Aqueduct (water supply)
An aqueduct is a watercourse constructed to carry water from a source to a distribution point far away. In modern engineering, the term aqueduct is used for any system of pipes, canals and other structures used for this purpose; the term aqueduct often refers to a bridge on an artificial watercourse. The word is derived from ducere. Aqueducts were used in ancient Greece, ancient Egypt, ancient Rome. In modern times, the largest aqueducts of all have been built in the United States to supply the country's biggest cities; the simplest aqueducts are small ditches cut into the earth. Much larger channels may be used in modern aqueducts. Aqueducts sometimes run for all of their path through tunnels constructed underground. Modern aqueducts may use pipelines. Agricultural societies have constructed aqueducts to irrigate crops and supply large cities with drinking water. Although associated with the Romans, aqueducts were devised much earlier in Greece and the Near East and Indian subcontinent, where peoples such as the Egyptians and Harappans built sophisticated irrigation systems.
Roman-style aqueducts were used as early as the 7th century BC, when the Assyrians built an 80 km long limestone aqueduct, which included a 10 m high section to cross a 300 m wide valley, to carry water to their capital city, Nineveh. The Indian subcontinent is believed to have some of the earliest aqueducts. Evidence can be found at the sites of Karnataka; the massive aqueducts near river Tungabhadra supplying irrigation water were once 15 miles long. The waterways supplied water to royal bath tubs. In Oman from the Iron Age, in Salut and other sites, a system of underground aqueducts called falaj or qanāts were constructed, a series of well-like vertical shafts, connected by sloping horizontal tunnels. There are three types of falaj: Daudi with underground aqueducts Ghaili requiring a dam to collect the water Aini whose source is a water springThese enabled large scale agriculture to flourish in a dry land environment. In Persia from early times a system of underground aqueducts called qanāts were constructed, a series of well-like vertical shafts, connected by sloping tunnels.
This technique: taps into subterranean water in a manner that delivers water to the surface without need for pumping. The water drains relying on gravity, with the destination lower than the source, an upland aquifer. Allows water to be transported long distances in hot dry climates without losing a large proportion of the source water to seepage and evaporation. Throughout Petra, the Nabataean engineers took advantage of every natural spring and every winter downpour to channel water where it was needed, they constructed aqueducts and piping systems that allowed water to flow across mountains, through gorges and into the temples and gardens of Petra's citizens. Walking through the Siq, one can spot the remains of channels that directed water to the city center, as well as durable retention dams that kept powerful flood waters at bay. On the island of Samos, the Tunnel of Eupalinos was built during the reign of Polycrates, it is considered an underground aqueduct and brought fresh water to Pythagoreion for a thousand years.
Roman aqueducts were built in all parts of the Roman Empire, from Germany to Africa, in the city of Rome, where they totaled over 415 kilometres. The aqueducts supplied fresh water to public baths and for drinking water, in large cities across the empire, set a standard of engineering, not surpassed for more than a thousand years. Bridges, built in stone with multiple arches, were a distinctive feature of Roman aqueducts and hence the term aqueduct is applied to a bridge for carrying water. Near the Peruvian town of Nazca, an ancient pre-Columbian system of aqueducts called Puquios were built and are still in use today, they were made of intricately placed stones, a construction material used by the Nazca culture. The time period in which they were constructed is still debated, but some evidence supports circa A. D. 540–552, in response to drought periods in the region. The Guayabo National Monument of Costa Rica, a park covering the largest archaeological site in the country, contains a system of aqueducts.
The complex network of uncovered and covered aqueducts still functions well. The aqueducts are constructed from rounded river stones, which are made of volcanic rock; the civilization that constructed the aqueduct system remains a mystery to archaeologists. When Europeans saw the Aztec capital Tenochtitlán, early in the 16th century, the city was watered by two aqueducts. One of these, Chapultepec Aqueduct, built circa 1420, was rebuilt by the Spanish three hundred years later. Tracing part of its path over now-gone Lake Texcoco, only a fragment remains in Mexico City today. Extensive usage of elaborate aqueducts have been found to have been used in ancient Sri Lanka; the best example is the Yoda Ela or Jaya Ganga, an 87 kilometres long water canal carrying excess water between two artificial reservoirs with a gradient of 10 to 20 cm per kilometer during the fifth century AD. However, the ancient engineering methods in calculating the exact elevation between the two reservoirs and the exact gradient of the canal to such fine precision had been lost with the fall of the civilization in 13th Century.
