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‘Ohe‘o Gulch or Seven Sacred Pools located in Haleakala National Park.

Water Resources in Hawai‘i and the Pacific

The University of Hawai‘i established the Water Resources Research Center (WRRC) in 1964 in response to the Federal Water Resources Research Act of 1964. It concentrates on addressing the unique water and wastewater management problems facing people in the Pacific, and serves the state of Hawai‘i as well as other Pacific islands and elsewhere by researching water-related issues distinctive to these areas. The center is part of the National Institutes for Water Resources which represents every U.S. state as well as Washington, D.C. and three U.S. territories.

The main focuses of the center are to: coordinate and conduct research to identify, characterize, and quantify water-related problems in Hawai‘i; assist Pacific island and Asian governments facing water problems similar to those in Hawai‘i; and facilitate access to interdisciplinary expertise within the university to enhance understanding of environmental problems and to identify effective solutions.

Hawai‘i ’s Water Resources by Dr. Darren T. Lerner, Director, University of Hawai‘i Sea Grant College Program and Water Resources Research Center (Interim)

Water is essential for all life. Water is inextricably linked to energy and food in a nexus that binds each to the other. Water is the key to sustainability and resilience.

Fresh water or wai played an integral role in traditional Hawaiian culture and lifestyle and was believed to be sacred. Ancient Hawaiians believed that water, along with land, belonged only to the gods. Water was upheld as an essential source of life and was key to the wealth of the Hawaiian people and as such waiwai refers to abundance or great amounts of wealth. The importance of water and its role in the health of individuals and communities was understood to a degree such that Hawaiians used water resources sustainably and shared these resources equitably. So strong was this understanding that the Hawaiian word for law is intimately tied to water as kanewai, which means “sharing water equally.”

We are still learning about the complete hydrologic cycle here in Hawai‘i. Certainly, we understand that northeasterly trade winds drive moisture saturated clouds onto the Islands that then move inland where mountains and forests force the moisture to condense and rain to fall. Rainwater percolates into the earth through volcanic soil and is stored in diked rock compartments and basal aquifers. Direct recharge from rain combined with the waters that overflow from diked rocks form the subterranean “basal freshwater lens.” It takes many years in some areas for rainwater to penetrate underground into our islands’ freshwater lenses, which supply most of the water needs for approximately 1.4 million people living in Hawai‘i.

From the Rainfall Atlas of Hawai‘i it can be estimated that 2 billion gallons of water in the form of rain falls each day on O‘ahu alone2. While that may sound like a tremendous amount of water, uncertainties about aspects of the hydrologic cycle and the absence of a more scientifically robust understanding of how water “works” leave us with an incomplete picture of water supply and water quality in Hawai‘i. The need to increase understanding and improve management of our water resources sustainably demands multidisciplinary approaches to obtaining fact-based data to better inform citizens, communities and decision makers about water use, planning and policies.

To address these needs we seek answers to questions posed through hypothesis testing and scientific inquiry. These questions form the foundation of much research conducted at the University of Hawai‘i and include: by whom and where is fresh water being used, in what quantities and from what sources; are we overdrawing or contaminating our underground sources; how much water is required for a steadily increasing population, a sustainable economy and a growing agricultural sector; how can we adapt to the impacts of climate change on water availability; how do we accurately price water (i.e., environmentally and economically sustainable); does our current water infrastructure, regulations and knowledge allow for the safe use of reclaimed water; can we restore our stream flows and still maintain healthy local economies while protecting homes and lives; who holds what water “rights” and where do those rights conflict? The University of Hawai‘i Water Resources Research Center (WRRC) has contributed major unbiased research efforts over the more than 50 years since its inception. Projects have dealt with assessing drinking and other water resources in terms of quantity, quality, social aspects, and economics. In addition to answering critical research questions, the general objectives are to meet federal requirements or solve specific problems. Now both WRRC and University of Hawai‘i Sea Grant College Program are continuing the efforts towards research, outreach, and education activities to address these questions in support of a sustainable Hawai‘i.

Submarine Groundwater Discharge by Dr. Henrietta Dulai, Associate Professor, Department of Geology and Geophysics, University of Hawai‘i at Mānoa

Groundwater is our primary water supply, but we humans are not the only ones depending on it. Hawaiian aquifers are leaky and copious amounts of groundwater pour out at the shoreline where coastal springs sustain vibrant coastal ecosystems. This process is called submarine groundwater discharge (SGD). Our research found that there is at least as much groundwater flow as stream discharge to every embayment or stretch of coastline on O‘ahu. While the impacts of streams and episodic nutrient-rich storm runoff on coastal water quality have been relatively well documented, non-point source pollution via groundwater discharge has a chronic impact on coastal ecosystems that is more difficult to evaluate.

