More than 4,000 people lived on Ibukijima island according to a blessing from the fishing industry. However, the island had a problem living on. It was the lack of drinking water.
The island consists of pyroxene bedrock. So even during the Great Hanshin-Awaji Earthquake, it hardly shook, while the mainland on the opposite bank suffered damage. However, because of the bedrock, the rain did not percolate and immediately flowed into the sea, making it impossible to obtain natural water. Although it was an island without water, islanders chose to live here because of the proximity to rich fishing grounds.
In order to solve this problem, the island created "rainwater wells" that collect rainwater by drilling through rocks. They used it for everything from drinking water to daily life water.
Each family collected rainwater from their roofs with gutters and stored it in a small private rainwater well, while the island also built large masonry rainwater wells for communal use. However, it was not groundwater but rainwater that had been stored. An old newspaper wrote that carp was released into the well to prevent mosquito larvae, and the islanders filtered with gauze to use as drinking water.
The Hirai Well, which was located in the center of the village, is now covered with concrete. In old photos, it was a stone well with stairs, and they went down to the depth where the water remained to draw water. During a dry season when water ran out, they added the water transported by boat to the well.
In 1973, the island, which had been decoupled from the water supply infrastructure, was freed from its dependence on rainwater since a water supply boat began commuting from the mainland twice a day. However, it didn't supply all the necessary water. They had to wait until 1984, when submarine water pumping began, and the trouble with water completely disappeared.
Even in Japan, which is (believed to be) blessed with water, some people were left out of the myth of water until a short time ago. Surprisingly, when I recently talked with an islander, she still lived on rainwater.