related measures of organic pollution. In a study 

of a particular water body, it may be possible 

to develop by trial and comparison, a relation 

between TOC and BOD that is appropriate to 

that particular study, but the relation cannot 

be transferred to other environments across 

the board.

124
COD (chemical oxygen demand) provides a 

quick, rough measure of the loads of pollution 

or oxidizable materials in water. The COD test 

is based on the fact that organic compounds, 

with few exceptions, can be oxidized by strong 

oxidizing agents under acid conditions. Samples are heated with strong oxidizing agents, 

the organic material is oxidized, and the amount 

of oxygen required for this oxidation is calculated in terms of mg/1. COD tests give a general estimate of organic loading in water, but 

cannot be used interchangeably with BOD 

values.

RADIOLOGICAL UNITS

Threat to health and life from radiation 

has haunted us at least since Hiroshima and 

Nagasaki. Physicians, public health officials, 

and biologists are concerned with units such 

as the "r" (roentgen), "rad" (radiation absorbed dose), and "rem" (roentgen equivalent 

man). These and others are denned and discussed by McKee and Wolf (1963, p. 343-354).

Although the rads, rems, and so on are really 

what we care about for reasons of personal 

and public health, the "RBE" (relative biological effectiveness) of the several types of 

radiation emitted by radioactive substances 

effectively precludes easy interpretation of their 

concentrations in water supply. The varying 

responses to radiation in different parts of the 

body and from individual to individual 

further fog the view.

Consequently, limiting concentrations have 

been set by different agencies at different levels. 

The controversy continues.

The occurrence of radioactivity in water also 

is reported in several ways. The reporting units 

may be based on various assumptions (McKee 

and Wolf, 1963, p. 343-354; Hem, 1970, p. 

209-215).

Uranium, commonly thought of as the radioactive element, actually is a sluggard because 

of its slow rate of radioactive disintegration 

(long half-life). In water analyses, uranium 

is commonly reported in micrograms per liter. 

Uranium is sparingly soluble. Hem (1970, p. 

212) cited concentrations of 0.1 to 10 /tg/1 as 

the normal range in natural water.

Other radioactive substances are present in 

water in smaller quantities that are extremely

hard to measure directly. Some, however, are 

much livelier than uranium, and disclose their 

presence by radioactivity. Their "concentrations," therefore, are commonly expressed in 

water analyses by activities in /*c/l (microcuries 

per liter) or pc/1 (picocuries=micromicrocuries per liter). Activities are measured by 

mechanically sensing and counting (as with a 

Gieger counter) radioactive emissions.

A c (curie) is a measure of rate of decay of 

a radioactive substance and is denned as 

3.70xlO10 disintegrations per second (McKee 

and Wolf, 1963, p. 343). A Mc (microcurie) is 

one one-millionth of a curie s or 3.70x10* disintegrations per second, and a picocurie is one 

one-trillionth of a curie or 3.70xlO~2 disintegrations per second say 2-3 counts per minute, in round numbers.

Health standards are expressed in MFC 

(maximum permissible concentration) which 

takes into account such things as the degree to 

which the human body accumulates and stores 

the element in question, the element's half-life, 

the average daily intake of water by people, 

and sources of the element other than water. 

The complexity is compounded by our rather 

scanty knowledge of some of the factors just 

named and confounded further by differences 

of opinion among people setting MFC values. 

No wonder MFC's are not the same worldwide.

Among 18 radionuclides tabulated by McKee 

and Wolf (1963) table 8-1), four are emitters 

of alpha particles but of those, only radium226 is important. So, commonly, water analyses 

for radioactive elements assign all alpha activity to radium-226 and report radium in terms 

of pc/1 (picocuries per liter, remember?). U.S. 

Public Health Service (1962, p. 58) cited 3 

pc/1 as a limit for radium-226, and 10 pc/1 as 

a limit for strontium-90 activity, where separable. The World Health Organization, playing it conservatively, has indicated a limit of 

1 pc/1 alpha as surely safe, but went on to say 

"Higher figures * * * may be safe" if absence 

of dangerous radionuclides can be demonstrated 

(McKee and Wolf, 1962, p. 348).

The same source shows a level of 10 pc/1 as 

safe for beta (and presumably gross betagamma) activity. Beta-gamma activity is reported in either microcuries or picocuries per 

liter.

