*' Prepared in cooperation with the California Department of Water Resources X;;';i-*j|

gs'... GEOLOGICAL SURVEY WATER-SUPPLY PAPER 1972 I i"*

^ 'W-'i-^^V'.;'.^- .V r.-n..---.... -..(fc-..---^^ -. .'. _- -; .-\-_^t>-?«»^

^
The

Lake Tahoe Basin, 

California-Nevada
Looking north-northeast over Fallen Leaf Lake and Lake Tahoe. The community of South Lake Tahoe is near the shore at the end of the lake to the right, 

and Crystal Bay, at the north end of the lake, is at the extreme left. (Courtesy of 

Air-Photo Co., Inc.)
The

Lake Tahoe Basin, 

California-Nevada

By J. R. Crippen 

and B. R. Pavelka

Prepared in cooperation with 

the California Department 

of Water Resources

GEOLOGICAL SURVEY WATER-SUPPLY PAPER 1972
DEPARTMENT OF THE INTERIOR 

MANUEL LUJAN, Jr., Secretary

U.S. GEOLOGICAL SURVEY 

Dallas L. Peck, Director

First printing 1970 

Second printing 1971 

Third printing 1990

Library of Congress catalog-card No. 74-606660

U.S. GOVERNMENT PRINTING OFFICE 

WASHINGTON : 1970

For sale by the Books and Open-File Reports Section 

U.S. Geological Survey, Federal Center, Box 25425, Denver, CO 80225
CONTE1 ITS

Introduction ................. i

Geography ................. 2

Location ................. 2

Physical geography ............. 3

Geology ................. 13

How the basin was formed .......... 14

Rocks and soils of the basin .......... 15

Climate ................. 18

Vegetation, fish, and wildlife ........... 23

History .................. 24

Exploration and settlement ........... 24

Trends in population and land use ......... 26

Water resources ................ 28

History of water use ............. 28

Hydrology ................ 33

Limnology ................ 40

Contamination ............... 44

Maps of the basin ............... 4?

Outstanding lakes of the world ........... 49

Selected references ............... 51

Index ................... 53

FIGURES

1 Map showing principal cities and highways in the vicinity of

Lake Tahoe ............... 3

2 Map showing depths of water in Lake Tahoe ..... 4

3 Map of the Lake Tahoe basin .......... 5

4 Profile of the perimeter of the Lake Tahoe basin ..... 10

5 Map showing altitudes in the Lake Tahoe basin ..... 11

6 Topographic cross section of the Lake Tahoe basin at Tahorra,

Calif. ................. 12

7 Map showing types of rocks in the Lake Tahoe basin . . 16

8 Schematic diagram showing climate and topography from the

Pacific Ocean to Carson Valley ......... 20

9 Map showing mean annual precipitation in the Lake Tahoe

basin ................. 21

10 Map of the Truckee River ........... 29

11 Schematic diagram showing estimated annual hydrologic

budget of the Lake Tahoe basin ......... 35

12 Map showing principal subbasins contributing to Lake Tahoe

and their estimated average annual flow ...... 38

13 Index to Geological Survey maps of the Lake Tahoe basin . . 48

TABLE

Estimated statistics of the annual hydrologic budget of the Lake 

Tahoe basin, 1901-66 ............ 36
THE

LAKE TAHOE BASIN, 

CALIFORNIA-NEVADA

By J. R. CRIPPEN and B. R. PAVELKA

INTRODUCTION

Lake Tahoe and the mountains that form its basin provide vistas 

and environments among the most beautiful in the Sierra Nevada. The 

region offers opportunities for both rest and recreation to suit a great 

variey of tastes. In addition to the natural beauty of the lake, the shoreline, the mountains, and the streams, there are facilities for almost all 

related summer and winter sports. These attractions are in a fairly 

compact region that is within 1 or 2 days driving distance for about 

25 million people. The beauty and the recreational facilities of the 

region attract sightseers, short-time visitors, and seasonal res: dents in 

both summer and winter. Others come to visit the casinos that have 

sprung up in parts of the basin in Nevada.

Tourists and part-time residents provide the major source of income 

for the area, and the great increase in tourism during the past two 

decades has had a tremendous impact not only on the economy of the 

Lake Tahoe basin but also on the environment. Hotels, motels, restaurants, and gas stations mushroomed almost overnight; unfortunately, their presence is somewhat incongruous with an area Mark 

Twain once called "the fairest picture the whole earth affords." The 

many privately owned lakeshore properties may lead to a shortage of 

facilities for public enjoyment of the shoreline. The concent~ation of 

commercial development in a few areas near the lake has caused acute 

traffic congestion during the summer and on winter weekends during 

the skiing season.

The most immediate problems are waste disposal and consequent
pollution, for the lake itself is the terminal for all liquid wastes and 

contaminants in the basin. Local, State, and Federal agencies are working together seeking ways to control future pollution. Because of the 

great beauty and purity of the lake, it is unusually subject to despoilment by the introduction of wastes that our way of life produces. Much 

of the attraction of the basin lies in the opportunity for enjoyment of 

nature, at once spectacular and pristine.

The rapid growth of tourism and the publicity given to the possibility 

of pollution of Lake Tahoe have resulted in a great demand for 

information concerning the lake and its environment. Much has been 

written about the history of the region; there are techrical reports 

about various aspects of the natural and manmade environments and 

popular pamphlets describing the local attractions. This report summarizes many facts about Lake Tahoe and its environment and gives 

special emphasis to the hydrology and the water problems of the 

region. The report is not a deeply scientific exposition; however, it 

does contain some technical information that may help in understanding the interplay of geologic, climatic, and hydrologic factors 

that affect the natural environment of Lake Tahoe and the interactions 

between man's way of life and his environment. A bibliography is 

included for those who are interested in more comprehensive studies 

of the area. Much of the information in this report was derived directly 

or indirectly from one or more of these references, and some of the 

opinions expressed here are based on data presented in them.

GEOGRAPHY

LOCATION

Lake Tahoe lies high in the Sierra Nevada, and occupies a valley 

bounded by the main range of the Sierra Nevada on the vest and the 

Carson Range, an offshoot ridge to the east. It is almost midway between the California gold belt and the gold and silver mining area 

of Virginia City, Nev. The lake is about 150 miles northeast'of the 

Pacific Ocean at San Francisco's Golden Gate. The California-Nevada 

State line passes through the lake and divides the basin (including 

the lake itself and the watershed that contributes to it), so that roughly 

two-thirds is in California and one-third in Nevada. The basin includes parts of three California counties El Dorado, Placer, and 

Alpine and three Nevada counties Douglas, Ormsby, and Washoe. 

Figure 1 shows Lake Tahoe in relation to principal population centers 

in the region.
113 116

40 C

33'

as Vegas

Needles

Santa Barbara

Los Angeles

San Diego)

FIGURE 1 ' ' Principal cities and highways in the vicinity of Lake Tahoe.

PHYSICAL GEOGRAPHY

Lake Tahoe is an irregular oval, about 22 miles long from rorth to 

south and 12 miles wide. It lies in the northern part of a basin that 

is about 40 miles long from north to south, and 10 to 18 miles wide. 

Figure 2 shows the lake, with lines that indicate its depth, and 

figure 3 shows the entire drainage basin. Some of the statistics pertaining to the lake and its contributing watershed are:

Surface area of Lake Tahoe. .... ......... 191 square miles

(122,000 acres) 

Altitude of the surface.................... 6,225 feet above

mean sea level 

Average depth of water. ......... ........ 1,000 feet

Greatest measured depth. . ........... ... 1,645 feet

Volume of water in the lake. ..... ...... 122,000,000 acre-feet

(40,000,000,000,000 gallons)

Area of contributing watershed 315 square miles 

(exclusive of the lake itself). (202,000 acres)

3
About 134 square miles of the lake is in California, and 57 square 

miles is in Nevada.

Statistics on Lake Tahoe show that the volume of water in the lake 

is exceptionally great in proportion to the surface area. Lake Erie, 

which has more than 50 times the area of Lake Tahoe, contains less 

than five times as much water. The water in Lake Tahoe would cover 

a flat area the size of California to a depth of slightly more than 14 

inches. About 150 square miles of the lake is more than TOO feet deep, 

and 100 square miles is more than 1,200 feet deep. In North America 

only two lakes are known to be deeper than Lake Tahoe: Crater Lake

FIGURE 2 '-" Depths of water in Lake Tahoe.
120 C

EXPLANATION 

Basin boundary

FIGURE 3 The Lake Tahoe basin.

in Oregon (1,930 ft deep) and Great Slave Lake in northern Canada 

(2,010 ft deep). In all the other continents there are only seven lakes 

known to be deeper than Lake Tahoe. It is the highest lake of its size 

in the United States; its only rival, Yellowstone Lake in Wyoming, is
137 square miles in area and the altitude of the lake surface is about 

7,735 feet.

The water in Lake Tahoe is pure and exceptionally clear. All natural 

water contains dissolved solids, but streams flowing from mountain 

regions that drain granitic rock, such as makes up much of the Lake 

Tahoe basin, usually carry less dissolved materials than do lowland 

streams. Lake Tahoe water contains from 60 to 70 mg/1 (milligrams 

per liter, equivalent to parts per million> by weight) of dissolved 

minerals roughly, 1 pound in 1,800 gallons of water. Lake Michigan 

contains about 120 mg/1, Crater Lake about 80, Lake Superior about 

60, and Moosehead Lake in Maine less than 20.

The clarity of the water is well known. Under the proper conditions of natural lighting and surface smoothness, underwater features 

can be seen at depths of several tens of feet. Scientists sometimes test 

the transparency of water by lowering a Secchi disk (about the size 

of a dinner plate and painted black and white). In Lake Tahoe the 

Secchi disk can sometimes be followed to depths of more than 120 

feet. Most streams and lakes contain solid material in the form of small 

particles of sediment and organic growth that limit visibility to much 

smaller depths. There is little organic matter in Lake Tahoe, as will be 

discussed later in this report. Sediment is brought into the lake by the 

many small contributing streams during winter storms and spring 

snowmelt, but relatively little sediment arrives from May through 

September. Because the lake occupies an area that is notably large with 

respect to the area of the contributing basin, a large proportion of its 

inflow (about 40 percent) reaches it directly in the form of rain and 

snow which contain almost no insoluble material.

Lake Tahoe never freezes over, but ice may form at times along 

the shore in small protected inlets. The water near the surface of 

the lake generally cools to 40° or 45°F during February or March 

and warms to 65° or 70°F during August or September. Below 600- 

700-foot depths the water temperature is always about 39°F.

The lake has about 71 miles of shoreline 42 miles in California 

and 29 miles in Nevada. The most pronounced irregularity in the 

shoreline is Emerald Bay, which covers an area of about 460 acres at 

the southwestern part of the lake. In the bay is Fannette, the only 

island in Lake Tahoe, 2 or 3 acres in area and rising 60 feet above 

the lake surface.

The low point of the lake shore is at Tahoe City, Calif., where the 

Truckee River carries the outflow from Lake Tahoe. The altitude of 

the lake surface is generally given as 6,225 feet above mean sea level; 

however, it ranges from 6,223 feet to 6,229 feet, depending on the 

quantity of inflow and, since 1874, on the operation of gates in a 

low dam at Tahoe City. The natural level of the outlet of the lake 

is about 6,223 feet. The quantity of water subject to regulation between
the levels of 6,223 and 6,229 feet is about 745,000 acre-feet. The lowest 

known level of the lake during historic times is 6,221.74 feet in December 1934, and the highest known level is 6,231.26 feet in July 1907; 

these figures represent a difference in storage of about 1,160,000 acrefeet, less than 1 percent of the total contents of the lake.

The Lake Tahoe basin, which has a perimeter of almost 140 miles 

(fig. 4), is defined as the land and water area contributing to the outflow from Lake Tahoe. More than 100 miles of the basin boundary 

is higher than 8,000 feet above sea level, and almost 50 miles is higher 

than 9,000 feet. Paved highways enter the basin at seven locations 

Brock way Summit, Tahoe City (the lowest, alt about 6,230 ft), Echo 

Summit, and Luther Pass, all in California; Daggett Pass, Spooners 

Summit, and Tahoe Meadows (the highest, alt 8,570 ft), in Nevada. 

The Tahoe Meadows road reaches an even higher altitude about 

8,930 feet at Mount Rose Summit, some 2 miles northeast of the 

boundary of the Lake Tahoe basin.

