Availability of Streamflow 

for Recharge of the 

Basal Aquifer in the 

Pearl Harbor Area, Hawaii

GEOLOGICAL SURVEY WATER-SUPPLY PAPER 1999-B

Prepared in cooperation with the 

Board of Water Supply, 

City and County of Honolulu
Availability of Streamflow 

for Recharge of the 

Basal Aquifer in the 

Pearl Harbor Area, Hawaii

By G. T. HIRASHIMA

CONTRIBUTIONS TO THE HYDROLOGY OF THE UNITED STATES

GEOLOGICAL SURVEY WATER-SUPPLY PAPER 1999-B

Prepared in cooperation with the 

Board of Heater Supply, 

City and County of Honolulu

G.

UNITED STATES GOVERNMENT PRINTING OFFICE, WASHINGTON: 1971
UNITED STATES DEPARTMENT OF THE INTERIOR 

ROGERS G. B. MORTON, Secretary

GEOLOGICAL SURVEY 

William T. Pecora, Director

iLlbrary of Congress catalog-card No. 70-&07328

For sale by the Superintendent of Documents, U.S. Government Printing Office 

Washington, D.C. 20402 - Price 25 cents (paper cover)
CONTENTS

Page

Abstract........................................................................................................................ Bl

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

Records available........................................................................................................ 4

Description of the area............................................................................................... 4

Drainage.............................................................................................................. 4

Rainfall................................................................................................................. 4

Ground water................................................................................................................ 6

Basal ground water............................................................................................ 6

Discharge.......................................... .................................................... ..... 6

Runoff............................................................................................................................ 7

Flow duration and regimen of flow.. ........................................................ 7

Mean annual direct runoff.............................................................................. 9

Average annual water loss.............. .......................................................... 14

Seepage losses...................................................................................................... 14

Recharge.........- ...................... ........................................................................ 15

Effect of changes in water use.....--- .......................................................... 15

Availability of streamflow at low altitudes............ ............................. 17

Availability of streamflow at higher altitudes...... .................................. 18

Sedimentation................................................................... ...... ................................ 23

Selected references..- ...... .......... . . ...... ..................................................... 26

ILLUSTRATIONS

Page

FIGURE 1. Map of Oahu showing the study area, its streams, and

lines of equal rainfall for the island ...........................................B3

2. Map of study area showing location of stream-gaging 

stations and the 800- and 400-foot altitudes 

on the streams.................................................................................. 5

3. Graph showing range in percentage of nonzero discharge

days for North Halawa Stream near Aiea................................ 8

4. Graph showing range in Qoo discharges of Kipapa

Stream near Wahiawa................................................................... 8

5-8. Flow-duration curves for:

5. North Halawa Stream near Aiea,

1930-33, 1954-66 fiscal years.......................................... 10

6. Kipapa Stream near Wahiawa,

1958-59, 1961-67 fiscal years................................ 11

7. Waikele Stream near Waipahu,

1958-59, 1961-67 fiscal years.................. .. .......... 12

8. Kipapa Stream stations 2128 and 2129,

December 14, 1966-March 31, 1968........ ............ 16

in
IV CONTENTS

Page

FIGURE 9. Graph showing magnitude and frequency of low

flows on Waikele Stream near Waipahu, 1953-59,

1961-67 fiscal years........................................................................ 17

10. Graph showing magnitude and frequency of low 

flows on Waiawa Stream near Pearl City, 

1953-67 fiscal years...................................................................... 18

11. Estimated long-term flow-duration and duration-area

curves for Kipapa Stream near Wahiawa................................ 21

12. Family of curves showing percentage of streamflow 

in excess of reservoir and diversion capacity for 

Kipapa Stream near Wahiawa.-----..---.-----..... -----.--.....----. .. 22

13. Graph showing the relationship of instantaneous sediment 

discharge to instantaneous water discharge for 

Kipapa Stream near Waipahu..................................................... 25

TABLES

Page

TABLE 1. List of gaging stations on streams entering Pearl IT arbor.......... B4

2. Hydrologic budget for watersheds above selected

gaging stations for 1931-60 ......................................................... 13

3. Ground-water inflow to Waiawa Stream

below gaging station 2160................................................................ 18

4. Estimated average annual runoff at selected altitudes

on streams in the Pearl Harbor area, 1931-60............................ 19

5. Suspended-sediment load for Kipapa Stream near Vaipahu....... 24
CONTRIBUTIONS TO THE HYDROLOGY OF THE 

UNITED STATES

AVAILABILITY OF STREAMFLOW FOR RECHARGE

OF THE BASAL AQUIFER 

IN THE PEARL HARBOR AREA, HAWAII

By G. T. HIRASHIMA

ABSTRACT

The Pearl Harbor area is underlain by an extensive basal aquifer that 

contains large supplies of fresh water. Because of the presence of a cap rock 

composed of sedimentary material that is less permeable than the basaltic 

lava of the basal aquifer, seaward movement of ground water is retarded. 

The cap rock causes the basal water to stand at a high level; thus, the lens 

of fresh water that floats on sea water is thick.

Discharge from the basal ground-water body, which includes pumoage 

from wells and shafts, averaged 250 million gallons per day during 1931-65. 

Because the water level in the basal aquifer did not decline progressively, 

recharge to the ground-water body must have been approximately equal to 

discharge.

Although pumping for agricultural use has decreased since 1931, net 

ground-water discharge has increased because of a large increase in pumping 

for urban use. Substitution of ground water for surface water in the irrigation 

of sugarcane has also contributed to a net increase in ground-water discharge. 

The development of Mililani Town will further increase discharge.

