U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2005-5253

Prepared in cooperation with the Honolulu Board of Water Supply

Numerical Simulation of the Effects of Low-Permeability 

Valley-Fill Barriers and the Redistribution of Ground-Water 

Withdrawals in the Pearl Harbor Area, Oahu, Hawaii

1880

1975
About the cover: The simulated distribution of salinity in the western part of the 

Pearl Harbor area is shown for predevelopment conditions (1880) and for the 

peak development period (1975), when the brackish-water transition zone rose 

in response to withdrawals.
Numerical Simulation of the Effects of 

Low-Permeability Valley-Fill Barriers 

and the Redistribution of Ground-Water 

Withdrawals in the Pearl Harbor Area, 

Oahu, Hawaii 

By Delwyn S. Oki

Prepared in cooperation with the Honolulu Board of Water Supply

Scientific Investigations Report 2005-5253

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

Gale A. Norton, Secretary

U.S. Geological Survey

P. Patrick Leahy, Acting Director

U.S. Geological Survey, Reston, Virginia: 2005

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Suggested citation:

Oki, D.S., 2005, Numerical Simulation of the Effects of Low-Permeability Valley-Fill Barriers and the Redistribution of 

Ground-Water Withdrawals in the Pearl Harbor Area, Oahu, Hawaii: U.S. Geological Survey Scientific Investigations 

Report 2005-5253, 111 p.
iii

Contents

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................2

Setting .............................................................................................................................................................2

Land Use.................................................................................................................................................5

Sugarcane Cultivation.................................................................................................................5

Pineapple Cultivation ..................................................................................................................5

Climate....................................................................................................................................................9

Rainfall...........................................................................................................................................9

Pan Evaporation...........................................................................................................................9

Geology...................................................................................................................................................9

Waianae Volcano.......................................................................................................................12

Koolau Volcano ..........................................................................................................................12

Volcanic-Rock Types.................................................................................................................12

Geologic Modification Processes...........................................................................................12

Hydraulic Properties of the Rocks ...................................................................................................13

Hydraulic Conductivity..............................................................................................................13

Storage ........................................................................................................................................14

Dispersion Characteristics.......................................................................................................15

Valley-Fill Barriers .......................................................................................................................................15

Effects of Valley-Fill Barriers on Water Levels ..............................................................................17

Ground-Water Flow System.......................................................................................................................21

Freshwater Lens..................................................................................................................................21

Recharge..............................................................................................................................................21

Discharge.............................................................................................................................................26

Withdrawals from Wells ...........................................................................................................26

Pearl Harbor Springs.................................................................................................................26

Water Levels........................................................................................................................................31

Salinity ..................................................................................................................................................33

Temperature.........................................................................................................................................33

Simulation of Ground-Water Flow.............................................................................................................36

Construction of the Model.................................................................................................................36

Model Mesh................................................................................................................................36

Boundary Conditions.................................................................................................................36

Initial Conditions ........................................................................................................................39

Representation of Hydrogeologic Features ..........................................................................39

Recharge.....................................................................................................................................39

Withdrawal..................................................................................................................................42

Water Properties........................................................................................................................42

Aquifer Properties .....................................................................................................................42

Evaluation of Simulated Transient Conditions 1880-2000 .............................................................47

Simulation of the Effects of Valley-Fill Barriers on Water Levels and Salinity..................................47

Simulation of Redistributed Withdrawals 2001-2025 .............................................................................53
iv

Contents—Continued

Scenario 1 ............................................................................................................................................65

Scenario 2 ............................................................................................................................................67

Scenario 3 ............................................................................................................................................67

Scenario 4 ............................................................................................................................................67

Scenario 5 ............................................................................................................................................67

Scenario 6 ............................................................................................................................................75

Scenario 7 ............................................................................................................................................75

Summary of Effects of Redistributing Withdrawals......................................................................75

Model Limitations.........................................................................................................................................80

Summary........................................................................................................................................................80

References Cited..........................................................................................................................................82

Appendix A. Monthly withdrawals from wells in the Pearl Harbor area............................................87

Appendix B. Properties of pumped wells in the Pearl Harbor area ..................................................103

Figures

Figure 1. State of Hawaii aquifer-management systems (Ewa-Kunia, Waipahu-Waiawa, and

Waimalu) in the Pearl Harbor area and other geographic features, Oahu, Hawaii .......3

Figure 2. Mean annual rainfall, Oahu, Hawaii, and mean monthly rainfall at selected rain

gages............................................................................................................................................4

Figure 3. Areas of sugarcane and pineapple cultivation during selected periods from 1900 to

2000 in the Pearl Harbor area, Oahu, Hawaii ........................................................................6

Figure 4. Mean annual pan evaporation, Oahu, Hawaii, and mean monthly pan evaporation

at selected stations .................................................................................................................10

Figure 5. Generalized surficial geology, Oahu, Hawaii.......................................................................11

Figure 6. Structural contours of the top of the volcanic-rock aquifer in the Honolulu area,

Oahu, Hawaii.............................................................................................................................16

Figure 7. Selected wells with water-level, salinity, or geologic information used in this study,

and structural contours of the top of the volcanic-rock aquifer in the Pearl Harbor

area, Oahu, Hawaii ..................................................................................................................18

Figure 8. Cross section of Waiawa Stream valley, Oahu, Hawaii ....................................................19

Figure 9. Measured water levels in wells near the Waiawa Shaft (2558-10), which was shut

off during February 23-25, 2005, Pearl Harbor area, Oahu, Hawaii..................................20

Figure 10. Measured and simulated barometric-pressure response in Waimano observation

well 2557-04, Oahu, Hawaii, during February 15, 2005 through February 25, 2005 ........22

Figure 11. Ground-water areas and generalized directions of ground-water movement, Oahu,

Hawaii ........................................................................................................................................23

Figure 12. Generalized cross section of ground-water flow in the Pearl Harbor area, Oahu,

Hawaii ........................................................................................................................................24

Figure 13. Distribution of ground-water recharge for predevelopment land use, Oahu, 

Hawaii ........................................................................................................................................25

Figure 14. Ratios of mean annual rainfall during selected periods to long-term (1916-83) mean

annual rainfall (Giambelluca and others, 1986), Oahu, Hawaii.........................................27

Figure 15. Ground-water withdrawals from the Pearl Harbor and Moanalua areas, Oahu,

Hawaii ........................................................................................................................................30
Figures—Continued

Figure 16. Water-level surveys of October 31, 2002 and May 15, 2003, Pearl Harbor area,

Oahu, Hawaii.............................................................................................................................32

Figure 17. Measured water levels in selected wells in the Pearl Harbor area, 

Oahu, Hawaii.............................................................................................................................34

Figure 18. Measured salinity profiles in selected wells in the Pearl Harbor area, 

Oahu, Hawaii.............................................................................................................................35

Figure 19. Model boundary conditions and other features for the vertically aligned mesh,

Pearl Harbor area, Oahu, Hawaii ..........................................................................................37

Figure 20. Vertical cross section (western edge) of model mesh for the Pearl Harbor area,

viewed from west to east .......................................................................................................38

Figure 21. Profile of Waiawa Stream channel and estimated bottom of valley-fill barrier, Pearl

Harbor area, Oahu, Hawaii.....................................................................................................40

Figure 22. Profile of Waimalu Stream channel and estimated bottom of valley-fill barrier, Pearl

Harbor area, Oahu, Hawaii.....................................................................................................41

Figure 23. Selected withdrawal wells used in construction of the numerical model of the

Pearl Harbor area and the Moanalua ground-water area, Oahu, Hawaii......................45

Figure 24. Measured and simulated (using base-case valley-fill barriers) water levels in

selected wells in the Pearl Harbor area, Oahu, Hawaii ....................................................48

Figure 25. Difference between measured and simulated (using base-case valley-fill barriers) 

1950s water levels at selected wells, Pearl Harbor area, Oahu, Hawaii........................50

Figure 26. Measured and simulated (using base-case valley-fill barriers) discharge from the 

Pearl Harbor springs, Oahu, Hawaii. ....................................................................................51

Figure 27. Measured and simulated (using base-case valley-fill barriers) salinity profiles in 

selected wells in the Pearl Harbor area, Oahu, Hawaii ....................................................52

Figure 28. Valley-fill barrier depths and configurations used in sensitivity tests of the

numerical ground-water model, Pearl Harbor area, Oahu, Hawaii.................................54

Figure 29. Measured and simulated (with no valley-fill barriers) water levels in selected wells

in the Pearl Harbor area, Oahu, Hawaii ...............................................................................55

Figure 30. Measured and simulated (with base-case valley-fill barriers deepened by 200 ft)

water levels in selected wells in the Pearl Harbor area, Oahu, Hawaii .........................57

Figure 31. Measured and simulated (with Waiawa valley-fill barrier deepened to 660 ft below

mean sea level) water levels in selected wells in the Pearl Harbor area, Oahu,

Hawaii ........................................................................................................................................59

Figure 32. Measured and simulated (with Waimalu valley-fill barrier deepened to 660 ft below

mean sea level) water levels in selected wells in the Pearl Harbor area, Oahu,

Hawaii ........................................................................................................................................61

Figure 33. Measured and simulated (with Waiawa valley-fill barrier deepened to 660 feet

below mean sea level) salinity profiles in selected wells in the Pearl Harbor area,

Oahu, Hawaii.............................................................................................................................63

Figure 34. Simulated change in 2-percent salinity depth caused by reducing withdrawal from

the Halawa Shaft (2354-01) by 5.66 million gallons per day and increasing

withdrawal from Pearl City III (2557-03) by the same amount relative to the 2003

permitted rates .........................................................................................................................66

Figure 35. Simulated (with no valley-fill barriers) change in 2-percent salinity depth caused by

reducing withdrawal from the Halawa Shaft (2354-01) by 5.66 million gallons per

day and increasing withdrawal from Pearl City III (2557-03) by the same amount 

relative to the 2003 permitted rates ......................................................................................68
vi

Figures—Continued

Figure 36. Simulated (with Waiawa valley-fill barrier deepened to 660 feet below mean sea

level) change in 2-percent salinity depth caused by reducing withdrawal from the

Halawa Shaft (2354-01) by 5.66 million gallons per day and increasing withdrawal

from Pearl City III (2557-03) by the same amount relative to the 2003 permitted 

rates ..........................................................................................................................................69

Figure 37. Simulated change in 2-percent salinity depth caused by reducing withdrawal from

the Halawa Shaft (2354-01) by 2.83 million gallons per day and increasing

withdrawal from Pearl City III (2557-03) by the same amount relative to the 2003

permitted rates .........................................................................................................................70

Figure 38. Simulated change in 2-percent salinity depth caused by reducing withdrawal from

the Halawa Shaft (2354-01) by 5.66 million gallons per day and increasing

withdrawal from Kunia III (2401-04) by the same amount relative to the 2003

permitted rates .........................................................................................................................71

Figure 39. Simulated change in 50-percent salinity depth caused by reducing withdrawal from

the Halawa Shaft (2354-01) by 5.66 million gallons per day and increasing

withdrawal from Kunia III (2401-04) by the same amount relative to the 2003

permitted rates .........................................................................................................................72

Figure 40. Simulated change in 2-percent salinity depth caused by reducing withdrawal from

the Kalauao Wells (2355-09 to -14) by 5.88 million gallons per day and increasing

withdrawal from Pearl City III (2557-03) by the same amount relative to the 2003 

permitted rates .........................................................................................................................73

Figure 41. Simulated change in 2-percent salinity depth caused by reducing withdrawal from

the Kalauao Wells (2355-09 to -14) by 2.94 million gallons per day and increasing

withdrawal from Pearl City III (2557-03) by the same amount relative to the 2003 

permitted rates .........................................................................................................................74

Figure 42. Simulated change in 2-percent salinity depth caused by reducing withdrawal from

the Kalauao Wells (2355-09 to -14) by 5.88 million gallons per day and increasing

withdrawal from Kunia III (2401-04) by the same amount relative to the 2003 permitted 

rates ..........................................................................................................................................76

Figure 43. Simulated change in 50-percent salinity depth caused by reducing withdrawal from

the Kalauao Wells (2355-09 to -14) by 5.88 million gallons per day and increasing

withdrawal from Kunia III (2401-04) by the same amount relative to the 2003 permitted 

rates ..........................................................................................................................................77

Figure 44. Simulated change in 2-percent salinity depth caused by reducing withdrawals from

the Halawa Shaft (2354-01) by 2.83 million gallons per day and the Kalauao Wells

(2355-09 to -14) by 2.94 million gallons per day and increasing withdrawal from Kunia 

III (2401-04) by 5.77 million galons per day relative to the 2003 permitted rates ...........78

Figure 45. Simulated change in 50-percent salinity depth caused by reducing withdrawals

from the Halawa Shaft (2354-01) by 2.83 million gallons per day and the Kalauao

Wells (2355-09 to -14) by 2.94 million gallons per day and increasing withdrawal

from Kunia III (2401-04) by 5.77 million galons per day relative to the 2003 permitted 

rates ..........................................................................................................................................79

Figure A1. Monthly ground-water withdrawals during 1890 to 2000 from wells in the Pearl 

Harbor and Moanalua areas, Oahu, Hawaii........................................................................88
vii

Tables

Table 1. Relations between annual rainfall and annual recharge for different land uses,

Pearl Harbor area, Oahu, Hawaii ..........................................................................................24

Table 2. Relations between discharge at the Pearl Harbor springs and water level

measured at well 2256-10, Oahu, Hawaii .............................................................................31

Table 3. Estimated ground-water recharge used in construction of the numerical model of

the Pearl Harbor area, Oahu, Hawaii during selected periods ........................................43

Table 4. Estimated areas and irrigation rates for furrow-irrigated sugarcane fields in the Pearl

Harbor area, Oahu, Hawaii during selected time periods.................................................44

Table 5. Aquifer-property values used in the construction of the numerical ground-water

model of the Pearl Harbor area, Oahu, Hawaii ...................................................................46

Table 6. 2003 permitted withdrawal rates from the Pearl Harbor and Moanalua areas, Oahu, 

Hawaii ........................................................................................................................................64

Table 7. Summary of simulated withdrawals for redistributed withdrawal scenarios in the

Pearl Harbor area, Oahu, Hawaii ..........................................................................................65

Table B1. Properties of pumped wells in the Pearl Harbor area, Oahu, Hawaii ...........................104
viii

Conversion Factors and Datums

Multiply By To obtain

Length

inch (in.) 25.4 millimeter (mm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

acre 4,047 square meter (m2)

square foot (ft2) 0.09290 square meter (m2)

square mile (mi2) 2.590 square kilometer (km2) 

Volume

million gallons (Mgal) 3,785 cubic meter (m3)

cubic foot (ft3) 0.02832 cubic meter (m3) 

Flow rate

foot per day (ft/d) 0.3048 meter per day (m/d)

foot per year (ft/yr) 0.3048 meter per year (m/yr)

cubic foot per second (ft3/s) 0.02832 cubic meter per second (m3/s)

million gallons per day (Mgal/d) 0.04381 cubic meter per second (m3/s)

inch per hour (in/h) 25.4 millimiter per hour (m/h)

inch per week (in/week) 25.4 millimeter per week (mm/week)

inch per year (in/yr) 25.4 millimeter per year (mm/yr)

Mass

pound, avoirdupois (lb) 0.4536 kilogram (kg) 

Pressure

atmosphere, standard (atm) 101.3 kilopascal (kPa)

bar 100 kilopascal (kPa) 

pound per square foot (lb/ft2) 0.04788 kilopascal (kPa) 

pound per square inch (lb/in2) 6.895 kilopascal (kPa)

Density

pound per cubic foot (lb/ft3) 16.02 kilogram per cubic meter (kg/m3)

Hydraulic conductivity

foot per day (ft/d) 0.3048 meter per day (m/d)

Hydraulic gradient

foot per mile (ft/mi) 0.1894 meter per kilometer (m/km)

Leakance

foot per day per foot [(ft/d)/ft] 1 meter per day per meter

Dynamic viscosity

slug per foot per second (slug/ft/s) 47.88 pascal-sec (Pa-s)

Temperature in degrees Celsius (°C) may be converted to degrees Fahrenheit (°F) as follows:

°F=(1.8×°C)+32

Temperature in degrees Fahrenheit (°F) may be converted to degrees Celsius (°C) as follows:

°C=(°F–32)/1.8

Vertical coordinate information is referenced to mean sea level.

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83).

Altitude, as used in this report, refers to distance above the vertical datum.

Specific conductance is given in microsiemens per centimeter at 25 degrees Celsius (μS/cm at 

25°C).
Abstract

The aquifer in the Pearl Harbor area of southern Oahu is 

the most heavily used aquifer in the State of Hawaii, producing more than 200 million gallons per day during the 1970s 

when sugarcane was actively cultivated, and more recently, 

about 100 million gallons per day during 2000. The aquifer 

has been divided by the State into three hydrologically connected management systems: the Ewa-Kunia system in the 

west, the Waipahu-Waiawa system in the middle, and the 

Waimalu system in the east. During some periods, reported 

withdrawals from the Waimalu management system have 

exceeded the State’s sustainable-yield estimate for this system 

of 45 million gallons per day. This has led to concern regarding potential saltwater-intrusion effects associated with longterm withdrawals from the Waimalu management system. 

In the Waimalu management system, water levels and 

salinity may be influenced by valley-fill barriers associated 

with existing stream valleys. Valley-fill barriers are formed by 

low-permeability valley-fill deposits and weathered volcanic rocks beneath the valley-fill deposits, and impede lateral 

ground-water movement. The State’s sustainable-yield estimates for the Pearl Harbor area do not account for the hydrologic effects of these barriers.

The objectives of this study are to (1) obtain a better 

understanding of the hydrologic effects of valley-fill barriers 

in the Pearl Harbor area, Oahu, Hawaii, (2) determine the possible effects of valley-fill barriers on water levels and salinity 

in the Pearl Harbor area using a three-dimensional, densitydependent ground-water flow model, and (3) estimate the 

effects of redistributing existing withdrawals on the freshwater 

resource.

A numerical finite-element ground-water model capable 

of simulating variable-density flow was developed to meet the 

study objectives. The model mainly used published estimates 

for the permeability, storage, and dispersivity values, and 

simulated water levels and salinity profiles that generally were 

in agreement with measured water levels and salinity profiles 

from representative wells in the modeled area. Model sensitivity analyses of valley-fill-barriers indicated that simulated 

water levels and salinity can be affected by the depth and 

length of the hypothesized valley-fill barriers.

The model constructed for this study was used to simulate the hydrologic effects of redistributing withdrawals in the 

Pearl Harbor area by reducing withdrawals in the eastern part 

of the Waimalu area and increasing withdrawals farther to the 

west by an equal amount. Simulation results from selected scenarios of redistributed withdrawal indicate that: (1) redistributing withdrawal from Halawa Shaft (2354-01) or the Kalauao 

Wells (2355-09 to -14), near the eastern part of the Waimalu 

management system, to Pearl City III (2557-03), near the 

western part of the Waimalu management system, results in a 

thickening of the freshwater zone east of Waimalu Stream and 

a thinning of the freshwater zone west of Waimalu Stream; (2) 

redistributing withdrawal from Halawa Shaft to Pearl City III 

results in greater thickening of the freshwater in the eastern 

part of the Waimalu management system relative to redistributing an equal amount of withdrawal from the Kalauao Wells 

to Pearl City III; (3) the extent of freshwater thickening in the 

eastern part of the Waimalu management system caused by 

reducing withdrawal from the area is directly related to the 

amount of the reduction; (4) the zone where freshwater thickens in response to reducing withdrawal from a well is greatest 

downgradient from the well, between the well and the shore; 

and (5) valley-fill barriers can potentially reduce the zone 

where freshwater thickness increases in response to reduced 

withdrawals. 

The numerical model developed for this study simulates 

regional water levels and salinity and may not accurately 

simulate salinity of water pumped from individual wells. 

Salinity of water pumped by a well may be controlled by local 

heterogeneities in the aquifer that are not represented in the 

model. The model has several other limitations for predictive 

purposes because of the various assumptions used and possible 

uncertainties in input data (for example, recharge, withdrawals, boundary conditions, and parameter values). Model reliability can be enhanced as our understanding of ground-water 

recharge, the distribution of model parameter values, and the 

geometry of the valley-fill barriers improves, and as numerical 

modeling technology improves. 

Numerical Simulation of the Effects of Low-Permeability 

Valley-Fill Barriers and the Redistribution of 

Ground-Water Withdrawals in the 

Pearl Harbor Area, Oahu, Hawaii 

By Delwyn S. Oki
Introduction

The aquifer in the Pearl Harbor area (fig. 1) of southern 

Oahu is the most heavily used aquifer in the State of Hawaii. 

In 1979, the Hawaii Board of Land and Natural Resources 

designated the Pearl Harbor area as a Ground-Water Management Area. With this designation, the State was authorized to 

protect the ground-water resource by managing ground-water 

withdrawals from the aquifer through a permitting process. 

For management purposes, the Hawaii Commission on Water 

Resource Management (CWRM) has divided the Pearl Harbor 

area into three hydrologically connected systems. From west 

to east, these management systems are the Ewa-Kunia system, 

the Waipahu-Waiawa system, and the Waimalu system (fig. 1).

During 2001, reported withdrawals from the Waimalu 

management system averaged 46.5 million gallons per 

day (Mgal/d) (unpub. data, Hawaii Commission on Water 

Resource Management). Ground-water withdrawal from 

the Waimalu management system was slightly higher than 

the CWRM sustainable-yield estimate of 45 Mgal/d for the 

area. This led to concern regarding potential saltwater-intrusion effects associated with long-term withdrawals from the 

Waimalu management system. 

The aquifer in the Pearl Harbor area is formed mainly 

by gently dipping lava flows extending from land surface to 

thousands of feet below sea level, with a number of geologic 

barriers controlling regional ground-water flow. Volcanic 

rift zones contain thousands of nearly vertical, low-permeability dikes that cut across existing lava flows and impound 

water in numerous compartments (Takasaki and Mink, 1985). 

Low-permeability valley-fill deposits and weathered volcanic 

rocks beneath the valley-fill deposits impede ground-water 

movement and can create differences in ground-water levels 

on opposite sides of the valley. In the Waimalu management 

system, ground-water flow may be influenced by valley-fill 

barriers associated with existing stream valleys. The CWRM 

sustainable-yield estimate for this area does not account for 

the hydrologic effects of these barriers.

In cooperation with the City and County of Honolulu 

Board of Water Supply (BWS), the U.S. Geological Survey 

(USGS) undertook an investigation to evaluate the possible 

hydrologic effects of valley-fill barriers in the Pearl Harbor 

area. The objectives of this study are to (1) develop a better 

understanding of the hydrologic effects of valley-fill barriers 

in the Pearl Harbor area, (2) determine the possible effects of 

valley-fill barriers on water levels and salinity in the Pearl Harbor area, and (3) estimate the effects of redistributing existing 

withdrawals on the freshwater resource.

This report describes (1) information related to valley-fill 

barriers in the Pearl Harbor area, including water-level data 

collected as part of this study, (2) development of a numerical ground-water flow and transport model, and (3) results of 

model simulations to assess the hydrologic effects of lowpermeability valley-fill barriers and the effects of redistributing withdrawals on water levels and salinity in the Waimalu 

management system of the Pearl Harbor area. 

Acknowledgments.—The author is grateful to the Honolulu Board of Water Supply for providing invaluable data and 

access to monitor wells during the study. The cooperation of 

the Honolulu Board of Water Supply, Hawaii Commission on 

Water Resource Management, U.S. Navy Public Works Center, and U.S. Air Force (through their consultant URS Corp.) 

made it possible to conduct synoptic water-level surveys of the 

Pearl Harbor area in a timely manner. Paul R. Eyre of the U.S. 

Navy Public Works Center coordinated a shut down of the 

Waiawa Shaft to investigate water-level recovery on opposite 

sides of Waiawa Stream valley. Patrice Tottori Liu of Gentry 

Investment Properties facilitated access to a well on Gentry 

property for water-level-monitoring purposes, and Jeff A. Perreault (USGS) and Kenneth N. Natividad (USGS) helped in 

the collection of water-level data from selected wells. Finally, 

the author thanks Chien-Hwa (Max) Chen (USGS) for characterizing areas of pineapple and sugarcane cultivation for this 

study.

Setting

The island of Oahu (597 mi2) is the third largest island 

of the State of Hawaii (Juvik and Juvik, 1998) and is formed 

by the eroded remnants of the Waianae and Koolau shield 

volcanoes. The Waianae Range, which is the eroded remnant 

of the older Waianae Volcano, forms the western part of the 

island and has a peak altitude of 4,025 ft at Mount Kaala, the 

highest peak on Oahu. The younger Koolau Range forms the 

eastern part of Oahu and has a peak altitude of 3,105 ft at Puu 

Konahuanui (fig. 1). A gently sloping saddle, the Schofield 

Plateau, lies between the two mountain ranges.

The Pearl Harbor study area is in the southern part of 

Oahu’s central corridor between the Koolau and Waianae 

Ranges (fig. 1). The study area is bounded on the northeast by 

the crest of the Koolau Range, on the southeast by the ridge 

(and flatter area near the coast) between South Halawa and 

Moanalua Stream valleys, on the south by the coast, on the 

west by the crest of the Waianae Range, and on the north by 

the approximate southern boundary of the Schofield groundwater area. The Schofield ground-water area is north of the 

Pearl Harbor area and is separated from the Pearl Harbor area 

by the southern Schofield ground-water dam, which is a natural feature of unknown structural origin (see for example Oki, 

1998). The study area is formed by the Ewa-Kunia, WaipahuWaiawa, and Waimalu aquifer-management systems defined 

by the CRWM (fig. 1). The management areas defined by the 

CWRM do not necessarily coincide with aquifer boundaries 

(Hunt, 1996). Thus, the boundaries of the study area do not 

coincide with hydrogeologic boundaries used in the numerical 

ground-water model in this study. 

Topography within the Pearl Harbor study area ranges 

from a broad flat coastal plain to steep interior mountains. 

Topography of the island affects climate, which generally is 

characterized by mild temperatures, cool and persistent northeasterly trade winds, and large spatial variations in rainfall 

(fig. 2). 

 Numerical Simulation of the Effects of Valley-Fill Barriers in the Pearl Harbor Area, Oahu, Hawaii
158o10'

157o50'

157o40'

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21o30'

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HAWAII 

LOCATION MAP 

PACIFIC

OCEAN

EXPLANATION 

STATE OF HAWAII AQUIFER-  MANAGEMENT-SYSTEM  BOUNDARY TOPOGRAPHIC DIVIDE TOPOGRAPHIC PEAK CITY OR TOWN 

!

Manini Gl

Waimea Gl

Huliwai Gl

Honouliuli Gl

Kaunala Gl

Kamananui Str

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P nu uul a Str

aha K na S rt

M nua wa S ili rt Pa ol ol

S rt

Ka il hi Str

Moana ul a Str

N

Ha al wa Str Wa mi a ul Str

K pi apa Str Na an uk li Str

Mailiilii Str

Makua Str

Makaleha Str

Kaukonahua Str

Poamoho Str North Fork

Opaeula Str

Anahulu River

M ka ha a Str

Kaupu i n t S r

Waikele

Str

a W ai wa Str

rt S oi O

Helemano Str

Sou ht Fork

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Ha al wa Str

Wa hi ee Str

Nuuanu Str

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Kaneohe Str 

Kahaluu

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Wa mi ano Str

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HONOLULU

Waikiki 

Kailua

Kaneohe

Makaha

Waianae 

Maili

Nanakuli

Ewa Beach

Ewa 

Waialua 

Haleiwa 

Sunset

Beach Kahuku

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Kaaawa 

Waimanalo 

Hawaii Kai

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!

!

Waipio 

Mililani

Schofield 

Barracks Wahiawa 

Base modified from U.S. Geological Survey National Hydrography Dataset, Albers equal area projection,standard parallels 21o19'40" and 21o38'20", centralmeridian 157o58', datum NAD83. Relief from U.S.Geological Survey digital elevation models, 1:24,000 

Kahuku Point 

Makapuu

Point

Barbers

Point

Diamond

Head

Kaena

Point

Waimanalo 

Bay

KANEOHE

BAY 

Kahana

Bay

Pearl 

 Harbor 

MAMALA BAY 

Maunalua Bay 

W

A

I A

N A E

R A

N G E

K O O L A U

R A N G E

Puu Konahuanui 

(3,105 feet) 

Mt Kaala 

(4,025 feet) 

EWA-KUNIA 

WAIPAHU-WAIAWA 

WAIMALU 

Waikele Spr 

Waiawa Spr 

Waiau-Waimano 

Spr

Kalauao Spr

Figure 1. State of Hawaii aquifer-management systems (Ewa-Kunia, Waipahu-Waiawa, and Waimalu) in the Pearl Harbor area and other geographic features, Oahu, Hawaii. 

Setting 
EWA

DISTRICT

HONOLULU

DISTRICT

!

!

!

!

!

!

!

!

!

!

!

!

!

Kahuku Point

Makapuu

Point

Diamond Head

Barbers

Point

Kaena

Point

Makaha

Ewa

Waialua

Haleiwa

Laie

Waipahu

Pearl

City

Aiea

Kailua Kaneohe

Schofield

Barracks

Wahiawa

Waimanalo

Bay

KANEOHE

BAY

MAMALA BAY

EXPLANATION

LINE OF EQUAL MEAN ANNUAL RAINFALL-- Interval, in inches, is variable. Number in  parentheses is value in millimetersTOPOGRAPHIC DIVIDEJUDICIAL DISTRICT BOUNDARYRAINGAGECITY OR TOWN

Pearl 

 Harbor

00

4 MILES 2

2 4 KILOMETERS

Base modified from U.S. Geological Survey NationalHydrography Dataset, Albers equal area projection, standard parallels 21o19'40" and 21o38'20", central meridian 157o58', datum NAD83. Relief from U.S. Geological Survey digital elevation models, 1:24,000

!

Waipio

!

Mililani

1

158o10'

157o50'

157o40'

21o40'

21o30'

21o20'

158o

59.1 (1,500)

59.1

(1,500)

39.4

(1,000)

31.5

(800)

23.6

(600)

59.1

(1,500)

78.7

(2,000)

118.1

(3,000)

157.5

(4,000)

196.9

(5,000)

236.2 (6,000)

275.6

(7,000)

39.4

(1,000)

31.5

(800)

23.6

(600)

23.6

(600)

39.4

(1,000)

157.5

(4,000)

78.7

(2,000)

31.5

(800)

31.5

(800)

31.5

(800)

2

2

2

2

2

2

2

2

State key no. 908

1 2 3 4 8 10 5 7 11 12 9 6

50

10

MONTH

MEAN MONTHLY RAINFALL,

IN INCHES

State key no. 883.2

1 2 3 4 8 10 5 7 11 12 9 6

0

302010

MONTH

MEAN MONTHLY RAINFALL,

IN INCHES

State key no. 795.1

1 2 3 4 8 10 5 7 11 12 9 6

50

10

MEAN MONTHLY RAINFALL,

IN INCHES

MONTH

State key no. 741

State key 

no. 750

1 2 3 4 8 10 5 7 11 12 9 6

50

10

MEAN MONTHLY RAINFALL,

IN INCHES

MONTH

State key no. 798

1 2 3 4 8 10 5 7 11 12 9 6

50

10

MEAN MONTHLY RAINFALL,

IN INCHES

MONTH

State key no. 847

1 2 3 4 8 10 5 7 11 12 9 6

50

10

MEAN MONTHLY RAINFALL,

IN INCHES

MONTH

State key no. 782

1 2 3 4 8 10 5 7 11 12 9 6

50

201510

MONTH

MEAN MONTHLY RAINFALL,

IN INCHES

Figure 2. Mean annual rainfall, Oahu, Hawaii, and mean monthly rainfall at selected rain gages (modified from Giambelluca and others, 1986).

 Numerical Simulation of the Effects of Valley-Fill Barriers in the Pearl Harbor Area, Oahu, Hawaii
Land Use

Gently sloping areas in the central and southern parts 

of the Pearl Harbor area were used extensively for sugarcane 

cultivation that was made possible by the discovery of artesian 

ground water during 1879 beneath the dry, southwestern 

coastal plain. Following the 1995 closure of the last remaining sugarcane plantation in the Pearl Harbor area, much of the 

former sugarcane lands was urbanized or used for diversified 

agriculture.

During the 20th century, land-use patterns on Oahu 

reflected increases in population and decreases in large-scale 

agricultural operations over time. The resident population 

on Oahu increased from 58,504 in 1900, to 876,156 in 2000 

(State of Hawaii, 2000). In 2000, about 72 percent of the 

State’s population resided on Oahu, and more than 40 percent 

of the residents on Oahu were in the Honolulu District. In 

recent years, the population in the Ewa District (fig. 2) has 

increased significantly as large-scale agricultural operations in 

this area have been replaced by urban developments. Between 

1980 and 2000, the resident population in the Ewa District 

increased 43 percent, from 191,051 to 272,328. For comparison, between 1980 and 2000, the population in the Honolulu 

District increased only 2 percent, from 365,048 to 372,279 

(State of Hawaii, 2000).

Toward the latter part of the 20th century, the general 

trend of land use on Oahu shifted from large-scale plantation agriculture to urban land use and diversified agriculture. 

Although two large pineapple plantations continue to operate 

in central Oahu, some of the land previously used for pineapple cultivation in the Pearl Harbor area has been developed 

for urban uses. A description of land use on Oahu during 1998 

is provided by Klasner and Mikami (2003). 

Sugarcane Cultivation

Prior to 1879, lack of a reliable source of irrigation water 

precluded large-scale sugarcane cultivation in the Pearl Harbor 

area. The 1879 discovery of artesian ground water beneath 

the dry, southwestern coastal plain of Oahu made it possible 

for sugarcane cultivation to expand to the Pearl Harbor area. 

Areas of sugarcane cultivation varied over time (fig. 3) until 

1995, when Oahu Sugar Company ceased operations.

In the Pearl Harbor area, sugarcane generally was grown 

at altitudes of a few feet to about 700 ft. Sugarcane cultivation 

practices varied among the plantations and were dependent 

on the variety of sugarcane as well as local field conditions. 

Sugarcane was grown year-round, and generally was harvested 

on a 2-yr crop cycle. A crop was initiated with the planting of 

sugarcane seeding stalks. One or two ratoon crops generally 

followed the initial crop. Prior to the 1970s, the main method 

of irrigation on Oahu was the furrow method, in which water 

was delivered to the fields through a system of ditches and 

in-field furrows. Fields generally were irrigated with the furrow method between 20 and 40 times over the 2-yr crop cycle, 

with each application requiring from 4 to 10 in. of water over 

the field (Yim and Dugan, 1975). Dale (1967) estimated that 

an average of about 112 in/yr of irrigation water was applied 

with the furrow method in southern Oahu between 1931 and 

1965. Estimates of the irrigation efficiency (ratio of water volume used by the crop to water volume applied) for the furrow 

method range from about 0.3 to 0.7 (Dale, 1967; Fukunaga, 

1978; Giambelluca, 1983; Mink, 1980; Nichols and others, 1996). Giambelluca (1983) estimated that ground-water 

recharge from furrow-irrigated sugarcane in the Pearl Harbor 

area averaged 87.3 in/yr, although Nichols and others (1996) 

estimated a much lower rate.

Although overhead sprinkler systems were introduced on 

Oahu during the 1960s to improve irrigation efficiency (Hall, 

1965), the drip-irrigation method began replacing the furrow 

method during the 1970s (Gibson, 1979). Estimates of the 

irrigation efficiency with the drip method range from about 

0.80 to 0.95 (Fukunaga, 1978). The drip method uses lateral 

tubes with small emitters that are spaced to deliver water to 

the plants and maintain adequate soil moisture in the plant root 

zone. With the drip method, water was applied daily during 

peak-use periods at a rate of about 0.03 in/hr over a 12-hour 

period (Yamauchi and Bui, 1990). Irrigation generally was 

discontinued 2 to 3 months before harvest to enhance sugar 

storage in the plant (Yim and Dugan, 1975). Using recharge 

estimates from Giambelluca (1983), Shade and Nichols (1996) 

developed a relation between rainfall and recharge (both 

expressed in terms of in/yr) for drip-irrigated sugarcane in the 

Pearl Harbor area:

Recharge (sugarcane, drip) = 0.64 · Rainfall + 11.1 (1)

Pineapple Cultivation

During the 20th century, large-scale pineapple cultivation 

on the island mainly was in central Oahu on three plantations, 

although only two plantations remain as of 2005 (Dole Food 

Co., Inc. and Del Monte Corp.). Areas of pineapple cultivation in the Pearl Harbor area varied over time (fig. 3). Much of 

the land that previously was used for pineapple cultivation in 

the central part of the Pearl Harbor area now is used for other 

purposes, including urban developments. 

