How oahu grts its fresh water?

O'ahu gets its freshwater from underground volcanic rock.

Explanation:

Water that shows itself at O'ahu is filtered through volcanic rock over 25 years before it is shown in glasses of water. The water comes from the equator and is filtered through springs and around volcanoes.

Hawaii tap water is rainwater that is naturally filtered through underground porous volcanic rock for about 25 years before it reaches aquifers. The Honolulu Board of Water Supply says Oahu's municipal water is safe to drink and use, and it does not require treatment by home filtration units.