Biology Reference
In-Depth Information
Confluence of the Sacramento and San Joaquin rivers in the delta below Rio Vista,
before they flow together into San Francisco Bay. (Dr. William Bowen, California
Geographical Survey, Northridge)
The confluence of the Sacramento and San Joaquin rivers is located
near the town of Rio Vista. It's such a wide, flat place that the meeting
point of these two waterways is difficult to see from a boat or the shore. A
few tule islands poke out of the shallows here and there, hinting at the
enormous freshwater marsh that once filled the delta. Below this indistinct
confluence the North Bay receives waters from the Napa and Petaluma
rivers, both of which are strongly influenced by tides. In the South Bay, the
only major freshwater input is from the Guadalupe River, which, unlike all
the other rivers, flows from west to east out of the coastal ridgelands.
All of these rivers are dammed save one. The Cosumnes flows for a
mere 80 miles from 8,000 feet above sea level to its confluence with the
Mokelumne River between Sacramento and Stockton. As the last free-
flowing river in the bay watershed, it's one of the few places where
scientists can get an unfettered sense of the natural water flow pattern, or
hydrograph.
Most of the rivers in the bay watershed also no longer spread out over
their banks onto floodplains. The natural seasonal flooding throughout
the watershed that once created valley topography, imported new soil,