In modern times, the largest aqueducts of all have been built in the United States to supply the country's biggest cities. The Catskill Aqueduct carries
Lake Oroville is a reservoir formed by the Oroville Dam impounding the Feather River, located in Butte County, northern California. The lake is situated 5 miles northeast of the city of Oroville, within the Lake Oroville State Recreation Area, in the western foothills of the Sierra Nevada. Known as the second-largest reservoir in California, Lake Oroville is treated as a keystone facility within the California State Water Project by storing water, providing flood control, freshwater releases assist in controlling the salinity intrusion Sacramento-San Joaquin Delta and protecting fish and wildlife; the lake is a popular nationally renowned bass fishing location, while coho salmon are stocked from the Feather River Fish Hatchery. This hatchery is a main component of Lake Oroville; the local indigenous tribe were the Konkow Maidu who settled the lake region and Feather River for many years. Today many of the small towns including Oroville were occupied by the Maidu people. In 2002, a Sonoma State study took archaeological inventory of the 15,476 acres of Lake Oroville to learn 250 sites are from the prehistoric era relating to the Native American life along the Feather River and an additional 478 sites dating to the Gold Rush.
These sites included open-air residential sites and rockshelters, limited lithic scatters, rock art and workshops, bedrock milling sites and cemetery areas. Natives lives were disrupted by gold discovery in 1848 and the white miners infiltrated their lands. In April 1848, only three months after gold was discovered at Sutter's Mill, John Bidwell found gold on the Feather River at a spot known today as the town of Bidwell Bar. Bidwell began to work the claim using local Konkow Maidu workers, due to the rapid spreading news of the California strikes under a year California's non-native population climbed from 20,000 to 100,000 and by 1850 Butte County alone supported 3,052 miners. Construction on the dam began in 1957 to relocate what is now Highway 70 and the Western Pacific Railroad. A few years the completed dam checked flooding on the Feather River in December 1964; this saved the Sacramento Valley from flooding. Prior to impoundment by the Oroville Dam, the current main basin of Lake Oroville was the location of the confluence of the North Fork Feather River with the Feather River and the now-inundated towns of Bidwell and Land.
Completed in 1968, Oroville Dam is an earthen dam and is the tallest dam located in the United States, measuring over 770 feet high and 6,920 feet across. The dam was the largest earth-fill dam in the world, it was built by the California Department of Water Resources as part of the California State Water Project. The dam houses the Edward Hyatt Powerplant, an underground hydro-electric plant, completed in 1967. Six generators are used to provide a maximum generating capacity of 819 MW. Lake Oroville and Oroville Dam are part of a water infrastructure complex including the Hyatt Powerplant, Thermalito Diversion Dam and Powerplant, the Feather River Fish Hatchery, Thermalito Power Canal, Thermalito Forebay, Thermalito Pumping-Generating Plant, Thermalito Afterbay, the Lake Oroville Visitors Center; the lake is fed by the North Fork, Middle Fork, West Branch and South Forks of the Feather River watershed. This watershed drains an area of 3,611 square miles; the North Fork and Middle Fork Feather Rivers comprise 3,222 square miles of this area which includes portions of the foothill and mountain regions of the northern Sierra Nevada and southern Cascade Range.
Storing over 3,500,000 acre feet, it is the second-largest reservoir in California, after Shasta Lake. About one-third of the water released from the reservoir goes to uses between the Oroville and Sacramento-San Joaquin Delta. Lake Oroville plays an important role in flood management, water quality, the health of fisheries affecting areas downstream like the Sacramento-San Joaquin River Delta. During the warm season, the primary source of streamflow is melting snow, occurring April 1 - July 31, Lake Oroville receives about 40 percent of the annual total inflow; the lake's storage and releases are a key part of the hydropower and water-supply facilities of the Oroville Complex, the reason it's a pillar and major source of flexibility of the SWP. The downstream flow limits set by the USACE for Lake Oroville are 150,000 cu ft/s north of Honcut Creek, 180,000 cu ft/s above the mouth of the Yuba River, 320,000 cu ft/s south of the Bear River; the Federal Energy Regulatory Commission licenses hydroelectric facilities such as the Edward Hyatt Power Plant at Oroville Dam.