Pineapples are grown year-round on Oahu, and fields are 

replanted every three to five years. The initial crop, which is 

harvested about 18 months after planting, is followed by one 

or two ratoon crops before the land is prepared for the next 

planting. Pineapples require much less water than sugarcane, 

and can be grown in areas of low to moderate rainfall with 

limited or no irrigation. Irrigation is applied using overhead 

sprinklers during periods of low rainfall or through drip-irrigation lines at the rate of about 0.25 in. per week (State of 

Hawaii, 1983). Most pineapples on Oahu have been cultivated 

in central Oahu at higher altitudes than areas of sugarcane 

cultivation.

Pineapple plants suppress evapotranspiration and enhance 

recharge relative to non-xerophytic plants. Using recharge 

Setting 
1940-49 1930-39

1920-29 1900-10

EXPLANATION 

PineapplesFurrow-irrigated sugarcane 

AGRICULTURAL AREA SUBSURFACE BOUNDARY BETWEEN  WAIANAE VOLCANICS AND KOOLAU  BASALT 

Topographic

Divide

158o10' 158o00' 157o50'

21o30'21o20'

Topographic

Divide

158o10' 158o00' 157o50'

21o30'21o20'

Topographic

Divide

158o10' 158o00' 157o50'

21o30'21o20'

Topographic

Divide

158o10' 158o00' 157o50'

21o30'21o20'

00

4 MILES 2

2 4 KILOMETERS 

Pacific Ocean

Area of 

Map

Oahu

Boundary of Pearl Harbor area

Boundary of Pearl Harbor area

Boundary of Pearl Harbor area

Boundary of Pearl Harbor area

Figure 3. Areas of sugarcane and pineapple cultivation during selected periods from 1900 to 2000 in the Pearl Harbor area, Oahu, Hawaii.

 Numerical Simulation of the Effects of Valley-Fill Barriers in the Pearl Harbor Area, Oahu, Hawaii
1975-79 1970-74

1960-69 1950-59

EXPLANATION 

PineapplesFurrow-irrigated sugarcane Drip-irrigated sugarcane 

AGRICULTURAL AREA SUBSURFACE BOUNDARY BETWEEN  WAIANAE VOLCANICS AND KOOLAU  BASALT 

Topographic

Divide

158o10' 158o00' 157o50'

21o30'21o20'

Topographic

Divide

158o10' 158o00' 157o50'

21o30'21o20'

Topographic

Divide

158o10' 158o00' 157o50'

21o30'21o20'

Topographic

Divide

158o10' 158o00' 157o50'

21o30'21o20'

00

4 MILES 2

2 4 KILOMETERS 

Pacific Ocean

Area of 

Map

Oahu

Boundary of Pearl Harbor area Boundary of Pearl Harbor areaBoundary of Pearl Harbor area Boundary of Pearl Harbor area

Figure 3. Areas of sugarcane and pineapple cultivation during selected periods from 1900 to 2000 in the Pearl Harbor area, Oahu, Hawaii—Continued. Setting 


1995-2000 1990-94

1985-89 1980-84

EXPLANATION 

PineapplesFurrow-irrigated sugarcane Drip-irrigated sugarcane 

AGRICULTURAL AREA SUBSURFACE BOUNDARY BETWEEN  WAIANAE VOLCANICS AND KOOLAU  BASALT 

Topographic

Divide

158o10' 158o00' 157o50'

21o30'21o20'

Topographic

Divide

158o10' 158o00' 157o50'

21o30'21o20'

Topographic

Divide

158o10' 158o00' 157o50'

21o30'21o20'

Topographic

Divide

158o10' 158o00' 157o50'

21o30'21o20'

00

4 MILES 2

2 4 KILOMETERS 

Pacific Ocean

Area of 

Map

Oahu

Boundary of Pearl Harbor area

Boundary of Pearl Harbor area

Boundary of Pearl Harbor area

Boundary of Pearl Harbor area

Figure 3. Areas of sugarcane and pineapple cultivation during selected periods from 1900 to 2000 in the Pearl Harbor area, Oahu, Hawaii—Continued.

 Numerical Simulation of the Effects of Valley-Fill Barriers in the Pearl Harbor Area, Oahu, Hawaii
estimates from Giambelluca (1983), Shade and Nichols (1996) 

developed a relation between rainfall and recharge (both 

expressed in terms of in/yr) for areas of pineapple cultivation 

in the Pearl Harbor area:

 Recharge (pineapple) = 0.935 · Rainfall – 13.54 (2)

Climate

Mild temperatures, cool and persistent northeasterly 

winds, a rainy season from October through April, and a dry 

season from May through September characterize the climate 

of Oahu (Blumenstock and Price, 1967; Sanderson, 1993). 

Topography and the location of the north Pacific anticyclone 

relative to the island primarily control the climate of Oahu. 

During the dry season, the stability of the north Pacific anticyclone produces persistent northeasterly winds, known locally 

as trade winds, that blow 80 to 95 percent of the time. During 

the rainy season, migratory weather systems often move past 

the Hawaiian islands, resulting in less persistent trade winds 

that blow 50 to 80 percent of the time. Southerly winds associated with low-pressure systems can bring heavy rains to the 

island. The dry coastal areas can receive most of their rainfall 

from these low-pressure systems. During heavy storms, 24-

hour rainfall can exceed 10 in. over coastal areas and 20 in. 

over the mountainous interior of the Koolau Range (Giambelluca and others, 1984).

Rainfall

Rainfall on Oahu is characterized by maxima at high 

altitudes and steep spatial gradients (fig. 2). Maximum mean 

annual rainfall is near the topographic crest of the Koolau 

Range and exceeds 275 in. (Giambelluca and others, 1986). 

Over the Waianae Range, the maximum mean annual rainfall is about 80 in. near Mount Kaala. Over the southwestern 

coastal parts of the Pearl Harbor area, mean annual rainfall 

is less than 25 in. Mean annual rainfall changes significantly 

over short distances; on the Koolau Range, this change can be 

about 80 in. over a distance of one mile. 

The windward (northeastern) side of the island is wettest. 

This pattern is controlled by the orographic lifting of moistureladen northeasterly trade winds along the windward slope of 

the Koolau Range, which is oriented roughly perpendicular to 

the direction of the trade winds. The moisture-laden air mass 

cools as it ascends the slopes of the Koolau Range, resulting 

in condensation, cloud formation, and high rainfall near the 

crest of the Koolau Range. Following its descent along the 

leeward slopes of the Koolau Range, the partially desiccated 

air ascends the slopes of the Waianae Range, which results in 

a smaller rainfall maximum near Mount Kaala. Because the 

air loses moisture during its ascent over a mountain, the driest 

areas on Oahu are near the coast on the leeward (southwest) 

sides of the Koolau and Waianae Ranges. This is commonly 

known as the rain-shadow effect.

Pan Evaporation

Pan evaporation generally is the main measurement used 

in Hawaii to assess the amount of water loss by evapotranspiration, which is the loss of water to the atmosphere by the 

combination of transpiration of plants and direct evaporation 

from plant, land, and water surfaces. Evapotranspiration is a 

major component of the hydrologic budget on Oahu. In the 

Pearl Harbor area, for example, evapotranspiration was estimated to be greater than 50 percent of the total water (rainfall 

plus irrigation) falling on or applied to the ground surface during 1946-75 (Giambelluca, 1983).

Over Oahu, pan evaporation minima exist at the higher 

altitudes of the Koolau and Waianae Ranges (fig. 4). Near the 

crest of the Koolau Range, mean annual pan evaporation may 

be as low as 20 in. Pan evaporation rates are highest along 

the southern coast of the island, where they may exceed 90 

in/yr. For comparison, the computed evaporation rate over 

the open ocean is 65 in/yr (Seckel, 1962). As with rainfall, 

the spatial distribution of pan evaporation on Oahu is related 

to topography. At high altitudes (where sunlight intensity is 

reduced because of clouds, humidity is high, and temperatures 

are low), pan-evaporation rates are reduced to 30 percent of 

the open-ocean rate. Pan evaporation rates along the southern 

coast of Oahu exceed the open-ocean rate due to heat advection. Evaporation rates are highest during the drier summer 

months when maximum sunlight and trade-wind flow also are 

highest (Ekern and Chang, 1985).

Geology

The geology of Oahu has been described by numerous 

investigators (see for example Macdonald and others, 1983; 

Palmer, 1927; Palmer, 1946; Stearns, 1985; Stearns and Vaksvik, 1935; Wentworth, 1951; Wentworth and Winchell, 1947; 

Winchell, 1947). Stearns (1939) published a detailed geologic 

map of Oahu. Langenheim and Clague (1987) described the 

stratigraphic framework of volcanic rocks for the entire island 

of Oahu. Presley and others (1997) revised the stratigraphic 

nomenclature for Waianae Volcano. A brief description of the 

geologic setting of Oahu follows.

Oahu is formed primarily by the shield-stage lavas of the 

older Waianae Volcano to the west and the younger Koolau 

Volcano to the east, and secondarily by preshield-, postshield-, 

and rejuvenated-stage volcanism (Langenheim and Clague, 

1987). Each volcano has two primary rift zones and a third 

lesser rift zone, all emanating from a collapsed caldera (fig. 5). 

The primary rift zones of the Waianae Volcano trend roughly 

northwest and south, and the third, lesser rift zone trends 

northeast. The primary rift zones of the Koolau Volcano trend 

northwest and southeast, and the third, subordinate rift zone 

trends southwest. The rift zones are marked by numerous 

vertical to nearly vertical intrusive dikes (Takasaki and Mink, 

1985; Walker, 1987).

Setting 
158o10'

157o50'

157o40'

21o40'

21o30'

21o20'

158o

!

!

!

!

!

!

!

!

!

!

!

!

!

Kahuku Point 

Makapuu

Point

Diamond Head 

Barbers

Point

Kaena

Point

Makaha

Ewa 

Waialua 

Haleiwa 

Laie

HONOLULU

Waipahu 

Pearl

City

Aiea

Kailua Kaneohe

Schofield 

Barracks Wahiawa 

Waimanalo 

Bay

KANEOHE

BAY 

MAMALA BAY 

EXPLANATION 

LINE OF EQUAL MEAN ANNUAL PAN  EVAPORATION--Interval 10 inches TOPOGRAPHIC DIVIDE PAN-EVAPORATION STATION CITY OR TOWN 

Pearl 

 Harbor 

00

4 MILES 2

2 4 KILOMETERS 

Base modified from U.S. Geological Survey National Hydrography Dataset, Albers equal area projection,standard parallels 21o19'40" and 21o38'20", centralmeridian 157o58', datum NAD83. Relief from U.S.Geological Survey digital elevation models, 1:24,000 

Waikiki 

!

!

! Mililani

30

90

80

80

80

90

80

80

80

70

60

60

70

80

80

70

60

50

70

80

70

60

50

50

40

40

30

30

20

20

70

70

40

60

60

50

90

2

2

2

2

2

2

2

2

1 2 3 4 8 10 5 7 11 12 9 6

543210

MONTH

MEAN MONTHLY PAN 

EVAPORATION, IN INCHES 

State key no. 782 

1 2 3 4 8 10 5 7 11 12 9 6

50

10

MONTH

MEAN MONTHLY PAN 

EVAPORATION, IN INCHES 

State key no. 908 

1 2 3 4 8 10 5 7 11 12 9 6

MONTH

MEAN MONTHLY PAN 

EVAPORATION, IN INCHES 5

4321

0

State key no. 882.1 

1 2 3 4 8 10 5 7 11 12 9 6

50

10

MEAN MONTHLY PAN 

EVAPORATION, IN INCHES 

MONTH

State key no. 795.1 

1 2 3 4 8 10 5 7 11 12 9 6

50

10

MEAN MONTHLY PAN 

EVAPORATION, IN INCHES 

MONTH

State key no. 741 

1 2 3 4 8 10 5 7 11 12 9 6

50

10

MEAN MONTHLY PAN 

EVAPORATION, IN INCHES 

MONTH

State key no. 798 

1 2 3 4 8 10 5 7 11 12 9 6

50

10

MEAN MONTHLY PAN 

EVAPORATION, IN INCHES 

MONTH

State key no. 847 

Figure 4. Mean annual pan evaporation, Oahu, Hawaii, and mean monthly pan evaporation at selected stations (modified from Ekern and Chang, 1985).

10 Numerical Simulation of the Effects of Valley-Fill Barriers in the Pearl Harbor Area, Oahu, Hawaii
Primary

Rift

Zone

Prim

a

ry

Rift

Zo

n

e

Primary

Rift

Zone

Primary Rift

Zone

i R tf

oZ

en

i R tf

oZ

en

!

!

!

!

!

!

!

!

! !

!

!

!

! !

! !

!

!

!

!

!

HONOLULU

Kailua

Kaneohe

Makaha

Waianae

Maili

Nanakuli

EwaBeach

Ewa

Waialua

Haleiwa

Sunset

Beach Kahuku

Laie

Kaaawa

Waimanalo

HawaiiKai

AinaHaina

Aiea

Waipahu

Schofield

Barracks

Wahiawa

!

!

Waipio

Mililani

158o10'

157o50'

157o40'

21o40'

21o30'

21o20'

158o

00

4 MILES 2

2 4 KILOMETERS

Kahuku Point

Makapuu

Point

Barbers

Point

Diamond

Head

Kaena

Point

Waimanalo

Bay

KANEOHE

BAY

Kahana

Bay

Pearl 

 Harbor

MAMALA BAY

Maunalua Bay

Base modified from U.S. Geological Survey NationalHydrography Dataset, Albers equal area projection, standard parallels 21o19'40" and 21o38'20", central meridian 157o58', datum NAD83. Relief from U.S. Geological Survey digital elevation models, 1:24,000

Waikiki

EXPLANATION

SEDIMENTARY DEPOSITS UNCONSOLIDATED CONSOLIDATEDKOOLAU VOLCANO REJUVENATED-STAGE VENT HONOLULU VOLCANICS KOOLAU BASALTWAIANAE VOLCANO (WAIANAE VOLCANICS) POSTSHIELD-STAGE VENT KOLEKOLE MEMBER PALEHUA MEMBER KAMAILEUNU AND LUALUALEI MEMBERSAXIS OF RIFT ZONE--Approximately locatedBOUNDARY OF CALDERA--Approximately located

Figure 5. Generalized surficial geology, Oahu, Hawaii (modified from Stearns, 1939; Langenheim and Clague, 1987; Presley and others, 1997).

Setting 11
Waianae Volcano

The Waianae Volcano is made up of the Waianae Volcanics that includes (1) the shield-stage lavas (Lualualei Member) of tholeiitic basalt, (2) the transitional or late shield-stage 

lavas (Kamaileunu Member) of mainly tholeiitic basalt, alkalic 

basalt, hawaiite, and rare ankaramite, (3) the postshield-stage 

lavas (Palehua Member) of hawaiite with minor alkalic basalt 

and mugearite, and (4) the younger postshield-stage lavas 

(Kolekole Member) of alkalic basalt (Sinton, 1986; Presley 

and others, 1997). The lava flows from the shield-stage Lualualei Member are mainly thin-bedded pahoehoe, ranging in 

thickness from about 5 to 75 ft and averaging about 25 ft. Lava 

flows of the Lualualei Member typically have dips of 4–14 ̊. 

Flows of the Kamaileunu Member are mainly pahoehoe and 

range in thickness from 10 to 120 ft, averaging about 40 ft. 

Flows of the Palehua Member are mainly aa and commonly 

have thicknesses ranging from 50 to 100 ft (Stearns and Vaksvik, 1935; Macdonald, 1940).

Potassium-argon dating of the Waianae Volcanics indicates an age of about 2.9 to 3.9 Ma, corresponding to the Pliocene epoch (Doell and Dalrymple, 1973; Presley, 1994; Presley and others, 1997). Exposed rocks of the Lualualei Member 

have ages of about 3.54 to 3.93 Ma, and exposed rocks of the 

Kamaileunu Member have ages of about 3.5 to 3.08 Ma (Guillou and others, 2000). Rocks of the Kolekole Member have an 

age of about 2.90 to 2.97 Ma (Presley and others, 1997).

Koolau Volcano

Lavas of the younger Koolau Volcano are subdivided into 

the Koolau Basalt and the Honolulu Volcanics. The Koolau 

Basalt consists primarily of shield-stage tholeiitic basalt, and 

the rejuvenated-stage Honolulu Volcanics consists of alkalic 

basalt, basanite, and nephelinite to melilitite (Langenheim and 

Clague, 1987).

Potassium-argon determinations of Koolau Basalt indicate an age of 1.8 to 2.6 Ma (Doell and Dalrymple, 1973), 

corresponding to the Pliocene epoch. The lava flows from the 

shield-stage Koolau Basalt are typically thin-bedded, with an 

average thickness of about 10 ft, and dip 3 to 10 degrees 

(Stearns and Vaksvik, 1935). Few soil or tuff layers interrupt 

the sequence of shield-stage lavas. Wentworth (1951) estimated that throughout the volcano, tuff lenses make up less 

than 1 or 2 thousandths of the section.

During the shield stage, lava flowing westward from 

the Koolau Volcano was deflected northward and southward 

by the preexisting Waianae Volcano. The central saddle area 

between the two volcanoes was formed by Koolau Basalt 

banking up against and being deflected by the Waianae Volcano. Within the central saddle, dips of the Koolau Basalt are 

invariably less than 5 and rarely more than 3 degrees (Stearns 

and Vaksvik, 1935, p. 34).

The Honolulu Volcanics erupted from more than 50 

vents, which are confined to the southeastern part of Oahu, 

and deposited on an already much-eroded, mature topography of the Koolau shield (Wentworth, 1951). The Honolulu 

Volcanics is of limited areal extent and is most notably marked 

by tuff cones such as Diamond Head, Punchbowl, and Koko 

Head. However, the Honolulu Volcanics also consists of cinder 

cones, ash deposits, spatter cones, and lava flows. Potassiumargon dating of various Honolulu Volcanics indicates ages 

from 0.031 Ma (Gramlich and others, 1971) to 1.13 Ma (Lanphere and Dalrymple, 1980) corresponding to the Pleistocene 

epoch. Age dates for the same flow, however, vary by an order 

of magnitude (Macdonald and others, 1983).

Volcanic-Rock Types

Volcanic rocks in Hawaii can be divided into three main 

groups on the basis of modes of emplacement: lava flows, 

dikes, and pyroclastic deposits. Lava flows that erupt from rift 

zones are either pahoehoe, which is characterized by smooth 

or ropy surfaces, or aa, which contains a massive central core 

sandwiched between rubbly clinker layers. Aa flows are typically more abundant at greater distances from eruptive centers 

(Lockwood and Lipman, 1987).

Dikes are thin, near-vertical sheets of massive rock that 

intrude existing rocks, such as lava flows. Dikes are commonly exposed by erosion within the rift zones of volcanoes, 

including the Waianae and Koolau Volcanoes (see for example 

Takasaki and Mink, 1985; Walker, 1987). In the central part of 

a rift zone, known as the dike complex, dikes may number as 

many as 1,000 per mile of distance and compose 10 percent 

or more of the total rock volume (Takasaki and Mink, 1985). 

The number of dikes decreases toward the outer edges of a rift 

zone. At the outer part of the rift zone, within the marginal 

dike zone, dikes usually constitute less than 5 percent of the 

total rock volume (Takasaki and Mink, 1985). 

Pyroclastic rocks form by explosive volcanic activity 

and are deposited by transport processes related to this activity. Pyroclastic rocks, such as ash, cinder, and spatter, can be 

deposited during all of the subaerial stages of eruption and 

probably form less than 1 percent of the mass of a Hawaiian 

volcano (Wentworth and Macdonald, 1953).

Geologic Modification Processes

The volcanoes that formed Oahu have undergone significant modification by processes such as subsidence, weathering, erosion, and deposition. These processes have played an 

important role in defining the geohydrologic setting of the 

Pearl Harbor area.

Subsidence.—Subsidence of Oahu was contemporaneous 

with shield development. Moore (1987) estimated that most 

Hawaiian volcanoes have subsided 6,500 to 13,000 ft since 

reaching the ocean surface. Andrews and Bainbridge (1972) 

suggested that submarine valleys off the northeastern coast of 

Oahu were originally subaerial features that have drowned as 

the island subsided. Some of these submarine valleys can be 

traced to depths of at least 6,600 ft below sea level (Shepard 

12  Numerical Simulation of the Effects of Valley-Fill Barriers in the Pearl Harbor Area, Oahu, Hawaii
and Dill, 1966), which may indicate that Oahu has subsided 

at least 6,600 ft relative to modern sea level. Hunt (1996) 

indicated that subsidence of Oahu occurred mainly prior to 

rejuvenated Koolau volcanism because Honolulu Volcanics 

either lies on or is intercalated only with the uppermost of the 

sedimentary units on the coastal plain.

Weathering and Erosion.—The processes of weathering and erosion contribute to the down-cutting of the original 

volcanic domes that formed Oahu. Although erosion can occur 

in the absence of weathering, weathering processes that break 

or soften rocks commonly enhance erosion.

Chemical weathering is the dominant weathering process 

on the island. Decomposition of rocks by chemical weathering 

is enhanced by high rainfall, abundant vegetation, and generally warm temperatures on Oahu. The effects of chemical 

weathering can extend to significant depths below the surface. 

The effects of chemical weathering proceed in a downward 

direction, resulting in a typical geologic profile consisting of 

several feet of soil and subsoil underlain by a few tens or hundreds of feet of saprolite, which is underlain by fresher volcanic rock. Saprolite is weathered rock retaining the structural 

and textural features of the parent rock. Hunt (1996) indicated 

that weathering intensity and saprolite thickness increase with 

rainfall, and estimated that saprolite is typically less than 100 

ft thick in areas where rainfall is less than 50 in/yr and about 

100 to 300 ft thick where rainfall is between 50 to 80 in/yr. 

Beneath stream channels, where percolating water is almost 

always present, depth of weathering may be considerably 

greater.

Erosion involves a group of processes that leads to the 

removal of earth materials from the surface. During the shield 

stage of volcanic activity, when the interval between successive lava flows is short, erosion of the land surface by streams 

likely is ineffective because the rocks generally are largely 

unaffected by weathering and highly permeable, and little rain 

runs off to the ocean. Following the shield stage of volcanic 

activity, however, during a period of volcanic quiescence, 

weathering of the land surface and erosion by streams can be 

significant. The rate of erosion by streams on Oahu has been 

estimated to range from about 1 to 6 in. per thousand years 

(Li, 1988). Erosion by streams has resulted in the formation 

of valleys that have been incised more than a thousand feet in 

the Koolau and Waianae Ranges. In general, the valleys in the 

Pearl Harbor area are in a youthful stage of dissection, and are 

narrow and V-shaped.

On Oahu, parts of the Waianae Volcano were eroded prior 

to being covered by Koolau Basalt. Thus, Waianae Volcanics 

is separated from Koolau Basalt by an erosional unconformity. 

Stearns and Vaksvik (1935) suggested that the Waianae Range 

had a well-developed stream pattern prior to the formation 

of the central saddle between the volcanoes because Koolau 

Basalt occupies a former amphitheater-headed valley.

Deposition.— Deposits of terrestrial and marine sediments and reef limestone form a coastal plain of varying width 

along the shore of Oahu. The coastal plain extends more than 

5 mi inland near Pearl Harbor. The onshore thickness of the 

coastal deposits generally is greatest at the coast and thins in 

an inland direction (Palmer, 1927; Palmer, 1946; Wentworth, 

1951; Visher and Mink, 1964; Dale, 1978). The sedimentary 

wedge is more than 1,000-ft thick along the southern coast 

near the entrance to Pearl Harbor.

Hydraulic Properties of the Rocks

The hydraulic properties of the various rock types control 

the ground-water flow system in the Pearl Harbor area. From 

a ground-water development standpoint, the main part of the 

ground-water flow system in the area exists in the dike-free 

volcanic rocks outside of the dike-intruded rift zones. Some 

rocks tend to impede the flow of ground water more than others, thereby creating barriers to flow.

Hydraulic Conductivity

Hydraulic conductivity is a quantitative measure of the 

capacity of a rock to transmit water. Hydraulic conductivity is 

the constant of proportionality in Darcy’s law, which relates 

specific discharge (discharge per unit area) to the hydraulic 

gradient:

 v = –K(dh/dl), (3)

where

 v = specific discharge [LT–1],

 K = hydraulic conductivity [LT–1], and

 dh/dl = hydraulic gradient [LL–1].

Darcy’s law generally is assumed to be applicable to regional 

ground-water flow analyses in Hawaii (see for example Souza 

and Voss, 1987; Oki, 1998; Gingerich and Voss, 2005). 

The hydraulic conductivity of a rock can be qualitatively 

described by permeability. Permeability describes the ease 

with which fluid can move through rock. The permeability 

of volcanic rocks is variable and depends on many factors, 

including the mode of emplacement and amount of weathering. Lava chemistry and topography also can affect permeability. Thicker flows generally are less permeable and form 

highly viscous lava on flat topography (Gingerich and Oki, 

2000).

Dike-Free Volcanic Rocks.—The permeability of the 

subaerial, shield-building, dike-free lava flows in the Pearl 

Harbor area generally is high. The main elements of lava 

flows contributing to the permeability are (1) clinker zones 

associated with aa flows, (2) voids along the contacts between 

flows, (3) cooling joints normal to flow surfaces, and (4) lava 

tubes associated with pahoehoe flows. The regional horizontal hydraulic conductivity of the dike-free volcanic rocks 

generally ranges from hundreds to thousands of feet per day 

(Soroos, 1973; Mink and Lau, 1980; Hunt, 1996). Because of 

the high permeability of the dike-free volcanic rocks, horizontal water-table gradients in these rocks are small (on the order 

of 1 ft/mi). Horizontal hydraulic conductivity in the lava flows 

may be anisotropic—several times greater parallel to the lava 

Setting 13
flows than perpendicular to the flows (see for example Nichols 

and others, 1996). 

In general, the vertical hydraulic conductivity of the 

dike-free lava flows may be hundreds of times less than the 

horizontal hydraulic conductivity. On the basis of a numerical-model analysis of the Pearl Harbor area, Souza and Voss 

(1987) estimated the ratio of horizontal to vertical hydraulic 

conductivity to be 200 to 1. 

Dikes.—Intrusive volcanic rocks include those rocks, 

such as dikes and sills, which formed by magma that cooled 

below the ground surface. Dikes associated with the rift zones 

of the Waianae and Koolau Volcanoes are the dominant intrusive rocks on Oahu, and are most abundant within the central 

area of the rift zones. Although the thickness of individual 

dikes generally is less than 10 ft, dikes are hydrologically significant because of their low permeability and their impounding effect on ground water. Ground-water levels in parts of 

the rift zone of the Koolau Volcano may be as high as 1,000 ft 

above sea level.

In general, the average hydraulic conductivity of a rift 

zone decreases as the number of dike intrusions within the rift 

zone increases. In addition, hydraulic conductivity is expected 

to be higher in a direction along the strike of the dikes rather 

than perpendicular to the strike. On the basis of a numerical 

model analysis, Meyer and Souza (1995) suggested that the 

average, effective hydraulic conductivity of a dike complex 

ranges from about 0.01 to 0.1 ft/d. These values reflect the 

influence of both the intrusive dikes as well as the lava flows 

between dikes. The hydraulic conductivity of the intrusive dike 

material was estimated to range from 10–5 to 10–2 ft/d (Meyer 

and Souza, 1995).

Weathering.—Weathering reduces the permeability of all 

types of volcanic rocks. The reduction of permeability may be 

attributed to secondary mineralization that clogs the original open spaces, or clays and colloids that precipitate from 

percolating water (Mink and Lau, 1980). An injection test 

conducted in weathered basalt beneath Waiawa Stream valley 

yielded a hydraulic conductivity of 0.058 ft/d (R.M. Towill 

Corporation, 1978). On the basis of laboratory permeameter 

tests on core samples, Wentworth (1938) estimated the hydraulic conductivity of weathered basalt to be between 0.083 and 

0.128 ft/d. Miller (1987) used the water-retention characteristics of core samples collected beneath pineapple fields of 

central Oahu to estimate the saturated hydraulic conductivity 

of saprolite and found values ranging from 0.0028 to 283 ft/d. 

The wide range of hydraulic-conductivity values estimated 

by Miller was attributed to the variability in macroporosity 

among samples.

Older Alluvium.—Wentworth (1951) classified the sedimentary rocks of Oahu into older, intermediate, and recent 

alluvial and marine formations. The sediments of greatest 

hydrologic significance are the old terrestrial sediments, which 

were created during the period of extensive erosion that carved 

deep valleys in the original volcanoes. Older alluvium forms 

deposits in deeply incised valleys and beneath the coastal 

plain of Oahu and is hydrologically significant because of its 

low permeability. The low permeability of older alluvium is 

caused by a reduction of pore space from the volume increase 

associated with weathering as well as mechanical compaction 

(Wentworth, 1951).

Wentworth (1938) estimated the hydraulic conductivity of 

three weathered alluvium samples with the use of a laboratory 

permeameter. Two of the samples had a hydraulic conductivity 

of less than 0.013 ft/d, and the third sample had a hydraulic 

conductivity of 1.08 ft/d. Eight samples classified as alluvium, 

without reference to weathering, produced a range of hydraulic conductivity from 0.019 to 0.37 ft/d (Wentworth, 1938).

Coastal Sedimentary Deposits.—The sedimentary deposits and underlying weathered volcanic rocks of the coastal 

plain form a low-permeability confining unit, called caprock, 

that overlies high-permeability volcanic rocks and impedes 

the seaward discharge of freshwater from the volcanic-rock 

aquifers. The caprock of southern Oahu includes terrestrial 

alluvium, marine sediments, calcareous reef deposits, pyroclastic rocks of the Honolulu Volcanics, and highly weathered 

basalt (Visher and Mink, 1964). In addition, massive aa cores 

or pahoehoe flows that are located near the coastal discharge 

zones also may impede the seaward discharge of fresh ground 

water. Although the permeability of the various components of 

the coastal caprock may vary widely, from low-permeability 

older alluvium and saprolite to cavernous limestone deposits 

with a hydraulic conductivity of thousands of feet per day, the 

overall effect of the caprock is one of low permeability (Visher 

and Mink, 1964). Souza and Voss (1987) modeled a vertical 

cross section of the Pearl Harbor ground-water area and estimated a caprock hydraulic conductivity of 0.15 ft/d (0.0457 

m/d). In their analysis, Souza and Voss treated the caprock as a 

homogeneous and isotropic unit, although significant heterogeneity may exist (Oki and others, 1998).

Storage

The effective porosity and specific storage of the rocks 

forming an aquifer affect the timing of the water-level 

response to natural or human-induced changes. The effective 

porosity represents that part of the total rock porosity that 

contributes to flow, and specific storage is a measure of the 

compressive storage of the rocks and fluid. Small values of 

effective porosity or specific storage will cause a rapid waterlevel response to changes in pumping or recharge, whereas 

large values of effective porosity or specific storage will cause 

a slow water-level response.

Total porosity of a rock is the ratio of the volume of 

void spaces to the total rock volume. Pore spaces in a layered sequence of lava flows may result from (1) vesicles 

(small spaces formed by the expansion of gas bubbles during the solidification of cooling lava), (2) joints and cracks, 

(3) separations between lava flows, (4) void spaces between 

fragmented rock, including aa clinker, and (5) lava tubes. Total 

porosity of the volcanic rocks on Oahu has been measured at 

different spatial scales using rock samples (Wentworth, 1938; 

Ishizaki and others, 1967), borehole photographic logging 

14  Numerical Simulation of the Effects of Valley-Fill Barriers in the Pearl Harbor Area, Oahu, Hawaii
(Peterson and Sehgal, 1974), and density logs from gravity 

surveys in underground tunnels (Huber and Adams, 1971). 

Total porosity estimates for volcanic rocks of Oahu range from 

less than 5 to more than 50 percent. Low porosity values may 

be associated with massive features, including dense flows, 

aa cores, and dikes, and high values may be associated with 

aa clinker zones. Effective porosity, which includes only the 

hydraulically interconnected pore spaces, for the dike-free 

volcanic rocks of Oahu may be up to an order of magnitude 

less than total porosity. 

Williams and Soroos (1973) analyzed aquifer-test data 

from wells in the Pearl Harbor area and estimated specific 

storage to range from about 10–4 to 10–7 ft–1. Specific storage 

also may be estimated from the compressibilities of water and 

the rock matrix (see for example Freeze and Cherry, 1979).

 Sf = γf (B + nβ), (4)

where

 Sf = freshwater specific storage [L–1],

 n = effective porosity of the rocks,

 γf = freshwater specific weight [ML–2T–2],

 B = compressibility of rock matrix [LT2M–1], 

and

 β = compressibility of water [LT2M–1].

The compressibility of water is about 2.1 × 10–8 ft2/lb (4.4 

× 10–10 Pa–1) (Freeze and Cherry, 1979), and the compressibility of the basaltic rock matrix in the Pearl Harbor area was 

estimated to be 1.2 × 10–7 ft2/lb (2.5 × 10–9 Pa–1) (Souza and 

Voss, 1987). The specific weight of freshwater is about 62.4 

lb/ft3. For an effective porosity of 0.02 the specific-storage 

value is about 7.5 × 10–6 ft–1, and for an effective porosity of 

0.2 the specific-storage value is about 7.8 × 10–6 ft–1.

Dispersion Characteristics

Mixing of freshwater with underlying saltwater in an 

aquifer creates a transition zone of brackish water. The extent 

of mixing in an aquifer is dependent on factors including the 

ground-water velocity and the aquifer dispersivity, which has 

units of length. High values of dispersivity, all other factors 

being equal, result in greater mixing. Dispersivity values generally are larger in the (longitudinal) direction of flow relative 

to directions transverse to flow, and also may be controlled by 

aquifer anisotropy. Few reported dispersivity values are available for Oahu. Meyer and others (1974) estimated the dispersivity to be about 200 ft for the volcanic-rock aquifer in the 

Honolulu area, and this value likely represents a longitudinal 

dispersivity. Using a cross-sectional numerical model, Souza 

and Voss (1987) estimated the longitudinal and transverse 

dispersivities of the Pearl Harbor area to be 250 and 0.82 ft, 

respectively. Vertical discretization of the cross-sectional mesh 

was variable, and was finest (49 ft) where concentration gradients were greatest; horizontal discretization also was variable, 

and was finest (984 ft) near areas of converging flow.

Valley-Fill Barriers

Following the period of extensive erosion during which 

valleys were deeply incised, some valleys were filled in by 

marine and terrestrial sediments during a period when relative 

sea level was higher than it is today. The sedimentary deposits that filled stream valleys along with the weathered rock 

beneath the valley bottoms may extend below the groundwater table and generally have lower overall permeability than 

the main dike-free volcanic-rock aquifers of Oahu. Thus, 

these valley-fill features tend to act as barriers to ground-water 

flow. 

Toward the lower reaches of the valleys, below an altitude 

of about 30 ft, valley-fill deposits may consist of terrestrial 

sediments that interfinger with marine sediments and limestone units. The geologic sequence reflects changes in relative 

sea level associated with island subsidence and glacioeustatic 

sea-level fluctuations during the Pleistocene (Stearns and 

Chamberlain, 1967). Inland, above an altitude of about 30 ft, 

the base of the valley-fill material typically consists of highly 

weathered and compact older alluvium, which is mantled with 

more recent, unconsolidated alluvium and colluvium. Older 

alluvium consists of terrestrial sediments, varying in size from 

fine-grain particles to boulders, which have been weathered 

and compacted into a soft coherent mass (Wentworth, 1951). 

The older alluvium may be hundreds of feet thick at lower 

altitudes, but at altitudes above about 400 to 600 ft, older alluvium may be nonexistent. 

Wells drilled in and near valley mouths provide evidence 

for a lower stream base level than exists today. For example, 

Palmer (1927, 1946) used information from wells to define 

structural contours for the top of the Koolau Basalt beneath the 

coastal sedimentary deposits in the Honolulu area (fig. 6), and 

identified reentrant forms that represent the original, subaerially formed valley incisions. The reentrant near the mouth of 

Nuuanu Stream valley suggests that this valley was incised 

when base level was at least 800 ft lower than it is today. The 

valley likely was incised to a depth greater than 800 ft; however, well coverage across the valley mouth is insufficient to 

define the original valley cross section and maximum depth of 

incision. Within the original channels of Manoa, Nuuanu, and 

Kalihi Stream valleys of Honolulu, the thickness of the valleyfill deposits likely exceeds 1,000 ft. The valley-fill deposits 

and underlying weathered volcanic rock associated with 

Manoa, Nuuanu, and Kalihi Streams form effective valley-fill 

barriers that affect the movement of ground water in the Honolulu area. Water levels on opposite sides of valley-fill barriers 

in the Honolulu area have differed by several feet at times. 

