U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2012–5264

Prepared in cooperation with the State of Hawaiÿi Department of Hawaiian Home Lands

Availability and Distribution of Low Flow in Anahola 

Stream, Kauaÿi, Hawaiÿi
Cover:

Kalalea Mountains in northeast Kauaÿi, Hawaiÿi. Photographed by Chui Ling Cheng.
Prepared in cooperation with the 

State of Hawaiÿi Department of Hawaiian Home Lands

Scientific Investigations Report 2012–5264

U.S. Department of the Interior

U.S. Geological Survey

Availability and Distribution of Low 

Flow in Anahola Stream, Kauaÿi, 

Hawaiÿi

By Chui Ling Cheng and Reuben H. Wolff
U.S. Department of the Interior

KEN SALAZAR, Secretary

U.S. Geological Survey

Marcia K. McNutt, Director

U.S. Geological Survey, Reston, Virginia: 2012

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Suggested citation:

Cheng, C.L., and Wolff, R.H., 2012, Availability and distribution of low flow in Anahola Stream, 

Kauaÿi, Hawaiÿi: U.S. Geological Survey Scientific Investigations Report 2012-5264, 32 p.

Any use of trade, product, or firm names is for descriptive purposes only and does not imply 

endorsement by the U.S. Government.

Although this information product, for the most part, is in the public domain, it also may contain 

copyrighted materials as noted in the text. Permission to reproduce copyrighted items must be 

secured from the copyright owner.
 iii

Contents

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

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

Purpose and Scope.................................................................................................2

Acknowledgments ...................................................................................................2

Description of the Study Area.........................................................................................4

Physical Setting.......................................................................................................4

Geologic Setting......................................................................................................4

Hydrologic Setting ...................................................................................................7

Groundwater ....................................................................................................7

Historical Streamflow Diversions......................................................................7

Biological Setting.....................................................................................................8

Native Species .................................................................................................9

Nonnative Species ...........................................................................................9

Streamflow Characteristics...........................................................................................12

Anahola Stream Under Regulated Flow Conditions..............................................14

Study-Area Streams Under Natural Flow Conditions ............................................15

Natural Low-Flow Availability..........................................................................16

Low-Flow Partial-Record Stations...........................................................17

Selection of Index Stations .....................................................................21

Record-Augmentation Techniques ..........................................................21

Low-Flow Duration Discharges ...............................................................22

Natural Low-Flow Distribution ........................................................................24

Seepage Runs ........................................................................................24

Streamflow Availability Scenarios .........................................................................28

Limitations of Approach................................................................................................29

Summary and Conclusions ..........................................................................................30

References Cited..........................................................................................................31

Figures

 1. Map showing Anahola and Goldfish Streams study area.......................................3

 2. Map showing diversion systems, streamflow and ditch-flow gaging stations 

in the Anahola and Goldfish Streams study area .............................................5

 3. Map showing general geology of the study area....................................................6

 4. Map showing locations of stream reaches surveyed and the distribution of 

selected native aquatic species observed during the 2011 U.S. Geological 

Survey biological surveys in Anahola Stream.................................................10

 5. Map showing locations of stream reaches surveyed and the distribution 

of selected nonnative aquatic species observed during the 2011 

U.S. Geological Survey biological surveys in Anahola Stream .......................13

 6. Plot showing annual mean discharges at streamflow-gaging station 

16089000 on Anahola Stream for water years 

with complete record during 1913–1985.........................................................14
iv

 7. Plot showing mean monthly discharges at streamflow-gaging station 

16089000 on Anahola Stream for water years 

with complete record during 1913–1985.........................................................14

 8. Plot showing flow-duration curves for total flow and base flow 

at streamflow-gaging station 16089000 on Anahola Stream 

for water years with complete record during 1913–1985 ................................15

 9. Plot showing annual mean discharges at streamflow-gaging station 

16093200 on Anahola Stream for water years 

with complete record during 1966–1982.........................................................15

10. Plot showing mean monthly discharges at streamflow-gaging station 

16093200 on Anahola Stream for water years 

with complete record during 1966–1982.........................................................16

11. Plot showing flow-duration curves for total flow and base flow 

at streamflow-gaging station 16093200 on Anahola Stream 

during 1966–1982...........................................................................................16

12. Photographs of low-flow partial-record stations in Anahola 

and Goldfish Streams .....................................................................................17

13. Map showing discharge-measurement stations in the Anahola and Goldfish 

Streams study area.........................................................................................19

14. Plot showing flow-duration curves for total flow and base flow 

at streamflow-gaging station 16097500 on Halaulani Stream 

during 1961–2011...........................................................................................24

15. Plot showing flow-duration curves for total flow and base flow 

at streamflow-gaging station 16071500 on left branch 

ÿÖpaekaÿa Stream during 1961–2011.............................................................24

16. Maps showing results of seepage runs on Anahola Stream, 

April and September 2011..............................................................................26

17. Photograph of raised gravel bed on the right bank immediately 

upstream of seepage-run measurement station 220854159210601 

on Anahola Stream .........................................................................................28

18. Plot showing flow-duration curves indicating the amount of flow available 

for agricultural use at the Upper Anahola Ditch diversion intake, 

based on data for water years 1961–2011 under a variety of potential 

instream-flow standards. ...............................................................................29
 v

Tables

 1. Locations and lengths of stream reaches where biological surveys were 

conducted by the U.S. Geological Survey in Anahola Stream, 2011 ................8

 2. Species observed during U.S. Geological Survey biological surveys 

of Anahola Stream, 2011 ................................................................................11

 3. Selected flow-duration discharges for total streamflow at streamflow-gaging 

stations 16089000 and 16093200 on Anahola Stream...........................................15

 4. Altitude and latitude and longitude coordinates of low-flow partial-record 

and seepage-run discharge-measurement stations in the Anahola 

and Goldfish Streams study area ...................................................................18

 5. Measured discharges at low-flow partial-record station 16085500 

on Anahola Stream upstream of upper ditch intake and concurrent 

daily mean discharges at streamflow-gaging station 16097500 

on Halaulani Stream .......................................................................................20

 7. Measured discharges at low-flow partial-record station 16088500 

on Keaÿoÿopu tributary near Anahola Stream confluence 

and concurrent daily mean discharges at streamflow-gaging station 

16071500 on left branch ÿÖpaekaÿa Stream............................................................20

 6. Measured discharges at low-flow partial-record station 16088300 

on Anahola Stream near Keaÿoÿopu tributary confluence 

and concurrent daily mean discharges at streamflow-gaging station 

16097500 on Halaulani Stream ......................................................................20

 8. Combined discharges measured at low-flow partial-record station 16088300 

on Anahola Stream near Keaÿoÿopu Stream confluence and low-flow 

partial-record station 16088500 on Keaÿoÿopu Stream near Anahola Stream 

confluence, and concurrent daily mean discharges at streamflow-gaging 

station 16097500 on Halaulani Stream......................................................................20

 9. Measured discharges at low-flow partial-record station 16081500 on Goldfish 

Stream and concurrent daily mean discharges at streamflow-gaging station 

16071500 on left branch ÿÖpaekaÿa Stream ...................................................21

10. Index stations, record-augmentation technique, and selected 

regression statistics for the low-flow partial-record stations 

in Anahola and Goldfish Streams ...................................................................23

11. Selected flow-duration discharges at the index stations 

and estimated flow-duration discharges at the low-flow 

partial record stations for water years 1961–2011..........................................23

12. Wet-season and dry-season seepage-run discharge measurements 

of Anahola Stream..............................................................................................25
Conversion Factors

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 0.004047 square kilometer (km2

)

square foot (ft2) 0.09290 square meter (m2

)

square mile (mi2) 2.590 square kilometer (km2) 

Volume

gallon (gal) 0.003785 cubic meter (m3

) 

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

)

cubic foot (ft3) 0.02832 cubic meter (m3) 

Flow rate

cubic foot per second (ft3/s) 0.64636 million gallons per day (Mgal/d)

gallon per day (gal/d) 0.003785 cubic meter per day (m3

/d)

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

/s)

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

Slope

foot per mile (ft/mi) 0.1895 meter per kilometer (m/km)

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 relative to local 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.

vi
Availability and Distribution of Low Flow in 

Anahola Stream, Kauaÿi, Hawaiÿi

By Chui Ling Cheng and Reuben H. Wolff

Abstract

Anahola Stream is a perennial stream in northeast 

Kauaÿi, Hawaiÿi, that supports agricultural, domestic, 

and cultural uses within its drainage basin. Beginning in 

the late 19th century, Anahola streamflow was diverted 

by Makee Sugar Company at altitudes of 840 feet 

(upper intake) and 280 feet (lower intake) for irrigating 

sugarcane in the Keälia area. When sugarcane cultivation 

in the Keälia area ceased in 1988, part of the Makee 

Sugar Company’s surface-water collection system 

(Makee diversion system) in the Anahola drainage basin 

was abandoned. In an effort to better manage available 

surface-water resources, the State of Hawaiÿi Department 

of Hawaiian Home Lands is considering using the 

existing ditches in the Anahola Stream drainage basin to 

provide irrigation water for Native Hawaiian farmers in 

the area. To provide information needed for successful 

management of the surface-water resources, the U.S. 

Geological Survey investigated the availability and 

distribution of natural low flow in Anahola Stream and 

also collected low-flow data in Goldfish Stream, a stream 

that discharges into Kaneha Reservoir, which served as a 

major collection point for the Makee diversion system.

Biological surveys of Anahola Stream were 

conducted as part of a study to determine the distribution 

of native and nonnative aquatic stream fauna. Results 

of the biological surveys indicated the presence of the 

following native aquatic species in Anahola Stream: 

ÿoÿopu ÿakupa (Sandwich Island sleeper) and ÿoÿopu 

naniha (Tear-drop goby) in the lower stream reaches 

surveyed; and ÿoÿopu näkea (Pacific river goby), ÿoÿopu 

nöpili (Stimpson’s goby), and ÿöpae kalaÿole (Mountain 

shrimp) in the middle and upper stream reaches surveyed. 

Nonnative aquatic species were found in all of the 

surveyed stream reaches along Anahola Stream.

The availability and distribution of natural low 

flow were determined using a combination of discharge 

measurements made from February 2011 to May 2012 

at low-flow partial-record and seepage-run stations 

established at locations of interest along study-area 

streams. Upstream of the upper intake, the estimated 

natural (undiverted) median flow in Anahola Stream is 

2.7 million gallons per day, and the flow is expected to 

be greater than or equal to 0.97 million gallons per day 

95 percent of the time. About 0.7 mile upstream of the 

lower intake and downstream from the confluence with 

Keaÿoÿopu Stream, the estimated natural (undiverted) 

median flow in Anahola Stream is 6.3 million gallons per 

day, and the flow is expected to be greater than or equal 

to 2.7 million gallons per day 95 percent of the time. In 

Goldfish Stream, about 0.4 mile upstream from the point 

of discharge into Kaneha Reservoir, the estimated natural 

median flow is 0.54 million gallons per day, and the flow 

is expected to be greater than or equal to 0.23 million 

gallons per day 95 percent of the time. The discharge 

estimates are representative of low-flow conditions in the 

study-area streams, and they are applicable to the base 

period (water years 1961–2011) over which they have 

been computed.

The distribution of natural low flow in Anahola 

Stream was characterized through data collected during 

wet- and dry-season seepage runs. Seepage-run results 

show that Anahola Stream was generally a gaining stream 

under natural low-flow conditions. During the wetseason seepage run, Anahola Stream at the station located 

upstream of tributary Kaÿalula Stream had more than 

five times the flow that was measured upstream from the 

upper intake. The estimated total gain (including tributary 

inflow) in the 6.1-mile seepage-run reach was 6.97 

million gallons per day; about 42 percent of that gain was 

groundwater discharge to the main channel of Anahola 

Stream. During the dry-season seepage run, about 34 

percent of the estimated total gain of 3.93 million gallons 

per day in the same seepage-run reach was groundwater 

discharge to the main channel of Anahola Stream. A 

15-percent seepage loss was estimated in a 0.3-mile 

reach downstream from the confluence of Anahola and 

Keaÿoÿopu Streams.

The report summarizes scenarios that describe (1) 

surface-water availability under regulated conditions 

of Anahola Stream if the upper and lower intakes are 

restored in the future; and (2) amount of flow available 

for agricultural use at the upper intake under a variety of 

potential instream-flow standards that may be established 

by the State of Hawaiÿi for the protection of instream uses.
Introduction

The surface-water resources of the Anahola Stream 

drainage basin in northeast Kauaÿi, Hawaiÿi (fig. 1), are 

important for agricultural, domestic, and cultural purposes. 