The highest peaks on the Lake Tahoe basin rim rise from ridge 

lines at four locations. West of Fallen Leaf Lake, Calif., is Dicks Peak 

(alt 9,974 ft). At the southern end of the lake are Stevens Peak and 

Red Lake Peak, both at an altitude of 10,061 feet. The Carson Range, 

in a 7-mile crestline south of the Nevada-California boundary, rises to 

Monument Peak (alt 10,067 ft), Jobs Sister Peak (alt 10,823 ft), and 

Freel Peak, whose altitude (10,881 ft) is the highest point in the 

basin and is about 4,650 feet higher than the surface of Lake Tahoe. At 

the northern end of the basin is a ridge that extends toward Mount 

Rose, Nev. (which is outside the basin), for about a mile at altitudes of 

more than 10,000 feet, the highest point being 10,324 feet. Many square 

miles of the lake bottom lie at altitudes of less than 4,700 feet above 

sea level. Figure 5 is a topographic map of the basin, and figure 6 is a 

cross section that showns graphically the great depth of the lake and 

the flatness of its bed.

Of the 315 square miles of the basin that contributes to Lake Tahoe, 

about 70 square miles lies at altitudes between 6,230 and 6,500 feet. 

Almost all the land in the basin that can be used for agricultural or 

commercial purposes is included in this part. The remainder of the 

land area lies at these altitudes:

Feet Square miles

6,500 to 7,000......................... 60

7,000 to 7,500. ....................... 48

7,500 to 8,500... ..................... 92

8,500 to 10,000......................... 44

More than 10,000.. 1

Within the basin there are more than 150 ponds having surface areas 

of from 1 to 20 acres, about 15 having areas of from 20 to 100 acres, 

and four larger lakes Cascade (210 acres), Upper and Lower Echo
Aerial view looking northwest over Cascade Lake and Em 

outlet of the lake are at the upper right. The mountain 

Fannette Island can be seen near the head of the bay, and a 

Air-Photo Co., Inc.)
, showing the west shore of Lake Tahoe. Tahoe City and the 

md the far shore of Emerald Bay is almost 9,200 feet high, 

 ow sandy beach is visible at the lower right. (Courtesy of
OT

FEET IN ALTITUDE, 

LEVEL SEA MEAN ABOVE 

Meadows Tahoe 

Virginia of Tunnel 

line water City 

Pass Daggett 

_NEVADA 

CALIFORNIA

Peak

Peak Dicks 
120U

Valley 

Peak

9214

Twin Peaks V

3878

EXPLANATION

Altitude, in feet abo 

mean sea level

10.000-11.000

Red Lake Peak 

10,061

FIGURE 5 ^ Altitudes in the Lake Tahoe basin.

(330 acres together), Marlette (350 acres), and Fallen Leaf (1,400 

acres). The total surface area of these lakes is about 5 square miles, 

therefore about 310 square miles of the basin is truly land surface.

Little of the land surface is level; most of it lies at slopes ranging 

from gentle and almost imperceptible to very steep. About half the 

land area of the Lake Tahoe basin has a slope steeper than 20 percent

11
o 

o

8

o

g cr. 

1 § 

> o 

CALIFORNIA 

NEVADA
Looking north from Crystal Bay, in Nevada, to a 9,600-foot-high mountain ridge 

that forms part of the northern boundary of the basin.

(that is, 1 ft of rise for each 5 ft of horizontal distance). Such steep 

slopes are probably too difficult and expensive to develop for any 

purpose but specialized recreation in the climatic environment of 

Tahoe. Little development within the basin is on land having a slope 

of more than 10 percent, and most development is on land having a 

slope of less than 5 percent. Only about 70 square miles (45,000 acres) 

of land in the basin lies at slopes gentler than 10 percent, and some 

60 square miles of this relatively level land is at the south end of 

the lake in El Dorado County, Calif., between the State line and 

Cascade Lake, and along the lakeshore in Placer County, Calif.

GEOLOGY

Much of the geologic history of the Lake Tahoe basin, described in 

1897 by Waldemar Lindgren, still remains largely hypothetical. Most 

of the early geologic history of the basin must be deduced from findings of regional studies of the entire Sierra Nevada, of which the 

Lake Tahoe basin is only a small part. In these studies, the fossilized 

remains of plants, animals, insects, and marine life have been analyzed 

and related to similar findings from other regions, and the ages of 

minerals have been estimated from the characteristics of their radioactive emissions. All those studies and many others have been considered together, and deductions some weak and some forceful 

have been made. A story encompassing tens of millions of years follows, the story of the rocks of the Lake Tahoe basin.

13
HOW THE BASIN WAS FORMED

For perhaps 200 million years, during the Paleozoic Era, a shallow 

sea lay in a broad valley that existed where the Sierra Nevada and 

the Carson Range now rise. There was a continual very slow movement into the sea of sediment and volcanic material derived from 

high land to the east. The seabed slowly sank during the era so that 

the accumulations formed layers on it. Then near the end of the 

Paleozoic Era, perhaps 250 or 300 million years ago, there was a period 

of gentle deformation of the earth's crust, and the thick layers of sedimentary and volcanic rocks were bent and broken. This period of 

deformation probably lasted for 100 to 150 million years and was 

followed by the Nevadan Revolution, some 150 to 175 million years 

ago. The Nevadan Revolution was a widespread disturbance of the 

crust that raised the area and formed a system of mountain ridges 

somewhat lower than the present Sierra Nevada.

Those ancient ridges were worn down by erosion for 40 to 50 million years and became a relatively low and level plain. Then about 

50 million years ago there began a period of great volcanic activity 

that erupted new rock material into parts of what is now the Lake 

Tahoe region. Between 25 and 40 million years ago another period 

of uplift occurred, and it was probably in that period of geologic 

activity, during the late Tertiary Period of the Cenozoic Era, that 

the Sierra Nevada was tilted upward and the large block of the earth's 

crust now partly occupied by Lake Tahoe was dropped below the 

nearby land surface. From that time onward, the general shape of 

the Sierra Nevada rise, of the Tahoe trough or graben, and of the 

Carson Range has been changed only by widespread uplifting of 

the entire region about 10 million years ago, by erosion, and to a minor 

extent by additional volcanic activity.

Between the periods of major movements of the earth's crust are 

periods in which the forces of erosion tend to wear away the mountains and fill the valleys. We are now living in such a period. The 

landscape is being slowly leveled by many forces but principally by 

the wearing away of material by water and the movement of the 

eroded material along stream channels. The early period of the Lake 

Tahoe basin, after the formation of the valley by the faulting that 

formed the graben, also saw changes wrought by volcanic activity and 

the movement of glaciers. The southern end of the graben is its lowest 

part, and there a lake quickly formed. It was probably much larger 

and deeper than it is now, and its outflow may have been a short 

distance east of the present outlet.

The water flowing from the lake eroded the outlet to an altitude 

corresponding to the present 6,480-foot level rather quickly because 

the obstructing material above that level was unconsolidated and

14
easily moved. Basalt flows, however, emerged from volcanic vents to 

block the outlet, and the lake level rose to about the present 6,600-foot 

level. The water then wore its way through the basalt only to have 

another flow block the outlet again. When the water cut through this 

second flow, the general location of the present outlet was established. 

The glacial or Pleistocene Epoch began about 2 million years ago 

and is followed by the Holocene Epoch, the period of time in which 

we live and the 10,000 or 15,000 years of the immediate past. During 

the Pleistocene there were four periods of glaciation, and the last 

glacial retreat of that epoch began about 25,000 years ago. The movement of vast ice sheets in the Lake Tahoe basin was important in 

forming the landscape we now know. Several times the outlet of 

Lake Tahoe was blocked by ice and the water rose, once to a height 

of about 600 feet above its present level. The gouging by glacial ice 

and the formation of moraines (masses of broken rock fragments and 

soil deposited by the melting of glacier ice and the outflow of melt 

water) formed the troughs now occupied by Emerald Bay, Fallen 

Leaf Lake, Cascade Lake, and many smaller lakes and ponds.

ROCKS AND SOILS OF THE BA SIN

As one would deduce from the foregoing geologic history of the 

Lake Tahoe basin, the rocks that are found near the surface are of 

many types and ages. The folding and overturning that tock place 

many times during the long periods of geologic activity, and the erosion, deposition, and recementing of rock materials that occurred during geologically quiet periods have left a complex arrangement of 

layers. Bedding that was originally horizontal can now be found 

lying at all angles, sometimes completely overturned. Ancient rocks 

overlie much younger formations in some places.

Rocks now exposed in the Lake Tahoe basin are principally igneous 

(that is, formed directly by the cooling of molten material) and metamorphic (formed by the alteration of some earlier type of rock principally by pressure and heat). Areas where the various types of rock 

are found are shown in figure 7.

The metamorphic rocks of Paleozoic age, the oldest exposed rocks 

in the basin, crop out at a few places on the east and west sides of 

the basin, mostly at high altitudes. They are the remains of a much 

larger body that has been intruded by the younger granitic rocks. 

The granitic rocks, principally of Jurassic and Cretaceous age, and 

soil derived from them, make up about half the exposed material in 

the basin. Most of the east side and the southern end of th° basin 

is of granitic origin. Volcanic rocks crop out north and northwest of 

the lake and at the extreme southern end of the basin.

15
FIGURE 7 / ' Types of rocks in the Lake Tahoe basin.

16
EXPLANATION

Contact 

Dashed where appr

Metamorphic rocks I IX

Basin boundary

FIGURE 7 Continued.

Soils generally are derived from adjacent rock outcrops and, if 

undisturbed by other forces, would tend to show the same lines of 

demarcation between types as do the rocks from which tHy were 

formed. However, forces such as gravity, flowing water, wind, or 

glacial ice were active. Regions such as the Lake Tahoe basin that 

have a complex pattern of rock outcrops also possess a compler pattern 

of soil types, and because of soil movement the locations of the soils 

may not bear a close relationship to the location of the parent rock. 

However, in general the soils found at the north end of Lake Tahoe 

are volcanic in nature and soils at the south end are of granitic origin. 

There are structural fractures in the rock, and there is some c'eterioration of the consolidated rock mass from weathering and frcrn penetration by deep-rooted vegetation. Because of this, the contact between 

the soil and the underlying rock is often indistinct. Water c^n penetrate into coarse soil and fragmented rock easily; it also drains rapidly 

from these materials unless there are barriers to its movement. Most 

ground water in the basin is found in valley fills of coarse soil. Soil 

depths in the Lake Tahoe basin range from thin veneers ir the uplands to deposits several feet deep in some bottom lands.

17
Glacial deposits, principally gravel, sand, and silt, occur at many 

places near the lakeshore. The retreat of the ice sheets of the glacial 

epoch has left many rocks and boulders mixed with the gravel and 

silt at the northern end of the basin. The glacial residue is therefore 

rather rough and uneven and is not as attractive for development as 

are some other soils.

Lacustrine deposits, formed under water when the lake surface was 

at a higher altitude, cover the wide valley floor south of the lake. 

Alluvium brought down from the mountains by running vater underlies the principal stream channels and adjacent areas. The alluvium 

and lacustrine deposits are probably the most recently formed surface 

materials and, because of the nature of their origin, form the most level 

and low-lying land surfaces in the basin. These level areas are attractive for roads, streets, and buildings; by far the greatest part of the 

development in the basin is within the regions shown (fig. 7) as lake 

deposits and alluvium.

CLI14 ATE

There is no single classification that can describe the climate of the 

Lake Tahoe basin. One can generalize so far as to state that all regions 

of the basin experience freezing temperatures during the winter and 

most of the precipitation comes during the winter months. Beyond 

this, generalization is difficult.

The climatic factors that dominate in establishing the rature of the 

plant and animal life of a region and that most directly influence 

human activities are temperature and precipitation. The climate of 

the Lake Tahoe basin is influenced by marine air moving inland from 

the Pacific Ocean and by continental airmasses from the interior. 

Figure 8 shows mean monthly temperatures at Tahoe City as well as 

those at Sacramento and San Francisco. The moderating effect of the 

ocean is strongly evident in the San Francisco temperatures, and the 

effect of altitude difference is shown by comparing temperatures at 

Sacramento to those at Tahoe City. Sacramento is less than 100 feet 

above sea level.

