The Fall River, a major tributary of the Pit River, is located in north-eastern Shasta County approximately 60 miles northeast of Redding in the Fall River Valley. The Fall River Valley rests between the Sierra Nevada and Cascade Mountain ranges with Mt. Shasta visible to the northwest and Mt Lassen to the south.
The Fall River Watershed lies within the volcanic terrain of the Modoc Plateau geomorphic province. The Fall River is the largest sub-drainage in the middle reach of the Pit River. The river drains a 612-square mile area, but due to the porous volcanic nature of the region, most of the stream flow originates from springs within the valley.
The Fall River is a moderate sized, slow moving, meandering meadow stream. Flows are relatively stable throughout the year due to the stream’s spring origins. At the USGS gage near Dana, the river has a summer flow of about 450 cfs.
The river itself originates at Thousand Springs (elevation approximately 3,320 ft), a series of springs rising from lava beds northeast of Dana, and flows 21.3 miles in a southerly direction before joining the Pit River below Fall River Mills. Bear Creek represents the only significant surface flow contribution to the Fall River. The Tule River, another tributary to the Fall River, originates as a series of large springs known as Ahjumawi Lava Springs.
Extreme flows recorded for the 1958 to 1967 period were 353 and 3,910 cfs (USGS survey, 1968). Peak flows originate primarily from flood events on Bear Creek. Bear Creek flows into Fall River just below Thousand Springs, but is intermittent in its lower reaches during the summer.
At 5.2 miles below Thousand Springs, Spring Creek contributes to the river about 200 cubic feet per second of pristine spring water. Below Spring Creek, the river increases to about 600 cubic feet per second and broadens to about 100 ft. The river meanders the remaining 16 miles through an open valley. Approximately 7 miles below Spring Creek, Fall River is joined by the Tule River, which flows out of Big Lake and Eastman (Tule) Lake. These tributaries bring the total summer flow to about 1,200 cfs and channel widths to about 300 ft in the lower 9.3 miles of Fall River above the Pit No. 1 Intake.
Wild Trout Habitat
The large volumes of spring water inflow maintain Fall River water temperature at near optimum ranges for trout production, even during mid-summer. At the Island Road Bridge, mid-summer temperatures are generally in the low to mid 50s F and, near Glenburn and the Pit No. 1 Intake, in the low to mid 60s.
Big Lake Complex
Big Lake is used primarily for waterfowl hunting and supports a warm water fishery year round and a trout fishery during the general trout season. Horr Pond supports a similar sport fishery, including largemouth black bass, and brown bullheads. The Tule River supports bass, bullheads, and trout for anglers each year, and the Little Tule River contains self-sustaining populations of rainbow and brown trout. Recreation use of these areas is for the most part by means of an access site (Rat Farm) located in the WHIP near the shore of Big Lake.
The lava springs feeding the Big Lake Complex, the headwaters of the Tule River, are the source of 75% of the water in the Fall River and supply about 85% of the flow of the Pit River during the summer months. The Complex consists of five contiguous bodies of water: Big Lake, Horr Pond, the Upper Tule River, the Little Tule River, and Eastman Lake, whose combined surface area exceeds 1100 acres.
PG&E owns five miles of the south shore of Big Lake, 2 miles along the east shore of the Little Tule River, and most of the inundated area. A levee on this shoreline protects the reclaimed McArthur Swamp owned by PG&E from inundation. Much of the northern shoreline is in Ahjumawi Lava Springs State Park. There is only one public boat launching site, the Rat Farm site on the south shore.
McArthur Swamp is a 7,400-acre area of reclaimed wetlands and open water north of the town of McArthur and south of Big Lake and the Tule River. It provides valuable waterfowl habitat on the Pacific Flyway and is also grazed. PG&E proposes to donate McArthur Swamp and the nearby parcel acquired by a land trade with State Parks (see Lake Britton) to the Fall River Resource Conservation District, which is to manage it subject to a strict easement. The easement will preserve the wildlife habitat and other environmental values of McArthur Swamp, while allowing continuation of grazing, which will be carefully controlled to benefit waterfowl habitat.