The Sacramento River ( es, Río Sacramento) is the principal river of

Northern California Northern California (colloquially known as NorCal) is a geographic and cultural region that generally comprises the northern portion of the U.S. state of California. Spanning the state's northernmost 48 counties, its main population centers incl ...

in the United States and is the largest river in California. Rising in the

Klamath Mountains The Klamath Mountains are a rugged and lightly populated mountain range in northwestern California and southwestern Oregon in the western United States. As a mountain system within both the greater Pacific Coast Ranges and the California Coast ...

, the river flows south for before reaching the

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 ...

and

San Francisco Bay San Francisco Bay 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 big cities of San Francisco, San Jose, California, San Jose, and Oakland, Ca ...

. The river drains about in 19 California counties, mostly within the fertile agricultural region bounded by the Coast Ranges and

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 ...

known as the Sacramento Valley, but also extending as far as the volcanic plateaus of Northeastern California. Historically, its watershed has reached as far north as south-central

Oregon Oregon () is a state in the Pacific Northwest region of the Western United States. The Columbia River delineates much of Oregon's northern boundary with Washington, while the Snake River delineates much of its eastern boundary with Idah ...

where the now, primarily,

endorheic An endorheic basin (; also spelled endoreic basin or endorreic basin) is a drainage basin that normally retains water and allows no outflow to other external bodies of water, such as rivers or oceans, but drainage converges instead into lakes ...

(closed) Goose Lake rarely experiences southerly outflow into the Pit River, the most northerly tributary of the Sacramento. The Sacramento and its wide natural

floodplain A floodplain or flood plain or bottomlands is an area of land adjacent to a river which stretches from the banks of its channel to the base of the enclosing valley walls, and which experiences flooding during periods of high discharge.Goudi ...

were once abundant in fish and other aquatic creatures, notably one of the southernmost large runs of

chinook salmon The Chinook salmon (''Oncorhynchus tshawytscha'') is the largest and most valuable species of Pacific salmon in North America, as well as the largest in the genus '' Oncorhynchus''. Its common name is derived from the Chinookan peoples. Other ...

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 trade and 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, later 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 The California Trail was an emigrant trail of about across the western half of the North American continent from Missouri River towns to what is now the state of California. After it was established, the first half of the California Trail f ...

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, and many immigrants turned to farming and ranching. Many populous communities were established along the Sacramento River, including the state capital of

Sacramento ) , image_map = Sacramento County California Incorporated and Unincorporated areas Sacramento Highlighted.svg , mapsize = 250x200px , map_caption = Location within Sacramento ...

. Intensive agriculture and mining contributed to pollution in the Sacramento River, and 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 Hydroelectricity, or hydroelectric power, is electricity generated from hydropower (water power). Hydropower supplies one sixth of the world's electricity, almost 4500 TWh in 2020, which is more than all other renewable sources combined a ...

. Today, large dams impound the river and almost all of its major tributaries. The Sacramento River is used heavily for irrigation and serves much of Central and Southern California through the canals of giant state and federal water projects. While it's 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 greatly modified from its natural state and have caused the decline of its once-abundant fisheries.

Course

Upper river

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, Middle and South Forks in the

Trinity Mountains The Trinity Mountains are a subrange of the Klamath Mountains, one of the ranges within the California Coast Ranges and part the greater Pacific Coast Ranges, the coastal mountain system extending from Mexico to Alaska. The Trinity Mountains subra ...

of Siskiyou County. It flows east into a small reservoir,

Lake Siskiyou Lake Siskiyou is a reservoir formed by Box Canyon DamBox Canyon Dam
NPDP D ...

, before turning south. The river flows through a canyon for about , past

Dunsmuir Dunsmuir may refer to: * Dunsmuir, California, a city in the northern part of the state * Dunsmuir station, an Amtrak station in Dunsmuir, California * Dunsmuir station (British Columbia), a Via Rail station * Dola Dunsmuir, Canadian socialite * Jam ...

