Autonomous long-term gamma-spectrometric monitoring of submarine groundwater discharge trends in Hawaii

Dulai, Henrietta; Kameník, Jan; Waters, Christine A.; Kennedy, Joseph; Babinec, J.; Jolly, James A.; Williamson, M.R.

doi:10.1007/s10967-015-4580-9

Cited by 26 publications

(26 citation statements)

References 18 publications

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“…In this case, the reservoirs’ volumes would be substantially higher than the minimum values estimated above. These reservoirs of freshwater offshore Hawai‘i are most likely renewable, as implied from point-source fluxes of freshwater from the seafloor to the water column ( 20 , 21 ).…”

Section: Discussionmentioning

confidence: 99%

Marine electrical imaging reveals novel freshwater transport mechanism in Hawai‘i

et al. 2020

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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.

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Section: Discussionmentioning

confidence: 99%

Marine electrical imaging reveals novel freshwater transport mechanism in Hawai‘i

et al. 2020

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“…Although differences in precipitation are expected to impact SGD flux and associated N+N loads among locations and seasons [1, 84], these results suggest that differences in land use and associated nutrient loading to CGW may exert an equal or greater amount of control on the level of available nutrients in the water column than variations SGD flux. For example, Dulai et al [84] found that maximal SGD rates during the wet season in Kiholo Bay, Hawaiʻi were only 2.3 times greater than the minimum rate of SGD flux, which was measured during the dry season.…”

Section: Discussionmentioning

confidence: 99%

“…For example, Dulai et al [84] found that maximal SGD rates during the wet season in Kiholo Bay, Hawaiʻi were only 2.3 times greater than the minimum rate of SGD flux, which was measured during the dry season. In contrast, differences in SGD flux and N concentration in CGW among our study locations varied across one order of magnitude and two orders of magnitude, respectively [53].…”

Section: Discussionmentioning

confidence: 99%

Impact of Submarine Groundwater Discharge on Marine Water Quality and Reef Biota of Maui

et al. 2016

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Generally unseen and infrequently measured, submarine groundwater discharge (SGD) can transport potentially large loads of nutrients and other land-based contaminants to coastal ecosystems. To examine this linkage we employed algal bioassays, benthic community analysis, and geochemical methods to examine water quality and community parameters of nearshore reefs adjacent to a variety of potential, land-based nutrient sources on Maui. Three common reef algae, Acanthophora spicifera, Hypnea musciformis, and Ulva spp. were collected and/or deployed at six locations with SGD. Algal tissue nitrogen (N) parameters (δ15N, N %, and C:N) were compared with nutrient and δ15N-nitrate values of coastal groundwater and nearshore surface water at all locations. Benthic community composition was estimated for ten 10-m transects per location. Reefs adjacent to sugarcane farms had the greatest abundance of macroalgae, low species diversity, and the highest concentrations of N in algal tissues, coastal groundwater, and marine surface waters compared to locations with low anthropogenic impact. Based on δ15N values of algal tissues, we estimate ca. 0.31 km2 of Kahului Bay is impacted by effluent injected underground at the Kahului Wastewater Reclamation Facility (WRF); this region is barren of corals and almost entirely dominated by colonial zoanthids. Significant correlations among parameters of algal tissue N with adjacent surface and coastal groundwater N indicate that these bioassays provided a useful measure of nutrient source and loading. A conceptual model that uses Ulva spp. tissue δ15N and N % to identify potential N source(s) and relative N loading is proposed for Hawaiʻi. These results indicate that SGD can be a significant transport pathway for land-based nutrients with important biogeochemical and ecological implications in tropical, oceanic islands.

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“…Examples of the latter approach include autonomous water-proofed gammaspectrometry systems that are passive and do not require power-demanding water pumping (Tsabaris et al, 2012). A mobile underwater in-situ gamma-ray spectroscopy system was successfully applied for coastal surveys of radon and 224 Ra as a ship-deployed tow system (Patritis et al, 2018) and was also developed for long-term deployment on a permanently moored station where it recorded hourly radon measurements for multiple years (Dulai et al, 2016 and see Figure 5). These novel technologies bring the ability to perform longer and higher resolution SGD monitoring in diverse field settings, which will help document trends in SGD in different hydrogeologic and climatic settings, under extreme weather events, excessive groundwater pumping trends, and sea level rise scenarios.…”

Section: Geochemical Methodologymentioning

confidence: 99%

“…(D) Hourly radon measurements over multiple years (a 9-month record shown here) allows us to evaluate SGD dynamics over tidal and seasonal time scales. Data from Dulai et al (2016).…”

Section: Geochemical Methodologymentioning

confidence: 99%

Submarine Groundwater Discharge: Updates on Its Measurement Techniques, Geophysical Drivers, Magnitudes, and Effects

Taniguchi

Dulai

Burnett

et al. 2019

Front. Environ. Sci.

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The number of studies concerning Submarine Groundwater Discharge (SGD) grew quickly as we entered the twenty-first century. Many hydrological and oceanographic processes that drive and influence SGD were identified and characterized during this period. These processes included tidal effects on SGD, water and solute fluxes, biogeochemical transformations through the subterranean estuary, and material transport via SGD from land to sea. Here we compile and summarize the significant progress in SGD assessment methodologies, considering both the terrestrial and marine driving forces, and local as well as global evaluations of groundwater discharge with an emphasis on investigations published over the past decade. Our treatment presents the state-of-the-art progress of SGD studies from geophysical, geochemical, bio-ecological, economic, and cultural perspectives. We identify and summarize remaining research questions, make recommendations for future research directions, and discuss potential future challenges, including impacts of climate change on SGD and improved estimates of the global magnitude of SGD.

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Autonomous long-term gamma-spectrometric monitoring of submarine groundwater discharge trends in Hawaii

Cited by 26 publications

References 18 publications

Marine electrical imaging reveals novel freshwater transport mechanism in Hawai‘i

Marine electrical imaging reveals novel freshwater transport mechanism in Hawai‘i

Impact of Submarine Groundwater Discharge on Marine Water Quality and Reef Biota of Maui

Submarine Groundwater Discharge: Updates on Its Measurement Techniques, Geophysical Drivers, Magnitudes, and Effects

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