In the Pearl Harbor area, several valley-fill barriers, 

including those associated with the larger stream valleys of 

Kipapa and Waikele, Waiawa, Waimalu, and North Halawa 

Streams, may impede the flow of ground water. Measured 

water levels on opposite sides of the stream valleys in the 

Pearl Harbor area do not definitively indicate the presence of 

hydrologically effective valley-fill barriers such as those in the 

Valley-Fill Barriers 15
Palolo

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anoa

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EXPLANATION 

STRUCTURAL CONTOUR OF TOP OF VOLCANIC- 

 ROCK AQUIFER, IN FEET BELOW MEAN 

 SEA LEVEL--Interval 100 feet 

TOPOGRAPHIC DIVIDE 

!

!

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 map 

Figure 6. Structural contours of the top of the volcanic-rock aquifer in the Honolulu area, Oahu, Hawaii (modified from Palmer, 1927, 

1946).

16  Numerical Simulation of the Effects of Valley-Fill Barriers in the Pearl Harbor Area, Oahu, Hawaii
Honolulu area. The effectiveness of the valley-fill barriers in 

the Honolulu area may be related to the steeper topography 

and longitudinal slopes of the valleys in the Honolulu area 

relative to the Pearl Harbor area. The depths of the valley-fill 

barriers also likely are related to the availability of water that 

causes weathering below the stream channels, the location of 

the water table (and relative sea level), and the characteristics 

and structure of the rocks beneath the stream channels.

Drilling, geophysical, and hydrologic information from 

well 2401-01 (fig. 7), drilled about 600 ft downstream of the 

confluence of Kipapa and Waikele Streams to a depth of about 

200 ft below mean sea level, indicates the presence of very 

weathered basalt, which grades into less weathered basalt, 

extending below sea level (Eyre, 1983). From aquifer-test 

analyses, Eyre (1983) estimated a hydraulic-conductivity value 

of about 50 ft/d for the volcanic rocks penetrated by the well. 

In Waiawa Stream valley, a borehole log and geophysical information from resistivity and seismic surveys indicate 

the presence of a valley-fill barrier that partly penetrates the 

aquifer (R.M. Towill Corporation, 1978). Beneath the floor of 

Waiawa Stream valley is a sequence consisting of (1) an upper 

layer of soil and recent alluvium that is less than 10 ft thick, 

(2) older alluvium that is tens of feet thick in places, and (3) 

weathered basalt that becomes less weathered with depth. The 

weathered basalt beneath the studied site, which was at an altitude of about 190 ft, extends to a depth of 50 to 100 ft below 

sea level (fig. 8) (R.M. Towill Corporation, 1978), although 

subtle weathering effects that affect rock permeability may 

extend even deeper. 

Waimalu Stream valley also may form a partially penetrating barrier to ground-water flow. Available drilling logs 

from wells in Waimalu Stream valley indicate the presence of 

sedimentary material and possibly weathered volcanic rocks to 

depths greater than 200 ft below mean sea level. 

A valley-fill barrier formed beneath North Halawa Stream 

valley (Hunt, 1996) separates the Pearl Harbor area from the 

Moanalua ground-water area to the east. The alluvial and colluvial material that fills the bottom of the valley may penetrate 

below sea level (Izuka, 1992). In addition, weathered volcanic 

rocks may extend beneath the valley-fill material and impede 

the flow of ground water between the Moanalua and Pearl 

Harbor areas. 

Effects of Valley-Fill Barriers on Water Levels

As part of this study, water levels from wells on opposite 

sides of Waiawa Stream valley were measured to determine 

if differences in water-level recovery associated with shutting 

off a large-capacity production well could be measured. The 

Waiawa Shaft (well 2558-10, fig. 7), which is located on the 

west side of Waiawa Stream valley, was shut off for a period of 

about 2 days. During the shut-off period, water was supplied 

by other sources several miles away from Waiawa Shaft. 

Waiawa Shaft is a Maui-type shaft (Stearns and Vaksvik, 1935) that consists of a 30-degree inclined shaft, which 

originates at a land-surface altitude of about 140 ft near the 

western valley wall within Waiawa Stream valley and leads 

down to a pump room at an altitude of about 30 ft, a sump 

excavated beneath the pump-room floor to about 20 ft below 

mean sea level, and a 1,700-ft long infiltration tunnel extending generally northward from the sump. Waiawa Shaft has a 

large-capacity infiltration tunnel and is capable of withdrawing greater than 15 Mgal/d partly by skimming water from the 

top of the freshwater lens. The infiltration tunnel is 12 ft wide 

by 12 ft high near its entrance, which has an invert altitude of 

about 4 ft below mean sea level, and tapers to about 7 ft wide 

by 10 ft high near its terminus, which has an invert altitude of 

about 4 ft above mean sea level (Oki and others, 1990).

During the week prior to the 2-day shut-off of Waiawa 

Shaft in February 2005, withdrawal from Waiawa Shaft 

was steady at about 10 Mgal/d. Rainfall during February 

15 through 25, 2005 at a rain gage near Mililani was 0.19 

in. (National Weather Service, 2005), which is unlikely to 

have affected ground-water levels much. Water levels were 

monitored at wells 2659-04 and 2459-26 on the west side of 

Waiawa Stream valley, and at well 2557-04 on the east side of 

the valley (fig. 7). During the 2-day period when Waiawa Shaft 

was shut off, water levels on each side of Waiawa Stream valley appeared to recover, although the measured recoveries are 

somewhat obscured by the hydrologic effects of barometric 

(atmospheric) pressure (fig. 9). 

Barometric pressure at a particular site is determined by 

the weight of the air column above that site. Pressure changes 

at a site are caused by dynamical (air motion) and thermal 

(temperature) effects that change the weight of the air column 

above the site. Variations of barometric pressure can occur 

over time scales ranging from seconds to several years. Over 

short time scales of seconds to minutes, sensitive barometers 

may measure high-frequency pressure variations caused by 

local gusts of wind. On a weekly to annual time scale, migratory low- or high-pressure systems can cause relatively large 

pressure variations (in excess of 0.3 ft of water) over a region. 

In Hawaii, barometric pressure at the surface shows a marked 

semidiurnal variation which is attributed to absorption of 

radiation by water vapor and ozone in the upper atmosphere 

(Whiteman and Bian, 1996; Chapman and Lindzen, 1970). 

Unlike tidal phenomena, the semidiurnal variation in barometric pressure is not purely sinusoidal in nature. The amplitude 

of the semidiurnal barometric-pressure variation at surface 

sites in Hawaii is typically about 0.05 ft of water.

The effects of barometric pressure on measured water 

levels were removed using a one-dimensional numerical 

model that accounts for air flow in the unsaturated zone, 

vertical flow of water in the aquifer, and vertical loading 

of the aquifer (Oki, 1997). The one-dimensional numerical 

model removes low-frequency barometric-pressure effects as 

well as the semidiurnal barometric-pressure effects on water 

levels. The semidiurnal variations in water levels caused by 

barometric-pressure changes are generally a few hundredths of 

a foot in amplitude, and are greater in well 2659-04 (which has 

the greatest depth to water of the three wells) than in wells 

2459-26 or 2557-04. 

Valley-Fill Barriers 17
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2006-01 to -10 

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Base modified from U.S. Geological Survey National Hydrography Dataset, Albers equal area projection,standard parallels 21o19'40" and 21o38'20", centralmeridian 157o58', datum NAD83. Relief from U.S.Geological Survey digital elevation models, 1:24,000 

1,200

EXPLANATION 

STRUCTURAL CONTOUR OF TOP OF VOLCANIC-ROCK AQUIFER, IN FEET BELOW MEAN SEA LEVEL--Interval is 100 feet for contour values less than 1,300  feet and 330 feet (100 meters) for contour values greater than 1,300 feetWELL AND WELL NUMBER H

2558-10

100

Figure 7. Selected wells with water-level, salinity, or geologic information used in this study, and structural contours of the top of the volcanic-rock aquifer in the Pearl Harbor area, Oahu, Hawaii. Structural contours modified from Palmer (1946), Wentworth (1951), Visher and Mink (1964), and Gregory (1980).

18  Numerical Simulation of the Effects of Valley-Fill Barriers in the Pearl Harbor Area, Oahu, Hawaii
0

-50

-100

50

100

150

200

250

EAST WEST

0 100 200 300 400 500 600 700 800

DISTANCE, IN FEET 

ALTITUDE, IN FEET RELATIVE TO MEAN SEA LEVEL 

Resistivity survey location Resistivity survey 

location

Borehole

Waiawa 

Stream

Older alluvium

Soil and

recent alluvium 

Weathered basalt, decreased 

weathering with depth 

Slightly weathered basalt 

Section

Location

Oahu

Figure 8. Cross section of Waiawa Stream valley, Oahu, Hawaii (modified from R.M. Towill Corporation, 1978).

Valley-Fill Barriers 19
22.8

22.7

22.6

22.5

22.4

21.2

21.1

21.0

20.9

20.8

19.8

19.7

19.6

19.5

19.4

02/15/05 02/16/05 02/17/05 02/18/05 02/19/05 02/20/05 02/21/05 02/22/05 02/23/05 02/24/05 02/25/05

Well 2659-04 (west of Waiawa Stream) Waiawa Shaft 

shut off 

Well 2459-26 (west of Waiawa Stream) 

Well 2557-04 (east of Waiawa Stream) 

WATER LEVEL, IN FEET ABOVE MEAN SEA LEVEL 

Figure 9. Measured water levels in wells near the Waiawa Shaft (2558-10), which was shut off during February 23-

25, 2005, Pearl Harbor area, Oahu, Hawaii. Shaded area represents shut-off period.

20 Numerical Simulation of the Effects of Valley-Fill Barriers in the Pearl Harbor Area, Oahu, Hawaii
The resulting water levels with barometric-pressure 

effects removed indicate a recovery on the east side of Waiawa 

Stream valley (well 2557-04) (fig. 10). (The recovery associated with shutting off Waiawa Shaft also is indicated in wells 

2659-04 and 2459-26 on the west side of Waiawa Stream valley, although the water levels in these wells with barometricpressure effects removed are not shown.) Thus, on the basis 

of water-level information, the Waiawa valley-fill barrier is not 

a totally effective hydrologic barrier in the vicinity of Waiawa 

Shaft. Ground-water withdrawal from the western side of 

Waiawa Stream valley measurably affects water levels on the 

eastern side of the valley because the ground-water pressure 

reduction caused by withdrawal is propagated either beneath 

or through the valley-fill barrier.

Ground-Water Flow System

The most important source of fresh ground water on 

Oahu is from the freshwater lens in dike-free volcanic rocks in 

the Pearl Harbor area (fig. 11). The main ground-water system 

in the Pearl Harbor area consists of a lens-shaped freshwater 

body, an intermediate transition zone of brackish water, and 

underlying saltwater. Several geologic features form boundaries of the freshwater-lens system of the Pearl Harbor area or 

impede the flow of ground water within the system. Features 

that form boundaries of the freshwater-lens system include 

dikes and the southern Schofield ground-water dam; features 

that may impede flow within the system include valley-fill 

barriers, the coastal caprock that thickens in a seaward direction, and the Waianae confining unit that separates Waianae 

Volcanics and Koolau Basalt.

Freshwater Lens

The freshwater lens in the Pearl Harbor area forms 

because of the density difference between freshwater and 

underlying saltwater. For hydrostatic conditions, the depth at 

which the brackish water in the transition zone has a salinity 

about 50 percent that of ocean water is sometimes estimated 

from the Ghyben-Herzberg principle (see for example Freeze 

and Cherry, 1979). The Ghyben-Herzberg principle describes 

a freshwater-saltwater relation for conditions in which the two 

fluids do not mix (no transition zone) and freshwater flow is 

horizontal. For these conditions, the freshwater-lens thickness 

below sea level is directly proportional to the height of the top 

of the freshwater above sea level. In principle, at a place where 

the water table stands 1 foot above sea level, for example, 40 

feet of freshwater will be below sea level, and the freshwater 

lens will thus be 41 feet thick. This relation exists because 

ocean water is about one-fortieth denser than freshwater. In 

the dike-free volcanic rocks of the Pearl Harbor area, mixing 

of freshwater with underlying saltwater creates a brackishwater transition zone that may be hundreds of feet thick. (For 

the purposes of this report, brackish water is considered to be 

water with salinity that ranges from greater than 2 percent to 

less than 100 percent ocean-water salinity.) 

The water table in the dike-free volcanic rocks is less 

than a few tens of feet above sea level. In general, the altitude 

of the water table in the dike-free volcanic rocks is lowest 

near the coast and increases in an inland direction at a rate of 

about 1 ft/mi, although local variations may exist near areas of 

converging flow caused by springs and pumping from wells. 

Within the dike-free volcanic rocks, freshwater generally flows 

from inland areas to coastal discharge areas (fig. 12). Although 

freshwater flow is predominantly horizontal in the dike-free 

volcanic rocks, the flow may have an upward component in 

some areas. For example, freshwater may flow upward to sites 

of discharge near the land surface at the Pearl Harbor springs. 

Within the uppermost limestone unit in the caprock, the water 

table generally is less than a few feet above sea level.

The low-permeability coastal caprock along southern 

Oahu acts as a confining unit that impedes the discharge of 

fresh ground water from the aquifer as well as the inflow 

of saltwater into the aquifer. The caprock of southern Oahu 

extends offshore, beyond the seaward extent of the freshwater 

lens. The freshwater-lens system in the dike-free volcanic 

rocks is mainly unconfined inland from the caprock. Within 

the caprock, highly permeable limestone units may be confined by low-permeability sedimentary deposits, although the 

uppermost limestone unit of the caprock is unconfined and 

contains brackish water (see for example Bauer, 1996; Oki and 

others, 1998).

A saltwater-circulation system exists beneath the freshwater lens. Saltwater flows landward in the deeper parts of the 

aquifer, rises, and then mixes with seaward-flowing fresher 

water (fig. 12). This mixing creates the brackish-water transition zone. 

Recharge

Recharge to the freshwater-lens system in the Pearl Harbor area is from infiltration of rainfall and irrigation water, and 

discharge from upgradient ground-water bodies. Upgradient 

ground-water bodies that recharge the freshwater-lens system 

of the Pearl Harbor area include the Koolau and Waianae rift 

zones, the Schofield ground-water area, and the Moanalua 

ground-water area (fig. 11). Oki (1998) estimated that during 

the 1950s, about 62 percent of the discharge from the Schofield ground-water area flowed toward the Pearl Harbor area, 

with the remaining 38 percent flowing northward. 

Shade and Nichols (1996) developed regression equations 

relating rainfall and recharge in the Pearl Harbor area using 

water-budget information from Giambelluca (1983, 1986) 

(table 1). Shade and Nichols used these regression equations 

to estimate the distribution of recharge in the Pearl Harbor 

area for predevelopment conditions, and indicated that total 

predevelopment recharge to the Pearl Harbor area was about 

280 Mgal/d (including recharge from the rift zones and the 

Schofield ground-water area) (fig. 13). The adjacent Moanalua 

Ground-Water Flow System  21
02/15/05 02/16/05 02/17/05 02/18/05 02/19/05 02/20/05 02/21/05 02/22/05 02/23/05 02/24/05 02/25/05

0.0

0.00

-0.2

-0.1

0.1

0.2

20.8

20.9

21.0

21.1

WATER LEVEL, 

IN FEET RELATIVE TO MEAN SEA LEVEL 

RELATIVE BAROMETRIC PRESSURE, 

IN FEET OF WATER 

RESIDUAL WATER LEVEL, 

IN FEET RELATIVE TO ARBITRARY DATUM 

WATER LEVEL AT WAIAWA SHAFT, 

IN FEET RELATIVE TO MEAN SEA LEVEL 

21.2

-0.10

-0.05

0.05

0.10

15

16

17

18

19

20

21

22

RELATIVE BAROMETRIC PRESSURE, WAIMANO OBSERVATION WELL 2557-04 

MEASURED WATER LEVEL, WAIMANO OBSERVATION WELL 2557-04 

SIMULATED WATER-LEVEL RESPONSE TO BAROMETRIC PRESSURE, 

 WAIMANO OBSERVATION WELL 2557-04 

RESIDUAL WATER LEVEL WITH BAROMETRIC-PRESSURE EFFECTS 

 REMOVED, WAIMANO OBSERVATION WELL 2557-04 

MEASURED WATER LEVEL, WAIAWA SHAFT 2558-10 

EXPLANATION 

Figure 10. Measured and simulated barometric-pressure response in Waimano observation well 2557-04, Oahu, 

Hawaii, during February 15, 2005 through February 25, 2005. Barometric-pressure response was simulated with a 

pneumatic diffusivity of 1.0x108 ft2/d, vertical hydraulic conductivity of 10 ft/d, specific storage of 1.0x10–5 ft–1, loading 

efficiency of 0.5, and specific yield of 0.5. 

22  Numerical Simulation of the Effects of Valley-Fill Barriers in the Pearl Harbor Area, Oahu, Hawaii
Kaimuki 

North Schofield barrier 

SCHOFIELD 

NORTH-CENTRAL OAHU 

SOUTHEASTERN OAHU 

Kawailoa 

Waialua Mokuleia 

WAIANAE RIFT ZONE 

Pearl Harbor 

SOUTHERN OAHU 

KAHUKU

KOOLAU 

RIFT 

ZONE 

Moanalua 

Wailupe-Hawaii Kai Waialae 

Kalihi Beretania 

South Schofield barrier 

Ewa

158o10'

157o50'

157o40'

21o40'

21o30'

21o20'

158o

!

!

!

!

!

!

!

!

!

!

!

! !

Kahuku Point 

Makapuu

Point

Diamond Head 

Barbers

Point

Kaena

Point

Makaha

Ewa

Waialua

Haleiwa

Laie

HONOLULU

Waipahu

Pearl

City

Aiea

Kailua

Kaneohe

Schofield

Barracks Wahiawa

Waimanalo

Bay

KANEOHE

BAY

MAMALA BAY 

EXPLANATION

BOUNDARY OF GROUND-WATER AREA BOUNDARY OF GROUND-WATER SUBAREA TOPOGRAPHIC DIVIDE DIRECTION OF GROUND-WATER MOVEMENT 

FRESHWATER-LENS SYSTEMDIKE-IMPOUNDED SYSTEMSCHOFIELD AREA OF HIGH WATER LEVELS

Pearl

 Harbor 

00

4 MILES 2

2 4 KILOMETERS 

Base modified from U.S. Geological Survey National Hydrography Dataset, Albers equal area projection,standard parallels 21o19'40" and 21o38'20", centralmeridian 157o58', datum NAD83.

Figure 11. Ground-water areas and generalized directions of ground-water movement, Oahu, Hawaii.

Ground-Water Flow System  23
Land surface

water table Spring Pacific

Ocean

FRESHWATER 

BRACKISH WATER 

(TRANSITION ZONE) 

SALTWATER 

FRESHWATER 

LENS

EXPLANATION 

VOLCANIC ROCK 

SEDIMENTARY DEPOSITS 

LOW-PERMEABILITY 

 MATERIAL 

FRESHWATER 

BRACKISH WATER 

SALTWATER 

GENERAL DIRECTION OF

 GROUND-WATER FLOW 

 Freshwater 

 Saltwater 

Figure 12. Generalized cross section of ground-water flow in the Pearl Harbor 

area, Oahu, Hawaii.

Table 1. Relations between annual rainfall and annual recharge for different land uses, Pearl Harbor area, Oahu, Hawaii (Shade and 

Nichols, 1996).

Land use Relation1 Coefficient of 

determination, r2

Range of annual rainfall 

for indicated relation, in 

inches

Predevelopment (before 1880)

Recharge = 0.06p + 3.4

Recharge = 0.78p – 28.0 

Recharge = 0.60p – 15.0

Recharge = 0.89p – 56.0

0.09

0.93

0.24

0.91

20-43

43-95

95-152

> 152

Development (after 1880)

Non-agricultural

Recharge = 0.41p – 5.7

Recharge = 0.78p – 28.0 

Recharge = 0.60p – 15.0

Recharge = 0.89p – 56.0

0.57

0.93

0.24

0.91

14-60

60-95

95-152

> 152

Pineapple Recharge = 0.935p – 13.54 0.98 > 15

Sugarcane (drip) Recharge = 0.64p + 11.1 0.89 > 0

1

Recharge is in inches per year; p is rainfall, in inches per year.

24  Numerical Simulation of the Effects of Valley-Fill Barriers in the Pearl Harbor Area, Oahu, Hawaii
0

0

2 4 MILES 

2 4 KILOMETERS 

EXPLANATION 

!

!

!

!

!

!

!

!

Waianae 

Ewa 

Waialua 

HONOLULU

Waipahu 

Kailua

Kaneohe

Wahiawa 

21o20'

158o10'

157o50'

157o40'

21o40'

21o30'

158o

Base modified from U.S. Geological Survey 

digital data, 1:24,000, 1983, Albers equal area

projection, standard parallels 21o15' and 21o45',

central meridian 157o59'

GROUND-WATER RECHARGE, IN INCHES PER YEAR 

 Greater than or equal to 150 

 Greater than or equal to 100 and less than 150 

 Greater than or equal to 50 and less than 100 

 Greater than or equal to 25 and less than 50 

 Greater than or equal to 10 and less than 25 

 Less than 10 

Kahuku Point 

Makapuu

Point

Diamond

Head

Barbers

Point

Kaena

Point

KANEOHE

BAY 

Pearl 

 Harbor 

MAMALA BAY 

MAUNALUA BAY

Figure 13. Distribution of ground-water recharge for predevelopment land use, Oahu, Hawaii (modified from Shade and Nichols, 

1996).

Ground-Water Flow System  25
ground-water area to the east of the Pearl Harbor area received 

about 28 Mgal/d recharge for predevelopment conditions. 

Since about 1900, land use in the Pearl Harbor area 

has undergone significant changes (see for example Oki and 

Brasher, 2003), and these changes have had an effect on the 

hydrologic budget of the area. Irrigation on large-scale sugarcane plantations and suppressed evapotranspiration associated 

with pineapple plants generally have resulted in increased 

recharge relative to predevelopment conditions. Variations in 

rainfall (fig. 14) also have affected the amount of recharge in 

the Pearl Harbor area over time. During the 1940s and late 

1970s, rainfall was less than average, whereas during the 

1960s rainfall was above average (fig. 14). During the 1950s, 

rainfall was near the long-term average. 

Relations from Shade and Nichols (1996) (table 1) were 

used in this study to estimate recharge from rainfall for different time periods and land uses. Estimated recharge over 

time was used as input to the numerical ground-water model 

described later in this report. 

Discharge

Discharge from the Pearl Harbor area is in the form of 

ground-water withdrawals from pumped wells, discharge to 

onshore springs inland from Pearl Harbor, and diffuse seepage 

through the caprock to Pearl Harbor and the ocean. Withdrawals from pumped wells and discharge from the Pearl Harbor 

springs have been measured, although records are incomplete 

for some time periods and locations. Diffuse seepage through 

the caprock has not been measured.

Withdrawals from Wells

Withdrawals from drilled wells in the Pearl Harbor area 

began following the 1879 discovery of free-flowing artesian 

water in the southwestern part of the area. Early records of 

withdrawals are not available, but withdrawals were probably about 5 Mgal/d during the 1880s (Mink, 1980). Records 

of withdrawals from the volcanic-rock aquifer from 1890 to 

about 1920 are incomplete, although information is available 

for when wells were drilled. After about 1920, records of withdrawals from the volcanic-rock aquifers in the Pearl Harbor 

area are more complete. 

During the early period of ground-water development, 

most of the water was used for sugarcane cultivation. For this 

study, sugarcane-plantation withdrawals from individual well 

fields during the early period of development from 1890 to 

about 1920 were estimated if data were not available. Withdrawals from individual well fields for early periods when 

data were unavailable were estimated from either (1) a linearregression equation relating annual rainfall from a nearby rain 

gage (State key number 741 or 750) and annual withdrawal 

from the well field during a period for which data were available, or (2) the average annual withdrawal rate from the well 

field during a subsequent period for which data were available. 

The latter method was used for cases in which the correlation 

coefficient of the relation between annual rainfall and annual 

withdrawal rate was between about 0.6 and –0.6. Estimated 

annual withdrawals for a well were disaggregated into 

monthly withdrawals using mean ratios of monthly-to-annual 

withdrawal from the same well for a subsequent period with 

available data. Estimated withdrawal rates also were adjusted 

proportionally to account for the number of wells existing in 

the well field during the estimation period relative to when 

data were available. 

Ground-water withdrawals from the volcanic rocks of 

the Pearl Harbor area (including the Ewa-Kunia, WaipahuWaiawa, and Waimalu management systems) increased after 

about 1895 as areas used for sugarcane cultivation expanded. 

From 1910 through 1939, average withdrawal was about 157 

Mgal/d (fig. 15). During the war years 1940 through 1945, 

average withdrawal increased to about 191 Mgal/d. From 

1946 through 1959, average withdrawal decreased to about 

158 Mgal/d, which was about the same as the pre-war average. During the 1960s, average withdrawal increased to 184 

Mgal/d, and during the 1970s, average withdrawal increased 

further to 224 Mgal/d. After the 1970s, average withdrawal 

began to decline. From 1996 through 2001, following the closure of the last remaining sugarcane plantation in the area in 

1995, average ground-water withdrawal from the Pearl Harbor 

area was 104 Mgal/d. Much of the reduction in ground-water 

withdrawal after 1980 was from the western part of the Pearl 

Harbor area, in the Waipahu-Waiawa management system (fig. 

15). 

Ground-water withdrawals from the coastal caprock 

mainly are from the upper-limestone unit of the caprock. Prior 

to the closure of Oahu Sugar Co., most of the withdrawals 

from the caprock were for irrigation of sugarcane. Since the 

closure of Oahu Sugar Co., ground water from the caprock has 

mainly been used for landscape and golf-course irrigation and 

industrial purposes. 

Pearl Harbor Springs

The Pearl Harbor springs consist of a group of springs 

inland from the shore of Pearl Harbor near the inland margin of the caprock. The five major springs have been named, 

from east to west, Kalauao, Waiau, Waimano, Waiawa, and 

Waikele Springs (fig. 1) and are described in detail by Visher 

and Mink (1964). Schuyler and Allardt (1889) reported that 

the largest flows were from a bluff at an altitude of about 20 to 

25 ft. Visher and Mink (1964) indicated that the main spring 

discharges are from areas where volcanic rocks are exposed 

at a break in slope of the land surface. Water also discharges 

as diffuse seeps where the caprock is thin, where erosion has 

exposed the volcanic rocks, and through alluvium into stream 

channels incised below the level of the existing head in the 

aquifer. Historically, the spring discharge was used for wetland 

crops such as rice. The discharge is currently used for watercress cultivation as well as for industrial purposes. 

26  Numerical Simulation of the Effects of Valley-Fill Barriers in the Pearl Harbor Area, Oahu, Hawaii
Base modified from U.S. Geological Survey National

Hydrography Dataset, Albers equal area projection, standard parallels 21o19'40" and 21o38'20", central meridian 157o58', datum NAD83. 

EXPLANATION

RATIOS OF AVERAGE RAINFALL DURING INDICATED PERIOD TO LONG-TERM (1916-1983) MEAN ANNUAL RAINFALL, IN PERCENT, ATSELECTED RAIN GAGES (VALUES INDICATED NEXT TO SYMBOL) LESS THAN 90 PERCENT GREATER THAN OR EQUAL TO 90  PERCENT AND LESS THAN OR  EQUAL TO 110 PERCENT  GREATER THAN 110 PERCENT

HHH

80

75

79

84

80

88

80

82

86

85

85 80

82

83 82 82

81

80

80

81

79

76

79

79

81

75

76

85

85

85

77 84

85

81

81

87 82

73 81

81

79

77

84

80

83

82

86

79

83

86

83

85

89

84 90

76

80

75

82

72

77

77

87

83

8277

81

86

83

84

89

88

82

86

86

86

88

89

77

89

86

86

89

85

84

88

H

H H

HH

H

H

H

H

H

H H

H H H H

H

H

H

H

H

H

H

H

H

H

H

H H

H

H H

H

H

H

HH

H H H

H

H

H

H

H

H

H

HH H

H

H

H

H

H

H

H

H

H

H H

H

H

HH

H

H

HH

H

H

H

H

H

H H

H H

H

H

H

H

H

H

H

H

H

95

94 94

92

92

90

90

93

90

94

93

98

96

98

90

97

92

91

96

91

94

95

92

90

92

90

91

H

H H

H

H HH

H

H

H H

H

H

H

H

H H

H

H

H H

H H

H

H

H H

84

Kahuku Point

Makapuu

Point

Diamond Head

Barbers

Point

Kaena

Point

Waimanalo

Bay

KANEOHE

BAY

MAMALA BAY

Pearl 

 Harbor

Waikiki

158o10'

157o50'

157o40'

21o40'

21o30'

21o20'

158o

1940-49

76 H

98

99 100

109

110

104

108

102

103

108

97

93

102

101

102

93

99 97 100

97

100

99

102

99

99

102

97

96

97

100

99

107

93 105

107

106

96

106

108

106 103

98

98

101

100

103

102

103

97

95

101

101

99

108

107

104

103

108

101

98

110

99

109

110

104

107

100 101

101

103

109

107

107

95

101

105

108

106

108

107

110

102

99

99

100

99

100

H

H H H

H

HH

H

H

H

H

H

H

H

H

H H H

HH

H

H

H

H

H

H

H

H

H

H

H

H

H H

H

H

H

H

H

H H H

H

H HH

H H

H

H H

H

H

H

H

HH

H

H

H

HH

H

H

H

H

H H H

H

H

H

H

H

HH

HH H H

H

H

H

H

H

H

H

111

113 111

111

111

114

110

113

112

117 117

116

117

111

110

122

119

112

117 113 124

110

115

112 111

114

111

113

127

H

H H

H

H

H

H

H

H HHH H

H

H

H

H

H

H H H

H

H H H

H

HH

H

Kahuku Point

Makapuu

Point

Diamond Head

Barbers

Point

Kaena

Point

Waimanalo

Bay

KANEOHE

BAY

MAMALA BAY

Pearl 

 Harbor

Waikiki

158o10'

157o50'

157o40'

21o40'

21o30'

21o20'

158o

1930-39

90 89

72

88

86

86

89

89

86

90 90

90

82

H H

H

H

H

H

H

H

H

H H H

H

95 97

103 105

98

98

91

98 93

95

98

90

92

96

99 106 100

98

109

91

100

90

99

95

94

98

99

104

102

95

104

98

92

92

99

102

101 104

98

96

93

92

H HH HH

H

H

H H

H

HH

H H

H H H H H

H

H

H

H H

H

H

H

H

H

H

H

H

H

H

H

H H H

H

H

H

H

121

115

120

115

H

H

H

H

Kahuku Point

Makapuu

Point

Diamond Head

Barbers

Point

Kaena

Point

Waimanalo

Bay

KANEOHE

BAY

MAMALA BAY

Pearl 

 Harbor

Waikiki

158o10'

157o50'

157o40'

21o40'

21o30'

21o20'

158o

1920-29

85

83

87

89

90

87

77

H

H

H

H

H

H

H

97

108

103

97

98

94

97

102

105

110

105

99

95

90

96 97

93

99 99

107

105

H HH H

H

H

H

H

H

H H

H

H

H

H H

H

H H

H

H

121

113

110

125 141 110

110

H H H HH H

H

Kahuku Point

Makapuu

Point

Diamond Head

Barbers

Point

Kaena

Point

Waimanalo

Bay

KANEOHE

BAY

MAMALA BAY

Pearl 

 Harbor

Waikiki

158o10'

157o50'

157o40'

21o40'

21o30'

21o20'

158o

00

4 MILES 2

2 4 KILOMETERS

Topographic divide

Topographic divide

1910-19

Figure 14. Ratios of mean annual rainfall during selected periods to long-term (1916-83) mean annual rainfall (Giambelluca and others, 1986), Oahu, Hawaii.

Ground-Water Flow System  27
Base modified from U.S. Geological Survey National

Hydrography Dataset, Albers equal area projection, standard parallels 21o19'40" and 21o38'20", central meridian 157o58', datum NAD83. 

HHH

EXPLANATION

RATIOS OF AVERAGE RAINFALL DURING INDICATED PERIOD TO LONG-TERM (1916-1983) MEAN ANNUAL RAINFALL, IN PERCENT, ATSELECTED RAIN GAGES (VALUES INDICATED NEXT TO SYMBOL) LESS THAN 90 PERCENT GREATER THAN OR EQUAL TO 90  PERCENT AND LESS THAN OR  EQUAL TO 110 PERCENT  GREATER THAN 110 PERCENT

78

81

88

90 86

84

88

90 89

87

84

83

89

82

76

82

78

86

84 83

87

84

88

83 83

78

84

88

84

80

75

85

89

84

84

82 85

75

81

76

85 86

89

87

85

86 85 84 83

88

87

71

85

79 86

81

90

89

7677

87

H H

H

H H

H

H

H H

H

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 Harbor

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Point

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Pearl 

 Harbor

Waikiki

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1970-74

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Bay

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BAY

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Pearl 

 Harbor

Waikiki

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1960-69

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Makapuu

Point

Diamond Head

Barbers

Point

Kaena

Point

Waimanalo

Bay

KANEOHE

BAY

MAMALA BAY

Pearl 

 Harbor

Waikiki

158o10'

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158o

Topographic divide

Topographic divide

1950-59

00

4 MILES 2

2 4 KILOMETERS

Figure 14. Ratios of mean annual rainfall during selected periods to long-term (1916-83) mean annual rainfall (Giambelluca and others, 1986), Oahu, Hawaii—Continued.

28  Numerical Simulation of the Effects of Valley-Fill Barriers in the Pearl Harbor Area, Oahu, Hawaii
Base modified from U.S. Geological Survey National

Hydrography Dataset, Albers equal area projection, standard parallels 21o19'40" and 21o38'20", central meridian 157o58', datum NAD83. 

HHH

EXPLANATION

RATIOS OF AVERAGE RAINFALL DURING INDICATED PERIOD TO LONG-TERM (1916-1983) MEAN ANNUAL RAINFALL, IN PERCENT, ATSELECTED RAIN GAGES (VALUES INDICATED NEXT TO SYMBOL) LESS THAN 90 PERCENT GREATER THAN OR EQUAL TO 90  PERCENT AND LESS THAN OR  EQUAL TO 110 PERCENT  GREATER THAN 110 PERCENT

67

72

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79

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118

H

Kahuku Point

Makapuu

Point

Diamond Head

Barbers

Point

Kaena

Point

Waimanalo

Bay

KANEOHE

BAY

MAMALA BAY

Pearl 

 Harbor

Waikiki

158o10'

157o50'

157o40'

21o40'

21o30'

21o20'

158o

1995-2000

77

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69

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Point

Diamond Head

Barbers

Point

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Point

Waimanalo

Bay

KANEOHE

BAY

MAMALA BAY

Pearl 

 Harbor

Waikiki

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157o50'

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158o

1990-94

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Point

Waimanalo

Bay

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BAY

MAMALA BAY

Pearl 

 Harbor

Waikiki

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1985-89

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Makapuu

Point

Diamond Head

Barbers

Point

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Point

Waimanalo

Bay

KANEOHE

BAY

MAMALA BAY

Pearl 

 Harbor

Waikiki

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158o

Topographic

divide

Topographic

divide

1980-84

00

4 MILES 2

2 4 KILOMETERS

Figure 14. Ratios of mean annual rainfall during selected periods to long-term (1916-83) mean annual rainfall (Giambelluca and others, 1986), Oahu, Hawaii—Continued.

Ground-Water Flow System  29
1880 1900 1920 1940 1960 1980 2000

0

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ANNUAL MEAN PUMPAGE, IN MILLION GALLONS PER DAY 

Ewa-Kunia management system 

Sustainable-yield estimate 

Waipahu-Waiawa management system 

Waimalu management system 

Moanalua management system 

Pearl Harbor area caprock 

Pearl Harbor area volcanic rocks (Ewa-Kunia, Waipahu-Waiawa, and Waimalu aquifer-management systems) 

Figure 15. Ground-water withdrawals from the Pearl Harbor and Moanalua areas, Oahu, Hawaii. Sustainable-yield 

values (as of 2005) are from the Hawaii Commission on Water Resource Management. 

30 Numerical Simulation of the Effects of Valley-Fill Barriers in the Pearl Harbor Area, Oahu, Hawaii
Schuyler and Allardt (1889) described the first known 

measurements of discharge from the Pearl Harbor springs 

and reported that discharge measured at seven locations 

totaled about 75 Mgal/d. These first known measurements of 

discharge from the springs represent a lower bound for the 

total discharge at the time because only the unused flow was 

measured. 