The increase in ground-water discharge may cause an increase in chloride 

content of the water pumped from wells near the shore of Pearl Hrrbor 

unless the increased discharge is balanced by increased recharge to the 1 isal 

aquifer.

The aquifer is recharged by direct infiltration and deep percolation of 

rain, principally in the high forested area, by infiltration and percolation of 

irrigation water applied in excess of plant requirements, by seepage of water 

through streambeds, and possibly by ground-water inflow from outside the 

area. Recharge is greatest in the uplands, where rainfall is heavy and where 

much infiltration takes place before rainwater collects in the middle and lower 

reaches of stream channels. Once water collects in and saturates the allu"ium 

of stream channels, additional inflow to the streams will flow out to sea, only 

slightly decreased by seepage.

Average annual direct runoff from the 90-square-mile Pearl Harbor area 

is 47.27 million gallons per day, or 11.1 inches; this is 13.3 percent of the 

average annual rainfall (83.3 in.) over the area. Average annual direct runoff 

in streams at the 800- and 400-foot altitudes is 29 and 38 million gallons' per 

day, respectively. Kipapa Stream has the largest average annual direct mnoff 

at those altitudes 6 and 9 million gallons per day, respectively.

Bl
B2 CONTRIBUTIONS TO THE HYDROLOGY OF THE UNITED STATES

Because streams are flashy and have a wide range in discharge, only 

60 percent of the average annual runoff can be economically diverted through 

ditches to recharge areas. The diversion may be increased slightly if reservoirs are used in conjunction with ditches to temporarily detain flows in 

excess of ditch capacity.

The planned irrigation use of some of the perennial flow available in 

Waikele Stream near sea level will decrease pumping fron and increase 

recharge to the basal aquifer.

Suspended-sediment load is mainly silt and clay, and it increases rapidly 

with increased discharge. Thus, the use of streamflow for artificial recharge 

poses problems. High flows must be used if recharge is to fee effective, but 

flows must not be so high as to cause clogging of recharge facilities with 

sediment or woodland debris.

Practical tests are needed to determine the advantages and disadvantages 

of different types of recharge structures, such as a reservoir or basin, largediameter deep shafts, deep wells, or combinations of all these structures.

INTRODUCTION

Planned developments in the Pearl Harbor basin indicate a 

need to increase pumping from the basal aquifer, a basaltic lava, 

to meet the growing demand. Mililani Town alone will require 

pumpage greater than 10 mgd (million gallons per day) to supply 

a projected population of 60,000. The first of about 11 required 

water-supply wells for this development was drilled in January 

1968. The increased draft may cause an increase in chloride content of the water pumped from wells near the shore of Pearl Harbor because of sea-water encroachment. The increare in chloride 

content can be minimized if recharge to the basal ground-water 

body is increased.

The purpose of this study was to determine the amount of 

streamflow that might be available for recharging the basal aquifer 

in the Pearl Harbor area. The investigation was limited to those 

streams entering Pearl Harbor.

This report was prepared by the U.S. Geological Survey under 

the direction of Mearle M. Miller, district chief, Water Resources 

Division, as part of a water-resources investigation program under 

cooperative agreement with the City and County of Honolulu, 

Board of Water Supply, George L. Yuen, manager and chief engineer. Acknowledgment is given the Waiahole Water Co., Waialua 

Sugar Co., U.S. Navy, and U.S. Army for their cooperation and 

assistance.

The Pearl Harbor area is defined in this report as the part of 

the island of Oahu bounded by the southern drainage divide of 

South Halawa Stream, the crest of the Koolau Range, the northern drainage divide of Waikakalaua and Waikele Streams, and the 

southwest drainage divide of Waikele Stream (fig. 1).

B4 CONTRIBUTIONS TO THE HYDROLOGY OF THE UNITFD STATES 

RECORDS AVAILABLE

Although current-meter measurements of the flov of water 

into Pearl Harbor have been made since 1911, daily streamflow 

records are available only from 1929. In that year, a gaging station was established on North Halawa Stream. Gaging stations 

that are being or have been operated on streams entering Pearl 

Harbor are listed in table 1, and their locations are shown in 

figure 2.

TABLE 1. List of gaging stations on streams entering Pearl Harbor

Station 

name

Kipapa Stream near Wahiawa............

Kipapa Stream near Waipahu............

Waikele Stream near Waipahu..... ..

Waiawa Stream near Pearl City........

Waimalu Stream near Aiea.. ..............

Kalauao Stream at Moanalua Road

North Halawa Stream near Aiea......

Station 

No.

.. 2128

.. 2129

.. 2130

.. 2160

.. 2230

.. 2245

.. 2260

.. 2270

Drainage area 

(sq mi)

4.29

13.8

45.7

25.4

6.07

2.59

3.45

8.78

Period of 

record 

(fiscal years)

1957-67

1966-67

1951-67

1952-67

1952-67

1957-67

1929-33, 1953-67

1953-62

DESCRIPTION OF THE AREA

DRAINAGE

Five streams draining 89.5 square miles discharge into Pearl 

Harbor. The longest natural waterway, 14 miles long, is formed 

by Waikakalaua Stream and the southern part of Waikele Stream 

(fig. 2). Little or no water is provided to any of the streams by the 

high-level dike-confined ground-water bodies of the Koolau Range; 

the larger streams are perennial in their upper reaches because of 

persistent rainfall in the Koolau highlands. All streams are perennial below an altitude of about 20 feet and are intermittent 

between that altitude and their upper reaches. Infiltration and 

evaporation from the drainage basin are large; therefore, only a 

small fraction of the rain runs off into Pearl Harbor.

