Honjō Dam
Honjō Dam is a concrete gravity dam that stores and regulates water from the Nikō River. It was constructed in 1918 by the Imperial Navy in response to the expanding naval base’s growing demands for water. Until the dam’s completion in 1918, the citizens of Kure depended on low-quality well water, which was vulnerable to exposure to harmful bacteria. After the dam was built, the Navy made part of this new water supply available to Kure’s residents, thus providing them with a more reliable water source.
At the time of its construction, Honjō Dam was said to be the largest dam in the East. The dam is 97 meters long, 3.64 meters wide, and 25 meters high. The reservoir behind it holds a maximum volume of 1.96 million cubic meters of water. The exterior of the dam, as well as its large staircase (with 96 steps), are made from cut granite. Honjō Dam has been in continual use since it was first built, yet very little repair work has been necessary. This durability testifies to the relative sophistication of naval architectural technology at the time the dam was built.
At the foot of the dam, a gatehouse regulates the volume of water released by the dam by measuring its flow rate. This water is then sent downstream to the Miyahara Water Purification Plant. A round well next to the gatehouse can be used to draw water directly from the Nikō River when the water level of the reservoir is low. In 2017, a new propeller water circulation system was installed to further improve water quality by inhibiting the growth of algae on the surface of the water. The dam’s reservoir is also protected by a small shrine dedicated to a Shinto water deity, which has been erected on an artificial island near the dam.
The Honjō Dam facility was designated a national Important Cultural Property in 1999. It is the first water-supply structure to have received this designation while still in use. In 2005, the Water Resources Environment Center certified the Honjō Dam reservoir as one of the “Selected 100 Dam Lakes” across Japan, in recognition of its scenery, historical significance, and sophisticated architecture. The dam is opened to visitors every spring when the cherry trees bloom along the dam’s base.