Monthly average temperatures tell only part of the story. The range 

between daytime highs and nighttime lows and the temperature extremes experienced during unusually hot or cold periods are important to our comfort and our choice of activities. Data are available for 

lakeside locations in the Lake Tahoe basin, but relatively little is 

known of conditions at higher altitudes. At Tahoe City, these have 

been observed during a 50-year period:

18
Highest temperature. ..... 94°F Lowest temperature. .... 15°F

Mean daily maximum, Mean daily minimum,

January ........ ...... 37°F January .. ........... 17°F

Mean daily maximum, Mean daily minimum,

July .................. 78°F July ..... ........... 43°F

Mean annual temperature... 42.4°F

On the average, temperatures at Tahoe City drop to or below 32°F 

on about 220 days of the year. Temperatures at Glenbrook, on the 

east shore of the lake, are generally 4° or 5° higher than those at 

Tahoe City. At higher altitudes the mean, or average, temperatures 

can be roughly estimated by applying the rule-of-thumb correction of 

a 1° drop for each 300 feet of altitude. The actual temperature at 

various locations at a given altitude varies, of course, with exposure 

to wind and sun, and extreme high and low temperatures ?re both 

likely to be lower at high altitudes.

Precipitation in the Lake Tahoe basin follows the pattern that prevails along the Pacific Coast from San Diego to Seattle; that is, it is 

plentiful in the winter and scanty in the summer. However, the bars 

in figure 8 showing average monthly precipitation indicate that there 

is more precipitation at Tahoe City than at Carson City, Sacramento, 

or San Francisco. This is because most precipitation in the region 

originates with airmasses that move inland during the winter and are 

forced upward by the rising landmass that forms the Sierra Nevada. 

Figure 9 shows lines of equal depth of mean annual precipitation in 

the Lake Tahoe basin. These represent the long-term average and 

often differ greatly from year to year, but the relation between the 

quantity of precipitation and the topography is usually the same. The 

maximum precipitation is at high altitudes in the southwest part of 

the basin. As the air descends into the basin, precipitation becomes 

less until the eastward-moving air is again forced upward by the 

Carson Range.

Most of the precipitation comes during the winter in the form of 

snow. The long-term average annual snowfall reported by the U.S. 

Weather Bureau at Tahoe City is 213 inches. At higher altitudes, 

where precipitation is greater and temperature is lower, snowfall is 

undoubtedly much more than this. Reports of April 1 measurements 

show depths of snow on the ground as great as 89 inches at Tahoe 

City and 244 inches near Echo Lake at an altitude of 8,200 fe~t in the 

southwest part of the basin. February, March, and April snov7 depths 

are usually between 15 and 45 inches at Tahoe City and between 110 

and 190 inches near Echo Lake. On the average, probably at least 

50 percent of the precipitation falls as snow at the lowest altitudes in 

the Tahoe basin, and 90 percent or more does so at altitudes of 8,000 

feet or higher.

19
to

o SAN FRANCISCO SACRAMENTO 

'" AVERAGE MONTHLY 

50 TEMPERATURE. IN 

40 DEGREES FAHRENHEIT 

30 

20 

4 AVERAGE MONTHLY 

3 PRECIPITATION, IN INCH

ONOJFMAMJJAS ONOJFMAMJJAS 

c/5> 

QUJ

Z S

~ UJ

oQ . (D

1 SAN FRANCISCO

\ Coastal

\j \1 t^ ' Rang

DISTANCE FROM PACIFIC OCEAN. IN 

FIGURE 8 ^ Climate and topography from the Pacific 
FIGURE 9 r~; Mean annual precipitation in the Lake Tahoe basin.

Forested regions below 8,000 feet in altitude are generally clear of 

snow by the middle of June, but snow cover may last a few weeks 

longer after unusually wet winters. By mid-August, winter snow is 

gone except for the remains of deep drifts that may have formed in 

sheltered ravines on north-facing slopes. Although some snow may

21
fall on the higher peaks and ridges even during summer months, 

there is no permanent snowpack or icefield in the basin.

Thunderstorms sometimes occur in the basin, most often in the 

mountains. They occasionally cause localized flooding.

Prevailing winds are generally from west to east, but local conditions often give them northwesterly or southwesterly directions, and 

light breezes over the lake itself may blow in any direction. Violent 

winds are infrequent.

Aerial view of Lower Echo Lake, elevation 7,400 feet, on June 24, 1953. Note 

the heavy snow cover on the north-facing slope of the ridge south of the lake. 

Only scattered patches remain on the south slopes of the ridge. U.S. Highway 

50, the main route between Sacramento and South Lake Tahoe, is visible at the 

right.

22
VEGETATION, FISH, 

AND WILDLIFE

Probably 95 percent of the trees in the Tahoe basin consists of conifers, mostly varieties of pine and fir. Most forest cover is at rltitudes 

of less than 9,000 feet, although trees and shrubs can thrive at higher 

altitudes where soil and exposure are favorable. Along much of the 

lake's shoreline there is a belt of gently sloping land that has soil 

and moisture conditions favorable to vegetation. Because of this, the 

lake is surrounded by a belt of pine and fir, interspersed with areas 

of shrubs and open meadows.

There are many hundreds of acres of the low, hardy scrub brush 

of mixed varieties, including manzanita, ceanothus, and scrub oak, 

commonly known collectively as chaparral. Large areas of cHparral 

cover the slopes facing the lake just north of Emerald Bay. Many 

slopes that have been laid bare by slides or fire are bordered by 

chaparral, which can find a foothold rather quickly in soils that are 

relatively inhospitable.

Grasses and other herbage flourish on fairly level open ar°as that 

have a few inches or more of soil, at all altitudes. Their growth 

occurs while moisture is available after snow cover melts, and they 

become brown and brittle and go to seed as soil moisture drop <? below 

the wilting point during the dry summer. Chaparral, which has a 

much deeper root system, remains green throughout the summer. 

There are large areas of grassland south and east of Fallen Leaf Lake. 

In the same region and in other locations where soils and moisture 

supply are favorable there are clumps of deciduous brush and small 

trees. Among the grasses and brush are many flowering plantc that at 

times furnish pleasant scenes of natural beauty amid varied 

surroundings.

Almost all varieties of wildlife found in the Western United States, 

can be seen in the Lake Tahoe basin. Deer, bear, mountain lion, 

coyote, rabbit, raccoon, and a great variety of rodents are common. 

Deer, rabbit, and woodchuck are probably the most frequently hunted 

animals. Land birds and water fowl are plentiful, and almost all common varieties nest in the basin or visit it during migrations.

For a few years before the turn of the century there was corrmercial 

fishing in Lake Tahoe, and the fish population was greatly depleted. 

The nutrient supply of the lake water was too low to encourage a rapid 

revival, so the lake is now stocked with fish, mostly trout from hatcheries, that provide sport fishing. Lake trout, brown trout, and brook 

trout as well as the native cut-throat rainbow trout and whitefish are 

caught. Cut-throat trout weighing as much as 35 pounds have been 

taken from the lake. There are many miles of fishable streams in the 

basin.

23
HISTORY

EXPLORATION AND 

SETTLEMENT

Indians of the Washoe tribe lived in the Lake Tahoe basin long 

before the first forerunners of European civilization reached western 

America. Little is known of their way of life. They maintained 

themselves by hunting and fishing and probably suffered from occasional forays by the Paiutes, who roamed the drier lands to the east. 

The first recorded sight of Lake Tahoe by anyone other than Indians 

was on February 14, 1844, by John C. Fremont. With a party of 39 men 

that included "Kit" Carson, Fremont was on a tour of exploration that 

had left Kansas City more than 8 months earlier. He had visited 

Great Salt Lake and the Columbia River, then had turned southward 

and discovered Pyramid Lake. Perhaps because of stories of a semitropical lake lying on the western slopes of the Sierra 1 Tevada, the 

expedition continued southward and westward, and it was on this 

leg of the journey that the party sighted Lake Tahoe, probably from 

Stevens Peak. They did not visit the lake but continued westward and 

crossed the Sierra through the pass that is now named after Carson. 

Fremont named the lake "Bonpland," in honor of a noted French 

botanist. He believed it to be in the headwaters of the American River.

The name "Bonpland" was never popular or widely used. The first 

official map of the State of California, prepared in 1853, called it Lake 

Bigler, after the third Governor of the State. Bigler was no^ considered 

an attractive name, and ex-Governor Bigler expressed political sympathies that made the name undesirable in 1862, when a new map was 

in preparation. The map compiler was somewhat versed in the local 

Indian vocabulary and proposed renaming the lake "Tahoe," variously 

interpreted as "big water," "high water," or "water in a high place." 

The name was adopted and retained.

Few travelers crossed the Sierra Nevada until the gre^t migration 

that followed the discovery of gold in 1848 about 50 miles west and 

slightly south of the lake, in the South Fork of the American River. 

In 1849, after news of the discovery, a stream of gold seekers began 

a trek to California that soon included adventurers, hopeful farmers, 

and tradesmen and businessmen who sought the freedom and opportunity of a new frontier. All these groups followed the b<°st routes to 

the goldfields and the rich farmlands and settlements farther west. 

To them, the Lake Tahoe region was only a barrier in their route, 

and the easiest journey for most was up the Carson River to its head24
waters and over Carson Pass or Johnson Pass (now Echo Summit), 

9 miles south of the lake. Others followed the Truckee River upstream from Reno and avoided Lake Tahoe and the steep mountains 

rising on its west shore by crossing at Donner Summit, north of 

the lake. Then in 1858, the Comstock lode was discovered 15 miles 

to the east, at Virginia City, Nev., and Lake Tahoe became attractive as a place of opportunity.

The riches in the Lake Tahoe basin were not gold nor silver but 

were timber to supply the needs of the Comstock development. The 

needs were great, for thousands of people were flocking into western 

Nevada and immense profits could be made by supplying lumber for 

the region. The thick forests on the slopes surrounding Lake Tahoe 

were especially attractive, and lumbermen and their followers began 

to settle in the basin. By 1860, the town of Glenbrook was settled, 

and in 1861 a sawmill was established there. The first roads were 

built from the lake to the Carson Valley over Daggett and Soooners 

passes, and flumes were built to float logs cut high on the Carson 

Range down to Carson City.

As lumbering progressed on the eastern side of the basin, the 

supply of large logs began to diminish and cutting began on the 

west side. The logs were floated across the lake to the mills of Glenbrook. All this activity led to the development of other enterprises; 

one of the earliest was the supplying of hay for the large number of 

horses used. Hay was grown in the meadows at the northern end 

of the lake near the outlet into the Truckee River. In 1860 the 125-ton, 

60-foot schooner Iron DuJ^e was put into service to carry hay to the 

south end of the lake. A short-lived mining boom at Squaw Valley, 

Calif., in 1864 brought many people to the northern end of the lake, 

and those who settled near the boat landing founded Tahoe City 

and built two hotels to accommodate visitors and attract tourists. 

Lake Tahoe was becoming a resort, but as a satellite of the Virginia 

City-Comstock lode region.

Those were the years of timber construction and steam povrer, and 

the steam required wood for fuel. The demand for wood continued 

to deplete the forests, but the payrolls and the profits from supplying 

the workers maintained prosperity in the Lake Tahoe basin for 25 

or 30 years. Short logging railroads were built near Glenbrook and 

Incline, Nev., and Bijou, Calif. In 1864 the first steamboat was 

launched on the lake, a 42-foot, 32-ton wood-burning side-wheel 

tugboat. Other steam-powered cargo carriers, tugs, and passenger 

boats served on the lake in the following years. Many of then: carried 

mail and passengers between lakeside communities on a regular 

schedule. Steamboat transportation served Lake Tahoe until 1934, when 

the 169-foot vessel Tahoe made its last scheduled trip.

25
Gradually the momentum of the mining boom slowed and the 

demand for timber lessened. At the same time a few individuals foresaw the possibility of harmful effects from uncontrolled logging, and 

under these influences lumbering activity diminished. The number of 

visitors increased, however, especially after a railroad connection between Tahoe City and the main line at Truckee was opened in 1900.

By 1870 there were resort hotels at Brockway and Carnelian Bay, 

Calif., and Glenbrook, Nev., as well as at Tahoe City. Tahoe City was 

a center of activity after 1900, for it had shipyard and railroad-shop 

facilities in addition to serving as the railroad terminal and the transfer 

point between rail and water facilities.