Anahola was designated by the Land Act of 1895, which allowed 

Crown lands to be leased or sold, for Native Hawaiian settlement 

to promote homestead farming as a means for preserving the 

Native Hawaiian culture (State of Hawaiÿi Department of 

Hawaiian Home Lands, 2010). In the late 19th century, Makee 

Sugar Company began diverting surface water from Anahola 

Stream for the irrigation of sugarcane in the Keälia area. The 

Makee Sugar Company’s surface-water collection system 

(hereafter referred to as the Makee diversion system) consisted 

of a network of ditches and reservoirs in the Anahola and Kapaÿa 

drainage basins, and depended primarily on Anahola and Keälia 

Streams for irrigation water (fig. 2). By the early 1900s, the 

Makee diversion system delivered an average of 30 million 

gallons per day (Mgal/d) of water and included several reservoirs 

with a combined capacity of 700 million gallons (Mgal). When 

Makee Sugar Company was acquired by Lïhuÿe Plantation 

Company in 1933, they were cultivating 7,200 acres with an 

additional 2,200 acres cultivated primarily by homesteaders 

in the Anahola and Keälia areas (Wilcox, 1996, p. 73). Lïhuÿe 

Plantation ceased sugarcane cultivation in Anahola and Keälia in 

1988—thereby abandoning some parts of the Makee diversion 

system (Souza and others, 1996).

Presently, the State of Hawai‘i Department of Hawaiian 

Home Lands (DHHL) owns half of the Anahola Stream 

drainage basin, and the remaining part—mostly unirrigated 

lands in the upslope areas—is owned by the State of Hawai‘i 

and managed by the State of Hawai‘i Department of Land 

and Natural Resources (DLNR). Part of the Makee diversion 

system that is located in the Anahola Stream drainage basin 

and that diverted water from Anahola Stream is abandoned. 

However, area residents have developed their own systems 

for diverting surface water from the lower reaches of Anahola 

Stream for agricultural, domestic, and cultural uses. Anahola 

remains an important homestead area and has more Native 

Hawaiians than any other area on the Island of Kauaÿi (State of 

Hawaiÿi Department of Hawaiian Home Lands, 2010).

The DHHL is interested in using part of the Makee 

diversion system in the Anahola Stream drainage basin to 

provide irrigation water for Native Hawaiian farmers in the 

area. In managing water resources, the DHHL utilizes a 

watershed approach that accounts for the stream ecosystem 

and water demands of the downstream users. To provide 

information needed for water-management decisions, the U.S. 

Geological Survey (USGS), in cooperation with the DHHL, 

investigated the availability and distribution of low flow and 

the distribution of aquatic fauna in Anahola Stream. Low-flow 

data were also collected from an unnamed stream that flows 

into Kaneha Reservoir. For the purposes of this study, this 

unnamed stream is referred to as Goldfish Stream, a name 

commonly used by area residents.

Purpose and Scope

The objectives of this study are to (1) quantify the 

availability of surface water in Anahola Stream and Goldfish 

Stream under low-flow conditions upstream of surface-water 

diversions; (2) characterize the distribution of low flow 

along Anahola Stream downstream of the diversions; and (3) 

determine the distribution of native and nonnative aquatic 

fauna in Anahola Stream. A majority of the field work for 

this study is focused on Anahola Stream. This study does 

not evaluate the hydraulic condition of the Makee diversion 

system or the reservoirs that are part of that diversion system.

The first two objectives of this study were achieved by 

analyzing historical and current flow data at continuous-record 

streamflow- and ditch-flow gaging stations, and additional data 

collected as part of this study, including (1) 10 to 12 discharge 

measurements at four low-flow partial-record (LFPR) stations 

established upstream from points of surface-water diversions; 

and (2) two sets of seepage-run discharge measurements at 

selected sites along Anahola Stream. The third objective was 

accomplished through reconnaissance-level biological surveys 

that documented the presence and absence of aquatic species 

and number of aquatic species found in Anahola Stream.

Acknowledgments

The authors acknowledge the State of Hawaiÿi DHHL and 

members of the Anahola community for their understanding 

and support throughout this study. Stephen “Haku” Rivera, Jeff 

Rivera, Frank Rivera, Sr., John Pia, Harold Ano, Canen Hoÿokano, 

and Frank Cummings were among the community members 

that shared information on the Makee diversion system and 

provided a historical perspective of the Anahola area during the 

plantation era. The authors appreciate access to homestead lands 

provided by Frank Rivera, Sr., and Harold Ano. Frank Rivera, 

Jr., and Frank Rivera, Sr., were most generous with their time as 

they accompanied USGS personnel during the reconnaissance 

survey and guided them to the safest hiking trails for accessing 

the streams. The authors are indebted to Kaipo Duncan and Frank 

Cummings for their help during difficult situations encountered 

while driving along the rugged roads of Anahola Valley.

This study could not have been completed without the 

assistance of an experienced group of USGS personnel. 

Benjamin H. Shimizu expertly selected and made dischargemeasurement sections and conducted discharge measurements 

during the study. He also served as a mentor to the first author 

for all field activities. Richard B. Castro, Clarence L. Edwards, 

Melia K. Iwamoto, and Adam G. Johnson helped with 

streamflow measurements and other field-related activities. 

Bobbie L. Arruda helped conduct the biological surveys 

and assisted with data management. Finally, the authors are 

grateful to Scot K. Izuka for sharing his knowledge on the 

geology of the study area, and Delwyn S. Oki and Richard A. 

Fontaine for their support and guidance in project design and 

report preparation.

2 Availability and Distribution of Low Flow in Anahola Stream, Kauaÿi, Hawaiÿi
Figure 1. Map showing Anahola and Goldfish Streams study area, Kauaÿi, Hawaiÿi.

Waimea

District

Hanalei

District

Köloa

District

Lïhuÿe

District

Kawaihau

District

Näpali Coast

Anahola

Stream

drainage

basin

Goldfish

Stream

drainage

basin

Hanalei

Bay

WAIMEA

CANYON

50

35

80

65

25

100

140

180

220

260

300

340

35

50

50

35

80

65

25

100

140

180

220

260

300

340

35

50

159°20'

159°30'

159°40'

22°0'

22°10'

Niÿihau

Oÿahu Molokaÿi

Länaÿi

Kahoÿolawe

Kauaÿi

Maui

HAWAIIAN

ISLANDS

PACIFIC OCEAN

Hawaiÿi

16097500

50

Study area

Judicial-district boundary

Line of equal mean annual rainfall – 

 Contour interval, in inches, is variable (modified from Giambelluca and others, 2011)

Streamflow-gaging station and number –

 Stations were active from February 2011 to May 2012

Mount Waiÿaleÿale

16097500

16103000

16108000

16071500

16068000

16060000

16048000

16036000

16019000

16010000

16097500

16103000

16108000

16071500

16068000

16060000

16048000

16036000

16019000

16010000

EXPLANATION

Kawaikini Peak

0 3 6 MILES

0 3 6 KILOMETERS

Base modified from 

U.S. Geological Survey digital data. 

Universal Transverse Mercator projection,

zone 4, North American Datum 1983.

Introduction 3
Description of the Study Area

Physical Setting

Kauaÿi is the fourth-largest (553 square miles, mi2) and one 

of the oldest of the eight major Hawaiian Islands. The 

topography of the island ranges from coastal beaches and the 

2,700-foot (ft) sea cliffs of the Näpali Coast in the northwest to 

the highest altitude of 5,243 ft above sea level at Kawaikini Peak, 

a mile south of Mount Waiÿaleÿale (fig. 1). The distribution of 

rainfall on the Island of Kauaÿi is controlled by orographic 

effects. Orographic rainfall occurs when northeasterly trade 

winds lift moist air up the windward slopes of the island to 

higher altitudes where the air is cooled, clouds are formed, and 

rainfall is generated. Due to the orographic effects, drier air 

descends down the leeward slopes of the mountains, resulting in 

decreased rainfall in those areas. Rainfall varies greatly 

throughout the island, ranging from less than 25 inches per year 

(in/yr) on the southwestern coast to more than 340 in/yr at 

Mount Waiÿaleÿale (Giambelluca and others, 2011). This extreme 

rainfall variability contributed to the dramatic evolution of the 

island’s landscapes. The abundant rainfall and resulting 

streamflow has carved large valleys such as the 14.5-mile (mi) 

long Waimea Canyon with depths reaching 2,750 ft in some 

places (Stearns, 1966).

Covering an area of about 10.7 mi2, the study area 

encompasses the drainage basins of Anahola Stream and 

Goldfish Stream, both of which lie on the northeastern or 

windward side of the Island of Kauaÿi in the district of 

Kawaihau (fig.1). The study area is bordered on the east by the 

coastline of Anahola Bay, on the north by a mountain ridge that 

extends from the Kalalea Mountains to Namahana Mountains, 

and on the west-southwest by the Makaleha Mountains. The 

southern boundary of the study area runs nearly parallel to 

Kaneha Ditch, which is part of the Makee diversion system 

(fig. 2). Mean annual rainfall in the study area ranges from 

about 140 inches at the headwaters to less than 50 inches near 

the coast (Giambelluca and others, 2011) (fig. 1). 

The Anahola Stream drainage basin is the larger of the two 

basins in the study area and occupies an area of about 10.1 mi2. 

Anahola Stream is a perennial stream that flows in an easterly 

direction for 11.8 mi from its headwaters in the upper slopes 

of the Namahana Mountains to Anahola Bay (fig. 2). Near the 

mouth of Anahola Stream is an estuary that extends about threequarters of a mile inland from the Pacific Ocean. The major 

tributaries to Anahola Stream include the Keaÿoÿopu Stream, 

Kaupaku Stream, and Kaÿalula Stream that join the main channel 

4.4, 1.8, and 1 mi upstream of the estuary, respectively. From the 

headwaters at an altitude of 2,450 ft to a waterfall at an altitude 

1,050 ft, Anahola Stream flows through a relatively steep valley, 

descending 1,400 ft over its first 3.3 mi of stream length at an 

average slope of 420 feet per mile (ft/mi). Downstream of the 

waterfall to its confluence with Keaÿoÿopu Stream, Anahola 

Stream flows through a wider valley at an average slope of 190 

ft/mi. The remaining 4.4 mi of the stream (excluding the length 

of the estuary) is wide and flows on a relatively flat terrain with 

several deep pools along its course to the ocean. 

A majority of the Anahola Stream drainage basin 

supports alien forests and grasslands. Among the more 

prominent alien plant species are Psidium guajava (guava), 

Albizia falcataria (Molucca albizia), and Caesalpinia 

decapetala (cat’s-claw). The guava and Molucca albizia trees 

are mostly found in the intermediate to upper slopes, whereas 

the cat’s-claw is more common in the lower slopes of the 

drainage basin above Kühiö Highway (fig. 2). Native forests 

and wetlands are limited to the headwaters and parts of the 

valley walls surrounding Keaÿoÿopu Stream. The former 

sugarcane lands located in the center of Anahola Valley, 

currently owned by the DHHL, are under interim month 

to month leases and are used primarily for raising cattle. 

Below Kühiö Highway and extending outside of the studyarea boundary are residential lots; DHHL plans to develop 

additional residential and agricultural lots in this area (State 

of Hawaiÿi Department of Hawaiian Home Lands, 2010).

The Goldfish Stream drainage basin has an area of 0.6 

mi2 that consists of a network of four tributaries that flow 

into the main channel (fig. 2). The main channel of Goldfish 

Stream flows in an easterly direction for 1.8 mi before 

discharging into Kaneha Reservoir. About 0.3 mi upstream 

from the reservoir is a small waterfall. From its headwaters 

at an altitude of 1,350 ft, the stream descends about 350 ft 

over its first 0.6 mi of stream length at an average slope of 

580 ft/mi. Over the remaining 1.2 mi of its course, the stream 

gradually descends 120 ft to the reservoir. Land cover in this 

drainage basin is mainly alien forests and shrub lands.

Geologic Setting

Most of Kauaÿi was built by basaltic shield volcanism in 

the Pliocene. A long period of volcanic inactivity followed the 

end of shield volcanism; during this time, faulting and erosion 

created valleys, deep canyons, and other large depressions. 

Subsequent rejuvenated volcanism, mostly during the late 

Pliocene and Pleistocene, partially filled the depressions in the 

original volcano, including the valleys in Anahola (Macdonald 

and others, 1960; Stearns, 1966; Sherrod and others, 2007).

The volcanic rocks in Anahola are divided into two 

units of formational rank: the Waimea Canyon Basalt and the 

Köloa Volcanics (Langenheim and Clague, 1987; Sherrod 

and others, 2007). The Waimea Canyon Basalt was formed 

by shield volcanism that built the bulk of the island and 

the basement on which younger lavas lie. The predominant 

unit of the Waimea Canyon Basalt in Anahola is the Näpali 

Member, which consists of thin-bedded aa and pähoehoe 

flows (Macdonald and others, 1960). The Köloa Volcanics 

was formed during the rejuvenated stage of volcanic activity 

and primarily consists of massive flows and pyroclastic 

deposits intercalated with sediments (Macdonald and others, 

1960; Sherrod and others, 2007).

