A HYDROGEOCHEMICAL EXAMINATION OF WEST HAWAIʻI'S WATER CYCLE

Simple item page
dc.contributor.advisor Lautze, Nicole C.
dc.contributor.author Tachera, Diamond
dc.contributor.department Earth and Planetary Sciences
dc.date.accessioned 2022-07-05T19:58:28Z
dc.date.available 2022-07-05T19:58:28Z
dc.date.issued 2022
dc.description.degree Ph.D.
dc.identifier.uri https://hdl.handle.net/10125/102218
dc.subject Hydrologic sciences
dc.subject Atmospheric chemistry
dc.subject Geochemistry
dc.subject aquifer management
dc.subject dissolved ions
dc.subject groundwater
dc.subject Hawaiʻi Island
dc.subject recharge
dc.subject stable isotopes of water
dc.title A HYDROGEOCHEMICAL EXAMINATION OF WEST HAWAIʻI'S WATER CYCLE
dc.type Thesis
dcterms.abstract Groundwater, sourced from precipitation, is the main source of drinking water in the State of Hawaiʻi. Understanding Hawaiʻi’s groundwater system is critical to understanding future water security. With increasing development, decreasing rainfall, and sea level rise, the uncertainty of Hawaiʻi’s water resource security is a growing concern. The overarching goal of this dissertation is to address the source, flow, and interconnectivity of Hawaiian aquifer systems. This dissertation identified relationships between precipitation and groundwater using stable isotopic compositions of water, flow and connectivity of groundwater aquifers using relative abundances of geochemical parameters, and the relationship between geochemical abundances and spatial distribution. The second chapter evaluates the isotopic and chemical compositions of rainfall from central to leeward Hawaiʻi Island. The study collected cumulative rainfall samples at regular intervals over a 28-month period from 20 stations spanning a range of elevations across this region, and determined average isotopic and dissolved ion compositions in those samples. The study period included an extreme weather event (Hurricane Lane), a major volcanic eruption at Kīlauea in 2018, and the nearly complete cessation of long-term volcanic emissions following that eruptive event. Consistent with previous literature, results show long-term variability through the establishment of an enhanced local meteoric water line (LMWL) for West Hawaiʻi. Additionally, results of stable isotope compositions and bulk ion deposition highlight how extreme events, such as volcanic eruptions and hurricanes, can affect the chemistry of precipitation. The results from this study can be used to better quantify and characterize precipitation, which is the ultimate source of Hawai‘i’s groundwater. Groundwater chemistry studies utilize the occurrence of dissolved ions and other geochemical parameters to determine source, quality, flow, and interconnectivity of aquifers. In groundwater chemistry studies focused on island and coastal environments, a salinity correction is routinely applied, which subtracts the fraction of ocean water from a mixed fresh- and salt- water system in order to focus on fresh-water processes. The third chapter identifies challenges associated with accurate identification of the ocean water fraction in groundwater in a location where dissolved ion contribution can occur through processes that include seawater intrusion, seaspray deposition, wastewater, and hydrothermal reactions. Further exacerbating this challenge is the complex subsurface hydrogeologic environment of West Hawaiʻi Island. The simplistic end-member values for fresh and ocean water currently used in salinity corrections proved challenging for this region. Instead, the study finds the use of end-members chosen from within probable groundwater flow paths produces better results (less frequent over corrections). In addition, this study finds that alkalinity analyses cause higher charge balance errors in groundwater with lower ion concentrations. Charge balance errors may be a good check of quality for datasets, but are not definitive in determining whether a dataset is viable for further geochemical analyses. The fourth chapter uses the geochemical datasets and analyses from previous chapters to better understand areas of recharge as well as the interconnectivity of groundwater aquifers in West Hawaiʻi. The research utilized two methods to calculate groundwater recharge elevations: point-source and fully-integrated recharge. The utilization of two methods constrained the possible range of recharge elevations from Hualālai, Mauna Kea, and Mauna Loa volcanoes. In many cases, the recharge from Hualālai volcano is not isotopically depleted enough to account for the isotopic compositions of groundwater found in the Hualālai aquifer systems. More depleted recharge from Mauna Loa or Mauna Kea volcanoes are additionally needed to account for the isotopically-depleted groundwater. In addition, recharge crosses current aquifer management boundaries used for groundwater resources. The final chapter explores inequalities in funding structures for scientific research. The current academic and research systems are rooted in colonization and continue to perpetuate the exploitation of Indigenous lands and peoples. As the geoscience field works towards a more diverse, equitable, and inclusive environment, leadership from funding agencies must recognize the burden of broader impacts on Indigenous scientists, and the additional devaluing of community engagement and other labor necessary for equitable scientific research practices. Enacting steps for accountability and encouraging best practices in community-driven research are two ways that, as a scientific community, we can raise our standards of ethical research and develop reciprocity and respect, and repair relationships.
dcterms.extent 199 pages
dcterms.language en
dcterms.publisher University of Hawai'i at Manoa
dcterms.rights All UHM dissertations and theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission from the copyright owner.
dcterms.type Text
local.identifier.alturi http://dissertations.umi.com/hawii:11294
Files
Original bundle
Now showing 1 - 1 of 1
No Thumbnail Available
Name:
Tachera_hawii_0085A_11294.pdf
Size:
7.74 MB
Format:
Adobe Portable Document Format
Description:
Download
Collections
Ph.D. - Earth and Planetary Sciences