RAINFALL

The areal variation of annual rainfall on Oahu is g:~eat. Rainfall ranges from about 20 inches along the leeward coast to about 

300 inches in the north-central part of the Koolau Range (fig. 1).

In the Pearl Harbor area, annual rainfall ranges from between 20 and 30 inches at Pearl Harbor to about 225 inches near 

the crest of the central part of the Koolau Range. Tr^de winds, 

from the northeast, blow two-thirds of the year (Yeh z nd others, 

1951, p. 36). The warm moist air of the trade winds if cooled as 

it rises over the Koolau Range, and rain results. The maximum 

orographic rainfall occurs within 1 mile leeward, or southwest, of 

the crest of the range. Farther to the southwest, orographic rainfall decreases according to a geometric regression (Mink, 1962b).
158°00' 

21' 

30'

21° 

20'

EXPLANATION

A

Stream-gaging station 

and number

800-foot altitude

»...--"+- 

 -T400-foot altitude

Drainage divide

FIGURE 2. Locations of gaging stations and the 800- and 400-foot altitudes on th

and 2280, both outside the report area, were used to extend the records to the 19
B6 CONTRIBUTIONS TO THE HYDROLOGY OF THE UNITED STATES

A cyclonic pattern of air circulation, which causes a more 

uniformly distributed rainfall, occurs about one-fifth of the year 

(Yeh and others, 1951, p. 36). It occurs more frequently in winter 

and provides the bulk of the rain for the dry, leeward ar^as of the 

island. The summers are generally dry.

GROUND WATER

Rainfall is the source of all fresh water on Oahu. Fart of the 

rainfall runs off directly to the sea in streams, part evaporates or 

transpires into the atmosphere, and part moves downward through 

the soil and rocks to become ground water. The ground water 

moves slowly through the rocks and eventually reacher points of 

discharge to streams, to the ocean, or to the atmosphere.

BASAL GROUND WATER

The main water table in the study area stands a few tens of 

feet above sea level. This is the basal water table. Above the basal 

aquifer is a confining layer, locally called the cap rock, composed 

of sedimentary material that is less permeable than the basaltic 

lava of the basal aquifer. The cap rock retards the seaward movement of ground water, and the water stands at a higher level in 

the aquifer than it would if the cap rock were absent. The upper 

part of the basal ground-water body is fresh recharged principally by rainfall in the Koolau Range and the lower part is sea 

water. Because the specific gravity of fresh water is sl'ghtly less 

than that of sea water, the fresh water floats on the sea water as 

a lens-shaped body. The basaltic lavas of the basal aquifer are 

saturated to an unknown depth below sea level. (For a more 

detailed discussion of basal ground water, see "Ground-water Resources in Southern Oahu, Hawaii" by Visher and Mink, 1964.)

DISCHARGE

Water from the basal ground-water body is discharged by 

springs near the shore of Pearl Harbor, by springs and seeps along 

stream channels near sea level, and by pumping from wells and 

shafts. The flow of springs near the shore of Pearl Harbor has 

been measured at gaging stations at or near mean sea level since 

1931. In 1937, some of the gaging stations were discontinued because of changes in flow patterns caused by building construction. 

The flow of some small springs and seeps along stream channels 

can only be estimated; however, the amount of such unmeasured 

water is probably small. Dale (1967) estimated that the total discharge of water from the basal ground-water body averaged 250 

mgd during the years 1931-65.
BASAL AQUIFER, PEARL HARBOR AREA, HAWAII B7

RUNOFF

Runoff from five drainage basins in the Pearl Harbor area is 

measured at seven stream-gaging stations (table 1). Another station was discontinued in 1962. Flow at four of the active stations 

and at the one discontinued station includes some discharge from 

the basal aquifer and some return flow from irrigation of sugarcane. The station on Kipapa Stream near Waipahu (sta. 212?) is 

upstream from the zone of discharge from the basal aquifer. Its 

record of discharge includes only excess irrigation water spilled 

intermittently into the stream above the station. The remaining 

two stations, Kipapa Stream near Wahiawa (sta. 2128) and North 

Halawa Stream near Aiea (sta. 2260), are also upstream from all 

discharges from the basal aquifer, and they record runoff from 

rain only.

FLOW DURATION AND REGIMEN OF FLOW

Streams in the Pearl Harbor area flow generally at right 

angles to the Koolau Range and cut across lines of equal rainfall, 

which are roughly parallel to the range. Thus, rainfall in each 

drainage area is greatest near the headwaters and least at the 

mouths of streams (fig. 1).

A typical stream in the Pearl Harbor area flows only for the 

time it takes for the rain in excess of infiltration capacity tc collect in stream channels and drain out of the valley. Because there 

is little or no valley storage and because there are no perennial 

springs in the headwaters, streams stop flowing a few days after 

the rain stops.

Rainfall in the Koolau Range is most persistent as are the 

trade winds during August. This persistence is reflected in the 

runoff of North Halawa Stream, in the southern part of the area, 

and of Kipapa Stream, in the northern part.

Although North Halawa Stream may have days of no flow 

during any month, the percentage of time of no flow is least during August. This is shown in figure 3, where the percentage of 

time flow equals or exceeds 0.01 mgd is shown on the ordinate 

scale. North Halawa Stream is dry one-third of the time.

The graph (fig. 4) for Kipapa Stream (sta. 2128), which is 

near the region of highest rainfall on Oahu, shows effects of persistent trade-wind rainfall better than does the graph (fig. 3) for 

North Halawa Stream. As shown by the record for both streams, 

June is the driest month of the year.

