Until the end of the war, except for a few districts, drinking water was provided by wells. Under the U.S. military administration, however, the water supply system was updated to pump water directly into distribution pipes, using the former Japanese military reservoir and wells drilled in the Okumura area as water sources. (Ref. 1)

Following reversion of the islands, the stable supply of good quality water for the rapidly expanding population was a priority issue for the development of Ogasawara. New wells were drilled on Chichijima to secure sufficient water supply, and water distribution was also changed to a method in which water is first sent from the water source to a distribution tank, from where it is supplied through water pipes. (Ref. 1) From fiscal year 1982 onwards measures were taken to reduce trihalomethanes, including aeration of dam water and the new installation of activated carbon treatment facilities and chemical injection rooms, etc., and advanced water purification treatment was started. In March 2015 a new water treatment plant was completed. (Ref. 2) On Hahajima, three wells and a water purification system were installed to ensure a minimum water supply of 100 m3 per day. Similarly to Chichijima, since 1982 measures have been taken to reduce trihalomethanes. At the end of fiscal 2013, all waterworks operations were transferred to Chichijima and operations as Ogasawara Village Small Scale Public Water Supply began from fiscal year 2014. (Ref. 2)

Ref. 1: Nanpo Doho Engokai, Ogasawara no genkyo: Fu Ogasawara henkan no kiroku (Current Situation of Ogasawara: Record of the Reversion of Ogasawara), 1969, pp. 23-24.

Ref. 2: Tokyo Metropolitan Ogasawara Branch Office, Kannai Gaiyo (Overview of the Jurisdiction), 2019 ed., pp.219-223.