4 Availability and Distribution of Low Flow in Anahola Stream, Kauaÿi, Hawaiÿi
500

100

1000

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2000

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3000

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Anahola

Bay

KalaleaMountains

NamahanaMountains

MakalehaMountains

16089000

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Anahola

Kühiö Highway

16087000

16086000

16088000

16093200

Lower Anahola

Upper Anahola Reservoir

Lower Anahola Reservoir

Kaneha Reservoir

Field 1 Kealia Reservoir 

Field 2 Kealia Reservoir 

Unnamed Reservoir 

Anahola Str

Keälia Ditch

Kapaÿa

Keälia

16092000

16091000

KeaÿoÿopuStr

Anaho al Str

Ka

aÿ ul al Str

KaupakuStr

Goldfish

Str

Upper Anahola

Kaneha Ditch

Keälia

Str

Kapaÿa Str

500

Anahola Stream drainage basin

Goldfish Stream

drainage basin

PACIFIC

OCEAN

Island of Kauaÿi

Map

area

Study-area drainage basinsLine of equal elevation relative to mean sea level –

Contour interval, in feet, is variable

Makee diversion system near study areaStreamflow-gaging station and numberDitch-flow gaging station and number

10

EXPLANATION

1608900016090000

0 2 1 MILES0 2 1 KILOMETERS

Base modified from U.S. Geological Survey digitaldata. Universal Transverse Mercator projection,zone 4, North American Datum 1983.

159°18' 159°21' 159°24'

22°9'22°7'

Figure 2. Map showing diversion systems, streamflow and ditch-flow gaging stations in the Anahola and Goldfish Streams study area, Kauaÿi, Hawaiÿi. (Reservoir names from State of Hawaiÿi, 2012.)

Description of the Study Area 5
PAC IF IC

OCEAN

ISLAND OF KAUAÿI

Map area

Näpali

Coast

Mount Waiÿaleÿale

Anahola Aquifer

System

Boundary o f Lïhuÿe Basin

0720-02

0720-01

0719-01

0719-02

4

1019-02

1020-01

3

Anahola Stream drainage basin

Goldfish Stream

drainage basin

Anahola

Bay

Namahana

Mountains

Kalalea

Mountains

Makaleha Mountains

Anahola

159°18' 159°21' 159°24'

22°12'

22°9'

Study areaReservoirSedimentary DepositsKöloa VolcanicsWaimea Canyon Basalt – 

Näpali Member

DikesTunnel and numberTest hole and number

EXPLANATION

4

0

Base modified from U.S. Geological Survey digital data. Universal Transverse Mercator projection, zone 4, North American Datum 1983.

2 1 MILES

0 2 1 KILOMETERS

Figure 3. Map showing general geology of the study area, Kauaÿi, Hawaiÿi (modified from Macdonald and others, 1960; Sherrod and others, 2007). Anahola aquifer system boundary delineated by State of Hawaiÿi Commission on Water Resource Management (2008).

6 Availability and Distribution of Low Flow in Anahola Stream, Kauaÿi, Hawaiÿi
The Anahola Stream drainage basin is formed mainly 

by Köloa Volcanics overlying Waimea Canyon Basalt (fig.3). 

Along the Kalalea Mountains and Namahana Mountains 

in the northern drainage-basin boundary and the Makaleha 

Mountains near the headwaters of Anahola Stream are 

outcrops of the Waimea Canyon Basalt (Näpali Member). 

Sedimentary deposits—principally gravel, sand, and silt—are 

concentrated in the lower parts of the drainage basin near 

the estuary, although some of the older alluvium deposits 

are found between altitudes of 500 to 1,200 ft. The Goldfish 

Stream drainage basin is formed by Köloa Volcanics overlying 

Waimea Canyon Basalt. Older alluvium sedimentary deposits 

line a majority of the stream length (Macdonald and others, 

1960; Sherrod and others, 2007).

Hydrologic Setting

Groundwater

In Hawai‘i, fresh groundwater commonly occurs in 

a freshwater-lens system in which a lens-shaped body of 

freshwater floats on underlying, denser saltwater originating 

from the Pacific Ocean. A zone of brackish water forms 

where the freshwater and saltwater mix. Groundwater in a 

freshwater-lens system can discharge to the ocean and to 

streams and springs where the water table intersects the land 

surface. In places where the water table is below the stream 

channel, water that infiltrates moves downward to recharge 

the aquifer. Freshwater can also occur in a dike-impounded 

or perched system. A dike-impounded system is created 

when tabular sheets of low-permeability volcanic rocks (or 

dikes) intrude other rocks, usually in rift zones and calderas 

of a volcano. These dikes impede the horizontal movement 

of groundwater; and where they compartmentalize the more 

permeable rocks, the water level within the permeable layers 

can be elevated substantially. Perched-groundwater systems 

are created where low-permeability strata, such as weathered 

soil, ash, sedimentary deposits, or dense lava flows, impede 

the downward movement of water.

Information on the hydrogeology of the Island of Kaua‘i 

is very limited compared with the existing research available 

for the more developed areas on O‘ahu. Izuka and Gingerich 

(2003) studied the complex hydrogeologic characteristics of 

the southern Lïhuÿe Basin (fig. 3), which is characterized by 

a large region of massive and dense low-permeability (low 

hydraulic conductivity) Köloa Volcanics interbedded with 

sediment, overlying high-permeability Waimea Canyon Basalt. 

The effect of the low-permeability lava flows paired with the 

wet climate of the area creates a thick freshwater lens with 

steep hydraulic gradients, causing water levels to rise to the 

land surface where groundwater is discharged to springs and 

streams. As a result, perennial streams within the southern 

Lïhuÿe Basin are supported by substantial amounts of base 

flow or groundwater discharge.

Anahola Stream and Goldfish Stream lie in the Anahola 

aquifer system, which has similar rainfall and geologic 

characteristics as the southern Lïhuÿe Basin. Records at test 

holes 0720-01 and 0720-02 near the easternmost end of 

the Makaleha Mountains, and test hole 1020-01 at the base 

of the Kalalea Mountains (fig. 3) show steep vertical and 

horizontal groundwater hydraulic gradients (Macdonald and 

others, 1960) that are consistent with a low-permeability (low 

hydraulic conductivity) aquifer like that found in the southern 

Lïhuÿe Basin. Several dikes intrude the Waimea Canyon Basalt 

(Näpali Member) along the southern slopes of the Kalalea 

Mountains (Sherrod and others, 2007). These dikes most likely 

do not impound groundwater to levels that reach the land 

surface because the small tributaries flowing from the ridge 

to Anahola Stream are intermittent. Although no other dikes 

have been identified within the study area, the many perennial 

streams flowing from the Makaleha Mountains suggest 

that dike-impounded groundwater most likely occurs in the 

Waimea Canyon Basalt at the headwaters of Anahola Stream.

Historical Streamflow Diversions

Since 1877 when sugarcane was cultivated in the 

Anahola and Keälia areas, Anahola streamflow was diverted 

at altitudes of 840 ft (upper intake) and 280 ft (lower intake) 

(fig. 2). Surface water captured at the upper intake traveled 

southeast in Upper Anahola Ditch and was discharged into 

Kaneha Reservoir. A wasteway was located just upstream from 

the reservoir where some of the flow diverted at the upper 

intake could be returned to Anahola Stream, about 5.4 mi 

downstream of the upper intake, by way of tributary Kaupaku 

Stream. The lower intake, located about 3.6 mi downstream of 

the upper intake, diverted Anahola streamflow into the Lower 

Anahola Ditch, which transported the diverted water to the 

Upper and Lower Anahola Reservoirs (fig. 2). All of the flow 

in Goldfish Stream discharged into Kaneha Reservoir. With 

a maximum capacity of 116 Mgal (Souza and others, 1996), 

Kaneha Reservoir was a collection point for the majority of 

the surface water diverted by the Makee diversion system. 

Kaneha Ditch transported the diverted water from the reservoir 

to several smaller reservoirs along the ditch and ultimately to 

the sugarcane fields.

The USGS operated six ditch-flow gaging stations in 

the Upper and Lower Anahola Ditches for parts of the period 

1909–2002 (fig. 2). Three stations measured flows within 

the Upper Anahola Ditch: station 16086000 was located 

upstream of the wasteway, station 16087000 was located in 

the wasteway about 300 ft downstream of the wasteway gates, 

and station 16088000 was located at the point of discharge 

into Kaneha Reservoir. During the period 1916–21, records 

at station 16086000 showed that an average daily flow of 

4.9 Mgal/d was diverted into the Upper Anahola Ditch 

before some of the diverted flow was returned to Anahola 

Stream through the wasteway. When station 16086000 was 

discontinued, the combined discharges measured at stations 

Description of the Study Area 7
16087000 and 16088000 represented the total amount of 

surface water diverted at the Upper Anahola Ditch intake, 

assuming minimal surface-water losses in the wasteway 

upstream from station 16087000 and in the ditch between the 

wasteway and station 16088000. During the period 1936–85, 

the average daily flow at the two stations combined was about 

5.4 Mgal/d, and an average daily flow of 2.7 Mgal/d was 

discharged into Kaneha Reservoir.

The three gaging stations in the Lower Anahola 

Ditch include station 16090000 about a quarter of a mile 

downstream from the lower intake, station 16091000 near the 

end of the ditch, and station 16092000 upstream of Upper 

Anahola Reservoir. Records at station 16090000 showed 

that an average daily flow of 5.9 Mgal/d was diverted into 

Lower Anahola Ditch between 1909 and 1914. During the 

period 1937–82, an average daily flow of 1.9 Mgal/d was 

recorded at station 16091000. The difference in average daily 

flows at stations 16090000 and 16091000 may be attributed 

to differences in the periods of record and operation and 

condition of the ditch. Fragmentary record was collected at 

station 16092000 when it was in operation during 1909–11.

Biological Setting

Isolation of the Hawaiian Islands resulted in the evolution of 

a unique community of native stream fauna that utilize a variety 

of macro- and microhabitats within stream ecosystems. Recent 

human activities have resulted in the introduction of a number of 

nonnative species into Hawaiÿi, and these nonnative species may 

compete with native species for available resources, or they may 

prey on the native species directly. Different natural and humaninfluenced conditions affect the ability of the amphidromous 

native stream fauna to recruit, colonize, and flourish in a stream. 

The amphidromous life history of native species requires stream 

connectivity to the ocean to enable recruitment. Any condition that 

impedes connectivity can affect the distribution and abundance of 

amphidromous fauna.

Reconnaissance-level biological surveys of Anahola 

Stream were conducted as part of this study to document the 

distribution of native and nonnative aquatic stream fauna. 

Six stream reaches along Anahola Stream were surveyed during 

August 8–12 and September 19–23, 2011 (table 1, fig.4). The 

study reaches were selected to represent a variety of habitats 

available along Anahola Stream, and the reach lengths were 

determined by time limitations imposed by the difficulty of 

accessing and traversing the survey sites. In general, the stream 

water was consistently mildly turbid with a yellowish-orange 

hue, even during dry-weather conditions. Thick mats of algal 

growth were present on the rocky substrates in all habitats 

except those with the fastest flowing water such as cascades. 

The stream bed in most pools was covered by a layer of 

leaf litter and other organic debris. Rainfall just prior to the 

September 19–23, 2011, surveys made Anahola Stream very 

turbid on the 19th and 20th, limiting the ability to observe the 

instream fauna in the six surveyed stream reaches.

As part of the biological surveys, the presence or absence 

and the distribution of aquatic species were determined using 

snorkel surveys at the six selected reaches on Anahola Stream. 

During the surveys a snorkeler entered the stream below the 

downstream end of the reach and slowly moved upstream, 

photographing and identifying the observed fish, snail, and 

crustacean species. For some of the native fish species, when 

possible, the size-class, age (adult or juvenile), and sex were 

determined. Locations of the observations were recorded 

with a Global Positioning System (GPS) unit. The snorkel 

surveys were supplemented by the occasional use of a seine 

net and hook and line sampling. The presence of some benthic 

macroinvertebrates was determined by overturning and 

inspecting rocks while snorkeling. Adult native damselflies, 

pinao ÿula, of the endemic genus Megalagrion were also 

photographed and identified. Identifications were determined 

Table 1. Locations and lengths of stream reaches where biological surveys were conducted by the U.S. Geological 

Survey in Anahola Stream, August 8–12 and September 19–23, 2011, Kauaÿi, Hawaiÿi.