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 through the southern Cascade Range, roughly parallel to the Upper Sacramento, eventually 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 before emptying into Shasta Lake near Montgomery Creek. Goose Lake, straddling the

–California border, occasionally 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 even the driest of summers. At the lower end of Shasta Lake is Shasta Dam, which impounds the Sacramento River for flood control, irrigation 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 The Pit River Bridge (officially the Veterans of Foreign Wars Memorial Bridge) is a double deck, deck truss, road and rail bridge over Shasta Lake in Shasta County, California. The bridge, carrying Interstate 5 on its upper deck and Union Pa ...

, which carries

Interstate 5 Interstate 5 (I-5) is the main north–south Interstate Highway on the West Coast of the United States, running largely parallel to the Pacific coast of the contiguous U.S. from Mexico to Canada. It travels through the states of Calif ...

and the

Union Pacific Railroad The Union Pacific Railroad , legally Union Pacific Railroad Company and often called simply Union Pacific, is a freight-hauling railroad that operates 8,300 locomotives over routes in 23 U.S. states west of Chicago and New Orleans. Union Pac ...

over the reservoir, is structurally the highest double-decked bridge in the United States (although most of the bridge piers are submerged under Shasta Lake when the reservoir is full). The Upper Sacramento River canyon also provides the route for I-5 and the railroad between Lakehead and Mount Shasta.

Sacramento Valley

Below Shasta Dam the Sacramento River enters the

foothills Foothills or piedmont are geographically defined as gradual increases in elevation at the base of a mountain range, higher hill range or an upland area. They are a transition zone between plains and low relief hills and the adjacent topographi ...

region of the northern Sacramento Valley. It flows through Keswick Dam, where it receives about of water per year diverted from the Trinity River. It then swings east through Redding, the largest city of the Shasta Cascade region, and turns southeast, entering Tehama County. East of Cottonwood it receives Cottonwood Creek – the largest undammed tributary – from the west, then

Battle Creek Battle Creek is a city in the U.S. state of Michigan, in northwest Calhoun County, at the confluence of the Kalamazoo and Battle Creek rivers. It is the principal city of the Battle Creek, Michigan Metropolitan Statistical Area (MSA), which encom ...

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 (which replaced the Red Bluff Diversion Dam) removes water for irrigation. Beyond Red Bluff the river reaches the low

of the Sacramento Valley, receiving Mill Creek from the east and

Thomes Creek Thomes Creek is a major watercourse on the west side of the Sacramento Valley in Northern California. The creek originates in the Coast Ranges and flows east for about to join the Sacramento River, at a point about northeast of Corning in Te ...

from the west near Los Molinos, then Deer Creek from the east near Vina. Southeast of Corning, the Sacramento forms the boundary of Tehama County to the west and Butte County to the east. A few miles downstream it forms the border of Butte County and

Glenn County Glenn County is a county located in the U.S. state of California. As of the 2020 census, the population was 28,917. The county seat is Willows. It is located in the Sacramento Valley, in the northern part of the California Central Valley. ...

to the west.

Stony Creek Stony Creek may refer to the following waterways or communities: Waterways Australia * Stony Creek, a tributary of the Allyn River, in the Hunter region of New South Wales * Stony Creek, a tributary of the Brogo River, in the South Coast region o ...

joins from the west in Glenn County, near Hamilton City and about west of

Chico Chico () means ''small'', ''boy'' or ''child'' in the Spanish language. It is also the nickname for Francisco in the Portuguese language (). Chico may refer to: Places *Chico, California, a city *Chico, Montana, an unincorporated community *Chic ...

. The river then forms the Glenn– Colusa County line for a short distance before crossing entirely into Colusa County. It passes by the Sutter Buttes, a group of volcanic hills that rise abruptly from the middle of the Sacramento Valley, where it receives Butte Creek from the east at Colusa. Below Colusa the river flows south-southeast, forming the border of Colusa County and Sutter County to the east. About further downstream, the Sacramento River reaches the Tisdale Weir. During floods, water overtops the weir and flows east into the

Sutter Bypass The Sutter Basin is a area of the Sacramento Valley in the U.S. state of California, and is part of the Feather River drainage basin. The basin includes the Sutter Basin Fire Protection District of ~ and uses irrigation from the Thermalito Afterb ...

