Clear Lake (California)
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Clear Lake (
Pomo The Pomo are a Indigenous peoples of California, Native American people of California. Historical Pomo territory in Northern California was large, bordered by the West Coast of the United States, Pacific Coast to the west, extending inland to ...
: ''Lypoyomi'') is a natural freshwater lake in Lake County in the U.S. state of
California California () is a U.S. state, state in the Western United States that lies on the West Coast of the United States, Pacific Coast. It borders Oregon to the north, Nevada and Arizona to the east, and shares Mexico–United States border, an ...
, north of Napa County and
San Francisco San Francisco, officially the City and County of San Francisco, is a commercial, Financial District, San Francisco, financial, and Culture of San Francisco, cultural center of Northern California. With a population of 827,526 residents as of ...
. It is the largest natural freshwater lake wholly within the state, with of surface area. (
Lake Tahoe Lake Tahoe (; Washo language, Washo: ''dáʔaw'') is a Fresh water, freshwater lake in the Sierra Nevada of the Western United States, straddling the border between California and Nevada. Lying at above sea level, Lake Tahoe is the largest a ...
is partially in Nevada.) It has an age of nearly 500,000 years. It is the latest lake to occupy a site with a history of lakes stretching back at least 2,500,000 years. Clear Lake supports large populations of
largemouth bass The largemouth bass (''Micropterus nigricans'') is a carnivorous, freshwater fish, freshwater, ray-finned fish in the Centrarchidae (sunfish) family, native to the eastern United States, eastern and central United States, southeastern Canada an ...
,
crappie Crappies () are two species of North American freshwater fish of the genus ''Pomoxis'' in the family Centrarchidae (sunfishes). Both species of crappies are popular game fish among recreational anglers. Etymology The genus name ''Pomoxi ...
,
bluegill The bluegill (''Lepomis macrochirus''), sometimes referred to as "bream", "brim", "sunny", or, in Texas, "copper nose", is a species of North American freshwater fish, native to and commonly found in streams, rivers, lakes, ponds and wetlands ea ...
,
carp The term carp (: carp) is a generic common name for numerous species of freshwater fish from the family (biology), family Cyprinidae, a very large clade of ray-finned fish mostly native to Eurasia. While carp are prized game fish, quarries and a ...
and
catfish Catfish (or catfishes; order (biology), order Siluriformes or Nematognathi) are a diverse group of ray-finned fish. Catfish are common name, named for their prominent barbel (anatomy), barbels, which resemble a cat's whiskers, though not ...
. Two-thirds of the fish caught in Clear Lake are largemouth bass, with a record of . In addition to fish, there is abundant wildlife within the Clear Lake basin. There are year-round populations of ducks, pelicans, grebes, blue herons, egrets, osprey, and bald eagles, and the basin supports sizable populations of deer, bear, mountain lion, raccoon and other animals. The expansive, warm water of Clear Lake makes it popular for
watersports Water sports or aquatic sports are sports activities conducted on waterbodies and can be categorized according to the degree of immersion by the participants. On the water * Boat racing, the use of powerboats to participate in races * Boatin ...
, such as
swimming Swimming is the self-propulsion of a person through water, such as saltwater or freshwater environments, usually for recreation, sport, exercise, or survival. Swimmers achieve locomotion by coordinating limb and body movements to achieve hydrody ...
,
water skiing Water skiing (also waterskiing or water-skiing) is a surface water sport in which an individual is pulled behind a boat or a cable ski installation over a body of water, skimming the surface on one or two skis. The sport requires sufficien ...
,
wakeboarding Wakeboarding is a water sport in which the rider, standing on a wakeboard (a board with foot bindings), is towed behind a motorboat across its wake and especially up off the crest in order to perform aerial maneuvers. A hallmark of wakeboarding ...
,
sailing Sailing employs the wind—acting on sails, wingsails or kites—to propel a craft on the surface of the ''water'' (sailing ship, sailboat, raft, Windsurfing, windsurfer, or Kitesurfing, kitesurfer), on ''ice'' (iceboat) or on ''land'' (Land sa ...
, boat races, and jet skiing.


Nomenclature

''Hok-has-ha'', ''Ka-ba-tin'', and ''Lupiyoma'' are the original names given to Clear Lake by the indigenous people of the region, the
Pomo The Pomo are a Indigenous peoples of California, Native American people of California. Historical Pomo territory in Northern California was large, bordered by the West Coast of the United States, Pacific Coast to the west, extending inland to ...
, Lake Miwok and
Wappo The Wappo (endonym: ''Micewal'') are an Indigenous people of northern California. Their traditional homelands are in Napa Valley, the south shore of Clear Lake, Alexander Valley, and Russian River valley. They are distantly related to the Yu ...
. In the early 19th century,
European American European Americans are Americans of European ancestry. This term includes both people who descend from the first European settlers in the area of the present-day United States and people who descend from more recent European arrivals. Since th ...
settlers referred to the lake as "Big Lake" or "Laguna", before finally adopting Clear Lake by the mid-19th century.


