Lake Tahoe FAQs by David C. Antonucci is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.
Based on a work at beyond the scope of this license may be requested at Contact 

Tahoe FAQs were prepared by David C. Antonucci in cooperation with the UC Davis Tahoe Environmental Research Center.

How did Lake Tahoe form?

About 3 to 3.5 million years ago, a system of north-south trending faults (fractures in the earth’s crust) began moving. The upward movement of the surrounding mountains and the downward fall of the valley bottom along these faults formed a basin that contained an ancestral Lake Tahoe. A much deeper body of water continued to form as the lake bottom fell. Approximately 2.5 million years ago, escaping water eroded through the volcanic edifice forming the existing lake outlet and Truckee River headwaters.

Why is Lake Tahoe called the "Lake of the Sky?"

The water surface of Lake Tahoe sits at an average elevation of 6,225.1 ft or 1.2 miles above sea level. This creates the metaphorical and poetic name, "Lake of the Sky," for a lake that is so high in elevation; it literally and figuratively resides in the heavens. In addition, the name “Lake of the Sky” comes from the many moods of the sky reflected on the surface of the Lake.

How did the name Tahoe originate and what does it mean?

The name Tahoe comes from a mispronunciation of the Washoe Native American name for Lake Tahoe, da ow a ga, which means, “edge of the lake.”

Where is the Tahoe Basin located?

The Tahoe Basin straddles the California-Nevada border. The coordinates of the geographic center of the main body of Lake Tahoe are 39° 06’ 30” N and 120° 01’ 51” W. Lake Tahoe and its watershed spans the montane and subalpine life zones.

How high is the Tahoe Basin?

The surface of the Lake is at an elevation of 6,225 feet above historical sea level. The surrounding mountain peaks vary from 9,000 to nearly 11,000 feet.

How pure is the Lake?

The water is 99.994% pure, making it one of the purest large lakes in the world. For comparison, commercially distilled water is 99.998% pure. Tahoe contains roughly 60 parts per million of dissolved matter.

Why does the Lake appear to have different colors?

As light penetrates the Lake, water molecules absorb various colors. Fine particles and the exceptional clarity allow backscattering of the predominating light color toward the eye of an observer. The lake water appears blue as other colors in the light spectrum are absorbed at deeper depths and the predominant blue light is scattered back toward the observer’s eye. The center of the Lake can appear indigo, as blue light is absorbed further, leaving more visible violet light as the predominant light color. In shallow areas, the water can appear emerald or turquoise in color since green is the predominant light color at shallow depths. In addition, under the right conditions, the Lake surface can reflect the adjacent mountains and the color of the sky.

How clear is the water and why?

Clarity is determined by measuring the water depth at which an 8-inch diameter white disk disappears from view. The Lake owes it extraordinary natural clarity mainly to its exceptional depth and volume, a relatively small watershed and favorable climatological conditions. In 2013, clarity averaged 70.1 feet, far less than the maximum 105 feet of clarity measured in 1968. In the last 10 years, the rate of loss of clarity has decreased due to environmental improvements in the watershed.

How large is the Lake?

The maximum length of the Lake is 21.2 miles (north to south) and the maximum width is 11.9 miles (east to west). The surface area is 191 square miles (122,200 acres). The shoreline length is 75.1 miles and the encircling state highway is 71.8 miles long.

How deep is the Lake?

A maximum depth of 1,645 feet in Crystal Bay makes Tahoe the second deepest lake in the USA, third deepest in North America and 11th deepest in the world. The elevation of Carson City, Nevada is 85 feet higher than the deepest part of Lake Tahoe. If the Willis (formerly Sears) Tower, the tallest building in North America, were dropped into Lake Tahoe at its deepest point, the top would still be submerged by 195 feet of water. The average depth is about 1,000 feet.

How much water is in the Lake?

The Lake holds about 39 trillion gallons of water, enough to cover the state of California to a depth of 14½ inches. A dam at Tahoe City on the Lake’s outlet regulates the upper 6.1 feet of Lake Tahoe above the low water rim. Between the regulated high and low water levels, the volume of water in Tahoe can vary by 243 billion gallons. By volume, Tahoe is the sixth largest lake in the USA.

How old is Lake Tahoe?

Lake Tahoe is over 2-3 million years old. Tahoe is considered an ancient lake and is counted  among the 20 oldest lakes in the world.

How does Lake Tahoe compare to other world lakes?

Tahoe is the second largest lake in the world at or above this elevation. By volume, it is the 31st largest lake overall and the 11th deepest lake in the world.

Where does the water come from?

Rain and snow melt runoff from 63 tributaries in the 312 square-mile watershed adds 65% of the water. Another 35% falls as precipitation directly on the Lake. Typically, 212 billion gallons of water enter the Lake this way each year. In a normal year, Lake Tahoe will rise 15 inches from spring runoff, assuming the outlet gates are closed.