, the first of two major bypass channels that temporarily store and move floodwaters downstream to reduce pressure on the main channel of the Sacramento. The Sacramento River and the Sutter Bypass flow parallel for over , rejoining on the border of Sutter County and Yolo County near

Knights Landing Knights Landing (formerly, Baltimore and East Grafton) is a census-designated place in Yolo County, California, United States, founded by William Knight. It is located on the Sacramento River around 25 miles northwest of Sacramento in the northeas ...

. The Feather River, the largest tributary of the Sacramento, joins from the east at

Verona Verona ( , ; vec, Verona or ) is a city on the Adige River in Veneto, Italy, with 258,031 inhabitants. It is one of the seven provincial capitals of the region. It is the largest city municipality in the region and the second largest in nor ...

directly below the Sutter Bypass. A second flood control structure, the Fremont Weir, diverts flood waters from both the Sacramento and Feather Rivers into the Yolo Bypass, which parallels the Sacramento River down the west side of the valley. Cache Creek and Putah Creek, two major tributaries which formerly joined the Sacramento River from the west, are now intercepted by the Yolo Bypass via man-made channels. The main channel of the Sacramento flows south, forming the Yolo–

Sacramento County Sacramento County () is a county located in the U.S. state of California. As of the 2020 census, the population was 1,585,055. Its county seat is Sacramento, which has been the state capital of California since 1854. Sacramento County is t ...

line.

Lower river

As the river continues south it approaches the Sacramento metro area, the largest population center in the watershed. Sacramento International Airport is located on the east bank of the river near Fremont. Near downtown Sacramento it receives the

American River , name_etymology = , image = American River CA.jpg , image_size = 300 , image_caption = The American River at Folsom , map = Americanrivermap.png , map_size = 300 , map_caption ...

from the east, then passes under the historic

Tower Bridge Tower Bridge is a Grade I listed combined bascule and suspension bridge in London, built between 1886 and 1894, designed by Horace Jones and engineered by John Wolfe Barry with the help of Henry Marc Brunel. It crosses the River Thames close ...

and Interstate 80 Business. The California State Capitol sits less than half a mile (0.8 km) east of the river where the Tower Bridge crosses it. Shortly downstream, the

Port of Sacramento The Port of Sacramento, now known as the Port of West Sacramento, is an inland port in West Sacramento, California, in the Sacramento metropolitan area. It is northeast of San Francisco, and is centered in the California Central Valley, one of t ...

is located on the west side of the Sacramento, connected to the river by a lock. The

Sacramento River Deep Water Ship Channel The Sacramento Deep Water Ship Channel (also known as Sacramento River Deep Water Ship Channel or SRDWSC) is a canal from the Port of Sacramento in West Sacramento, California, to the Sacramento River, which flows into San Francisco Bay. It ...

provides access to the port from the Pacific, bypassing about of the winding lower Sacramento. The channel runs parallel to the Sacramento several miles to the west, and also forms the eastern boundary of the Yolo Bypass. The manually operated Sacramento Weir, located across from downtown Sacramento on the west side of the river, serves to relieve floodwater pressure from the American River by allowing it to drain west into the Yolo Bypass instead of continuing down the Sacramento River. Downstream of Sacramento, the river enters the

, a vast tidal

estuary An estuary is a partially enclosed coastal body of brackish water with one or more rivers or streams flowing into it, and with a free connection to the open sea. Estuaries form a transition zone between river environments and maritime environm ...

and inverted river delta of over which receives the entire run-off of the Central Valley, a region covering a third of California. The Sacramento is by far the largest contributor of fresh water to the Delta; in an average year, it accounts for more than 80 percent of the fresh water inflow. At Walnut Grove, the manmade Delta Cross Channel connects the Sacramento to the Mokelumne River channel, allowing a portion of the water to be pumped south toward Clifton Court Forebay, the receiving reservoir for the main CVP and

State Water Project The California State Water Project, commonly known as the SWP, is a state water management project in the U.S. state of California under the supervision of the California Department of Water Resources. The SWP is one of the largest public water ...

aqueducts which irrigate millions of acres and supply water to over 23 million people in the

San Joaquin Valley The San Joaquin Valley ( ; es, Valle de San Joaquín) is the area of the Central Valley of the U.S. state of California that lies south of the Sacramento–San Joaquin River Delta and is drained by the San Joaquin River. It comprises seven ...