Background and geology

Clear Lake is by at its widest point, with a surface
area Area is the measure of a region's size on a surface. The area of a plane region or ''plane area'' refers to the area of a shape or planar lamina, while '' surface area'' refers to the area of an open surface or the boundary of a three-di ...
of and a capacity. Average depth is , maximum is , lake elevation is , and average water temperature is in winter and in summer. Clear Lake is believed to be one of the oldest lakes in North America. The lake sits on a huge block of stone which slowly tilts northward at the same rate as the lake fills in with
sediment Sediment is a solid material that is transported to a new location where it is deposited. It occurs naturally and, through the processes of weathering and erosion, is broken down and subsequently sediment transport, transported by the action of ...
, thus keeping the water at roughly the same depth. Core samples of the lake's
sediments Sediment is a solid material that is transported to a new location where it is deposited. It occurs naturally and, through the processes of weathering and erosion, is broken down and subsequently sediment transport, transported by the action of ...
, taken by
U.S. Geological Survey The United States Geological Survey (USGS), founded as the Geological Survey, is an agency of the U.S. Department of the Interior whose work spans the disciplines of biology, geography, geology, and hydrology. The agency was founded on March ...
geologists A geologist is a scientist who studies the structure, composition, and history of Earth. Geologists incorporate techniques from physics, chemistry, biology, mathematics, and geography to perform research in the field and the laboratory. Geolog ...
in 1973 and 1980, indicate that the lake is at least 480,000 years old. Some experts feel that
Mono Lake Mono Lake ( ) is a Salt lake, saline soda lake in Mono County, California, formed at least 760,000 years ago as a terminal lake in an endorheic basin. The lack of an outlet causes Hypersaline lake, high levels of salts to accumulate in the lake ...
, to the east of the
Sierra Nevada The Sierra Nevada ( ) is a mountain range in the Western United States, between the Central Valley of California and the Great Basin. The vast majority of the range lies in the state of California, although the Carson Range spur lies primari ...
in California, is older than Clear Lake. However, the sedimentary history of Clear Lake is unbroken, while Mono Lake's sediments have been disturbed by past eruptions of the
Long Valley Caldera Long Valley Caldera is a Depression (geology), depression in eastern California that is adjacent to Mammoth Mountain. The valley is one of the Earth's largest calderas, measuring about long (east-west), wide (north-south), and up to deep. Lo ...
and associated volcanoes. At one time Clear Lake was even bigger than it is now, and included the Blue Lakes (to the northwest of Clear Lake). Volcanic eruptions and subsequent landslides changed the landscape dramatically, forever separating Clear Lake from the Blue Lakes and from its former westward drainage into the Russian River. Clear Lake lies within the Clear Lake Volcanic Field, as designated by the
United States Geological Survey The United States Geological Survey (USGS), founded as the Geological Survey, is an agency of the U.S. Department of the Interior whose work spans the disciplines of biology, geography, geology, and hydrology. The agency was founded on Mar ...
. The volcanic field contains The Geysers, a steam field which powers a network of the world's most productive geothermal power plants. There are numerous small faults present in the south end of the lake as well as many
volcano A volcano is commonly defined as a vent or fissure in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most oft ...
es, ranging in age from 10,000 to 2.1 million years, the largest being Mount Konocti, sitting at the middle of the lake's south shore. There have been no eruptions from the Clear Lake Volcanic Field for thousands of years, but there are indicators currently being monitored that suggest there is the potential for future eruptions. These indicators include volcanic-type earthquakes, hot spring activity and seepage of volcanic gas.


Weather

It is not uncommon for temperatures in the summer to rise into the triple digits, or below freezing in the winter. Occasional summer thunderstorms occur but are not common. Snow can fall to lake level but accumulation is rare. Snow on the surrounding mountains is common. The average high temperature is in summer, and the average low is in winter. Normally, July is the hottest month and December the coldest. December and January are the wettest months, with an average of of rain per month, respectively.


Recreation

With over of shoreline, Clear Lake is a popular spot for water-sports enthusiasts. According to the California Water Board, Clear Lake sees 15,000 recreational boaters per year. There are 11 free boat launch ramps around the lake that are open to the public. Individuals may rent boats and personal watercraft from many businesses around the lake. Clear Lake is sometimes called the "Bass Capital of the West." Largemouth bass, which are farmed and planted in the lake by California Department of Fish and Wildlife, crappie, catfish, bluegill, and
rainbow trout The rainbow trout (''Oncorhynchus mykiss'') is a species of trout native to cold-water tributary, tributaries of the Pacific Ocean in North America and Asia. The steelhead (sometimes called steelhead trout) is an Fish migration#Classification, ...
can be found in the county's lakes.
Fishing boat A fishing vessel is a boat or ship used to catch fish and other valuable nektonic aquatic animals (e.g. shrimps/prawns, krills, coleoids, etc.) in the sea, lake or river. Humans have used different kinds of surface vessels in commercial, arti ...
s can be rented, and many stores and facilities around the lake specialize in fishing equipment. Numerous fishing tournaments and derbies are held throughout the year. In 2016, Clear Lake was ranked by ''Bassmaster Magazine'' as the #3 best bass lake in the United States and the #1 best bass lake on the West Coast. All boaters entering Lake County are warned that Dreissenid mussels, also known as
quagga The quagga ( or ) (''Equus quagga quagga'') is an extinct subspecies of the plains zebra that was endemic to South Africa until it was hunted to extinction in the late 19th century. It was long thought to be a distinct species, but mtDNA ...
and
zebra mussel The zebra mussel (''Dreissena polymorpha'') is a small freshwater mussel, an Aquatic animal, aquatic bivalve mollusk in the family Dreissenidae. The species originates from the lakes of southern Russia and Ukraine, but has been accidentally Intro ...
s, are a great threat to Clear Lake. By law, boats are required to be inspected before launching, and must have a Lake County Quagga/Zebra (QZ) Sticker on the watercraft. Shops in the vicinity carry out the inspection. At every entry to Lake County, signs warn boaters not to spread
hydrilla ''Hydrilla'' (waterthyme) is a genus of aquatic plant, usually treated as containing just one species, ''Hydrilla verticillata'', though some botanists divide it into several species. It is native to the cool and warm waters of the Old World in A ...
in the county's bodies of water. Extensive management efforts have controlled the presence of hydrilla in Clear Lake, although it may return at any time. The lake is also the site of an annual "splash-in", the "oldest and largest seaplane gathering in the Western United States". The
California Office of Environmental Health Hazard Assessment The Office of Environmental Health Hazard Assessment, commonly referred to as OEHHA (pronounced oh-EEE-ha), is a specialized department within the cabinet-level California Environmental Protection Agency (CalEPA) with responsibility for evaluati ...
released an advisory statement regarding eating fish caught from the lake, based on the mercury level.


