וְשֵׁ֨ם הַנָּהָ֤ר הַשְּׁלִישִׁי֙ חִדֶּ֔קֶל ה֥וּא הַֽהֹלֵ֖ךְ קִדְמַ֣ת אַשּׁ֑וּר וְהַנָּהָ֥ר הָֽרְבִיעִ֖י ה֥וּא פְרָֽת׃
셋째 강의 이름은 힛데겔이라 앗수르 동편으로 흐르며 넷째 강은 유브라데더라
Shulchan Arukh, Orach Chayim
Not on every river should you recite the blessing, but rather on the 4 rivers, as it is written "like Chidekel and Euphrates." And he who saw them in a place that wasn't normally walked by people.