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FROM RECHARGE TO REEF: ASSESSING THE SOURCES, QUANTITY, AND TRANSPORT OF GROUNDWATER ON TUTUILA ISLAND, AMERICAN SAMOA

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Title:FROM RECHARGE TO REEF: ASSESSING THE SOURCES, QUANTITY, AND TRANSPORT OF GROUNDWATER ON TUTUILA ISLAND, AMERICAN SAMOA
Authors:Shuler, Christopher K.
Contributors:El-Kadi, Aly I. (advisor)
Earth and Planetary Sciences (department)
Keywords:Hydrologic sciences
Environmental science
Coastal nutrient impact
Collaborative modeling
Groundwater contamination
show 3 moreGroundwater modeling
Submarine Groundwater Discharge
Water budget
show less
Date Issued:2019
Publisher:University of Hawai'i at Manoa
Abstract:On high volcanic islands, groundwater resources are essential for maintaining human habitability and for sustaining coastal and aquatic ecosystems. On the island of Tutuila in American Samoa, groundwater is the only source of drinking water to over 90% of the island’s approximately 60,000 residents. However, the island’s population faces numerous water quality and water quantity challenges including well salinization, aquifer contamination by anthropogenic sources, and environmental water quality degradation. The purpose of this work is to contribute to new understanding of these issues in tropical island environments, and specifically for the island of Tutuila, by exploring a wide range of hydrogeologic phenomena through presentation of six individual chapters; each of which targets a small set of the territory’s most critical water resources management questions. This dissertation commences in its Introduction and concludes in its Appendices with a comprehensive literature review on the topic of American Samoan hydrogeology, which is contextualized as a conceptual hydrogeologic model that supports the other studies presented here as individual chapters. Chapter 2 details the application of geochemical and biological tracers to determine the mechanism of contamination in wells on Tutuila’s Tafuna-Leone Plain that have caused one of the longest standing boil-water-notices in U.S. history. Chapter 3 explores surface water - groundwater interaction in one of the island’s steepest watersheds and uses natural environmental tracers to quantify submarine groundwater discharge (SGD) and associated nutrient loading. This study shows how comprehensive, tracer-based field assessment of SGD can be complimented by watershed modeling to develop a conceptual hydrogeologic model of groundwater-surface water interaction and to quantify coastal nutrient loading by multiple hydrologic pathways. Chapter 4, expands upon the techniques used in Chapter 3 and also examines macroalgal tissue parameters to quantify the impact of land-based, nutrient-pollution sources on four separate watersheds spanning a human-impact gradient. Chapter 5 presents the development and results of a water budget assessment of Tutuila Island, specifically designed to estimate spatially distributed groundwater recharge, and including effects of future climate change. Chapter 6 presents a distinctive approach to groundwater modeling; instead of focusing on model results, this chapter focuses on the vertically-integrated, cloud-based, and process oriented collaborative modeling framework applied jointly between researchers and water utility staff at the American Samoa Power Authority to develop a cooperative groundwater modeling process. As a case study, this chapter shows how the collaborative approach can be applied to develop modeling products that have greater longevity and applicability to the needs of resource managers. Each of the individual chapters in this dissertation is linked through the common goal of seeking to provide researchers, water resource managers, and policy makers with applied science tools that can be used to improve water resources sustainability in American Samoa and throughout the Pacific.
Description:Ph.D. Thesis. Ph.D. Thesis. University of Hawaiʻi at Mānoa 2019
Pages/Duration:310 pages
URI:http://hdl.handle.net/10125/63106
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.
Appears in Collections: Ph.D. - Earth and Planetary Sciences


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