California's Department of Water Resources and stakeholders participated in a six-year renewal process for a 50-year hydroelectric license for the Oroville Facilities. This agreement commits the state to: restore salmon and steelhead habitat, improved river recreation and community benefits, a fish passage study to determine and launch a project to enhance passage in the Feather and surrounding river basins. Due to federal flood control requirements, by mid-October each year, the lake's storage must be reduced to a specified level within the range of a maximum flood control pool of 750,000 acre feet and a minimum of 375,000 acre feet; each day the allowable level within the range is recalculated using an index reflecting the watershed wetness and the anticipation of heavy runoff from incoming storms. As a wet season like 1997-98 occurred progresses the allowable storage trends to coincide with the maximum flood co
Southern California Edison
Southern California Edison, the largest subsidiary of Edison International, is the primary electricity supply company for much of Southern California. It provides 14 million people with electricity across a service territory of 50,000 square miles. However, the Los Angeles Department of Water and Power, San Diego Gas & Electric, Imperial Irrigation District, some smaller municipal utilities serve substantial portions of the southern California territory; the northern part of the state is served by the Pacific Gas & Electric Company of San Francisco. Southern California Edison still owns all of its electrical transmission facilities and equipment, but the deregulation of California's electricity market in the late 1990s forced the company to sell many of its power plants, though some were sold by choice. In California, SCE retained only its hydroelectric plants, totaling about 1,200 MW, its 75% share of the 2,150-MW San Onofre Nuclear Generating Station, shut down since January 2012. SCE still owns about half of the 1,580-MW coal-fired Mohave Generating Station in Laughlin, which supplied electricity to California and Arizona.
The utility lost all of its natural gas-fired plants, which provided most of its electrical generation. The large, aging plants were bought by out-of-state companies such as Mirant and Reliant Energy, which used them to manipulate the California energy market. Southern California Edison's power grid is linked to PG&E's by the Path 26 wires that follow Interstate 5 over Tejon Pass; the interconnection takes place at a massive substation at Buttonwillow. PG&E's and WAPA's Path 15 and Path 66 from Buttonwillow north connect to BPA's grid in the Pacific Northwest. There are several other interconnections with local and out-of-state utilities, such as Path 46. In addition, SCE operates a regulated water utility. SCE is the sole commercial provider of natural gas and fresh water service to Santa Catalina Island, including the city of Avalon, California. SCE operates the utilities under the names of Catalina Island Gas Company and Catalina Island Water Company; the origins of the company lie with the grand scheme of magnate Henry E. Huntington and hydraulic engineer John S. Eastwood, developed around 1908, for a vast complex of reservoirs to be constructed in the Sierra Nevada Mountains of central California.
Huntington founded Pacific Light and Power, one of the two dozen companies he controlled at the time, to execute what would become one of the largest hydropower systems in the United States, the Big Creek Hydroelectric Project. Pacific Light and Power was one of the predecessor companies to SCE, along with Edison Electric, Mt. Whitney Power & Electric Co. California Electric Power Co. Southern California Power Co. and others. In November, 2014, Southern California Edison announced a partnership with Ice Energy to provide more efficient energy storage by freezing water at night when electricity is cheaper. In 2015, Southern California Edison began laying off American information technology employees and replacing them with H-1B visa immigrants from India; the layoffs were questioned by members of the United States Senate. Southern California Edison agreed to pay a $650,000 settlement for the 2011 blackout with FERC and NERC. On December 16, 2011, a shooting occurred when an employee of Southern California Edison opened fire at an office building in Irwindale.