The flow-duration curve shows the percentage of time, for a 

given period, that any discharge was equaled or exceeded and is 

a useful device for analyzing the availability and variability of 

streamflow.
B8 CONTRIBUTIONS TO THE HYDROLOGY OF THE UNITED STATES

80

75

Si 70

,60

45

July Aug. Sept. Oct. Nov. Dec. Jan. Feb. Mar. Apr. May June

FIGURE 3. Range in percentage of nonzero discharge day? for North 

Halawa Stream near Aiea (sta. 2260).

July Sept. Oct. Nov Dec. Jan. Feb. Mar. Apr. May June

FIGURE 4. Range in Q90 discharges of Kipapa Stream near Wahiawa

(sta. 2128).

The flow-duration curves for North Halawa Stream near Aiea 

(sta. 2260, fig. 5) and for Kipapa Stream near Wahiawa (sta. 2128, 

fig. 6) are typical curves for streams in the Pearl Harbor area. 

Both curves have steep slopes throughout the range of discharges, 

which indicate the absence of perennial storage in the drainage 

areas. Kipapa Stream flows a greater percentage of tirre than does 

North Halawa Stream only because the watershed of Kipapa
BASAL AQUIFER, PEARL HARBOR AREA, HAWAII B9

Stream receives runoff-producing rains a greater percentage of 

time than does the watershed of North Halawa Stream.

The flow-duration curve for Waikele Stream near Waipahu 

(sta. 2130; solid line in fig. 7) for the 1958-59 and 1961-67 fiscal 

years has a steep slope over the range of discharges that are 

equaled or exceeded less than 7 percent of the time and has a 

flatter slope over the range of discharges that are equaled or exceeded more than 7 percent of the time. The flatter slope indicates 

perennial storage in the drainage basin. However, that storage is 

in the basal ground-water body and contributes to streamflow only 

below an altitude of about 30 feet.

Duration curves for other streams that are gaged near sea 

level also show the effect of leakage from the basal ground-vater 

body but to a lesser degree than curves for Waikele Stream, because these streams receive less discharge of ground water. In 

addition to discharge from the basal ground-water body, the flow 

of all streams at low altitudes includes irrigation return flows. 

Some of the streams receive effluent from sewage-treatment plants 

also.

MEAN ANNUAL DIRECT RUNOFF

Watersheds of all streams in the Pearl Harbor area have 

similar rainfall-distribution patterns (fig. 1) and similar geology. 

All streams are dry in the middle and lower reaches during periods 

of little or no rain. Rainfall can be correlated with runoff where 

the streamflow data are collected at altitudes above all inflows 

from sources other than rain. At stations where the streamflow 

includes water from other sources, the records were adjusted by 

eliminating all flow except direct runoff from rain. To do this, relation curves were constructed from the discharges measured at the 

gaging stations and the discharges measured concurrently at sites 

above the spring-inflow zones. The curves were used to estimate 

the shape of the flow-duration curve for direct runoff only. (See 

fig. 7, dashed line.) The area between the curve for total flow and 

the curve for estimated direct runoff was integrated to determine 

the flow contributed by springs and seeps, irrigation return, and 

sewage effluent during the periods of record. This estimated flow 

was then adjusted to the 1931-60 period.

The estimated long-term (1931-60) mean annual direct runoffs and long-term mean annual runoffs of total flow are given in 

table 2. The long-term mean annual runoffs of total flow were 

determined by a series of runoff correlations involving the shortterm records for the stations in the area and the long-term records 

for North Fork Kaukonahua Stream above Right Branch (sta. 

2000, fig. 2) and Moanalua Stream near Honolulu (sta. 2280, fig. 2).
BIO CONTRIBUTIONS TO THE HYDROLOGY OF THE UNITED STATES

1000

100

10

5 1.0

0.1

o.oii *-< in o o o o o o o OQOOOOQ o o ooooo <r

p p « CN « p p pp ppppppp pp ppinoqoi 0

O OOOO'-HCNJ ^ O O OOOOOO O IT) OOC>0^0^O) O

"< tvjmTj-mici^oo o> o> o> o> o> o> o> 5 

PERCENTAGE OF TIME INDICATED DISCHARGE WAS EQUALED OR EXCEEDED

FIGURE 5. Flow-duration curve for North Halawa Str?am near 

Aiea (sta. 2260), 1930-33, 1954-66 fiscal years.
BASAL AQUIFER, PEARL HARBOR AREA, HAWAII Bll

1000

£ 1.0 -

0.01

|2gg§8 8 8 § i 8 8 8 ii.SSS 8j

O OOOO^HCVJtfid OOOOOOO OLOOOO'JO'JO'SO1) O1) 

*"H CXIPO^LO^Or^OO O'JO'JO'JO'JO'JO'SO1) CT1

PERCENTAGE Of TIME INDICATED DISCHARGE WAS EQUALED OR EXCEEDED

FIGURE 6. Flow-duration curve for Kipapa Stream near Wahiawa (sta. 2128), 1958-59, 1961-67 fiscal years.
B12 CONTRIBUTIONS TO THE HYDROLOGY OF THE UNITED STATES

Diversions of surface water for irrigation also affected the 

runoff record. Because the diverted water was used for irrigation 

upstream from the gaging stations, the streamflow past the sta1000

28 S § 88 8 8888885 §8883 §§

d d d ci d - CM" ^ o °°§ggoo g £ g> §>§>§> gj g 

PERCENTAGE OF TIME INDICATED DISCHARGE WAS EQUALED OR EXCEEDED

FIGURE 7. Flow-duration curves for Waikele Stream near Waipahu 

(sta. 2130), 1958-59, 1961-67 fiscal years. Solid line is cur^'e for total 

flow; dashed line is curve for direct runoff only.
TABLE 2. Hydrologic budget (mean annual runoff) for-watersheds abo

[mgd, million gallons per day]

Station 

No.

