Dams, based on the systems of Koshayis and Nodotto, are widespread across the smaller rivers dotting Wajahe land. The purpose of these dams is to place further controls upon seasonal flooding - though the flood periods of the Great River are regular and predictable, this is not always true of its many tributaries. They also create reservoirs to act as water storage in the case of a drought, and irrigation systems plug directly into these. These dams come with fish-ladders, which allow for upstream migration of the salmon - essential not only for the food source they represent but also for the integrity of The Afterlife. Dams often have a bridge built atop them, serving as a primary crossing over the river for that portion. These bridges are tall wooden arches, and typically made with as small a slope as possible and with thick, sturdy supports (in case the bridge is wider than the dam) to allow for easy horse and wagon crossings.