125
These, then, are a few (but not all) of the 

problems in understanding reports of radioactivity in water. Most planners and managers 

may want to leave interpretation of radiological 

hazards to their public-health consultants.

WATER-QUALITY STANDARDS AND CRITERIA

The Federal Water Pollution Control Act 

amended by the Water Quality Act of 1965 

authorized indeed required all States and 

the Federal Government to establish waterquality standards for interstate streams and 

coastal waters. The law included a requirement 

that standards to be set should "protect the 

public health or welfare, [and] enhance the 

quality of water * * * ." The "enhance" provision proved to be controversial as many States 

felt maintenance of the status quo was enough 

to ask. However, in the end, the 50 States complied, and water-quality standards were established.

In addition, various river-basin commissions, 

regional water-pollution control boards, international treaties, and other governmental 

bodies have their own sets of standards or criteria. It is infeasible to assemble them all or 

even to find a representative series of examples. 

Their numbers are too many and their purposes hence requirements too diverse.

There is a good deal of confusion in use of 

the terms "standards" and "criteria." The Federal Water Pollution Control Administration 

(now the Environmental Protection Agency) 

reported (FWPCA, 1968, p. v) the following 

definitions:

Standard a plan that is established by governmental 

authority as a program for water pollution prevention and abatement.

Criteria a scientific requirement on which a decision or judgment may be based concerning the 

suitability of water quality to support a designated 

use.

McKee and Wolf (1963, p. vii) said in this 

connection:

* * * the use of the word "standard" has been avoided

* * * for its signifies "any definite rule, principle, or 

measure established by authority." Instead "criterion" 

has been chosen for it designates "a means by which 

anything is tried in forming a correct judgment respecting it."

Putting those ideas together, one may conclude that a set of criteria are assembled, 

usually experimentally, that tell you what is

known about the behavior of substances in 

water whether they are harmful or beneficial, 

and in what concentrations the harm or benefit 

is likely to occur. Then, on the basis of ttiose 

data, an agency with authority to do so, sets 

guidelines or rules (see below) as water-quality 

standards.

The most widely quoted and sometimes 

misquoted set of water-quality standards in 

the United States most likely is the Drinking 

Water Standards, 1962, published by the U.S. 

Public Health Service (1962) of the Department of Health, Education, and Welfare. Those 

standards (rules, regulations, limits) have been 

widely accepted by local health agencies which 

have modeled their own accordingly or 

adopted the USPHS standards across the 

board. The standards have been widely quoted 

in the literature on water quality and used to 

evaluate potential supplies in terms of their 

acceptability for drinking water.

And in the process, an important distinction 

has sometimes been overlooked, which is why 

the reference was made to misquotation. There 

are two types of limits in the standards, carefully defined in the book (USPHS, 1962, p. v). 

The two are:

(a) Limits which, if exceeded, shall be grounds for 

rejection of the supply. Substances in this category 

may have adverse effects on health when present in 

concentrations above the limit.

Type (a) limits are often referred to as the 

mandatory limits.

(b) Limits .which should not be exceeded whenever 

more suitable supplies can be made available at reasonable cost.

Type (b) limits are the recommended limits. 

In effect, those limits are desirable because, if 

exceeded, the water may be esthetically displeasing or may cause nonlethal but unpleasant 

reactions in the more susceptible users of the 

water. It's nice not to exceed the recommended 

limits but an excess is not necessarily 

grounds for rejecting the supply if you can't 

do better. A case in point involves the commonly quoted "limit" of 500 mg/1 dissolved 

solids (or 1,000 mg/1 when better water is not 

available) that appears in the USPHS Standards. Many a water report implies that water 

having a higher dissolved-solids concentration 

cannot be used for public supply. But USPHS 

Standards (1962, p. 33) itself says, "More than 

100 public supplies in the United States pro126
vide water with more than 2,000 mg/1 of dissolved solids. Newcomers and casual visitors 

would certainly find these waters almost intolerable * * * [but] many are able to tolerate 

if not to enjoy these highly mineralized 

waters."

The moral of this story is: know the Federal, State, and local regulations that apply to 

your own circumstance. And bear in mind the 

critical difference between mandatory and 

recommended limits.

The USPHS standards (abbreviated) and 

those of WHO (World Health Organization) 

are shown in table 8.

TABLE 8. Comparison of chemical constituents in the drinking water standards of the World Health Organization and the 17.S. Public Health Service

Concentrations in milligrams per liter

WHO International (1971)

Anionic detergents _ _ _ .

