Where is the yalu river and why is it important

Together with the Tumen River to its east, and a small portion of Paektu Mountain, the Yalu forms the border between North Korea and China and is notable as a site involved in military conflicts such as the First Sino-Japanese War, the Russo-Japanese War, World War II, and the Korean War.

I don't know where it is but it is important because it has a lot of water and most people needs it