The employee killed two co-workers and wounded two others before committing suicide. Southern California Edison allows its customer to obtain their electricity from renewable sources by subscribing to a "green rate". In 2006, Southern California Edison planned to secure 1,500 megawatts or more of power generated from new projects to be built in the Tehachapi Pass Wind Farm area; the contract, which more than doubles SCE's wind energy portfolio, envisions more than 50 square miles of wind parks in the Tehachapi region, triple the size of any existing U. S. wind farm. In March 2008, Southern California Edison announced a $875 million project to build a network of 250 megawatts of photovoltaic solar power generation, making it the biggest solar cell project in the nation; the photovoltaic cells will cover 65,000,000 square feet of rooftops in southern California and will generate enough power to serve 162,000 homes. In 2009, Southern California Edison entered into a contract with Solar Millennium to purchase solar thermal power up to 726 MW.
Southern California Edison entered into a contract with Stirling Energy Systems to buy electricity from a 500 megawatt, 4,600 acre, solar power plant, due to open in 2009. The purchase was canceled in late 2010, as changes in technology reduced the cost of photovoltaic-based solar power to below that of solar Stirling generated power; this would have been the first commercial application of the dish stirling system. A different technology from the more familiar solar panel, the dish concentrates solar energy by the use of reflective surfaces and by the use of the Stirling heat engine to convert the heat into electricity. In 2014, Southern California Edison installed more than 600,000 lithium-ion battery cells at a substation in Tehachapi, California in order to test storing power generated from an area that has 5,000 wind turbines. In 2014 SCE had a renewables mix of 23%. By 2016, 28.2% of SCE's power
Sacramento–San Joaquin River Delta
The Sacramento–San Joaquin River Delta, or California Delta, is an expansive inland river delta and estuary in Northern California. The Delta is formed at the western edge of the Central Valley by the confluence of the Sacramento and San Joaquin rivers and lies just east of where the rivers enter Suisun Bay; the Delta is recognized for protection by the California Bays and Estuaries Policy. The city of Stockton is located on the San Joaquin River on the eastern edge of the delta; the total area of the Delta, including both land and water, is about 1,100 square miles. The Delta was formed by the raising of sea level following glaciation, leading to the accumulation of Sacramento and San Joaquin River sediments behind the Carquinez Strait, the sole outlet from the Central Valley to San Pablo and San Francisco Bays and the Pacific Ocean; the narrowness of the Carquinez Strait coupled with tidal action has caused the sediment to pile up, forming expansive islands. Geologically, the Delta has existed since the end of the last Ice Age.
In its natural state, the Delta was a large freshwater marsh, consisting of many shallow channels and sloughs surrounding low islands of peat and tule. Since the mid-19th century, most of the region has been claimed for agriculture. Wind erosion and oxidation have led to widespread subsidence on the Central Delta islands. Much of the water supply for central and southern California is derived from here via pumps located at the southern end of the Delta, which deliver water for irrigation in the San Joaquin Valley and municipal water supply for southern California; the Delta consists of 57 reclaimed islands and tracts, surrounded by 1,100 miles of levees that border 700 miles of waterways. The southwestern side of the Delta lies at the foothills of the California Coast Ranges, while to the northwest sit the lower Montezuma Hills. Most of the Delta lies within Contra Costa, San Joaquin and Yolo Counties; the total human population of the Delta was 515,264 as of 2000. Altogether, the Delta covers 1,153 square miles, with 841 sq mi, or nearly 73 percent, devoted to agriculture.
About 100 sq mi of the Delta area is urban and 117 sq mi. The rivers, streams and waterways of the Delta total about 95 sq mi of surface, although this fluctuates with seasons and tides. Geologically, it is not considered a true river delta, but rather an inverted river delta, as it formed inward rather than outward; the only other major river delta in the world located this far inland is the Pearl River Delta in China. The main source rivers include the Sacramento River from the north, the San Joaquin from the southeast, the Calaveras and Mokelumne Rivers from the east; the Calaveras and Mokelumne are both tributaries of the San Joaquin River. The Sacramento and San Joaquin Rivers join at the western end of the Delta near Pittsburg, at the head of Suisun Bay, although they are linked upstream by the Georgiana Slough, first used by steamboats in the 19th century as a shortcut between Sacramento and Stockton; the southwestern part of the Delta is transected by the Middle River and Old River, former channels of the San Joaquin.
