The discovery of the freshwater submarine off the coast of Hawai’i raises hopes for islands around the world

Illustration showing a multilayered conceptual model of the fresh groundwater transport mechanism from land to open sea in Hawaii. Credit: University of Hawai’i

According to a University of Hawai’i study with important implications for volcanic islands around the world, twice as much fresh water is stored off the island of Hawai’i than previously thought. A vast freshwater reservoir within the submarine southern flank of the Hualālai aquifer was mapped by UH researchers with the Hawai’i EPSCoR ‘Ike Wai project. The groundbreaking results, published in Advances in science, reveal a new way in which large volumes of freshwater are transported from onshore subsea aquifers to offshore ones along the coast of the island of Hawai’i.

This mechanism can provide alternative renewable freshwater resources to volcanic islands around the world. “Their separate freshwater lens trials, stacked on top of each other, near the Kona coast of Hawai’i, profoundly improves the prospects for sustainable development on the volcanic islands,” said UH Mānoa School of Ocean and Earth. Science and Technology (SOEST) Dean Brian Taylor.

Porpoise system graphic.jpg Caption: illustration of the CSEM (Marine Controlled Source Electromagnetic) system towed to the surface called Porpoise. Credit: University of Hawai’i

Paradigm shift

Through the use of source-controlled marine electromagnetic imagery, the study revealed the land-to-open movement of freshwater through a multilayered formation of basalts embedded between ash and soil layers, diverging from previous groundwater models of the latter. area. Conducted as part of the National Science Foundation-supported Ike Wai project, research affiliate professor Eric Attias led the marine geophysics campaign.

Eric Attias (center) deploying the Towed Surface Marine Controlled Source Electromagnetic System (CSEM) off the island of Hawai’i. Credit: University of Hawai’i

“Our findings provide a paradigm shift from conventional hydrological conceptual models that have been widely used by multiple water studios and organizations in Hawaii and other volcanic islands to calculate sustainable yields and aquifer storage over the past 30 years,” he said. Attias. “We hope our discovery will improve future hydrological models and, consequently, the availability of clean fresh water in volcanic islands.”

The Towed To Surface Marine Controlled Source Electromagnetic System (CSEM) in the ocean off the island of Hawai’i. Credit: University of Hawai’i

Co-author Steven Constable, a professor of geophysics at the Scripps Institution of Oceanography, who developed the controlled source electromagnetic system used in the project, said: ‘I have spent my entire career developing marine electromagnetic methods like the one used here. gratifying to see the equipment 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 to the open sea. “

Kerry Key, associate professor at Columbia University employing electromagnetic methods to create images of various terrestrial ocean structures, which are not involved in this study, said: “This new electromagnetic technique is a revolutionary tool for convenient reconnaissance investigations to identify regions containing freshwater aquifers, before of more expensive drilling efforts to directly sample interstitial waters. It can also be used to map the lateral extent of any already identified aquifers in isolated wells. “

Twice as much water

Donald Thomas, a geochemist at SOEST’s Hawai’i Institute of Geophysics and Planetology who also worked on the study, said the results confirm twice the presence of much larger amounts of stored groundwater than previously thought.

“Understanding this new groundwater mechanism … is important to better manage groundwater resources in Hawaii,” said Thomas, who leads the Humu? Ula Groundwater Research, which found another large freshwater supply on the island of Hawai’i several years ago.

Eric Attias, research affiliate professor at the University of Hawai’i, at Wailupe Beach Park in O’ahu. Credit: University of Hawai’i

It is suggested that offshore freshwater systems similar to those flanking the Hualālai Aquifer are present for the Isle of O’ahu, where the electromagnetic imaging technique has not yet been applied, but, if demonstrated, could provide a concept completely new to manage fresh water resources.

The study proposes that this recently discovered transport mechanism may be the governing mechanism in other volcanic islands. With offshore reservoirs considered more resilient to droughts due to climate change, volcanic islands around the world can potentially consider these resources in their water management strategies.

Reference: 25 November 2020, Advances in science.
DOI: 10.1126 / sciadv.abd4866

This project is supported by the National Science Foundation EPSCoR Program Award OIA # 1557349.