There was a slow, steady increase in the number of people visiting 

the Lake Tahoe basin for recreation until World War II. After the 

war, two factors brought about an explosive increase in both the temporary and the permanent population of the basin. Splerdid casinos, 

offering popular, sophisticated entertainment as well as gambling 

facilities, were built on the Nevada side of the State line. At the same 

time, widespread financial prosperity and fast, easy autorrobile routes 

put all America on the highway. Lake Tahoe is well known, both 

because of its attractions and because of well-directed efforts to obtain 

publicity. Many tourists from distant States visit the lake on their vacation trips in the West, and the major population centers cf. California 

are now within a 1- or 2-day drive of the lake. The number of people 

visiting Lake Tahoe will no doubt continue to increase. Land developers are successfully persuading visitors to buy land for vacation or 

retirement homes in the basin.

TRENDS IN POPULATION 

AND LANE USE

The permanent homes within the Lake Tahoe basin are almost 

entirely on the low-lying gentle slopes along the lake shore. Estimates 

of the permanent population of the basin at any given time vary 

widely, probably because of varying opinions as to what constitutes 

permanency. However, a reasonable estimate of the year-around resident population of the basin in 1965 is about 26,000. By far the largest 

concentration is in and near the city of South Lake Tahoe, Calif. 

This community was incorporated in November 1965 anc" had a population of about 14,000; about 2,000 more persons lived ir the adjoining community of Stateline, Nev. The shoreline communities along 

State Highway 28 in Placer County, Calif., including Homewood, 

Tahoe City, Carnelian Bay, Brockway, and Kings Beach, had a total 

population in 1965 of about 4,000. Another 4,000 residents lived along

26
the shores of Crystal Bay, in Nevada. The remaining 2,000 lived in 

other parts of Douglas County, Nev., and El Dorado Count;', Calif., 

mostly near the lake. Thus, except for residents in the vicinity of 

Meyers, Calif., 5 or 6 miles south of the lake, only a few hundred of 

the total year-around population lived more than 2 miles from the lake.

The actual number of people within the basin varies greatly from 

season to season, the greatest number coming on summer weekends 

and the smallest number, corresponding closely to the residential population, during midweek periods from November through April. The 

average annual transient population served by the facilities of the basin 

is probably from two to three times the permanent residential population, and during the busiest month (mid-July to mid-August), the 

number of people in the basin may be more than eight t: mes the 

permanent population.

In addition to these periodic variations in basin population, there 

is a strong trend toward an increase in both permanent and temporary 

population. The results of many projections vary, but trends indicate 

that the peak-season population by the year 1990 may be between 

350,000 and 500,000, or at least twice the 1965 peak. The projected yeararound population is from 80,000 to 100,000.

Most recreational activity in the basin is associated with the lake 

and its shores, with the casinos that are just over the interstate boundary in Nevada at the north and south ends of the lake, or with skiing 

facilities. Water sports and recreation are also available at the smaller 

lakes in the basin, especially at Fallen Leaf and Echo Lake?- There 

are campgrounds and hiking trails in the mountains that surround 

the lake, but with the exception of skiers the concentration of people 

visiting the basin is as strongly associated with lakeshore locations 

as is the permanent population.

Thus, from the viewpoint of population distribution and land development, the Lake Tahoe basin can be considered as having two 

rings concentric about the lake: An inner ring rarely more than 2 miles 

wide in which are most of the roads and streets, homes, and businesses 

of the residents and most of the recreational activity; and an outer 

ring of mountainous land, about 240 square miles in are?, that is 

visited by skiers and hikers but otherwise is virtually uninhabited.

The economy of the Lake Tahoe basin, originally based or logging 

and agriculture, shifted its base to tourism and recreation by the turn 

of the century. After World War II, and especially during the past 

decade, the economy of the basin underwent a dramatic boom which 

increased the pressure for conversion of land to the most immediately 

profitable uses. Motels, summer homes, shopping centers, and casinos, 

together with the streets and parking areas needed to serve an almost 

completely automobile-based and largely transient population, were 

quickly built. Such uses are appropriate for land with rather gentle

27
slopes. It is therefore probable that the greatest pressures for land 

development will continue to be in the 70 square miles of relatively 

low and flat land immediately surrounding the lake, while somewhat 

less pressure will exist for development of adjacent higher and slightly 

steeper land.

WATER RESOURCES

HISTORY OF WATEF USE

Water is essential to almost all the activities of man. Aside from 

the obvious needs for household purposes, one probably thinks first 

of the recreational and esthetic uses of the lakes and streams in the 

Lake Tahoe basin. These uses, however, were not the first that measured the importance of Lake Tahoe for the surrounding region. Lake 

Tahoe water flows into the water-hungry semidesert of western Nevada 

and was valued highly for use in irrigation many years before Lake 

Tahoe became well known.

The outflow from Lake Tahoe, augmented by drainage from 

mountain regions to the north and the northeast, forms the Truckee 

River. In California, the Truckee provides water for power generation 

and domestic water supplies. In Nevada, the water is used for municipal supply in the cities of Reno and Sparks and for irrigation in the 

lower Truckee and Carson basins and is important to the economy of 

a large area. Figure 10 shows the entire Truckee River basin from 

its origin south of Lake Tahoe to its terminus in Pyramid Lake, 

Nev., which has no outflow.

During the last hundred years, man's use of water in the Truckee 

River basin has been marred by water-rights disputes involving not 

only the citizens of the area, but also the California and Nevada State 

Governments and the Federal Government. Many of the problems 

have been solved, but the biggest problem of all remains: providing 

enough water for domestic use in California and Nevada and for agriculture in Nevada without causing an excessive drop in the level of 

the lake or harmfully affecting the quality of the water.

The story of large-scale use of water in the Lake Tahoe basin began 

in 1865 when Colonel A. W. Von Schmidt, an engineer from Prussia, 

acquired some land at the Truckee River outlet of the lake and was 

granted the right to build a dam across the river and to appropriate 

500 cfs (cubic feet per second more than 320 million gallons per 

day) of water. By 1870 Von Schmidt had completed a wooden and 

rock dam. In 1871 he announced a bold plan to supply San Francisco 

with water from Lake Tahoe by constructing a tunnel through the

28
120°

40 C

39 C

20 MILES

FIGURE 10 The Truckee River.

Sierra Nevada large enough to accommodate both a railroad line and 

two 6-foot-diameter conduits. The scheme was dismissed as too ambitious and costly; neither the city of San Francisco nor the Central 

Pacific (now the Southern Pacific) railroad was interested.

29
In 1870 the California legislature granted the Donner Lumber and 

Boom Company, a subsidiary of the railroad, exclusive use of the 

Truckee River between Tahoe City and Truckee, as well as the right 

to build a dam at the outlet. However, because of Vor Schmidt's 

prior rights to the outlet, the company could not fully implement 

their plans. Von Schmidt continued to seek acceptance of his idea 

but was unable to muster enough support and eventually control of 

the dam passed to the Donner Company.

In 1903 the Donner Lumber and Boom Company demanded a fee 

from power companies along the Truckee for the privilege of using 

the water. In response to this demand the Fleishhacker family, who 

owned two power plants that served pulp and paper mills ?t Floriston, 

Calif., about 15 miles downriver from Truckee, purchased the "littoral 

rights" to the Truckee River outlet from the Donner Company.

Under the Reclamation Act of 1902 the U.S. Bureau of Reclamation 

of the Department of the Interior initiated a program of supplying 

water from the Truckee River to agricultural lands in Nevada. The 

Bureau planned to construct a new dam at the Lake Tahoe outlet to 

provide greater control over the flow in the Truckee. 1 Tot certain 

that the purchase of "littoral rights" by the Fleishhacker interests was 

legal, the Bureau over a period of years negotiated with both the 

Donner Lumber and Boom Company and the Fleishhaker power company in an attempt to firmly acquire the necessary right?. Its efforts 

were foiled by lakeshore landowners who were opposed to increased 

discharges from the lake that would result in lower lake levels.

In 1908 the Truckee River General Electric Company, predecessor 

of the Sierra Pacific Power Company, purchased all the power plants 

along the Truckee as well as the dam and the adjacent land. The 

terms of the purchase included an agreement by the power company 

to maintain an average flow at Floriston of 500 cfs from March 1 

to September 30 and 400 cfs for the other months. The^e required 

releases became known as the "Floriston Rates." At the time, they 

assured a sufficient supply of water for power generation in California 

and for irrigation in Nevada.

In 1908 the Bureau of Reclamation initiated the Newlands Project, 

named after its principal promoter, Nevada's Senator Francis Newlands. The goal of the project was to supply water for irrigation of 

a large area of land near Fallen, Nev. In 1909 the Bureau was granted 

control of the Lake Tahoe dam and gates by the Truckee River General Electric Company. In the agreement the Floriston Rates were 

reaffirmed, and the Truckee-Carson Irrigation District, created under 

the auspices of the Bureau, was issued the right to appropriate all surplus water of the Truckee River for irrigation in Nevada. In return, 

the Truckee River General Electric Company received trr perpetual 

right to divert the Truckee anywhere along its reach as well as the

30
right to locate its installations on any public lands east of the Truckee 

River watershed. In addition, the Government assumed the responsibility for any damage claims brought against the power company as 

a result of the agreement. The power company also was granted the 

right to construct a diversion channel from Lake Tahoe at any point 

along its shores; however, because of adverse public opinion, this right 

was never exercised.

In 1915 a Federal court decreed that the U.S. Government had the 

right to control discharges from Lake Tahoe. In addition, the decree 

stipulated that the Floriston Rates of flow must be maintained, and 

the water level of the lake must not be allowed to drop below 6,223 

feet above mean sea level.

The Truckee-Carson Irrigation District was granted the right to 

operate the Newlands Project and the Lake Tahoe Reservoir by the 

Bureau of Reclamation in 1926. The Bureau also agreed to abstain 

from additional diversions from the Truckee and Carson Rivers until 

enough water was available to irrigate 87,500 acres at Newlands, Nev.

The water shortage problems created by a severe drought in the 

early 1930's led to the Truckee River Agreement in 1935. Parties to 

the agreement included the Bureau of Reclamation, Truckee-Carson 

Irrigation District, Washoe County Conservation District, and the 

Sierra Pacific Power Company. The States of California and Nevada 

and the Lake Tahoe landowners did not participate in the negotiations. Major provisions of the agreement included:

1. Maintaining the Floriston Rates, except for those periods of low 

lake levels occurring between November 1 and March 31. During this time the new rates were established at 350 cfs for lake 

levels between 6,225.5 and 6,226.0 feet and at 300 cfs for lake 

levels below 6,225.5 feet.

2. Allowing water to be pumped out of the lake for irrigation upon 

the consent of the Secretary of the Interior or upon the consent 

 of the attorneys general of the States of California and Nevada 

if the pumping is for sanitary or domestic purposes.

3. Fixing the low-level elevation of the lake at 6,223.0 feet above sea 

level and the high water level at 6,229.1 feet above sea level.

4. Constructing Boca Reservoir, which has a storage capacity of 40,000 

acre-feet, on the Little Truckee River. Boca Reservoir was completed in 1939.

A Federal court decree of 1944 redefined the irrigation rights in the 

Truckee River basin, affirmed certain water rights of the Pyramid 

Indians, and clarified the rights of the power plants. Reservoir operating procedures were established, so that the Floriston Rates could be 

maintained. Finally, the Truckee River Agreement of 1935 was incorporated into the 1944 decree.

31
Aerial view of the outlet of Lake Tahoe. The dam is below and left of the center 

of the picture, 100 feet or so upstream from the highway bridge over the Truckee 

River. Streets in Tahoe City are near the top of the picture.

32
In 1955 the States of California and Nevada each created interstate 

compact commissions to formulate recommendations for solving water 

and sewage problems in the entire Truckee River basin. The more 

important recommendations made by the commissions for the Lake 

Tahoe basin included the following:

1. Pumpage from the lake should not exceed 34,000 acre-feet per year, 

and return flow from such pumpage should not be transported 

from the basin.

2. Transbasin diversions should not be changed. (There are three 

transbasin diversions from the Lake Tahoe watershed, amounting 

to approximately 5,000 acre-ft annually. The Marlette Lake diversion in Nevada supplies water for domestic use in Virginia City. 

Diverted water from Third Creek, also in Nevada, is used for 

irrigation in Washoe Valley. About 2,000 acre-ft is diverted annually from Echo Lake into the South Fork of the American 

River.)

3. Sewage or sewage effluent should not be discharged directly into 

Lake Tahoe, unless the quality of the discharge is such that it 

will not impair the quality of lake water.