These rivers transport more than 30 million acre feet of water through the Delta each year – about 50 percent of all California's runoff. Nearby cities include Lodi and Stockton to the east and Manteca to the south, Brentwood to the southwest, Pittsburg and Antioch to the west; the state capital, Sacramento, is located just to the north of the Delta. The Sacramento River Deep Water Ship Channel connects the Delta to the Port of Sacramento, with its terminus located near Rio Vista, on the northwestern side of the Delta; the Stockton Ship Channel is a dredged and straightened section of the San Joaquin River cutting directly through the Delta from the Port of Stockton to the San Joaquin's confluence with the Sacramento near Antioch. The Delta was located at the bottom of a large inland sea in the Central Valley, which formed as the uplift of the California Coast Ranges blocked off drainage from the Sierra Nevada to the Pacific. About 560,000 years ago, water breached the mountains, carving out the present-day Carquinez Strait and San Francisco Bay.
The drainage of all the water through this narrow gap formed a bottleneck in the Central Valley's outflow. The Delta in its contemporary state began to form about 10,000 years ago at the end of the last Ice Age. During the Ice Age global sea levels were about 300 ft lower than today, the Delta region, as well as Suisun Bay, the Carquinez Strait and San Francisco Bay, were a river valley through which the continuation of the Sacramento and San Joaquin Rivers flowed to the Pacific Ocean; when sea levels rose again, ocean water backed up through the Carquinez Strait into the Central Valley. The early delta was composed of shifting channels, sand dunes, alluvial fans and floodplains that underwent constant fluctuation because of rising seas – one inch per year. About 8,000 years ago, the rate of sea-level rise slackened, allowing wetland plants to take hold in the Delta, trapping sediment. Th
The Sacramento River is the principal river of Northern California in the United States, is the largest river in California. Rising in the Klamath Mountains, the river flows south for 400 miles before reaching the Sacramento–San Joaquin River Delta and San Francisco Bay; the river drains about 26,500 square miles in 19 California counties within the fertile agricultural region bounded by the Coast Ranges and Sierra Nevada known as the Sacramento Valley, but extending as far as the volcanic plateaus of Northeastern California. Its watershed has reached as far north as south-central Oregon where the now endorheic Goose Lake experiences southerly outflow into the Pit River, the most northerly tributary of the Sacramento; the Sacramento and its wide natural floodplain were once abundant in fish and other aquatic creatures, notably one of the southernmost large runs of chinook salmon in North America. For about 12,000 years, humans have depended on the vast natural resources of the watershed, which had one of the densest Native American populations in California.
The river has provided a route for travel since ancient times. Hundreds of tribes sharing regional customs and traditions inhabited the Sacramento Valley, first coming into contact with European explorers in the late 1700s; the Spanish explorer Gabriel Moraga named the river Rio de los Sacramentos in 1808 shortened and anglicized into Sacramento. In the 19th century, gold was discovered on a tributary of the Sacramento River, starting the California Gold Rush and an enormous population influx to the state. Overland trails such as the California Trail and Siskiyou Trail guided hundreds of thousands of people to the gold fields. By the late part of the century mining had ceased to be a major part of the economy, many immigrants turned to farming and ranching. Many populous communities were established along the Sacramento River, including the state capital of Sacramento. Intensive agriculture and mining contributed to pollution in the Sacramento River, significant changes to the river's hydrology and environment.
Since the 1950s the watershed has been intensely developed for water supply and the generation of hydroelectric power. Today, large dams impound the river and all of its major tributaries; the Sacramento River is used for irrigation and serves much of Central and Southern California through the canals of giant state and federal water projects. While its now providing water to over half of California's population and supporting the most productive agricultural area in the nation, these changes have left the Sacramento modified from its natural state and have caused the decline of its once-abundant fisheries; the Sacramento River originates in the mountains and plateaus of far northern California as three major waterways that flow into Shasta Lake: the Upper Sacramento River, McCloud River and Pit River. The Upper Sacramento begins near Mount Shasta, at the confluence of North and South Forks in the Trinity Mountains of Siskiyou County, it flows east into Lake Siskiyou, before turning south. The river flows through a canyon for about 60 miles, past Dunsmuir and Castella, before emptying into Shasta Lake near Lakehead in Shasta County.