Study reach 

identifier

Study reach description 

(Anahola Stream)

Length,

in miles

Upstream point Downstream point

Altitudeb,

in feet Latitudec Longitudec Altitudeb

,

in feet Latitudec Longitudec

Upper 1 Upstream of upper intake 0.55 1,020 22°08'26.5" 159°23'31.2" 830 22°08'37.7" 159°23'14.0"

Upper 2 1.5 miles downstream of 

upper intake

0.16 540 22°08'44.7" 159°22'25.9" 510 22°08'46.4" 159°22'19.6"

Middle 1 Near Keaÿoÿopu Stream 0.63 430 22°08'44.2" 159°21'53.7" 340 22°08'59.6" 159°21'36.9"

Middle 2a Near lower intake 0.58 310 22°08'58.1" 159°21'15.8" 260 22°08'55.9" 159°20'50.9"

Lower 1 Upstream of Kaÿalula 

Stream

1.11 180 22°08'32.0" 159°20'07.3" 80 22°08'14.8" 159°19'15.6"

Lower 2 Upstream of estuary 0.22 10 22°08'25.9" 159°18'59.2" 10 22°08'29.6" 159°18'49.8"

a

 Middle 1 study reach includes a 200-foot reach within tributary Keaÿoÿopu Stream immediately upstream of its confluence with Anahola Stream.

b

 Altitude values interpolated from USGS 1:24,000-scale digital hypsography data.

c

 Latitude and longitude coordinates in North American Datum of 1983.

8 Availability and Distribution of Low Flow in Anahola Stream, Kauaÿi, Hawaiÿi
using “Hawaiian Damselflies: a Field Identification Guide” by 

Polhemus and Asquith (1996). Identifications were verified by 

Dr. Dan A. Polhemus, Coastal Conservation Program Manager 

at the Pacific Islands Fish and Wildlife Office, U.S. Fish and 

Wildlife Service. Additional observations of aquatic biota 

were made during the biological surveys at various locations 

along Anahola Stream to provide supplemental information on 

the distribution of the aquatic fauna. All captured fauna were 

released unharmed back into the environment from which 

they were collected. Results of the August and September 

2011 biological surveys are described in the following text, 

summarized in table 2, and illustrated in figures 4 and 5.

Native Species

Eleven native species were observed in the selected 

reaches of Anahola Stream during the biological surveys 

(fig.4; table 2). The endemic Sandwich Island sleeper, Eleotris 

sandwicensis (ÿoÿopu ÿakupa), was commonly observed 

lying in wait amid rocky crevices and leaf litter in pools 

throughout the Lower 2 study reach, and a single ÿoÿopu 

ÿakupa was observed in the Lower 1 study reach at an altitude 

of about 140 ft. Adults and juveniles, males and females of 

the Pacific river goby, Awaous guamensis (ÿoÿopu näkea), 

were numerous within pools, runs, and riffles within each of 

the six study reaches along Anahola Stream. The endemic 

Stimpsonÿs goby, Sicyopterus stimpsoni (ÿoÿopu nöpili) 

were not observed within the Lower 2 study reach and were 

infrequently observed within the Upper 1 study reach up to 

an altitude of about 1,000 ft. However, adult and juvenile, 

male and female ÿoÿopu nöpili were commonly observed in 

riffles and cascades within the other study reaches. Adults 

and juveniles of the endemic teardrop goby, Stenogobius 

hawaiiensis (ÿoÿopu naniha) were observed in pools and runs 

within the Lower 2 study reach and were not observed in any 

of the other study reaches. Schools of the Hawaiian flagtail, 

Kuhlia xenura (äholehole), were commonly observed in pools 

within the Lower 2 study reach. Smaller schools of äholehole 

were also commonly observed in pools throughout the Lower 

1 study reach and individuals were occasionally observed in 

pools within the downstream segment of the Middle 2 study 

reach up to an altitude of about 270 ft. Schools of the striped 

mullet, Mugil cephalus (ÿamaÿama), were commonly observed 

in pools throughout the Lower 2 study reach but were not 

observed in any of the other study reaches. 

Adult and juvenile mountain shrimp, Atyoida bisulcata

(ÿöpae kalaÿole), were only observed within the Upper 1 study 

reach and were common in riffles, runs, and pools above an 

altitude of about 910 ft. A single ÿöpae kalaÿole recruit about 

0.75 inch long was observed within the Middle 2 study reach, 

captured from a cascade using a seine net. The endemic 

river prawn, Macrobrachium grandimanus (ÿöpae ÿoehaÿa) 

was observed in pools within the Lower 2 study reach, and a 

single ÿöpae ÿoehaÿa was observed within the Lower 1 study 

reach near an altitude of 140 ft. The endemic damselflies, 

Megalagrion oresitrophum (Slender Kauaÿi damselfly) and 

Megalagrion vagabundum (Scarlet Kauaÿi damselfly) were 

commonly observed only within the Upper 1 study reach. 

Adult males and females of both species were observed 

flying about the streambank vegetation and basking atop 

exposed boulders, and were occasionally observed mating. 

An unidentified Megalagrion individual was briefly observed 

within the riparian vegetation along the Upper 2 study reach.

Four of the commonly observed native stream species, 

Neritina granosa (hïhïwai), Neritina vespertinus (hapawai), 

Lentipes concolor (ÿoÿopu ‘alamo‘o), and the native 

chironomid Telmatogeton, were conspicuously not observed 

during the biological surveys in the six study reaches along 

Anahola Stream. The hïhïwai and hapawai require clean 

substrate on which to attach (Ford, 1979). The rocky substrate 

of Anahola Stream tended to be covered by thick algal mats 

or sediment that may impede the recruitment of these species. 

The ÿoÿopu ‘alamo‘o also has specific habitat requirements—

including clean substrate, high water velocity, and low 

turbidity that may not have been sufficiently present to allow 

for substantial recruitment in Anahola Stream (Timbol and 

others, 1980). Furthermore, they found that streams with the 

native ÿoÿopu akupa, a top predator in the estuary and lower 

stream reaches, had few, if any, ÿoÿopu ‘alamo‘o. The ÿoÿopu 

ÿakupa was observed to be very abundant in the Lower 2 study 

reach in Anahola Stream during the 2011 biological surveys. 

The presence of the native aquatic insect Telmatogeton was 

recorded in 1965 (Parham and others, 2008) within the Upper 

1 study reach but was not observed during the 2011 biological 

surveys of the same area.

Nonnative Species

Eleven nonnative species and one cryptogenic 

(undetermined origin) species were observed in Anahola 

Stream (fig. 5; table 2). Schools of short-finned mollies, 

Poecilia sphenops, were commonly observed in pools within 

the Lower 2 study reach but were not observed within any 

of the other study reaches. The most commonly observed 

nonnative fish were green swordtails, Xiphophorus helleri, 

which were very abundant in pools and runs throughout the 

study reaches, except for the Upper 1 study reach where they 

were only observed up to a cascade or small waterfall near 

an altitude of 870 ft. These schools consisted of males and 

females, adults and juveniles, and both green and orange color 

patterns. Unconfirmed observations of two other nonnative 

fish species, Chinese catfish, Clarias fuscus, and Western 

mosquitofish, Gambusia affinis, were made. These fish 

were not captured or photographed, and the identifications 

were made from very brief observations. Clarias fuscus was 

previously captured and identified in Anahola Stream during 

a survey in 2001 using electrofishing techniques (Brasher 

and others, 2006), but this cryptic (concealed) fish is difficult 

to observe using snorkeling techniques. Gambusia affinis

has not been reported from Anahola Stream, and many of 

the fish of the family Poeciliidae are similar in appearance 

at different stages in their development. It is possible that 

Description of the Study Area 9
Kuhlia xenura Mugil cephalus

Atyoida bisulcata Macrobrachium grandimanus

Stenogobius hawaiiensis

Anahola

Bay

Kalalea Mountains

Namahana Mountains

Anahola

Anahola Stream

drainage basin

Goldfish Stream

drainage basin

Upper Middle Lower

159°24' 159°21'

22°9'

22°8'

EXPLANATION

Base modified from U.S. Geological Survey digital data. Universal Transverse 

Mercator projection, zone 4, North American Datum 1983.

0 1 2 MILES

0 1 2 KILOMETERS

PACIFIC

OCEAN

Island of Kauaÿi

Map

area

1 2 1 2 1 2

Stream reaches surveyed during the 2011 

biological surveys –Color bar shows the 

presence or absence of native aquatic species

(shown in photo) in the similarly colored surveyed 

reaches of Anahola Stream

Eleotris sandwicensis Awaous guamensis Sicyopterus stimpsoni

0.75 in.

KeaÿoÿopuStr

Anahola Stream

Kaÿalula Str

KaupakuStream

Goldfish Str

Anahola Stream

Figure 4. Map showing locations of stream reaches surveyed and the distribution of selected native aquatic species 

observed during the 2011 U.S. Geological Survey biological surveys in Anahola Stream, Kauaÿi, Hawaiÿi. (Aquatic species 

shown in the photographs without a scale bar generally range from a few inches to one foot.)

10 Availability and Distribution of Low Flow in Anahola Stream, Kauaÿi, Hawaiÿi
Table 2. Species observed during U.S. Geological Survey biological surveys of Anahola Stream, August 8–12 and 

September 19–23, 2011, Kauaÿi, Hawaiÿi.

[Cg, cryptogenic; A, nonnative; N, native; U, uncommon; P, present; C, common; *, unconfirmed observation; --, not observed during surveys]

Phylum

 Class

 Order

 Family

 Taxon

Common name Hawaiian 

name

Status

Study reach identifier

Upper Middle Lower

1 2 1 2 1 2

Chordata

 Osteichthyes

 Cyprinodontiformes

 Poeciliidae

 Gambusia affinis Western mosquitofish A -- -- -- * * --

 Poecilia sphenops Short-finned molly A -- -- -- -- -- C

 Xiphophorus helleri Green swordtail A C C C C C C

 Perciformes

 Eleotridae

 Eleotris sandwicensis Sandwich Island sleeper ÿOÿopu ÿakupa N -- -- -- -- U C

 Gobiidae

 Awaous guamensis Pacific river goby ÿOÿopu näkea N C C C C C C

 Sicyopterus stimpsoni Stimpson's goby ÿOÿopu nöpili N P C C C C --

 Stenogobius hawaiiensis Teardrop goby ÿOÿopu naniha N -- -- -- -- -- C

 Kuhliidae

 Kuhlia xenura Hawaiian flagtail Äholehole N -- -- -- P C C

 Mugilidae

 Mugil cephalus Striped mullet ÿAmaÿama N -- -- -- -- -- C

 Siluriformes

 Clariidae

 Clarias fuscus Chinese catfish A -- -- -- -- * --

 Amphibia

 Anura

 Bufonidae

 Rhinella marina (Bufo marinus) Cane toad A C C C C C C

 Ranidae

 Rana catesbeiana Bullfrog A P P -- -- P P

Arthropoda

 Crustacea

 Decapoda

 Atyidae

 Atyoida bisulcata Mountain shrimp ÿÖpae kalaÿole N C -- -- U -- --

 Cambaridae

 Procambarus clarkii Red swamp crayfish A -- -- -- U -- --

 Palaemonidae

 Macrobrachium grandimanus Hawaiian river prawn ÿÖpae ÿoehaÿa N -- -- -- -- P P

 Macrobrachium lar Tahitian prawn A -- C C C C C

 Insecta

 Odonata

 Coenagrionidae

 Megalagrion sp. Native Hawaiian damselfly Pinao ÿula N -- P -- -- -- --

 Megalagrion oresitrophum Slender Kauai damselfly Pinao ÿula N C -- -- -- -- --

 Megalagrion vagabundum Scarlet Kauai damselfly Pinao ÿula N C -- -- -- -- --

 Ischnura posita Fragile forktail A -- P -- P P --

 Libellulidae

 Crocothemis servilia Scarlet skimmer A -- P -- -- -- --

 Trichoptera

 Hydropsychidae

 Cheumatopsyche analis Little sister sedges A C C C C C C

Mollusca

 Gastropoda

 Basommatophora

 Thiaridae

 Melanoides tuberculata Red–rimmed melania Cg -- -- -- C C --

 Pelecypoda

 Venerioda

 Corbiculidae

 Corbicula fluminea Asian clam A -- -- -- -- C P

Platyhelminthes

 Turbellaria

 Tricladida

 Planariidae Flatworm A C C C C C C

Description of the Study Area 11
these observations were of juvenile green swordtails or shortfin 

mollies. Tadpoles of the Bullfrog, Rana catesbeiana, were 

observed in pools within the upper and lower study reaches. 

Adult Rana catesbeiana were not as common as the tadpoles, 

but they were observed in some pools—and sounds thought 

to be adult bullfrogs leaping into the stream were often heard. 