2270 

2245 

2230 

2160 

2130

Stream

Kalauao... ........ ...

Waimalu.. ...........

Waiawa.. .............

Waikele... ............

Drainage 

area 

(sq mi)

... 8.78

.. 2.59

.. 6.07

..26.4

...45.7

Total or average. 89.54

2260 

2128 

2280

North Halawa... 

Kipapa.. ........... ...

Moanalua... ........

.. 3.45 

.. 4.29

... 2.73

<

 . , Total 

Rainfall flr>w

in.

92 

96 

116 

98 

68

83.3

127 

170 

125

mgd (mgd)

7.55 

1.81 

5.27 

17.0 

25.9

355 57.53

3.72 

6.42 

2.01

Spring inflow 

irrigation 

return, or 

sewage flow 

( mgd )

1.19 

.07 

.60 

2.60 

10.6

15.06

Direct 

runoff 

(mgd) 

6.36 

1.74 

4.67 

14.4 

15.3 

42.47 

3.72 

6.42 

2.01

*No long-term data on diversion available. Average for 1947-62 used. 

2Adjustments for diversion are only one-half of long-term diversion because estimated long-ter

by reduced diversions.
B14 CONTRIBUTIONS TO THE HYDROLOGY OF THE UNITED STATES

tions included some return irrigation water. However, this return 

irrigation water is probably a small part of the total quantity 

measured at the gaging station and was neglected.

Since 1953, diversion of streamflow for irrigation has been 

decreasing, owing to the increased cost of maintenance of ditches 

and diversion works. This decrease in diversion of streamflow has 

been offset by increased pumping of ground water, a less variable 

supply. Adjustment in the computations for diversion was less than 

the long-term average diversion because the decrease in diversion 

was occurring during the 1931-60 base period.

AVERAGE ANNUAL WATER LOSS

Water loss from a drainage basin, defined in terms of surface 

flow, occurs (1) when rain infiltrates the ground and percolates 

to the water table, (2) when water seeps to the water table through 

the streambeds, and (3) when water is evaporated or transpired. 

In this report, the average annual water loss from the drainage 

basins of streams entering Pearl Harbor is defined r.s the difference between the 30-year (1931-60) mean annual rairfall over the 

basins and the 30-year mean annual direct runoff.

The long-term average annual rainfall over the 90 square 

miles of drainage area, as determined from the precipitation map 

(fig. 1), was 83.3 inches, or 355 mgd. Direct runoff (exclusive of 

runoff from basal springs, irrigation return water, and sewage 

effluent) averaged 11.1 inches. Water loss, therefore, was 72.2 

inches, or 308 mgd (table 2). However, it is not known what part 

of the loss is attributable to evapotranspiration and what part to 

infiltration and deep percolation.

SEEPAGE LOSSES

Most deep percolation probably occurs in the upland areas of 

heavy rainfall before water collects in the middle and lower reaches 

of stream channels. The alluvial streambeds are poorl;T permeable. 

Thus, once water collects in the channels and fills all the pools and 

interstices of the alluvium, additional inflow of water will flow out 

to sea, only slightly decreased by seepage.

The discharge records for the gaging station on North Halawa 

Stream near Aiea (sta. 2260) and observations of no flow at the 

confluence of North Halawa Stream with South Halawa Stream 

indicate that at least 5.3 million gallons of water is required to fill 

all the pools and saturate the streambed in the reach between the 

two sites. It is not known how much of the 5.3 million gallons is 

lost in deep percolation during the initial wetting, but measurements made at other times indicate that once the streambed is 

saturated, only small amounts of water seep through the bed of 

North Halawa Stream.
BASAL AQUIFER, PEARL HARBOR AREA, HAWAII B15

Measurements of Kipapa and Waikakalaua Streams show that 

seepage from these streambeds also is small. Because continuous 

records of discharge are more reliable than individual currentmeter measurements, the concurrent records of stations 212.9 and 

2129 on Kipapa Stream are used to show the magnitude of seepage. Duration curves for the two stations are plotted for the period 

of concurrent record, December 14, 1966-March 31, 1968, in figure 

8. The maximum difference between the two curves at low flow, 

which is indicative of the maximum dry-weather seepage between 

the two stations, is about 0.35 mgd. The distance between the two 

stations is 8.2 miles ; therefore, seepage through the bed of Kipapa 

Stream is about 0.04 mgd per mile of stream.

RECHARGE

Dale (1967) estimated that throughout the years 1931-65 the 

discharge of ground water in the Pearl Harbor area averaged 

250 mgd. This large discharge without a progressive lowering 

of the water level in the basal ground-water body suggests that 

recharge to the ground-water body was approximately equal to 

discharge from it.

The basal ground-water body is recharged by direct infiltration 

of rain, principally in the high forested area, by infiltration of 

irrigation water applied in excess of plant requirements, by seepage of water through streambeds, and by possible ground-water 

inflow from outside the area. Estimates of the amount of recharge 

provided by each of the items are beyond the scope of this report. 

Of importance, however, is the amount of the potential infiltration.

The land overlying the basaltic aquifer intake area has a 

loose and porous structure and a high capacity to absorb water. 

Mink (1962a) estimated that 50 to 60 percent of the aggregate 

rainfall and the water applied in the irrigation of sugarcane in the 

Pearl Harbor area returns to the ground-water body.

EFFECT OF CHANGES IN WATER USE

Before 1953, streams supplied an average of 8.6 mgd of the 

irrigation water; and before 1963, the Waiahole Ditch (fg. 2) 

supplied an average of 26.1 mgd of surface water and ground 

water imported from the east side of the Koolau Range. The basal 

aquifer supplied the rest of the irrigation water.