The McCloud River rises on the east slope of Mount Shasta and flows south for 77 miles through the southern Cascade Range parallel to the Upper Sacramento to reach the McCloud Arm of Shasta Lake. The Pit River, by far the largest of the three, begins in Modoc County in the northeastern corner of California. Draining a vast and remote volcanic highlands area, it flows southwest for nearly 300 miles before emptying into Shasta Lake near Montgomery Creek. Goose Lake, straddling the Oregon–California border overflows into the Pit River during wet years, although this has not happened since 1881; the Goose Lake watershed is the only part of the Sacramento River basin extending into another state. Unlike most California rivers, the Pit and the McCloud Rivers are predominantly spring-fed, ensuring a large and consistent flow in the driest of summers. At the lower end of Shasta Lake is Shasta Dam, which impounds the Sacramento River for flood control and hydropower generation. Before the construction of Shasta Dam, the McCloud River emptied into the Pit River, which joined the Sacramento near the former mining town of Kennett, submerged when Shasta Lake was filled.
The Pit River Bridge, which carries Interstate 5 and the Union Pacific Railroad over the reservoir, is structurally the highest double-decked bridge in the United States. The Upper Sacramento River canyon provides the route for I-5 and the railroad between Lakehead and Mount Shasta. Below Shasta Dam, it flows through Keswick Dam, where it receives about 1,200,000 acre feet of water per year diverted from the Trinity River. It swings east through Redding, the largest city of the Shasta Cascade region, turns southeast, entering Tehama County. East of Cottonwood it receives Cottonwood Creek – the largest undammed tributary – from the west Battle Creek a short distance downstream. Below Battle Creek it carves its last gorge, Iron Canyon, emerging from the hills at Red Bluff, where a pumping station removes water for irrigation. Beyond Red Bluff the river reaches the low floodplain of the Sacramento Valley, receiving Mill Creek from the east and Thomes Creek from the west near Los Molinos Deer Creek from the east near Vina.
Southeast of Corni
O'Neill Dam is an earthfill dam on San Luis Creek, 12 miles west of Los Banos, United States, on the eastern slopes of the Pacific Coast Ranges of Merced County. Forming the O'Neill Forebay, a forebay to the San Luis Reservoir, it is 2.5 miles downstream from the San Luis Dam. Built from 1963 to 1967, the dam is an earthfill and rockfill construction stretching over 3 miles across the valley of San Luis Creek. A morning-glory type spillway lies at the left bank of the reservoir. At 87.5 feet high, with a maximum reservoir depth of 57 feet, the crest of the dam is 14,300 feet long, at an elevation of 223 feet. The spillway is, as mentioned before, a morning-glory design, capacity 3,250 cubic feet per second, with a circumference of 641.5 feet. The O'Neill Forebay reservoir is fed by releases from the San Luis Dam as well as from the Delta–Mendota Canal. Water from the Delta–Mendota Canal is lifted a vertical distance of 8 feet into a channel running 2,200 feet into the forebay; the peak inflow to the forebay is 15,600 cubic feet per second, from both the San Luis Dam and the Delta–Mendota Canal.
Drainage area of the reservoir downstream of the San Luis Dam is only 18 acres. The O'Neill Pumping-Generating Plant produces 28 megawatts. Irregular water releases from the San Luis Dam and William R. Gianelli Powerplant are collected in the reservoir of the O'Neill Dam, which has a capacity of 56,400 acre feet. List of dams and reservoirs in California Department of Water Resources. "Station Meta Data: O'Neill Forebay". California Data Exchange Center. State of California. Retrieved 2009-04-01. "O'Neill Forebay". Geographic Names Information System. United States Geological Survey. 19 Jan 1981. Retrieved 2009-06-15
The Tehachapi Mountains are a mountain range in the Transverse Ranges system of California in the Western United States. The range extends for 40 miles in southern Kern County and northwestern Los Angeles County; the Tehachapis form a geographic, watershed and rain shadow divide separating the San Joaquin Valley to the northwest and the Mojave Desert to the southeast. The Tehachapis' crest varies in height from 4,000–8,000 feet, they are southeast of Bakersfield and the Central Valley, west of Mojave and the Antelope Valley. The range runs southwest to northeast connecting the Southern Sierra Nevada range on their northeast with the San Emigdio Mountains on the west and Sierra Pelona Mountains on the southwest; the Tehachapis are delineated from the San Emigdio Mountains by Tejon Pass at the range's western end. The dramatic incline of Interstate 5 from the San Joaquin Valley floor up to the pass, is regionally referred to as The Grapevine, after Grapevine Canyon which it follows between the northern slopes of the two mountain ranges and is sometimes extended to include the portion of Interstate 5 on the southern side of Tejon Pass during snow closures.
