The Slab Creek section on the South Fork American River almost never has water in it. It is an eight mile stretch between two reservoirs used for power generation. Only when Mother Nature's bounty of rain is too much for the concrete walls to contain does water spill over and return to the natural river bed. So far this year that has occurred only twice and I have had the good fortune and good timing to get on it both times.
Last time (in March) was a two man exploratory run during heavy rains that turned into a high water adventure. More on the stressful side of fun. This time was an eight person group enjoying low flows in nice weather. A very different experience but both were great runs of a beautiful stretch of river. A shame it doesn't exist more frequently.
Helmet cam footage can be found here.