Simulation of saltwater intrusion in the Northern Guam Lens using a microcomputer

Contractor, D. N.; Srivastava, Rajesh

doi:10.1016/0022-1694(90)90252-s

Cited by 13 publications

(7 citation statements)

References 6 publications

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“…Within the plateau, the Barrigada Limestone, of Late Miocene to Pliocene age, forms the bulk of the aquifer, although it is exposed on only 18 percent of the surface. It consists of fine-grained, pure foraminiferal-detrital limestone, which grades upward and outward into the overlying Mariana Limestone (Ward and others, 1965;Contractor and Srivastava 1990;Jocson and others, 2002). With a thickness of greater than 540 ft (Camp, Dresser & McKee Inc., 1982;Tracey and others, 1964), the permeable and productive Barrigada Limestone supplies water to most of the wells in northern Guam.…”

Section: Geologymentioning

confidence: 99%

“…, Darcy's law generally is assumed applicable to regional groundwater flow analyses in Guam (Contractor, 1983;Contractor and Srivastava, 1990;Jocson and others, 1999;Contractor and Jenson, 2000).…”

Section: Hydraulic Conductivitymentioning

confidence: 99%

“…Faults transecting the plateau complicate the structure and regional hydraulic conductivity of the aquifer rock units (Mylroie and others, 2001;Jenson and others, 2006). In previous modeling studies, the regional horizontal hydraulic conductivity of the main limestone aquifer generally is estimated to be thousands to tens of thousands of feet per day (Contractor and Srivastava, 1990;Jocson and others, 1999;Contractor and Jenson, 2000). Ayers and Clayshulte (1984) made regional hydraulicconductivity estimates ranging from 3,300-19,700 feet per day (ft/d) from analyses of tidal-induced fluctuations in five wells of varying distances inland on the central west coast of northern Guam, and they noted "shoreline rocks may be lower in hydraulic conductivity," acting "as a dam to the inland propagating tidal signal."…”

Section: Hydraulic Conductivitymentioning

confidence: 99%

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The effects of withdrawals and drought on groundwater availability in the Northern Guam Lens Aquifer, Guam

Gingerich¹

2013

Scientific Investigations Report

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For more information on the USGS-the Federal source for science about the Earth, its natural and living resources, natural hazards, and the environment, visit http://www.usgs.gov or call 1-888-ASK-USGS.For an overview of USGS information products, including maps, imagery, and publications, visit http://www.usgs.gov/pubprodTo order this and other USGS information products, visit http://store.usgs.gov Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.Although this information product, for the most part, is in the public domain, it also may contain copyrighted materials as noted in the text. Permission to reproduce copyrighted items must be secured from the copyright owner.Suggested citation: Gingerich, S.B., 2013, The effects of withdrawals and drought on groundwater availability in the Northern Guam Lens Aquifer, Guam: U.S. Geological Survey Scientific Investigations Report 2013-5216, 76 p., http://dx.doi.org/10.3133/ sir20135216. ISSN 2328-0328 (online) iii Executive SummaryMost of the public water supply on Guam is pumped from a freshwater lens in the Northern Guam Lens Aquifer, a limestone aquifer. Because of population growth and a potential military realignment involving the U.S. Marine Corps (USMC), groundwater withdrawals from wells are expected to increase. Currently (2013), the salinity of water pumped from some wells in the area is higher than acceptable for drinking water. The expected increase in demand for water has led to concern over the long-term sustainability of withdrawals from existing and proposed wells. In 2010, to aid in management of groundwater resources and to plan for sustainable growth on the island, the United States Marine Corps, Headquarters entered into a cooperative agreement with the U.S. Geological Survey (USGS) to study groundwater availability in northern Guam. The objective of this 3.5-year study was to estimate the effects of several hypothetical withdrawal scenarios on water levels, the transition zone between freshwater and saltwater, and salinity of pumped wells.On Guam, freshwater-lens systems are found in limestone and volcanic rocks, but the most important groundwater sources are from the freshwater parts of these systems in the high-hydraulic-conductivity limestone rocks of northern Guam. The most intensely developed groundwater system in this area comprises a lens-shaped freshwater body, an intermediate brackish-water transition zone, and underlying saltwater. For management purposes, the Guam Environmental Protection Agency (GEPA) delineated the Northern Guam Lens Aquifer (NGLA) into six hydrologically connected aquifer basins: Agafo Gumas, Andersen, Finegayan, Hagåtña, Mangilao, and Yigo-Tumon. Hydrologic DataKnowledge of the NGLA hydrology comes from compilation and analysis of data on water levels, salinity profiles in deep monitoring wells, production well pumping rates and salinities, and geologic information gleaned from decades of well drilling and hydrologic monitoring. The NGLA...