Where does all the water go?

About one-third of the water flows into the Truckee River through the dam at Tahoe City for downstream use with any remaining water flowing 140 miles to the river terminus at Pyramid Lake. The remaining two-thirds of water evaporate from the lake surface at an annual average rate of 0.1 inch per day. The average daily evaporation of water from the lake surface would serve the daily needs of 3.3 million Americans.

What is the weather like?

During the winter months, the average high air temperature is in the mid-40s °F and the average low is in the mid to high-20s °F. In the summer months, the average highs are in the low-80s °F and the lows in the mid to low-50s °F. At least seven months per year, daily maximum temperatures reach the outdoor comfort zone. Sunshine occurs over 75% of the time during daylight hours each year for 273 sunny or partly sunny days. From November through March, 78% of the yearly precipitation occurs, mostly as snowfall. Typically, at lake level in Tahoe City, 15.8 feet of snow falls over winter and accumulates to a maximum snow pack depth of 2.8 feet Summers are very dry and there is less than a 10% chance of getting more than 0.1 inch of precipitation between May 1 and October 15.

How cold is the Lake?

Below an average depth of 900 ft, water temperature is a near constant 41˚F. Over the last 10 years, monthly surface water temperature averaged 41.9˚F at its coldest in February and 65.7˚F at its warmest in August. Daily maximum surface temperature can reach 75˚F. Over the past 38 years, water temperature warmed an average of 1˚F from top to bottom and monthly water surface temperature increased 1.6˚F due to global climate change.

Does the Lake ever freeze?

The main body of Lake Tahoe does not freeze. The stored heat in the Lake’s massive amount of water compared to its relative surface area prevents the Lake from reaching freezing temperature under the prevailing climatic conditions. On rare occasions, Emerald Bay has developed full or partial ice cover and thin ice sheets can form on shallow near shore waters under very cold and calm conditions.

If Tahoe is so pure, why do we see so much attached algae growth on piers and rocks in the near shore?

The appearance of heavy attached algae growths in the nearshore of Lake Tahoe is a fairly recent development that has become highly noticeable since the mid-20th century. The thick mats of green, brown and yellow growths are largely the result of influx of human-caused nutrients from nearby tributaries, storm drains and groundwater. The nutrients are circulated along the shoreline by wind-driven and density currents that bring these nutrients to the stationary algae. The abundant nutrients in combination of readily available sunlight in the shallow water and human-caused warming of the nearshore waters create ideal conditions for attached algae to flourish.

Does pollution endanger Lake Tahoe?

Tahoe has lost about one-third of its world-renowned clarity since 1968. The major component of clarity loss is fine particles, with nearly three-quarters originating from development-impacted watersheds. Another important pollutant is nitrogen, over one-half of which comes from atmospheric fallout created by vehicle exhaust and pollution blown in from surrounding urban areas. A third critical pollutant is phosphorus, with disturbed and natural watersheds contributing two-thirds of the load. All wastewater is treated and exported from the Basin. Lake Tahoe is designated an Outstanding National Resource Water under the Federal Clean Water Act.

How many people are at Lake Tahoe?

Year-round resident population is 66,000. Total population can reach 300,000 on peak days. About three million people visit Lake Tahoe each year. This is comparable to the numbers of visitors to Grand Canyon National Park (3.2 million) and Yellowstone National Park (2.7million).

Important Historical Events

  • Ancestral Native Americans began inhabiting the Tahoe region as far back as 10,000 years ago. The Washoe Tribe occupied the Tahoe Basin for 1,300 years preceding the 20th Century.
  • The first recorded sighting of Lake Tahoe was by Brevet Captain John Fremont and his topographer, Henry Preuss, on February 14, 1844 from Red Lake Peak near present-day Carson Pass.
  • Over a 40-year period in the late 19th Century, loggers clear-cut 95% of the forest to supply lumber for Virginia City, Nevada mines and the transcontinental railroad.
  • In 1861, Mark Twain hiked 12 miles from Carson City to Lake Tahoe in search of a timber claim, camped on the North Shore near present-day Tahoe Vista and accidentally started a wildfire.
  • The 1960 Olympic Winter Games were staged in Squaw Valley and on the West Shore of Lake Tahoe.
  • California and Nevada formed the Tahoe Regional Planning Agency in 1969.

David C. Antonucci is an environmental engineer and 39-year Tahoe resident. He is available for paid professional speaking engagements on Lake Tahoe natural history, Mark Twain at Lake Tahoe and the 1960 Winter Olympics. For more information and booking arrangements, contact him at 530-525-5410 or on the Contact page. Tahoe FAQs were prepared in cooperation with the UC Davis, Tahoe Environmental Research Center.