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Illustration showing a multi-layered conceptual model of the mechanism for transporting fresh groundwater from land to sea in Hawaii. Credit: University of Hawaii
According to a University of Hawaii study with important implications for volcanic islands around the world, twice as much fresh water is stored off the island of Hawaii. A large freshwater reservoir in the submarine southern flank of the Hualālai Aquifer has been mapped by UH researchers with the Hawai’i EPSCoR Ike Wai Project. The revolutionary discoveries, published in Scientific advances, reveal a new way of transporting substantial volumes of fresh water from land-based submarine aquifers to submarine aquifers along the coast of the island of Hawaii.
This mechanism can provide renewable alternative freshwater resources to volcanic islands around the world. “Their evidence of separate freshwater lenses, stacked on top of each other, near the Kona coast of Hawaii, profoundly improves the prospects for sustainability on the volcanic islands,” said the Dean of the UH Mānoa School of Ocean and Earth Science and Technology (SOEST). Brian Taylor.
Porpoise system graphic.jpg Caption: Illustration of the surface-towed marine controlled source electromagnetic system (CSEM) called Porpoise. Credit: University of Hawaii
Paradigm shift
Through the use of source-controlled marine electromagnetic imaging, the study revealed the onshore-offshore movement of freshwater through a multi-layered formation of basalts embedded between layers of ash and soil, diverging patterns. groundwater precedents from this area. As part of the National Science Foundation-supported Ike Wai project, Affiliate Research Professor Eric Attias led the marine geophysics campaign.
Eric Attias (middle) deploying the Surface-Towed Marine Controlled Source Electromagnetic System (CSEM) off the island of Hawaii. Credit: University of Hawaii
“Our results provide a paradigm shift from conventional hydrologic conceptual models that have been widely used by multiple studies and water organizations in Hawaii and other volcanic islands to calculate sustainable yields and storage of aquifers at over the past 30 years, ”Attias said. “We hope that our discovery will improve future hydrological models and, therefore, the availability of clean freshwater in volcanic islands.”
The Surface-Towed Marine Controlled Source Electromagnetic System (CSEM) in the ocean off the island of Hawaii. Credit: University of Hawaii
Co-author Steven Constable, professor of geophysics at the Scripps Institution of Oceanography, who developed the source-controlled electromagnetic system used in the project, said: “I have spent my entire career developing marine electromagnetic methods such as the one used here. It is truly gratifying to see the equipment being used for such an impactful and important application. Electrical methods have long been used to study groundwater on land, so it makes sense to extend the application offshore.
Kerry Key, Associate Professor at Columbia university which uses electromagnetic methods to image various oceanic structures on Earth, which are not involved in this study, said: “This new electromagnetic technique is a revolutionary tool for cost-effective reconnaissance surveys to identify regions containing aquifers of freshwater, ahead of more costly drilling efforts to directly sample porewater. It can also be used to map the lateral extent of any aquifer already identified in isolated boreholes. “
Twice as much water
Donald Thomas, a geochemist at SOEST’s Hawaiian Institute of Geophysics and Planetology who also worked on the study, said the results twice confirm the presence of much larger amounts of stored groundwater than is commonly believed. thought before.
“Understanding this new mechanism for groundwater… is important to better manage groundwater resources in Hawai’i,” said Thomas, who leads Project Humu? Ula Groundwater Research, who found another large source of fresh water on the island of Hawaii several years ago.
University of Hawaii Affiliate Research Faculty Eric Attias at Wailupe Beach Park, O’ahu. Credit: University of Hawaii
It is suggested that offshore freshwater systems similar to those bordering the Hualālai aquifer are present for the island of O’ahu, where the electromagnetic imaging technique has not yet been applied, but, if demonstrated, could provide a comprehensive new concept for managing freshwater resources.
The study proposes that this newly discovered transport mechanism could be the driving mechanism in other volcanic islands. With offshore reservoirs considered more resilient to droughts brought on by climate change, volcanic islands around the world have the potential to factor these resources into their water management strategies.
Reference: November 25, 2020, Scientific advances.
DOI: 10.1126 / sciadv.abd4866
This project is supported by the National Science Foundation OIA EPSCoR Program Award # 1557349.
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