The Sacramento River's watershed is the largest entirely in California, covering much of the northern part of the state.
The endorheic (closed) Goose Lake drainage basin in southern Oregon, 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, 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 ten 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 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'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 Sacramento River's watershed is the largest entirely in California, covering much of the northern part of the state. The endorheic (closed) Goose Lake drainage basin in southern Oregon, 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, 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 ten 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 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'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.
Sacramento River