Tadpoles, toadlets (young toads), and adult cane toads, Rhinella 

marina (Bufo marinus), were much more abundant than the 

bullfrogs. Large numbers of Rhinella marina tadpoles were 

commonly observed in pools and habitats with slow flowing 

water, whereas the toadlets were commonly observed along 

the streambanks and were very abundant within some study 

reaches. Adult cane toads were less abundant than the tadpoles 

and toadlets as they instinctively move away from the stream as 

adults. They were often observed within all the study reaches 

and along many of the hiking trails.

A single specimen of the red swamp crayfish, 

Procambarus clarkii, was briefly observed among the cobbles 

and boulders along the streambank within the Middle 2 

study reach. This observation appears to be the first record 

of this potentially harmful species in Anahola Stream and 

indicates that it is not yet established at this time (Yamamoto 

and Tagawa, 2000). Adults and juveniles of the Tahitian 

prawn, Macrobrachium lar, were also very abundant in pools 

and habitats with slow flowing water throughout the study 

reaches except for the Upper 1 study reach. The nonnative 

damselfly known as the fragile forktail, Ischnura posita, 

was observed in the riparian vegetation within the Lower 1, 

Middle 2, and Upper 2 study reaches. A nonnative dragonfly 

known as the Scarlet skimmer, Crocothemis servilia, 

was observed within the Upper 2 study reach. Two small 

benthic macroinvertebrates were observed on the undersides 

of cobbles within every study reach. These nonnative 

invertebrates were insect larvae of the caddisfly known as 

little sister sedges, Cheumatopsyche analis, and a flatworm of 

the family Planariidae that is probably of the genus Dugesia. 

Cheumatopsyche analis larvae were more commonly 

observed on the undersides of cobbles from riffles and runs 

with fast flowing water, whereas the flatworms were more 

commonly observed in pools and on the undersides of cobbles 

from runs with slow flowing water.

The Asian clam, Corbicula fluminea, was observed 

in pockets of sand within the Lower 1 and 2 study reaches, 

downstream of the confluence with Kaupaku Stream, and was not 

observed upstream of the confluence. It is likely this species was 

introduced sometime in the past into a taro loÿi (irrigated terrace), 

located near the confluence, as a food resource and it has dispersed 

into Anahola Stream by way of Kaupaku Stream and has become 

established downstream of the confluence. However, it is incapable 

of migrating upstream of the confluence on its own. Conversely, 

the cryptogenic red-rimmed melania, Melanoides tuberculata, 

were only observed upstream of the confluence attached to cobbles 

and boulders in pools and habitats with slow flowing water within 

the Lower 1 and downstream of the Middle 2 study reaches up to 

an altitude of about 400 ft.

Streamflow Characteristics

Streamflow characteristics at a gaging station are 

commonly described using a flow-duration curve. A flowduration curve is a cumulative-frequency distribution 

that shows the percentage of time that specific discharges 

(commonly daily mean values) at the gaged site are 

equaled or exceeded over a specified period of time. The 

period of time is typically expressed in water years. A 

water year is a 12-month period that extends from October 

1 to September 30 of the following year and is named 

according to the year during which the period ends. For 

example, the “2012 water year” is the period October 

1, 2011, to September 30, 2012. The most frequently 

computed flow-duration statistic is the 50th percentile 

discharge, commonly referred to as median discharge or 

the Q50 flow-duration statistic. The median discharge is 

the flow that has been equaled or exceeded 50 percent 

of the time during the specified time period. Low-flow 

duration discharges are generally considered to be those 

equal to or less than the Q50 flow-duration statistic, and 

they are represented by the lower end of the flow-duration 

curve. The slope of the flow-duration curve is affected by 

hydrologic and geologic characteristics of the drainage 

basin. A steep slope suggests variable flow conditions 

in the stream as a result of direct runoff. A flat slope, 

especially at the low-flow end of the flow-duration curve, 

suggests perennial-flow conditions in which streamflow is 

sustained by groundwater discharge.

Base flow is part of the total streamflow that is 

supported by the discharge of groundwater, which occurs 

where the stream intersects the water table (Oki, 2003). 

The base flow of Anahola Stream at the discontinued 

streamflow-gaging stations was estimated using the 

automated hydrograph-separation method developed 

by Wahl and Wahl (1995). The hydrograph-separation 

method requires two input parameters, N (number of 

days) and f (turning point factor), defined by the user. 

The hydrograph-separation method involves dividing 

the specified time period with daily discharge record (in 

complete water years) into nonoverlapping increments 

of N days. The minimum flows within each of the N-day 

increments (central minimum) are identified. The central 

minimum is designated as a turning point on the base-flow 

hydrograph if f times the central minimum is less than the 

minimum flows in the adjacent increments. The base-flow 

hydrograph is plotted by drawing straight lines between 

turning points on semilogarithmic paper. The area beneath 

the base-flow hydrograph is the volume of base flow 

for the specified time period. For discontinued Anahola 

Stream gaging stations, N was determined to be 4 days 

and f, as recommended by Wahl and Wahl (1995), was 

0.9. These input parameters were used in the automated 

hydrograph-separation method to estimate base flow at the 

discontinued Anahola Stream gaging stations.

12 Availability and Distribution of Low Flow in Anahola Stream, Kauaÿi, Hawaiÿi
Macrobrachium lar

Upper Middle Lower

EXPLANATION

1 2 1 2 1 2

Stream reaches surveyed during the 2011 

biological surveys –Color bar shows the 

presence or absence of nonnative aquatic 

species (shown in photo) in the similarly colored 

surveyed reaches of Anahola Stream.

Poecilia sphenops Xiphophorus helleri Melanoides tuberculata

Rhinella marina Corbicula fluminea Planariidae

0.5 in.

1 in.

0.0625 in.

Anahola

Bay

Kalalea Mountains

Namahana Mountains

Anahola

Anahola Stream

drainage basin

Goldfish Stream

drainage basin

159°24' 159°21'

22°9'

22°8'

Base modified from U.S. Geological Survey digital data. Universal Transverse 

Mercator projection, zone 4, North American Datum 1983.

0 1 2 MILES

0 1 2 KILOMETERS

PACIFIC

OCEAN

Island of Kauaÿi

Map

area

KeaÿoÿopuStr

Anahola Stream

Kaÿalula Str

KaupakuStream

Goldfish Str

Anahola Stream

Figure 5. Map showing locations 

of stream reaches surveyed and the 

distribution of selected nonnative 

aquatic species observed during 

the 2011 U.S. Geological Survey 

biological surveys in Anahola 

Stream, Kauaÿi, Hawaiÿi.

Streamflow Characteristics 13
Anahola Stream Under 

Regulated Flow Conditions

Historically, the USGS operated two 

continuous-record streamflow-gaging stations 

on Anahola Stream, and both were located 

downstream from locations where the Makee 

diversion system was actively diverting surface 

water for sugarcane cultivation (fig.2). Because 

the Makee diversion system in the Anahola 

Stream drainage basin has been abandoned, 

historical streamflow records at these stations 

are not representative of present-day conditions 

in the valley. Nevertheless, streamflow 

characteristics at the stations are summarized 

to provide insight on the regulated conditions 

of the stream, which may be helpful if parts 

of the Makee diversion system in the study 

area are restored in the future. Streamflow 

statistics provided for Anahola Stream under 

regulated flow conditions are applicable to the 

period of record from which the statistics were 

computed.

One of the continuous-record stations 

on Anahola Stream (station 16089000) was 

located at an altitude of 295 ft; this site was 

downstream from the Upper Anahola Ditch 

diversion intake and immediately upstream 

from the Lower Anahola Ditch diversion intake 

(fig. 2). During the period 1910 and 1913–85 

when the station was in operation, 70 complete 

water years (1914–17 and 1920–85) of 

streamflow data were collected. During those 

water years, annual mean discharges ranged 

from 5.6 Mgal/d in 1984 to 36 Mgal/d in 1969 

(fig. 6). Mean monthly discharges show a 

seasonal pattern in which June to October had 

the lower flows and November to May had 

the higher flows (fig. 7). The maximum daily 

discharge was 1,130 Mgal/d and the minimum 

daily discharge was 1.0 Mgal/d. The low-flow 

duration discharges ranged from 1.7 Mgal/d 

(Q99 discharge) to 6.3 Mgal/d (Q50 discharge) 

(table 3, fig. 8).

The other continuous-record station 

on Anahola Stream (station 16093200) was 

located about 590 ft upstream from the estuary; 

streamflow at this location reflected diversion 

at both the Upper and Lower Anahola Ditches 

and return flow from the Upper Anahola Ditch 

wasteway (fig. 2). The station was in operation 

between 1964 and 1982, during which 17 

complete water years (1966–82) of streamflow 

data were collected. During those water 

years, annual mean discharges ranged from 

12 Mgal/d in 1973 to 50 Mgal/d in 1969 and 

0

5

10

15

20

25

30

35

40

1920 1930 1940 1950 1960 1970 1980

Annual mean discharge, in million gallons per day

Water year

Mean discharge

No data

0

5

10

15

20

25

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

Mean monthly discharge, in million gallons per day

Month

Figure 6. Plot showing annual mean discharges at streamflowgaging station 16089000 on Anahola Stream, Kauaÿi, Hawaiÿi, for 

water years with complete record during 1913–1985.

Figure 7. Plot showing mean monthly discharges at streamflowgaging station 16089000 on Anahola Stream, Kauaÿi, Hawaiÿi, for 

water years with complete record during 1913–1985.

14 Availability and Distribution of Low Flow in Anahola Stream, Kauaÿi, Hawaiÿi
1982 (fig. 9). Mean monthly discharges show 

a seasonal pattern in which June to October 

had the lower flows and November to May had 

the higher flows (fig. 10). The maximum daily 

discharge was 1,080 Mgal/d and the minimum 

daily discharge was 1.6 Mgal/d. The low-flow 

duration discharges ranged from 2.4 Mgal/d 

(Q99 discharge) to 10 Mgal/d (Q50 discharge) 

(table 3, fig. 11).

Study-Area Streams Under 

Natural Flow Conditions

The primary focus of this study is to 

characterize the availability and distribution 

of streamflow in Anahola Stream under 

natural (undiverted), low-flow conditions. 

Low-flow availability is determined typically 

by computing low-flow duration discharges 

at the sites of interest. Ideally, flow-duration 

discharges should be computed from 

streamflow data at a long-term continuousrecord station established upstream from 

points of diversion to accurately describe the 

availability of natural low flows. Similarly, 

the distribution of low flows along a stream, 

1

10

100

1,000

1 5 10 30 50 70 90 95 99

Daily mean discharge, in million gallons per day

Percentage of time indicated discharge was equaled or exceeded

Total flow

Base flow

Table 3. Selected flow-duration discharges 

for total streamflow at streamflow-gaging 

stations 16089000 and 16093200 on 

Anahola Stream, Kauaÿi, Hawaiÿi, during 

indicated period of record with complete 

water years.

[Mgal/d, million gallons per day; POR, period of record]

Percentage

of time 

indicated flow 

equaled or 

exceeded

Discharge (Mgal/d)

16089000

POR:

1914–17, 

1920–85

16093200

POR:

1966–82

99 1.7 2.4

95 2.3 3.2

90 2.4 3.9

85 3.3 4.5

80 3.7 5.3

75 4.1 5.9

70 4.5 6.5

65 4.8 7.1

60 5.3 7.8

55 5.8 9.0

50 6.3 10

Figure 8. Plot showing flow-duration curves for total flow and 

base flow at streamflow-gaging station 16089000 on Anahola 

Stream, Kauaÿi, Hawaiÿi, for water years with complete record 

during 1913–1985.

Figure 9. Plot showing annual mean discharges at streamflowgaging station 16093200 on Anahola Stream, Kauaÿi, Hawaiÿi, for 

water years with complete record during 1966–1982.

0

10

20

30

40

50

60

1966 1968 1970 1972 1974 1976 1978 1980 1982

Annual mean discharge, in million gallons per day

Water year

Mean discharge of 24 million gallons per day

Streamflow Characteristics 15
which may vary in both time and location 

due to interactions between surface water 

and groundwater, can be determined 

from long-term streamflow data from 

continuous-record stations established at 

multiple locations along a stream. However, 

long-term continuous-record stations are 

rarely available at all locations where data 

are desired. Alternatively, the availability 

and distribution of low flow in a stream 

can be determined using a combination of 

discharge measurements made at LFPR and 

seepage-run stations established at the sites 

of interest where data are collected over a 

shorter period of time. The following section 

of the report includes discussion on using 

discharge measurements at LFPR stations to 

determine low-flow availability in Anahola 

and Goldfish Streams. The method of using 

discharge measurements at seepage-run 

stations to describe the distribution of natural 

low flow in Anahola Stream is discussed in 

the subsequent section “Natural Low-Flow 

Distribution.”

