Noble gas signatures in the Island of Maui, Hawaii: Characterizing groundwater sources in fractured systems

Water Resources Research
By: , and 

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Abstract

Uneven distribution of rainfall and freshwater scarcity in populated areas in the Island of Maui, Hawaii, renders water resources management a challenge in this complex and ill-defined hydrological system. A previous study in the Galapagos Islands suggests that noble gas temperatures (NGTs) record seasonality in that fractured, rapid infiltration groundwater system rather than the commonly observed mean annual air temperature (MAAT) in sedimentary systems where infiltration is slower thus, providing information on recharge sources and potential flow paths. Here we report noble gas results from the basal aquifer, springs, and rainwater in Maui to explore the potential for noble gases in characterizing this type of complex fractured hydrologic systems. Most samples display a mass-dependent depletion pattern with respect to surface conditions consistent with previous observations both in the Galapagos Islands and Michigan rainwater. Basal aquifer and rainwater noble gas patterns are similar and suggest direct, fast recharge from precipitation to the basal aquifer. In contrast, multiple springs, representative of perched aquifers, display highly variable noble gas concentrations suggesting recharge from a variety of sources. The distinct noble gas patterns for the basal aquifer and springs suggest that basal and perched aquifers are separate entities. Maui rainwater displays high apparent NGTs, incompatible with surface conditions, pointing either to an origin at high altitudes with the presence of ice or an ice-like source of undetermined origin. Overall, noble gas signatures in Maui reflect the source of recharge rather than the expected altitude/temperature relationship commonly observed in sedimentary systems.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Noble gas signatures in the Island of Maui, Hawaii: Characterizing groundwater sources in fractured systems
Series title Water Resources Research
DOI 10.1002/2016WR020172
Volume 53
Issue 5
Year Published 2017
Language English
Publisher American Geophysical Union
Publisher location Washington, D.C.
Contributing office(s) Oregon Water Science Center
Description 16 p.
First page 3599
Last page 3614
Country United States
State Hawaii
Other Geospatial Island of Maui