4. Waste effluents should not be exported unless an equal amount of 

water is imported.

Opponents of these recommendations argue that the Lake Tahoe 

basin might be faced with a serious water shortage if annual pumpage 

from the lake were limited to only 34,000 acre-feet.

There is also opposition to the recommendation that the export of 

effluents from the basin be delayed until an equal amount of water 

can be imported, based on the conviction that effluents must be exported immediately to preserve the purity of the lake. With the aid 

of Federal and State funds, the planning and construction of transbasin pipelines for exporting sewage effluent was under way in 1967.

HYDROLOGY

Hydrology is the study of the waters of the earth, their occurrence, 

distribution, and movement. The hydrology of the Lake Tahoe basin 

that will be described here is concerned with the water brought to 

the basin as rain or snow, its movement within the basin, the forces 

that act upon it, and its manner of leaving the basin.

Hydrology is not as yet an exact science. The study of forces and 

factors involved in the behavior of water in the environment includes 

atmospheric physics, hydraulics, chemistry, and biology. The quantities involved are tremendous; a winter storm that brings 2 inches of 

water to the basin in 2 or 3 days as rain or snow carries more than

33
70 million tons of moisture. At the same time the destiny of each 

molecule of water entering the environment is uniquely determined 

by the physical and chemical interactions to which it is exposed. Obviously, we can only generalize about those quantities and forces. The 

random variations that exist in nature from place to place and from 

time to time make precise measurements rather pointless. We can 

only gather records of data that most directly concern us and use that 

information to describe what we consider to be the important characterisics of hydrology.

Data that have been gathered in the Lake Tahoe basin include snow 

depths and water contents, total precipitation (rainfall plus the water 

equivalents of snowfall), evaporation of water from a standard 4-foot 

diameter pan, and temperature. Precipitation, evaporation, and temperature data have been gathered at only a few points, mostly near 

the lake. The most accurately measured data, however, are the outflows 

from the lake into Truckee River. These have been measured since 

1901, and daily as well as annual flows are known to within a few 

percent. Records of the level of water in the lake have also been kept, 

and therefore variations of the amount of water in storage are known.

The tabulation of quantities of inflow of water to a region and of 

the quantities leaving the region and the routes by which they leave 

is called a hydrologic budget. Figure 11 is the estimated annual hydrologic budget of the Lake Tahoe basin. The value shown for average 

annual change in storage is really meaningless because a drop of 

7 inches in lake level during the 66 years would change storage by 

70,000 acre-feet and would be interpreted as an average annual change 

of 1,000 acre-feet. Changes in storage of more than 70,000 acre-feet 

during single years are frequent.

The story of figure 11 is amplified by the information in table 1, 

statistics of the annual hydrologic budget of the Lake Tahoe basin. 

The table shows the mean value (that is, the average of all estimated 

or observed annual events), the median (the value between the highest half and the lowest half of events), the standard deviation (a measure of scatter; for example, about two-thirds of the years had outflow 

of between 52,000 and 290,000 acre-ft, determined by subtracting 

119,000 acre-ft from or adding it to the mean of 171,000 acre-ft), and the 

greatest and smallest estimated or observed annual values. Because of 

the relative ease of measurement, the values of outflow of water from 

the lake are much more accurate than any of the other components 

of the budget. The values of average annual precipitation and water 

loss pertaining to land and water surfaces may be in error by several 

percent. The same is true of the precipitation lines of figure 9 and of 

the component values suggested for individual years in the specific 

instances that are cited in this report; however, because their integrated residual in the form of changes in storage and outflow are

34
Precipitation or land

 672 OOO acre feet

- 139.9 inchesj

^fe -

^%^'^^^v";--.

^-" '-''.,. TRUCKEE R

Dutflow to Truckee River 172000 

feet. iFrom 1901 to 1966 stora 

Lake Tahoe increased by 55.OOO 

feet, thereby net Truckee Rivei

171.OOO acre-feetl

FIGURE 11'-' Estimated annual hydrologic budget of the Lake Tahoe basin.

known rather precisely, the relative magnitudes of the components, 

one to another, cannot be greatly in error.

The annual diversion of 5,000 acre-feet, mentioned in the section, 

"History of Water Use," is from Echo Lake, Marlette Lake, and Third 

Creek. The losses from land of 355,000 acre-feet include evaporation 

from small lakes and streams, in addition to evaporation from moist 

soil surfaces, and from transpiration, the process by which plants 

utilize water. After these losses, probably a little less than half the 

water that falls on the land reaches the lake in the form of streamflow 

or underground seepage. The lake also receives precipitation directly 

on the lake surface. It loses water to the air by evaporation, and the 

residual flows over the dam and through the gates at Tahoe City into 

the Truckee River or is retained to increase the amount of water stored 

in the lake. Losses from the lake by underground flow or seepage are 

probably very small or nonexistent.

35
TABLE 1 ~ Estimated statistics of the anunal hydrologic budget of the Lake Tahoe basin, 1901-66

Component Mean Median Standard Maximum Minimum

deviation

Runoff to lake, after diversion . . . .inches .

Precipitation on lake . .do

Evaporation from lake .do

Net runoff from basin *

. . acre-feet .

Outflow to Truckee River 3

. .do

Range in stage . feet

18.5

20.9

34.6

172, 000

171, 000

2.27

17.0

20.5

35.2

155,000

152,000

1.97

8.0

4.2

3.3

205,000

119,000

.94

41.5

35.0

39.5

767,000

657,000

4.9

4.6

12.8

28.2

2 194, 000

4,700

.8

1 Represents outflow to Truckee River if year-end lake level were always the same.

2 Negative value reflects excess of evaporation from the lake over the sum of inflow and 

precipitation on the lake.

3 Outflow as it actually occurred.

NOTE. 0.3 inch of runoff is diverted from the basin and therefore does not reach the lake. 

Highest lake stage: 6,231.26 ft, July 1907. Lowest lake stage: 6,221.74 ft, December 1934.

As shown in table 1, the components of the hydrologic budget vary 

greatly from year to year. During the wet water year* from October 1, 

1906, to September 30, 1907, inflow to the lake from the land was 

698,000 acre-feet, and precipitation on the lake was 356,000 acre-feet. 

Of this input of 1,054,000 acre-feet, 287,000 acre-feet was lost by 

evaporation, 657,000 acre-feet flowed down the Truckee River, and 

110,000 acre-feet remained in the lake. In contrast, during the dry water 

year 1924, only 78,000 acre-feet reached the lake from the land and 

130,000 acre-feet by direct precipitation; 402,000 acre-feet was lost by 

evaporation and 178,000 acre-feet was released to the Truckee River. 

Because of the low total inflow, storage in the lake was diminished by 

372,000 acre-feet. The extreme changes in lake storage were the decrease just described, in water year 1924, and an increase of 419,000 

acre-feet in water year 1938.

An important aspect of hydrology, in addition to quantity, is timing 

because the growing season is the period when both man and nature 

have the greatest need for water. The Lake Tahoe basin has the same 

seasonal variation in precipitation as does the entire region west of 

the Sierra Nevada; that is, winter precipitation and summer dryness. 

The timing of inflow to Lake Tahoe is also affected by the fact that 

much of the precipitation input to the basin is in the form of snow, 

awaiting release by the melting that occurs in late spring and early 

summer. Thus most of the 212,000 acre-feet average inflow from direct 

precipitation upon the lake comes during the months December to

1 The period October 1 to September 30 of the following year is by convention 

called the water year. It is selected as the period most convenient for hydrologic 

computation.

36
March, while much of the 312,000 acre-feet runoff from the land area 

is often delayed until the months of April to July. These inflows, when 

considered as components of the net input to the storage and discharge 

regimen of the lake, are modified by evaporation from the lake surface. The evaporation loss is relatively small during the damp, cool 

winter months and is greater during the late spring and summer (the 

melt period).

August, September, and October are months of little precipitation, 

negligible snowmelt, and high evaporation. Therefore the 9 remaining 

months can be considered the inflow period and can in turr be separated into the 5-month winter period, November to March, when most 

precipitation arrives but when there is little melting of snow and the 

4-month melt period, April to July, when there is much less precipitation but more snowmelt and evaporation. The variations in timing 

and magnitude of net input to the lake can be demonstrated by data 

from the unusually dry and unusually wet years 1961 and 1965:

1961 net input: Winter period Melt period

Time-_______________ Jan. 24-Mar. 31 Apr. 1-Jure 13

Percent______________ 29 71

Thousand acre-feet _. _ _ 28 70 

1965 net input:

Time. _______________ Dec. 19-Mar. 31 Apr. 1-Aug. 17

Percent________------ 60 40

Thousand acre-feet-. __ 333 226

Net input is the sum of Truckee River outflow plus increase in storage 

in Lake Tahoe. The 1961 melt period was rather short, while in 1965 

a severe storm in December caused both heavy wintertime runoff 

into the lake and a prolonged period of snowmelt. Before and after 

the periods shown, evaporation loss from the lake was generally 

greater than inflow.

The variation of annual precipitation from place to place has been 

discussed in the section "Climate" and is shown by figure 9. Inflow 

to the lake generally varies in location in proportion to the quantity 

of precipitation received by the various contributing streams Inspection of figure 9 shows that the south and west parts of the barm, especially the areas draining towards Emerald Bay and Fallen Leaf Lake, 

receive the most precipitation; that region therefore contributes a large 

part of the inflow. Of the inflow to Lake Tahoe from land areas, 80 

to 90 percent is from California.

The slopes of the Lake Tahoe basin are drained by many streams; 

by far the greatest flow is from three that enter the south end of the 

lake. These are, from east to west, Trout Creek, Upper Truckee River, 

and Taylor Creek. Together they drain about 36 percent of the land 

area of the basin and yield from 40 to 45 percent of the runof*. These 

and other selected basins are shown in figure 12.

37
of the lake contribute an estimated ! J 'v 

average annual flow of 190OO acre .'\ */''\ S^*^

Small unidentified basins and

annual flow of 30 OOO acrefeet

FIGURE 12 ' ' Principal subbasins contributing to Lake Tahoe and their 

estimated average annual flow.

Under natural conditions the streams entering Lake Tahoe carry 

an average of 100 to 250 mg/1 of suspended sediment, as do most 

streams in the Sierra Nevada. This is equivalent to about 0.13 to 0.34 

ton of sediment per acre-foot of inflow, or 40,000 to 100,000 tons per 

year, on the average. Some of the sediment settles in the lake, and the 

Truckee River probably carries away not more than 0.06 to 0.13 ton 

per acre-foot, or 10,000 to 25,000 tons per year. This indicates that 

perhaps 50,000 tons of sediment are deposited in Lake Tahoe each

38
year, enough to reduce the average depth of the lake by 1 foot in 

about 3,200 years. The activities of man in the basin probably increase 

the volume of sediment entering the lake, and some of this material 

is undoubtedly deposited on the lake bottom. However, our knowledge of the quantities involved and of their trends is not complete 

enough to justify an estimate of the long-range effect.

Lake Tahoe water contains some 60 to 70 mg/1 of minerals in solution. Most streams in the area that have been studied contain similar 

concentrations of dissolved solids, so it is reasonable to assume that 

streamflow entering and leaving the lake has the same characteristic; 

studies of Truckee River water show about the same concentrations. 

These values, converted to weights, show that about 30,000 tors of dissolved solids per year on the average enter the lake in streamflow and 

about 17,000 tons leave it. Precipitation and fallout of soluble dust 

from the air can be conservatively estimated to add another 1,000 tons 

per year of dissolved solids, so that the net increase of minerals in Lake 

Tahoe is probably about 14,000 tons per year. If all this material remained in solution, concentration of dissolved solids would increase 

about 10 mg/1 in 100 years; however, there are several physical, chemical, and biological processes that remove solutes from the water, and 

therefore the actual increase in concentration is considerably slower. 

The dissolved solids in both the streams and the lake are in the form 

of ions, mostly bicarbonate, silica, calcium, sodium, sulfate and 

chloride.

In addition to suspended sediment and dissolved minerals, flowing 

water carries organic material derived from the environment through 

which it passes. This material ranges in size from floating tree trunks, 

through decaying leaves and bark, down to particles too small to see. 

If conditions are favorable the organic material eventually decays to 

form gases and adds to the dissolved mineral content of the water. 

The processes and products of decay are important to the biology of a 

stream or lake, and the density and character of aquatic life are dependent upon the physical and chemical characteristics of the water.

