Sacramento River - Watershed

Watershed

The largest river in California, the Sacramento River's watershed covers a large portion of the northern portion of the state and is situated almost entirely within California's boundaries, with the historically rare exception of the northernmost Pit River, which once received outflow of the now endorheic (closed) Goose Lake drainage basin in southern Oregon. Almost the entire basin lies between the Sierra Nevada and Cascade Range on the east and the Coast Ranges and Klamath Mountains in the west. The Sacramento's longest tributary, the Pit River, has the distinction of being one of three rivers that cut through the main crest of the Cascades; its headstreams rise on the western extreme of the Basin and Range Province, east of major Cascade volcanoes such as Mount Shasta and Lassen Peak. The other two are the Klamath River 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 seven times the flow of the Sacramento. The Colorado River, which reaches the Gulf of California just south of the US-Mexico border near the southeast part of the state, is far larger than the Sacramento by both length and drainage area but has a slightly smaller flow. After the Colorado and San Joaquin, it has the third-largest drainage basin in California. The Sacramento, when combined with the Pit, is also one of the longest rivers in the United States entirely within one state—after Alaska's Kuskokwim and Texas' Trinity.

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

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 agricultural lands of the Sacramento-San Joaquin Delta. The highest point is Mount Shasta, a stratovolcano that stands 14,104 feet (4,299 m) high, near the headwaters of the Sacramento River. Subsidence caused by wind erosion and other phenomena slowly caused the land in the delta to sink for years; many of the delta islands would be underwater if not for the maintenance of the levees that keep them dry. Many of the "islands" are now up to 25 feet (7.6 m) below the surrounding water. The Sierra Nevada generally decreases in height from south to north—from 10,000 to 11,000 feet (3,000 to 3,400 m) near Lake Tahoe, east of the American River, to just 6,000 feet (1,800 m) as they merge into the Cascades and Modoc Plateau in the Lassen Peak area; however, on the west side, the Coast Ranges area is the opposite, increasing from 2,000 to 3,000 feet (610 to 910 m) in the south to just shy of 10,000 feet (3,000 m) in the north. The volcanic plateaus in the northeast, which comprise relatively flat terrain, typically lie at elevations of 3,000 to 5,000 feet (910 to 1,500 m). Most of the Sacramento Valley is below 300 feet (91 m) in elevation; in its lower course, the Sacramento River drops only about 1 foot (0.30 m) per mile.

Most of the Sacramento River's valley is intensely cultivated, with some 2,000,000 acres (8,100 km2) of irrigated farmland. Medium to dense forests occupy most of the mountains, many of which lie on U.S. Forest Service lands. Sparse grasslands and high desert stretch to the north. Along with the agrarian base, the basin is also home to about 2.8 million people, far more than half of whom live within the Sacramento metropolitan area. Other important cities are Chico, Redding, Davis and Woodland. The Sacramento River watershed covers all or most of Shasta, Tehama, Glenn, Butte, Plumas, Yuba, Sutter, Lake and Yolo Counties. It also extends into portions of Siskiyou, Modoc, Lassen, Lake (in Oregon), Sierra, Nevada, Placer, El Dorado, 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.

The Sacramento River watershed includes large areas of forests such as the Mendocino and Trinity National Forests in the Coast Ranges, Shasta and Lassen National Forests in the southern Cascades and the Plumas, Tahoe and Eldorado National Forests on the western slopes of the Sierra Nevada. The watershed also has Lassen Volcanic National Park, which covers 106,000 acres (430 km2) centered around Lassen Peak, the southernmost Cascade volcano. Whiskeytown-Shasta-Trinity National Recreation Area, which is over 200,000 acres (810 km2) in size, straddles much of the upper Sacramento and Trinity Rivers, centering around three popular man-made lakes–Shasta Lake, Trinity Lake and Whiskeytown Lake. Many other state parks and recreation areas lie within the watershed.