The Somo River (sometimes called the Big Somo) is a tributary of the Tomahawk River, with headwaters in Price County, but mostly lying in Lincoln County. The source is the confluence of Somo Creek and Little Somo Creek in the unincorporated community of Clifford. The river flows approximately east-southeast, and terminates in Lake Mohawksin. Prior to the existence of Lake Mohawksin, which floods the confluence, the Somo flowed into the Tomahawk, just a few hundred yards up stream of its confluence with the Wisconsin.