California has over 100 rivers, tributaries, and creeks. The two greatest rivers in northern and central California — in terms of flow of water and economic importance — are the Sacramento and San Joaquin rivers.
The Sacramento River has its origins near Mount Shasta, in the northern part of the state. It flows some 400 miles south through California's great Central Valley. Near Sacramento, it turns west to empty into the Sacramento River Delta and then into Suisun Bay, San Pablo Bay, San Francisco Bay, and the Pacific Ocean.
As we saw earlier, the average annual runoff in the Sacramento River basin is 22 million acre-feet — about one-third of the state's total runoff.