The Whitewater River run in the Alpine Lakes Wilderness Boundary to Confluence with East Fork Foss River in Washington state is a popular destination for whitewater enthusiasts. The ideal streamflow range for this section of the river is between 500-1500 cfs. At this level, the rapids are exciting and challenging, but not overly dangerous.

The class rating for this section of the river is Class III-IV, with some Class V rapids during high water. The segment mileage is approximately 8.5 miles long, with a put-in at the Alpine Lakes Wilderness Boundary and a take-out at the confluence with the East Fork Foss River.

Specific rapids and obstacles on this section of the river include the Entrance Rapid, the Waterfall Rapid, the Cocytus Rapid, and the Exit Rapid. These rapids offer a mix of technical challenges and big drops, making it an exciting run for experienced paddlers.

There are specific regulations in place for the Alpine Lakes Wilderness Boundary, including a permit system for overnight camping and a strict pack it in, pack it out policy for all trash and waste. Additionally, all paddlers must wear a life jacket and helmets are recommended for the more challenging rapids.