In 1911, miscellaneous measurements of springs at 11 

locations near Pearl Harbor were made by the USGS (Martin 

and Pierce, 1913). The total measured spring discharge was 

about 48 Mgal/d, which is not representative of the total flow 

because not all known springs were measured. 

In 1927, the Honolulu Board of Water Supply initiated 

a program of measuring the discharge from the five major 

spring sites (Kunesh, 1929, 1931). Measured annual mean 

discharge from the Pearl Harbor springs was about 64, 61, and 

74 Mgal/d during 1928, 1929, and 1930, respectively. However, reported discharge from Waikele and Waimano springs 

during 1928 to 1930 (Kunesh, 1931) underestimated the total 

discharge at these sites (Oki, 1998). 

Starting in 1931, the USGS began establishing gaging stations to measure flow from the Pearl Harbor springs. 

Annual mean discharge from the springs was about 85 and 82 

Mgal/d during 1932 and 1933 (Stearns and Vaksvik, 1935), 

respectively, but these values include estimated discharge from 

Waikele springs based on the incomplete measurements from 

Kunesh (1931). 

During 1931 to 1967, the USGS maintained gaging 

stations to measure discharge from the Pearl Harbor springs. 

Since 1967, the USGS has made semiannual discharge 

measurements at 20 to 24 sites near Pearl Harbor to monitor 

discharge from the springs (see for example Taogoshi and others, 2001). 

Discharge from the Pearl Harbor springs is directly 

dependent on the head in the aquifer; discharge is high when 

head in the aquifer is high, and discharge is low when head in 

the aquifer is low. Soroos and Ewart (1979) indicated that a 

linear relation exists between head (as measured by the water 

level in a monitor well) and total spring discharge. Oki (1998) 

used available data to develop linear-regression equations for 

each of the major spring areas relating discharge and groundwater level (table 2). These relations were developed for conditions when water levels at well 2256-10 were between about 

13 and 24 ft for Kalauao, Waiau, and Waimano springs, and 

between about 13 and 20 ft for Waiawa and Waikele springs.

Water Levels

Ground-water flow directions commonly are inferred 

from ground-water levels measured in wells. Ground-water 

levels also are an indicator of changes in recharge or withdrawals from the ground-water system, and can be an indicator 

of freshwater-lens thickness. In the Pearl Harbor area, groundwater levels vary spatially (both horizontally and vertically) 

and temporally. 

In general, measured water levels in the Pearl Harbor 

area are lowest near the Pearl Harbor springs at the inland 

edge of the caprock. Water levels increase inland toward 

the recharge areas of the Koolau Range and the Schofield 

ground-water area (Visher and Mink, 1964; Dale and Ewart, 

1971; Soroos and Ewart, 1979). On October 31, 2002 and 

May 15, 2003, ground-water-level surveys were made in the 

Pearl Harbor area. Agencies participating included the USGS, 

BWS, CWRM, U.S. Air Force (through their consultant, URS 

Corporation), and U.S. Navy (U.S. Geological Survey, 2003). 

Water levels measured on October 31, 2002 ranged from 13.6 

to 20.4 ft above mean sea level. Water levels measured on May 

15, 2003 ranged from 13.1 to 19.7 ft above mean sea level. In 

general, measured water levels were lowest near the southeastern and southwestern parts of the Pearl Harbor area and 

were highest in the inland, northern part of the area (fig. 16). 

Water levels in the Waianae Volcanics (west of the Waianae 

confining unit) generally are lower than water levels in Koolau 

Basalt because recharge to the Waianae Volcanics is relatively 

low. 

The magnitude of the horizontal hydraulic gradient varies 

spatially and generally is on the order of 0.0002 ft/ft (about 1 

ft/mi). Near areas of converging flow, such as near the Pearl 

Harbor springs, the horizontal hydraulic gradient may exceed 

0.0002 ft/ft. 

Table 2. Relations between discharge at the Pearl Harbor springs and water level measured at well 2256-10, 

Oahu, Hawaii (Oki, 1998).

Spring Relation1 Coefficient of determination, r2

Waikele Discharge = 1.6108h – 12.5595 0.59

Waiawa Discharge = 1.4882h – 7.8089 0.81

Waimano-Waiau Discharge = 2.4572h – 19.0360 0.96

Kalauao Discharge = 1.2726h – 7.5966 0.79

1

Discharge is in million gallons per day; h is the water level, in feet above mean sea level, at well 2256-10.

Ground-Water Flow System  31
Waianae Confining Unit

Waianae Confining Unit

0

0

2 4 MILES

2 4 KILOMETERS

158o10' 158o00' 157o50'

21o30'

21o20'

0

0

2 4 MILES

2 4 KILOMETERS

158o10' 158o00' 157o50'

21o30'

21o20'

Topographic Divide

Topographic Divide

Kalihi

Str

Moanalua Str

N Halawa Str

Waimano Str

Kipapa

Str

Mailiilii Str

Waiawa Str

S Halawa Str

Waihee Str

Nuuanu Str

Waimalu Str

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Str

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Str

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Str

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Str

Barbers

Point MAMALA BAY

Pearl 

 Harbor

Base modified from U.S. Geological Survey National

Hydrography Dataset, Albers equal area projection, 

standard parallels 21o19'40" and 21o38'20", central 

meridian 157o58', datum NAD83. Relief from U.S. 

Geological Survey digital elevation models, 1:24,000

Barbers

Point MAMALA BAY

Pearl 

 Harbor

Base modified from U.S. Geological Survey National

Hydrography Dataset, Albers equal area projection, 

standard parallels 21o19'40" and 21o38'20", central 

meridian 157o58', datum NAD83. Relief from U.S. 

Geological Survey digital elevation models, 1:24,000

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U.S. Geological Survey

Honolulu Board of Water Supply

U.S. Air Force (through URS Corp.)

U.S. Navy H

H

water level next to well symbol

is in feet above mean sea level

(rounded to nearest tenth of a foot)

MEASURING AGENCY

H

H

Pearl Harbor area ground-water levels

October 31, 2002 (9:00 a.m. to 11:30 a.m.)

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U.S. Geological Survey

Honolulu Board of Water Supply

Hawaii Commission on Water 

 Resource Management

H

water level next to well symbol

is in feet above mean sea level

(rounded to nearest tenth of a foot)

MEASURING AGENCY

H

H

Pearl Harbor area ground-water levels

May 15, 2003 (9:00 a.m. to 11:30 a.m.)

Pacific

Ocean

Area of

Map

Oahu

Pacific

Ocean

Area of

Map

Oahu

Boundary of Pearl Harbor area

Boundary of Pearl Harbor area

Figure 16. Water-level surveys of October 31, 2002 and May 15, 2003, Pearl Harbor area, Oahu, Hawaii.

32  Numerical Simulation of the Effects of Valley-Fill Barriers in the Pearl Harbor Area, Oahu, Hawaii
Near inland recharge areas, heads in the aquifer may 

decrease with depth, whereas near coastal discharge areas 

heads in the aquifer may increase with depth. Although limited 

information is available to quantify the magnitude of the vertical hydraulic gradient in the Pearl Harbor area, information 

from a pair of wells near a discharge area in northern Oahu 

indicates that the vertical hydraulic gradient near the wells is 

about 0.001 ft/ft (Oki, 1998). 

The first successful artesian well drilled on Oahu was 

in the Pearl Harbor area and was completed in 1879. The 

well (2101-04) was drilled near the southwestern part of the 

Pearl Harbor area near West Loch. Thrum (1889) reported 

the original head in the southwestern part of the Pearl Harbor 

area to be 32 ft above mean sea level, although it is unclear 

whether this head is representative of an average head during 

predevelopment times or whether it reflects a particular wet 

or dry period. Assuming a hydraulic gradient of 0.0002 ft/ft 

and a head of 32 ft near Pearl Harbor, Mink (1980) estimated 

an inland predevelopment water level of 39 ft above mean sea 

level near the boundary between the Pearl Harbor and Schofield ground-water areas. 

The history of water-level decline in wells in the Pearl 

Harbor area is well documented (see for example Soroos 

and Ewart, 1979). Water levels measured in wells in the area 

indicate seasonal variations and a long-term downward trend 

(fig. 17). Historically, water levels were strongly affected by 

the seasonal pattern of ground-water withdrawals by sugarcane 

plantations. This effect is evident at well 2101-03, which is 

near several high-capacity agricultural wells. Measured water 

levels in well 2101-03 varied by 5 ft between dry and wet seasons when sugarcane was being cultivated. Soroos and Ewart 

(1979) used a linear-regression analysis to estimate a 0.09 

ft/yr rate of water-level decline in the Pearl Harbor area during 

1910-77. The water-level decline was caused by the increased 

ground-water withdrawals from the aquifer over time, and 

also may reflect a downward trend in rainfall over time (Oki, 

2005). 

Salinity

Salinity is one of the main factors controlling groundwater availability in the Pearl Harbor area. In general, the 

salinity of water withdrawn from wells in the area is expected 

to increase with depth, proximity to the coast, and withdrawal 

rate, although exceptions to this generalization are known 

to exist. Many of the older, high-capacity irrigation wells 

drilled by sugarcane plantations produced water with a salinity 

exceeding 5 percent that of ocean water. Saltwater intrusion is 

a problem at these wells because of the great depth to which 

the wells were drilled and the high withdrawal rates. At some 

well fields, salinity of pumped water was reduced by backfilling the deeper wells (Stearns and Vaksvik, 1935). 

To better understand conditions in the freshwaterlens systems on Oahu, the BWS established a program of 

monitoring the salinity profiles in deep open boreholes that 

fully penetrate the freshwater lens. Salinity profiles generally are measured in terms of fluid conductivity. For this 

study, ocean water was assumed to have a fluid conductivity of 50,000 microsiemens per centimeter, which is near 

the maximum value measured in deep boreholes. Measured 

fluid-conductivity values were divided by 50,000 microsiemens per centimeter to obtain salinity in terms of percent of 

ocean-water salinity. 

Measured salinity profiles provide an indication of the 

volume of freshwater in the aquifer. Collection of salinity profiles over time provides an indication of the changes 

in freshwater volume. In the Pearl Harbor area, numerous 

deep wells have been drilled for the purpose of monitoring 

salinity profiles. Although many of these wells were drilled 

within the past several years, a few deep monitor wells were 

drilled more than 15 years ago. In general, salinity profiles 

collected from the older deep monitor wells indicate a rise of 

the top of the brackish-water transition zone and a reduction 

of freshwater thickness over time (fig. 18). Decreased salinity over time measured in some wells (compare profiles from 

1990 and 2001 for well 2457-04 in fig. 18) may be related to 

reduced withdrawals, logging-equipment changes, or changing 

borehole-flow conditions. 

Salinity profiles from deep open boreholes may be 

affected by flow within the borehole (Paillet and others, 2002). 

Borehole flow can be caused by both natural and withdrawalinduced vertical-head differences in the aquifer. Head may 

increase with depth in the aquifer near coastal discharge areas 

and near partially penetrating pumped wells, and increasing 

head in the aquifer with depth may lead to upward flow within 

an open borehole. Upward borehole flow may cause saltwater 

to flow upward in the borehole, which in turn may lead to 

an underestimate of the freshwater-lens thickness based on 

the recorded salinity profile. In areas where head decreases 

with depth, downward borehole flow may occur and lead to 

an overestimate of the freshwater-lens thickness based on the 

recorded salinity profile. 

Temperature

Ground-water temperatures in the Pearl Harbor area generally range from about 19 to 25 degrees Celsius and are highest near the top and bottom of measured temperature profiles. 

Water temperatures at the top of the freshwater lens generally 

are slightly warmer than temperatures in the underlying freshwater because of local recharge from irrigation-return flow. 

Beneath the warm upper zone, water temperatures in the main 

part of the freshwater body are cooler because recharge originates from cooler high altitudes. Beneath the main freshwater 

body, water warms with depth because of the natural geothermal gradient.

Ground-Water Flow System  33
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Figure 17. Measured water levels in selected wells in the Pearl Harbor area, Oahu, Hawaii.

34  Numerical Simulation of the Effects of Valley-Fill Barriers in the Pearl Harbor Area, Oahu, Hawaii
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Figure 18. Measured salinity profiles in selected wells in the Pearl Harbor area, Oahu, Hawaii. (Salinity profiles from Honolulu Board of Water Supply.)

Ground-Water Flow System  35
Simulation of Ground-Water Flow

Several numerical models have been developed to 

simulate ground-water flow in the Pearl Harbor area. These 

models include two-dimensional areal models that treat the 

interface between freshwater and saltwater as a sharp interface (Liu and others, 1981; Essaid, 1990; Nichols and others, 

1996; Oki, 1998), two-dimensional cross-section models that 

simulate the brackish-water transition zone (Souza and Voss, 

1987), and most recently, a three-dimensional model capable 

of simulating the brackish-water transition zone (Gingerich 

and Voss, 2005). The model developed for this study also is a 

three-dimensional model capable of simulating the brackishwater transition zone and incorporates hydrogeologic features 

(valley-fill barriers, an upper-limestone unit in the caprock, 

onshore discharge at the Pearl Harbor springs, and a weathered 

surface separating Waianae Volcanics and Koolau Basalt) that 

were not represented in the model developed by Gingerich and 

Voss (2005).

The model code used for this study was SUTRA (version 2D3D.1) (Voss and Provost, 2003), modified to account 

for water-table storage (Gingerich and Voss, 2005) through 

the specific yield of the aquifer. SUTRA is a finite-element 

code that simulates fluid movement and the transport of dissolved substances in a ground-water system. SUTRA (version 

2D3D.1) is capable of simulating three-dimensional, variabledensity ground-water flow and solute transport in heterogeneous anisotropic aquifers. Model construction was facilitated 

using a graphical user interface (SutraGUI) (Winston and 

Voss, 2003) capable of reading geographic information system 

(GIS) spatial data. 

Construction of the Model

The numerical model of ground-water flow and transport 

in the Pearl Harbor area was developed to simulate groundwater levels and brackish-water transition-zone movement 

within the freshwater-lens system during the period 1880 

through 2000, and incorporated time-varying recharge and 

withdrawals. Hydraulic characteristics used to construct the 

model were based mainly on previous estimates (R.M. Towill 

Corporation, 1978; Souza and Voss, 1987; Oki and others, 

1998; Oki, 1998). In some cases, hydraulic-characteristic 

values were varied in the model to obtain better agreement 

between simulated and measured water levels and measured 

salinity profiles. Transient simulations of the Pearl Harbor area 

from 1880 through 2000 were initiated with the hydrologic 

system in a steady-state, predevelopment condition. 

Model Mesh

The model mesh used for this study consists of 306,432 

nodes and 292,875 elements, covers the entire freshwaterlens system in the Pearl Harbor area as well as the Moanalua 

ground-water area to the east, and extends several miles offshore to include the zone where fresh ground water discharges 

to the ocean (fig. 19). The model mesh excludes dike-intruded 

areas between the margins of the rift zones and the topographic crests of the Koolau and Waianae Ranges, although 

recharge within these excluded areas is included in the model 

and is assumed to contribute to the freshwater-lens system. 

The modeled domain extends to 5,906 ft below mean sea 

level to coincide with an assumed aquifer bottom (Souza and 

Voss, 1987) and a seismic velocity discontinuity (Furumoto 

and others, 1970). Node spacing is variable in both the vertical 

and horizontal directions and is finest in the upper part of the 

aquifer and near areas of ground-water discharge. Onshore, 

the vertical spacing between nodes varies from 33 ft within the 

top 1,969 ft of the aquifer to 492 ft within the bottom 2,953 ft 

of the modeled domain; offshore, the vertical spacing between 

nodes is dependent on the bathymetry within the top 1,969 ft 

of the aquifer, but is the same as the onshore spacing within 

the bottom 3,937 ft of the modeled domain (fig. 20). 

Boundary Conditions

The lateral extent of the model domain is defined by 

vertical boundaries that are either no-flow, recharge, or 

specified-pressure boundaries. The southeastern boundary is 

formed by the valley-fill barrier associated with Kalihi Stream 

valley and is treated as a no-flow boundary in the model. The 

western, northern, and northeastern boundaries are formed, 

respectively, by the southern rift zone of the Waianae Volcano, 

the southern Schofield ground-water dam, and the northwest 

rift zone of the Koolau Volcano. Recharge from upgradient 

areas is allowed to enter the western, northern, and northeastern boundaries between altitudes of -3 ft and -984 ft (fig. 19). 

Below altitudes of -984 ft, the western, northern, and northeastern boundaries are no-flow boundaries. 

The offshore, vertical southern boundary of the model 

domain is a specified-pressure (hydrostatic ocean-water) 

boundary condition. Pressure at each node along the offshore 

vertical southern boundary is equal to the pressure of a column 

of ocean water extending from the node to sea level. Water 

may either enter or exit the flow system across the vertical 

southern boundary of the model. Water entering at the vertical 

southern boundary has salinity equal to that of ocean water, 

and water exiting at the southern boundary has salinity equal 

to that in the adjacent aquifer. 

The top of the offshore model domain is defined 

by the ocean-bottom bathymetry (U.S. Army Corps of 

Engineers, 2000; U.S. Geological Survey, 2002) and is a 

specified-pressure (hydrostatic ocean-water) boundary condition. Ocean water may enter the model domain at the top 

boundary in offshore areas or water from the aquifer may exit 

at the top boundary in offshore areas. 

The top of the onshore model domain is assumed to be at 

sea level. Although the top water-table boundary in onshore 

areas is truncated at sea level, the overall aquifer transmissivity 

is underestimated by less than 1 percent by this assumption. 

The bottom of the model is assumed to be a no-flow boundary.

36  Numerical Simulation of the Effects of Valley-Fill Barriers in the Pearl Harbor Area, Oahu, Hawaii
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VOLCANIC-ROCK AQUIFER (UNCONFINED)COASTAL CONFINING UNIT (CAPROCK) OVERLYING VOLCANIC-ROCK AQUIFERVALLEY-FILL BARRIER INLAND FROM CAPROCKVALLEY-FILL BARRIER BENEATH CAPROCKWAIANAE CONFINING UNIT INLAND FROM CAPROCKWAIANAE CONFINING UNIT BENEATH CAPROCKSEAWARD BOUNDARY BENEATH CAPROCKARTIFICIAL HIGH-DISPERSIVITY ZONE IN MODEL (ONLY FOR TOP TWO ELEMENTS OF MODEL)PEARL-HARBOR SPRING NODESPECIFIED-PRESSURE BOUNDARY NODE AT TOP BOUNDARY ONLY ALONG VERTICAL (TOP TO BOTTOM BOUNDARIES)RECHARGE BOUNDARY NODE (-3 TO -984 FEET) WAIANAE RIFT ZONE WESTERN SCHOFIELD EASTERN SCHOFIELD KOOLAU RIFT ZONE, NORTH KOOLAU RIFT ZONE, SOUTH

HHHHH

EXPLANATION

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Pearl 

 Harbor

Base modified from U.S. Geological Survey NationalHydrography Dataset, Albers equal area projection, standard parallels 21o19'40" and 21o38'20", central meridian 157o58', datum NAD83. Relief from U.S. Geological Survey digital elevation models, 1:24,000

Figure 19. Model boundary conditions and other features for the vertically aligned mesh, Pearl Harbor area, Oahu, Hawaii. A hydrostatic seawater boundary condition is used for the uppermost offshore nodes and all nodes along the southern vertical boundary of the mesh. 

Simulation of Ground-Water Flow  37
vertical exaggeration x 10 

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ALTITUDE, IN FEET RELATIVE TO MEAN SEA LEVEL 

COAST 

Offshore bathymetry

Inland direction 

Figure 20. Vertical cross section (western edge) of model mesh for the Pearl Harbor area, viewed from west to east.

38  Numerical Simulation of the Effects of Valley-Fill Barriers in the Pearl Harbor Area, Oahu, Hawaii
Initial Conditions

Initial conditions for the transient simulation from 1880 

through 2000 were estimated from a steady-state simulation 

using predevelopment recharge (Shade and Nichols, 1996) and 

zero withdrawals. Predevelopment recharge of 307 Mgal/d 

was used in the model. Simulated predevelopment discharge 

from the Pearl Harbor springs was about 137 Mgal/d. 

Representation of Hydrogeologic Features

Several hydrogeologic features of low permeability 

relative to the main aquifer were represented in the model. 

Valley-fill barriers associated with Kipapa, Waiawa, Waimalu, 

and North Halawa Stream valleys were represented as partially 

penetrating, vertical, low-permeability zones. The depth of 

penetration of the valley-fill barriers is uncertain because of 

a paucity of available information. Depths of the valley-fill 

barriers were estimated at selected locations and interpolated 

or extrapolated at other sites. The valley-fill barrier depths 

described in this section represent the base-case valley-fill barriers in the model. 

On the basis of available information from well 2401-

01, weathered volcanic rocks may extend about 100 ft below 

mean sea level in Waikele Stream valley, about 600 ft downstream from the confluence of Waikele and Kipapa Streams 

at a channel altitude of about 100 ft (Eyre, 1983). Data are 

unavailable to define the bottom of the Kipapa valley-fill 

barrier seaward or inland of well 2401-01. For the model, the 

Kipapa valley-fill barrier was extended seaward of well 2401-

01, using a bottom altitude of -100 ft to where the contact 

between the caprock and volcanic rocks also is 100 ft below 

mean sea level. The bottom of the Kipapa valley-fill barrier 

was extended inland, with an estimated slope of 3 percent, to 

where the bottom of the barrier was at sea level.

On the basis of available well logs, the bottom of the 

Waiawa valley-fill barrier was estimated to extend to 65 ft 

below mean sea level near the shore of Middle Loch of Pearl 

Harbor (fig. 21). At a channel altitude of 200 ft, the alluvium 

was estimated to be 65 ft thick, extending to an altitude of 135 

ft, and underlain by 200 ft of weathered basalt (R.M. Towill 

Corporation, 1978). Thus, the bottom of the Waiawa valleyfill barrier was estimated to be at an altitude of -65 ft where 

the channel altitude is 200 ft (fig. 21). Inland from where the 

channel altitude is 200 ft and between channel altitudes of 100 

and 200 ft, the bottom of the Waiawa valley-fill barrier was 

assumed to have a slope of 3 percent. The Waiawa valley-fill 

barrier was extended inland to where the bottom of the barrier 

was at sea level.

On the basis of available well logs, the bottom of the 

Waimalu valley-fill barrier was estimated to extend to about 

330, 260, and 200 ft below mean sea level near wells 2357-

19, 2357-20, and 2356-34, respectively (fig. 22). Seaward of 

well 2357-19, the bottom of the Waimalu valley-fill barrier 

was assumed to be 330 ft below mean sea level to where the 

contact between the caprock and volcanic rocks also is 330 ft 

below mean sea level. Inland of well 2356-34, the bottom of 

the Waimalu valley-fill barrier was extrapolated using a slope 

of 3 percent to where the bottom of the barrier was at sea level.

Izuka (1992) estimated the bottom of the alluvium filling 

Halawa Stream valley to be near sea level at a channel altitude 

of about 150 ft. Weathered basalt was assumed to extend 200 

ft beneath the alluvium. Thus, the bottom of the North Halawa 

valley-fill barrier was estimated to be at an altitude of -200 

ft where the channel altitude is 150 ft. Seaward of where the 

channel altitude is 150 ft, the bottom of the North Halawa 

valley-fill barrier was assumed to be 200 ft below mean sea 

level to where the contact between caprock and volcanic rocks 

also is 200 ft below mean sea level. Inland of where the channel altitude is 150 ft, the North Halawa valley-fill barrier was 

extrapolated using a slope of 3 percent to where the bottom of 

the barrier was at sea level.

In the model, the volcanic-rock aquifer is unconfined in 

areas that are not beneath valley-fill barriers or the coastal confining unit (caprock). The caprock was represented as a seaward-thickening wedge with geometry defined by published 

structural contours (Palmer, 1946; Wentworth, 1951; Visher 

and Mink, 1964; Gregory, 1980) that were modified using 

additional logs from more recently drilled wells (fig. 7). A 

high-permeability upper-limestone unit within the low-permeability caprock was defined on the basis of existing structural 

contours (Camp Dresser and McKee, 1994) that were extrapolated offshore and to the east. 

Although the Waianae confining unit separating Waianae 

Volcanics from Koolau Basalt follows the weathered, dipping 

surface of the Waianae Volcano, this confining unit was represented as a partially penetrating, vertical, low-permeability 

zone in the model, extending down to an altitude of -2,953 ft. 

The representation of the Waianae confining unit in the model 

is simplified because of uncertainties in the geometry and barrier effectiveness at depth. 

Recharge

Recharge enters the model at the top, water-table boundary in onshore areas and along parts of the western, northern, 

and northeastern boundaries. Recharge from the western, 

northern, and northeastern boundaries enters the model 

between altitudes of -3 ft and -984 ft relative to mean sea level. 

Recharge was estimated as a function of rainfall and land 

use (table 1). For predevelopment conditions, a piecewise linear model relating annual rainfall and annual recharge (Shade 

and Nichols, 1996) along with the distribution of long-term 

average annual rainfall (Giambelluca and others, 1986) was 

used to estimate the spatial distribution of average recharge 

over the modeled area. Recharge in the non-modeled, dikeintruded areas between the model boundaries and the crests of 

the Koolau and Waianae Ranges was estimated using values 

from Shade and Nichols (1996). Recharge entering the northern model boundary through the southern Schofield groundwater dam was estimated to be 106 Mgal/d (Oki, 1998; Shade 

Simulation of Ground-Water Flow  39
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Figure 21. Profile of Waiawa Stream channel and estimated bottom of valley-fill barrier, Pearl Harbor area, Oahu, Hawaii.

40 Numerical Simulation of the Effects of Valley-Fill Barriers in the Pearl Harbor Area, Oahu, Hawaii
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Figure 22. Profile of Waimalu Stream channel and estimated bottom of valley-fill barrier, Pearl Harbor area, Oahu, Hawaii.

Simulation of Ground-Water Flow  41
and Nichols, 1996). Estimated total predevelopment recharge 

in the modeled area was 307 Mgal/d (table 3).

The distributions of recharge for individual 5- to 20-year 

periods from 1880 through 2000 were estimated using the 

distributions of land use (fig. 3) and rainfall (fig. 14) during 

each period in conjunction with equations relating annual 

rainfall and annual recharge for different land uses (Shade and 

Nichols, 1996). Annual rainfall during a particular period was 

estimated from the long-term annual rainfall (fig. 2) (Giambelluca and others, 1986) multiplied by the ratio of annual rainfall 

during the period to the long-term annual rainfall. For each 

model node, ratios of annual rainfall during selected periods to 

the long-term annual rainfall (fig. 14) were determined using 

the ratio from the nearest rain gage with a computed ratio for 

the period. Land use at each node was assumed to be representative of the land use for the immediate area surrounding the 

node. 

For furrow-irrigated sugarcane areas, recharge was 

estimated by adding a fraction of the applied irrigation water 

(table 4) to the estimated non-agricultural recharge rate. For 

this study, it was assumed that 30 percent of the applied irrigation water in furrow-irrigated sugarcane fields contributed to 

recharge, which is lower than some previous estimates but 

consistent with the estimate from Nichols and others (1996).

For each selected time period, recharge entering the 

model domain from the western, northern, and northeastern 

boundaries was determined by multiplying the predevelopment recharge value by an average ratio (determined from 

nearby rain gages with available data) of annual rainfall during 

the period to the long-term annual rainfall. Estimated recharge 

in the modeled area for individual 5- to 20-year periods during 1880 through 2000 ranged from 261 Mgal/d (1995-2000) 

to 424 Mgal/d (1930-1939) (table 3). Estimated recharge is 

greatest near high-rainfall areas, although irrigation associated 

with sugarcane cultivation and evapotranspiration suppression associated with pineapple cultivation locally modify this 

general recharge distribution.

Withdrawal

Reported or estimated monthly withdrawals from wells 

during 1890 through 2000 were simulated in the numerical 

model (Appendix A). Reported withdrawals were compiled 

from published records (Stearns and Vaksvik, 1935; Stearns, 

1940), information contained in U.S. Geological Survey files 

(unpub. data, USGS Pacific Islands Water Science Center data 

files), and a CWRM digital database (unpub. data, 2002). The 

small amount of estimated withdrawal prior to 1890 (Mink, 

1980) was not simulated in the transient model, which has 

little effect on the long-term transient response of the system. 

Withdrawal wells (fig. 23) were represented in the model 

by the nearest vertical column of nodes to the withdrawal well. 

Within the nearest vertical column of nodes from a pumped 

well, only those nodes corresponding to the interval of the 

well open to the aquifer (appendix B) were used to simulate 

withdrawal. Withdrawal from the aquifer was assumed to 

be uniform within the interval of the well open to the aquifer. Withdrawals from Maui-type shafts with large-capacity 

infiltration tunnels generally were represented in the model by 

a single node, although some infiltration tunnels were represented by more than one node to improve model stability. In 

the model, withdrawals were not simulated from the top layer 

of nodes to avoid assigning both recharge and pumpage at the 

same node in SutraGUI (Winston and Voss, 2003). 

Discharge from the Pearl Harbor springs was simulated in 

the model from selected nodes at the top of the model domain 

(fig. 19). Recharge from nodes used to represent the Pearl Harbor springs was set to zero. Discharge from the Pearl Harbor 

springs was simulated as a function of the simulated head at 

well 2256-10 according to relations from Oki (1998) (table 2). 

Because of the lack of information on discharge from the Pearl 

Harbor springs during the entire period from 1880 through 

2000, it was necessary to apply the relations in table 2 beyond 

the range of water levels used to develop the relations. 

Water Properties

For all model simulations, water was assigned a fluid 

compressibility of 2.14 × 10–8 ft2/lb (4.47 × 10–10 Pa–1) and 

dynamic viscosity of 2.1 × 10–5 slug/(ft•s) [0.001kg/(m•s)]. 

Viscosity is a property of a fluid that measures its resistance 

to deformation (flow). Dynamic viscosity is the ratio of shear 

stress (shear force per unit area) to velocity gradient. 

Solute concentrations in the model are expressed as a 

mass fraction: mass of total dissolved solids (TDS) per unit 

mass of fluid. Freshest water was assigned a TDS concentration of zero and 100 percent saltwater was assigned a TDS 

concentration of 0.0357 kg/kg. The density of water was 

assumed to increase linearly with salinity from 62.42 lb/ft3

(1,000 kg/m3) for freshwater to 63.98 lb/ft3 (1,024.99 kg/m3) 

for saltwater. 

Molecular diffusion of a solute is driven by concentration gradients in the fluid and may take place in the absence of 

ground-water flow. Molecular diffusion of a solute in a fluid 

is characterized by the molecular diffusivity. In the model, 

molecular diffusivity was assigned a value of 1.1 × 10–8 ft2/s 

(1.0 × 10–9 m2/s). 

Aquifer Properties

For this study, aquifer properties generally were assigned 

values based on published estimates. Solid-matrix compressibility was assigned a value of 1.2 × 10–7 ft2

/lb (2.5 × 10–9

Pa–1) (Souza and Voss, 1987). For the volcanic-rock aquifers, 

effective porosity values used in the model were 0.04 (east 

of Waiawa Stream) and 0.1 (west of Waiawa Stream). The 

effective porosity values used in the model are within the 

range of previously estimated values (Mink, 1980; Souza and 

Voss, 1987) and are lower in the east than west to improve the 

match between measured and simulated salinity profiles. For 

the upper-limestone unit, effective porosity was assigned a 

42  Numerical Simulation of the Effects of Valley-Fill Barriers in the Pearl Harbor Area, Oahu, Hawaii
Table 3. Estimated ground-water recharge used in construction of the numerical model of the Pearl Harbor area, Oahu, Hawaii during selected periods.

[Mgal/d, million gallons per day]

Period

Recharge, in Mgal/d

Pumpage, in 

Mgal/d Top boundary1 Waianae rift zone2 Western Schofield2 Eastern Schofield2 Koolau rift zone2, north Koolau rift zone2, south Total

Predevelopment 175 1.9 0.6 106 23 0.8 307 01880-1889 175 1.9 0.6 106 23 0.8 307 01890-1899 175 1.9 0.6 106 23 0.8 307 291900-1909 229 1.9 0.6 106 23 0.8 361 1391910-1919 258 1.8 0.6 115 23 0.8 390 1561920-1929 256 1.9 0.6 104 23 0.8 386 1601930-1939 282 2.0 0.6 113 26 0.8 424 1561940-1949 224 1.6 0.5 97 21 0.6 345 1761950-1959 245 2.0 0.6 109 21 0.7 378 1601960-1969 267 2.2 0.7 113 24 0.9 407 1841970-1974 232 2.1 0.7 112 21 0.8 368 2201975-1979 183 1.7 0.5 97 19 0.7 302 2291980-1984 194 1.9 0.6 106 23 0.9 326 1891985-1989 202 1.9 0.6 99 23 1.0 327 1521990-1994 187 1.9 0.6 103 22 0.9 316 1521995-2000 142 1.8 0.6 98 18 0.9 261 105

1Includes recharge over the volcanic-rock aquifer, coastal caprock, valley-fill barriers, and Waianae confining unit.2Recharge boundary shown in figure 19.

Simulation of Ground-Water Flow  43
Table 4. Estimated areas and irrigation rates for furrow-irrigated sugarcane 

fields in the Pearl Harbor area, Oahu, Hawaii during selected time periods.

[Mgal/d, million gallons per day]

Area, in 

square miles

Irrigation rate, 

in Mgal/d

Irrigation rate, in 

inches per year

Predevelopment 0 0 0

1880-1899 0 0 0

1900-1909 48.8 155 67

1910-1919 48.8 185 80

1920-1929 45.2 208 97

1930-1939 43.8 222 106

1940-1949 38.7 215 117

1950-1959 33.4 187 118

1960-1969 38.1 184 102

1970-1974 36.2 189 110

1975-1979 18.6 not estimated1 112

1980-1984 4.3 not estimated1 112

1985-1989 2.6 not estimated1 112

1990-1994 2.6 not estimated1 112

1995-2001 0 0 0

1

Irrigation rate for furrow-irrigated sugarcane fields was not estimated from wateruse information because of uncertainty in distribution of water used for furrow- and 

drip-irrigated sugarcane. Irrigation rate for furrow-irrigated sugarcane fields estimated from 

the time-weighted average value during 1940 to 1974.

value of 0.2, and for all other rock types effective porosity was 

assigned a value of 0.1. 

For all rock types, the transverse dispersivity was 

assigned a value of 0.82 ft (0.25 m) (Souza Voss, 1987) (table 

5). For the volcanic-rock aquifers, longitudinal dispersivity 

was assigned a value of 250 ft (76 m) in the horizontal direction (corresponding to the major and semi-major axes of the 

permeability tensor) (Souza and Voss, 1987) and 25 ft (7.6 m) 

in the vertical direction (corresponding to the minor axis of 

the permeability tensor). For the upper-limestone unit of the 

caprock, longitudinal dispersivity was assigned a value of 250 

ft (76 m) in the horizontal direction and 25 ft (7.6 m) in the 

vertical direction (Oki and others, 1998). For the low permeability features in the model (valley-fill barriers, Waianae 

confining unit, and caprock exclusive of the upper-limestone 

unit), longitudinal dispersivity was assigned a value of 10 ft (3 

m) (Oki and others, 1998).

To enhance numerical stability near the discharge zones 

of the Pearl Harbor springs and near the inland contact 

between the upper-limestone unit and low-permeability part of 

the caprock, zones of high dispersivity were created within the 

top 66 ft (top two elements) of the model. These zones were 

created by trial and error to eliminate numerical problems that 

result in unrealistic solute-concentration distributions. Within 

these zones of high dispersivity, longitudinal dispersivity 

values were increased by a factor of 3 relative to the values for 

the volcanic rocks and upper-limestone unit. Although these 

high-dispersivity zones may a have local effect on the salinity distribution by enhancing mixing, they do not affect the 

regional distribution of salinity in the aquifer at depth. 