Nutrient concentrations in aquifers have significantly increased on O‘ahu due to agricultural activities and the consequences of urbanization, such as leaky septic and sewer systems, wastewater injection to coastal aquifers, commercial and domestic use of fertilizers, and pesticides, etc. These all contribute excess nutrients, but also pesticides, pharmaceuticals, personal care products, and other contaminants of emerging concern. We use geochemical signatures to trace the source of various SGD components. Nutrients, for example, originate from a range of sources including natural soil, septic systems, and treated wastewater injected to the coastal aquifer.

In our most recent project on the south shore of O‘ahu we focused on assessing the effects of SGD and its components on coastal water quality. We found that SGD directly affects coastal pH, causing local ocean acidification, and offsets the expected marine nitrogen-to-phosphorus ratios. In addition, excess nutrient delivery by SGD amplifies the photosynthesis respiration cycle in coastal ecosystems and we can link large variations in coastal dissolved oxygen, pH, and nutrients to groundwater fluxes. The effects of these phenomena on the reefs are yet to be documented, and we haven’t even begun looking at the effects of emerging contaminants like pharmaceuticals and personal care products.

Our research provides a deeper understanding of coastal hydrological processes (when, where, and how much groundwater flows to the coast), contents of groundwater, as well as how these affect coastal water quality. We have state-of-the-art tools that allow us to detect and quantify these processes. We collaborate with colleagues from other disciplines to investigate the many consequences of excessive groundwater withdrawal, water re-use in the coastal regions, sea-level rise, climate change, and pollution on SGD and coastal ecosystems. We look at SGD as a resource that supports the needs of coastal communities.

Water Resources Research Center Highlight: Dr. Aly El-Kadi, Associate Director

Dr. Aly El-Kadi is a professor of hydrology in the University of Hawai‘i at Mānoa, Department of Geology and Geophysics, and associate director of the Water Resources Research Center. His research has dealt with assessing effects of climate change and land-use practices on water resources sustainability; watershed assessment and modeling; modeling multiphase flow and transport of hydrocarbons; bioremediation in tidal aquifers; contamination by agricultural, cesspool sources, and arsenic.

A snapshot of his current and most recent research efforts include:

  • Assessing Groundwater Sustainability in Jeju Island, Korea
  • Assessed the decline in water levels and spring flows and increase in salinity as indicators of groundwater sustainability.
  • Prioritizing water-quality management efforts in Tutuila, American Samoa

Wells in the island’s most productive aquifers are subject to contamination from agricultural chemicals, biological pathogens, and nutrients from human and pig waste disposal systems. Nitrogen-source partitioning in the Tafuna-Leone Plain of the island is used to identify potential non-point contaminant sources and assess their relative impact on groundwater resources. The research found that on-site disposal systems were the most detrimental to groundwater resources and should be prioritized in future water management efforts.

  • Evaluating surface water harvesting in Honolulu, Hawai‘iEvaluating surface water harvesting is a water conservation method the Honolulu Board of Water Supply is considering to augment groundwater

supply in Honolulu, Hawai‘i, aquifers. Such aquifers are likely to experience long-term recharge reduction due to climate change impacts, leading to decreased head levels and reduced potable-water volumes. This research is investigating the potential use of a harvesting system in the Nuÿuanu Reservoir No. 4 area. The general objective of the project is to address the likely effect on water quantity and quality by the subsurface injection process. That work aims at estimating the harvesting amounts and identifying the reservoir operation strategy.

Professor El-Kadi’s current work primarily focuses on assessing the sustainability of water resources to assist water resource managers in the decision making process. In general, water sustainability related studies employ watershed models in estimating elements of the water budget, including recharge and surface runoff, for watersheds under current and future land-use and climate conditions. Current projects cover sites on O‘ahu (He‘eia and Nu‘uanu area watersheds), and on Tutuila (Fagaalu and other watersheds). The results are not only useful as tools for management decisions, but also provide helpful insights regarding model application in challenging environments under scarcity of data. Professor El-Kadi is a member of the ‘Ike Wai science team, a $20M project funded by the National Science Foundation Experimental Program to Stimulate Competitive Research (NSF EPSCoR) (see next article). He is tasked with groundwater modeling, which is a central and critical part of the efforts connecting the data collection, visualization, and scenario development teams.

UH Water Resources Research Center and Sea Grant Partner on $20 M Water Sustainability Project By Cindy Knapman, Hawai‘i Sea Grant Communications Leader

Most of us take it for granted that we will turn on our tap and have access to clean, safe drinking water. Especially in Hawai‘i, where the rainwater slowly percolates through the volcanic soil and is naturally purified by the time it reaches the aquifers and eventually our water glasses. But Hawai‘i is an island state with a rapidly growing population, changing land use practices including many new housing developments, and an uncertain future with regard to the impacts climate change. What do we need to do today to ensure that we still have access to this vital resource tomorrow, the next day, and in the years to come?