Wildlife and vegetation

The Clear Lake basin attracts large quantities of waterfowl, including
mallard The mallard () or wild duck (''Anas platyrhynchos'') is a dabbling duck that breeds throughout the temperate and subtropical Americas, Eurasia, and North Africa. It has been introduced to New Zealand, Australia, Peru, Brazil, Uruguay, Arge ...
s, western grebe,
coot Coots are medium-sized water birds that are members of the rail family, Rallidae. They constitute the genus ''Fulica'', the name being the Latin term for "coot". Coots have predominantly black plumage, and—unlike many rails—they are usual ...
s, various species of
geese A goose (: geese) is a bird of any of several waterfowl species in the family Anatidae. This group comprises the genera '' Anser'' (grey geese and white geese) and ''Branta'' (black geese). Some members of the Tadorninae subfamily (e.g., Egyp ...
,
osprey The osprey (; ''Pandion haliaetus''), historically known as sea hawk, river hawk, and fish hawk, is a diurnal, fish-eating bird of prey with a cosmopolitan range. It is a large raptor, reaching more than in length and a wingspan of . It ...
s,
plover Plovers ( , ) are members of a widely distributed group of wader, wading birds of subfamily Charadriinae. The term "plover" applies to all the members of the subfamily, though only about half of them include it in their name. Species lis ...
s,
mergansers ''Mergus'' is the genus of the typical mergansers ( ) fish-eating ducks in the subfamily Anatinae. The genus name is a Latin word used by Pliny the Elder and other Ancient Rome, Roman authors to refer to an unspecified waterbird. The common mer ...
and many others.
Wild turkey The wild turkey (''Meleagris gallopavo'') is an upland game bird native to North America, one of two extant species of Turkey (bird), turkey and the heaviest member of the order Galliformes. It is the ancestor to the domestic turkey (''M. g. dom ...
s, blacktail deer, gray squirrels,
ground squirrel Ground squirrels are rodents of the squirrel family (Sciuridae) that generally live on the ground or in burrows, rather than in trees like the tree squirrels. The term is most often used for the medium-sized ground squirrels, as the larger ones ar ...
s,
skunk Skunks are mammals in the family Mephitidae. They are known for their ability to spray a liquid with a strong, unpleasant scent from their anal glands. Different species of skunk vary in appearance from black-and-white to brown, cream or gi ...
s, river otter,
raccoon The raccoon ( or , ''Procyon lotor''), sometimes called the North American, northern or common raccoon (also spelled racoon) to distinguish it from Procyonina, other species of raccoon, is a mammal native to North America. It is the largest ...
,
mink Mink are dark-colored, semiaquatic, carnivorous mammals of the genera ''Neogale'' and '' Mustela'' and part of the family Mustelidae, which also includes weasels, otters, and ferrets. There are two extant species referred to as "mink": the A ...
, and
muskrat The muskrat or common muskrat (''Ondatra zibethicus'') is a medium-sized semiaquatic rodent native to North America and an introduced species in parts of Europe, Asia, and South America. The muskrat is found in wetlands over various climates ...
. There have been occasional sightings of
mountain lion The cougar (''Puma concolor'') (, ''Help:Pronunciation respelling key, KOO-gər''), also called puma, mountain lion, catamount and panther is a large small cat native to the Americas. It inhabits North America, North, Central America, Cent ...
and ringtail.
Opossum Opossums () are members of the marsupial order Didelphimorphia () endemic to the Americas. The largest order of marsupials in the Western Hemisphere, it comprises 126 species in 18 genera. Opossums originated in South America and entered North A ...
s,
red-tailed hawk The red-tailed hawk (''Buteo jamaicensis'') is a bird of prey that breeds throughout most of North America, from the interior of Alaska and northern Canada to as far south as Panama and the West Indies. It is one of the most common members of ...
s,
turkey vulture The turkey vulture (''Cathartes aura'') is the most widespread of the New World vultures. One of three species in the genus '' Cathartes'' of the family Cathartidae, the turkey vulture ranges from southern Canada to the southernmost tip of Sou ...
s, and other species are also common. The endangered
northern spotted owl The northern spotted owl (''Strix occidentalis caurina'') is one of three spotted owl subspecies. A western North American bird in the family Strigidae, genus ''Strix (genus), Strix'', it is a medium-sized dark brown owl native to the Pacific N ...
is seen occasionally. Common reptiles and amphibians include the northwestern pond turtle, California king snake, Pacific gopher snake,
garter snake Garter snake is the common name for small to medium-sized snakes belonging to the genus ''Thamnophis'' in the Family (biology), family Colubridae. They are native to North America, North and Central America, ranging from central Canada in the no ...
s, northern pacific rattlesnake, common bullfrog and the rare California giant salamander among many others. Much of the shoreline is developed, but parks, reserves, miles of open water and private land also exist allowing many opportunities for observing and enjoying nature. The county also hosts a growing population of the rare
tule elk The tule elk (''Cervus canadensis nannodes'') is a subspecies of elk found only in California, ranging from the grasslands and marshlands of the Central Valley to the grassy hills on the coast. The subspecies name derives from the tule (), ...
, recently reintroduced after being locally hunted to extinction one hundred years before. A large colony of
bald eagle The bald eagle (''Haliaeetus leucocephalus'') is a bird of prey found in North America. A sea eagle, it has two known subspecies and forms a species pair with the white-tailed eagle (''Haliaeetus albicilla''), which occupies the same niche ...
s is found in the Cache Creek canyon. In addition to the native Clear Lake hitch (called ''chi'' by the native Pomo), the lake hosts
