The Old River was once the main channel of the San Joaquin until navigation (Stockton Deepwater Shipping Channel) and flood control projects in the late 19th and 20th century fixed the San Joaquin to its present course past Stockton.

[1] The river is lined with levees that prevent flooding of the adjacent Delta islands, many of which lie below sea level.

The reverse flow also confuses migrating salmon in the San Joaquin River which may have contributed to the decline of the species in the 20th century.

[5] A pumping station on Old River east of Discovery Bay provides fresh water to Los Vaqueros Reservoir via pipeline.

The Old River also skirts the Franks Tract State Recreation Area, a former Delta island that is now submerged and forms a lake.