The word "渭河" is formed by combining the character "渭", which is the name for a specific river, with the character "河", which means "river", resulting in a compound that explicitly identifies that watercourse as the Wei River.
Word Definition - 渭河
wèi héWei River in Shaanxi through the Guanzhong Plain 關中平原|关中平原[guān zhōng píng yuán]