The Middle Fork has the largest flow, but is subject to numerous hydro-power diversions that often dewater the river bed in summer. The Sand Bar and Mt. Knight runs ( in total), rated "difficult" at Class IV–V+ are dependent on releases from Sand Bar Dam, which only occur when river flow exceeds the capacity of Stanislaus Powerhouse. The average season for this run is only about 3 weeks long, typically in early June. The reach between Donnells Dam and Beardsley Reservoir, known as "Hell's Half Acre", flows through a narrow granite gorge descending 183 feet per mile (35 m/km), including numerous Class V+ (unrunnable) drops; this reach only runs when water is released from Donnells Dam. Due to the increasing popularity of whitewater boating, PG&E has been considering making higher dam releases during the summer.