Arsenic _ _.

Barium _ _ _ _ _.

Cadmium _.

Calcium .

Carbon chloroform extract _______

Chloride ___ - ___ - _________ .

Chromium (hexavalent) _ _ ___ _ _ .

Copper .

Cyanide _ _ _ .

Fluoride .

Iron .

Lead __ ___ __ _ . Magnesium _ ___ __ ___ __ _.

Manganese _ .

Nitrate (as NO8 ) ____________ .

Phenolic compounds (as phenols) __

Selenium _______ _ _____ _ __ .

Silver ____ _ _____ _ ________ .

Sulfate _________________ .

Total solids ____ _ _________ .

Zinc _ __ ____ ______ _ _ .

Highest

desirable

level

. 0.2

_

. 75

. 200

. __ .05

. __ Same as USPHS

. __ .1

. __ "150

. __ .05

. __ .001

. __ 200

. __ 500

. __ 5.0

Maximum

permissible

level

1.0

.05

.01

200

600

1.5

.05

1.0

.1

150

.5

45

.002

.01

400

1,500

15

U.S.P.H.S.

Recommended

limit

0.5

.01

£

250

 

1.0

.01

1 0.8-1.7

.3

.05

45

.001

250

500

5.0

(1962)

Maximum

allowable

0.05

1.0

.01

___

.05

.2

1 1.6-3.4

.05

___

_ -.

__ 

-__

.01

.05

 «...

___

1 Recommended limits and maximum allowable concentrations vary inversely with mean annual temperature. 

8 If there are 250 mg/1 of sulfate present, magnesium should not exceed 30 mg/1.

GLOSSARY

Acre-foot. The quantity of water needed to cover 1 

acre to a depth of 1 foot. Equals 43,560 cubic feet= 

1,233.4 cubic meters=325,851 gallons=1,23 3,000 

liters.

Activity. Here used as measure of rate of decay of 

a radioactive element. Each departure of proton, 

neutron, etc., from an atom of an element is a 

disintegration, an event that can be recorded instrumentally. So activity is an expression of the rate 

of radioactive disintegration, registered by counts, 

as on a Geiger counter.

Aquifer. A subsurface water-bearing unit that transmits water rapidly enough to supply useful quantities to springs and wells. Sand and gravel aquifers 

are characterized by innumerable spaces around and 

among the grains. Water is stored in and moves 

through those spaces. Limestone may have intergranular spaces but commonly stores and transmits 

water in small to cavernously large openings formed 

by solution. Lavas, especially basalt, store and transmit water in cracks and in bouldery zones of rubble 

between successive flows of lava.

Baseflow. Low flow in streams; occurs typically during 

long periods between rains when streamflow is maintained mostly or entirely by ground-water discharge.

Biochemical oxygen demand (BOD). A measure of the 

living and nonliving organic demand for oxygen 

imposed by wastes of various kinds. A high BOD may 

temporarily, or permanently, so deplete oxygen in 

water as to kill aquatic life. The determination of 

BOD is perhaps most useful in evaluating impact of 

wastewater on the receiving water bodies.

Celsius, degrees (°C). A temperature scale based on 

100 equal divisions (degrees) between the freezing 

temperature of water (taken as 0°C) and the sealevel boiling temperature (taken as 100°C). Named 

for Anders Celsius, an 18th century Swedish astronomer who devised the scale.

Chemical oxidiation demand (COD). A quick (and only 

approximate) measure of loads of oxidizable matter 

in water. Results cannot be used interchangeably with 

BOD values. However, COD can quickly identify

127
water with very low or very high BOD potential. 

Coli-aerogenes group. See Coliform bacteria. 

Coliform bacteria. A large and varied group of bacteria. 

The fecal coliform bacteria flourish in the guts and 

feces of warm-blooded animals, including man. 

Escherichia coli (E. coli) is largely of fecal origin 

and has been the indicator organism most commonly cited as indicating sewage or feedlot pollution. 

The coliforms apparently do not themselves cause 

disease, but their presence in water suggests that 

disease-causing organisms (pathogens) may also 

be present. Coliform bacteria are used as indicators 

of pollution because they are abundant and their 

presence is fairly easy to detect. The coli-aerogenes 

group is also among indicator organisms and is 

not usually distinguished from other fecal coliforms. 

