Attias Eric, Thomas Donald, Sherman Dallas, Ismail Khaira, Constable Steven
Hawai'i Institute of Geophysics and Planetology, School of Ocean and Earth Science and Technology, University of Hawai'i at Mānoa, Honolulu, HI, USA.
Frontier Geosciences, North Vancouver, BC, Canada.
Sci Adv. 2020 Nov 25;6(48). doi: 10.1126/sciadv.abd4866. Print 2020 Nov.
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 km 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储量的传统水文地质框架模型忽略了近岸和近海海底环境的复杂性。然而，夏威夷岛的陆上含水层在高海拔淡水补给和海岸排放之间存在显著的体积差异。在本研究中，我们提出了一种新的淡水输送机制，即淡水通过具有夹灰/土壤低渗透层的水饱和层状玄武岩多层结构从陆上向近海移动。海洋电磁成像显示，约35公里的横向连续电阻层从夏威夷海岸线以西至少延伸4公里，包含约3.5公里的淡化水。我们认为，这种新发现的新鲜地下水输送机制可能是其他火山岛的主导机制。在这种情况下，全球的火山岛可以将这些被认为对气候变化引发的干旱更具恢复力的可再生近海储层用作新的水资源。
