How many rivers make up the Columbia river?

There are six major rivers that make up the Columbia River System: the Columbia River itself, the Kootenay River, the Pend Oreille River, the Spokane River, the Snake River, and the Yakima River. These six rivers and their tributaries collectively drain an area of over 258,000 square miles (670,000 km²) in the Pacific Northwest region of the United States and Canada.