Lake Tahoe receives organic material from the streams that feed it. 

Because of the great volume of water in the lake, the incoming water 

remains there a very long time, and the processes of decomposition 

are given the opportunity to operate more completely than in a smaller 

lake. Also, about 40 percent of the water annually entering the lake 

comes as precipitation and is almost completely free of organic material. Moreover, in the past there has been a low supply of nutrients to 

the lake, therefore biological productivity of the lake has been inhibited. For these reasons, under the natural regimen the lake as a 

whole is almost completely free of the disagreeable side effects that 

accompany an overabundant supply of organics, such as objectionable 

odor, taste, or color of the water.

39
LIMNOLOGY

Limnology is the scientific study of bodies of fresh water, with special reference to plant and animal life. In this section Lake Tahoe is 

described as an example of the family of lakes, and its urique characteristics as an individual are examined in terms of laker in general. 

Limnology and hydrology are thoroughly intertwined; therefore, this 

and the preceding section are closely related.

Lakes originate in many ways. Glacial movement sometimes scoops 

out a trough that may fill with water and become a lake; Fallen Leaf 

Lake is an example of such action. Glacial debris, landslides, or volcanic outflows can obstruct valleys and create lakes. The ground surface can subside, either because of the removal of soluble underlying 

rock by water or because of crustal movements of the earth, and provide a basin that will fill until water finds a point of overflow. Lakes 

form in the craters of inactive volcanoes and in the oxbow-shaped 

troughs left behind when a river changes its course. Lake Tahoe has 

been affected by many of these phenomena. As mentioned in the section, "How the Basin Was Formed," the Tahoe valley itself was 

formed by the sinking of a massive block of the earth's crust during a 

period of geological instability. The level of the lake and the location 

of its outflow have been affected by glacial action, by lava flows from 

volcanic vents, and undoubtedly by landslides. Because of the predominating influence of crustal sinking in its formation, Lake Tahoe 

is considered a magnificent example of a graben lake. Many large 

lakes have been formed in this manner, among them the two deepest 

known: Baikal, in Siberia (greatest known depth about 5,700 ft), and 

Tanganyika, in Africa (4,800 ft). Pyramid Lake, into which the 

Truckee River flows, is a graben lake about one-fifth as deep as Lake 

Tahoe.

Although Lake Tahoe is not among the large lakes of the world 

in surface area, it is the 14th largest natural fresh-water lake in the 

United States, excluding the Great Lakes. The combination of area, 

depth, and altitude, together with the relatively small area of contributing basins, creates a unique situation. The great volume of the 

lake, about 122 million acre-feet, results in a relatively slow flushing 

action by the water that flows through. Flushing time, sometimes 

called self-purging time, must be measured on the basis of outflow 

from the lake; water losses by evaporation tend to copTentrate impurities rather than to remove them. The flushing time of Lake Tahoe 

computed thus (dividing volume by annual outflow) is roughly 700 

years; this compares to some 185 years for Lake Superior, having 97 

times the volume of Lake Tahoe; about 10 years for lakes Chelan, 

Wash., Seneca, N.Y., and Sebago, Maine; and 2.6 years for Lake Erie,

40
having more than four times Lake Tahoe's volume. Thus the flushing 

action resulting from the passage of water is much slower in Lake 

Tahoe than in most lakes, and the time of residence of a given mass 

of water, together with all the organic and inorganic material carried 

by the water, is relatively long. This long residence probably has some 

effect upon the dissolved minerals; it can be very important to the 

fate of organic materials, and it allows the settling of a large part of 

the incoming sediment. Because flushing time is dependent upon the 

complete exchange of water in the lake and because it is unlikely that 

all the water involved in vertical mixing processes within the lake 

passes through the inflow-outflow system of the lake at a uniform rate, 

it is probable that the true flushing time for Lake Tahoe is consMerably 

longer than 700 years.

The clarity of water can be measured in several ways. T% e most 

common method that provides a basis for comparison from place to 

place is by noting the depth to which a Secchi disk can be followed. 

Results of this method are subject to a rather wide range of error, however, because of differences among observers, differences in the condition of the water surface, and differences in conditions associated with 

the incoming light at the water surface. The transmission of light 

through water can be measured more objectively by use of a hydrophotometer, a device that is relatively free of such errors. Hydrophotometer readings taken at Lake Tahoe indicate that, in general, 

between depths of about 30 to 500 feet, 90 percent of incoming light 

is extinguished by 120 or 130 feet of water. Hydrophotometer readings 

and Secchi disk readings in other lakes show that the waters of Lake 

Tahoe are among the clearest water found in nature anywhere in the 

world.

Water temperature is an important characteristic of a lake. Its variation from time to time and its role in creating vertical currents are 

very significant in determining the nature of biological activity. Lake 

Tahoe, like most lakes, frequently has three strata or layers of water 

of differing temperature characteristics; the vertical extent of these 

layers varies with weather conditions, especially wind, and with the 

amount of heat added to or removed from the water within the lake. 

The layering fades out of existence as autumn winds and low temperatures cool the surface of the lake, and there may be mixing of water 

within the upper 500 feet or so of the lake because of density currents 

arising from temperature differences and agitation by the wind.

The three layers of water are most clearly defined during late summer and early fall. At that time there is an upper layer of relatively 

warm water, called the epilimnion, in which temperature decreases 

very slowly with depth. The temperature of the epilimnion in Lake 

Tahoe may sometimes slightly exceed 70 °F, and the layer sometimes

41
extends to depths as great as 75 feet. In shallow protected parts of the 

lake, water temperatures may be somewhat higher than the prevailing 

temperature of the epilimnion.

Below the epilimnion, from March or April to November or December, is another layer that varies in vertical thickness as the season advances and sometimes may reach to a depth of 250 feet. This is the 

region in which temperature decreases much more rapidly as depth 

increases, and in a typical late summer period it may exhit ; t a decrease 

in water temperature from 65 °F at a depth of 35 feet to 45 °F at 180 

feet. This zone of rapid temperature change is called the thermocline; 

in shallower lakes the thermocline occupies a much nar-ower range 

of depths and the temperature gradient is necessarily much steeper.

Below Lake Tahoe's thermocline lies another layer, the hypolimnion, in which temperature again changes but slowly with depth. The 

hypolimnion exists as a separate zone only during the summer period 

when temperatures in the epilimnion are markedly higher than those 

at greater depths; thus the upper boundary of the hypolimnion corresponds to the lower boundary of the thermocline, and the mutual 

boundary in Lake Tahoe is very indefinite. The warmest temperatures 

of this deep layer are probably about 50 °F in late summer. Very few 

readings have been made of water temperatures in Lake Tahoe at 

depths greater than 500 feet; the few data that are available indicate 

that, the year around, the temperature of this deep water is very close 

to 39°F, the temperature at which water has its greatest density. Professor C. R. Goldman, of the University of California at Davis, has 

conducted studies that include the collection of data from great depths 

in Lake Tahoe. He concluded (1965, p. 1053) that the lake is "monomictic"; that is, the water is mixed completely to the bottom once each 

year. This conclusion is supported by data of temperature and chemical 

gradients and by the fact that the water is nearly saturated with oxygen 

throughout the depth of the lake.

The oxygen content of the water is another factor in establishing 

the nature of a lake. In general, water in Lake Tahoe contains from 

7 to 11 parts per million of dissolved oxygen, existing as molecules 

intermixed with the molecules of water. This represents a healthy 

condition because there is great capacity for eliminating organic 

impurities; low oxygen content is usually reflected by the presence of 

organic material that is only partially decomposed, a condition resulting in disagreeable color, odor, or taste and in a loss of transparency 

of the water. The dissolved oxygen in Tahoe seems to r?nge from 90 

to 105 percent of saturation throughout the upper 500 feet of the lake 

and varies in concentration chiefly with temperature and depth.

In water containing the relatively low concentrations of dissolved 

solids that are present in Lake Tahoe, biological activity depends 

strongly on the presence of oxygen, the prevalence of favorable tem42
peratures, the clarity of the water which allows light necessary for 

photosynthesis to penetrate, and the availability of nutrients, especially 

nitrate and phosphate. Almost all water, including that of Lake Tahoe, 

contains microscopic organisms called plankton. Plankton includes 

plants, such as algae, and animals, such as protozoa. The plants thrive 

on nitrate and phosphate, and when these substances are present in the 

proper quantity and proportions, algae grow and multiply rapidly, 

sometimes experiencing bursts of growth called "blooms" that produce 

clouds of greenish algae. Under some circumstances, live algae growths 

can cause unpleasant characteristics to appear in water, similar to those 

associated with partially decomposed organic material.

In the normal regimen of a lake, the algae propagate and then die 

at a moderate rate, and the dissolved oxygen contained in the lake 

water is sufficient to support decomposition of the dead algae as well 

as all the other organic material that is continually entering the lake. 

If the volume of algae increases beyond some critical point, however, 

oxygen may be depleted by the decomposition of dead algal cells and 

other organic material in the water. When this occurs, the water may 

become colored by the undecomposed material, and the taste and odor 

of the water may be affected. The entire process that of enrichment 

and the chain of events culminating in increased organic content is 

called eutrophication.

Eutrophication proceeds most rapidly in shallow lakes that receive 

large amounts of plant nutrients. Algae grow most bountifully where 

light is present, and little light reaches the bottom of deep lakes. Lake 

Erie, which is rather shallow and receives nutrients in great volumes, 

has reached a high degree of eutrophication while none of the other 

and deeper Great Lakes shows such advanced signs of enrichment. 

It is likely then that under natural conditions, eutrophication of Lake 

Tahoe would be a long-time process. However, it is possible that the 

phase of eutrophication that is accompanied by the widespread appearance of algal blooms near the surface could be initiated in the near 

future if phosphate and nitrate, found in great quantity in sewage and 

fertilizers, continue to be injected into the lake.

From the preceding description of eutrophication, it is obvious that 

under the natural regimen of Lake Tahoe conditions favcrable to 

small localized algal blooms might exist in some parts of the lake. 

Such blooms do in fact occur and have been observed in shallow, 

sheltered coves where organic material has been deposited and the 

circulation of water from the main body of the lake is restricted. Undoubtedly, such situations arose before man affected the lake. It is 

probable that, regardless of the true extent of change due to the entry 

of man, phenomena such as algal blooms now are more quickly detected and more widely publicized because of the widespread attention 

that has been directed to Lake Tahoe.

43
There has been much study of the eutrophication o^ lakes and 

streams but the process is very complex and involves many chemical 

and biological interactions so there remains much that is unknown. 

Most authorities now believe that accelerated eutrophication might 

begin in Lake Tahoe with the addition of nitrate and phosphate and 

that the phosphorus now in the lake is present in concentrations that 

are almost critical so that an increase in nitrogen could trigger the 

process.

CONTAMINATION

In terms of geologic time, Lake Tahoe, like all lakes, is doomed to a 

short life; however, its life expectancy is much longer than that of most 

other lakes because of its great depth. Lake Tahoe will probably remain as a large body of water long after many other lakes have been 

emptied by geological processes or have become filled with sediment 

to form marshes or solid land. It is possible, however, for man to introduce contamination that can make at least some aspects of the lake 

less pleasing than they have been in the past. The history of our treatment of other lakes and streams gives ample proof that our refuse 

can defile such beauty quickly and easily and that it probably will do 

so unless safeguards of some type are adopted.

Fortunately, in the Lake Tahoe basin, there is little evidence of such 

obvious befouling of the environment as is found in large industrial 

areas the great clouds of smoke from factory chimneys, th^ spreading 

oozing heaps of slag, the windrows of trash that collect at hedges and 

fences, and the floating scum and solids that appear in ponds and 

streams. Probably there never will be smoke clouds or slag heaps in 

the region; there is little likelihood that heavy industry will find the 

basin to be an economical site. There are other and more subtle processes of contamination, however, and these are the threats that are 

feared.

Metropolitan region planners generally consider that on the average 

each person imposes about 120 gallons of sewage and £ pounds of 

rubbish daily on his environment. Sewer lines, treatment facilities, and 

trash collection systems are usually planned to handle such an output. 

In the Tahoe basin, however, much of the population is transient and 

does not use as much water as would the same number of permanent 

residents, and there is little industry. For these reasons the per capita 

use of water in the Tahoe basin can be assumed to be somewhat lower, 

perhaps 90 gallons per day in 1965 and 100 gallons per day by 1990. 