, the

San Francisco Bay Area The San Francisco Bay Area, often referred to as simply the Bay Area, is a populous region surrounding the San Francisco, San Pablo, and Suisun Bay estuaries in Northern California. The Bay Area is defined by the Association of Bay Area Gov ...

and

Greater Los Angeles Greater Los Angeles is the second-largest metropolitan region in the United States with a population of 18.5 million in 2021, encompassing five counties in Southern California extending from Ventura County in the west to San Bernardino ...

. Although river levels are tidally influenced here and occasionally as far north as Verona, the water stays fresh in all but the driest years. Saltwater intrusion from the Pacific Ocean was one of the main reasons for the construction of the federal Central Valley Project (CVP), whose dams maintain a minimum flow in the Sacramento River to keep seawater at bay. Below Rio Vista, the lower Sacramento River is rejoined by the Deep Water Ship Channel and the Yolo Bypass and curves southwest along the base of the Montezuma Hills, forming the border of Solano and Sacramento Counties. This part of the river is dredged for navigation by large oceangoing vessels and averages three-quarters of a mile (1.2 km) across. North of

Antioch Antioch on the Orontes (; grc-gre, Ἀντιόχεια ἡ ἐπὶ Ὀρόντου, ''Antiókheia hē epì Oróntou'', Learned ; also Syrian Antioch) grc-koi, Ἀντιόχεια ἡ ἐπὶ Ὀρόντου; or Ἀντιόχεια ἡ ἐπ� ...

and Pittsburg, the Sacramento and

San Joaquin River The San Joaquin River (; es, Río San Joaquín) is the longest river of Central California. The long river starts in the high Sierra Nevada, and flows through the rich agricultural region of the northern San Joaquin Valley before reaching ...

s join at the head of Suisun Bay, marking the official end of both rivers. The combined waters flow west through Suisun Bay and the Carquinez Strait into

San Pablo Bay San Pablo Bay is a tidal estuary that forms the northern extension of 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 water c ...

and

, joining the Pacific at the Golden Gate.

Discharge

Following the Columbia River, the Sacramento is the largest river by

discharge Discharge may refer to Expel or let go * Discharge, the act of firing a gun * Discharge, or termination of employment, the end of an employee's duration with an employer * Military discharge, the release of a member of the armed forces from serv ...

on the Pacific coast of the continental United States. The natural runoff of the river is 22 million acre feet (27 km³) per year, or about . Before dams were built on its tributaries, the river flooded up to during the rainy season, equal to the flow of the

Mississippi River The Mississippi River is the second-longest river and chief river of the second-largest drainage system in North America, second only to the Hudson Bay drainage system. From its traditional source of Lake Itasca in northern Minnesota, it ...

. Late summers of particularly dry years could see flows drop below . Large volumes of water are withdrawn from the Sacramento River for irrigation, industry and urban supplies. Annual depletions (water not returned to the river after use) are about 4.72 million acre feet (5.83 km³) for irrigation and for urban use. An additional 7.61 million acre feet (9.39 km³) is reserved for environmental uses, primarily to maintain a minimum fresh water outflow in the Delta to combat salinity. The U.S. Geological Survey (USGS) has stream gauges on 25 locations along the Sacramento River, although not all of them are currently operational. The ones currently in operation are at Delta, California (near the source at Mount Shasta), at Keswick (near Redding), Colusa (about halfway down the river),

, and

Freeport Freeport, a variant of free port, may refer to: Places United States *Freeport, California *Freeport, Florida *Freeport, Illinois *Freeport, Indiana *Freeport, Iowa *Freeport, Kansas *Freeport, Maine, a New England town **Freeport (CDP), Maine, the ...