The hydraulic-conductivity values for some geologic 

features, including the upper-limestone unit of the caprock 

(2,500 ft/d horizontal; 25 ft/d vertical), the Waianae confining 

unit (10 ft/d horizontal), and valley-fill barriers (0.058 ft/d), 

were estimated on the basis of published information (Camp 

Dresser and McKee, 1994; Oki and others, 1998; Oki, 1998; 

R.M. Towill Corporation, 1978) and were not varied in the 

model. Souza and Voss (1987) assigned a leakance of 1.25 

× 10-3 d-1 for the elements at the seaward end of their mesh 

to control the ease with which saltwater enters and exits the 

flow system. For this study, the hydraulic conductivity at the 

seaward end of the mesh was assigned a value that resulted 

44  Numerical Simulation of the Effects of Valley-Fill Barriers in the Pearl Harbor Area, Oahu, Hawaii
158o10' 158o00' 157o50'

21o30'21o20'

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2500-01,-02

1900-20

1806-19

1805-04 to -09 1806-11 1806-09,-10

1906-061906-051906-041906-031807-011807-031806-20

2006-01 to -11

2006-142006-13

1905-051905-041905-091905-101905-08

1904-01

2104-012003-052004-041904-02

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2003-081902-03

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1900-221900-23

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2001-122001-10

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2202-21

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2303-03 to -06

2402-01 to -03,-05

2101-01

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2001-082001-142001-132001-032001-04

2002-01 to -08,-10

2002-12

2002-17

2002-192002-18

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2202-03 to -142202-15 to -20

2201-03,-04,-07

2202-01

2201-022202-022101-14

2201-05 2201-14

2301-34 to -39

2401-042300-07

2400-01 to -04

2400-05,-06,-08,-14

2401-07

2400-09

2301-44

2301-01 to -10

2301-11

2301-21 to -32

2459-19,-20,

2300-182300-112300-20

-23,-24

2600-02

2600-03,-04

2659-02,-03

2800-01 to -04

2859-01,-02

2858-01 to -03

2658-01,-02

2557-03

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2703-01

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2455-022355-03 to -052354-01

2254-01

2155-04

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2154-012052-08

2153-10 to -122153-062054-012054-02,-03

2053-10,-112053-052053-032053-082053-12

2053-022053-06

2153-04,-052153-07,-082153-012153-022053-09

2457-13 to -152457-05 to -122456-01 to -03

2357-23,-24

2357-21

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2256-05 to -09

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2458-03

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2358-44

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2358-36

2458-01

2356-54

2356-14 to -332356-34 to -422356-55,-56

2356-61,-62,-65

2356-70

2355-09 to -142356-58,-592355-02

2356-44

2355-06,-072255-35,-362255-37 to -392255-32

2255-21 to -282255-07 to -20, 29 to -31

2459-21

2359-032359-05

2359-15

2359-17

2359-10

2358-42

2358-49

2358-24

2358-28

2358-48

2356-49,-50

2356-60,-63,-64

2459-01 to -14

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Barbers

Point MAMALA BAY

Base modified from U.S. Geological Survey NationalHydrography Dataset, Albers equal area projection, standard parallels 21o19'40" and 21o38'20", central meridian 157o58', datum NAD83. Relief from U.S. Geological Survey digital elevation models, 1:24,000

Boundary of Pearl Harbor area

Figure 23. Selected withdrawal wells used in construction of the numerical model of the Pearl Harbor area and the Moanalua ground-water area, Oahu, Hawaii.

Simulation of Ground-Water Flow  45
 Table 5. Aquifer-property values used in the construction of the numerical ground-water model of the Pearl Harbor area, Oahu, 

Hawaii.

[ft, feet; ft/d, feet per day; ft2/lb, feet squared per pound]

Parameter Estimated value

Hydraulic conductivity (ft/d) Vertical Horizontal,

transverse

Horizontal,

longitudinal

Volcanic-rock aquifer 7.5 1,5001 4,5002

Caprock3, upper-limestone unit 25 2,500 2,500

Caprock3, low-permeability unit

Above Waianae Volcanics 0.3 0.3 0.3

Above Koolau Basalt, west of Waiawa Stream 0.01 0.01 0.01

Above Koolau Basalt, east of Waiawa Stream 0.6 0.6 0.6

Valley-fill barriers 0.058 0.058 0.058

Waianae confining unit 7.5 10 10

Seaward boundary below caprock (last row of 

elements) 7.5 30 30

Dispersivity (ft) Transverse Longitudinal,

minimum4

Longitudinal,

middle and

maxmum5

Volcanic-rock aquifer 0.82 25 250

Caprock, upper-limestone unit 0.82 25 250

Caprock, low-permeability unit 0.82 10 10

Valley-fill barriers 0.82 10 10

Waianae confining unit 0.82 10 10

Seaward boundary below caprock (last row of 

elements) 0.82 25 250

High-dispersivity zones 0.82 75 750

Porosity (and specific yield)

Upper limestone unit 0.2

Volcanic-rock aquifer, east of Waiawa Stream 0.04

All other rocks 0.1

Solid-matrix compressibility (ft2/lb) 1.2 x 10-7

1

The transverse direction represents the direction transverse to the general lava-flow direction.

2

The longitudinal direction represents the general lava-flow direction.

3

In the model, the caprock is represented by an upper-limestone unit and a low-permeability unit with hydraulic-conductivity values that vary spatially 

depending on whether the caprock overlies Waianae Volcanics or Koolau Basalt, and whether the caprock over Koolau Basalt is east or west of Waiawa Stream.

4

The longitudinal, minimum dispersivity is the longitudinal dispersivity for flow in the direction of the minimum (vertical) hydraulic conductivity.

5

The longitudinal, middle dispersivity is the longitudinal dispersivity for flow in the direction of the middle (horizontal transverse) hydraulic conductivity. The 

longitudinal, maximum dispersivity is the longitudinal dispersivity for flow in the direction of the maximum (horizontal longitudinal) hydraulic conductivity.

46  Numerical Simulation of the Effects of Valley-Fill Barriers in the Pearl Harbor Area, Oahu, Hawaii
in a leakance about one order of magnitude higher than the 

value used by Souza and Voss as this tended to produce a 

better overall match between simulated and measured water 

levels and salinity profiles. Within the lochs of Pearl Harbor, a layer of sedimentary material (typically about 33-ft or 

1-element thick) was assumed to overlie the upper-limestone 

unit and was assigned the same hydraulic-conductivity value 

as the underlying low-permeability caprock beneath the 

upper-limestone unit. 

Different distributions of hydraulic-conductivity values 

for the volcanic-rock aquifers and low-permeability part of the 

caprock were used in the model to match measured water levels and salinity profiles from selected wells in the study area. 

Hydraulic-conductivity values used in the model ranged from 

0.01 ft/d for parts of the caprock to 4,500 ft/d for the volcanic-rock aquifers (table 5). Horizontal hydraulic-conductivity 

values for the volcanic-rock aquifers in the model were 

4,500 ft/d in the assumed direction of the surficial lava flows 

(approximately perpendicular to the existing topographic contours), and 1,500 ft/d in the lateral direction. Vertical hydraulic 

conductivity of the volcanic-rock aquifers in the model was 

7.5 ft/d (Souza and Voss, 1987). 

Evaluation of Simulated Transient Conditions 

1880-2000

Water Levels.—Simulated water levels generally are in 

agreement with measured water levels from representative 

wells in the modeled area (fig. 24). Measured and simulated 

water levels decline regionally until the late 1970s. In the 

western part of the Koolau Basalt aquifer, near well 2101-03, 

measured and simulated water levels increase after the late 

1970s in response to reduced withdrawals for sugarcane irrigation in the area. The water-level recovery after the late 1970s 

is less pronounced in the eastern part of the Koolau Basalt 

aquifer (well 2256-10), mainly because withdrawals in the 

eastern part of the aquifer did not change as much as those in 

the western part, where most of the wells used for sugarcane 

irrigation were located. 

Because recharge in the transient model was averaged 

over periods ranging from 5 to 20 years, interannual variations 

in water levels caused by interannual variations in recharge 

were not represented by the model. Some interannual variability in water levels was represented, however, because of 

variations in withdrawal. 

Within the Koolau Basalt aquifer of the Pearl Harbor 

area, simulated water levels west of Kipapa Stream generally 

are low and simulated water levels east of Waiawa Stream generally are high relative to measured water levels. The model 

underestimates, by about 4 ft, the reported predevelopment 

head near well 2101-03 of 32 ft above mean sea level (fig. 24). 

During the 1950s, a period for which the spatial distribution of 

water levels is relatively well-characterized by available data, 

average simulated water levels generally are within a few feet, 

and sometimes within a foot, of measured water levels (fig. 

25). 

Some of the discrepancy between measured and simulated water levels can be attributed to uncertainties in the 

estimated distribution of hydraulic properties in the model. In 

addition, some of the discrepancy may be related to factors 

including: (1) the reported predevelopment head may be from 

a period with climatic conditions that are not representative of long-term conditions, (2) the estimated distributions 

of recharge for different time periods are uncertain, (3) the 

reported ground-water withdrawal information may be inaccurate, (4) the hydraulic characteristics of the caprock may have 

changed over time because of the drilling of numerous artesian 

wells, which flowed freely at the surface and may have leaked 

in the subsurface. 

Pearl Harbor Springs Discharge.—Discharge from the 

Pearl Harbor springs was modeled as a function of head at 

well 2256-10 (table 2). During the period from about 1970 to 

the early 1980s, simulated discharge from the Pearl Harbor 

springs was in general agreement with measured discharge 

(fig. 26). After the early 1980s, however, simulated spring 

discharge generally was higher than measured discharge. After 

the early 1980s, simulated spring discharge is high mainly 

because simulated water levels at well 2256-10 are higher than 

measured water levels. 

Salinity profiles.—Prior to about 2000, salinity profiles 

from deep monitor wells in the study area were limited to only 

a few wells, including wells at Waipahu (2300-18), Waipio 

(2659-01), and Punanani (2457-04). The BWS periodically 

logs these wells to measure changes in salinity profiles over 

time. In general, measured salinity profiles indicate a rise in 

the brackish-water transition zone over time, and simulated 

salinity profiles are consistent with this trend (fig. 27). The 

shapes of the simulated salinity profiles also generally are 

consistent with the measured profiles. At the Waipahu deep 

monitor well (2300-18), simulated and measured depths where 

salinity is 50 percent that of ocean water are within about 50 

feet of each other. At the Punanani deep monitor well (2457-

04), which is toward the eastern part of the Pearl Harbor area, 

simulated and measured depths where salinity is 50 percent 

that of ocean water may differ by as much as 200 ft. 

Some of the discrepancy between measured and simulated salinity profiles can be attributed to (1) uncertainties in 

the estimated distribution of hydraulic properties in the model, 

(2) borehole flow (Paillet and others, 2002), and (3) additional 

factors described above for simulated water levels.

Simulation of the Effects of Valley-Fill 

Barriers on Water Levels and Salinity

Model sensitivity to the geometry of the valley-fill barriers was tested using four additional, hypothetical valley-fill 

barrier configurations: (1) no barriers; (2) base-case barriers 

deepened by 200 ft, extended inland using a 3 percent slope, 

Simulation of the Effects of Valley-Fill Barriers on Water Levels and Salinity  47
Measured

Simulated

EWA-KUNIA AREA WAIPAHU-WAIAWA AREA 

2703-012103-01 (T19) 2006-01 to -10 

2801-012201-10 (T41) 2101-03

2759-022600-01 (T47) 

1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000

40353025201510

50

3025201510

50

3025201510

403530252015104035302520151040353025201510

403530252015104035302520151040353025201510

2300-10,-18

WATER LEVEL, IN FEET ABOVE MEAN SEA LEVEL 

Figure 24. Measured and simulated (using base-case valley-fill barriers) water levels in selected wells in the Pearl Harbor area, Oahu, Hawaii.

48  Numerical Simulation of the Effects of Valley-Fill Barriers in the Pearl Harbor Area, Oahu, Hawaii
Measured

Simulated

WAIPAHU-WAIAWA AREA* WAIMALU AREA MOANALUA AREA 

1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000

403530252015104035302520151040353025201510

403530252015104035302520151040353025201510

403530252015104035302520151040353025201510

2557-02*Waimalu area 2457-012358-02,-20

2455-01 (T52) 2255-33 (T45) 2256-10

2253-022153-092153-02

WATER LEVEL, IN FEET ABOVE MEAN SEA LEVEL 

Figure 24. Measured and simulated (using base-case valley-fill barriers) water levels in selected wells in the Pearl Harbor area, Oahu, Hawaii—Continued.

Simulation of the Effects of Valley-Fill Barriers on Water Levels and Salinity  49
158o10' 158o00' 157o50'

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5 < d ≤ 150 < d ≤ 5-5 < d ≤ 0-15 < d ≤ -5-25 < d ≤ -15 

DIFFERENCE, d, BETWEEN MEASURED AND SIMULATED 1950S WATER LEVELS, IN PERCENT (Positive values for d indicatethat simulated water levels are higher thanmeasured water levels.)

Barbers

Point MAMALA BAY

Base modified from U.S. Geological Survey NationalHydrography Dataset, Albers equal area projection, standard parallels 21o19'40" and 21o38'20", central meridian 157o58', datum NAD83. Relief from U.S. Geological Survey digital elevation models, 1:24,000

Boundary of Pearl Harbor area

Figure 25. Difference between measured and simulated (using base-case valley-fill barriers) 1950s water levels at selected wells, Pearl Harbor area, Oahu, Hawaii.

50 Numerical Simulation of the Effects of Valley-Fill Barriers in the Pearl Harbor Area, Oahu, Hawaii
0

20

40

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Total Pearl Harbor springs 

Waikele springs 

Waiawa springs 

Waimano−Waiau springs 

1970 1980 1990 2000

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MEASURED

DISCHARGE, IN MILLION GALLONS PER DAY 

Figure 26. Measured and simulated (using base-case valley-fill barriers) discharge from the Pearl Harbor springs, 

Oahu, Hawaii.

Simulation of the Effects of Valley-Fill Barriers on Water Levels and Salinity  51
Measured

11/13/198611/23/199401/03/2002Simulated1970198019902000

Measured04/23/198712/07/199402/13/2002Simulated1970198019902000

Measured11/23/196804/04/199001/30/2001Simulated1970198019902000

-1000-1500

-500

0

Waipahu Deep Monitor Well 2300-18 Punanani Deep Monitor Well 2457-04 

0 20 40 60 80 100 0 20 40 60 80 100 0 20 40 60 80 100

Waipio Deep Monitor Well 2659-01 

SALINITY, IN PERCENT SEAWATER SALINITY SALINITY, IN PERCENT SEAWATER SALINITY SALINITY, IN PERCENT SEAWATER SALINITY 

ALTITUDE, IN FEET RELATIVE TO MEAN SEA LEVEL 

Figure 27. Measured and simulated (using base-case valley-fill barriers) salinity profiles in selected wells in the Pearl Harbor area, Oahu, Hawaii.

52  Numerical Simulation of the Effects of Valley-Fill Barriers in the Pearl Harbor Area, Oahu, Hawaii
and extended seaward with a zero percent slope to where the 

caprock and valley-fill barriers are at common depths; (3) 

Waiawa valley-fill barrier deepened to a constant depth of 660 

ft below mean sea level, extended inland to where the channel 

altitude is 800 ft, and extended seaward to where the caprock 

is at a depth of 660 ft below mean sea level; and (4) Waimalu 

valley-fill barrier deepened to a constant depth of 660 ft 

below mean sea level, extended inland to where the channel 

altitude is 800 ft, and extended seaward to where the caprock 

is at a depth of 660 ft below mean sea level (fig. 28). In the 

absence of definitive information on the valley-fill barriers, the 

hypothetical valley-fill barrier configurations represent a range 

of configurations that may exist. All aspects of the model 

other than the configuration of the valley-fill barriers were 

unchanged for the analysis. 

Simulated water levels in the absence of valley-fill barriers generally were lower, by a few tenths of a foot or less, than 

simulated water levels using the base-case valley-fill barriers 

(figs. 24 and 29) because overall system permeability is higher 

in the absence of valley-fill barriers. With the valley-fill barriers deepened by 200 ft, simulated water levels generally were 

higher, by a few tenths of a foot, than simulated water levels in 

the base case, although simulated water levels were lower in 

some places near the eastern part of the Pearl Harbor area (see 

for example wells 2256-10, 2355-33, and 2455-01) with the 

deepened valley-fill barriers (figs. 24 and 30). 

Deepening the Waiawa valley-fill barrier to 660 ft below 

mean sea level resulted in an increase in simulated water levels 

west of the Waiawa valley-fill barrier by as much as a foot 

relative to the base case (see wells 2101-03 and 2201-10 in 

the western part of the Pearl Harbor area in figs. 24 and 31), 

which represents an improvement in simulated water levels 

relative to the base case. Simulated water levels just east of the 

Waiawa valley-fill barrier were lower by a few tenths of a foot 

relative to the base case (see wells 2358-02, -20 in the central 

part of the Pearl Harbor area in figs. 24 and 31), which also 

represents an improvement in simulated water levels relative 

to the base case for most periods. The increase in simulated 

water levels west of the deepened Waiawa valley-fill barrier 

and the decrease in simulated water levels east of the barrier 

result from a redistribution of ground-water flow relative to the 

base case. 

Deepening the Waimalu valley-fill barrier to 660 ft below 

mean sea level resulted in an increase in simulated water levels 

west of the Waimalu valley-fill barrier by as much as a foot 

relative to the base case (see wells 2101-03 and 2201-10 in 

the western part of the Pearl Harbor area in figs. 24 and 32), 

which represents an improvement in simulated water levels 

relative to the base case. Simulated water levels in the central 

part of the Pearl Harbor area also increased by about a foot 

relative to the base case (see wells 2358-02, -20 in figs. 24 and 

32), and this represents a decrease in accuracy in simulated 

water levels relative to the base case. Simulated water levels 

just east of the Waimalu valley-fill barrier were lower by a few 

tenths of a foot relative to the base case (see wells 2256-10 

and 2255-33 in figs. 24 and 32), which represents a slight 

improvement in simulated water levels relative to the base 

case. The increase in simulated water levels west of the deepened Waimalu valley-fill barrier and the decrease in simulated 

water levels east of the barrier result from a redistribution of 

ground-water flow relative to the base case. 

Simulated salinity profiles generally were consistent with 

the simulated water levels. For example, in the absence of 

valley-fill barriers, simulated salinity profiles were shallower, 

by about 10 ft, than simulated salinity profiles at common sites 

and times with the base-case valley-fill barriers. This result is 

consistent with the lower water levels simulated in the absence 

of valley-fill barriers relative to the base case. 

Deepening the Waiawa valley-fill barrier to 660 ft below 

mean sea level generally resulted in a deeper simulated transition zone west of the Waiawa valley-fill barrier by as much as 

a few tens of feet in some places relative to the base case for 

common sites and times (figs. 27 and 33). At the Punanani 

deep monitor well (2457-04) east of the Waiawa valley-fill 

barrier, the transition zone was widened because of enhanced 

dispersion in the area (figs. 27 and 33).

Simulation of Redistributed 

Withdrawals 2001-2025

The model constructed for this study was used to simulate the hydrologic effects of redistributing ground-water 

withdrawals by reducing withdrawals in the eastern part of 

the Waimalu area and increasing withdrawals farther to the 

west by an equal amount. The simulated initial conditions for 

redistributed withdrawal scenarios were the final conditions 

from the appropriate (depending on the valley-fill barriers 

simulated) 1880-2000 transient simulation. The effects of 

redistributing withdrawals were simulated with 25-year transient simulations from 2001-2025 using average recharge from 

the period 1995-2000 for the top of the model and predevelopment recharge for the inland vertical boundaries. Assigned 

total recharge over the model domain for the period 2001-2025 

(274 Mgal/d) is lower than the long-term average and also is 

lower than estimated predevelopment recharge (307 Mgal/d). 

A simulation with withdrawals equal to the 2003 permitted 

rates at all wells (table 6) was used as the basis for comparison 

with various redistributed withdrawal scenarios. 

Seven redistributed withdrawal scenarios were tested 

(table 7) using the base-case valley-fill barriers. (For one of 

the redistributed withdrawal scenarios, scenario 1, two additional valley-fill barrier configurations were tested.) In these 

scenarios, withdrawals from Halawa Shaft (2354-01) or the 

Kalauao Wells (2355-09 to -14) were reduced and withdrawals from Pearl City III (2557-03) or Kunia III (2401-04) were 

increased. The Halawa Shaft and Kalauao Wells are located 

in the eastern part of the Waimalu management system, Pearl 

City III is located just west of the Waimalu management 

system within the Waipahu-Waiawa management system, 

Simulation of Redistributed Withdrawals 2001-2025  53
158o10' 158o00' 157o50'

21o30'21o20'

158o10' 158o00' 157o50'

21o30'21o20'

158o10' 158o00' 157o50'

21o30'21o20'

158o10' 158o00' 157o50'

21o30'21o20'

Topographic Divide

Topographic Divide

Topographic Divide

Topographic Divide

00

4 MILES 2

2 4 KILOMETERS 

D

GREATER THAN 300 GREATER THAN 225 AND LESS THAN OR EQUAL TO 300 GREATER THAN 150 AND LESS THAN OR EQUAL TO 225 GREATER THAN 75 AND LESS THAN OR EQUAL TO 150 GREATER THAN 0 AND LESS THAN OR EQUAL TO 75 

A

DEPTH OF VALLEY-FILL BARRIER, IN FEET BELOW MEAN SEA LEVEL 

C

B

Pacific Ocean

Area of 

Map

Oahu

Figure 28. Valley-fill barrier depths and configurations used in sensitivity tests of the numerical ground-water model, Pearl Harbor area, Oahu, Hawaii. Valley-fill-barrier configurations shown are for the following cases: (A) the base case; (B) base-case valley-fill barriers deepened by 200 feet, extended inland using a 3-percent slope, and extended seaward using a zero-percent slope; (C) Waiawa valley-fill barrier deepened to a constant depth of 660 feet below mean sea level, extended inland to where the channel altitude is 800 feet, and extended seaward to where the caprock is at a depth of 660 feet below mean sea level; and (D) Waimalu valley-fill barrier deepened to a constant depth of 660 feet below mean sea level, extended inland to where the channel altitude is 800 feet, and extended seaward to where the caprock is at a depth of 660 feet below mean sea level.

54  Numerical Simulation of the Effects of Valley-Fill Barriers in the Pearl Harbor Area, Oahu, Hawaii
Measured

Simulated

EWA-KUNIA AREA WAIPAHU-WAIAWA AREA 

2703-012103-01 (T19) 2006-01 to -10 

2801-012201-10 (T41) 2101-03

2759-022600-01 (T47) 

1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000

40353025201510

50

3025201510

50

3025201510

403530252015104035302520151040353025201510

403530252015104035302520151040353025201510

2300-10,-18

WATER LEVEL, IN FEET ABOVE MEAN SEA LEVEL 

Figure 29. Measured and simulated (with no valley-fill barriers) water levels in selected wells in the Pearl Harbor area, Oahu, Hawaii.

Simulation of Redistributed Withdrawals 2001-2025  55
Measured

Simulated

WAIPAHU-WAIAWA AREA* WAIMALU AREA MOANALUA AREA 

1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000

403530252015104035302520151040353025201510

403530252015104035302520151040353025201510

403530252015104035302520151040353025201510

2557-02*Waimalu area 2457-012358-02,-20

2455-01 (T52) 2255-33 (T45) 2256-10

2253-022153-092153-02

WATER LEVEL, IN FEET ABOVE MEAN SEA LEVEL 

Figure 29. Measured and simulated (with no valley-fill barriers) water levels in selected wells in the Pearl Harbor area, Oahu, Hawaii—Continued.

56  Numerical Simulation of the Effects of Valley-Fill Barriers in the Pearl Harbor Area, Oahu, Hawaii
Measured

Simulated

EWA-KUNIA AREA WAIPAHU-WAIAWA AREA 

2703-012103-01 (T19) 2006-01 to -10 

2801-012201-10 (T41) 2101-03

2759-022600-01 (T47) 

1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000

40353025201510

50

3025201510

50

3025201510

403530252015104035302520151040353025201510

403530252015104035302520151040353025201510

2300-10,-18

WATER LEVEL, IN FEET ABOVE MEAN SEA LEVEL 

Figure 30. Measured and simulated (with base-case valley-fill barriers deepened by 200 ft) water levels in selected wells in the Pearl Harbor area, Oahu, Hawaii.

Simulation of Redistributed Withdrawals 2001-2025  57
Measured

Simulated

WAIPAHU-WAIAWA AREA* WAIMALU AREA MOANALUA AREA 

1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000

403530252015104035302520151040353025201510

403530252015104035302520151040353025201510

403530252015104035302520151040353025201510

2557-02*Waimalu area 2457-012358-02,-20

2455-01 (T52) 2255-33 (T45) 2256-10

2253-022153-092153-02

WATER LEVEL, IN FEET ABOVE MEAN SEA LEVEL 

Figure 30. Measured and simulated (with base-case valley-fill barriers deepened by 200 ft) water levels in selected wells in the Pearl Harbor area, Oahu, Hawaii—Continued.

58  Numerical Simulation of the Effects of Valley-Fill Barriers in the Pearl Harbor Area, Oahu, Hawaii
Measured

Simulated

EWA-KUNIA AREA WAIPAHU-WAIAWA AREA 

2703-012103-01 (T19) 2006-01 to -10 

2801-012201-10 (T41) 2101-03

2759-022600-01 (T47) 

1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000

40353025201510

50

3025201510

50

3025201510

403530252015104035302520151040353025201510

403530252015104035302520151040353025201510

2300-10,-18

WATER LEVEL, IN FEET ABOVE MEAN SEA LEVEL 

Figure 31. Measured and simulated (with Waiawa valley-fill barrier deepened to 660 ft below mean sea level) water levels in selected wells in the Pearl Harbor area, Oahu, Hawaii.

Simulation of Redistributed Withdrawals 2001-2025  59
Measured

Simulated

WAIPAHU-WAIAWA AREA* WAIMALU AREA MOANALUA AREA 

1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000

403530252015104035302520151040353025201510

403530252015104035302520151040353025201510

403530252015104035302520151040353025201510

2557-02*Waimalu area 2457-012358-02,-20

2455-01 (T52) 2255-33 (T45) 2256-10

2253-022153-092153-02

WATER LEVEL, IN FEET ABOVE MEAN SEA LEVEL 

Figure 31. Measured and simulated (with Waiawa valley-fill barrier deepened to 660 ft below mean sea level) water levels in selected wells in the Pearl Harbor area, Oahu, Hawaii—Continued.

60 Numerical Simulation of the Effects of Valley-Fill Barriers in the Pearl Harbor Area, Oahu, Hawaii
Measured

Simulated

EWA-KUNIA AREA WAIPAHU-WAIAWA AREA 

2703-012103-01 (T19) 2006-01 to -10 

2801-012201-10 (T41) 2101-03

2759-022600-01 (T47) 

1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000

40353025201510

50

3025201510

50

3025201510

403530252015104035302520151040353025201510

403530252015104035302520151040353025201510

2300-10,-18

WATER LEVEL, IN FEET ABOVE MEAN SEA LEVEL 

Figure 32. Measured and simulated (with Waimalu valley-fill barrier deepened to 660 ft below mean sea level) water levels in selected wells in the Pearl Harbor area, Oahu, Hawaii.

Simulation of Redistributed Withdrawals 2001-2025  61
Measured

Simulated

WAIPAHU-WAIAWA AREA* WAIMALU AREA MOANALUA AREA 

1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 1880 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000

403530252015104035302520151040353025201510

403530252015104035302520151040353025201510

403530252015104035302520151040353025201510

2557-02*Waimalu area 2457-012358-02,-20

2455-01 (T52) 2255-33 (T45) 2256-10

2253-022153-092153-02

WATER LEVEL, IN FEET ABOVE MEAN SEA LEVEL 

Figure 32. Measured and simulated (with Waimalu valley-fill barrier deepened to 660 ft below mean sea level) water levels in selected wells in the Pearl Harbor area, Oahu, Hawaii—Continued.

62  Numerical Simulation of the Effects of Valley-Fill Barriers in the Pearl Harbor Area, Oahu, Hawaii
Measured

11/13/198611/23/199401/03/2002Simulated1970198019902000

Measured04/23/198712/07/199402/13/2002Simulated1970198019902000

Measured11/23/196804/04/199001/30/2001Simulated1970198019902000

-1000-1500

-500

0

Waipahu Deep Monitor Well 2300-18 Punanani Deep Monitor Well 2457-04 

0 20 40 60 80 100 0 20 40 60 80 100 0 20 40 60 80 100

Waipio Deep Monitor Well 2659-01 

SALINITY, IN PERCENT SEAWATER SALINITY SALINITY, IN PERCENT SEAWATER SALINITY SALINITY, IN PERCENT SEAWATER SALINITY 

ALTITUDE, IN FEET RELATIVE TO MEAN SEA LEVEL 

Figure 33. Measured and simulated (with Waiawa valley-fill barrier deepened to 660 feet below mean sea level) salinity profiles in selected wells in the Pearl Harbor area, Oahu, Hawaii.

Simulation of Redistributed Withdrawals 2001-2025  63
Table 6. 2003 permitted withdrawal rates from the Pearl Harbor and Moanalua areas, Oahu, Hawaii.

[Mgal/d, million gallons per day; well nos. indicated in bold represent Maui-type shafts with infiltration tunnels]

Well no. 2003 permitted

withdrawal, in Mgal/d Well no. 2003 permittedwithdrawal, in Mgal/d

1805-04 3.168 2300-11 0.68

1806-09 2.26 2300-20 0.4

1900-02 1.201 2301-01 to -10 0.95

1900-21 0.1 2301-34 to -39 6.61

1900-22 0.6 2301-44 1

1900-23 0.023 2302-01 to -04 4.357

1901-05 0.056 2303-01,-02 2.24

1901-06 3.3 2303-03 to -06 4.48

1902-03 0.5 2354-01 11.32

1905-04 1 2355-03 to -05 0.98

1905-05 0.5 2355-06,-07 1.3

1905-08 0.302 2355-09 to -14 11.75

2001-01 5.89 2356-49,-50 0.08

2001-02 0.08 2356-54 0.33

2001-03 0.03 2356-55,-56 1.35

2001-04 0.04 2356-58,-59 1.2

2001-05 0.066 2356-70 0.1

2001-06 0.08 2357-23,-24 1.11

2001-07 0.063 2358-36 0.004

2001-08 0.048 2358-44 0.04

2001-09 0.023 2358-49 0.003

2001-10 0.022 2359-10 0.005

2001-12 0.249 2359-19 0.18

2001-13 0.8 2400-01 to -04 6

2001-14 0.892 2400-05,-06,-08,-14 2.1

2002-12 0.04 2400-09 3.029

2002-17 0.498 2401-04 1.5

2003-01 1 2401-07 0.6

2003-04 0.494 2402-01 to -03, -05 2.71

2003-08 0.237 2455-02 0.158

2004-04 1.5 2456-01 to -03 1.5

2006-01 to -11 0.957 2457-01 to -03 1.8

2006-13 0.7 2457-05 to -12 11.97

2006-14 1 2457-13 to -15 1.89

2052-08 9.5 2458-01 1.22

2053-11 1.035 2458-03,-04 0.7

2101-01 0.11 2458-05 0.1

2101-14 0.216 2459-19,-20 0.63

2102-02,-04 to -22 7.969 2459-21 0.006

2103-03 2.337 2459-23,-24 0.68

2104-01 0.168 2500-01,-02 1

2153-02 0.021 2557-01,-02 0.136

2153-07,-08 0.609 2557-03 0.5

2153-10 to -12 3.79 2558-10 14.977

2154-01 0.346 2600-02 0.1

2201-02 0.021 2600-03,-04 1.55

2201-14 0.003 2603-01 0.4

2202-01 0.003 2659-02,-03 0.85

2202-02 0.009 2703-01 1.075

2202-21 12.154 2800-01 to -04 2.98

2254-01 4.659 2858-01 to -03 1.722

2255-32 0.697 2859-01,-02 1.9

2255-37 to -39 1.08 STATE DHHL [01] 1.358

Total 188.056

64  Numerical Simulation of the Effects of Valley-Fill Barriers in the Pearl Harbor Area, Oahu, Hawaii
Table 7. Summary of simulated withdrawals for redistributed withdrawal scenarios in the Pearl Harbor area, 

Oahu, Hawaii1.

[Mgal/d, million gallons per day]

Simulated withdrawal, in Mgal/d

Scenario Halawa Shaft 

(2354-01)

Kalauao Wells 

(2355-09 to -14)

Pearl City III 

(2557-03)

Kunia III

(2401-04) Total

Base case 11.32 11.75 0.50 1.50 25.07

1 5.66 11.75 6.16 1.50 25.07

2 8.49 11.75 3.33 1.50 25.07

3 5.66 11.75 0.50 7.16 25.07

4 11.32 5.88 6.38 1.50 25.08

5 11.32 8.81 3.44 1.50 25.07

6 11.32 5.88 0.50 7.38 25.08

7 8.49 8.81 0.50 7.27 25.07

1

Simluated withdrawals from all wells in the modeled area that are not listed in the table were equal to the 2003 permitted rates.

and Kunia III is located in the western part of the WaipahuWaiawa management system (fig. 1).

For each of the seven scenarios tested, model-simulation 

results are shown in terms of the change in the depth of 

the bottom of the freshwater (2-percent salinity) part of the 

ground-water system. In general, a reduction of withdrawal 

from a site causes a deepening of the 2-percent salinity 

depth (increase in freshwater thickness) near that site, and an 

increase of withdrawal from a site causes a shallowing of the 

2-percent salinity depth (decrease in freshwater thickness) 

near that site. 

Scenario 1

In scenario 1, withdrawal from Halawa Shaft (2354-01) 

was reduced by 5.66 Mgal/d and withdrawal from Pearl City 

III (2557-03) was increased by 5.66 Mgal/d relative to the 

2003 permitted rates. Model results indicate that the 2-percent 

salinity depth does not change (0-ft line of equal change in 2-

percent salinity depth) along a line that runs from Pearl Harbor 

to the inland extent of the model, about midway between 

Halawa Shaft and Pearl City III (fig. 34). East of the 0-ft line 

of equal change, toward Halawa Shaft, the 2-percent salinity depth deepens in response to decreased withdrawal from 

Halawa Shaft. West of the 0-ft line of equal change, toward 

Pearl City III, the 2-percent salinity depth shallows in response 

to increased withdrawal from Pearl City III. Near Halawa 

Shaft the 2-percent salinity depth deepens by about 30 ft, and 

near Pearl City III the 2-percent salinity depth shallows by 

about 20 ft. 

Simulated changes in the 2-percent salinity depth are 

greatest downgradient from the wells with redistributed withdrawals, not directly beneath the wells as might be expected 

if local upconing were the only process by which underlying 

brackish water moved in response to increased withdrawal. 

Because brackish water moves both landward and upward 

into areas previously occupied by freshwater in response to 

increased withdrawal, the location where the simulated shallowing of the 2-percent salinity depth is greatest is downgradient of Pearl City III, where withdrawal was increased in the 

model. Similarly, because freshwater water moves both seaward and downward into areas previously occupied by brackish water in response to decreased withdrawal, the location 

where the simulated deepening of the 2-percent salinity depth 

is greatest is downgradient of Halawa Shaft, where withdrawal 

was decreased in the model. In scenario 1, the change in 50-

percent salinity depth caused by the redistributed withdrawal 

is less than 15 ft. 

For scenario 1 only, the effects of two additional valleyfill barrier configurations were tested: (1) no valley-fill barriers, (2) Waiawa valley-fill barrier deepened to a constant depth 

of 660 ft below mean sea level, extended inland to where the 

channel altitude is 800 ft, and extended seaward to where the 

caprock is at a depth of 660 ft below mean sea level. Initial 

conditions for simulations with the additional valley-fill barrier configurations were the final conditions from 1880-2000 

transient simulations using these additional valley-fill barrier 

configurations. In the absence of valley-fill barriers, the simulated deepening of the 2-percent salinity depth east of Halawa 

Shaft is increased relative to the simulated deepening using the 

Simulation of Redistributed Withdrawals 2001-2025  65
Kipapa

Waiawa

Waimalu

Halawa

158o10' 158o00' 157o50'

21o30'21o20'

Topographic

Divide

00

4 MILES 2

2 4 KILOMETERS

PacificOcean

Area of

Map

Oahu

0

-10

-20

10

10

20

-10

0

H

H

Pearl City III (increase 

withdrawal by 5.66 Mgal/d)

Halawa Shaft (reduce 

withdrawal by 5.66 Mgal/d)

SCENARIO 1

VOLCANIC-ROCK AQUIFER (UNCONFINED)COASTAL CONFINING UNIT (CAPROCK) OVERLYING VOLCANIC-ROCK AQUIFERVALLEY-FILL BARRIER INLAND FROM CAPROCKVALLEY-FILL BARRIER BENEATH CAPROCKWAIANAE CONFINING UNIT INLAND FROM CAPROCKWAIANAE CONFINING UNIT BENEATH CAPROCKSEAWARD BOUNDARY BENEATH CAPROCKLINE OF EQUAL CHANGE IN 2-PERCENT SALINITY DEPTH, IN FEET--Interval 10 feet NEGATIVE CHANGE (LOWERING OF 2-PERCENT SALINITY DEPTH)  ZERO CHANGE POSITIVE CHANGE (RISE OF 2-PERCENT SALINITY DEPTH)WELL H

EXPLANATION

Figure 34. Simulated change in 2-percent salinity depth caused by reducing withdrawal from the Halawa Shaft (2354-01) by 5.66 million gallons per day and increasing withdrawal from Pearl City III (2557-03) by the same amount relative to the 2003 permitted rates. Salinity changes were determined by comparing two simulations that differ only in the rates of withdrawal from the Halawa Shaft and Pearl City III; the first simulation includes withdrawals equal to the 2003 permitted rates from all wells in the modeled area, and the second simulation includes reduced withdrawal from Halawa Shaft (11.32 to 5.66 million gallons per day), increased withdrawal from Pearl City III (0.5 to 6.16 million gallons per day), and withdrawals equal to the 2003 permitted rates from all other wells in the modeled area. Salinity changes shown are after 25 years of simulation using the ending results from the 1880-2000 transient simulation as initial conditions. 