Natural Low-Flow Availability

Record-augmentation techniques 

are commonly used to determine flowduration discharges at sites with either 

short-term record or partial-record 

streamflow data. The process of record 

augmentation involves correlating discharge 

measurements at the site of interest with 

the concurrent daily mean discharges at a 

nearby long-term continuous-record station 

(index station) to develop a statistical 

relation. Subsequently, the statistical 

relation is used to compute flow-duration 

discharges at the site of interest from 

corresponding flow-duration discharges at 

the index station for the base period. The 

base period is a common period during 

which all index stations used in the analysis 

are in operation with complete water years 

of streamflow data for computing various 

flow-duration discharges. In Hawaiÿi, 

record augmentation has been used by: 

Fontaine and others (1992) to estimate 

median streamflows for perennial streams 

in the State of Hawaiÿi; Fontaine (2003) 

to quantify base-flow availability in 

Honoköhau Stream, Island of Maui; Oki 

and others (2006) to characterize low-flow 

availability in Punaluÿu Stream, Island 

of Oÿahu; Yeung and Fontaine (2007) to 

0

5

10

15

20

25

30

35

40

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

Mean monthly discharge, in million gallons per day

Month

Figure 11. Plot showing flow-duration curves for total flow and 

base flow at streamflow-gaging station 16093200 on Anahola 

Stream, Kauaÿi, Hawaiÿi, for water years with complete record 

during 1966–1982.

Figure 10. Plot showing mean monthly discharges at streamflowgaging station 16093200 on Anahola Stream, Kauaÿi, Hawaiÿi, for 

water years with complete record during 1966–1982.

1

10

100

1,000

1 5 10 30 50 70 90 95 99

Daily mean discharge, in million gallons per day

Percentage of time indicated discharge was equaled or exceeded

Total flow

Base flow

16 Availability and Distribution of Low Flow in Anahola Stream, Kauaÿi, Hawaiÿi
describe natural and regulated low flows for streams in the 

windward side of the Island of Oÿahu; and Oki and others 

(2010) to characterize natural low flows for streams in the Nä 

Wai ÿEhä area, Island of Maui. For this study, LFPR stations 

were established at sites of interest along study-area streams 

where discharge measurements were made for use in record 

augmentation. The following sections discuss the selection 

of and data collection at the LFPR stations, the selection of 

index stations, and the implementation of record-augmentation 

techniques to determine low-flow availability in the study-area 

streams.

Low-Flow Partial-Record Stations

No continuous-record stations that measured discharges 

under natural-flow conditions have been operated in the studyarea streams. Available data from the two discontinued stations 

on Anahola Stream (stations 16089000 and 16093200) reflect 

A B

C D

Figure 12. Photographs of low-flow partial-record stations in Anahola and Goldfish Streams, Kauaÿi, Hawaiÿi. 

A. Anahola Stream immediately upstream of station 16085500. B. Anahola Stream immediately downstream 

of station 16088300. C. Discharge-measurement cross section of station 16088500 on Keaÿoÿopu Stream. D. 

Discharge-measurement cross section of station 16081500 on Goldfish Stream.

regulated-flow conditions, which are not applicable to presentday conditions in the streams. To characterize natural low-flow 

availability in the study-area streams, LFPR stations were 

established upstream from points of diversion. The locations 

of the LFPR stations were selected based on the assumption 

that one or both of the diversion intakes (upper and lower 

intakes) on Anahola Stream would likely be restored in the 

future to provide for surface-water use. Three LFPR stations 

were established on Anahola Stream: station 16085500 

about 450 ft upstream from the Upper Anahola Ditch intake 

(fig. 12A), station 16088300 about 50 ft upstream from the 

confluence with tributary Keaÿoÿopu Stream (fig. 12B), and 

station 16088500 on tributary Keaÿoÿopu Stream about 80 ft 

upstream from the confluence with Anahola Stream (fig. 12C). 

By establishing two LFPR stations near the confluence of 

Anahola and Keaÿoÿopu Streams instead of one LFPR station 

upstream from the Lower Anahola Ditch intake, low-flow 

availability could be characterized at the main channel and the 

Streamflow Characteristics 17
tributary independently. The combined concurrent discharges 

measured at these two LFPR stations represent the estimated 

discharge on Anahola Stream immediately downstream from 

its confluence with Keaÿoÿopu Stream. In Goldfish Stream, 

LFPR station 16081500 (fig. 12D) was established about 

0.4 mi upstream from the point of discharge into Kaneha 

Reservoir (table 4, fig. 13).

For record augmentation, a minimum of about 10 

discharge measurements are generally made at LFPR stations 

during periods of low flow (Rantz and others, 1982). The 

discharge measurements should be made under a variety of 

low-flow conditions and during independent recessions. A 

recession is the period when streamflows return to low-flow 

conditions following a period of direct runoff. Hydrographs 

from nearby, currently active, continuous-record streamflowgaging stations were checked to determine when recessions 

were in place in the Anahola and Goldfish Streams study 

area. The optimal period to make a discharge measurement 

at the LFPR station is depicted in a streamflow hydrograph 

as the later phases in the recession limb when the curve 

Table 4. Altitude and latitude and longitude coordinates of low-flow partial-record and seepage-run dischargemeasurement stations in the Anahola and Goldfish Streams study area, Kauaÿi, Hawaiÿi.

[ID, identifier; USGS, U.S. Geological Survey; DS, downstream; alt, altitude]

Station ID USGS station 

number

USGS station name,

in Kauai, HI

Altitudea,

in feet Latitudeb Longitudeb

Low-flow partial-record stations

16081500 16081500 Unnamed Tributary above Kaneha Reservoir 880 22°08'05" 159°22'45"

16085500 16085500 Anahola Stream above upper ditch intake 860 22°08'38" 159°23'18"

16088300 16088300 Anahola Stream near Keaoopu Tributary confluence 350 22°09'00" 159°21'38"

16088500 16088500 Keaoopu Tributary near Anahola Str confluence 350 22°09'02" 159°21'38"

Seepage-run discharge-measurement stations

1c 16085500 Anahola Stream above upper ditch intake 860 22°08'38" 159°23'18"

2 220843159225901 Anahola Stream below upper ditch intake 740 22°08'42.5" 159°22'59.3"

3 220848159224501 Upper Tributary of Anahola Stream 630 22°08'48.0" 159°22'45.4"

4c 16088300 Anahola Stream near Keaoopu Trib confluence 350 22°09'00" 159°21'38"

5c 16088500 Keaoopu Tributary near Anahola Str confluence 350 22°09'02" 159°21'38"

6 220857159213401 Tributary of Anahola Steam below confluence 340 22°08'56.6" 159°21'33.8"

7 220855159212601 Anahola Stream below confluence at alt 300 ft 330 22°08'55.2" 159°21'25.8"

8 220856159211201 Tributary of Anahola Stream above lower intake 300 22°08'56.0" 159°21'12.0"

9 220854159210601 Anahola Stream below lower ditch intake 280 22°08'54.0" 159°21'05.6"

9a 220854159210501 Lower Anahola Ditch DS of tunnel 280 22°08'53.8" 159°21'04.6"

10 220832159200601 Lower Anahola Stream at alt 200 ft 170 22°08'32.4" 159°20'05.7"

11 220821159194501 Kaupaku Stream near Anahola 140 22°08'21.2" 159°19'45.3"

12 220815159191601 Anahola Stream upstream Kaalula Tributary 70 22°08'15.2" 159°19'15.8"

a

 Altitude values interpolated from USGS 1:24,000-scale digital hypsography data.

b

 Latitude and longitude coordinates in North American Datum of 1983.

c

 Seepage-run stations that were low-flow partial-record stations during the study period of February 2011 to May 2012.

begins to level out, eventually reaching base flow. For this 

study, 10 to 12 discharge measurements were made at each 

of the LFPR stations between February 2011 and May 2012. 

Discharge measurements were made with acoustic Doppler 

velocimeters (ADV) and Price pygmy vertical-axis current 

meters. Since the LFPR stations were difficult to access, 

discharge measurements at the stations could not all be made 

on the same day. A majority of the measurements were made 

when flows were generally stable. Stable flow conditions 

were documented by recording the height of water surface, 

commonly referred to as gage height or stage, during the 

time when discharge measurements were being made. A few 

of the measurements were made when gage heights were 

variable and direct runoff may have been occurring and those 

measurements were not used to estimate low-flow duration 

discharges. All of the discharge measurements made at the 

LFPR stations for this study are presented in tables 5 to 9 

and they are stored in the USGS National Water Information 

System (NWIS) database.

18 Availability and Distribution of Low Flow in Anahola Stream, Kauaÿi, Hawaiÿi
Anahola Stream drainage basin

Goldfish Stream

drainage basin

Anahola

Bay

Kalalea Mountain s Namahana Mountains

Anahola

Kühiö Highway

Lower Anahola Ditch

Upper Anahola Reservoir

Lower Anahola Reservoir

Kaneha Reservoir

Field 1 Kealia Reservoir

Field 2 Kealia Reservoir

Unnamed Reservoir

Anahola Str

Keälia Ditch

Kapaÿa

Keälia

Keaÿoÿopu Str

Anahola Str

Ka

ÿalula Str

Kaupaku Str

Goldfish Str

Upper Anahola

D

i

tch

Kaneha Ditch

1

16085500

16081500

516088500

4

16088300

2

3 6 7 8

9

9a

10

11 12

0

500

10001500200025003000

0 2 4 6 8 10 12

, in feetnoitavelE

Distance from headwaters, in miles

Elevation profile of Anahola Stream

16085500

2 3

6

7

8

9

10

11 12 16088300

16088500

159°18' 159°21' 159°24'

22°9'22°7'

PACIFIC

OCEAN

Island of Kauaÿi

Map

area

Study-area drainage basinsMakee diversion system near study areaLow-flow partial-record station and number – For stations with two numbers, the upper number is the seepage-run station number and the lower number is the low-flow partial-record station number.

Seepage-run measurement station and identifier

Main channel Tributary or ditch

EXPLANATION

2

16088500

11

0 2 1 MILES0 2 1 KILOMETERS

Base modified from U.S. Geological Survey digitaldata. Universal Transverse Mercator projection,zone 4, North American Datum 1983.

Figure 13. Map showing discharge-measurement stations in the Anahola and Goldfish Streams study area, Kauaÿi, Hawaiÿi. (Reservoir names from State of Hawaiÿi, 2012.)

Streamflow Characteristics 19
Table 5. Measured discharges at low-flow partial-record 

station 16085500 on Anahola Stream upstream of upper 

ditch intake and concurrent daily mean discharges at 

streamflow-gaging station 16097500 on Halaulani Stream, 

Kauaÿi, Hawaiÿi.

[Mgal/d, million gallons per day; discharges not used in record augmentation 

are underlined]

Date

Daily mean discharge

in Mgal/d

Station 16097500 Station 16085500

02/23/11 3.9 2.50

03/01/11 3.4 1.51

03/21/11 3.7 2.01

04/13/11 3.4 1.64

04/15/11 3.3 1.50

07/05/11 4.3 2.86

07/28/11 5.7 2.92

08/08/11 4.1 1.66

09/02/11 3.1 1.36

09/26/11 2.6 0.80

05/22/12 3.1 0.72

Table 6. Measured discharges at low-flow partial-record 

station 16088300 on Anahola Stream near Keaÿoÿopu 

tributary confluence and concurrent daily mean discharges 

at streamflow-gaging station 16097500 on Halaulani 

Stream, Kauaÿi, Hawaiÿi.

[Mgal/d, million gallons per day; discharges not used in record augmentation 

are underlined]

Date

Daily mean discharge

in Mgal/d

Station 16097500 Station 16088300

02/24/11 7.8 6.85

03/02/11 3.4 2.86

03/22/11 3.9 5.46

04/15/11 3.3 2.66

06/02/11 4.8 4.64

07/05/11 4.3 4.42

07/28/11 5.7 4.69

09/02/11 3.1 2.73

09/26/11 2.6 1.56

04/04/12 4.0 2.81

05/22/12 3.1 1.80

Table 7. Measured discharges at low-flow partial-record 

station 16088500 on Keaÿoÿopu tributary near Anahola 

Stream confluence and concurrent daily mean discharges at 

streamflow-gaging station 16071500 on left branch ÿÖpaekaÿa 

Stream, Kauaÿi, Hawaiÿi.

[Mgal/d, million gallons per day; discharges not used in record augmentation 

are underlined]

Date

Daily mean discharge

in Mgal/d

Station

16071500

Station

16088500

02/24/11 16 3.63

03/02/11 1.9 2.26

03/22/11 2.1 3.33

04/15/11 1.2 1.77

06/02/11 1.6 2.35

07/05/11 1.2 1.52

07/28/11 0.78 1.63

09/02/11 0.46 1.07

09/26/11 0.35 0.74

04/04/12 1.7 2.15

05/22/12 0.58 1.01

Table 8. Combined discharges measured at low-flow partialrecord station 16088300 on Anahola Stream near Keaÿoÿopu 

Stream confluence and low-flow partial-record station 16088500 

on Keaÿoÿopu Stream near Anahola Stream confluence, and 

concurrent daily mean discharges at streamflow-gaging station 

16097500 on Halaulani Stream, Kauaÿi, Hawaiÿi.