channel catfish The channel catfish (''Ictalurus punctatus''), known informally as the "channel cat", is a species of catfish native to North America. They are North America's most abundant catfish species, and the official state fish of Kansas, Missouri, Nebra ...
, white catfish, brown bullhead, crappie (both black and white species), and other native fish species, as well as Florida strain largemouth bass and
carp The term carp (: carp) is a generic common name for numerous species of freshwater fish from the family (biology), family Cyprinidae, a very large clade of ray-finned fish mostly native to Eurasia. While carp are prized game fish, quarries and a ...
placed by the Department of Fish and Wildlife for sporting purposes. Along the shoreline and creeks, there are aquatic growths of tule,
cattail ''Typha'' is a genus of about 30 species of monocotyledonous flowering plants in the family Typhaceae. These plants have a variety of common names, in British English as bulrushStreeter D, Hart-Davies C, Hardcastle A, Cole F, Harper L. 2009. ...
,
willow Willows, also called sallows and osiers, of the genus ''Salix'', comprise around 350 species (plus numerous hybrids) of typically deciduous trees and shrubs, found primarily on moist soils in cold and temperate regions. Most species are known ...
, cottonwood,
box elder ''Acer negundo'', also known as the box elder, boxelder maple, Manitoba maple or ash-leaved maple, is a species of maple native to North America from Canada to Honduras. It is a fast-growing, short-lived tree with opposite, ash-like compound l ...
, and many other types of riparian plant life. The streams feeding Clear lake contain Sacramento pikeminnow,
California roach The California roach (previously ''Lavinia/Hesperoleucus symmetricus'') is a species of freshwater Actinopterygii, ray-finned fish belonging to the Family (biology), family Leuciscidae, which includes the daces, chubs, Phoxinus, Eurasian minnows ...
, and rainbow trout. Pacific lamprey are present in at least one stream, Kelsey Creek. Prior to the construction of a dam on the outlet of Clear Lake, both
steelhead Steelhead, or occasionally steelhead trout, is the Fish migration#Classification, anadromous form of the coastal rainbow trout or Columbia River redband trout (''O. m. gairdneri'', also called redband steelhead). Steelhead are native to cold-wa ...
and Pacific lamprey ascended Cache creek to spawn in Clear Lake's tributaries. As of March 2024, farming operations along the Big Valley Groundwater Basin watershed have been ordered to report of their water use by the
California State Water Resources Control Board The California State Water Resources Control Board (SWRCB) is one of six branches of the California Environmental Protection Agency. History This regulatory program has had the status of an official government department since the 1950s. The ...
in order to study the effect of groundwater pumping and water diversions on the Clear Lake hitch spawning and migration. Clear Lake is well known among
entomologists Entomology (from Ancient Greek ἔντομον (''éntomon''), meaning "insect", and -logy from λόγος (''lógos''), meaning "study") is the branch of zoology that focuses on insects. Those who study entomology are known as entomologists. In ...
for the Clear Lake
gnat GNAT is a free-software compiler for the Ada programming language which forms part of the GNU Compiler Collection (GCC). It supports all versions of the language, i.e. Ada 2012, Ada 2005, Ada 95 and Ada 83. Originally its ...
('' Chaoborus astictopus'') and historical control efforts. This
species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...
of "phantom midge" (so called because the larvae are transparent and very difficult to see) measures less than long and resembles a tiny
mosquito Mosquitoes, the Culicidae, are a Family (biology), family of small Diptera, flies consisting of 3,600 species. The word ''mosquito'' (formed by ''Musca (fly), mosca'' and diminutive ''-ito'') is Spanish and Portuguese for ''little fly''. Mos ...
, but is non-biting. Clear Lake gnat hatches start anytime from March through June, depending on weather. Before pesticide use began in the 1940s, the gnat was so abundant around the lake in the summer that large piles of dead gnats appeared beneath streetlights, looking like dirty snow. The gnat swarms were so thick that people driving along the edge of the lake reported stopping every to clean the insects off the windshields and headlights of their cars so they could see, and pedestrians tied kerchiefs over their faces to avoid inhaling the gnats. The rugged coastal mountains surrounding Clear Lake are covered with thick stands of oak-madrone forest, manzanita, sage shrubs,
chaparral Chaparral ( ) is a shrubland plant plant community, community found primarily in California, southern Oregon, and northern Baja California. It is shaped by a Mediterranean climate (mild wet winters and hot dry summers) and infrequent, high-intens ...
, and grasses. Most common trees include blue oak, valley oak, interior live oak, Pacific madrone, California scrub oak, plus very occasional coast redwoods and
tanoak ''Notholithocarpus densiflorus'', commonly known as the tanoak or tanbark-oak, is a broadleaf tree in the family Fagaceae, and the type species of the genus ''Notholithocarpus''. It is a hardwood tree that is native to the far western United Sta ...
. Large stands of western white pine may be seen in the higher elevations. The heavy forestation and ruggedness of this part of California has helped prevent wholesale real estate development or farming. On the northeast slope of Mount Konocti is a heavily forested area known locally as the "Black Forest" because it never gets direct sunshine. This area has some
Douglas fir The Douglas fir (''Pseudotsuga menziesii'') is an evergreen conifer species in the pine family, Pinaceae. It is the tallest tree in the Pinaceae family. It is native to western North America and is also known as Douglas-fir, Douglas spruce, Or ...
in very heavy stands.