After 1953, diversion of surface water for irrigation decreased 

until, in 1963, only about 1 mgd was diverted. This resulted in a 

decrease of about 4 mgd [0.5X (8.6-1.0)] in recharge. However, 

since 1963, there has been an increase of 5 to 6 mgd of water 

imported from eastern Oahu by way of the Waiahole Ditch. In
B16 CONTRIBUTIONS TO THE HYDROLOGY OF THE UNITED STATES

100

; 2 8 8 § 8 8 8 8888888 8 8 8 § S § §?

o O ci ci o -« CM ,«o o = o g g o o o g g? g §? 8S 8 

PERCENTAGE OF TIME INDICATED DISCHARGE WAS EQUALED OR EXCEEDED

FIGURE 8. Flow-duration curves for Kipapa Stream stations 2128 and 2129, 

December 14, 1966-March 31, 1968.

addition, about 2.2 mgd of the water available in Waikele Stream, 

at the Waiahole Ditch siphon, is pumped into Waiaholo Ditch for 

irrigation. The water available at the siphon is the eff-ient from
BASAL AQUIFER, PEARL HARBOR AREA, HAWAII B17

sewage treatment plants at Schofield Barracks and Waipio Acres 

and the ground water returned to the stream after being used for 

air conditioning by the U.S. Navy. At the present time (1968), 

ground water constitutes the largest part of the water used; however, sewage effluent may be used for irrigation in greater amounts 

in the future. The capacity of the pumps at the siphon is 2,975 

gallons per minute, or 4.3 mgd.

Dale (1967) estimated that, owing to a decrease in pumping 

for agricultural use and an increase in pumping for urban use, 

infiltrated irrigation water decreased by 10 mgd. The result has 

been a net increase in ground-water discharge. The development of 

Mililani Town in the northern part of the area will eventually 

increase ground-water discharge by an additional 10 mgd or more.

AVAILABILITY OF STREAMFLOW AT LOW ALTITUDES

The decrease in the use of surface water for irrigation mentioned previously will be partly offset by the planned use of part 

of the perennial flow of Waikele Stream at the gaging station near 

Waipahu (sta. 2130). The perennial flow, which is contributed 

mainly by the basal ground-water body, averages about 10.6 mgd. 

However, the lowest daily flow recorded during the periods of 

record (1958-59, 1961-67) was 4.4 mgd in 1963.

To show how much water is available for use, low-flow frequency curves for Waikele Stream (sta. 2130) were prepared (fig. 

9). The curves show the lowest mean discharge for 1 day and for 

7 consecutive days. The 3-day minimum is not shown because it 

is nearly the same as the 1-day minimum. Curves for periods

20

00 o

§2

2 10

S 5

Q >-"

Z 2

2 cc

-day

I I I I

RECURRENCE INTERVAL, IN YEARS

FIGURE 9. Magnitude and frequency of low flows on Waikele Stream 

near Waipahu (sta. 2130), 1953-59, 1961-67 fiscal years.
longer than 7 days were not drawn because they would be affected 

by direct runoff from rain during such periods.

The 1-day-minimum curve, which represents the run-of-river 

flow, shows the flow available without storage. The7-dsy-minimum 

curve shows the flow available if some storage is provided.

There is perennial flow also at the gaging station on Waiawa 

Stream (sta. 2160), which can provide an average of 2.6 mgd of 

irrigation water. Figure 10 shows the magnitude and frequency 

of the 1-day- and 7-day-minimum flows at the gag'ng station. 

Measurements made in 1967 and 1968 show that flow increased 

by about 1.5 mgd in the 1,000-foot reach of channel below the 

gaging station. This gain was equivalent to 47 percent of that 

from seeps and springs upstream from the gaging station. (See 

table 3.)

AVAILABILITY OF STREAMFLOW AT HIGHER ALTITUDES

Estimated runoff figures for altitudes of 800 and 400 feet are 

given in table 4. They were estimated from a regression equation

'10

" £

E > o < * 

z o 

< 

7-day

1-day'

 i csj m

RECURRENCE INTERVAL, IN YEARS

FIGURE 10. Magnitude and frequency of low flows on Waiawa Stream 

near Pearl City (sta. 2160), 1953-67 fiscal years.

TABLE 3. Ground-water inflow to Waiawa Stream below gaging station 2160

[Results in million gallons per day]

Discharge

Discharge Ground-water Irrigation- 1,000 feet Ground-water 

above spring- Discharge gain above well below gain below 

Date inflow zone at station station1 discharge station station2

May 12, 1967.............

July 10, 1967.............

Oct. 16, 1967..... ...... ..

Average... ....... ..

...........0.81

...........3.28

........... .75

...........1.46

4.49

6.19

4.06

4.64

3.68

2.91

3.31

3.18

........3.24

0.79

.76

.63

.79

6.78

8.08

6.59

1.13

1.90

1.60

1.53

1Discharge at station minus discharge above spring-inflow zone.

2Discharge 1,000 ft below station minus discharge at station minus irrigation-well discharge.
TABLE 4. Estimated average annual runoff at selected altitudes on strea

[mgd, million gallons per day]

800-foot altitude

Stream

Waikakalaua ...

(Unnamed) . .

Manana..... ... ... ... .........

Waimano2.... ... ... .... ....

Waimalu2 ... ... ... .. ... ... ..

South Halawa.... .......

Total.-..- .

Tributary to

.Waikele....... ............

.Pacific Ocean.... ......

..Kipapa ...............

..Waikele...... ...... 

