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Distribution of ancient carbon in groundwater and soil gas from degradation of petroleum near the Red Hill Bulk Fuel Storage Facility, O‘ahu, Hawai‘i

The groundwater below the Red Hill Bulk Fuel Storage Facility (the facility) in Oʻahu, Hawaiʻi, contains fuel compounds from past spills. This study used carbon-14 analyses to distinguish fuel-derived carbon from background carbon, along with other biodegradation indicators, to address two goals: (1) determine the extent and migration direction of groundwater affected by residual fuel below the fa

Jared J. Trost, Barbara A. Bekins, Jeanne B. Jaeschke, Geoffrey N. Delin, Daniel A Sinclair, James K Stack, Rylen K. Nakama, Uli'i M. Miyajima, Lhiberty D. Pagaduan, Isabelle M. Cozzarelli

Effects of drought and cloud-water interception on groundwater recharge and wildfire hazard for recent and future climate conditions, Kauaʻi, Oʻahu, Molokaʻi, Maui, and the Island of Hawaiʻi

The Water-budget Accounting for Tropical Regions Model (WATRMod) code was used for Kauaʻi, Oʻahu, Molokaʻi, Maui, and the Island of Hawaiʻi to estimate the spatial distribution of groundwater recharge, soil moisture, evapotranspiration, and climatic water deficit for a set of water-budget scenarios. The scenarios included historical and future drought conditions, and a land-cover condition where s
Alan Mair, Delwyn S. Oki, Heidi L. Kāne, Adam G. Johnson, Kolja Rotzoll

Estimated groundwater recharge for mid-century and end-of-century climate projections, Kaua‘i, O‘ahu, Moloka‘i, Lāna‘i, Maui, and the Island of Hawai‘i

Demand for freshwater in the State of Hawaiʻi is expected to increase by roughly 13 percent from 2020 to 2035. Groundwater availability in Hawaiʻi is affected by a number of factors, including land cover, rainfall, runoff, evapotranspiration, and climate change. To evaluate the availability of fresh groundwater under projected future-climate conditions, estimates of groundwater recharge are needed
Heidi L. Kāne, Alan Mair, Adam G. Johnson, Kolja Rotzoll, James Mifflin, Delwyn S. Oki

Groundwater and surface-water interactions in the He‘eia watershed, O‘ahu, Hawai‘i—Insights from analysis of historical data and numerical groundwater-model simulations

He‘eia and ‘Ioleka‘a Streams in the He‘eia watershed on O‘ahu, Hawai‘i, receive substantial discharge from dike-impounded groundwater. Previous studies indicated that groundwater withdrawals from the watershed affect streamflow. Resource managers and users seek information that can be used to balance the needs of competing uses of groundwater and streamflow in the watershed.In this study, analyses
Scot K. Izuka, Heidi L. Kāne, Kolja Rotzoll

Identifying the relative importance of water-budget information needed to quantify how land-cover change affects recharge, Hawaiian Islands

This report describes a sensitivity analysis of a water-budget model that was completed to identify the most important types of hydrologic information needed to reduce the uncertainty of model recharge estimates. The sensitivity of model recharge estimates for the Hawaiian Islands of Oʻahu and Maui was analyzed for seven model parameters potentially affected by land-cover changes within a watershe
Adam G. Johnson, Alan Mair, Delwyn S. Oki

Availability of groundwater from the volcanic aquifers of the Hawaiian Islands

The islands of Hawaiʻi were built by basaltic shield volcanoes in the Pacific Ocean. These volcanoes formed aquifers that supply hundreds of millions of gallons of fresh water per day to the islands’ residents and diverse industries. Groundwater discharge from the volcanic aquifers to streams and the coast also supports traditional practices and ecosystems. The aquifers' capacity to yield fresh gr
Scot K. Izuka, Kolja Rotzoll

Magnitude and frequency of floods on Kauaʻi, Oʻahu, Molokaʻi, Maui, and Hawaiʻi, State of Hawaiʻi, based on data through water year 2020

Accurate estimates of flood magnitude and frequency are needed to (1) optimize the design and location of infrastructure, including dams, culverts, bridges, industrial buildings, and highways, and (2) inform flood-zoning and flood-insurance studies. The U.S. Geological Survey (USGS), in cooperation with the State of Hawaiʻi Department of Transportation, estimated flood magnitudes for the 50-, 20-,
Jackson N. Mitchell, Daniel M. Wagner, Andrea G. Veilleux

Volcanic aquifers of Hawaiʻi—Contributions to assessing groundwater availability on Kauaʻi, Oʻahu, and Maui

The volcanic aquifers of the Hawaiian Islands supply water to 1.46 million residents, diverse industries, and a large component of the U.S. military in the Pacific. Groundwater also supplies fresh water that supports ecosystems in streams and near the coast. Hawaii’s aquifers are remarkably productive given their small size, but the capacity of the islands to store fresh groundwater is limited bec
Scot K. Izuka, Kolja Rotzoll

Assessment and guidance for using Laser In-situ Scattering and Transmissometry– Stream-Lined 2 (LISST-SL2)

The Laser In-situ Scattering and Transmissometry–Stream-Lined 2 (LISST-SL2) is a second-generation isokinetic river sediment monitoring device that uses laser diffraction to measure suspended-sediment concentration and particle size between 1 and 500 microns in 36 log-spaced bins at a point in a river every second. We compare this latest laser diffraction instrument for suspended-sediment sampling
Muneer Ahammad, Jonathan A. Czuba, Christopher A. Curran

Groundwater-level monitoring from January 17 to March 3, 2022, Hālawa area, O‘ahu, Hawai‘i

A reported fuel release in November 2021 at the Red Hill Bulk Fuel Storage Facility within the naval reservation at Red Hill led to the shutdown of several production wells in the Hālawa area, O‘ahu, Hawai‘i. Red Hill Shaft—one of the high-capacity production wells that shut down—was reactivated on January 29, 2022. Submersible pressure transducers were deployed at 20 wells in the Hālawa area to m
Rylen K. Nakama, Jackson N. Mitchell, Delwyn S. Oki

Long-term groundwater availability in the Waihe‘e, ‘Īao, and Waikapū aquifer systems, Maui, Hawai‘i

Groundwater levels have declined since the 1940s in the Wailuku area of central Maui, Hawai‘i, on the eastern flank of West Maui volcano, mainly in response to increased groundwater withdrawals. Available data since the 1980s also indicate a thinning of the freshwater lens and an increase in chloride concentrations of pumped water from production wells. These trends, combined with projected increa
Kolja Rotzoll, Delwyn S. Oki, Adam G. Johnson, William R. Souza

Water-budget accounting for tropical regions model (WATRMod) documentation

Regional groundwater recharge commonly is estimated using a threshold-type water-budget approach in which groundwater recharge is assumed to occur when water in the plant-root zone exceeds the soil’s moisture storage capacity. A water budget of the plant-soil system accounts for water inputs (rainfall, fog interception, irrigation, septic-system leachate, and other inputs), water outputs (runoff,
Delwyn S. Oki