Thus the quantities of refuse and sewage that were produced in 1965 

and may be produced in 1990 in the basin can be summarized by these 

estimates:

44
1965 1990

Period Popula- Sewage, in Rubbish, Popula- Sewage, in Rubbish,

tion ' millions in tons tion l millions in tons

of gallons of gallons

26, 000

53, 000

. . . 170, 000

2.3

4.8

15

1,700

52

110

340

40,000 .

90,000

170,000

420,000

9

17

42

6,200

180

340

840

124,000

1 Middle range of estimates from several sources made during 1960-66.

Obviously, if more than 6 billion gallons of sewage and 120,000 

tons of refuse are to be released into the Lake Tahoe basin each year, 

we must try to determine whether they will harm the environment. 

If they will, we must choose a course of action that will produce the 

least harm.

Both rubbish and sewage are sources of pollution that can adversely 

affect Lake Tahoe. In addition to unsightly remains, they introduce 

minerals and organic substances that may upset the aquatic community that has developed under the natural regimen. Chief among these 

harmful substances are phosphate and nitrate, which are abundant in 

fertilizers; therefore, water that has passed over or percolated through 

fertilized soil adds to the nutrient load that enters the lake. However, 

chemical and biochemical processes within the soil tend to decrease 

the quantity of phosphate and nitrate that are contributed by fertilizers.

Little can be done to reduce the amounts of nutrients that enter 

Lake Tahoe from the undeveloped parts of the basin. It would probably be harmful to stop that contribution even if it were practicable 

to do so; the well-balanced cycle of microscopic life that has existed 

in the lake is necessary to the existence of desirable characteristics. It 

is an overabundance of activity that is to be avoided, and the greatest 

potential for creating such an overabundance is in the proHble increase in sewage.

Most of the sewage from the larger communities in the basin is now 

treated before being released, although overloads and breakdowns of 

equipment have occasionally allowed untreated sewage to enter the 

lake. Before the influx of visitors and residents that began about 1950, 

the amount of sewage entering the lake was not believed to pose a 

serious problem. The only effects of human activity that are clearly 

defined are an occasional increase in coliform organisms in some 

popular beach areas, especially at the south end of the lake, and local 

increases in turbidity when construction activity has introduced sediment into the lake.

Many plans have been proposed for avoiding the contamiration of 

Lake Tahoe by sewage. All plans call for the complete capture and

45
subsequent treatment of all sewage originating within the basin. The 

degree of treatment differs according to the ultimate disposal of the 

effluent as envisioned by each plan. Treatment methods are known 

that, although expensive, will produce an effluent of such high quality 

that it would meet generally accepted standards for drinking water, 

but even then the concentrations of nitrate might be unacceptable as 

inflow to the lake. Distillation of the sewage would leave only pure 

water, of course, but it would be prohibitively expensive.

The plan that seems most practical, and that has been adopted, is to 

treat the sewage thoroughly in order to produce an effluent of drinking-water quality and to pump the effluent through pipelines to streams 

outside the basin. This would involve the export, by 1990, of perhaps 

19,000 acre-feet each year and therefore would require that the outflow 

of the lake be lessened by that amount or that water o^ acceptable 

quality be imported to supply the deficiency. The export destinations 

that are planned are the headwaters of the Carson River, for sewage 

originating at the south end of the lake, and the Truckee River, for 

sewage from the northern region. Sewage from regions along the east 

and west shores of the lake can be routed to one or the other of these 

export systems. The southern export route might require a total pumping lift of well over 1,000 feet, while the northern route would be 

almost level and therefore require much less pumping.

The solution by treatment and export is expensive, but not prohibitively so; local, State and Federal groups are agreed on the need for 

preserving the purity of Lake Tahoe, and there will be cooperation 

from each of these sources. Probably the greatest difficulties to be surmounted are those created by the tangle of conflicting jurisdictions 

and by prejudices. Laws, court decisions, and agreement:: of the past 

have established attitudes concerning water rights that are not always 

in accord with the maximum benefits that can be obtained, while even 

the most complete purification cannot remove from seme peoples' 

minds the stigma sometimes associated with water that has once been 

sewage. The resolution of these difficulties requires sessions of patient 

discussion leading to mutual understanding. Some authorities have 

suggested that the creation of a regional agency with jurisdiction over 

water-associated matters in the area affecting the Tahoe basin may be 

the most practical way to bring this about.

Construction activity of almost every nature can affect the lake adversely. In addition to the introduction of sediment, nutrient transport 

is likely to be accelerated by the disruption of the natural ground cover. 

Here again, cooperation on a regionally uniform basis is necessary. 

It may be that guidelines can determine the nature and location of 

construction and logging activity and perhaps the timing, on the basis 

of optimum use of the lake and its environs.

46
Boaters, too, can introduce undesirable contaminants to the lake. 

Proposals for the reduction of pollution arising from boat use include 

the sealing of sanitary facilities and periodic inspection to insure that 

neither human wastes nor grease and oil leakage can reach the lake.

Rubbish and garbage can be removed from the basin by truck to 

some point of disposal. It is highly probable that, within the r~xt few 

decades, garbage and the solid residue of sewage treatment plants 

can be economically converted to serve as fuel, fertilizer, or raw materials for reprocessing. Until such a time, however, some suitable 

disposal site must be used.

To summarize: Eutrophication is part of the natural evolution of 

a lake. Geologically speaking, lakes are temporary features of the 

landscape. In terms of human history, however, they are long lived 

and can be enjoyed by many generations. If mankind is careless in his 

treatment of a lake, he can speed up eutrophication to the pcmt that 

the desirable characteristics of the lake can be adversely affected within 

decades. In the case of Lake Tahoe, there are indications that rapid 

and unpleasant changes in the lake may be imminent. The cooperative efforts of all those who are associated with the basin of Lake 

Tahoe can prevent this catastrophe. The means of forestalling that 

day are obvious and are within our reach: we have only to stop the 

uncontrolled inflow of everyday waste products into the basir.

MAPS OF THE BASIN

Many road maps of California and Nevada include an enlarged 

insert showing travel routes to and around Lake Tahoe. Much greater 

detail is shown on the topographic maps of the 15- and 7^-minute 

series that are published by the U.S. Geological Survey. The 15-minuteseries quadrangle sheets have a scale of about 1 inch to 1 mil 0. They 

portray landforms by means of altitude contours and also show roads, 

trails, buildings, water features, and political boundaries. Most of the 

basin is also mapped in the 7y2 -minute series at a scale of 1 inch to 

2,000 feet; four of the map sheets of the 7 1/2 -minute series are needed 

to include the area shown on one of the 15-minute-series sheets. Figure 13 shows the names and locations of the maps of the two series 

that include Lake Tahoe and its immediate vicinity.

The lake is also shown on maps of the 1:250,000 series (about 4 miles 

to 1 inch) that are published by the Survey. Lat 39° N. and long 120° 

E. form boundaries for maps of this series; these coordinate? inter47
ii^i_I

+

15-MINUTE QUADRANGLES 7'/2-MINUTE QUADRANGLES

FIGURE 13 < > Index to Geological Survey maps of the Lake Tahoe basin.

sect within the lake; therefore, four map sheets are required to show 

the entire lake and its vicinity. Those four sheets Chico, Sacramento, 

Reno, and Walker Lake portray a region extending more than 200 

miles from east to west and 140 miles from north to soutt, with Lake 

Tahoe at the center.

Chart 5001, issued by the U.S. Coast and Geodetic Survey, is primarily intended as an aid to navigation on Lake Tahoe. The chart is 

published at a scale of 1:40,000 (about 1.58 inches per mile) and includes contours, landmarks, streams, and roads within a distance of 

about 2 miles of the shoreline. The chart shows soundings throughout 

the lake and bears symbols indicating the nature and location of navigational aids and hazards to the boatman.

48
OUTSTANDI1TG

LAKES OF THE

WORLD

Lake Tahoc is well known throughout the Nation because of its 

many attractions. It is considered by many to rank among the world's 

beautiful scenes. To those seeking recreation it offers many choices. 

To the more technically minded, it is interesting because of its geology 

and topography and the extraordinary clarity and depth of the lake 

itself. Because this report may be read by some who have ar interest 

in lakes in general, a list of selected lakes throughout the world is 

presented here.

The first 11 lakes named are the largest in the world in terms of 

surface area. The other lakes have been chosen because one or more 

of their characteristics may be of interest. The list includes the 12 

deepest known lakes in the world, and the lake whose surface is the 

lowest (the Dead Sea). The highest lake in the world is not known; 

however, aeronautical charts indicate that there probably are lakes of 

at least 10 square miles in area at altitudes of more than 19,000 feet on 

the Tibetan plateau.

There is no precise definition to establish how large a body of water 

must be to be called a lake. There are many "ponds" that are larger 

than nearby "lakes," but by usage in most regions, a permarent natural body of water of more than 1 square mile in area is generally 

called a lake.

The surface areas of lakes are generally determined from maps, 

while their depths, and therefore their volumes, must be found by 

soundings. There are many lakes in regions that are not easily accessible and are little known. Advances in aerial mapping have increased 

our knowledge of many remote areas in recent years, and therefore 

such information as the existence of lakes, and sometimes even their 

surface areas and altitudes, in almost unexplored regions are known 

with a remarkable degree of accuracy. Knowledge of depths and volumes is much more uncertain. Little is known of the depths of the 

dozens of very high lakes in the Tibetan plateau, and many lakes in 

southern South America are as yet unsounded. Even in more accessible and familiar regions, soundings may be too few to permit a really 

accurate estimate of the volume of a lake or to insure that the greatest 

depth thus far measured is truly the maximum depth of the lake.

For these reasons, data from even some lakes bearing well-known 

names may be uncertain. Standard reference volumes differ f-om one

49
Lake

Baikal ...........

Nyasa. ...........

Titicaca. ........

IssykKul.........

Salton Sea 2 . ......

Hornindalsvatn. . . . 

TAHOE...........

Lighten 1 ..........

I 

Area 

(sq mi)

168, 000

31, 800

26, 600

24, 000

23, 000

22, 400

13, 100

12, 300

12,200

11,900 

11,600

3,000

2,300

950

850 ..

363

360 

224

215

196 

191 

63

55

50 

40

21

Maximum 

known ' 

depth

(ft)

3,100

1, 300 . .

260 .

220 . .

750 ..

920 . .

4,800

450 .

5,700

2,300 

2,010

920 . .

2,300

35 ..

1,315 ..

45 ..

1, 020 . .

270 . .

1,690 

1,645 

1,940

1,600

220 . 

1,640

1,930

Volume 

Rank, (millions 

by of 

depth acre-ft)

3 64,000

.... 9, 730

... . 2, 660

780

..... 3, 700

... . 4, 650

2 15, 700

1 18,700

4 6, 810 

6 1, 500

5 1,410

...... 30

...... 113

...... 6

...... 73

...... 22

9 98 

10 122 

7 32

12 . . . ....

11 . ........

8 10

Altitude 

of water 

surface 

above or 

below ( ^ 

mean sea 

level 

(ft)

 92

602

3,720

174

581

581

2,535

512

1,490

1,550 

490

12, 600

5,400

4,210

16, 200

-1,330

-232 

1,230

15, 100

174 

6,225 

1,260

1,100

16, 830 

10, 800

6,180

Location

)

U.S.S.R.-Iran

Canada

U.S.S.R. (Asia)

Canada

U.S.S.R. (Asia)

Central Africa

U.S.S.R. (Asia)

Tibet

United States

Switzerland 

Tibet

Norway 

United States

(Celebes)

Ti':et 

U.S.S.R. (Asia)

1 Among the highest lakes of comparable size.

2 The lowest lake of appreciable size in the Western Hemisphere.

3 Outflow is tributary to the Indus River. Lake has long been regarded by Hindus as 

sacred pilgrimage goal.

another in the surface area they ascribe to such familiar lakes as Great 

Slave and Victoria. The lakes that are known as the largest in area, 

in volume, and in depth are so outstanding that it is unlikely that 

further data will displace them from their top rank in those characteristics, but the relative rankings of lakes farther down the list are 

much less certain.

Among the lakes that at times rank with the greatest in area are 

some that fluctuate in size, as the vagaries of climate dictate, and 

vanish or almost vanish during dry periods. Outstanding examples are 

Eyre, in Australia, and Chad, in Africa. Lake Eyre filled in 1950 to cover

50
an area of about 3,400 square miles, but it was completely dry in 1953. 

