Ara River System :Ara River Dam Control and Management Office (Saitama Prefecture)
The rainbow was able to be done by water's in the Urayama dam being rolled up because of the strong wind.
The following four purposes are in the Urayama dam. The flood control in the lower river region is done, the shortage of water of the river is prevented, the water service rainwater is sent to Tokyo and Saitama, and electricity is generated.