History

Archaeologists believe that the Clear Lake basin has been occupied by Native Americans for at least 11,000 years. (See: Post Pattern.) Evidence of this has been found at nearby Borax Lake and on Rattlesnake Island in the lake's south arm. Abundant fish, game and waterbirds made Clear Lake an oasis in the otherwise harsh conditions of Northern California's mountains. The native Clear Lake Hitch (''Lavinia exilicauda'') was once so abundant that millions of hitch clogged the lake's feeder streams in dry months. When the Spanish missionaries came to California, they found that thousands of Native Americans lived in the Clear Lake Basin, primarily
Pomo The Pomo are a Indigenous peoples of California, Native American people of California. Historical Pomo territory in Northern California was large, bordered by the West Coast of the United States, Pacific Coast to the west, extending inland to ...
, Yuki, and
Wappo The Wappo (endonym: ''Micewal'') are an Indigenous people of northern California. Their traditional homelands are in Napa Valley, the south shore of Clear Lake, Alexander Valley, and Russian River valley. They are distantly related to the Yu ...
with some Lake Miwok. European settlers arrived starting around 1845. Frequently they abused and exploited the native
Pomo people The Pomo are a Indigenous peoples of California, Native American people of California. Historical Pomo territory in Northern California was large, bordered by the West Coast of the United States, Pacific Coast to the west, extending inland to ...
. A number of Pomo were enslaved and abused by settlers, notably Andrew Kelsey (whose name is attached to the town of Kelseyville) and Charles Stone. The Pomo eventually revolted and killed Kelsey and Stone in 1849. The following year, a
United States Army The United States Army (USA) is the primary Land warfare, land service branch of the United States Department of Defense. It is designated as the Army of the United States in the United States Constitution.Article II, section 2, clause 1 of th ...
contingent under Lieutenant
Nathaniel Lyon Nathaniel Lyon (July 14, 1818 – August 10, 1861) was a United States Army officer who was the first Union Army, Union General officer, general to be killed in the American Civil War. He is noted for his actions in Missouri in 1861, at the beginn ...
cornered as many as 200 Pomo on an island in Clear Lake and slaughtered most of them—including scores of women and children. The historical marker for the Bloody Island massacre is on Highway 20 between Upper Lake and the Robinson Rancheria. The Pomo were later forced to live in small rancherias set aside by the federal government. Clear Lake was one of the potential water supplies considered in the 1870s by the city of
San Francisco San Francisco, officially the City and County of San Francisco, is a commercial, Financial District, San Francisco, financial, and Culture of San Francisco, cultural center of Northern California. With a population of 827,526 residents as of ...
, along with Blue Lakes in Alpine County, Lake Merced, Calaveras Valley, Spring Valley Water Works, and
Pescadero Creek Pescadero Creek is a major stream in Santa Cruz County, California, Santa Cruz and San Mateo County, California, San Mateo counties in California, United States. At ,U.S. Geological Survey. National Hydrography Dataset high-resolution flowline d ...
. The Clear Lake Water Works Company would have built a dam at the current location of the existing one, and piped water through a system of tunnels, canals and reservoirs to the
San Pablo Bay San Pablo Bay is a tidal estuary that forms the northern extension of the San Francisco Bay in the East Bay and North Bay regions of the San Francisco Bay Area in northern California. Most of the Bay is shallow; however, there is a deep wate ...
. The surveyors reported that the lake's "water has a
peat Peat is an accumulation of partially Decomposition, decayed vegetation or organic matter. It is unique to natural areas called peatlands, bogs, mires, Moorland, moors, or muskegs. ''Sphagnum'' moss, also called peat moss, is one of the most ...
y and rather unpleasant flavor", and that "the condition of the water differed in the upper and lower portions of the lake", noting "dead fish floating here and there". Clear Lake was used as an outlying seaplane base for Alameda Naval Air Station during
World War II World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...
and the early years of the
Cold War The Cold War was a period of global Geopolitics, geopolitical rivalry between the United States (US) and the Soviet Union (USSR) and their respective allies, the capitalist Western Bloc and communist Eastern Bloc, which lasted from 1947 unt ...
.
Flying boat A flying boat is a type of seaplane with a hull, allowing it to land on water. It differs from a floatplane in having a fuselage that is purpose-designed for flotation, while floatplanes rely on fuselage-mounted floats for buoyancy. Though ...
s could land on Clear Lake when conditions were unsafe on
San Francisco Bay San Francisco Bay (Chochenyo language, Chochenyo: 'ommu) is a large tidal estuary in the United States, U.S. state of California, and gives its name to the San Francisco Bay Area. It is dominated by the cities of San Francisco, California, San ...
. In 1977, Proteus Inc, a Berkeley-based company that would eventually become Earthrise Nutritionals, contacted the Clear Lake Algae Research Unit (CLARU), an initiative resulting from the collaboration of the county's Flood Control and Water Conservation District and the
California Department of Water Resources The California Department of Water Resources (DWR) is part of the California Natural Resources Agency and is responsible for the management and regulation of the State of California's water usage. The department was created in 1956 by Governor ...
. The company expressed interest in the "possibility of harvesting the county's algae for sale in specialty markets in Europe and Japan". The project didn't materialize, as harvesting spirulina, the
cyanobacteria Cyanobacteria ( ) are a group of autotrophic gram-negative bacteria that can obtain biological energy via oxygenic photosynthesis. The name "cyanobacteria" () refers to their bluish green (cyan) color, which forms the basis of cyanobacteri ...
genus Genus (; : genera ) is a taxonomic rank above species and below family (taxonomy), family as used in the biological classification of extant taxon, living and fossil organisms as well as Virus classification#ICTV classification, viruses. In bino ...
the company was interested in, didn't prove economical nor reliable. The company opted instead for algae farming. The Clear Lake Algae Research Unit was disbanded in October 1978 for lack of funding, eight years after its start.


Hydrology and water rights

The Clear Lake Watershed is contained within the Upper Cache Creek USGS hydrologic unit, an area that encompasses . The
drainage basin A drainage basin is an area of land in which all flowing surface water converges to a single point, such as a river mouth, or flows into another body of water, such as a lake or ocean. A basin is separated from adjacent basins by a perimeter, ...
is ( including the lake), which is large compared to the lake's . The surface area of the lake is divided into three arms: the Upper Arm, the Oaks Arm and the Lower Arm. Cache Creek, the only outlet for the lake, originates from the Lower Arm. Cache Creek has two major tributaries: North Fork Cache Creek and Bear Creek. The Upper Arm is the largest of the three arms and receives 75% of drainage from the watershed. Rodman Slough, contained within the Upper Arm, receives drainage to its marsh from Scotts Creek and Middle Creek, the largest tributaries to Clear Lake as well as Kelsey Creek, which enters from Big Valley. Erosion and sedimentation are key environmental concerns in the Clear Lake region. Seventy percent of the terrain has very shallow topsoil, which saturates after a rainfall of , after which runoff flows quickly into the lake. The maximum flow from the lake is determined by the narrow canyon of Cache Creek, not by the dam. The combination of rapid inflow and slow outflow results in frequent flooding of low-elevation areas such as downtown Clearlake and Lakeport. DeWitt Clinton Rumsey, previously a
cattle drive Droving is the practice of walking livestock over long distances. It is a type of herding, often associated with cattle, in which case it is a cattle drive (particularly in the US). Droving stock to market—usually on foot and often with the ...
"Captain" (and after whom the town of Rumsey in Yolo County was named), was one of the first to record the water levels of Clear Lake. Its level was originally controlled by a rocky ledge in Cache Creek called the "Grigsby Riffle" (which is now submerged upstream of the 1914 dam). In 1872 Rumsey installed a gauge in Lakeport to record the water level. He defined the level when the lake ceased to flow over the ledge as "zero feet Rumsey," which corresponds to an elevation of . The reading is referred to as being "on the Rumsey Gauge" or "(x) feet Rumsey," which can fall below zero due to evaporation (over a year) and pumping of water. The highest recorded level is ( in 1890, and the lowest is in 1920. In 1991 a court ruled that the official low water mark (which determines property ownership) is zero feet Rumsey. The Rumsey gauge, now automated, is still in operation. Yolo County acquired riparian rights to Cache Creek's water in 1855, and after gaining water storage rights in 1912 they built the Cache Creek dam. Water companies which rely on the lake have to pay Yolo County for their water. The Gopcevic (1920) and Bemmerly (1942) Decrees prohibited the modification of the Grigsby Riffle, set the normal maximum level of Rumsey, and required Yolo to keep the level below except for limited times during floods. Yolo was entitled to use all the water down to zero feet. The Solano Decree (1978,1995) limited the amount of water Yolo could use: if the lake is "full" on May 1—at Rumsey—then they can draw 150,000 acre-feet, equivalent to a drop in the lake level of about . If the level on May 1 is below they can draw none, with a proportional amount for other levels. They must stop on October 31, or if the level falls to . In compensation, the Indian Valley Reservoir, also entirely in Lake County, was constructed in 1975, and is under the full control of Yolo County. The northern end of Clear Lake adjacent to Rodman Slough and Middle Creek was blocked off with levees between 1900 and 1940, and the land was reclaimed for agricultural use. During the summer months, Clear Lake provides irrigation flows for agricultural operations in Yolo County. Management of the lakebed is provided by the County of Lake, in accordance with authorities granted by the State Lands Commission in 1973. A project is currently under way to breach the levees and restore of lake and wetland. Bloody Island will again be an island. The additional water resulting from the increased lake area will be allocated to municipal districts drawing water from the lake. Yolo's water allowance under the Solano Decree may also be increased. The management of the lake level is thus designed to avoid flooding, provide water to Yolo County and local water companies, and maintain enough water for recreational use. Sewage from many Lake County towns no longer flows into the lake; instead, it is pumped to The Geysers geothermal plant. On September 15, 2014, the lake level fell to on the Rumsey gauge, the lowest level since the 1977 drought. When full, the lake level measures .