Lake Chad has varied in area from about 3,800 square miles to almost 

10,000 square miles. Eyre is the sump for a drainage basin of about 

500,000 square miles, much of which has a mean annual rainfall of 

less than 5 inches. Chad, too, is the terminus of flow for an immense 

desert basin.

Lake Sarez, in the Pamir Mountains of central Asia, is of special 

interest because of the way in which it was formed. It is not outstanding in size; in area it is roughly equal to Eagle Lake in California or 

Lake George in New York. It is outstanding, however, in its combination of great altitude and depth 10,800 feet and 1,640 feet, respectively. Lake Sarez was formed by a huge landslide on February 18, 

1911, that dammed the Murgab River to a height of more than 2,400 

feet above the valley floor. The water rose slowly for 23 years and the 

level has been fairly stable since 1934. Outflow is by seepage through 

the dam at about 500 feet below the lake surface.

Lakes in the United States were tabulated and discussed in some 

detail by Bue (1963), and probably the most comprehensive source of 

information relative to lakes throughout the world is Hutchinson 

(1957).

SELECTED 

REFERENCES

Bue, C. D., 1963, Principal lakes of the United States: U.S. Geological 

Survey Circular 476, 22 pages.

Fairbridge, R. W., ed., 1968, Encyclopedia of geomorphology: New 

York, Reinhold Book Corporation, 1295 pages.

Fenneman, N. M., 1931, Physiography of western United States: New 

York, McGraw-Hill Book Co., Inc., 534 pages.

Geological Society of Sacramento, 1968, Geologic studies in the Lake 

Tahoe area, California and Nevada in Evans, J. R., and Matthews, 

R. A., eds., Annual field trip guidebook: Sacramento, California 

Division of Mines and Geology, 99 pages.

Goldman, C. R., 1967, The bad news from Lake Tahoe: Cry California [San Francisco], volume 3, number 1, winter 1967-68, pages 

12-23.

Goldman, C. R., and Carter, R. C., 1965, An investigation by rapid 

carbon-14 bioassay of factors affecting the cultural eutrophication 

of Lake Tahoe, California-Nevada: Journal of the Water Pollution Control Federation, July, pages 1044-1059.

51
Gresswell, R. K., and Huxley, A., 1965, Standard encyclopedia of the 

world's rivers and lakes: New York, Putnam, 384 pages.

Harding, S. T., 1935, Changes in lake levels in Great Basin area: Civil 

Engineering, volume 5, pages 87-90.

Hutchinson, G. E., 1957, A treatise on limnology Volume 1, Geography, physics, and chemistry: New York, John V^iley & Sons, 

Inc., 1014 pages.

James, G. W., 1956, Lake of the sky: Chicago, Charles T. Powner 

Co., 414 pages.

Lake Tahoe Board of Consultants, 1963, Comprehensive study on protection of water resources of Lake Tahoe basin through controlled 

waste disposal: Report for Lake Tahoe Area Council, 157 pages.

Lindgren, Waldemar, 1897, Description of the Truckee quadrangle 

(California): U.S. Geological Survey Geologic Atlas, Folio 39.

Scott, E. B., 1957, The saga of Lake Tahoe: Crystal Bay, Nev., SierraTahoe Publishing Co., 519 pages.

U.S. Geological Survey, 1960, Compilation of records of surface waters 

of the United States through September 1950 Part 10, The Great 

Basin: U.S. Geological Survey Water-Supply Pap°r 1314, 485 

pages.

 1961-66, Water resources data for California Part 1, Surface 

water records, volume 2: U.S. Geological Survey open-file report.

 1963, Compilation of records of surface waters o^ the United 

States, October 1950 to September 1960 Part 10, The Great 

Basin: U.S. Geological Survey Water-Supply Paper 1734, 318 

pages.

1963-65, Water resources data for California Part 2, Water

quality records: U.S. Geological Survey open-file report. 

Welch, P. S., 1952, Limnology [2d ed.]: New York, McGraw-Hill

Book Co., Inc., 538 pages. 

West, A. W., and Mackenthon, K. M., 1966, Report on pollution in

the Lake Tahoe basin: U.S. Department of the Inte-ior, Federal

Water Pollution Control Administration, Cincinnati, Ohio, 38

pages. 

Wilsey, Ham and Blair, 1962, Preliminary regional plan, Lake Tahoe,

1980 regional plan program: San Mateo, Calif., Wilsey, Ham and

Blair (consultants), map and text on one sheet.

52
INDEX

[Italic page numbers indicate major references] 

A

Algal blooms. ........ ....

Alluvium .................

American River. ..........

South Fork.............. 24,33

B

Basalt flows...............

Bears ....................

Bijou, Calif. ..............

Biological activity. ........

Birds ... ...............

Boating, pollution by. .....

Boca Reservoir, Calif. ......

Bonpland ................

Brockway, Calif. ..........

Brockway Summit, Calif. . . .

California gold belt. ..........

Carnelian Bay, Calif....... ...

Carson, Kit..................

Carson City, Nev .... ........

Carson Pass, Calif. . . ........

Carson Range, Calif....... 2,7,

Carson River. .... ..........

Cascade Lake, Calif. ........ 7,

Casinos .......... ..........

Ceanothus .... ..............

Central Pacific (Southern Pacific) railroad. . . . Chaparral ...... ...........

Climate .......... ... ......

Columbia River. . . ..........

Comstock lode, Nevada........

Construction activity, pollution 

by ........ ...

Contamination ..... ... . ...

Coyotes . ...... ......

Crater Lake, Oreg. .....

Crystal Bay, Nev... ....

43

18

?4

24 ' 33

15

23 

25 

42 

23

47 

31

24 

26

7

2 

26

24 

19,25

25

14,19

24,46

13,15

26

23

29

23

18

24 

25

46 

2 44 £*) II

23

4,6

7,7

D

Dagsett Pass Nev

Deer .......................

Dicks Peak, Calif. ............

Donner Lumber and Boom ComTi9 nv

Donner Summit, Calif. .......

E 

Eagle Lake, Calif. ............

Echo Lake, Calif. ....... 19,27, 

Echo Summit, Calif. ..........

Emerald Bay, Calif. ..... 6, 15,

F

Fallen Leaf Lake, Calif. .......

11,15,23,27, 

Fallen, Nev ..................

Fish ........................

Fleishhacker family ...........

Floriston, Nev ................

Floriston Rates ..............

Flushing time, Lake Tahoe and 

other lakes. ......

Freel Peak, Calif. ............

Fremont, John C ..............

G

Geology . .................. OJ

Glacial deposits ...............

Glacial gouging. . . .... ..... 

Glaciers ........ ..........

7 25

49

?3

7

6,39

30

?,5

51

33,35

6,25

23,37 

41

43,47

34

7

37,40 

30

6

?3

??

30

30

30

40

7

74

7?

1ft

15

14

53
Glenbrook, Nev........... 19, 25, 26

Grasses .....................

Great Lakes. .................

Great Salt Lake, Utah.........

Great Slave Lake, Canada...... 5, 50

Ground water, location. .......

H

Hay ... 

History of exploration and 

settlement .......

Homewood, Calif ............

Hydrologic budget, definition. . 

statistics ................

Hydrology, definition..... ....

Hydrophotometer readings.....

Hypolimnion ................

I

Igneous rocks. 

Incline, Nev. . 

Introduction . . 

Irrigation ....

J

Jobs Sister Peak, Calif. 

Johnson Pass, Calif....

K

Kansas City.......

Kings Beach, Calif.

Lacustrine deposits...........

Lake Baikal, U.S.S.R. .......

Lake Bigler, California-Nevada 

Lake Chad, Africa...........

Lake Chelan, Wash..........

Lake Erie.................. 4,40,43

Lake Eyre, Australia..........

Lake George, New York-Vermont ............

Lake Michigan. ..............

Lake Sarez, U.S.S.R. .........

Lake Superior. ............ . . 6,40

76

73

43

74

50

17

25

24

ZD

34

36

33

41

42

15 

25 

1

 )0

7

25

24

ZD

18 

40 

24 

50

40

43

50

51 

6 

51

,40

o

statistics ..............

temperature ...........

Lake Tahoe basin, definition.

o

maps ................

rocks and soils ........

Lake Tanganyika, Afric? . .

Lake Victoria, Africa .......

Lakes, definition ..........

graben ............... O

outstanding .... .....

Limnology, definition ......

C7 J "

Lower Echo Lake, Calif. . . . Luther Pass, Calif. ........

M

Marlette Lake, Nev ........

Metamorphic rocks ........

Meyers, Calif ..............

Mining, boom. ............

Moosehead Lake, Maine. . . Moraines .................

Mount Rose, Nev ..........

Mount Rose Summit, Nev . . . Mountain lions ............

Mountain peaks ...........

Mur gab River ............. O

N 

Newlands, Nev ............

Newlands Project. .........

Nitrate . . ..............

0

Organic material ........... O

Oxveen content. . ........

6

40

37

1 2

24

3

6

7 

37

27

14

47

15

40

50

49

40

49

40

7 

7

23

11,33,35

15

27

25

2

7

6

15

7

7

23

7

51

31

30

14

.. 43,45

39

42

54
Paiute Indians.............. . 24

Pamir Mountains. ..... .... 51

Phosphate ............ . . . . 43,45

Physical geography............ 3

Pine trees............. ...... 23

Plankton .................. . 43

Pollution . . ............... 2,44

Ponds ...................... 7

Population trends and land use. . 26 

Precipitation, amount of snowfall .. ...... 19

data . . ............... 37

thunderstorms ..... .... 22

total .................... 34

Pyramid Indians. ............. 31

Pyramid Lake, Nev ....... 24, 28, 40

R

Rabbits ............. ...... 23

Raccoons .................... 23

Railroad terminal, Tahoe City,

Calif ......... 26

Reclamation Act of 1902...... 30

Recreational activities.... ... 27

Red Lake Peak, Calif.... .... 7

Refuse and sewage, amounts... 44 

Reno, Nev........ ......... 25, 28

Sacramento, Calif. ............ 18

San Diego, Calif.... ..... . 19

San Francisco, Calif. . . ....... 18,29

Scrub oak.................... 23

Seattle, Wash. .... ......... 19

Sebago Lake, Maine... ....... 40

Secchi disk. . ................. 6,41

Sediment, suspended.......... 38

Seneca Lake, N.Y. .......... 40

Sewage, problems.... ....... 33

treatment ......... 46

Shipyard, Tahoe City, Calif. . . 26

Shoreline, length ........... 6

Sierra Nevada... ... .... ... 2,

13,14,19,24,29,36,38

Sierra Pacific Power Company. . 30

Skiing .............. ....... 27,36

Snow, amount. ..... ........ 19

depths .................. 34

water content. . . . .... 34

Soil types.................... 17

South Lake Tahoe, Calif. ..... 26

Sparks, Nev.................. 28

Spooners Pass, Nev........... 25

Spooners Summit, Nev........ 7

Squaw Valley, Calif... ....... 25

Stateline, Nev................ 26

Stevens Peak, Calif............ 7,24

Tahoe City, Calif...... 6,7,18,

Tahoe Meadows, Nev.........

Tahoe trough................

Taylor Creek.................

Temperature, air..............

Thermocline . ..... .........

Third Creek.................

Timber .....................

Tourism ....................

Trout, brook.................

brown ..................

cut-throat . . .............

lake ... ................

Trout Creek.................

Truckee-Carson Irrigation D:strict ............

Truckee River................

25,28,34,36, 

Truckee River Agreement......

Truckee River General Electric 

Company .......

U

Upper Echo Lake, Calif. 

Upper Truckee River .

19,26

7

14

37

19

42

33,35

25

2

23

23

23

23

37

30

6,

38,46

31

30

7

37

Vegetation .................. 23

Virginia City, Nev.......... 2, 25, 33

Volcanic rocks................ 15

Volcanism .................. 14

Von Schmidt, Colonel A. W.... 28

W

Washoe Indians..... 

Washoe Valley, Nev.

24

33

55
Waste disposal............... 1

Water, clarity. ............... 6, 41

purity .................. 6

temperature ............. 41

Water fowl.................. 23

Water resources.......... ... 25,34

Water rights, disputes......... 28

Water sports................. 27

Whitefish .......

Wildlife ........

Winds, prevailing. 

Woodchucks

23

23

22

23

Yellowstone Lake, Wyo.

56

ir U.S. GOVERNMENT PRINTING OFFICT.: 1990 266-037