Tucannon River salmonid populations (includes mainstem Snake River tributaries: Alkali Flat, Deadman, and Meadow Creeks) The Tucannon River is a Snake River tributary originating in the Blue Mountains of southeast Washington and is located in Columbia and Garfield Counties. The main channel is approximately 58 miles long and drains about 503 square miles before entering the Snake River approximately 3 miles upstream of Lower Monumental Dam. Several major tributaries drain into the main stem including, Pataha Creek, Tumalum Creek, Cummins Creek, Little Tucannon, and Panjab Creek. The Tucannon River supports four populations of threatened species including the Snake River ESU spring Chinook, Snake River fall Chinook, Snake River ESU summer steelhead, and the Columbia River bull trout. All reaches of the Tucannon River are utilized during one or more life stage annually except fall,which only use the lower river. The lower Snake River spring Chinook is currently only found in the Tucannon River, having been extirpated from Asotin Creek. The Tucannon River spring Chinook is a sub-population of the Snake River spring Chinook ESU, which has been listed as threatened under the Endangered Species Act since 1996, and is the primary focus of the Program restoration project. The Tucannon River is the lowest downstream tributary spring Chinook population in the Snake River.