The first critical steps are to have a clear understanding of how much water is contained in Hawai‘i’s aquifers, the rate at which the aquifers are recharged, and the direction and rate at which it flows. Sounds easy? It’s not. We do not currently understand Hawai‘i’s complex underground aquifer systems and how geological formations impact the flow of the water. In many areas the lava flows have formed extremely large and permeable aquifers, and in others, factors such as buried ash and soil, thick lava that pooled in preexisting depressions, and multiple other factors impede the amount and flow of the groundwater. Without a clear understanding of how much water is available we cannot plan for the future.

To help the state address this critical issue the National Science Foundation Experimental Program to Stimulate Competitive Research (NSF EPSCoR) awarded $20 million dollars to the University of Hawai‘i System (UH) to engage in a five-year groundbreaking study of water sustainability issues through a collaboration called ‘Ike Wai. The project name ‘Ike Wai symbolizes knowledge (‘Ike) of water (wai) which informs values, policies, and practices for managing this resource. ‘Ike Wai will assemble UH, state and federal agencies, and community partners to address critical gaps in the understanding of Hawai‘i’s water supply that limits decision-making, planning, and crisis responses. It will also bring together a diverse team of hydrologists, geophysicists, modelers, volcanologists, engineers, visualization experts, social scientists, and educators, and hire seven new faculty in the UH system to specifically focus on this project.

Groundwater models are essential tools to understand and assess the flow and amount of water contained in Hawai‘i’s aquifers as well as potential contaminant transport. Towards this objective, the research team has engaged one of the top visualization experts at UH to create new high-resolution 3D maps of geologic structures. A new technology nicknamed CyberCANOE, or Cyber-enabled Collaboration Analysis Navigation and Observation Environment, is a large multi-screen display that will be used by the scientists and stakeholders to see the 3D images and data such as complex geophysical aquifer models and water flow diagrams. With new data to test theories, one of the goals is to better characterize aquifer conditions and connectivity and evaluate accurate bathymetry of groundwater.

The University of Hawai‘i Water Resources Research Center (WRRC), the University of Hawai‘i Sea Grant College Program (Hawai‘i Sea Grant), and the Institute of Hawaiian Language Research and Translation bring critical research expertise and stakeholder input and engagement to bear on solving issues related to water availability and sustainability for the ‘Ike Wai project. In addition to bringing invaluable university knowledge and expertise, these programs provide the capacity for understanding traditional knowledge and history of our water resources and close ties with other parts of the Pacific, which will inform as well as benefit from the results of this groundbreaking collaboration.

Dr. Darren T. Lerner, Hawai‘i Sea Grant director and also interim director of the WRRC, noted “Understanding all dimensions of our water resources in Hawai‘i including quantity, quality, and use, is critical to our mission of increasing our ability to live sustainably. Water is inseparably linked to the production of energy and food and this funding ultimately serves to boost our existing efforts across the UH system to address all of these issues for our state, the region, and the world.”

The Water Resources Research Center at UH serves Hawai‘i and American Samoa, and is Hawai‘i’s link in a National Institutes for Water Resources network consisting of 54 programs nationwide, including American Samoa, Guam, Puerto Rico, and the U.S. Virgin Islands. Dr. Aly El-Kadi, WRRC’s Associate Director, is leading the groundwater modeling effort, which is a critical part of ‘Ike Wai. In addition, this project will provide the opportunity to hire three new tenure- track WRRC faculty shared jointly with UH’s School of Ocean and Earth Science and Technology, College of Engineering, and College of Social Sciences. These faculty are not only essential to achieve the project’s objectives, but they will greatly expand and enhance WRRC’s expertise and capacity. The engagement with Hawai‘i Sea Grant will link ‘Ike Wai to Sea Grant’s extensive network of 33 coastal and Great Lakes programs across the U.S., Puerto Rico, and Guam as well as other parts of the Pacific such as American Samoa, the Republic of the Marshall Islands, and Pohnpei, where Hawai‘i Sea Grant faculty are based.

Increasing Access to Safe Drinking Water on Hawai‘i Island By Dr. Mary J. Donohue, Program Specialist, Hawai‘i Sea Grant

Mohala i ka wai ka maka o ka pua.

Unfolded by the water are the faces of the flowers.

-Hawaiian proverb

Water is the driver of Nature.

-Leonardo Da Vinci

There’s plenty of water in the universe without life, but nowhere is there life without water.