[Mgal/d, million gallons per day; discharges not used in record augmentation 

are underlined]

Date

Discharge in Mgal/d

Daily mean 

discharge at 

station 16097500

Combined 

discharges 

measured at 

stations 16088300 

and 16088500

02/24/11 7.8 10.5

03/02/11 3.4 5.12

03/22/11 3.9 8.79

04/15/11 3.3 4.43

06/02/11 4.8 6.99

07/05/11 4.3 5.94

07/28/11 5.7 6.32

09/02/11 3.1 3.80

09/26/11 2.6 2.30

04/04/12 4.0 4.96

05/22/12 3.1 2.81

20 Availability and Distribution of Low Flow in Anahola Stream, Kauaÿi, Hawaiÿi
Selection of Index Stations

Streamflow data from an index station are used to 

compute low-flow duration discharges at the LFPR stations. 

The index station is usually located along the same stream 

as the LFPR stations or nearby in drainage basins that are 

hydrologically similar to that of the LFPR stations. Hydrologic 

similarity between the drainage basins is defined by Searcy 

(1959, p. 14) as having the same probability of rainfall, and 

not necessarily the occurrence of concurrent rainfall events. 

However, remote index stations as far away as 50 mi have 

been used to estimate flow-duration discharges when longterm concurrent streamflow data are available at the stations. 

For this study, index stations were selected from a network of 

10 long-term continuous-record streamflow-gaging stations on 

the Island of Kauaÿi that were active from February 2011 to 

May 2012 (fig. 1), none of which were located on the studyarea streams. Selection of the index stations was based on 

(1) proximity of the continuous-record stations to the LFPR 

stations relative to the windward and leeward regions of the 

island; and (2) a minimum correlation coefficient of 0.80 

in the relations between the discharge measurements at the 

LFPR stations and the concurrent daily mean discharges at the 

continuous-record stations. The windward and leeward regions 

of the Island of Kauaÿi are defined in Yamanaga (1972, p.24). 

Streamflow-gaging station 16097500 on Halaulani 

Stream was used as the index station for the two LFPR 

stations on Anahola Stream, stations 16085500 and 16088300. 

Correlation coefficients, based on simple linear regression, 

in the relations between concurrent daily mean discharges at 

Table 9. Measured discharges at low-flow partial-record 

station 16081500 on Goldfish Stream and concurrent daily 

mean discharges at streamflow-gaging station 16071500 on 

left branch ÿÖpaekaÿa Stream, Kauaÿi, Hawaiÿi.

[Mgal/d, million gallons per day; discharges not used in record augmentation 

are underlined]

Date Daily mean discharge in Mgal/d

Station 16071500 Station 16081500

02/24/11 16 1.51

03/02/11 1.9 0.73

03/21/11 2.1 1.09

04/12/11 1.2 0.65

06/01/11 1.9 1.45

07/05/11 1.2 0.61

07/29/11 0.84 1.60

08/31/11 0.49 0.34

09/27/11 0.35 0.21

10/31/11 0.39 0.34

04/04/12 1.7 0.66

05/23/12 0.58 0.30

the index station and discharge measurements at the LFPR 

stations averaged 0.81. Streamflow-gaging station 16071500 

on the left branch of ÿÖpaekaÿa Stream was used as the index 

station for the LFPR stations on Keaÿoÿopu Stream (station 

16088500) and on Goldfish Stream (station 16081500). The 

correlation coefficients, based on simple linear regression, 

in the relation between concurrent daily mean discharges at 

the index station and discharge measurements at the LFPR 

stations averaged 0.91. On Anahola Stream immediately 

downstream from its confluence with Keaÿoÿopu Stream, 

the combined concurrent discharges measured at LFPR 

stations 16088300 and 16088500 were better correlated with 

the concurrent daily mean discharges at streamflow-gaging 

station 16097500—correlation coefficient of 0.76—than with 

the concurrent daily mean discharges at streamflow-gaging 

station 16071500. Therefore, station 16097500 was used as 

the index station for this location. Measured discharges at the 

LFPR stations and the concurrent daily mean discharges at the 

selected index stations are presented in tables 5 to 9. The base 

period used to compute low-flow duration discharges at the 

index stations was water years 1961–2011.

Record-Augmentation Techniques

The two record-augmentation techniques considered 

for use in this study are (1) the Maintenance of Variance 

Extension Type 1 (MOVE.1) technique described in Hirsch 

(1982); and (2) the graphical-correlation technique described 

in Searcy (1959, p.14). Both record-augmentation techniques 

assume that the relation between concurrent records at the 

index and LFPR stations is the same for any time period (Ries, 

1993, p.21). Selection of the appropriate record-augmentation 

technique for estimating low-flow duration discharges depends 

on the relation between discharge measurements at the LFPR 

station and the concurrent daily mean discharges at the index 

station. When little or no curvature is detected in the relation 

on a logarithmic plot, the MOVE.1 technique is used to 

estimate low-flow duration discharges. When curvature is 

evident in the relation, the graphical-correlation technique is 

used. Only limited curvature was evident in the logarithmic 

plots in this study and, therefore, the MOVE.1 technique was 

used to estimate low-flow duration discharges at all four of the 

LFPR stations.

The MOVE.1 technique applies the line of organic 

correlation regression method in developing the statistical 

relation. Compared with ordinary least squares and least 

normal squares regression methods, the line of organic 

correlation method has been shown by Hirsch and Gilroy 

(1984) and Helsel and Hirsch (2002) to be most appropriate 

in record augmentation. The procedure for the MOVE.1 

technique begins by transforming the concurrent discharges 

at the index and LFPR stations to base-10 logarithms, 

and computing the means and standard deviations of the 

logarithms. The low-flow duration discharges for the base 

period at the index station are also computed and transformed 

to base-10 logarithms. Estimates of low-flow duration 

discharges at the LFPR stations are determined using the 

Streamflow Characteristics 21
 

Yi = my + (xi − mx) (1)

sy

sx

where:

Yi is the base-10 logarithm of the estimated lowflow duration discharge at the LFPR station,

xi is the base-10 logarithm of the computed lowflow duration discharge at the index station,

my is the mean of the base-10 logarithms of the 

discharge measurements at the LFPR station,

mx is the mean of the base-10 logarithms of the 

concurrent daily mean discharges at the index station,

sy is the standard deviation of the base-10 

logarithms of the discharge measurements at the LFPR station, and

sx is the standard deviation of the base-10 

logarithms of the concurrent daily mean discharges at the index 

station.

The Streamflow Record Extension Facilitator (SREF) is a 

program developed by the USGS, in cooperation with the Federal 

Highway Administration and the Rhode Island Water Resources 

Board, that automates the MOVE.1 record-augmentation 

technique (Granato, 2009). To help the user evaluate the MOVE.1 

results, the SREF program computes several regression statistics. 

Those statistics include the correlation coefficient (r), residual 

error for each data point (ei), the leverage of each data point 

(hi), the mean square error (MSE), the root mean square error 

(RMSE), and a modified Nash-Sutcliff coefficient of efficiency 

(E). The correlation coefficient (Vogel and Stedinger, 1985; 

Helsel and Hirsch, 2002) is a measure of the strength of the linear 

relation between concurrent discharges at the index and LFPR 

stations. The residual error is the uncertainty in the estimated 

flow-duration discharges at the LFPR stations. The leverage of a 

data point measures the influence it has on the final estimates; a 

high leverage indicates the higher likelihood of an outlier in the 

discharge measurements made at the LFPR stations. The root 

mean square error (or standard deviation) is simply the square 

root of the mean square error (or variance), and it quantifies 

the difference between the estimated and measured discharges 

at the LFPR stations. The modified Nash-Sutcliff coefficient 

of efficiency (Legates and McCabe, 1999) ranges from minus 

infinity to 1. The closer a coefficient is to 1 the more accurately 

the statistical relation predicts low-flow duration discharges at the 

LFPR stations from the low-flow duration discharges at the index 

station. The equations used to compute these regression statistics 

can be found in Granato (2009). 

Low-Flow Duration Discharges

A summary of the index stations used and selected recordaugmentation regression statistics for the LFPR stations in 

Anahola and Goldfish Streams are included in table 10. Flowduration curves for index stations 16097500 and 16071500 are 

provided in figures 14 and 15, respectively. Selected low-flow 

duration discharges at the index stations and those estimated at 

the LFPR stations are summarized in table 11. Flow-duration 

discharge estimates less than the 95th-percentile discharge are 

not provided because those estimates are outside of the range of 

discharges measured at the LFPR stations during the study period 

of February 2011 to May 2012.

Anahola Stream upstream of upper intake.—At LFPR station 

16085500, a total of 11 discharge measurements were made 

during the study period and 9 measurements were used in record 

augmentation (table 5). Measurements made on April 13 and 15, 

2012, were taken during the same streamflow recession and the 

discharge measured on April 15 was selected to be used in record 

augmentation because it was taken during a seepage run to identify 

gains and losses in the stream. The measurement made on May 22, 

2012, was not used because it appeared to be an outlier that greatly 

deviated from the general trend that was consistent with the other 

nine measurements. Low-flow duration discharges estimated with 

the MOVE.1 technique ranged from 0.97 Mgal/d (Q95 discharge) 

to 2.7 Mgal/d (Q50 discharge). Measured discharges at the LFPR 

station that were used for record augmentation were between 

the flow-duration percentiles of 98 and 46 percent; therefore, the 

measured discharges provide flow-duration estimates that are 

representative of the low-flow conditions on Anahola Stream 

upstream of the upper intake.

Anahola Stream at confluence.—At LFPR station 16088300, 

11 discharge measurements were made during the study period 

and 9 of the measurements were used in record augmentation 

(table 6). Measurements made on February 24 and March 22, 

2011, were not used because the hydrograph from index station 

16097500 indicated possible runoff occurring during the time 

that the discharge measurements were being made. Low-flow 

duration discharges estimated with the MOVE.1 technique ranged 

from 1.7 Mgal/d (Q95 discharge) to 4.2 Mgal/d (Q50 discharge). 

Measured discharges at the LFPR station that were used for record 

augmentation generally fell between the flow-duration percentiles 

of 97 and 45 percent; therefore, the measured discharges provide 

flow-duration estimates that are representative of the low-flow 

conditions on Anahola Stream immediately upstream of its 

confluence with Keaÿoÿopu Stream.

Keaÿoÿopu Stream at confluence.—At LFPR station 

16088500, 11 discharge measurements were made during the 

study period, and 9 of the measurements were used in record 

augmentation (table 7). Discharge measurements made on 

February 24 and March 22, 2011, were not used because the 

hydrograph from index station 16071500 indicated possible runoff 

occurring during the time that the discharge measurements were 

being made. Only five of the nine usable discharge measurements 

made at the LFPR station were greater than the median discharge. 

The highest measured flow was 2.35 Mgal/d, which was about a 

Q20 discharge. Typically, the runoff component of total streamflow, 

represented in a flow-duration curve as the area between the 

total-flow and base-flow curves, becomes substantial at discharges 

greater than the median discharge. This is clearly illustrated in the 

flow-duration curve for station 16097500 on Halaulani Stream 

(fig. 14); hence, low-flow duration discharges usually span the 

range between the Q95 to Q50 discharges. However, the fairly 

MOVE.1 formula (equation 1) and then converted to the 

original (not log-transformed) units of measurement in 

million gallons per day.

22 Availability and Distribution of Low Flow in Anahola Stream, Kauaÿi, Hawaiÿi
flat slope of the flow-duration curve for index station 16071500 

(fig.15) indicates that low-flow conditions could possibly occur in 

the range between the Q95 to Q20 discharges. Low-flow duration 

discharges estimated with the MOVE.1 technique ranged from 

0.76 Mgal/d (Q95 discharge) to 2.4 Mgal/d (Q20 discharge). All 

of the discharge measurements made at the LFPR station were 

between the Q96 to Q20 discharges; therefore, the measured 

discharges provide flow-duration estimates that are representative 

of the low-flow conditions on Keaÿoÿopu Stream at the confluence.

Anahola Stream immediately downstream of confluence.—

On Anahola Stream immediately downstream of its confluence 

with Keaÿoÿopu Stream, the concurrent discharge measurements 

made at LFPR stations 16088300 and 16088500 were combined 

to represent the estimated discharge at that location (table 8). 