Environmental issues


Agriculture and wetlands

The Clear Lake Watershed contains both
freshwater Fresh water or freshwater is any naturally occurring liquid or frozen water containing low concentrations of dissolved salts and other total dissolved solids. The term excludes seawater and brackish water, but it does include non-salty mi ...
marsh In ecology, a marsh is a wetland that is dominated by herbaceous plants rather than by woody plants.Keddy, P.A. 2010. Wetland Ecology: Principles and Conservation (2nd edition). Cambridge University Press, Cambridge, UK. 497 p More in genera ...
es and vernal pools. The freshwater marshes are characterized by emergent vegetation including tules and
cattails ''Typha'' is a genus of about 30 species of monocotyledonous flowering plants in the family Typhaceae. These plants have a variety of common names, in British English as bulrushStreeter D, Hart-Davies C, Hardcastle A, Cole F, Harper L. 2009. ...
among other species. Ecologists have identified over 1,500 vernal pools in the area, largely located on private lands. The largest remaining
wetland A wetland is a distinct semi-aquatic ecosystem whose groundcovers are flooded or saturated in water, either permanently, for years or decades, or only seasonally. Flooding results in oxygen-poor ( anoxic) processes taking place, especially ...
s include Anderson Marsh State Park and Rodman Slough. Wetlands in the Clear Lake watershed serve a variety of important ecological functions, including providing habitat for local fish and wildlife, as well as filtering
sedimentation Sedimentation is the deposition of sediments. It takes place when particles in suspension settle out of the fluid in which they are entrained and come to rest against a barrier. This is due to their motion through the fluid in response to th ...
entering the lake from streams. Due to increased agricultural and urban land use, Clear Lake's historic wetland habitats have been reduced by 79%. Agriculture has been a significant form of land use in the region since the mid-19th century. Analysis of sediment cores drawn from the lake indicate that the increase in sedimentation rates corresponds with an increase in the use of heavy agricultural equipment in the 1930s. Other agricultural activities such as stream channelization, groundwater pumping, application of fertilizers and pesticide use have contributed to lake sedimentation, hillside erosion and floodplain encroachment. The primary pollutant of concern associated with agriculture in the area is
nitrate Nitrate is a polyatomic ion with the chemical formula . salt (chemistry), Salts containing this ion are called nitrates. Nitrates are common components of fertilizers and explosives. Almost all inorganic nitrates are solubility, soluble in wa ...
, with elevated nitrate levels having been identified in the Big Valley area. Agriculture impacts area groundwater sources through pumping, and is responsible for 82% of water usage in the watershed. This usage may contribute to early drying of stream beds, which impacts local wildlife and riparian vegetation.


Pesticides

In 1949, as part of an effort to boost tourism and improve the local economy, DDD (dichlorodiphenyldichloroethane) was applied to the lake in heavy doses to eradicate the gnats that were driving summer tourists away from the lake. The treatment succeeded in controlling the gnats that year and for the following year; however, the gnat population rebounded in 1953, prompting another application in 1954. The final application of DDD to Clear Lake was made in 1957 (Cook 1963). Numbers of western grebe were found dead, their tissues containing high concentrations of DDD. The effects were devastating to the local ecology. From 1962 to 1975, carefully planned applications of methyl parathion were made for Clear Lake gnat control. The gnat still occurs in Clear Lake, but at much lower numbers than in the 1940s–1970s. Its population is believed to be kept in check now by two introduced fish species (the threadfin shad and the inland silverside) that compete with the gnat for its preferred
zooplankton Zooplankton are the heterotrophic component of the planktonic community (the " zoo-" prefix comes from ), having to consume other organisms to thrive. Plankton are aquatic organisms that are unable to swim effectively against currents. Consequent ...
for food.


