Conventional hydrogeologic framework models used to compute ocean island sustainable yields and aquifer storage neglect the complexity of the nearshore and offshore submarine environment. However, the onshore aquifer at the island of Hawai‘i exhibits a notable volumetric discrepancy between high-elevation freshwater recharge and coastal discharge. In this study, we present a novel transport mechanism of freshwater moving from onshore to offshore through a multilayer formation of water-saturated layered basalts with interbedded low-permeability layers of ash/soil. Marine electromagnetic imaging reveals ∼35 km of laterally continuous resistive layers that extend to at least 4 km from west of Hawai‘i’s coastline, containing about 3.5 km³ of freshened water. We propose that this newly found transport mechanism of fresh groundwater may be the governing mechanism in other volcanic islands. In such a scenario, volcanic islands worldwide can use these renewable offshore reservoirs, considered more resilient to climate change-driven droughts, as new water resources.

用于计算海洋岛屿可持续产量和含水层存储的常规水文地质框架模型忽略了近岸和近海海底环境的复杂性。但是，夏威夷岛的岸上含水层在高海拔淡水补给量和沿海排泄量之间表现出明显的体积差异。在这项研究中，我们提出了一种新型的淡水输送机制，它是通过水饱和的层状玄武岩与灰分/土壤互层的低渗透层的多层形成而从陆上转移到近海的。海洋电磁成像揭示了约35 km的横向连续电阻层，这些电阻层从夏威夷海岸线以西至少延伸4 km，其中约3.5 km ³新鲜的水。我们认为，这种新发现的淡水输送机制可能是其他火山岛的治理机制。在这种情况下，全世界的火山岛都可以将这些可再生的近海水库用作新的水资源，这些水库被认为对气候变化驱动的干旱更具抵抗力。