66  Numerical Simulation of the Effects of Valley-Fill Barriers in the Pearl Harbor Area, Oahu, Hawaii
base case valley-fill barriers (figs. 34 and 35). With Waiawa 

valley-fill barrier deepened to 660 ft below mean sea level, 

the simulated deepening of the 2-percent salinity depth east 

of Halawa Shaft is slightly decreased relative to the simulated 

deepening using the base case valley-fill barriers (figs. 34 and 

36). In all cases, the simulated deepening of the 2-percent 

salinity depth downgradient of Halawa Shaft exceeds 50 ft. 

With Waiawa valley-fill barrier deepened to 660 ft below mean 

sea level, the simulated shallowing of the 2-percent salinity depth near Pearl City III is truncated west of the Waiawa 

valley-fill barrier relative to the base-case valley-fill barriers 

and no valley-fill barrier case. The 0-ft line of equal change in 

2-percent salinity depth does not vary much with the different 

valley-fill barrier configurations tested. 

The locations where change in 2-percent salinity depth 

are greatest are controlled by factors including, (1) proximity 

of the pumped wells to brackish ground water, (2) hydraulic 

characteristics of the rocks (horizontal and vertical permeability), and (3) presence of low-permeability barriers. 

Saltwater intrusion can be enhanced if (1) pumping rates are 

high, (2) wells are drilled close to a source of brackish ground 

water, (3) aquifer permeability, particularly in the vertical 

direction, is high, and (4) pumped wells are located close to 

low-permeability valley-fill barriers. 

Scenario 2

In scenario 2, withdrawal from Halawa Shaft (2354-01) 

was reduced by 2.83 Mgal/d and withdrawal from Pearl City 

III (2557-03) was increased by 2.83 Mgal/d relative to the 

2003 permitted rates. The location of the 0-ft line of equal 

change in 2-percent salinity depth simulated in scenario 2 is 

nearly the same as that simulated in scenario 1 (figs. 34 and 

37). Near Halawa Shaft, the 2-percent salinity depth deepens 

by about 15 ft, and near Pearl City III the 2-percent salinity 

depth shallows by about 10 ft. In scenario 2, the reduction 

in withdrawal from Halawa Shaft is half that simulated in 

scenario 1. At common locations, the simulated change in 

2-percent salinity depth in scenario 2 also is about half the 

magnitude of the simulated change in scenario 1. In scenario 

2, the change in 50-percent salinity depth caused by the redistributed withdrawal is less than 10 ft.

Scenario 3

In scenario 3, withdrawal from Halawa Shaft (2354-01) 

was reduced by 5.66 Mgal/d and withdrawal from Kunia III 

(2401-04) was increased by 5.66 Mgal/d relative to the 2003 

permitted rates. Model results indicate that the 2-percent 

salinity depth does not change (0-ft line of equal change in 

2-percent salinity depth) along a line that runs from Pearl Harbor to the inland extent of the model, about midway between 

Halawa Shaft and Kunia III (fig. 38). Relative to scenario 

1, the 0-ft line of equal change in 2-percent salinity depth 

simulated in scenario 3 extends farther westward, indicating a 

larger zone where freshwater thickness increases in scenario 

3 relative to scenario 1. Thus, by redistributing 5.66 Mgal/d 

from Pearl City III (scenario 1) to Kunia III (scenario 3), 

located farther to the west, the zone where freshwater thickness increases expands westward. Near Halawa Shaft the 2-

percent salinity depth deepens by about 30 ft, and near Kunia 

III the 2-percent salinity depth shallows by about 35 ft. 

In scenario 3, shallowing of the 50-percent salinity depth 

is greatest to the southwest of Kunia III, and is as much as 

40 ft (fig. 39). Shallowing of the 50-percent salinity depth is 

enhanced by the presence of the low-permeability Waianae 

confining unit, which is represented in the model as a vertical 

barrier. 

Scenario 4

In scenario 4, withdrawal from the Kalauao Wells 

(2355-09 to -14) was reduced by 5.88 Mgal/d and withdrawal 

from Pearl City III (2557-03) was increased by 5.88 Mgal/d 

relative to the 2003 permitted rates. Model results indicate that 

the 2-percent salinity depth does not change (0-ft line of equal 

change in 2-percent salinity depth) along a line that runs from 

Pearl Harbor to the inland extent of the model, about a third 

of the way from the Kalauao Wells to Pearl City III (fig. 40). 

East of the 0-ft line of equal change, toward the Kalauao 

Wells, the 2-percent salinity depth deepens in response to 

decreased withdrawal from the Kalauao Wells. West of the 0-ft 

line of equal change, toward Pearl City III, the 2-percent salinity depth shallows in response to increased withdrawal from 

Pearl City III. Near the Kalauao Wells the 2-percent salinity depth deepens by about 20 ft, and near Pearl City III the 

2-percent salinity depth shallows by about 20 ft. In scenario 4, 

the change in 50-percent salinity depth caused by the redistributed withdrawal is less than 15 ft.

Scenarios 1 and 4 are similar in the amount of redistributed withdrawal to Pearl City III (5.66 Mgal/d in scenario 

1 and 5.88 Mgal/d in scenario 4). The size and shape of the 

zones in which freshwater thickness increases also are similar 

in scenarios 1 and 4. In general, however, the deepening of 

the 2-percent salinity depth is greater in scenario 1 relative to 

scenario 4. Within the simulated zones in which freshwater 

thickness decreases, shallowing of the 2-percent salinity depth 

is slightly greater in scenario 4 relative to scenario 1 because 

simulated withdrawal from Pearl City III is slightly higher in 

scenario 4.

Scenario 5

In scenario 5, withdrawal from the Kalauao Wells (2355-

09 to -14) was reduced by 2.94 Mgal/d and withdrawal from 

Pearl City III (2557-03) was increased by 2.94 Mgal/d relative 

to the 2003 permitted rates. The 0-ft line of equal change in 

2-percent salinity depth simulated in scenario 5 is nearly the 

same as that simulated in scenario 4 (figs. 40 and 41). Near the 

Kalauao Wells the 2-percent salinity depth deepens by about 

Simulation of Redistributed Withdrawals 2001-2025  67
158o10' 158o00' 157o50'

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-10

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-10

H

H

Halawa Shaft (reduce 

withdrawal by 5.66 Mgal/d)

Pearl City III (increase 

withdrawal by 5.66 Mgal/d)

VOLCANIC-ROCK AQUIFER (UNCONFINED)COASTAL CONFINING UNIT (CAPROCK) OVERLYING VOLCANIC-ROCK AQUIFERWAIANAE CONFINING UNIT INLAND FROM CAPROCKWAIANAE CONFINING UNIT BENEATH CAPROCKSEAWARD BOUNDARY BENEATH CAPROCKLINE OF EQUAL CHANGE IN 2-PERCENT SALINITY DEPTH, IN FEET--Interval 10 feet  NEGATIVE CHANGE (LOWERING OF 2-PERCENT SALINITY DEPTH)  ZERO CHANGE POSITIVE CHANGE (RISE OF 2-PERCENT SALINITY DEPTH)WELL H

EXPLANATION

Figure 35. Simulated (with no valley-fill barriers) change in 2-percent salinity depth caused by reducing withdrawal from the Halawa Shaft (2354-01) by 5.66 million gallons per day and increasing withdrawal from Pearl City III (2557-03) by the same amount relative to the 2003 permitted rates. Salinity changes were determined by comparing two simulations that differ only in the rates of withdrawal from the Halawa Shaft and Pearl City III; the first simulation includes withdrawals equal to the 2003 permitted rates from all wells in the modeled area, and the second simulation includes reduced withdrawal from Halawa Shaft (11.32 to 5.66 million gallons per day), increased withdrawal from Pearl City III (0.5 to 6.16 million gallons per day), and withdrawals equal to the 2003 permitted rates from all other wells in the modeled area. Salinity changes shown are after 25 years of simulation using the ending results from the 1880-2000 transient simulation as initial conditions. 

68  Numerical Simulation of the Effects of Valley-Fill Barriers in the Pearl Harbor Area, Oahu, Hawaii
Kipapa

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Waimalu

Halawa

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10

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H

H

Pearl City III (increase 

withdrawal by 5.66 Mgal/d)

Halawa Shaft (reduce 

withdrawal by 5.66 Mgal/d)

Kipapa

Waiawa

Waimalu

Halawa

VOLCANIC-ROCK AQUIFER (UNCONFINED)COASTAL CONFINING UNIT (CAPROCK) OVERLYING VOLCANIC-ROCK AQUIFERVALLEY-FILL BARRIER INLAND FROM CAPROCKVALLEY-FILL BARRIER BENEATH CAPROCKWAIANAE CONFINING UNIT INLAND FROM CAPROCKWAIANAE CONFINING UNIT BENEATH CAPROCKSEAWARD BOUNDARY BENEATH CAPROCKLINE OF EQUAL CHANGE IN 2-PERCENT SALINITY DEPTH, IN FEET--Interval 10 feet NEGATIVE CHANGE (LOWERING OF 2-PERCENT SALINITY DEPTH)  ZERO CHANGE POSITIVE CHANGE (RISE OF 2-PERCENT SALINITY DEPTH)WELL H

EXPLANATION

Figure 36. Simulated (with Waiawa valley-fill barrier deepened to 660 feet below mean sea level) change in 2-percent salinity depth caused by reducing withdrawal from the Halawa Shaft (2354-01) by 5.66 million gallons per day and increasing withdrawal from Pearl City III (2557-03) by the same amount relative to the 2003 permitted rates. Salinity changes were determined by comparing two simulations that differ only in the rates of withdrawal from the Halawa Shaft and Pearl City III; the first simulation includes withdrawals equal to the 2003 permitted rates from all wells in the modeled area, and the second simulation includes reduced withdrawal from Halawa Shaft (11.32 to 5.66 million gallons per day), increased withdrawal from Pearl City III (0.5 to 6.16 million gallons per day), and withdrawals equal to the 2003 permitted rates from all other wells in the modeled area. Salinity changes shown are after 25 years of simulation using the ending results from the 1880-2000 transient simulation as initial conditions. 

Simulation of Redistributed Withdrawals 2001-2025  69
Kipapa

Waiawa

Waimalu

Halawa

158o10' 158o00' 157o50'

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0

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H

H

Pearl City III (increase 

withdrawal by 2.83 Mgal/d)

Halawa Shaft (reduce 

withdrawal by 2.83 Mgal/d)

SCENARIO 2

Kipapa

Waiawa

Waimalu

Halawa

VOLCANIC-ROCK AQUIFER (UNCONFINED)COASTAL CONFINING UNIT (CAPROCK) OVERLYING VOLCANIC-ROCK AQUIFERVALLEY-FILL BARRIER INLAND FROM CAPROCKVALLEY-FILL BARRIER BENEATH CAPROCKWAIANAE CONFINING UNIT INLAND FROM CAPROCKWAIANAE CONFINING UNIT BENEATH CAPROCKSEAWARD BOUNDARY BENEATH CAPROCKLINE OF EQUAL CHANGE IN 2-PERCENT SALINITY DEPTH, IN FEET--Interval 10 feet NEGATIVE CHANGE (LOWERING OF 2-PERCENT SALINITY DEPTH)  ZERO CHANGE POSITIVE CHANGE (RISE OF 2-PERCENT SALINITY DEPTH)WELL H

EXPLANATION

Figure 37. Simulated change in 2-percent salinity depth caused by reducing withdrawal from the Halawa Shaft (2354-01) by 2.83 million gallons per day and increasing withdrawal from Pearl City III (2557-03) by the same amount relative to the 2003 permitted rates. Salinity changes were determined by comparing two simulations that differ only in the rates of withdrawal from the Halawa Shaft and Pearl City III; the first simulation includes withdrawals equal to the 2003 permitted rates from all wells in the modeled area, and the second simulation includes reduced withdrawal from Halawa Shaft (11.32 to 8.49 million gallons per day), increased withdrawal from Pearl City III (0.5 to 3.33 million gallons per day), and withdrawals equal to the 2003 permitted rates from all other wells in the modeled area. Salinity changes shown are after 25 years of simulation using the ending results from the 1880-2000 transient simulation as initial conditions. 

70 Numerical Simulation of the Effects of Valley-Fill Barriers in the Pearl Harbor Area, Oahu, Hawaii
Kipapa

Waiawa

Waimalu

Halawa

158o10' 158o00' 157o50'

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-30

-20

0

-10

-10

10

10

20

H

H

Kunia III (increase 

withdrawal by 5.66 Mgal/d)

Halawa Shaft (reduce 

withdrawal by 5.66 Mgal/d)

SCENARIO 3

Waiawa

Waimalu

Halawa

Kipapa

VOLCANIC-ROCK AQUIFER (UNCONFINED)COASTAL CONFINING UNIT (CAPROCK) OVERLYING VOLCANIC-ROCK AQUIFERVALLEY-FILL BARRIER INLAND FROM CAPROCKVALLEY-FILL BARRIER BENEATH CAPROCKWAIANAE CONFINING UNIT INLAND FROM CAPROCKWAIANAE CONFINING UNIT BENEATH CAPROCKSEAWARD BOUNDARY BENEATH CAPROCKLINE OF EQUAL CHANGE IN 2-PERCENT SALINITY DEPTH, IN FEET--Interval 10 feet NEGATIVE CHANGE (LOWERING OF 2-PERCENT SALINITY DEPTH)  ZERO CHANGE POSITIVE CHANGE (RISE OF 2-PERCENT SALINITY DEPTH)WELL H

EXPLANATION

Figure 38. Simulated change in 2-percent salinity depth caused by reducing withdrawal from the Halawa Shaft (2354-01) by 5.66 million gallons per day and increasing withdrawal from Kunia III (2401-04) by the same amount relative to the 2003 permitted rates. Salinity changes were determined by comparing two simulations that differ only in the rates of withdrawal from the Halawa Shaft and Kunia III; the first simulation includes withdrawals equal to the 2003 permitted rates from all wells in the modeled area, and the second simulation includes reduced withdrawal from Halawa Shaft (11.32 to 5.66 million gallons per day), increased withdrawal from Kunia III (1.5 to 7.16 million gallons per day), and withdrawals equal to the 2003 permitted rates from all other wells in the modeled area. Salinity changes shown are after 25 years of simulation using the ending results from the 1880-2000 transient simulation as initial conditions. 

Simulation of Redistributed Withdrawals 2001-2025  71
Kipapa

Waiawa

Waimalu

Halawa

158o10' 158o00' 157o50'

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5

5

10

15

20

25

15

5

5

-5

-10

H

H

Kunia III (increase 

withdrawal by 5.66 Mgal/d)

Halawa Shaft (reduce 

withdrawal by 5.66 Mgal/d)

SCENARIO 3

VOLCANIC-ROCK AQUIFER (UNCONFINED)COASTAL CONFINING UNIT (CAPROCK) OVERLYING VOLCANIC-ROCK AQUIFERVALLEY-FILL BARRIER INLAND FROM CAPROCKVALLEY-FILL BARRIER BENEATH CAPROCKWAIANAE CONFINING UNIT INLAND FROM CAPROCKWAIANAE CONFINING UNIT BENEATH CAPROCKSEAWARD BOUNDARY BENEATH CAPROCKLINE OF EQUAL CHANGE IN 50-PERCENT SALINITY DEPTH, IN FEET--Interval 10 feet NEGATIVE CHANGE (LOWERING OF 50-PERCENT SALINITY DEPTH)  ZERO CHANGE POSITIVE CHANGE (RISE OF 50-PERCENT SALINITY DEPTH)WELL H

EXPLANATION

Figure 39. Simulated change in 50-percent salinity depth caused by reducing withdrawal from the Halawa Shaft (2354-01) by 5.66 million gallons per day and increasing withdrawal from Kunia III (2401-04) by the same amount relative to the 2003 permitted rates. Salinity changes were determined by comparing two simulations that differ only in the rates of withdrawal from the Halawa Shaft and Kunia III; the first simulation includes withdrawals equal to the 2003 permitted rates from all wells in the modeled area, and the second simulation includes reduced withdrawal from Halawa Shaft (11.32 to 5.66 million gallons per day), increased withdrawal from Kunia III (1.5 to 7.16 million gallons per day), and withdrawals equal to the 2003 permitted rates from all other wells in the modeled area. Salinity changes shown are after 25 years of simulation using the ending results from the 1880-2000 transient simulation as initial conditions. 

72  Numerical Simulation of the Effects of Valley-Fill Barriers in the Pearl Harbor Area, Oahu, Hawaii
Kipapa

Waiawa

Waimalu

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158o10' 158o00' 157o50'

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H

H

Pearl City III (increase 

withdrawal by 5.88 Mgal/d)

Kalauao (reduce 

withdrawal by 5.88 Mgal/d)

SCENARIO 4

Kipapa

Waiawa

Waimalu

Halawa

VOLCANIC-ROCK AQUIFER (UNCONFINED)COASTAL CONFINING UNIT (CAPROCK) OVERLYING VOLCANIC-ROCK AQUIFERVALLEY-FILL BARRIER INLAND FROM CAPROCKVALLEY-FILL BARRIER BENEATH CAPROCKWAIANAE CONFINING UNIT INLAND FROM CAPROCKWAIANAE CONFINING UNIT BENEATH CAPROCKSEAWARD BOUNDARY BENEATH CAPROCKLINE OF EQUAL CHANGE IN 2-PERCENT SALINITY DEPTH, IN FEET--Interval 10 feet NEGATIVE CHANGE (LOWERING OF 2-PERCENT SALINITY DEPTH)  ZERO CHANGE POSITIVE CHANGE (RISE OF 2-PERCENT SALINITY DEPTH)WELL H

EXPLANATION

Figure 40. Simulated change in 2-percent salinity depth caused by reducing withdrawal from the Kalauao Wells (2355-09 to -14) by 5.88 million gallons per day and increasing withdrawal from Pearl City III (2557-03) by the same amount relative to the 2003 permitted rates. Salinity changes were determined by comparing two simulations that differ only in the rates of withdrawal from the Kalauao Wells and Pearl City III; the first simulation includes withdrawals equal to the 2003 permitted rates from all wells in the modeled area, and the second simulation includes reduced withdrawal from Kalauao (11.75 to 5.88 million gallons per day), increased withdrawal from Pearl City III (0.5 to 6.38 million gallons per day), and withdrawals equal to the 2003 permitted rates from all other wells in the modeled area. Salinity changes shown are after 25 years of simulation using the ending results from the 1880-2000 transient simulation as initial conditions. 

Simulation of Redistributed Withdrawals 2001-2025  73
Kipapa

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H

H

Pearl City III (increase 

withdrawal by 2.94 Mgal/d)

Kalauao (reduce 

withdrawal by 2.94 Mgal/d)

SCENARIO 5

Kipapa

Waiawa

Waimalu

Halawa

VOLCANIC-ROCK AQUIFER (UNCONFINED)COASTAL CONFINING UNIT (CAPROCK) OVERLYING VOLCANIC-ROCK AQUIFERVALLEY-FILL BARRIER INLAND FROM CAPROCKVALLEY-FILL BARRIER BENEATH CAPROCKWAIANAE CONFINING UNIT INLAND FROM CAPROCKWAIANAE CONFINING UNIT BENEATH CAPROCKSEAWARD BOUNDARY BENEATH CAPROCKLINE OF EQUAL CHANGE IN 2-PERCENT SALINITY DEPTH, IN FEET--Interval 10 feet NEGATIVE CHANGE (LOWERING OF 2-PERCENT SALINITY DEPTH)  ZERO CHANGE POSITIVE CHANGE (RISE OF 2-PERCENT SALINITY DEPTH)WELL H

EXPLANATION

Figure 41. Simulated change in 2-percent salinity depth caused by reducing withdrawal from the Kalauao Wells (2355-09 to -14) by 2.94 million gallons per day and increasing withdrawal from Pearl City III (2557-03) by the same amount relative to the 2003 permitted rates. Salinity changes were determined by comparing two simulations that differ only in the rates of withdrawal from the Kalauao Wells and Pearl City III; the first simulation includes withdrawals equal to the 2003 permitted rates from all wells in the modeled area, and the second simulation includes reduced withdrawal from Kalauao (11.75 to 8.81 million gallons per day), increased withdrawal from Pearl City III (0.5 to 3.44 million gallons per day), and withdrawals equal to the 2003 permitted rates from all other wells in the modeled area. Salinity changes shown are after 25 years of simulation using the ending results from the 1880-2000 transient simulation as initial conditions. 

74  Numerical Simulation of the Effects of Valley-Fill Barriers in the Pearl Harbor Area, Oahu, Hawaii
10 ft, and near Pearl City III the 2-percent salinity depth shallows by about 10 ft. In scenario 5, the change in 50-percent 

salinity depth caused by the redistributed withdrawal is less 

than 10 ft. In scenario 5, the reduction in withdrawal from the 

Kalauao Wells is half that simulated in scenario 4. At common 

locations, the simulated change in 2-percent salinity depth in 

scenario 5 also is about half the magnitude of the simulated 

change in scenario 4. 

Scenario 6

In scenario 6, withdrawal from the Kalauao Wells (2355-

09 to -14) was reduced by 5.88 Mgal/d and withdrawal from 

Kunia III (2401-04) was increased by 5.88 Mgal/d relative 

to the 2003 permitted rates. Model results indicate that the 

2-percent salinity depth does not change (0-ft line of equal 

change in 2-percent salinity depth) along a line that runs from 

Pearl Harbor to the inland extent of the model, a third of the 

way from the Kalauao Wells to Kunia III (fig. 42). Relative to 

scenario 4, the 0-ft line of equal change in 2-percent salinity 

depth simulated in scenario 6 extends farther westward, indicating a larger zone where freshwater thickness increases in 

scenario 6 relative to scenario 4. Thus, by redistributing 5.88 

Mgal/d from Pearl City III (scenario 4) to Kunia III (scenario 

6), located farther to the west, the zone where freshwater 

thickness increases expands westward. Near the Kalauao Wells 

the 2-percent salinity depth deepens by about 30 ft, and near 

Kunia III the 2-percent salinity depth shallows by about 35 ft. 

In scenario 6, shallowing of the 50-percent salinity depth 

is greatest to the southwest of Kunia III, and is as much as 

45 ft (fig. 43). Shallowing of the 50-percent salinity depth is 

enhanced by the presence of the low-permeability Waianae 

confining unit, which is represented in the model as a vertical 

barrier.

Scenarios 3 and 6 are similar in the amount of redistributed withdrawal to Kunia III (5.66 Mgal/d in scenario 3 and 

5.88 Mgal/d in scenario 6). The size and shape of the zones 

in which freshwater thickness increases also are similar in 

scenarios 3 and 6. In general, however, the deepening of the 

2-percent salinity depth is greater in scenario 3 relative to 

scenario 6. Within the simulated zones in which freshwater 

thickness decreases, shallowing of the 2-percent salinity depth 

is slightly greater in scenario 6 relative to scenario 3 because 

simulated withdrawal from Kunia III is slightly higher in 

scenario 6.

Scenario 7

In scenario 7, withdrawal from Halawa Shaft (2354-01) 

was reduced by 2.83 Mgal/d, withdrawal from the Kalauao 

Wells (2355-09 to -14) was reduced by 2.94 Mgal/d, and 

withdrawal from Kunia III (2401-04) was increased by 5.77 

Mgal/d relative to the 2003 permitted rates. Model results 

indicate that the 2-percent salinity depth does not change (0-ft 

line of equal change in 2-percent salinity depth) along a line 

that runs from Pearl Harbor to the inland extent of the model, 

about midway between Halawa Shaft and Kunia III (fig. 44). 

The 0-ft line of equal change in 2-percent salinity depth simulated in scenario 7 is similar to that of scenario 3. In scenario 

7, shallowing of the 50-percent salinity depth is greatest to the 

southwest of Kunia III, and is as much as 45 ft (fig. 45). 

Scenarios 3 and 7 are similar in the amount of redistributed withdrawal to Kunia III (5.66 Mgal/d in scenario 3 and 

5.77 Mgal/d in scenario 7). The size and shape of the zones 

in which freshwater thickness increases also are similar in 

scenarios 3 and 7. In general, however, the deepening of the 

2-percent salinity depth is greater in scenario 3 relative to 

scenario 7. Within the simulated zones in which freshwater 

thickness decreases, shallowing of the 2-percent salinity depth 

is slightly greater in scenario 7 relative to scenario 3 because 

simulated withdrawal from Kunia III is slightly higher in 

scenario 7.

Summary of Effects of Redistributing 

Withdrawals

Results of the simulation of seven scenarios of redistributed withdrawal indicate the following: (1) redistributing withdrawal from Halawa Shaft (2354-01) or the Kalauao 

Wells (2355-09 to -14), near the eastern part of the Waimalu 

management system, to Pearl City III (2557-03), near the 

western part of the Waimalu management system, results in a 

thickening of the freshwater zone east of Waimalu Stream and 

a thinning of the freshwater zone west of Waimalu Stream; 

(2) in general, redistributing withdrawal from Halawa Shaft to 

Pearl City III results in greater thickening of the freshwater 

in the eastern part of the Waimalu management system relative to redistributing an equal amount of withdrawal from the 

Kalauao Wells to Pearl City III; (3) redistributing withdrawal 

from Halawa Shaft or the Kalauao Wells, near the eastern part 

of the Waimalu management system, to Kunia III (2557-03), 

near the western part of the Waipahu-Waiawa management 

system, results in a thickening of the freshwater zone throughout most of the Waimalu management system and a thinning 

of the freshwater zone in the Waipahu-Waiawa management 

system; (4) in general, redistributing withdrawal from Halawa 

Shaft to Kunia III results in greater thickening of the freshwater in the eastern part of the Waimalu management system 

relative to redistributing an equal amount of withdrawal from 

the Kalauao Wells to Kunia III; (5) the extent of freshwater 

thickening in the eastern part of the Waimalu management 

system caused by reducing withdrawal from the area is 

directly related to the amount of the reduction; (6) the zone 

where freshwater thickens in response to reducing withdrawal 

from a well is greatest downgradient from the well, between 

the well and the shore; and (7) valley-fill barriers can potentially reduce the zone where freshwater thickness increases in 

response to a reduction of withdrawal. 

Simulation of Redistributed Withdrawals 2001-2025  75
Kipapa

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Waimalu

Halawa

158o10' 158o00' 157o50'

21o30'21o20'

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0

-10

-10

0

-20

10

10

20

30

H

H

Kunia III (increase 

withdrawal by 5.88 Mgal/d)

Kalauao (reduce 

withdrawal by 5.88 Mgal/d)

SCENARIO 6

Kipapa

Waiawa

Waimalu

Halawa

VOLCANIC-ROCK AQUIFER (UNCONFINED)COASTAL CONFINING UNIT (CAPROCK) OVERLYING VOLCANIC-ROCK AQUIFERVALLEY-FILL BARRIER INLAND FROM CAPROCKVALLEY-FILL BARRIER BENEATH CAPROCKWAIANAE CONFINING UNIT INLAND FROM CAPROCKWAIANAE CONFINING UNIT BENEATH CAPROCKSEAWARD BOUNDARY BENEATH CAPROCKLINE OF EQUAL CHANGE IN 2-PERCENT SALINITY DEPTH, IN FEET--Interval 10 feet NEGATIVE CHANGE (LOWERING OF 2-PERCENT SALINITY DEPTH)  ZERO CHANGE POSITIVE CHANGE (RISE OF 2-PERCENT SALINITY DEPTH)WELL H

EXPLANATION

Figure 42. Simulated change in 2-percent salinity depth caused by reducing withdrawal from the Kalauao Wells (2355-09 to -14) by 5.88 million gallons per day and increasing withdrawal from Kunia III (2401-04) by the same amount relative to the 2003 permitted rates. Salinity changes were determined by comparing two simulations that differ only in the rates of withdrawal from the Kalauao Wells and Kunia III; the first simulation includes withdrawals equal to the 2003 permitted rates from all wells in the modeled area, and the second simulation includes reduced withdrawal from Kalauao (11.75 to 5.88 million gallons per day), increased withdrawal from Kunia III (1.5 to 7.38 million gallons per day), and withdrawals equal to the 2003 permitted rates from all other wells in the modeled area. Salinity changes shown are after 25 years of simulation using the ending results from the 1880-2000 transient simulation as initial conditions. 

76  Numerical Simulation of the Effects of Valley-Fill Barriers in the Pearl Harbor Area, Oahu, Hawaii
Kipapa

Waiawa

Waimalu

Halawa

158o10' 158o00' 157o50'

21o30'21o20'

Topographic

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Area of

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0

0

-5

10

5

5

5

10

15

20

25

H

H

Kunia III (increase 

withdrawal by 5.88 Mgal/d)

Kalauao (reduce 

withdrawal by 5.88 Mgal/d)

SCENARIO 6

VOLCANIC-ROCK AQUIFER (UNCONFINED)COASTAL CONFINING UNIT (CAPROCK) OVERLYING VOLCANIC-ROCK AQUIFERVALLEY-FILL BARRIER INLAND FROM CAPROCKVALLEY-FILL BARRIER BENEATH CAPROCKWAIANAE CONFINING UNIT INLAND FROM CAPROCKWAIANAE CONFINING UNIT BENEATH CAPROCKSEAWARD BOUNDARY BENEATH CAPROCKLINE OF EQUAL CHANGE IN 50-PERCENT SALINITY DEPTH, IN FEET--Interval 10 feet NEGATIVE CHANGE (LOWERING OF 50-PERCENT SALINITY DEPTH)  ZERO CHANGE POSITIVE CHANGE (RISE OF 50-PERCENT SALINITY DEPTH)WELL H

EXPLANATION

Figure 43. Simulated change in 50-percent salinity depth caused by reducing withdrawal from the Kalauao Wells (2355-09 to -14) by 5.88 million gallons per day and increasing withdrawal from Kunia III (2401-04) by the same amount relative to the 2003 permitted rates. Salinity changes were determined by comparing two simulations that differ only in the rates of withdrawal from the Kalauao Wells and Kunia III; the first simulation includes withdrawals equal to the 2003 permitted rates from all wells in the modeled area, and the second simulation includes reduced withdrawal from Kalauao (11.75 to 5.88 million gallons per day), increased withdrawal from Kunia III (1.5 to 7.38 million gallons per day), and withdrawals equal to the 2003 permitted rates from all other wells in the modeled area. Salinity changes shown are after 25 years of simulation using the ending results from the 1880-2000 transient simulation as initial conditions. 

Simulation of Redistributed Withdrawals 2001-2025  77
Kipapa

Waiawa

Waimalu

Halawa

158o10' 158o00' 157o50'

21o30'21o20'

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PacificOcean

Area of

Map

Oahu

0

0

-10

-20

-10

0

10

10

20

H

H

H

Kunia III (increase 

withdrawal by 5.77 Mgal/d)

Kalauao (reduce 

withdrawal by 2.94 Mgal/d)

Halawa Shaft (reduce 

withdrawal by 2.83 Mgal/d)

SCENARIO 7

Waiawa

Waimalu

Halawa

Kipapa

VOLCANIC-ROCK AQUIFER (UNCONFINED)COASTAL CONFINING UNIT (CAPROCK) OVERLYING VOLCANIC-ROCK AQUIFERVALLEY-FILL BARRIER INLAND FROM CAPROCKVALLEY-FILL BARRIER BENEATH CAPROCKWAIANAE CONFINING UNIT INLAND FROM CAPROCKWAIANAE CONFINING UNIT BENEATH CAPROCKSEAWARD BOUNDARY BENEATH CAPROCKLINE OF EQUAL CHANGE IN 2-PERCENT SALINITY DEPTH, IN FEET--Interval 10 feet NEGATIVE CHANGE (LOWERING OF 2-PERCENT SALINITY DEPTH)  ZERO CHANGE POSITIVE CHANGE (RISE OF 2-PERCENT SALINITY DEPTH)WELL H

EXPLANATION

Figure 44. Simulated change in 2-percent salinity depth caused by reducing withdrawals from the Halawa Shaft (2354-01) by 2.83 million gallons per day and the Kalauao Wells (2355-09 to -14) by 2.94 million gallons per day and increasing withdrawal from Kunia III (2401-04) by 5.77 million gallons per day relative to the 2003 permitted rates. Salinity changes were determined by comparing two simulations that differ only in the rates of withdrawal from the Halawa Shaft, Kalauao Wells, and Kunia III; the first simulation includes withdrawals equal to the 2003 permitted rates from all wells in the modeled area, and the second simulation includes reduced withdrawal from Halawa Shaft (11.32 to 8.49 million gallons per day), reduced withdrawal from Kalauao (11.75 to 8.81 million gallons per day), increased withdrawal from Kunia III (1.5 to 7.27 million gallons per day), and withdrawals equal to the 2003 permitted rates from all other wells in the modeled area. Salinity changes shown are after 25 years of simulation using the ending results from the 1880-2000 transient simulation as initial conditions. 

78  Numerical Simulation of the Effects of Valley-Fill Barriers in the Pearl Harbor Area, Oahu, Hawaii
Kipapa

Waiawa

Waimalu

Halawa

158o10' 158o00' 157o50'

21o30'21o20'

Topographic

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Area of

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0

0

-5

-5

5

5

10

15

20

5

25

5

H

H

H

Kunia III (increase 

withdrawal by 5.77 Mgal/d)

Kalauao (reduce 

withdrawal by 2.94 Mgal/d)

Halawa Shaft (reduce 

withdrawal by 2.83 Mgal/d)

SCENARIO 7

VOLCANIC-ROCK AQUIFER (UNCONFINED)COASTAL CONFINING UNIT (CAPROCK) OVERLYING VOLCANIC-ROCK AQUIFERVALLEY-FILL BARRIER INLAND FROM CAPROCKVALLEY-FILL BARRIER BENEATH CAPROCKWAIANAE CONFINING UNIT INLAND FROM CAPROCKWAIANAE CONFINING UNIT BENEATH CAPROCKSEAWARD BOUNDARY BENEATH CAPROCKLINE OF EQUAL CHANGE IN 50-PERCENT SALINITY DEPTH, IN FEET--Interval 10 feet NEGATIVE CHANGE (LOWERING OF 50-PERCENT SALINITY DEPTH)  ZERO CHANGE POSITIVE CHANGE (RISE OF 50-PERCENT SALINITY DEPTH)WELL H

EXPLANATION

Figure 45. Simulated change in 50-percent salinity depth caused by reducing withdrawals from the Halawa Shaft (2354-01) by 2.83 million gallons per day and the Kalauao Wells (2355-09 to -14) by 2.94 million gallons per day and increasing withdrawal from Kunia III (2401-04) by 5.77 million gallons per day relative to the 2003 permitted rates. Salinity changes were determined by comparing two simulations that differ only in the rates of withdrawal from the Halawa Shaft, Kalauao Wells, and Kunia III; the first simulation includes withdrawals equal to the 2003 permitted rates from all wells in the modeled area, and the second simulation includes reduced withdrawal from Halawa Shaft (11.32 to 8.49 million gallons per day), reduced withdrawal from Kalauao (11.75 to 8.81 million gallons per day), increased withdrawal from Kunia III (1.5 to 7.27 million gallons per day), and withdrawals equal to the 2003 permitted rates from all other wells in the modeled area. Salinity changes shown are after 25 years of simulation using the ending results from the 1880-2000 transient simulation as initial conditions. 

Simulation of Redistributed Withdrawals 2001-2025  79
Model Limitations

The numerical model developed for this study simulates 

water levels and salinity on a regional scale and may not accurately predict either the pumping water level at an individual 

well or the salinity of water pumped from that well. Salinity of 

water pumped from a well may be controlled by local heterogeneities in the aquifer that are not represented in the model, 

and the level of model discretization affects the numerical 

accuracy with which transport mechanisms are simulated. The 

model has several other limitations for predictive purposes 

because of the various assumptions used and possible uncertainties in input data. These limitations are discussed below.