.....do. ............

.Pacific Ocean... ......

.....do.........................

.....do .......

 do 

.....do..- ..

Drainage 

area 

(sq mi)

-.2.60

.....5.30

....1.91

....3.83

.... .31

.....1.23

.... .98

.....1.71

.... .83

.....2.36

.....1.92

.....1.12

.....1.56

..... .82

Rainfall 

(in.)

158 

51 

127 

180 

140 

190 

180 

167 

140 

158 

164 

141 

146 

124

iDoes not include the estimated difference of 0.5 mgd between the 

2Values for 800-foot altitude represent total of the three headwater

Direct runoff

in.

27.4 

5.8 

20.2 

32.6 

23.1 

35.2 

32.6 

29.5 

23.1 

27.4 

28.8 

23.3 

24.5 

19.5

mgd

3.39 

1.47 

1.84 

5.95 

.34 

2.07 

1.53 

2.40 

.91 

3.08 

2.64 

1.25 

1.81 

.76

29.44

amount available at the Waiaho

streams.
B20 CONTRIBUTIONS TO THE HYDROLOGY OF THE UNITED STATES

computed from the rainfall and direct-runoff figures in table 2. 

The equation is log y 1.37 log x 1.576, where y = direct runoff, in inches, and x = rainfall, in inches. The standard error of 

the estimate is 0.067 log units, or 16.8 percent.

Table 4 shows that at the 800- and 400-foot altitudes the 

mean annual direct runoff is 29 and 38 mgd, respectively. However, the runoff available in any single stream is small, the largest 

being 6 and 9 mgd at the 800- and 400-foot altitudes, respectively, 

in Kipapa Stream.

Because the direct runoffs shown in table 4 are average annual 

figures, they may be fully utilized only if all the flows from low 

flow to flood flow are diverted for use. To show how much of 

the average flow of Kipapa Stream is available if diversion is less 

than total, figure 11 was prepared from the recoH for Kipapa 

Stream near Wahiawa (sta. 2128). The average flow (6.4 mgd) 

at the gaging station at an altitude of 690 feet is nearly equal to 

that of the stream at 800 feet (6.0 mgd).

The estimated long-term flow-duration curve end the duration-area curve for Kipapa Stream (sta. 2128) are shown in figure 

11. The flow-duration curve shows the percentage of time a given 

discharge is equaled or exceeded. The duration-area curve is the 

integral of the flow-duration curve along the flow axis (side scale) 

and shows the average flow available below a given discharge. 

Figure 11 may be used in the following manner. Enter the graph 

at the side scale for example, at 60 mgd. The intersection of the 

60-mgd line and the flow-duration curve indicates that 60-mgd 

flow was equaled or exceeded 1.5 percent of the tiire, as read on 

the bottom scale. Follow the 60-mgd line across the gr^aph to where 

it intersects the duration-area curve. This intersection is read on 

the top scale and indicates that 5.6 mgd is the average of all flows 

less than 60 mgd. The average discharge for the stream at the 

gaging station is 6.42 mgd; therefore, if all flows at and below 60 

mgd are diverted, about 87 percent of the average flow of the 

stream is available. If all flows below 40 mgd are diverted, an 

average of 5.2 mgd, or 81 percent of the average flow of the 

stream, is available.

The foregoing average flows of 5.6 and 5.2 mgd are available 

only if the diversion ditch is large enough to take rll daily flows 

of 60 and 40 million gallons. Such a ditch must have a capacity 

much larger than 60 mgd (or 40 mgd) because of th« large range 

in discharge in a day. If capacity is limited to 60 mgd1 (or 40 mgd) 

the average of the flows diverted will be less than 87 (or less than 

81) percent of the mean annual discharge of the stream.
BASAL AQUIFER, PEARL HARBOR AREA, HAWAII B21

12345

AVERAGE FLOW, IN MILLIONS OF GALLONS PER DAY 

10 20 30 40 50 

PERCENTAGE OF TIME INDICATED DISCHARGE WAS EQUALED OR EXCEEDED

60

FIGURE 11. Estimated long-term flow-duration and duration-area 

curves for Kipapa Stream near Wahiawa (sta. 2128). Flow-duration-curve values are read from the bottom and side scales. 

Duration-area-curve values are read from the top and side scales.
B22 CONTRIBUTIONS TO THE HYDROLOGY OF THE UNITED STATES

3501

Diversion capacity, in millions 

of gallons per day

20 30 40 50 

RATIO OF WATER SPILLED TO RUNOFF, IN PERCENT

FIGURE 12. Family of curves showing percentage of streamflow in excess 

of reservoir and diversion capacity for Kipapa Stre?m near Wahiawa (sta. 2128).

The family of curves shown in figure 12 is based on the 3,468 

daily discharges of Kipapa Stream (sta. 2128) from January 1, 

1957, through June 30, 1966. The curves were computer developed 

for the author by R. H. Dale. They show that the ratio of water 

spilled (water in excess of system capacity) to stream runoff can 

be obtained by combining various reservoir and diversion capacities. For example, the following reservoir-diversion combinations 

will capture all but 19 percent (amount of water spilled) of the
BASAL AQUIFER, PEARL HARBOR AREA, HAWAII B23

average runoff (6.78 mgd) of Kipapa Stream (sta. 2128). The 

average runoff in this example differs slightly from the previous 

example because of a different base period.

Reservoir capacity Diversion capacity 

(million gallons) (mgd)

250........................................................................................................ 1C

80........................................................................................................ 20

20...................................................................................................... 40

0........................................ ........................................................ .