Fecal streptococci and enteric viruses are pathogens 

found in animal wastes. Methods for their identification in water remain provisional. The presence 

of fecal coliform bacteria suggests that streptococci 

and viruses may be present hence the concern over 

danger of infection whenever large numbers of fecal 

coliform bacteria are detected in water. (See Most 

Probable Number.)

Conjunctive use. Planned management of surface- and 

ground-water resources as a single, interlocking system.

Cubic foot per second (cfs). A flow rate=28.32 liters 

per second=448.831 gallons per minute. Same as 

second-foot or British cusec.

Curie. See Activity.

Cusec. See Cubic foot per second.

Dissolved oxygen (DO). DO concentration of unpolluted 

water depends pretty much on atmospheric pressure 

and temperature. Therefore it is greater at sea level 

and when water is cool than at high altitudes or 

when water is warm.

Nonliving organic matter (especially its content 

of carbon in any form) and various chemicals react 

with oxygen in water, depleting the oxygen and causing stress from lack of oxygen on fish and other 

aquatic life. In extreme depletion, water may become 

anaerobic (literally without air), stagnate, and stink.

Electrical conductivity. See Specific conductance.

Enteric viruses. See Coliform bacteria.

Fahrenheit, degree (°F). The familiar thermometer 

scale in which freezing temperature of water is 32°F 

and boiling at sea level is 212°F. Named for Gabriel 

D. Fahrenheit, an 18th century German physicist.

Fecal coliforms. See Coliform bacteria.

Fecal streptococci. See Coliform bacteria.

Ground water. Subsurface water that completely fills 

(saturates) all available space within an aquifer and 

below the top of the zone of saturation. Contrast with 

Water in unsaturated zone. Ground water does not 

occur in subsurfaces "lakes" nor move in subsurface 

"rivers" except those in a few caves in limestone.

Half-life. See Radioactivity.

Ion. An electrically charged particle of matter dissolved 

in water. For instance, common table salt has no 

chemical charge. In water, salt "dissociates;" each 

molecule of salt (NaCl) forms one ion of sodium

(Na+1 ) with a positive charge, and one ion of chloride 

(Cl-1 ) with a negative"charge. (Chlorine is a gas; 

each molecule consists of two atoms of the element 

chlorine. In water, the atoms travel alone, are electrically charged, and are called chloride ions.)

Kilogram (kg). A unit of weight= 1,000 grams= 

weight of 1 liter of pure water.

Liter (1). Metric measure of volume=1,000 ml (milliliters). For pure water, 1 liter weighs 1 kilogram= 

1,000 grams.

Maximum permissible concentration (MFC). A standard intended to govern the concentration of a radioactive substance allowable in drinking water. Standards and only a few have been suggested differ 

from place to place. The MPC for any element is set 

on the basis of variables such as sources other than 

water from which the element may be absorbed, degree to which element accumulates in the body, estimated daily intake of water, and half-life of the 

element.

Microcurie. See Activity.

Microgram G*g). One one-millionth of a gram= 

IXlO-g.

Microgram per liter G*g/l). One one-millionth of a gram 

of substance in 1 liter of water. Equals part per 

billion (ppb) because 1 liter of pure water weighs 

1,000 grams, so we have 1 one-millionth of 1 gram 

in 1,000 grams, or 1 ppb by weight. Used in identifying and reporting trace concentrations of heavy 

metals or of pesticides.

Micromhos. See Specific conductance.

Milligram per liter (mg/1). One part by weight of dissolved chemical, or suspended sediment, in 1 million 

parts by volume ( = 1 liter) of water. Numerically 

equivalent to parts per million (ppm) between 0 

and about 7,000 mg/1.

Milliliter (ml). One one-thousandth of a liter=the volume of 1 gram of pure water.

Miner's inch. Obsolete unit of measure in western 

States; variously, 38.4, 40, and 50 miner's inches= 

1 cubic foot per second, as set by law in different 

States. Still the basis for some old water rights.

Most Probable Number (MPN). A statistical evaluation of degree of water pollution based on presence 

of coliform bacteria. It is not feasible to identify 

the exact concentration of coliform bacteria in a 

water sample. The MPN interprets test results in 

terms of results observed. (See Coliform bacteria.)

Nanogram per liter (ng/1). One one-billionth of a gram 

of substance in 1 liter of water. Equals part per 

trillion (ppt) because 1 liter of pure water weighs 

1,000 grams, so we have 1 one-billionth of one gram 

in 1,000 grams, or 1 ppt by weight. Trace concentrations of heavy metals or of pesticides are reported in 

nanograms per liter. "Parts per trillion" has pretty 

much dropped out of use.