Differences between measured and simulated water levels 

and salinity profiles are greater in some areas than others, 

which may reflect uncertainties in the recharge or withdrawal 

estimates, boundary conditions, assigned parameter values in 

the model, or representations of the different hydrogeological 

features in the model. Recharge estimates in Hawaii generally are based on water-budget computations that could be 

improved with a better understanding of the spatial distributions of rainfall, evapotranspiration, runoff, and land-cover 

characteristics. Additional studies that could reduce uncertainties include: (1) directly measuring recharge using field 

lysimeters, (2) measuring changes in soil moisture below the 

plant root zone, (3) quantifying increases in the chloride concentration of infiltrating water caused by evapotranspiration, 

(4) measuring ground-water discharge with offshore seepage meters, and (5) developing an integrated surface-water/

ground-water model. Improved recharge estimates in the study 

area will lead to improved estimates for parameter values in 

the numerical ground-water model and greater confidence in 

model results. Withdrawals represented in the model were 

based on available information. Unreported withdrawals and 

uncertainties in reported withdrawals that cannot be quantified 

also affect the accuracy of model results. 

For this study, no-flow boundaries were assigned in the 

east and west, which precludes movement of ground water 

across these boundaries. Although some flow likely takes 

place across these boundaries, the amount cannot be quantified 

without expanding the modeled area. 

The distributions of parameter values assigned in the 

model were kept simple to avoid creating an overly complex 

model that could not be justified on the basis of existing information. Heterogeneity in the ground-water system likely exists 

but is currently poorly understood. Values assigned to model 

parameters generally were based on existing estimates. However, some of these parameter values may be poorly known. 

Improved estimates of the distribution of hydraulic characteristics in the study area can be obtained using controlled aquifer 

tests as well as by careful monitoring of pumping and waterlevel conditions throughout the aquifer. Accurate pumping 

data in conjunction with water-level drawdown and recovery 

data can be used for calibration of a numerical ground-water 

flow model, particularly during periods when recharge does 

not vary. 

The geometrical representation of the valley-fill barriers, 

caprock, and Waianae confining unit also were kept simple 

for the model. Because of uncertainty in the configuration of 

the valley-fill barriers, different configurations were tested in 

a sensitivity analysis. The sensitivity analysis indicated that 

model results could be improved in some places by adjusting 

valley-fill configurations. Our understanding of the geometry of the valley-fill barriers can be improved using surface 

geophysical techniques in conjunction with drilling additional 

monitor wells within the valleys (see for example R.M. Towill 

Corporation, 1978). In addition, careful monitoring of water 

levels on opposite sides of valley-fill barriers can provide 

insight as to the hydrologic effectiveness of the barriers.

For this study, the coastal caprock was represented as a 

homogeneous zone of low permeability except near the top 

of the caprock, where a high-permeability limestone unit was 

modeled. Other high-permeability zones likely exist in the 

caprock but they are poorly understood and were not represented in the model for this study. The Waianae confining unit 

was represented in the model as a vertical unit located near 

the sea-level contact between Waianae Volcanics and Koolau 

Basalt. Although the Waianae confining unit may dip about 

10o away from the Waianae Volcano toward the east, it was 

represented in the model as a vertical unit because of uncertainty in the location of the confining unit eastward of the sealevel contact between Waianae Volcanics and Koolau Basalt. 

Flow of water at the vertical seaward boundary of the 

model, below the caprock, was controlled by the hydraulic 

conductivity of the row of elements at the boundary. The ease 

with which saltwater enters the model at this boundary has an 

effect on the transient response of the system to changes in 

recharge and withdrawals. Extension of the model farther offshore may reduce the sensitivity of the model to the assigned 

hydraulic conductivity at the seaward boundary. 

Two modeling artifices were incorporated to improve 

numerical stability in the model: (1) shallow zones (top two 

elements at most) of high dispersivity were created near zones 

of discharge, and (2) withdrawal from selected Maui-type 

shafts with infiltration tunnels was represented at more than 

one model node. These modeling artifices could be relaxed in 

future models that have finer discretization, although neither 

of these artifices likely affect the overall conclusions of this 

study. 

Confidence in model results can be improved by addressing the limitations described in this section. In particular, 

improved estimates of recharge and the distribution of model 

parameters likely will lead to better model reliability. 

Summary

The aquifer in the Pearl Harbor area of southern Oahu 

is the most heavily used aquifer in the State of Hawaii. For 

80 Numerical Simulation of the Effects of Valley-Fill Barriers in the Pearl Harbor Area, Oahu, Hawaii
management purposes, the State Commission on Water 

Resource Management has divided the Pearl Harbor area into 

three hydrologically connected aquifer-management systems. 

From west to east, these management systems are the EwaKunia system, the Waipahu-Waiawa system, and the Waimalu 

system. During 2001, reported withdrawals from the Waimalu 

management system averaged 46.5 Mgal/d. Ground-water 

withdrawal from the Waimalu management system is slightly 

higher than the State’s sustainable-yield estimate of 45 Mgal/d 

for the area. This has led to concern regarding saltwater intrusion associated with long-term withdrawals from the Waimalu 

management system. 

In the Waimalu management system, ground-water flow 

may be influenced by valley-fill barriers associated with 

existing stream valleys. Valley-fill barriers are formed by 

low-permeability valley-fill deposits and weathered volcanic 

rocks beneath those deposits that impede ground-water movement. The State’s sustainable-yield estimate for the Waimalu 

management system does not account for the hydrologic 

effects of these possible barriers.

In cooperation with the City and County of Honolulu 

Board of Water Supply (BWS), the U.S. Geological Survey 

(USGS) undertook an investigation to evaluate the possible 

hydrologic effects of valley-fill barriers in the Pearl Harbor 

area. The objectives of this study were to (1) obtain a better 

understanding of the hydrologic effects of valley-fill barriers 

in the Pearl Harbor area, (2) determine the possible effects of 

valley-fill barriers on water levels and salinity in the Pearl Harbor area, and (3) estimate the effects of redistributing existing 

withdrawals on the freshwater resource.

To date, only limited information has been published on 

valley-fill barriers in the Pearl Harbor area. As part of this 

study, water levels from wells on opposite sides of Waiawa 

Stream valley were measured to determine if water-level 

recovery associated with shutting off a large-capacity production well could be measured. The Waiawa Shaft (well 

2558-10), which is located on the west side of Waiawa Stream 

valley, was shut off for a period of about 2 days. During the 

week prior to the shut-off, withdrawal from Waiawa Shaft 

was steady at about 10 Mgal/d. During the 2-day period 

when Waiawa Shaft was shut off, water levels on each side 

of Waiawa Stream valley appeared to recover, indicating that 

Waiawa Stream valley is not a totally effective hydrologic barrier in the vicinity of Waiawa Shaft. 

A three-dimensional numerical ground-water model 

capable of simulating density-dependent solute transport was 

developed as part of this study. The model used published 

estimates for most of the permeability, storage, and dispersivity values. Simulated water levels and salinity profiles generally were in agreement with measured water levels and salinity 

profiles from representative wells in the modeled area. 

Simulated water levels during some periods were a few 

feet too high in the eastern part of the Koolau Basalt aquifer 

and a few feet too low in the western part. Furthermore, the 

model underestimates, by about 4 ft, the reported predevelopment head of 32 ft above mean sea level near the southwestern 

part of the Koolau Basalt aquifer. Some of the discrepancy 

between measured and simulated water levels can be attributed to uncertainties in the estimated distribution of hydraulic 

properties in the model. In addition, some of the discrepancy 

may be related to factors including: (1) the reported predevelopment head may be from a period with climatic conditions 

that are not representative of long-term conditions, (2) the estimated distributions of recharge for different time periods are 

uncertain, (3) the reported ground-water withdrawal information may be inaccurate, (4) the hydraulic characteristics of the 

caprock may have changed over time because of the drilling 

of numerous artesian wells, which flowed freely at the surface 

and may have leaked in the subsurface. 

Model sensitivity tests of valley-fill barrier configuration indicated that simulated water levels and salinity can be 

affected by the depth and length of the simulated valley-fill 

barriers. Deepening the Waiawa valley-fill barrier to 660 ft 

below mean sea level and extending it inland and seaward 

resulted in a redistribution of ground-water flow and simulated 

water-level changes of as much as a foot relative to the basecase valley-fill barriers. Deepening the Waiawa valley-fill barrier to 660 ft below mean sea level generally resulted in deeper 

simulated salinity profiles west of the Waiawa valley-fill 

barrier by as much as a few tens of feet in some places relative 

to the base case for common sites and times. 

The model constructed for this study was used to simulate the hydrologic effects of redistributing withdrawals in 

the Pearl Harbor area by reducing withdrawals in the eastern 

part of the Waimalu area and increasing withdrawals farther 

to the west by an equal amount. Simulation results from seven 

scenarios of redistributed withdrawal indicate the following: 

(1) redistributing withdrawal from Halawa Shaft (2354-01) or 

the Kalauao Wells (2355-09 to -14), near the eastern part of 

the Waimalu management system, to Pearl City III (2557-03), 

near the western part of the Waimalu management system, 

results in a thickening of the freshwater zone east of Waimalu 

Stream and a thinning of the freshwater zone west of Waimalu 

Stream; (2) in general, redistributing withdrawal from Halawa 

Shaft to Pearl City III results in greater thickening of the 

freshwater in the eastern part of the Waimalu management system relative to redistributing an equal amount of withdrawal 

from the Kalauao Wells to Pearl City III; (3) redistributing 

withdrawal from Halawa Shaft or the Kalauao Wells, near the 

eastern part of the Waimalu management system, to Kunia 

III (2557-03), near the western part of the Waipahu-Waiawa 

management system, results in a thickening of the freshwater 

zone throughout most of the Waimalu management system 

and a thinning of the freshwater zone in the Waipahu-Waiawa 

management system; (4) in general, redistributing withdrawal 

from Halawa Shaft to Kunia III results in greater thickening 

of the freshwater in the eastern part of the Waimalu management system relative to redistributing an equal amount of 

withdrawal from the Kalauao Wells to Kunia III; (5) the extent 

of freshwater thickening in the eastern part of the Waimalu 

management system caused by reducing withdrawal from 

the area is directly related to the amount of the reduction; (6) 

Summary  81
the zone where freshwater thickens in response to reducing 

withdrawal from a well is greatest downgradient from the 

well, between the well and the shore; and (7) valley-fill barriers can potentially reduce the zone where freshwater thickness 

changes in response to a reduction of withdrawal. 

The numerical model developed for this study simulates 

water levels and salinity on a regional scale and may not accurately predict either the pumping water level at an individual 

well or the salinity of water pumped from that well. Salinity of water pumped from a well may be controlled by local 

heterogeneities in the aquifer that are not represented in the 

model. The model has several other limitations for predictive 

purposes because of the various assumptions used and possible 

uncertainties in input data. Model reliability can be improved 

as understanding of ground-water recharge, the distribution 

of model parameter values, and the geometry of the valley-fill 

barriers improves. 

Recharge estimates in Hawaii generally are based on 

water-budget computations that could be improved with a better understanding of the spatial distributions of rainfall, evapotranspiration, runoff, and land-cover characteristics. Additional studies that could lead to improved recharge estimates 

include, (1) directly measuring recharge using field lysimeters, 

(2) measuring changes in soil moisture below the plant root 

zone, (3) quantifying increases in the chloride concentration of 

infiltrating water caused by evapotranspiration, (4) measuring 

ground-water discharge with offshore seepage meters, and (5) 

developing an integrated surface-water/ground-water model.

Improved estimates of the distribution of hydraulic characteristics in the study area can be obtained using controlled 

aquifer tests as well as by careful monitoring of pumping 

and water-level conditions throughout the aquifer. Accurate 

pumping data in conjunction with water-level drawdown 

and recovery data can be used for calibration of a numerical 

ground-water flow model, particularly during periods when 

recharge does not vary. 

Our understanding of the geometry of the valley-fill barriers could be improved using surface geophysical techniques 

in conjunction with drilling additional monitor wells within 

the valleys. In addition, careful monitoring of water levels on 

opposite sides of a valley could provide insight as to the effectiveness of the valley-fill barrier.

References Cited

Andrews, J.E., and Bainbridge, Charles, 1972, Submarine 

canyons off eastern Oahu: Pacific Science, v. XXVI, no. 1, 

p. 108-113.

Bauer, Glenn, 1996, Reevaluation of the ground-water 

resources and sustainable yield of the Ewa caprock aquifer: 

final report, State of Hawaii, Department of Land and Natural Resources, Commission on Water Resource Management, 57 p.

Blumenstock, D.I., and Price, Saul, 1967, Climate of Hawaii, 

in Climates of the States, no. 60-51, Climatography of the 

United States: U.S. Department of Commerce. 

Camp Dresser and McKee, 1994, Groundwater modeling 

study--responses to CWRM comments on preliminary modeling, Ewa Marina project: Prepared for HASEKO (EWA) 

Inc, Honolulu, Hawaii, May 1994, 68 p. plus appendixes.

Chapman, Sydney, and Lindzen, R.S., 1970, Atmospheric 

tides, D. Reidel Publishing Company, Dordrecht, Holland, 

200 p.

Dale, R.H., 1967, Land use and its effect on the basal water 

supply Pearl Harbor area, Oahu, Hawaii, 1931-65: U.S. 

Geological Survey Hydrologic Investigations Atlas HA-267, 

2 sheets.

Dale, R.H., 1978, A ground-water inventory of the Waialua 

basal-water body, island of Oahu, Hawaii: U.S. Geological 

Survey Open-File Report 78-24, 71 p.

Dale, R.H., and Ewart, C.J., 1971, Ground-water status report, 

1910-70, Pearl Harbor area: U.S. Geological Survey OpenFile Report. 

Doell, R.R., and Dalrymple, G.B., 1973, Potassium-argon ages 

and paleomagnetism of the Waianae and Koolau Volcanic 

Series, Oahu, Hawaii: Geological Society of America Bulletin, v. 84, no. 4, p. 1,217-1,241.

Ekern, P.C., and Chang, J-H., 1985, Pan evaporation: State of 

Hawaiʻi, 1894-1983: State of Hawaii, Department of Land 

and Natural Resources, Report R74, 172 p. 

Essaid, H.I., 1990, The computer model SHARP, a quasithree-dimensional finite-difference model to simulate freshwater and saltwater flow in layered coastal aquifer systems: 

U.S. Geological Survey Water-Resources Investigations 

Report 90-4130, 181 p.

Eyre, P.R., 1983, Investigation of Waikele well no. 2401-01, 

Oahu, Hawaii: pumping test, well logs and water quality: 

U.S. Geological Survey Water-Resources Investigations 

Report 83-4089, 38 p.

Freeze, R.A., and Cherry, J.A., 1979, Groundwater: Englewood Cliffs, N.J., Prentice-Hall, Inc., 604 p.

Fukunaga, L.K., 1978, Some agroclimatic, economic, ecological and site considerations that condition the practice of drip 

irrigation in Hawaii’s sugar industry, M.A. thesis, University of Hawaii, 181 p.

Furumoto, A.S., Campbell, J.F., and Hussong, D.M., 1970, 

Seismic studies of subsurface structure in the Ewa coastal 

plain, Oahu, Hawaii: Pacific Science, v. 24, no. 4, p. 529-

542.

82  Numerical Simulation of the Effects of Valley-Fill Barriers in the Pearl Harbor Area, Oahu, Hawaii
Giambelluca, T.W., 1983, Water balance of the Pearl HarborHonolulu basin, Hawaiʻi, 1946-1975: University of Hawaii 

Water Resources Research Center Technical Report no. 151, 

151 p.

Giambelluca, T.W., 1986, Land-use effects on the water balance of a tropical island: National Geographic Research, v. 

2, no. 2, p. 125-151.

Giambelluca, T.W., Lau, L.S., Fok, Y.S., and Schroeder, T.A., 

1984, Rainfall frequency study for Oahu: State of Hawaii, 

Department of Land and Natural Resources, Division of 

Water and Land Development, Report R-73, 232 p. 

Giambelluca, T.W., Nullet, M.A., and Schroeder, T.A., 1986, 

Rainfall atlas of Hawaiʻi: State of Hawaii, Department of 

Land and Natural Resources, Report R76, 267 p. 

Gibson, Warren, 1979, Water-yield relationships under drip 

irrigation: Hawaiian Sugar Technologists 1978 Reports, 37th

Annual Conference, November, 1978, p. 60-63.

Gingerich, S.B., and Oki, D.S., 2000, Ground water in Hawaii: 

U.S. Geological Survey Fact Sheet FS126-00, 6 p. 

Gingerich, S.B., and Voss, C.I., 2005, Three-dimensional variable-density flow simulation of a coastal aquifer in southern 

Oahu, Hawaii, USA: Hydrogeology Journal, v. 13, p. 436-

450.

Gramlich, J.W., Lewis, V.A., and Naughton, J.J., 1971, Potassium-argon dating of Holocene basalts of the Honolulu 

Volcanic Series: Geological Society of America Bulletin, v. 

82, no. 5, p. 1,399-1,404.

Gregory, A.E., III, 1980, Reflection profiling studies of the 

500-meter shelf south of Oahu: Reef development on a midoceanic island, M.S. thesis, University of Hawaii at Manoa, 

65 p.

Guillou, H., Sinton, J., Laj, C., Kissel, C., and Szeremeta, N., 

2000, New K-Ar ages of shield lavas from Waianae Volcano, Oahu, Hawaiian archipelago: Journal of Volcanology 

and Geothermal Research, v. 96, p. 229-242. 

Hall, W.G., 1965, Acres under overhead irrigation—1960-

1965: Hawaiian Sugar Technologists 1965 Reports, 24th

Annual Conference, November, 1965, p. 147-151.

Huber, R.D., and Adams, W.M., 1971, Density logs from 

underground gravity surveys in Hawaii: University of 

Hawaii Water Resources Research Center Technical Report 

no. 45, 39 p.

Hunt, C.D., Jr., 1996, Geohydrology of the island of Oahu, 

Hawaii: U.S. Geological Survey Professional Paper 1412-

B, 54 p.

Ishizaki Kenneth, Burbank, N.C., Jr., and Lau, L.S., 1967, 

Effects of soluble organics on flow through thin cracks 

of basaltic lava: University of Hawaii Water Resources 

Research Center Technical Report no. 16, 56 p.

Izuka, S.K., 1992, Geology and stream infiltration of North 

Halawa Valley, Oahu, Hawaii: U.S. Geological Survey 

Water-Resources Investigations Report 91-4197, 21 p.

Juvik, S.O., and Juvik, J.O., 1998, Atlas of Hawaiʻi, 3rd ed., 

University of Hawaii Press, Honolulu, 333 p.

Klasner, F.L., and Mikami, C.D., 2003, Land use on the island 

of Oahu, Hawaii, 1998: U.S. Geological Survey WaterResources Investigations Report 02-4301, 20 p.

Kunesh, J.F., 1929, Surface, spring and tunnel water investigations, Part IV of Report of the Honolulu Sewer and Water 

Commission to the Legislature of the Territory of Hawaii 

Fifteenth Regular Session, Honolulu, Hawaii, January 1929, 

p. 83-178.

Kunesh, J.F., 1931, Water resources of the City and County of 

Honolulu, Supplement to the report of the Board of Water 

Supply to the Legislature of the Territory of Hawaii Sixteenth Regular Session, Honolulu, Hawaii, February 1931, 

113 p. + index. 

Langenheim, V.A.M., and Clague, D.A., 1987, The HawaiianEmperor volcanic chain, part II, stratigraphic framework of 

volcanic rocks of the Hawaiian Islands, chap. 1 of Decker, 

R.W., Wright, T.L., and Stauffer, P.H., eds., Volcanism in 

Hawaii: U.S. Geological Survey Professional Paper 1350, 

v. 1, p. 55-84. 

Lanphere, M.A., and Dalrymple, G.B., 1980, Age and strontium isotopic composition of the Honolulu Volcanic Series, 

Oahu, Hawaii: American Journal of Science, v. 280-A, part 

2, p. 736-751. 

Li, Y.-H., 1988, Denudation rates of the Hawaiian islands by 

rivers and groundwaters: Pacific Science, v. 42, nos. 3-4, p. 

253-266.

Liu, C.C.K., Lau, L.S., and Mink, J.F., 1981, Numerical simulation of a thick freshwater lens: Pearl Harbor groundwater 

model: University of Hawaii Water Resources Research 

Center Technical Report no. 139, 71 p.

Lockwood, J.P., and Lipman, P.W., 1987, Holocene eruptive 

history of Mauna Loa Volcano, chap. 18 of Decker, R.W., 

Wright, T.L., and Stauffer, P.H., eds., Volcanism in Hawaii: 

U.S. Geological Survey Professional Paper 1350, v. 1, p. 

509-535.

Macdonald, G.A., 1940, Petrography of the Waianae Range, 

Oahu, in Stearns, H.T., ed., Supplement to geology and 

ground-water resources of the island of Oahu, Hawaii: State 

of Hawaii, Division of Hydrography Bulletin 5, p. 61-91.

References Cited  83
Macdonald, G.A., Abbott, A.T., and Peterson, F.L., 1983, Volcanoes in the sea, the geology of Hawaii (2nd ed.): University of Hawaii Press, Honolulu, 517 p. 

Martin, W.F., and Pierce, C.H., 1913, Water resources of 

Hawaii 1909-1911: U.S. Geological Survey Water-Supply 

Paper 318, 552 p.

Meyer, C.F., Kleinecke, D.C., Todd, D.K., and Ewing, L.E., 

1974, Mathematical modeling of freshwater aquifers having saltwater bottoms, Final technical completion report 

GE74TMP-43, General Electric Co., TEMPO, Center for 

Advanced Studies, Santa Barbara, California, 176 p. + app.

Meyer, William, and Souza, W.R., 1995, Factors that control 

the amount of water that can be diverted to wells in a highlevel aquifer, in Hermann, Raymond, Back, William, Sidle, 

R.C., and Johnson, A.I., eds., Water Resources and Environmental Hazards: Emphasis on Hydrologic and Cultural 

Insight in the Pacific Rim, Proceedings of the American 

Water Resources Association Annual Summer Symposium, 

Honolulu, Hawaii, June 25-28, 1995, p. 207-216.

Miller, M.E., 1987, Hydrogeologic characteristics of central 

Oahu subsoil and saprolite: Implications for solute transport, M.S. thesis, University of Hawaii at Manoa, 231 p.

Mink, J.F., 1980, State of the groundwater resources of southern Oahu, Honolulu Board of Water Supply, 83 p.

Mink, J.F., and Lau, L.S., 1980, Hawaiian groundwater 

geology and hydrology, and early mathematical models: 

University of Hawaii Water Resources Research Center 

Technical Memorandum Report no. 62, 74 p.

Moore, J.G., 1987, Subsidence of the Hawaiian ridge, chap. 

2 of Decker, R.W., Wright, T.L., and Stauffer, P.H., eds., 

Volcanism in Hawaii: U.S. Geological Survey Professional 

Paper 1350, v. 1, p. 85-100.

National Weather Service, 2005, Hydronet archived data: 

National Oceanic and Atmospheric Administration, 

accessed June 16, 2005 at URL http://www.prh.noaa.gov/

hnl/hydro/hydronet/hydronet-data.php.

Nichols, W.D., Shade, P.J., and Hunt, C.D., Jr., 1996, Summary of the Oahu, Hawaii, regional aquifer-system analysis: 

U.S. Geological Survey Professional Paper 1412-A, 61 p.

Oki, D.S., Miyahira, R.N., Green, R.E., Giambelluca, T.W., 

Lau, L.S., Mink, J.F., Schneider, R.C., and Little, D.N., 

1990, Assessment of the potential for groundwater contamination due to proposed urban development in the vicinity of 

the U.S. Navy Waiawa shaft, Pearl Harbor, Hawaii: University of Hawaii Water Resources Research Center Special 

Report 06.01:90, 455 p.

Oki, D.S., 1997, Modeling the effects of pumping, barometric 

pressure, and ocean tides on ground-water levels in northern 

Oahu, Ph.D. dissertation, University of Hawaii at Manoa, 

321 p.

Oki, D.S., 1998, Geohydrology of the central Oahu, Hawaii, 

ground-water flow system and numerical simulation of the 

effects of additional pumping: U.S. Geological Survey 

Water-Resources Investigations Report 97-4276, 132 p.

Oki, D.S., 2005, Trends in streamflow characteristics at 

long-term gaging stations, Hawaii: U.S. Geological Survey 

Scientific Investigations Report 2004-5080, 120 p.

Oki, D.S., and Brasher, A.M.D., 2003, Environmental setting and the effects of natural and human-related factors 

on water quality and aquatic biota, Oahu, Hawaii: : U.S. 

Geological Survey Water-Resources Investigations Report 

03-4156, 98 p.

Oki, D.S., Souza, W.R., Bolke, E.L., and Bauer, G.R., 1998, 

Numerical analysis of the hydrogeologic controls in a layered coastal aquifer system, Oahu, Hawaii, USA: Hydrogeology Journal, v. 6, no. 2, p. 243-263.

Palmer, H.S., 1927, The geology of the Honolulu artesian system: Honolulu Sewer and Water Commission, 68 p.

Palmer, H.S., 1946, The geology of the Honolulu ground water 

supply: Honolulu Board of Water Supply, 55 p.

Paillet, F.L., Williams, J.H., Oki, D.S., and Knutson, K.D., 

2002, Comparison of formation and fluid-column logs in a 

heterogeneous basalt aquifer: Ground Water, v. 40, no. 6, p. 

577-585.

Peterson, F.L., and Sehgal, M.M., 1974, Determining porosity 

with neutron logs from Hawaiian basaltic aquifers: University of Hawaii Water Resources Research Center Technical 

Report no. 80, 37 p.

Pineapple Growers Association of Hawaii, 1969, Pineapple 

fact book/Hawaii 1969, Honolulu, Hawaii, 24 p.

Presley, T.K., 1994, Late postshield volcanism on Waianae 

Volcano Oahu, Hawaii, M.S. thesis, University of Hawaii at 

Manoa, 101 p.

Presley, T.K., Sinton, J.M., and Pringle, Malcolm, 1997, 

Postshield volcanism and catastrophic mass wasting of the 

Waianae Volcano, Oahu, Hawaii: Bulletin of Volcanology, v. 

58, p. 597-616.

R.M. Towill Corporation, 1978, Feasibility study, surface 

water impoundment/recharge Pearl Harbor basin Oahu, 

Hawaii, variously paginated.

Sanderson, Marie, 1993, Prevailing trade winds, weather and 

climate in Hawaiʻi, University of Hawaii Press, Honolulu, 

126 p.

84  Numerical Simulation of the Effects of Valley-Fill Barriers in the Pearl Harbor Area, Oahu, Hawaii
Schuyler, J.D., and Allardt, G.F., 1889, Report on water supply for irrigation on the Honouliuli and Kahuku ranchos, 

island of Oahu, Hawaiian islands: Oakland, Cal., Jordan and 

Arnold Printers, 32 p.

Seckel, G.R., 1962, Atlas of the oceanographic climate of 

the Hawaiian Islands region: Fishery Bulletin 193, from 

Fishery Bulletin of the Fish and Wildlife Service, v. 61, p. 

373-427, Fish and Wildlife Service, U.S. Department of the 

Interior. 

Shade, P.J., and Nichols, W.D., 1996, Water budget and the 

effects of land-use changes on ground-water recharge, 

Oahu, Hawaii: U.S. Geological Survey Professional Paper 

1412-C, 38 p.

Shepard, F.P., and Dill, R.F., 1966, Submarine canyons and 

other sea valleys: Chicago, Rand MacNally, 343 p.

Sinton, J.M., 1986, Revision of stratigraphic nomenclature of 

Waianae Volcano, Oahu, Hawaii: U.S. Geologic Survey 

Bulletin 1775-A, p. A9-A15. 

Soroos, R.L., 1973, Determination of hydraulic conductivity 

of some Oahu aquifers with step-drawdown test data, M.S. 

thesis, University of Hawaii at Manoa, 239 p.

Soroos, R.L., and Ewart, C.J., 1979, Ground-water status 

report, Pearl Harbor area, Hawaii, 1978: U.S. Geological 

Survey Open-File Report 79-1542, 3 sheets. 

Souza, W.R., and Voss, C.I., 1987, Analysis of an anisotropic coastal aquifer system using variable-density flow and 

solute transport simulation: Journal of Hydrology, v. 92, p. 

17-41.

State of Hawaii, 1983, Preliminary report on soil sampling 

for EDB on Oahu: Department of Agriculture, Division of 

Plant Industry, Pesticides Branch, Honolulu, Hawaii., 19 p. 

+ app.

State of Hawaii, 2000, The State of Hawaii data book 2000, a 

statistical abstract: State of Hawaii, Department of Business, Economic Development, and Tourism, accessed January 24, 2002 at URL http://www.hawaii.gov/dbedt/db00. 

Stearns, H.T., 1939, Geologic map and guide of the island of 

Oahu, Hawaii: Hawaii Division of Hydrography, Bulletin 2, 

75 p., map scale 1:62,500.

Stearns, H.T., 1940, Supplement to geology and ground-water 

resources of the island of Oahu, Hawaii: Hawaii Division 

of Hydrography, Bulletin 5, 164 p.

Stearns, H.T., 1985, Geology of the State of Hawaii (2d ed.): 

Palo Alto, Calif., Pacific Books Publishers, 335 p.

Stearns, H.T., and Chamberlain, T.K., 1967, Deep cores of 

Oahu, Hawaii and their bearing on the geologic history of 

the central Pacific basin: Pacific Science, v. XXI, no. 2, p. 

153-165.

Stearns, H.T., and Vaksvik, K.N., 1935, Geology and groundwater resources of the island of Oahu, Hawaii: Hawaii 

Division of Hydrography, Bulletin 1, 479 p.

Takasaki, K.J., and Mink, J.F., 1985, Evaluation of major dikeimpounded ground-water reservoirs, island of Oahu: U.S. 

Geological Survey Water-Supply Paper 2217, 77 p.

Taogoshi, R.I., Nishimoto, D.C., Fontaine, R.A., Wong, M.F., 

and Hill, B.R., 2001, Water resources data, Hawaii and 

other Pacific areas, water year 2000, v. 1: U.S. Geological 

Survey Water-Data Report HI-00-1, 379 p.

Thrum, T.G., 1889, Artesian wells on Oahu, Hawaiian Almanac and Annual for 1889: Honolulu, Hawaii, Press Publishing Company Steam Print, p. 61-63. 

U.S. Army Corps of Engineers, 2000, Scanning Hydrographic 

Operational Airborne Lidar Survey (SHOALS), accessed 

December 20, 2002 at URL http://shoals.sam.usace.army.

mil/Hawaii/pages/Hawaii_Data.htm

U.S. Geological Survey, 2002, Pacific sea-floor mapping, 

accessed November 25, 2002 at URL http://wrgis.wr.usgs.

gov/dds/dds-55/pacmaps/site.htm. 

U.S. Geological Survey, 2003, Pearl Harbor area groundwater-level surveys, October 31, 2002 and May 15, 2003, 

accessed December 16, 2003 at URL http://hi.water.usgs.

gov/projects/pearl/pearl_index.html. 

Visher, F.N., and Mink, J.F., 1964, Ground-water resources 

in southern Oahu, Hawaii: U.S. Geological Survey WaterSupply Paper 1778, 133 p. 

Voss, C. I., and Provost, A.M., 2003, SUTRA, A model for 

saturated-unsaturated variable-density ground-water flow 

with solute or energy transport: U.S. Geological Survey 

Water-Resources Investigations Report 02-4231, 250 p. 

Walker, G.P.L., 1987, The dike complex of Koolau Volcano, 

Oahu: internal structure of a Hawaiian rift zone, chap. 41 of 

Decker, R.W., Wright, T.L., and Stauffer, P.H., eds., Volcanism in Hawaii: U.S. Geological Professional Paper 1350, 

v. 2, p. 961-993. 

Wentworth, C.K., 1938, Geology and ground water resources 

of the Palolo-Waialae District: Honolulu, Hawaii, Honolulu 

Board of Water Supply, 274 p.

Wentworth, C.K., 1951, Geology and ground-water resources 

of the Honolulu-Pearl Harbor area Oahu, Hawaii: Honolulu 

Board of Water Supply, Honolulu, Hawaii, 111 p.

References Cited  85
Wentworth, C.K., and Macdonald, G.A., 1953, Structures and 

forms of basaltic rocks in Hawaii: U.S. Geological Survey 

Bulletin 994, 98 p.

Wentworth, C.K. and Winchell, Horace, 1947, Koolau basalt 

series, Oahu, Hawaii: Geological Society of America Bulletin, v. 58, p. 49-77.

Whiteman, C.D., and Bian, Xindi, 1996, Solar semidiurnal 

tides in the troposphere: Detection by radar profilers: Bulletin of the American Meteorological Society, v. 77, no. 3, 

p. 529-542.

Williams, J.A., and Soroos, R.L., 1973, Evaluation of methods 

of pumping test analyses for application to Hawaiian aquifers: University of Hawaii Water Resources Research Center 

Technical Report no. 70, 159 p. 

Winchell, Horace, 1947, Honolulu series, Oahu, Hawaii: Geological Society of America Bulletin, v. 58, p. 1-48.

Winston, R.B. and Voss, C.I., 2003, SutraGUI, a graphicaluser interface for SUTRA, a model for ground-water flow 

with solute or energy transport: U.S. Geological Survey 

Open-File Report 03-285, 114 p., http://water.usgs.gov/nrp/

gwsoftware/sutra.html.

Yamauchi, Hiroshi, and Bui, Win, 1990, Drip irrigation and 

the survival of the Hawaii sugarcane industry: University 

of Hawaii College of Tropical Agriculture and Human 

Resources, Research Extension Series 113, 8 p.

Yim, S.K., and Dugan, G.L., 1975, Quality and quantity of 

nonpoint pollution sources in rural surface water runoff 

on Oahu, Hawaii: University of Hawaii Water Resources 

Research Center Technical Report no. 93, 60 p.

86  Numerical Simulation of the Effects of Valley-Fill Barriers in the Pearl Harbor Area, Oahu, Hawaii
Appendix A. Monthly ground-water withdrawals during 1890 to 2000 from wells 

in the Pearl Harbor and Moanalua areas, Oahu, Hawaii

Appendix A  87
1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000

0.40.30.20.10.00.40.30.20.10.00.40.30.20.10.00.40.30.20.10.00.40.30.20.10.01.51.00.50.0

1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000

2.01.51.00.50.0

0.080.060.040.020.00

50

1510

0.80.60.40.20.0

3210

0.100.050.00

PUMPAGE, IN MILLION GALLONS PER DAY 1805-07

1805-09

1806-101806-201807-01

1805-051805-061805-08

1806-091806-111806-19

1805-04

Figure A1. Monthly ground-water withdrawals during 1890 to 2000 from wells in the Pearl Harbor and Moanalua areas, Oahu, Hawaii. 

88  Numerical Simulation of the Effects of Valley-Fill Barriers in the Pearl Harbor Area, Oahu, Hawaii
0.8

0.60.40.20.0

64204321050

201510

0.80.60.40.20.00.40.30.20.10.0

0.40.30.20.10.00.40.30.20.10.00.80.60.40.20.00.80.60.40.20.0

50

10

0.40.30.20.10.0

1807-031900-011900-021900-131900-171900-18

1900-191900-201900-211900-221901-011901-03

1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000

PUMPAGE, IN MILLION GALLONS PER DAY 

Figure A1. Monthly ground-water withdrawals during 1890 to 2000 from wells in the Pearl Harbor and Moanalua areas, Oahu, Hawaii—Continued.

Appendix A  89
5

0

201510

1.00.50.0

?0.1?0.0

0.40.30.2

50

1510

?0.1?0.0

0.40.30.2

0.200.150.100.050.00

0.40.30.20.10.0

0.200.150.100.050.00

0.40.30.20.10.0

0.200.150.100.050.00

1.00.50.0

0.030.020.010.00

1902-011902-031902-051904-011904-021905-04

1905-081905-091905-101906-031906-041906-05

1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000

PUMPAGE, IN MILLION GALLONS PER DAY 

Figure A1. Monthly ground-water withdrawals during 1890 to 2000 from wells in the Pearl Harbor and Moanalua areas, Oahu, Hawaii—Continued.

90 Numerical Simulation of the Effects of Valley-Fill Barriers in the Pearl Harbor Area, Oahu, Hawaii
0.4

0.30.20.10.01.51.00.50.0

321050

1510

0.200.150.100.050.00

0.40.30.20.10.0

0.040.030.020.010.000.200.150.100.050.000.060.040.020.00

0.80.60.40.20.0

0.200.150.100.050.00

0.0040.0030.0020.0010.000

1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000

PUMPAGE, IN MILLION GALLONS PER DAY 

1906-061959-082000-012001-012001-022001-03

2001-042001-052001-062001-072001-082001-09

Figure A1. Monthly ground-water withdrawals during 1890 to 2000 from wells in the Pearl Harbor and Moanalua areas, Oahu, Hawaii—Continued.

