川 brook 천, 江 river 강
According to Naver Dictionary, 천 川 is a stream, creek, or brook and 강 江 is a river. Put ice 冰 and 川 together and you get glacier 冰川. Incheon in South Korea is 仁川. Sichuan Province in China is 四川. Makes it easy for me to remember the sound of 川 천 cheon.
Han River is 한강 hangang. Gangnam 강남 district in Seoul, South Korea is 江南.