-Sylvia A. Earle

Beyond the more intensively developed areas of the state of Hawai‘i’s “Big Island,” a rural sensibility emerges with all the attendant charms–but also challenges–that face non-urban communities. Here, on the state’s expansive namesake Island of Hawai‘i, tens of thousands of residents, and visitors alike, do not have access to municipal water and must rely on other sources for their potable water needs.1 Prominent among these is the capture of rainwater in cisterns for household use. Well-designed, installed, and maintained rainwater catchment systems can provide clean water for drinking and other uses. However, poorly maintained or designed systems potentially pose a health risk including exposure to waterborne illness. Unlike a number of states, Hawai‘i has no governmental oversight for ensuring the safety of rainwater catchment systems; owners and end-users are responsible for knowing how to use rainwater catchment systems and maintain their water source in a safe and appropriate manner.

Hawai‘i Island-based Sea Grant extension staff, Chantal Chung, who herself grew up using rainwater catchment in Hawai‘i Island’s South Kona District, recognized a need among the island’s rural communities for more information on the safe use and maintenance of rainwater catchment systems. Chung partnered with the University of Hawai‘i Sea Grant College Program’s (Hawai‘i Sea Grant) Dr. Mary J. Donohue to develop a project that would bring Sea Grant outreach on rainwater catchment into rural communities, and provide catchment system users and owners with free water testing kits to better understand the quality of their stored water. Donohue and Chung collaborated with the non-profit American Rainwater Catchment Systems Association (ARCSA) as well as enlisted the help of a recently retired, and much beloved, world expert on rainwater catchment living on the Big Island, Patricia S. H. Macomber.

With their team assembled, which also included Sea Grant extension faculty based on the islands of O‘ahu and Maui, Donohue and Chung embarked on an effort that would take them to every corner of the Big Island, conducting 11 free workshops on rainwater catchment in nine communities over 2015. Workshops included presentations that addressed rainwater catchment system components, maintenance, and waterborne diseases. More than 3000 people were also reached by project outreach at 15 island events such as farmer’s markets and festivals. Critically, 10,000 free DIY (“do-it-yourself”) water testing kits were distributed to community members by project personnel, collaborators, and volunteers. Nearly 400 free printed copies of the 51-page Guidelines on Rainwater Catchment Systems for Hawaii1 were distributed as well as made available online (

Fact-based outreach on rainwater catchment could not be more crucial. Hawai‘i Island’s population increased 25 percent between 2000 and 20102; with the greatest increases occurring in districts heavily dependent upon private rainwater catchment systems. Population increases have not been mirrored by an expansion of County of Hawai‘i water system service. Concurrently, concerns about water-borne illnesses are increasing. An apparent increase in number and severity of human cases of rat lungworm disease on Hawai‘i Island is troubling; one putative transmission vector for this disease is the infestation of catchment tanks by slugs or snails carrying the parasite.3 The 2015-2016 dengue fever outbreak on Hawai‘i Island was also of concern to rainwater catchment systems users and owners, as uncovered or otherwise accessible cisterns may serve as breeding areas for infected mosquitos that transmit this disease.4 It is worth noting that the Aedes aegypti and Aedes albopictus mosquitoes that can transmit dengue fever can also transmit the emerging Zika virus.5 Thus, outreach on the utility of a properly fitted and effective cistern cover, appropriate pre- and post cistern filtration, chemical and/or ultraviolet light water disinfection, and other best practices has the potential to reduce exposure to serious illnesses.

Presently, Hawai‘i Sea Grant is seeking avenues and collaborative funding opportunities to support extension activities on sustainable water practices, with a focus on rainwater catchment. Ultimately, our aim is to provide ongoing outreach activities related to all aspects of water use and stewardship.

This project was made possible by the collaboration of numerous organizations and individuals including the USDA National Institute of Food and Agriculture program, University of Hawai‘i College of Tropical Agriculture and Human Resources and ARCSA, among others.


1Macomber, Patricia S.H. Guidelines on Rainwater Catchment Systems for Hawaii. College of Tropical Agriculture and Human Resources, University of Hawai‘i at Mänoa. 2010.

2Population and Economic Projections for the State of Hawai‘i to 2040. Research and Economic Analysis Division, Department of Business, Economic Development and Tourism. March 2012.

Hawai‘i County Water Use and Development Plan Update-Hawaii Water Plan Final Report. Department of Water Supply Hawai‘i County. 2010.

Population Brief-Trends in the Western U.S.-Hawaii. Western Rural Development Center publication. Utah State University. 2010.

3Hawai‘i State Department of Health Disease Investigation Branch, January 29, 2009; and see University of Hawai‘i at Hilo Daniel K. Inyoue College of Pharmacy rat lungworm FAQ webpage:

4Hawai‘i State Department of Health, Controlling Mosquito Breeding in Rainwater Catchment Systems and “Dry” Injection Wells 24 December 2015 (

5State of Hawai‘i Department of Health, Disease Outbreak Division and