| One of the smaller rivers emerging from the Sierra Nevada mountains, this river flows west out of mid-elevation areas northeast of Stockton, travels a short distance across the Central Valley, and merges with the Mokelumne River near Highway 5. This river would not be notable except that it is the last major undammed watercourse entering the Central Valley. Because it is dwarfed by some of the larger rivers emerging from the Sierra, such as the American River or San Joaquin River, it escaped the dam-building craze of the mid 20th century that swept through the area. Because it is free flowing, this river fluxuates in flow much more than its neighboring rivers; something quite important for the animals and plants of the area. The Nature Conservancy, Ducks Unlimited, and other agencies have been buying land adjacent to this river, and restoring them to a more natural state. Currently, there are many acres of unleveed floodplain through which the river can wander, and the acreage is slowly increasing.
There are some very biologically rich areas around this river, which is one of the last places you can see what the inland valleys of California once looked like. Oaks and cottonwoods thrive in the seasonally-flooded areas. The river has a thriving population of salmon which is currently increasing (seasonal flooding offers habitat for juvenile salmon as well as nutrients for feeding). Waterfowl are abundant in these wetlands, and even large animals such as deer, coyotes, and mountain lions inhabit the area.
There is an excellent visitor center found on the preserve; it can be accessed by exiting I-5 on Twin Cities Road heading east, and turning right on the first paved road, immediately before the railroad tracks. Continue down this road for a few miles; the visitor center will be on the left just before the end of the road. | 