. The Freeport gauge, which sits just downstream of Sacramento, provides a relatively good metric of the annual outflow from the Sacramento River Basin. The average flow between 1949 and 2013 was . The maximum recorded flow was on February 19, 1986; the lowest was on October 15, 1977. Flow in the Yolo Bypass, a relief channel designed to carry a portion of the flood waters in order to protect the Sacramento area, is not measured by the Freeport gauge. A separate gauge on the bypass recorded an average throughput of between 1939 and 2013, mostly from December–March. The highest recorded flow was on February 20, 1986. During the dry season of July through September, the bypass carries low to zero flow. Although the Sacramento River nominally begins near Mount Shasta, the true hydrological source of the Sacramento River system is the Pit River, which is by far the largest of the three rivers flowing into Shasta Lake. At the USGS Montgomery Creek gauge, the average flow of the Pit River was for the period 1966–2013. By comparison, the Sacramento River at Delta gauge, a few miles above Shasta Lake, recorded an average of for the period 1945–2013. The McCloud River had an average discharge of for the 1967–2013 period. Since the 1960s, the McCloud River flow has been reduced and the Pit River flow increased due to diversion of water for hydropower generation; however the total volume of water entering Shasta Lake remains the same. Before Shasta Dam was built, the volcanic springs feeding the Pit and McCloud Rivers provided the majority of river flow in dry summers when the Upper Sacramento and other tributaries slowed to a trickle.

Monthly combined discharge of Sacramento River at

and Yolo Bypass near

Woodland A woodland () is, in the broad sense, land covered with trees, or in a narrow sense, synonymous with wood (or in the U.S., the '' plurale tantum'' woods), a low-density forest forming open habitats with plenty of sunlight and limited shade (see ...

(cfs)
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Watershed

The Sacramento River's watershed is the largest entirely in California, covering much of the northern part of the state. The

(closed) Goose Lake drainage basin in southern

, however, has been known to overflow into the Sacramento River system during particularly wet years. The Sacramento River basin generally lies between the Sierra Nevada and Cascade Range on the east and the Coast Ranges and Klamath Mountains in the west, although the part of the basin drained by the Pit River extends east of the Cascades. The Pit River, has the distinction of being one of three rivers that cut through the main crest of the Cascades; its headwaters rise on the western extreme of the

Basin and Range Province The Basin and Range Province is a vast physiographic region covering much of the inland Western United States and northwestern Mexico. It is defined by unique basin and range topography, characterized by abrupt changes in elevation, alternatin ...

, east of major Cascade volcanoes such as Mount Shasta and Lassen Peak. The other two are the

Klamath River The Klamath River (Karuk: ''Ishkêesh'', Klamath: ''Koke'', Yurok: ''Hehlkeek 'We-Roy'') flows through Oregon and northern California in the United States, emptying into the Pacific Ocean. By average discharge, the Klamath is the second larges ...

and Columbia River. By discharge, it is the second-largest contiguous U.S. river draining into the Pacific, after only the Columbia River, which has almost ten times the flow of the Sacramento. The

Colorado River The Colorado River ( es, Río Colorado) is one of the principal rivers (along with the Rio Grande) in the Southwestern United States and northern Mexico. The river drains an expansive, arid watershed that encompasses parts of seven U.S. s ...

, which reaches the

Gulf of California The Gulf of California ( es, Golfo de California), also known as the Sea of Cortés (''Mar de Cortés'') or Sea of Cortez, or less commonly as the Vermilion Sea (''Mar Bermejo''), is a marginal sea of the Pacific Ocean that separates the Baja C ...

just south of the US-Mexico border near the southeast part of the state, is far larger than the Sacramento in terms of length and drainage area but has a slightly smaller flow. The Sacramento, when combined with the Pit, is also one of the longest rivers in the United States entirely within one state—after

Alaska Alaska ( ; russian: Аляска, Alyaska; ale, Alax̂sxax̂; ; ems, Alas'kaaq; Yup'ik: ''Alaskaq''; tli, Anáaski) is a state located in the Western United States on the northwest extremity of North America. A semi-exclave of the U.S ...

