The Beaver River is a river in western Utah, 110 miles long, that drains to Sevier Lake via the Sevier River. The river starts in the Tushar Mountains, in eastern Beaver County near the town of Beaver, and flows for about 30 miles west as a perennial stream, through the Beaver Valley to the Escalante Desert, where it turns north. The river then continues nort…The Beaver River is a river in western Utah, 110 miles long, that drains to Sevier Lake via the Sevier River. The river starts in the Tushar Mountains, in eastern Beaver County near the town of Beaver, and flows for about 30 miles west as a perennial stream, through the Beaver Valley to the Escalante Desert, where it turns north. The river then continues north for about 80 miles as an ephemeral wash, past Milford into Millard County. Once it reaches the Sevier Desert south of Delta it turns west, joining the Sevier River and emptying into the intermittent, endorheic Sevier Lake.