The Whitewater River Run in California flows from the Hoover Wilderness Boundary to the Humboldt-Toiyabe National Forest Boundary, covering a distance of approximately 22 miles. This river run is rated as a Class III-IV run, and is best suited for experienced kayakers and rafters.

The ideal stream flow range for the Whitewater River Run is between 400 and 1,000 cubic feet per second (cfs), which typically occurs during the spring snowmelt or after summer thunderstorms. The river features several challenging rapids, including "Confluence Rapid," "The Squeeze," and "The Narrows." The latter is a particularly challenging section, with steep drops and tight turns.

It is important to note that the Whitewater River Run is located within the Hoover Wilderness, and as such, there are strict regulations in place to protect the area. Only non-motorized watercraft are permitted on the river, and all visitors must obtain a wilderness permit before entering the area. Additionally, visitors are required to follow Leave No Trace principles and pack out all trash.

Overall, the Whitewater River Run is a challenging and exciting whitewater experience for experienced kayakers and rafters. It is important to always check stream flow levels before embarking on this run, and to follow all regulations in order to protect the wilderness area.