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Section: Geologymentioning

confidence: 99%

Section: Hydraulic Conductivitymentioning

confidence: 99%

Section: Hydraulic Conductivitymentioning

confidence: 99%

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The effects of withdrawals and drought on groundwater availability in the Northern Guam Lens Aquifer, Guam

Gingerich¹

2013

Scientific Investigations Report

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“…This formation consists of fine-to course-grained foraminiferal limestone, has high permeability, and supplies water to most of the wells in northern Guam (Tracey and others, 1964;Ward and others, 1965;Contractor and Srivastava, 1990;Jocson and others, 2002). The Mariana Limestone covers most of northern Guam, Orote Peninsula, and the plateau fringing the east coast of southern Guam.…”

Section: Hydrogeologymentioning

confidence: 99%

“…Near the volcanic uplands, the Mariana Limestone is clay-rich (Hagåtña Argillaceous Member), and has moderate to high permeability. The permeability of the non-argillaceous limestone is considered very high owing to the presence of many solution fissures and channels (Ward and others, 1965;Contractor and Srivastava, 1990;Jocson and others, 2002). Unconsolidated alluvial deposits underlie valley floors and coastal lowlands.…”

Section: Hydrogeologymentioning

confidence: 99%

A water-budget model and estimates of groundwater recharge for Guam

Johnson¹

2012

Scientific Investigations Report

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COVER: Map of Guam showing the relative distribution of estimated annual recharge for baseline conditions. Estimated recharge is shown using a special color scale with red representing very low recharge and dark blue representing very high recharge. For an overview of USGS information products, including maps, imagery, and publications, visit http: //www.usgs.gov/pubprod To order this and other USGS information products, visit http://store.usgs.gov Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the U.S. Government.Although this report is in the public domain, permission must be secured from the individual copyright owners to reproduce any copyrighted material contained within this report. AbstractOn Guam, demand for groundwater tripled from the early 1970s to 2010. The demand for groundwater is anticipated to further increase in the near future because of population growth and a proposed military relocation to Guam. Uncertainty regarding the availability of groundwater resources to support the increased demand has prompted an investigation of groundwater recharge on Guam using the most current data and accepted methods. For this investigation, a daily water-budget model was developed and used to estimate mean recharge for various land-cover and rainfall conditions. Recharge was also estimated for part of the island using the chloride mass-balance method.Using the daily water-budget model, estimated mean annual recharge on Guam is 394

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Estimating hydraulic properties from tidal attenuation in the Northern Guam Lens Aquifer, territory of Guam, USA

et al. 2013

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Simulation of saltwater intrusion in the Northern Guam Lens using a microcomputer

Cited by 13 publications

References 6 publications

The effects of withdrawals and drought on groundwater availability in the Northern Guam Lens Aquifer, Guam

The effects of withdrawals and drought on groundwater availability in the Northern Guam Lens Aquifer, Guam

A water-budget model and estimates of groundwater recharge for Guam

Estimating hydraulic properties from tidal attenuation in the Northern Guam Lens Aquifer, territory of Guam, USA

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