Invasive species

The ecology of Clear Lake has been significantly altered due to the presence of
invasive species An invasive species is an introduced species that harms its new environment. Invasive species adversely affect habitats and bioregions, causing ecological, environmental, and/or economic damage. The term can also be used for native spec ...
. A notable invasive species is
hydrilla ''Hydrilla'' (waterthyme) is a genus of aquatic plant, usually treated as containing just one species, ''Hydrilla verticillata'', though some botanists divide it into several species. It is native to the cool and warm waters of the Old World in A ...
(''Hydrilla verticillata''), a submerged aquatic plant which notably out-competes both native and non-native species to create pure stands. The plant established so successfully due to its ability to break into smaller propagules, which can survive in sediment for up to seven years. The presence of hydrilla can affect fish stocks, and interfere with recreational boating or fishing. Hydrilla prevention is overseen by the
California Department of Food and Agriculture The California Department of Food and Agriculture (CDFA) is a Cabinet (government), cabinet-level agency in the government of California. Established in 1919 by the California State Legislature and signed into law by Governor William Stephens (Am ...
’s Hydrilla Eradication Program, whose goal is the eradication of existing hydrilla populations and prevention of future infestations. The program has been highly successful, managing to keep the lake hydrilla-free for two years before being detected once again in 2019. Furthermore, the lake has been subjected to a long history of non-native fish introductions. In the 1860s and 1870s,
goldfish The goldfish (''Carassius auratus'') is a freshwater fish in the family Cyprinidae of the order Cypriniformes. It is commonly kept as a pet in indoor aquariums, and is one of the most popular aquarium fish. Goldfish released into the w ...
(''Carassius auratus'') and
lake whitefish The lake whitefish (''Coregonus clupeaformis'') is a species of freshwater whitefish from North America. Lake whitefish are found throughout much of Canada and parts of the northern United States, including all of the Great Lakes. The lake white ...
(''Coregonus clupeaformis'') were some of the first species to be introduced to Clear Lake. Mississippi silverside (''Menidia audens'') were the most abundant fish in the lake soon after their introduction in 1967. Moreover, both the Florida strain largemouth bass (''Micropterus salmoides floridanus'') and the Northern
largemouth bass The largemouth bass (''Micropterus nigricans'') is a carnivorous, freshwater fish, freshwater, ray-finned fish in the Centrarchidae (sunfish) family, native to the eastern United States, eastern and central United States, southeastern Canada an ...
(''M. salmoides salmoides'') populations of the lake have persisted for decades after introduction. The lake is also actively monitored for
quagga mussel The quagga mussel (''Dreissena bugensis'') is a species (or subspecies) of freshwater mussel, an aquatic bivalve mollusk in the family Dreissenidae. It has an average lifespan of 3 to 5 years. The species is indigenous to the Dnipro River dr ...
s (''Dreissena bugensis'') and
zebra mussel The zebra mussel (''Dreissena polymorpha'') is a small freshwater mussel, an Aquatic animal, aquatic bivalve mollusk in the family Dreissenidae. The species originates from the lakes of southern Russia and Ukraine, but has been accidentally Intro ...
s (''D. polymorpha''), although there are no established populations of either species in Clear Lake.


Harmful algal blooms

Due to its shallow depth and warm temperatures, Clear Lake is naturally eutrophic. Written records documenting cloudy discolorations in the lake exist from the late 19th century.
Cyanobacteria Cyanobacteria ( ) are a group of autotrophic gram-negative bacteria that can obtain biological energy via oxygenic photosynthesis. The name "cyanobacteria" () refers to their bluish green (cyan) color, which forms the basis of cyanobacteri ...
(blue-green algae) in the lake can produce blooms often beginning in the spring and lasting through the fall. Referred to as
harmful algal bloom A harmful algal bloom (HAB), or excessive algae growth, sometimes called a red tide in marine environments, is an algal bloom that causes negative impacts to other organisms by production of natural algae-produced toxins, water deoxygenation, ...
s (HAB), these blooms consist of solid mats of scum and are associated with unpleasant odors. Studies have shown that increased nutrient contents, especially in the form of
phosphorus Phosphorus is a chemical element; it has Chemical symbol, symbol P and atomic number 15. All elemental forms of phosphorus are highly Reactivity (chemistry), reactive and are therefore never found in nature. They can nevertheless be prepared ar ...
, from
fertilizer A fertilizer or fertiliser is any material of natural or synthetic origin that is applied to soil or to plant tissues to supply plant nutrients. Fertilizers may be distinct from liming materials or other non-nutrient soil amendments. Man ...
runoff can potentially influence cyanobacteria blooms The California Water Boards have found that phosphorus loading in Clear Lake is largely driven by sedimentation due to erosion from agricultural activities as well as channel erosion, mining activities, wildfires, off-highway vehicle use, and timber harvesting. Harmful algae blooms have been found in the waters of private wells close to the lakeshore. Types of
toxin A toxin is a naturally occurring poison produced by metabolic activities of living cells or organisms. They occur especially as proteins, often conjugated. The term was first used by organic chemist Ludwig Brieger (1849–1919), derived ...
-producing cyanobacteria that have been identified in Clear Lake include the following genera: ''
Anabaena ''Anabaena'' is a genus of filamentous cyanobacteria that exist as plankton. They are known for nitrogen-fixing abilities, and they form symbiotic relationships with certain plants, such as the mosquito fern. They are one of four genera of cyan ...
'', '' Microcystis'', ''
Oscillatoria ''Oscillatoria'' is a genus of filamentous cyanobacteria. It is often found in freshwater environments. Its name refers to the oscillating motion of its filaments as they slide against each other to position the colony to face a light source. ...
'', ''
Planktothrix ''Planktothrix'' is a diverse genus of filamentous cyanobacteria observed to amass in algal blooms in water ecosystems across the globe. Like all Oscillatoriales, ''Planktothrix'' species have no heterocyst, heterocysts and no akinetes. ''Plankto ...
'', '' Aphanizomenon'', '' Cylindrospermopsis'', and '' Lyngbya'', all of which can cause short- and long-term health effects. Studies are ongoing to determine the various environmental factors responsible for harmful algal blooms.


