The Fall River watershed drains a area that originates from Thousand Springs, and is largely spring-fed, with
Bear Creek providing the only significant precipitation-related surface flow to the river. Bear Creek rises at a source elevation over and flows east to join Fall River at Thousand Springs at an elevation of . Its other two main tributaries, Spring Creek and the
Tule River, are also spring-fed, with the latter originating in the Ahjumawi Lava Springs system. Fall River is a moderate sized, slow moving, meandering meadow stream with a mean gradient of less than 1 ft./mile. Spring Creek joins Fall River 5.2 miles below Thousand Springs, and seven miles below Spring Creek, Fall River is joined by Tule River. Since 1922 the river has been dammed before its confluence with the Pit River and diverted through a tunnel under Saddle Mountain to the Pit No. 1 Intake powerhouse, one of many hydroelectric dams on the Pit River. ==See also==