's Kuskokwim and

Texas Texas (, ; Spanish language, Spanish: ''Texas'', ''Tejas'') is a state in the South Central United States, South Central region of the United States. At 268,596 square miles (695,662 km2), and with more than 29.1 million residents in 2 ...

Trinity The Christian doctrine of the Trinity (, from 'threefold') is the central dogma concerning the nature of God in most Christian churches, which defines one God existing in three coequal, coeternal, consubstantial divine persons: God the ...

. The major drainage basins bordering that of the Sacramento are that of the Klamath in the north, the San Joaquin and Mokelumne to the south and the Eel River in the west. The Russian River also lies to the west and the endorheic (closed) Honey Lake and Eagle Lake basins to the north. On the east side are many endorheic watersheds of the Great Basin including the

Truckee River The Truckee River is a river in the U.S. states of California and Nevada. The river flows northeasterly and is long.U.S. Geological Survey. National Hydrography Dataset high-resolution flowline dataThe National Map accessed October 20, 2012 Th ...

and

Carson River The Carson River is a northwestern Nevada river that empties into the Carson Sink, an endorheic basin. The main stem of the river is long although the addition of the East Fork makes the total length , traversing five counties: Alpine County ...

. Parts of the Sacramento watershed come very close to, but do not extend past, the border of California and

Nevada Nevada ( ; ) is a state in the Western region of the United States. It is bordered by Oregon to the northwest, Idaho to the northeast, California to the west, Arizona to the southeast, and Utah to the east. Nevada is the 7th-most extensive, ...

Physiography

The basin's diverse geography ranges from the glacier-carved, snowcapped peaks of the Sierra Nevada to the sea-level (and often lower) marshes and farmlands of the Sacramento-San Joaquin Delta. The highest point is at Mount Shasta, a dormant

stratovolcano A stratovolcano, also known as a composite volcano, is a conical volcano built up by many layers (strata) of hardened lava and tephra. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile with a summit crater and p ...

near the headwaters of the Sacramento River. The Sierra Nevada peaks generally decrease in height from south to north—from over in the headwaters of the American River near

Lake Tahoe Lake Tahoe (; was, Dáʔaw, meaning "the lake") is a freshwater lake in the Sierra Nevada of the United States. Lying at , it straddles the state line between California and Nevada, west of Carson City. Lake Tahoe is the largest alpine lake ...

, to in Lassen County where they adjoin the Cascade Range. On the west side, the Coast Ranges are the opposite, increasing in height to almost in the north. The arid volcanic plateaus in the northeast, which are characterized by alternating hills and large sedimentary basins, typically lie at elevations of . Most of the Sacramento Valley is below in elevation; in its lower course, the Sacramento River drops only about per mile. Between the bajadas or alluvial slopes extending from the foothills of the Sierra Nevada and Coast Ranges, are the low floodplains of the Sacramento River. The river flows at an elevation somewhat higher than the surrounding terrain due to deposits of sediment over millennia that created raised banks (essentially natural

levee A levee (), dike (American English), dyke (Commonwealth English), embankment, floodbank, or stop bank is a structure that is usually earthen and that often runs parallel to the course of a river in its floodplain or along low-lying coastl ...

s). The banks separate the river from the lowlands to the east and west that once served as vast overflow basins during winter storms, creating large areas of seasonal

wetland A wetland is a distinct ecosystem that is flooded or saturated by water, either permanently (for years or decades) or seasonally (for weeks or months). Flooding results in oxygen-free (anoxic) processes prevailing, especially in the soils. The ...

