The Pit River is a major river draining from northeastern California into the state's Central Valley. The Pit, the Klamath and the Columbia are the only three rivers in the U.S. that cross the Cascade Range. The longest tributary of the Sacramento River, it contributes as much as eighty percent of their combined water volume into the Shasta Lake reservoir; the junction of their Shasta Lake arms is northeast of Shasta Dam. The main stem of the Pit River is long, and some water in the system flows to the Sacramento River measuring from the Pit River's longest source. The Pit River drains a sparsely populated volcanic highlands area in Modoc County's Warner Mountains, passing through the south end of the Cascade Range in a deep canyon northeast of Redding. The river is so named because of the semi-subterranean permanent winter homes and large 'sweat houses' that the Pit River Tribe dug, and their pit traps for game that came to water at the river. The river is a popular destination for fishing, fly fishing, and rafting in its lower reaches, and is used to generate hydroelectricity in the powerhouses below Fall River Mills where the Pit and Fall rivers join, and at Shasta Dam. It is also used extensively for irrigation and conservation purposes. Course The Pit River rises in several forks in Modoc, Lassen and Shasta counties in the northeastern corner of California. The South Fork Pit River - West Valley Creek - Cedar Creek source originates just southeast of Buck Mountain in the Warner Mountains, in the extreme southeastern corner of the Modoc National Forest west of the California–Nevada border. The South Fork is formed from the confluence of several creeks in Jess Valley northeast of Madeline and flows west through a narrow canyon, past Likely, then generally north through a broad ranching valley where its waters are diverted for irrigation and waterfowl conservation via an extensive system of canals. The long North Fork - Linnville Creek tributary begins southeast of the town of Davis Creek, near Goose Lake. It flows generally south-southwest, joining the South Fork from the north near Alturas. Although Goose Lake is generally considered the terminal sink of an endorheic basin, it will overflow into the Pit River during floods; however this has not occurred since 1881 due to large diversions of water for agriculture. The combined river flows west-southwest in a winding