Top three-stream radical (Kangxi #47) — three wavy lines depicting a current. In 巡 the streams give a flowing-along-a-route sense, and the radical indexes the character within Kangxi #47 even though strict modern indexing lists 巡 under 巛/川. Same root family: 川 river, 州 prefecture, 灾 disaster.
Bottom-left walking radical wrapping around the streams — together the pieces depict 'walking along the watercourse,' which is exactly the original sense of 巡: to make a patrol, walking the borders of one's territory like a river follows its banks.