The canyon was named after native grapevines, the California grapevine, found at springs on its slopes. The California State Water Project is to the east, with the California Aqueduct pumped by the Edmonston Pumping Plant over/through the Tehachapis to Castaic Lake reservoir; the Tehachapis are delineated from the Sierra Pelona Mountains by California State Route 138 at the range's southwestern end, connecting Interstate 5 and the Antelope Valley. The Tehachapis are delineated from the Sierra Nevada by Tehachapi Pass and State Route 58 at the range's northeastern end, connecting the San Joaquin Valley and Mojave Desert; the Union Pacific north/south railroad line, with the famous Tehachapi Loop, crosses here also. The Tehachapi Pass Wind Farm is on its eastern side; the Tehachapis, though neither as long or high as other California mountain ranges, are considered the topographic feature that separates this part of Northern California from Southern California, with the geographic boundary being Kern County.
Some historians consider that California averted a potential split into two separate states – "North California" and "South California" – from the early 20th century Ridge Route construction, the first highway crossing these mountains to connect the Greater Los Angeles and San Joaquin Valley regions. The Tehachapis are the result of the movements of the Garlock Fault, located along the southeastern base of the range, a major transform fault which runs from the San Andreas Fault in the west to the Sierra Nevada Fault on the east and some distance beyond; this earthquake fault is unusual in California in that it is a left-lateral fault — meaning that if one stands facing the fault, the land on the opposite side moves to the left — opposite to most of the state's faults which are right-lateral faults. The Tehachapi Mountains are a major and crucial wildlife corridor and plant habitat bridge linking the other Transverse Ranges and the California Coast Ranges on the west with the Sierra Nevada on the east.
Their relative lack of development in the large Tejon Ranch section, have allowed the continuity of these ecological functions to date. The Tehachapis are in the California interior chaparral and woodlands sub-ecoregion, with native grasslands, California oak woodlands and oak savanna the predominate habitats; the higher montane elevations include the California mixed evergreen forest plant community. Some of the chaparral woodland species include: canyon live oak, valley oak, blue oak, gray pine. Montane species include: black oak, Coulter pine, incense cedar, white fir, in a few remote locations small stands of quaking aspen; the Tehachapi linanthus is a phlox plant species endemic to chaparral habitat in the Tehachapi Mountains and the southern Sierra Nevada. The Tehachapi ragwort is an aster plant species endemic to forest habitat in the Tehachapis and eastern Transverse Ranges; the Tehachapi buckwheat is known only from the chaparral of the Tehachapis. The Tehachapi slender salamander is endemic to the Tehachapi Mountains and a listed vulnerable species.
The white-eared pocket mouse is endemic to the Tehachapis and San Bernardino Mountains and a listed endangered species. There are at least 107 bird species, including the Steller's jay and mountain chickadee, found in the Tehachapis, many which consume acorns of the black oak as part of their diet. Other flora found here include the mountain mahogany; the notable raptor is a critically endangered species. As in many California mountains, larger fauna includes: mule deer, mountain lion, fox, black bear, feral pig and raccoon; the Tehachapi Mountains are the last known breeding site of the jaguar in the United States. The big cats were found there as as the late 1800s; the range includes and is the boundary between the xeric Mojave Desert and Mediterranean climate zones, includes the subalpine zone. The majority of the range is in the Mediterranean climate zone, receiving precipitation in the winter similar to the neighboring Transverse Ranges in the Los Padres and Angeles National Forests to the west and southwest.
They create a rain shadow for the eastern foothills ecotone into the Mojave climate zone that receives only a few inches of precipitation a year in winter. Summer