Part per billion (ppb). See Microgram per liter.

Part per million (ppm). One part by weight of dissolved 

chemical, or suspended sediment, in 1 million parts 

by weight of water. Numerically equivalent to milligrams per liter (mg/1) between 0 and about 7,000 

ppm.

128
Part per trillion (ppt). See Nanogram per liter.

pH. Measure of hydrogen-ion activity in solution. Expressed on a scale 0 (highly acid) to 14 (highly 

basic). pH 7.0 is a neutral solution, neither acid nor 

basic.

Pathogens. See Colif orm bacteria.

Picocurie. See Activity.

Powers of ten. A convenient notation based on multiples of 10 ten raised to a positive or negative exponent. The number 1.0 is 1 times 10 to the zero 

power (1X10°). Positive exponents (powers) are 

numbers greater than 1.0. Negative exponents express numbers (decimal fractions) smaller than 1.0. 

Each increase of 1 in the exponent (power) is 

equivalent to moving the demical point one place 

positive to the right, negative to the left. By convention, the number expressed as a power of 10 is 

stated as one whole number to left of decimal, plus 

whatever is needed to complete the number, times 

10 to the appropriate power. For instance: 

365 million=3.65 X 10s

365 million ths=3.65X10^, which is handier 

(once you're used to it) than its equivalent

365

0.00000365, or even . 

1,000,000

Radiation absorbed dose (rad). A measure of the radiation dose absorbed by matter (as human tissue, for 

example). The rad is about equivalent to the absorption of 1 roentgen (r) of X-rays.

Radioactivity. The property of some elements of giving off particles or rays or both. The rays are gamma 

or X-rays. The particles are alpha particles (like 

the nucleus of a helium atom), neutrons, or protons. 

The process is called radioactive decay. Decay rate 

is measured by the half-life that is, by the time it 

takes for one-half the available particles to be given 

off. Uranium decays slowly and has a half-life of 

about 4.5 billion years. Strontium-90 has a half-life 

of 28 years. Tritium (radioactive hydrogen) has a 

half-life of about 12.5 years. Some man-made radioactive elements have half-lives of tiny fractions of a 

second.

Radionuclide. A radioactive atom having (1) a specified number of protons and neutrons (therefore a 

specified mass), and (2) the property of giving off 

protons, neutrons, or rays at a specified time rate.

Recharge. Addition of water to an aquifer. Occurs 

naturally from infiltration of rainfall and of water 

flowing over earth materials that allow water to infiltrate below land surface. Artificial recharge 

through injection wells, or by spreading surface 

water where it will infiltrate is widely practiced in 

some places such as southern California and Long 

Island, N.Y., both to store water where it won't 

evaporate and to protect ground-water bodies from 

intrusion of sea water into aquifers.

Relative biological effectiveness (RBE). A measure of 

the relative effect on man of various types of radiation. One rad of alpha particles or of neutrons or 

protons has 10 times the RBE of 1 rad of beta particles or gamma or X-rays. Heavy recoil nuclei are 

estimated to be 20 times as damaging as X-rays on 

the same scale.

Roentgen (r). A measure of radiation (as X-rays= 

gamma rays). One r produces in 1 cubic centimeter of 

air, ions that carry one electrostatic charge.

Roentgen equivalent man (rem). The quantity of radiation of any kind that has the same effect on man as 

does absorbing 1 roentgen (r) of X-rays. The various 

kinds of radiation considered are gamma and Xrays, beta particles, alpha particles, neutrons and 

protons, and heavy recoil nuclei.

Second-foot (cfs). See Cubic foot per second.

Specific conductance (Sp. cond.). Literally specific electrical conductance (or electrical conductivity) a 

measure of the capacity of water to conduct an eletrical current under standard test conditions. Increases as concentrations of dissolved and ionized 

constituents increase. Actually measured as resistance 

(in millionths of an ohm) but reported usually as 

micromhos (reciprocal of millionths of an* ohm). 

As a rule of thumb, dissolved-solids concentration 

(in mg/1) is 60-70 percent of specific conductance 

(in micromhos).

Surface water. The water we see on the land surface, as 

in lakes, ponds, and streams.

Total organic carbon (TOC). A newly developing test for 

the one constituent, carbon, in wastewater that perhaps most influences BOD. Relations between TOC 

and BOD must still be determined by trial and error 

in specific studies before TOC alone can be used as 

an index of organic pollution of a waterbody.

