Steven examined the hologram in silence for several more mils, then pointed at one of the impellers under a river segment. "I don’t think you’ve correctly characterized the river system, Will. This isn’t one river, it’s four. Alternately going in opposite directions. The tributaries and feeders allow the rivers to exchange contents, but if you check the impeller configurations, there are two main flow directions. And note how, at the segment boundaries, the rivers coalesce into four straits running through the mountain barriers. Two in each direction."