Records of Kipapa Ditch diversions show that before diversions were reduced in 1954, 51 percent of the average annurl flow 

(9.2 mgd) of Kipapa Stream was diverted at the ditch intake. 

Waikakalaua Ditch diverted 65 percent of the average flov (3.5 

mgd) available in Waikakalaua Stream at the ditch intake. The 

average of the two percentages is about 60 percent.

If only 60 percent of the streamflow available in a stream can 

be diverted by a practical ditch under operating conditions, the 

figures of runoff in table 4 should be reduced by 40 percent. The 

water available for recharge then becomes 17.7 and 23.0 mgd at 

the 800- and 400-foot altitudes, respectively.

SEDIMENTATION

Data collected on Kipapa Stream near Waipahu (sta. 2129) 

indicate that the suspended-sediment load is mostly silt and clay 

(table 5). Although the maximum discharge for which samples 

were taken was only 158 mgd, or 245 cubic feet per second, the 

suspended-sediment load for greater flows probably will be composed predominantly of silt and clay.

The desirability of maximum use of flows and minimal clogging of facilities poses a dilemma. As figure 11 shows, to obtain 

an average of 3.0 mgd of recharge water from Kipapa Stream, all 

daily flows below 9.0 mgd must be diverted ; to obtain an average 

of 4.0 mgd, all flows below 17 mgd must be diverted. The increase 

of 1 mgd (from 3 to 4 mgd) in the average diversion is accompanied by a doubling (from 9 to 17 mgd) of the magnitude of the 

daily discharge below which all flows must be diverted. To obtain 

an additional 1 mgd (from 4 to 5 mgd) requires that all flows 

below 34 mgd be diverted. Thus, the magnitude of the daily discharge, below which all flows must be diverted, roughly doubles 

for each increase of 1 mgd in the amount diverted for diversions 

between 1 and 5 mgd.

However, as figure 13 shows, sediment discharge increases 

rapidly with increased water discharge. Thus, the use of surface 

water of the area for recharge poses a conflict. The flashiness of 

streamflow, on the one hand, requires that the flows diverted for
TABLE 5. Suspended-sediment load for Kipapa Stream ne

[Methods of analysis: C, chemically dispersed; P, pipet ; V, visual accumulation tube; W

Date of

collection

Feb. 17, 1967

May 18, 1967

June 30, 1967

July 31, 1967

Aug. 8, 1967

Dec. 18, 1967

Dec. 18, 1967

Dec. 19, 1967

Jan. 5, 1968

Mar. 25, 1968

May 8, 1968

1 Estimated.

Time

(24-

hour)

1030

1400

1045

0945

1145

1005

1240

1025

1225

1510

1105

Water 

temper- _. , 

atiirp Discharge

(°C)

20

26

24

24

24

22

22

21

22

23

mgd

9

3.4

4.6

2.8

25

158

85

16

J130

19

1.2

cfs

5.3

7.1

4.3

39

245

132

24

J 200

30

1.8

Sediment 

concentration

(mg/1)

8

13

11

24

585

300

27

18

3

Sediment 

discharge

day)

0.3

.2

.2

.1

2.5

387

107

1.7

>160

T

Percent of suspen

0.002 0.004 0.0

..........................................

.........................................

34 48 7

39 56 8

. ...... .................................
BASAL AQUIFER, PEARL HARBOR AREA, HAWAII B25

recharge be high enough so that the average volume of recharge 

water will be enough to justify the costs of a recharge project. 

On the other hand, lower flows are desirable to prevent clogging 

of recharge facilities by suspended sediment.

The flow of Kipapa Stream is used for irrigation of sugarcane, 

but the concentration of suspended sediment must be considered 

if the flow is to be used in recharge tunnels, wells, or basins.

1000

100

10

1.0

0.1 1 10 100

INSTANTANEOUS WATER DISCHARGE, IN MILLIONS OF GALLONS PER DAY

1000

FIGURE 13. Relationship of instantaneous sediment discharge to instantaneous water discharge for Kipapa Stream near Waipahu (sta. 

2129).
B26 CONTRIBUTIONS TO THE HYDROLOGY OF THE UNITED STATES

Artificial recharge of Hawaiian aquifers from streamflow has not 

been attempted but appears to be an obtainable and desirable goal. 

Practical tests must be made to provide some of the answers 

needed to design efficient recharge facilities. Unused ditches or 

reservoirs might be excavated or large-diameter shafts or wells 

might be dug to bedrock for recharge testing.

SELECTED REFERENCES

Dale, R. H., 1967, Land use and its effect on the basal water supply, Pearl 

Harbor area, Oahu, Hawaii, 1931-65: U.S. Geol. Survey Hydrol. Inv. 

Atlas HA-267.

Mink, J. F., 1962a, Excessive irrigation and the soils and ground water of 

Oahu, Hawaii: Science, v. 135, no. 3504, p. 672-673.

 1962b, Rainfall and runoff in the Leeward Koolau Mountains, Oahu, 

Hawaii: Pacific Science, v. 16, no. 2, p. 147-159.

Riggs, H. C., 1968, Frequency curves: U.S. Geol. Survey Techniques of WaterResources Inv., book 4, chap. A2, 15 p.

Visher, F. N., and Mink, J. F., 1964, Ground-water resource? in southern 

Oahu, Hawaii: U.S. Geol. Survey Water-Supply Paper 1778, 133 p.

Yeh, T. C., Wallen, C. C., and Carson, J. E., 1951, A study of rainfall over 

Oahu, in On the rainfall of Hawaii: Am. Meteorol. Soc., Meteorol. Mon., 

v. 1, no. 3, p. 34-36.

U. S. GOVERNMENT PRINTING OFFICE : 1971 O - 420-244