 The latter are part of the Confederated Tribes of the Colville, a multi-tribal government in Washington state.The bounds of Okanagan territory are roughly the basin of Okanagan Lake and the Okanagan River, plus the basin of the Similkameen River to the west of the Okanagan valley, and some of the uppermost valley of the Nicola River.The various Okanagan communities in British Columbia and Washington form the Okanagan Nation Alliance, a border-spanning organization which includes American-side Okanogans resident in the Colville Indian Reservation, where the Okanagan people are sometimes known as Colvilles.