s. Since the 19th century, artificial levee systems have been constructed to enable farming in the fertile flood plain. Today there are of irrigated farmland in the Sacramento Valley. Due to the reduction of the floodplain area, the speed of flood flow in the Sacramento River has increased, creating a significant hazard for the farms and towns along its course. By the early 20th century engineers had realized not all the floodplains could be safely reclaimed, leading to the intentional creation of flood bypasses where development is limited to annual crops and recreational uses. Further south, much of the Delta region is actually below sea level: subsidence caused by wind erosion and

intensive farming Intensive agriculture, also known as intensive farming (as opposed to extensive farming), conventional, or industrial agriculture, is a type of agriculture, both of crop plants and of animals, with higher levels of input and output per unit of ...

have caused the land in the delta to gradually sink since the late 19th century. Many of the delta islands would be underwater if not for the maintenance of the levees and pumps that keep them dry. Some of the "islands" are now up to below the adjacent channels and sloughs.

Land use

The Sacramento River watershed is home to about 2.8 million people; more than two-thirds live within the

Sacramento metropolitan area The Greater Sacramento area refers to a metropolitan region in Northern California comprising either the U.S. Census Bureau defined Sacramento–Roseville–Arden-Arcade metropolitan statistical area or the larger Sacramento–Roseville combine ...

. Other important cities are

, Redding, Davis and

. The Sacramento River watershed covers all or most of Shasta, Tehama, Glenn,

Butte __NOTOC__ In geomorphology, a butte () is an isolated hill with steep, often vertical sides and a small, relatively flat top; buttes are smaller landforms than mesas, plateaus, and table (landform), tablelands. The word ''butte'' comes from a F ...

, Plumas, Yuba, Sutter,

Lake A lake is an area filled with water, localized in a basin, surrounded by land, and distinct from any river or other outlet that serves to feed or drain the lake. Lakes lie on land and are not part of the ocean, although, like the much lar ...

and Yolo Counties. It also extends into portions of Siskiyou, Modoc,

Lassen Lassen is a Danish and Norwegian patronymic surname meaning "son of Lars" (equivalent of Laurentius), and thus a parallel form of the more common surname Larsen. Notable people with the surname include: * Anders Lassen (1920–1945), a Danish reci ...

(in Oregon),

Sierra Sierra (Spanish for "mountain range" and "saw", from Latin '' serra'') may refer to the following: Places Mountains and mountain ranges * Sierra de Juárez, a mountain range in Baja California, Mexico * Sierra de las Nieves, a mountain range i ...

, Placer,

El Dorado El Dorado (, ; Spanish for "the golden"), originally ''El Hombre Dorado'' ("The Golden Man") or ''El Rey Dorado'' ("The Golden King"), was the term used by the Spanish in the 16th century to describe a mythical tribal chief (''zipa'') or kin ...

Sacramento ) , image_map = Sacramento County California Incorporated and Unincorporated areas Sacramento Highlighted.svg , mapsize = 250x200px , map_caption = Location within Sacramento ...

, Solano and Contra Costa Counties. The river itself flows through Siskiyou, Shasta, Tehama, Butte, Glenn, Colusa, Sutter, Yolo, Sacramento, Solano and Contra Costa, often forming boundaries between the counties. Many of the mountainous regions of the watershed are administered by the U.S. Forest Service. The Sacramento River watershed includes large areas of coniferous forests in the Mendocino and

Trinity National Forest Trinity National Forest was established as the Trinity Forest Reserve by the U.S. Forest Service in California on April 26, 1905 with . It became a National Forest on March 4, 1907. On July 1, 1908 it gave up some acreage to California National Fo ...

s in the Coast Ranges, Shasta and Lassen National Forests in the southern Cascades and the Plumas, Tahoe and

Eldorado National Forest Eldorado National Forest is a U.S. National Forest located in the central Sierra Nevada mountain range, in eastern California. Geography Most of the forest (72.8%) lies in El Dorado County. In descending order of land area the others counties ...

s on the western slopes of the Sierra Nevada. The watershed also has Lassen Volcanic National Park, which covers centered on Lassen Peak, the southernmost Cascade volcano. Whiskeytown-Shasta-Trinity National Recreation Area, which is over in size, straddles much of the upper Sacramento and

Rivers, and is named for the three local reservoirs (Shasta Lake,