Appendix A  91
estimated

0.200.150.100.050.00

1.00.50.0

?0.1?0.0

0.40.30.2

50

1510

0.080.060.040.020.00

1.00.50.0

0.80.60.40.20.00.80.60.40.20.00.80.60.40.20.00.80.60.40.20.00.80.60.40.20.0

0.030.020.010.00

2001-102001-132001-142002-01 to -08,-10 2002-122002-15

2002-162002-172002-182002-192003-012003-02

1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000

PUMPAGE, IN MILLION GALLONS PER DAY 

Figure A1. Monthly ground-water withdrawals during 1890 to 2000 from wells in the Pearl Harbor and Moanalua areas, Oahu, Hawaii—Continued.

92  Numerical Simulation of the Effects of Valley-Fill Barriers in the Pearl Harbor Area, Oahu, Hawaii
0.4

0.30.20.10.00.80.60.40.20.00.40.30.20.10.00.80.60.40.20.0

32100

40302010

1.51.00.50.0

50

201510

0.80.60.40.20.00.40.30.20.10.00.40.30.20.10.0

0.0150.0100.0050.000

2003-032003-042003-052003-072004-042006-01 to -11 

2006-132052-082053-022053-032053-052053-06

1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000

PUMPAGE, IN MILLION GALLONS PER DAY 

Figure A1. Monthly ground-water withdrawals during 1890 to 2000 from wells in the Pearl Harbor and Moanalua areas, Oahu, Hawaii—Continued.

Appendix A  93
estimated

0

0.5

1

1.5

0

0.40.30.20.1

0

0.5

1

1.5

20

0.40.30.20.1

0

0.060.040.02

0

0.40.30.20.1

0

0.40.30.20.1

0

0.080.060.040.02

0

0.5

1

1.5

0

0.05

0.1

50

1510

0

0.80.60.40.2

2053-082053-092053-102053-122054-012054-02

2054-03

2055-01

2101-01

2101-02

2101-05 to -12 

2101-14

1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000

PUMPAGE, IN MILLION GALLONS PER DAY 

1890 1900 1910 1920 1930 1940 1950 1960 1980 1990 2000 1970

Figure A1. Monthly ground-water withdrawals during 1890 to 2000 from wells in the Pearl Harbor and Moanalua areas, Oahu, Hawaii—Continued.

94  Numerical Simulation of the Effects of Valley-Fill Barriers in the Pearl Harbor Area, Oahu, Hawaii
estimated

0

40302010

64200

0.40.30.20.10.80.60.40.20.00.80.60.40.20.00.40.30.20.10.0

0.80.60.40.20.02.01.51.00.50.01.00.50.0

6420

2.01.51.00.50.0

0.080.060.040.020.00

2102-02,-04 to -22 2103-032104-012153-012153-022153-04

2153-052153-062153-07,-082153-10 to -12 2154-012155-04

1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000

PUMPAGE, IN MILLION GALLONS PER DAY 

Figure A1. Monthly ground-water withdrawals during 1890 to 2000 from wells in the Pearl Harbor and Moanalua areas, Oahu, Hawaii—Continued.

Appendix A  95
estimated

estimated

estimated

estimated

estimated

estimated

50

10

3210

0.200.150.100.050.00

0.0010.000

0

302010

50

201510

0

40302010

50

201510

0

302010

0

302010

50

201510

0.80.60.40.20.0

2201-03,-04,-072201-052201-142202-01

2202-03 to -14 2202-15 to -20 

2202-212203-01 to -06 2254-01

2255-07 to -20,-29 to -31 2255-21 to -28 

2255-32

1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000

PUMPAGE, IN MILLION GALLONS PER DAY 

Figure A1. Monthly ground-water withdrawals during 1890 to 2000 from wells in the Pearl Harbor and Moanalua areas, Oahu, Hawaii—Continued.

96  Numerical Simulation of the Effects of Valley-Fill Barriers in the Pearl Harbor Area, Oahu, Hawaii
estimated

estimated

estimated

estimated

estimated

3210321050

201510

864200

302010

1.51.00.50.0

50

10

50

1510

50

1510

0

302010

50

1510

0.80.60.40.20.0

2255-35,-362255-37 to -39 2256-05 to -09 2256-102300-07 to -09,-12 to -14,-16,-17,-21 to -23 2300-11

2300-18

2301-01 to -10 2301-11 to -20 2301-21 to -32 

2301-34 to -39 2302-01 to -04 

1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000

PUMPAGE, IN MILLION GALLONS PER DAY 

Figure A1. Monthly ground-water withdrawals during 1890 to 2000 from wells in the Pearl Harbor and Moanalua areas, Oahu, Hawaii—Continued.

Appendix A  97
estimated

estimated

6420864200

40302010

50

1510

1.51.00.50.02.01.51.00.50.0

50

1510

50

201510

50

201510

0.40.30.20.10.00.80.60.40.20.0

0.030.020.010.00

2303-01,-022303-03 to -06 2354-012355-022355-03 to -05 2355-06,-07

2355-09 to -14 

2356-14 to -33 2356-34 to -42 

2356-442356-49,-502356-54

1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000

PUMPAGE, IN MILLION GALLONS PER DAY 

Figure A1. Monthly ground-water withdrawals during 1890 to 2000 from wells in the Pearl Harbor and Moanalua areas, Oahu, Hawaii—Continued.

98  Numerical Simulation of the Effects of Valley-Fill Barriers in the Pearl Harbor Area, Oahu, Hawaii
3

2103210

2.01.51.00.50.0

3210

0.080.060.040.020.00

2.01.51.00.50.0

2.01.51.00.50.01.51.00.50.00.80.60.40.20.0

6420

0.0200.0150.0100.0050.000

0.00080.00060.00040.00020.0000

2356-55,-562356-58,-592356-60,-63,-642356-61,-62,-652356-702357-21

2357-222357-23,-242358-03,-07,-132358-14 to -17 2358-242358-28

1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000

PUMPAGE, IN MILLION GALLONS PER DAY 

Figure A1. Monthly ground-water withdrawals during 1890 to 2000 from wells in the Pearl Harbor and Moanalua areas, Oahu, Hawaii—Continued.

Appendix A  99
0.8

0.60.40.20.00.80.60.40.20.0

0.040.030.020.010.00

1.00.50.00.40.30.20.10.01.00.50.0

8642086420

1.00.50.0

3210

0.00030.00020.00010.0000

0.0000150.0000100.0000050.000000

2358-422358-482359-032359-052359-152359-17

2400-01 to -04 2400-05,-06,-08,-142401-072402-01 to -03,-05 2451-012455-02

1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000

PUMPAGE, IN MILLION GALLONS PER DAY 

Figure A1. Monthly ground-water withdrawals during 1890 to 2000 from wells in the Pearl Harbor and Moanalua areas, Oahu, Hawaii—Continued.

100 Numerical Simulation of the Effects of Valley-Fill Barriers in the Pearl Harbor Area, Oahu, Hawaii
estimated 2456-01 to -03 

2457-01 to -03 2457-05 to -12 2457-13 to -15 2458-01

3210321050

1510

3210

2.01.51.00.50.02.01.51.00.50.0

2458-03,-04

2459-01 to-14 

2459-19,-202459-212459-23,-242500-01,-02

50

201510

3210

0.0100.0050.000

2.01.51.00.50.01.51.00.50.0

0.060.040.020.00

2557-01,-02

1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000 1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000

PUMPAGE, IN MILLION GALLONS PER DAY 

Figure A1. Monthly ground-water withdrawals during 1890 to 2000 from wells in the Pearl Harbor and Moanalua areas, Oahu, Hawaii—Continued.

Appendix A 101
0.8

0.60.40.20.0

0

302010

0.0200.0150.0100.0050.000

2.01.51.00.50.00.80.60.40.20.0

86420

2.01.51.00.50.01.51.00.50.0

6420

2.01.51.00.50.0

3210

2557-032558-102600-022600-03,-042603-012658-01,-02

2659-02,-032703-012800-01 to -04 2858-01 to -03 2859-01,-02

1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000

1890 1900 1910 1920 1930 1940 1950 1960 1970 1980 1990 2000

PUMPAGE, IN MILLION GALLONS PER DAY 

Figure A1. Monthly ground-water withdrawals during 1890 to 2000 from wells in the Pearl Harbor and Moanalua areas, Oahu, Hawaii—Continued.

102  Numerical Simulation of the Effects of Valley-Fill Barriers in the Pearl Harbor Area, Oahu, Hawaii
Appendix B. Properties of pumped wells in the Pearl Harbor area

Appendix B 103
Table B1. Properties of pumped wells in the Pearl Harbor area, Oahu, Hawaii (modified from unpub. digital database, 

2002, Hawaii Commission on Water Resource Management)—Continued.

[--, data not available]

Well no. Well name Year drilled

Ground

altitude,

in feet

Well depth,

in feet

Depth of solid 

casing, in feet

1805-04 Kalaeloa PW-1 1990 13 25 17

1805-05 Kalaeloa PW-2 1990 14 25 17

1805-06 Kalaeloa PW-3 1990 13 25 17

1805-07 Kalaeloa PW-4 1990 14 25 17

1805-08 Kalaeloa PW-5 1990 14 25 17

1805-09 Kalaeloa PW-6 1990 14 40 17

1806-09 Facility Maint 1 1986 12 103 50

1806-10 Facility Maint 2 1986 12 105 50

1806-11 AES Prod 1 1989 12 115 60

1806-19 Ewa Island Comm -- -- 25 --

1806-20 Acid Plant 1959 5 -- --

1807-01 Lpg Storage Area 1959 3 -- --

1807-03 Mauka-Makai St 1959 4 -- --

1900-01 Ep 20 1930 25 30 --

1900-02 Ep 22 1930 23 29 --

1900-13 EP 30 1965 5 8 --

1900-17 Haw Prince Irr 2 1990 20 26 18

1900-18 Haw Prince Irr 3 1990 20 25 17

1900-19 Haw Prince Irr 4 1990 20 25 17

1900-20 Haw Prince Irr 5 1990 20 25 17

1900-21 New Ewa Intl G C 1991 18 30 15

1900-22 Dug C 1988 -- 12 --

1900-23 Pac Tsunami Cntr 1999 -- 9 9

1901-01 Ep 24 1932 24 29 --

1901-03 Haw Prince Irr 1 1990 21 26 18

1901-05 Gentry Area 13 1999 33 43 31

1901-06 -- -- -- -- --

1902-01 Ep 27A&B, 28&29 1964 5 8 --

1902-03 Honouliuli STP 1 1991 36 51 31

1902-05 Coral Creek 5 1998 36 68 40

1904-01 Ep 31&32 1965 5 8 --

1904-02 Makakilo G C 1 1991 -- 77 57

1905-04 Ewa Desalt Basal 1988 -- 380 275

1905-05 Caprock 1 1988 -- 80 52

1905-08 Kapolei Irr 1 1991 65 84 64

1905-09 Caprock 3 1992 54 80 60

1905-10 Kapolei Irr 2 1993 65 94 54

1906-03 Grace Pac C-3 1988 -- 120 40

1906-04 Grace Pac C-2 1988 -- 120 40

1906-05 Grace Pac B-1 1988 -- 250 120

1906-06 Grace Pac C-1 1987 -- 118 45

1959-08 Dug D 1988 -- 12 --

2000-01 Ep 21 1930 25 30 --

2001-01 Ep 23 1931 43 47 --

2001-02 Gentry Entry Irr 1987 28 38 29

2001-03 Geiger Park 1989 38 56 36

2001-04 Sunrise 1994 38 61 36

2001-05 Sun Terra 1994 36 65 35

2001-06 Palm Villa I 1990 41 60 40

2001-07 Arbors GV 1 1991 33 50 28

2001-08 Palm Villa 2 1991 36 61 41

2001-09 Ft Weaver Apt. 1994 35 56 31

2001-10 Gentry Area 24 1996 34 52 30

2001-12 Keaunui Area 30 1999 31 39 29

2001-13 Coral Creek 4 1998 34 48 35

2001-14 Lake 10 1998 -- 5 --

2002-01 Ewa 1891 47 507 419

2002-02 Ewa 1891 46 523 450

Table B1. Properties of pumped wells in the Pearl Harbor area, Oahu, Hawaii (modified from unpub. digital database, 2002, Hawaii 

Commission on Water Resource Management).

[--, data not available]

104  Numerical Simulation of the Effects of Valley-Fill Barriers in the Pearl Harbor Area, Oahu, Hawaii
Table B1. Properties of pumped wells in the Pearl Harbor area, Oahu, Hawaii (modified from unpub. digital database, 

2002, Hawaii Commission on Water Resource Management)—Continued.

[--, data not available]

Well no. Well name Year drilled

Ground

altitude,

in feet

Well depth,

in feet

Depth of solid 

casing, in feet

2002-03 Ewa 1899 46 551 438

2002-04 Ewa 1899 46 550 450

2002-05 Ewa 1900 46 522 450

2002-06 Ewa 1900 46 518 445

2002-07 Ewa 1908 46 498 --

2002-08 Ewa 1908 46 497 464

2002-10 Ewa 1944 40 213 --

2002-12 Palm Court 3 1989 40 60 40

2002-15 Coral Creek 1 1997 40 55 38

2002-17 Coral Creek 2 1998 30 48 37

2002-18 Coral Creek 3 1998 34 47 37

2002-19 Lake A 1998 -- 5 --

2003-01 Kapolei Irr A 1991 60 85 65

2003-02 Kapolei Irr B 1991 60 82 62

2003-03 Kapolei Irr C 1991 -- 77 52

2003-04 Kapolei Irr D 1991 59 73 53

2003-05 Kapolei Irr E 1991 60 100 62

2003-07 Kapolei Irr C-1 1994 62 81 60

2003-08 East Kapolei 1999 51 70 51

2004-04 Makakilo 1981 141 268 188

2006-01 Ep 10 A 1908 41 -- --

2006-02 Ep 10 C 1908 41 282 62

2006-03 Ep 10 D 1908 41 -- --

2006-04 Ep 10 E 1908 41 155 --

2006-05 Ep 10 F 1908 41 165 --

2006-06 Ep 10 G 1908 41 165 --

2006-07 Ep 10 H 1908 41 -- --

2006-08 Ep 10 J 1913 41 -- --

2006-09 Ep 10 K 1913 41 -- --

2006-10 Ep 10 B 1923 41 160 60

2006-11 Ep 10 I 1923 41 160 57

2006-13 W Beach Estates 1986 58 120 58

2006-14 BP Non-Potable 1 1988 179 285 228

2052-08 Kalihi Shaft 1937 160 154 --

2053-02 Ft Shafter 1885 10 427 238

2053-03 Kalihi 1886 27 645 520

2053-05 Kalihi 1894 20 471 347

2053-06 Ft Shafter 1895 8 330 236

2053-08 Kalihi 1903 7 670 507

2053-09 Kalihi 1905 22 607 449

2053-10 Ft Shafter Mon. 1914 20 279 168

2053-11 Ft Shafter 1960 21 330 175

2053-12 Kalihi 1967 6 789 588

2054-01 Puuloa Rd 1898 19 824 692

2054-02 Puuloa Rd 1959 6 677 616

2054-03 Puuloa Rd. 1965 6 668 597

2055-01 Nimitz Hwy -- 20 795 517

2101-01 Honouliuli -- 20 325 208

2101-02 Honouliuli -- 25 -- --

2101-05 Honouliuli B 1890 30 456 320

2101-06 Honouliuli C 1890 30 451 310

2101-07 Honouliuli D 1890 30 468 302

2101-08 Honouliuli E 1890 30 462 310

2101-09 Honouliuli F 1890 31 448 432

2101-10 Honouliuli G 1899 30 462 304

2101-11 Honouliuli 1899 30 450 316

2101-12 Honouliuli A 1901 30 452 298

2101-14 Honouliuli 1978 6 12 4

Appendix B 105
Table B1. Properties of pumped wells in the Pearl Harbor area, Oahu, Hawaii (modified from unpub. digital database, 

2002, Hawaii Commission on Water Resource Management)—Continued.

[--, data not available]

Well no. Well name Year drilled

Ground

altitude,

in feet

Well depth,

in feet

Depth of solid 

casing, in feet

2102-02 Ep 18 Battery 1890 44 332 --

2102-04 Ep 18 Battery 1891 44 326 --

2102-05 Ep 18 Battery 1891 44 369 --

2102-06 Ep 18 Battery 1891 44 405 208

2102-07 Ep 18 Battery 1891 44 410 214

2102-08 Ep 18 Battery 1891 44 410 --

2102-09 Ep 18 Battery 1891 44 410 --

2102-10 Ep 18 Battery 1891 44 413 --

2102-11 Ep 18 Battery 1891 44 433 --

2102-12 Ep 18 Battery 1891 44 432 --

2102-13 Ep 18 Battery 1891 44 436 --

2102-14 Ep 18 Battery 1891 44 430 --

2102-15 Ep 18 Battery 1899 44 441 218

2102-16 Ep 18 Battery 1899 44 435 223

2102-17 Ep 18 Battery 1899 44 442 212

2102-18 Ep 18 Battery 1899 44 444 223

2102-19 Ep 18 Battery 1921 44 416 212

2102-20 Ep 18 Battery 1921 44 419 222

2102-21 Ep 18 Battery 1921 44 425 217

2102-22 Ep 18 Battery 1921 44 420 240

2103-03 Barbers Pt Shaft 1943 200 204 --

2104-01 Makakilo Quarry 1976 125 176 140

2153-01 Moanalua 1888 25 492 447

2153-02 Moanalua 1889 20 289 79

2153-04 Moanalua 1909 24 280 48

2153-05 Moanalua Deep 1980 35 -- 65

2153-06 Moanalua 1929 18 282 143

2153-07 Moanalua 1945 30 302 52

2153-08 Moanalua 1945 29 306 57

2153-10 Moanalua 1 1973 36 300 150

2153-11 Moanalua 2 1973 35 300 150

2153-12 Moanalua 3 1974 35 335 185

2154-01 HICC 1909 14 294 103

2155-04 Makalapa 1941 91 288 148

2201-02 Honouliuli -- 17 356 77

2201-03 Ep 2 1891 40 230 50

2201-04 Ep 2 1891 40 226 50

2201-05 Pearl Harbor 1892 11 170 98

2201-07 Ep 2 1921 40 282 62

2201-14 Pearl Harbor 1969 18 185 114

2202-01 Honouliuli -- 23 500 --

2202-02 Honouliuli -- 16 395 96

2202-03 Ep 18 Battery 1896 50 304 70

2202-04 Ep 18 Battery 1896 50 305 70

2202-05 Ep 18 Battery 1896 50 310 70

2202-06 Ep 18 Battery 1896 50 304 70

2202-07 Ep 18 Battery 1896 50 306 70

2202-08 Ep 18 Battery 1896 50 303 70

2202-09 Ep 18 Battery 1896 50 312 70

2202-10 Ep 18 Battery 1897 50 307 70

2202-11 Ep 18 Battery 1897 50 306 70

2202-12 Ep 18 Battery 1897 50 308 70

2202-13 Ep 18 Battery 1897 50 308 70

2202-14 Ep 18 Battery 1897 50 308 70

2202-15 Ep 18 Battery 1899 46 468 107

2202-16 Ep 18 Battery 1900 46 476 116

2202-17 Ep 18 Battery 1900 46 475 116

2202-18 Ep 18 Battery 1900 46 475 116

106  Numerical Simulation of the Effects of Valley-Fill Barriers in the Pearl Harbor Area, Oahu, Hawaii
Table B1. Properties of pumped wells in the Pearl Harbor area, Oahu, Hawaii (modified from unpub. digital database, 

2002, Hawaii Commission on Water Resource Management)—Continued.

[--, data not available]

Well no. Well name Year drilled

Ground

altitude,

in feet

Well depth,

in feet

Depth of solid 

casing, in feet

2202-19 Ep 18 Battery 1900 46 481 107

2202-20 Ep 18 Battery 1900 46 475 108

2202-21 Ep 15,16 1939 150 156 --

2203-01 Waipahu Wp5 1900 19 213 88

2203-02 Waipahu Wp5 1900 19 158 88

2203-03 Waipahu Wp5 1900 19 263 88

2203-04 Waipahu Wp5 1900 19 233 88

2203-05 Waipahu Wp5 1900 19 246 88

2203-06 Waipahu Wp5 1900 19 197 88

2254-01 Halawa Red Hill 1943 200 210 --

2255-07 Halawa 1900 21 391 150

2255-08 Halawa 1900 19 173 127

2255-09 Halawa 1900 23 399 160

2255-10 Halawa 1900 25 500 --

2255-11 Halawa 1900 25 500 --

2255-12 Halawa 1900 19 205 155

2255-13 Halawa 1900 22 288 150

2255-14 Halawa 1900 20 236 134

2255-15 Halawa 1900 23 431 135

2255-16 Halawa 1900 22 422 132

2255-17 Halawa 1900 25 450 152

2255-18 Halawa 1900 26 457 157

2255-19 Halawa 1900 22 426 130

2255-20 Halawa 1900 21 421 120

2255-21 Halawa 1900 31 394 225

2255-22 Halawa 1900 32 403 400

2255-23 Halawa 1900 23 404 118

2255-24 Halawa 1900 26 220 150

2255-25 Halawa 1900 23 388 96

2255-26 Halawa 1900 33 365 350

2255-27 Halawa 1900 20 303 300

2255-28 Halawa 1900 22 128 103

2255-29 Halawa 1930 26 440 149

2255-30 Halawa 1930 20 427 195

2255-31 Halawa 1930 20 423 190

2255-32 Aiea Halawa Shft 1937 95 99 --

2255-35 Aiea Refinery 1 1956 119 196 151

2255-36 Aiea Refinery 2 1956 119 240 151

2255-37 Halawa 2 1961 256 345 285

2255-38 Halawa 3 1961 270 359 314

2255-39 Halawa 1 1961 258 399 276

2256-05 Aiea 1908 38 344 87

2256-06 Aiea 1908 38 338 93

2256-07 Aiea 1908 38 345 71

2256-08 Aiea 1908 38 359 98

2256-09 Aiea 1908 45 -- 80

2256-10 Aiea 1922 11 173 143

2300-07 Waipahu P7A 1900 60 -- --

2300-08 Waipahu P7B 1900 60 -- --

2300-09 Waipahu P7C 1900 60 -- --

2300-11 Waipahu 1913 18 202 56

2300-12 Waipahu P7D 1917 60 400 92

2300-13 Waipahu P7E 1917 60 400 102

2300-14 Waipahu P7F 1917 60 402 128

2300-16 Waipahu P7G 1924 60 412 98

2300-17 Waipahu P7H 1924 60 430 92

2300-18 Waipahu Deep 1980 26 -- 38

2300-20 Waipahu 1959 13 204 56

Appendix B 107
Table B1. Properties of pumped wells in the Pearl Harbor area, Oahu, Hawaii (modified from unpub. digital database, 

2002, Hawaii Commission on Water Resource Management)—Continued.

[--, data not available]

Well no. Well name Year drilled

Ground

altitude,

in feet

Well depth,

in feet

Depth of solid 

casing, in feet

2300-21 Waipahu P7A 1962 64 320 101

2300-22 Waipahu P7B 1962 64 364 101

2300-23 Waipahu P7C 1962 64 378 102

2301-01 Waipahu WP1 -- 21 425 --

2301-02 Waipahu WP1 -- 30 -- --

2301-03 Waipahu WP1 -- 30 400 --

2301-04 Waipahu WP1 -- 30 400 --

2301-05 Waipahu WP1 -- 43 410 --

2301-06 Waipahu WP1 -- 30 400 --

2301-07 Waipahu WP1 -- 29 400 --

2301-08 Waipahu WP1 -- 30 412 --

2301-09 Waipahu WP1 -- 31 490 --

2301-10 Waipahu WP1 -- 31 498 --

2301-11 Waipahu WP4B 1898 19 500 --

2301-12 Waipahu WP4B 1898 19 500 --

2301-13 Waipahu WP4B 1898 19 500 --

2301-14 Waipahu WP4B 1898 19 500 --

2301-15 Waipahu WP4B 1898 19 500 --

2301-16 Waipahu WP4B 1898 19 500 --

2301-17 Waipahu WP4B 1898 19 500 --

2301-18 Waipahu WP4A 1898 19 500 --

2301-19 Waipahu WP4A 1898 19 500 --

2301-20 Waipahu WP4A 1898 19 500 --

2301-21 Waipahu WP2A2B 1898 20 425 --

2301-22 Waipahu WP2A2B 1898 20 425 --

2301-23 Waipahu WP2A2B 1898 20 400 --

2301-24 Waipahu WP2A2B 1898 20 410 --

2301-25 Waipahu WP2A2B 1898 20 414 --

2301-26 Waipahu WP2A2B 1898 20 410 --

2301-27 Waipahu WP2C2D 1898 20 400 --

2301-28 Waipahu WP2C2D 1898 20 400 --

2301-29 Waipahu WP2C2D 1898 20 410 --

2301-30 Waipahu WP2C2D 1898 20 420 --

2301-31 Waipahu WP2C2D 1898 20 429 --

2301-32 Waipahu WP2C2D 1898 20 439 --

2301-34 Hoaeae P1 1959 131 194 107

2301-35 Hoaeae P2 1959 133 197 113

2301-36 Hoaeae P3 1959 131 198 107

2301-37 Hoaeae P4 1959 130 195 108

2301-38 Hoaeae P5 1974 126 276 176

2301-39 Hoaeae P6 1974 123 273 173

2301-44 Waipahu IV-2 1998 133 273 173

2301-45 Waipahu IV-3 1998 136 276 176

2301-46 Waipahu IV-1 1998 131 271 171

2301-47 Waipahu IV-4 1999 134 273 173

2302-01 Kunia I P1 1957 201 350 221

2302-02 Kunia I P2 1957 201 338 221

2302-03 Kunia I P3 1972 206 427 246

2302-04 Kunia I P4 1972 201 420 241

2303-01 Honouliuli I-1 1987 412 625 550

2303-02 Honouliuli I-2 1987 411 563 550

2303-03 Honouliuli II-3 1987 419 534 450

2303-04 Honouliuli II-4 1988 421 555 455

2303-05 Honouliuli II-5 1989 432 545 465

2303-06 Honouliuli II-6 1989 432 535 455

2354-01 Halawa Shaft 1944 165 183 --

2355-02 Aiea 1945 195 200 --

2355-03 Aiea Gulch 1 1947 304 342 288

108  Numerical Simulation of the Effects of Valley-Fill Barriers in the Pearl Harbor Area, Oahu, Hawaii
Table B1. Properties of pumped wells in the Pearl Harbor area, Oahu, Hawaii (modified from unpub. digital database, 

2002, Hawaii Commission on Water Resource Management)—Continued.

[--, data not available]

Well no. Well name Year drilled

Ground

altitude,

in feet

Well depth,

in feet

Depth of solid 

casing, in feet

2355-04 Aiea Gulch B 1947 304 289 --

2355-05 Aiea Gulch 2 1947 304 344 286

2355-06 Aiea 1 1955 258 360 290

2355-07 Aiea 2 1955 258 358 288

2355-09 Kalauao 1 1965 159 413 221

2355-10 Kalauao 2 1965 159 413 222

2355-11 Kalauao 3 1965 159 413 219

2355-12 Kalauao 4 1965 159 413 221

2355-13 Kalauao 5 1969 159 413 227

2355-14 Kalauao 6 1969 159 413 230

2356-14 Aiea 1899 46 550 --

2356-15 Aiea 1899 46 550 --

2356-16 Aiea 1899 46 550 --

2356-17 Aiea 1899 46 550 --

2356-18 Aiea 1899 46 550 --

2356-19 Aiea 1899 46 550 --

2356-20 Aiea 1899 46 985 --

2356-21 Aiea 1899 46 464 --

2356-22 Aiea 1899 46 470 --

2356-23 Aiea 1899 46 550 --

2356-24 Aiea 1899 46 550 --

2356-25 Aiea 1899 46 550 --

2356-26 Aiea 1899 46 550 --

2356-27 Aiea 1899 46 620 --

2356-28 Aiea 1899 46 550 --

2356-29 Aiea 1899 46 550 --

2356-30 Aiea 1899 46 550 --

2356-31 Aiea 1899 46 550 --

2356-32 Aiea 1899 46 550 --

2356-33 Aiea 1899 46 550 --

2356-34 Aiea 1904 56 955 200

2356-35 Aiea 1904 56 -- --

2356-36 Aiea 1904 56 -- --

2356-37 Aiea 1904 56 707 206

2356-38 Aiea 1904 56 405 58

2356-39 Aiea 1904 56 503 88

2356-40 Aiea 1904 56 510 130

2356-41 Aiea 1904 56 504 76

2356-42 Aiea 1904 56 484 40

2356-44 Aiea 1941 81 100 34

2356-49 Waimalu I-1 1954 102 327 129

2356-50 Waimalu I-2 1955 102 327 127

2356-54 Pearl C C Golf 1966 374 552 395

2356-55 Kaonohi I-1 1966 252 542 289

2356-56 Kaonohi I-2 1966 252 549 296

2356-58 Kaamilo 1 1973 147 340 190

2356-59 Kaamilo 2 1973 148 340 190

2356-60 Waimalu II-1 1975 23 240 100

2356-61 Kaonohi II-1 1975 112 330 190

2356-62 Kaonohi II-2 1975 117 340 200

2356-63 Waimalu II-2 1975 26 240 100

2356-64 Waimalu II-3 1975 20 240 163

2356-65 Kaonohi II-3 1975 112 335 195

2356-70 Kalauao 1987 -- 261 170

2357-21 Waiau 1963 11 167 67

2357-22 Kalauao 1965 7 200 137

2357-23 Kaahumanu I-1 1975 49 230 90

2357-24 Kaahumanu I-2 1975 45 265 125

Appendix B 109
Table B1. Properties of pumped wells in the Pearl Harbor area, Oahu, Hawaii (modified from unpub. digital database, 

2002, Hawaii Commission on Water Resource Management)—Continued.

[--, data not available]

Well no. Well name Year drilled

Ground

altitude,

in feet

Well depth,

in feet

Depth of solid 

casing, in feet

2358-03 Pearl City -- 28 165 --

2358-07 Pearl City Pen 1905 28 197 --

2358-13 Pearl City 1926 30 140 54

2358-14 Pearl City 1926 15 175 --

2358-15 Pearl City 1926 15 180 100

2358-16 Pearl City 1926 15 176 53

2358-17 Pearl City 1926 15 176 63

2358-24 Pearl City 1949 23 120 67

2358-28 Pearl City 1953 15 118 37

2358-36 Pearl City 1954 13 102 52

2358-42 Pearl City 1958 10 110 62

2358-44 Pearl City 1962 14 165 37

2358-48 Pearl City 1969 5 195 123

2358-49 Pearl City 1976 21 125 76

2359-03 Waipahu 1943 97 177 100

2359-05 Waipahu 1953 9 150 57

2359-10 Waipahu 1954 23 100 43

2359-15 Waipahu 1958 9 191 38

2359-17 Waipahu 1958 11 175 60

2359-19 PHNWR NO. 1 -- -- -- --

2400-01 Waipahu I P2 1954 200 355 231

2400-02 Waipahu I P1 1954 200 355 231

2400-03 Waipahu I P3 1969 203 386 254

2400-04 Waipahu I P4 1969 203 386 254

2400-05 Waipahu II-2 1983 207 342 239

2400-06 Waipahu II-1 1983 211 344 241

2400-08 Waipahu II-3 1993 206 340 240

2400-09 Waipahu III-1 1994 318 458 358

2400-10 Waipahu III-2 1994 317 457 357

2400-11 Waipahu III-3 1994 312 455 355

2400-12 Waipahu III-5 1994 314 456 356

2400-13 Waipahu III-4 1995 314 453 353

2400-14 Waipahu II-4 1999 208 360 240

2401-04 Kunia III-1 1995 317 452 352

2401-05 Kunia III-2 1995 316 454 357

2401-06 Kunia III-3 1995 315 460 356

2401-07 Royal Kunia C C 1996 463 570 483

2402-01 Kunia II P1 1969 430 575 460

2402-02 Kunia II P2 1969 430 575 465

2402-03 Kunia II P3 1990 417 610 460

2402-05 Kunia II P4 1996 420 559 459

2451-01 N. Halawa-DOT 1991 1,036 918 835

2455-02 Waimalu 1958 128 206 140

2456-01 Newtown 1 1972 263 500 300

2456-02 Newtown 2 1972 263 500 300

2456-03 Newtown 3 1972 263 500 300

2457-01 Pearl City II-1 1957 267 398 281

2457-02 Pearl City II-2 1957 267 415 281

2457-03 Pearl City II-3 1968 272 423 283

2457-05 Punanani 6 1970 145 444 289

2457-06 Punanani 1 1970 151 458 312

2457-07 Punanani 1970 -- 455 --

2457-08 Punanani 1970 -- 338 --

2457-09 Punanani 2 1970 153 461 312

2457-10 Punanani 4 1970 146 368 217

2457-11 Punanani 3B 1970 141 363 211

2457-12 Punanani 5B 1970 140 367 210

2457-13 Waiau 2 1971 263 504 300

110 Numerical Simulation of the Effects of Valley-Fill Barriers in the Pearl Harbor Area, Oahu, Hawaii
Table B1. Properties of pumped wells in the Pearl Harbor area, Oahu, Hawaii (modified from unpub. digital database, 

2002, Hawaii Commission on Water Resource Management)—Continued.

[--, data not available]

Well no. Well name Year drilled

Ground

altitude,

in feet

Well depth,

in feet

Depth of solid 

casing, in feet

2457-14 Waiau 1 1971 263 503 300

2457-15 Waiau 3 1971 263 503 300

2458-01 Pearl City Shaft 1940 111 151 27

2458-03 Pearl City I-1 1953 120 150 56

2458-04 Pearl City I-2 1953 120 140 58

2458-05 Manana 1 1998 137 277 177

2459-01 Waipahu WP6A,6B -- 40 704 --

2459-02 Waipahu WP6A,6B -- 40 582 --

2459-03 Waipahu WP6A,6B -- 40 739 --

2459-04 Waipahu WP6A,6B -- 40 706 --

2459-05 Waipahu WP6A,6B -- 40 600 --

2459-06 Waipahu WP6A,6B -- 40 700 --

2459-07 Waipahu WP6A,6B -- 40 590 --

2459-08 Waipahu WP6A,6B -- 40 577 --

2459-09 Waipahu WP6A,6B -- 40 707 --

2459-10 Waipahu WP6A,6B -- 40 700 --

2459-11 Waipahu WP6A,6B -- 40 -- --

2459-12 Waipahu WP6A,6B -- 40 -- --

2459-13 Waipahu WP6A,6B -- 40 700 --

2459-14 Waipahu WP6A,6B -- 40 700 --

2459-19 Waipio Hts 2 1964 202 337 234

2459-20 Waipio Hts 1 1964 202 337 234

2459-21 Waipahu 1965 32 456 260

2459-23 Waipio Hts. I-3 1977 200 325 235

2459-24 Waipio Hts. I-4 1977 200 315 235

2500-01 Waipio Hts II-1 1978 416 546 446

2500-02 Waipio Hts II-2 1978 419 560 450

2557-01 Waimano Trng Sch 1941 495 512 472

2557-02 Waimano Trng Sch 1950 495 592 479

2557-03 Pearl City III 1977 620 750 650

2558-10 Waiawa Shaft 1951 150 170 --

2600-02 Kipapa Gulch 1957 297 401 299

2600-03 Mililani III-1 1980 664 814 704

2600-04 Mililani III-2 1979 665 815 705

2603-01 Waikele 1961 745 991 726

2658-01 Waipahu Wp17A 1961 703 805 693

2658-02 Waipahu Wp17B 1961 702 835 716

2659-02 Waipio Hts III-1 1987 571 710 604

2659-03 Waipio Hts III-2 1988 572 700 601

2703-01 Kunia Camp 1 1946 847 976 626

2800-01 Mililani I P1 1968 762 1,012 802

2800-02 Mililani I P2 1968 758 1,008 798

2800-03 Mililani I P3 1972 760 1,022 802

2800-04 Mililani I P4 1975 757 1,008 797

2858-01 Mililani IV 1984 960 1,160 1,030

2858-02 Mililani IV 1985 960 1,160 1,000

2858-03 Mililani IV 1985 960 1,160 1,000

2859-01 Mililani II P1 1978 835 995 875

2859-02 Mililani II P2 1979 835 985 875

Appendix B 111
Prepared by the U.S. Geological Survey Publications staff, 

Menlo Park Publishing Service Center

Luis E. Menoyo

For more information concerning the research in this report, contact the 

Pacific Islands Water Science Center Director, 

U.S. Geological Survey, 677 Ala Moana Blvd., Suite 415 

Honolulu, Hawaii 96813

http://hi.water.usgs.gov/