Turbidity. Defined as capacity of materials suspended in 

water to scatter light Measured in arbitrary Jackson turbidity units (JTU). Highly turbid water is 

often called "muddy," although all manner of suspended particles contribute to turbidity.

Water in unsaturated zone. Water, including soil moisture, below land surface but above the zone of saturation where all available space is filled by water. This 

water may percolate down to the zone of saturation 

to become ground water, or may, as soil moisture 

does, return to the surface by capillary attraction or 

in roots of plants.

REFERENCES

American Public Health Association, 1971, Standard 

methods for the examination of water and wastewater [13th ed.]: New York, American Public 

Health Asoc., Inc., 874 p.

Camp, T. R., 1963, Water and its impurities: New 

York, Reinhold Publishing Corp., 355 p.

Ciaccio, L. L. [ed.], 1971, Water and water pollution 

handbook: New York, Marcel Dekker, Inc., v. 1, 

449 p.

Durfor, E. N., and Becker, Edith, 1964, Public water 

supplies of the 100 largest cities in the United 

States, 1962: U.S. Geol. Survey Water-Supply 

Paper 1812, 364 p.

Flack, J. E., 1971, Future trends in water use, in 

Treatise on urban water systems [M. L. Albert129
son, L. S. Tucker, and D. C. Taylor, eds.]: Fort 

Collins, Colorado State Univ., p. 319-325.

Flynn, J. M., 1961, Impact of suburban growth on 

ground water quality in Suffolk County, New 

York, in Proceedings 1961 symposium on ground 

water contamination: U.S. Dept. Health, Education, and Welfare, p. 71-82.

Federal Water Pollution Control Administration, 1968, 

Water quality criteria: Report of the National 

Technical Advisory Committee to the Secretary of 

the Interior: Federal Water Pollution Control 

Admin., 234 p.

Guy, H. P., 1970, Sediment problems in urban areas: 

U.S. Geol. Survey Circular 601-E, 8 p.

Hem, J. D., 1970, Study and interpretation of the chemical characteristics of natural water [2d ed.]: U.S. 

Geol. Survey Water-Supply Paper 1473, 363 p.

Leopold, L. B., and Langbein, W. B., 1960, A primer 

on water: U.S. Geol. Survey special publ., 50 p.

McKee, J. E., and Wolf, H. W., 1963, Water quality 

criteria: California State Water Quality Control 

Board Pub. 3-A, 548 p.

McKinney, R. E., 1962, Microbiology for sanitary engineers: New York, McGraw-Hill Book Co., Inc., 

293 p.

Murray, C. R., and Reeves, E. B., 1972, Estimated use 

of water in the United States in 1970: U.S. Geol. 

Survey Circ. 676, 37 p.

Reid, G. W., 1971, The macro-approach urban water 

demand models, in Treatise on urban water systems [M. L. Albertson, L. S. Tucker, and D. C. 

Taylor, eds.]: Fort Collins, Colorado State Univ., 

p. 235-294.

Rudolfs, Willem [ed.], 1953, Industrial wastes, their 

disposal and treatment: New York, Reinhold Publishing Corp. [republished by Library of Engineering Classics, Valley Stream, N. Y., 1961], 

497 p.

Savini, John, and Kammerer, J. C., 1961, Urban growth 

and the water regimen: U.S. Geol. Survey WaterSupply Paper 1591-A, 43 p.

Schneider, W. J., and Spieker, A. M., 1969, Water for 

the cities the outlook: U.S. Geol. Survey Circular 601-A, 6 p.

Taylor, F. A., and Brabb, E. E., 1972, Maps showing 

distribution and cost by counties, of structurally 

damaging landslides in the San Francisco Bay 

region, California, winter of 1968-69: U.S. Geol. 

Survey Misc. Field Studies Map, MF-327, 1 sheet.

U.S. Geological Survey, 1968, Water and industry: U.S. 

Geol. Survey pamphlet.

 1968, Water of the world: U.S. Geol. Survey 

pamphlet.

 1969, What is water?: U.S. Geol. Survey 

pamphlet.

U.S. Public Health Service, 1969, Drinking water standards: [U.S.] Public Health Service Pub. 956, 61 p.

 &U.S. GOVERNMENT PRINTING OFFICE: 1978 O 261-221/144

130