Heavy metal contamination

The lake is heavily contaminated with mercury from the nearby Sulphur Bank Mercury Mine. The abandoned mine was declared a
Superfund site Superfund sites are Pollution, polluted locations in the United States requiring a long-term response to clean up hazardous material contaminations. Sites include landfills, mines, manufacturing facilities, processing plants where toxic waste h ...
in the early 1990s and is still undergoing clean-up. The
California Department of Fish and Wildlife The California Department of Fish and Wildlife (CDFW), formerly known as the California Department of Fish and Game (CDFG), is an American state agency under the California Natural Resources Agency. The Department of Fish and Wildlife manages ...
presently recommends that women of child-bearing age and children do not consume certain fish from Clear Lake, due to the presence of
methylmercury Methylmercury is an organometallic cation with the formula . It is the simplest organomercury compound. Methylmercury is extremely toxic, and its derivatives are the major source of organic mercury for humans. It is a bioaccumulative environment ...
compounds in lake sediments.


Monitoring, mitigation, and restoration

Clear Lake has been identified as an impaired water body under Section 303(d)(1)(A) of the
Clean Water Act The Clean Water Act (CWA) is the primary federal law in the United States governing water pollution. Its objective is to restore and maintain the chemical, physical, and biological integrity of the nation's waters; recognizing the primary respo ...
. This designation indicates that the water body does not comply with applicable water quality standards. As such, the area is required to comply with quality management strategies such as Total Maximum Daily Loads (TMDLs) to satisfy federal regulatory requirements. The Central Valley Regional Water Quality Control Board has identified point sources of pollution in Clear Lake as
Caltrans The California Department of Transportation (Caltrans) is an Executive (government), executive department of the U.S. state of California. The department is part of the Government of California#State agencies, cabinet-level California State Tran ...
and storm water permitees. Nonpoint sources of pollution in Clear Lake include the
Bureau of Land Management The Bureau of Land Management (BLM) is an agency within the United States Department of the Interior responsible for administering federal lands, U.S. federal lands. Headquartered in Washington, D.C., the BLM oversees more than of land, or one ...
, the
U.S. Forest Service The United States Forest Service (USFS) is an agency within the U.S. Department of Agriculture. It administers the nation's 154 national forests and 20 national grasslands covering of land. The major divisions of the agency are the Chief's ...
, irrigated agriculture, and the County of Lake The lake and the surrounding watershed are being monitored through sampling of gauges placed by the
California Department of Water Resources The California Department of Water Resources (DWR) is part of the California Natural Resources Agency and is responsible for the management and regulation of the State of California's water usage. The department was created in 1956 by Governor ...
. The Middle Creek Project was started in 1995 by Lake County to restore native wetlands to the Clear Lake area. The project set a goal of expanding the current
wetland A wetland is a distinct semi-aquatic ecosystem whose groundcovers are flooded or saturated in water, either permanently, for years or decades, or only seasonally. Flooding results in oxygen-poor ( anoxic) processes taking place, especially ...
s area to double its current size. Lake County has additionally ensured no further loss of wetlands by the passage of the County Shoreline Ordinance which prohibits the removal of wetland vegetation on private property. In 2009 the Middle Creek and Hamilton City Flood Damage Restoration and Ecosystem Act (AB74) was signed by Governor
Arnold Schwarzenegger Arnold Alois Schwarzenegger (born July30, 1947) is an Austrian and American actor, businessman, former politician, and former professional bodybuilder, known for his roles in high-profile action films. Governorship of Arnold Schwarzenegger, ...
. The project was to provide funding to breach the
levee A levee ( or ), dike (American English), dyke (British English; see American and British English spelling differences#Miscellaneous spelling differences, spelling differences), embankment, floodbank, or stop bank is an elevated ridge, natural ...
s and restore of lake and wetland. Bloody Island should again be an island. The project has the additional aim of reducing the amount of
phosphorus Phosphorus is a chemical element; it has Chemical symbol, symbol P and atomic number 15. All elemental forms of phosphorus are highly Reactivity (chemistry), reactive and are therefore never found in nature. They can nevertheless be prepared ar ...
entering the lake by 40%. The additional water resulting from the increased lake area is to be allocated to municipal districts drawing water from the lake. Yolo's water allowance under the Solano decree may also be increased. The passage of Assembly Bill 707 allowed for the creation of the Blue Ribbon Committee for the Rehabilitation of Clear Lake. The committee is made up of 15 county-appointed members from tribes, universities and various governmental organizations. The committee is charged with providing scientifically sound recommendations for the management of Clear Lake's "economy, ecosystem, and heritage". A Cyanobacteria Task Force was formed in 2014 which includes the Big Valley, Elem, Scotts Valley and Robinson tribes, as well as various state and federal governmental agencies. The task force focuses primarily on monitoring activities, particularly water sampling and testing for toxins. Various local ordinances protect the lake from land-use practices in the domesticated areas of the surrounding watershed, and the lake's water quality impairments are addressed by federal and state regulatory programs. Multiple water suppliers in communities surrounding the lake provide potable water for municipal uses in accordance with California's public health regulations. Lake County participates in the state's Department of Water Resources' Integrated Regional Water Management programs, within the Westside Region including Lake, Colusa, Napa, Solano, and Yolo counties. The Lake County Watershed Protection District is the lead agency for Lake County's participation in the Westside Region's long-term (2013–2033) water management programs. Within the jurisdictional boundary of the County of Lake, the Watershed Protection District provides the "Lake County Clean Water Program" for compliance with the National Pollutant Discharge Elimination System (NPDES) pollution prevention programs, and with the NPDES stormwater management permit (issued by the State Water Resources Control Board as Water Quality Order 2013-0001-DWQ), by implementing the Lake County "Stormwater Management Plan". Lake County also complies with the NPDES aquatic pesticide permit program, allowing licensed pesticide applicators to eradicate nuisance aquatic weeds, in accordance with the "Clear Lake Integrated Aquatic Plant Management Plan". Multi-jurisdictional programs for natural resource management in the Clear Lake watershed—including federal, state, and local land owners in the County of Lake—are described in the "Clear Lake Integrated Watershed Management Plan".


See also

* List of reservoirs and dams in California *
List of lakes in California There are more than 3,000 named lakes, reservoirs, and dry lakes in the U.S. state of California. Largest lakes In terms of area covered, the largest lake in California is the Salton Sea, a lake formed in 1905 which is now saline. It occup ...


References


External links

*   *  
County of Lake

Lake County Visitor Guide
* {{authority control Lakes of Lake County, California Lakes of California Lakes of Northern California