Eleven concurrent sets of discharge measurements were made 

at stations 16088300 and 16088500, and nine of those sets were 

used in record augmentation. Measurements made on February 

24 and March 22, 2011, were not used because the hydrograph 

from index stations 16097500 and 16071500 indicated possible 

runoff occurring during the time that the discharge measurements 

were being made. Low-flow duration discharges estimated with 

the MOVE.1 technique ranged from 2.7 Mgal/d (Q95 discharge) 

to 6.3 Mgal/d (Q50 discharge). Combined discharges measured 

at LFPR stations 16088300 and 16088500 that were used for 

record augmentation generally were between the flow-duration 

percentiles of 98 and 45 percent; therefore, the measured 

discharges provide flow-duration estimates that are representative 

of the low-flow conditions on Anahola Stream immediately 

downstream of its confluence with Keaÿoÿopu Stream.

Goldfish Stream upstream of Kaneha Reservoir.—A total of 

12 discharge measurements were made at LFPR station 16081500 

during the study period and 9 of the measurements were used 

Table 10. Index stations, record-augmentation technique, and selected regression statistics for the low-flow partial-record 

stations in Anahola and Goldfish Streams, Kauaÿi, Hawaiÿi.

[LFPR, low-flow partial-record; ID, identifier; r; correlation coefficient; RMSE, root mean square error; E, modified Nash-Sutcliff coefficient of efficiency (Legates 

and McCabe, 1999); MOVE.1; Maintenance of Variance Extension Type 1 record-augmentation technique (Hirsch, 1982)]

LFPR station ID Index station ID Record-augmentation technique Regression statistics

r RMSE E

16085500 16097500 MOVE.1 0.89 0.090 0.51

16088300 16097500 MOVE.1 0.91 0.076 0.52

16088500 16071500 MOVE.1 0.96 0.054 0.70

883+885a 16097500 MOVE.1 0.88 0.085 0.50

16081500 16071500 MOVE.1 0.95 0.077 0.69

a

 Flow-duration discharges at Anahola Stream immediately downstream of its confluence with Keaÿoÿopu Stream were estimated using the combined 

discharges measured at LFPR stations 16088300 and 16088500 during the study period of February 2011 to May 2012.

Table 11. Selected flow-duration discharges at the index stations and estimated flow-duration discharges at the low-flow 

partial record stations for water years 1961–2011, Kauaÿi, Hawaiÿi.

[Mgal/d, million gallons per day; --, not applicable]

Percentage of time 

indicated flow 

equaled or exceeded

Index stationsa

(Mgal/d)

Low-flow partial-record stations

(Mgal/d)

16097500 16071500 16085500 16088300 16088500 883+885b 16081500

95 2.6 0.33 0.97 1.7 0.76 2.7 0.23

90 2.9 0.41 1.2 2.0 0.87 3.1 0.27

85 3.1 0.47 1.3 2.2 0.96 3.4 0.30

80 3.3 0.53 1.4 2.4 1.0 3.8 0.33

75 3.5 0.59 1.6 2.7 1.1 4.1 0.35

70 3.7 0.65 1.8 3.0 1.2 4.6 0.38

65 3.9 0.78 1.9 3.2 1.3 4.9 0.43

60 4.1 0.84 2.2 3.5 1.4 5.3 0.46

55 4.4 0.90 2.4 3.8 1.5 5.8 0.49

50 4.6 1.0 2.7 4.2 1.6 6.3 0.54

45 -- 1.1 -- -- 1.7 -- 0.56

40 -- 1.2 -- -- 1.8 -- 0.61

30 -- 1.5 -- -- 2.0 -- 0.71

20 -- 1.9 -- -- 2.4 -- 0.84 a

 Selected flow-duration discharges for index stations computed from water years 1961–2011.

b

 Flow-duration discharges at Anahola Stream immediately downstream of its confluence with Keaÿoÿopu Stream were estimated using the combined discharges 

measured at LFPR stations 16088300 and 16088500 during the study period of February 2011 to May 2012. These flow-duration estimates may not correspond to the 

values resulting from the addition of the flow-duration discharges of LFPR stations 16088300 and 16088500 because of differences related to the timing of flows in 

tributary Keaÿoÿopu Stream and main channel of Anahola Stream. This is reflected in the use of different index stations for LFPR stations 16088300 and 16088500.

Streamflow Characteristics 23
in record augmentation (table 9). Discharge 

measurements made on February 24, June 

1, and July 29, 2011, were not used because 

the hydrograph from index station 16071500 

indicated possible runoff occurring during 

the time that the discharge measurements 

were being made. Although five of the nine 

usable measurements made at the LFPR 

station were higher than the median discharge, 

low-flow conditions could occur in the 

range between the Q95 to Q20 discharges 

as illustrated in the flow-duration curve for 

index station 16071500 (fig. 15). Lowflow duration discharges estimated with 

the MOVE.1 technique ranged from 0.23 

Mgal/d (Q95 discharge) to 0.84 Mgal/d (Q20

discharge). All except one of the discharge 

measurements made at the LFPR station 

were between the Q97 to Q20 discharges. 

The highest measured flow was 1.09 

Mgal/d, which was about a Q12 discharge. 

This measurement was included in the 

record-augmentation analysis because it 

was made under stable-flow conditions 

and runoff appeared to be minimal based 

on the flow-duration curve for index 

station 16071500. Therefore, the measured 

discharges provide flow-duration estimates 

that are representative of the low-flow 

conditions on Goldfish Stream.

Natural Low-Flow Distribution

Local geologic and climatic settings 

have an effect on groundwater and surfacewater flows. The varying interaction 

of these two bodies of water can affect 

the distribution of flow along a stream. 

Different reaches of the same stream can 

either gain water or lose water. When the 

water table is above the streambed, the 

stream can gain water as groundwater 

discharges into the stream. When the water 

table is below the streambed, flow in the 

stream can discharge to the underlying 

groundwater body.

Seepage Runs

Seepage runs are typically conducted 

to identify gaining and losing reaches 

of a stream. A seepage run consists of 

making multiple discharge measurements, 

preferably on the same day, at selected 

sites along the stream. The discharge 

measurements should be made when 

Figure 15. Plot showing flow-duration curves for total flow 

and base flow at streamflow-gaging station 16071500 on left 

branch ÿÖpaekaÿa Stream, Kauaÿi, Hawaiÿi, for water years with 

complete record during 1961–2011.

Figure 14. Plot showing flow-duration curves for total flow and 

base flow at streamflow-gaging station 16097500 on Halaulani 

Stream, Kauaÿi, Hawaiÿi, for water years with complete record 

during 1961–2011.

1

10

100

1 5 10 30 50 70 90 95 99

Daily mean discharge, in million gallons per day

Percentage of time indicated discharge was equaled or exceeded

Total flow

Base flow

100

0.1

1

10

1 5 10 30 50 70 90 95 99

Daily mean discharge, in million gallons per day

Percentage of time indicated discharge was equaled or exceeded

Total flow

Base flow

24 Availability and Distribution of Low Flow in Anahola Stream, Kauaÿi, Hawaiÿi
Table 12. Wet-season and dry-season seepage-run 

discharge measurements of Anahola Stream, Kauaÿi, Hawaiÿi.

[ID, identifier; Mgal/d, million gallons per day; --, not applicable]

Station IDa

Discharge, in Mgal/d

Wet season 

(04/15/2011)

Dry season 

(09/02/2011)

1 1.50 1.36

2 1.95 1.52

3 0.54 0.43

2 2.66 2.73

3 1.77 1.07

6 0.02 0

7 5.28 3.22

8 0.83 0.36

9 5.97 3.72

9a -- 0.14

10 6.01 4.71

11 0.91 0.72

12 8.47 5.29

a

 Refer to figure 13 for locations of the stations.

streamflow is generally stable. The existence of stableflow conditions during a seepage run can be determined by 

recording the stage during the time when each discharge 

measurement is being made, and at the beginning and end of 

the seepage run at a common location with a stable reference 

point from which the stage could be accurately measured.

For this study, two seepage runs were conducted—one 

in the wet season and one in the dry season—to characterize 

seasonal low-flow distribution along Anahola Stream. The 

wet-season seepage run for Anahola Stream was done on 

April 15, 2011, and the dry-season seepage run was done on 

September 2, 2011. The seepage-run stations established for 

this study are listed in table 4. An abbreviated station identifier 

(station ID) was assigned to the stations for ease of reference 

in the report. Discharge measurements were also made at the 

LFPR stations during the seepage runs. Among the 13 sites 

where discharges were measured during the seepage runs on 

Anahola Stream, 7 were in the main channel, 5 were in the 

tributaries, and 1 was in Lower Anahola Ditch. The station 

at the highest altitude (860 ft) was LFPR station 16085500 

and the station at the lowest altitude (70 ft, station 12) was 

upstream from the confluence of Anahola Stream and tributary 

Kaÿalula Stream. The station in Lower Anahola Ditch (station 

9a) was established during the dry-season seepage run because 

water was observed flowing into the ditch at that time.

Flow conditions during the seepage runs were 

documented by recording the stage during each discharge 

measurement, and by recording the stage relative to a 

common reference point at the start and near the end of the 

seepage runs. The reference point was a pin installed at the 

discontinued streamflow-gaging station located immediately 

upstream from the Lower Anahola Ditch diversion intake 

(station 16089000). All discharge measurements were made 

during undiverted conditions, or when any streamflow that 

may have seeped into the abandoned diversion intakes was 

returned to the stream downstream from the intakes. The 

existence of potential return flows was documented during 

the reconnaissance survey, and the seepage run stations 

were selected accordingly. For both seepage runs, the 

estimated seepage gains and losses in the main channel of 

Anahola Stream were computed as the difference between 

the discharges measured at the upstream and downstream 

stations, excluding flow contributed from tributaries. During 

the seepage runs, streamflow gains and losses were estimated 

along a 6.1-mi reach of Anahola Stream.

Wet Season. —The wet-season seepage run consisted 

of 12 discharge measurements (table 12, fig. 16). During the 

period when the first nine measurements were made, stage 

readings from the reference point and during each discharge 

measurement did not change, indicating that streamflow was 

stable despite the light showers that occurred intermittently 

throughout the morning and early afternoon hours. Discharge 

measurements in the 0.6-mi reach between stations 1 and 2 

indicated a gain in flow of 0.45 Mgal/d, representing a 

30-percent increase in flow from the upstream site to the 

downstream site. This gain included seepage flows observed 

from the left bank of the stream at altitudes of 790 and 760 ft, 

which were too low to measure with the available equipment. 

An unknown amount of flow was diverted into the Upper 

Anahola Ditch at the diversion intake. Because the ditch was 

in disrepair, a majority of the diverted flow was observed 

to have returned to the stream upstream from station 2 at 

an altitude of 760 ft or about 0.2 mi downstream from the 

upper intake. In the 2.3-mi reach between stations 2 and 4, 

the stream had seepage gains of 0.17 Mgal/d, or a 9-percent 

increase in flow between the two stations—which included 

several surface inflows along the reach that were too low 

to measure with the available equipment. In addition to the 

seepage gains of 0.17 Mgal/d, a tributary on the left bank at 

an altitude of 680 ft (station 3) contributed an additional 0.54 

Mgal/d of flow in the reach. Discharge measurements in the 

0.3-mi reach between stations 4 and 7 showed a seepage gain 

of 0.83 Mgal/d, a 19-percent increase in flow between the 

upstream and downstream sites. This seepage gain excluded 

flows contributed from two tributaries within this reach, 

including Keaÿoÿopu Stream that had a flow of 1.77 Mgal/d 

(station 5) and a smaller left-bank tributary that had a flow of 

0.02 Mgal/d (station 6). In the 0.5-mi reach between stations 

7 and 9, the stream lost about 3 percent (0.14 Mgal/d) of its 

total flow that was measured at the upstream station, excluding 

inflow of 0.83 Mgal/d from a right-bank tributary (station 8). 

Station 9 was immediately downstream from a wide raised 

gravel bed (fig.17) that directed a majority of the flow to the 

left side of the stream where the discharge measurement was 

made. The condition may have resulted in an unquantified 

amount of subsurface flow that bypassed station 9.

Streamflow Characteristics 25
Figure 16. Maps showing results of seepage runs on Anahola Stream, Kauaÿi, Hawaiÿi. A. Wet-season seepage-run 

results, 4/15/2011. B. Dry-season seepage-run results, 9/2/2011.

Kalalea Mountains

LowerAnahola Ditch

Anahola Str

Keälia Ditch

Keaÿoÿopu Str

Anahola Str

Kaÿalula Str

Kaupaku Str

Goldfish Stream

UpperAnahola

Ditch

Kaneha Ditch

1

2 3

10

11 12

Kalalea Mountains

LowerAnahola Ditch

Anahola Str

Keälia Ditch

Keaÿoÿopu Str

Anahola Str

Kaÿalula Str

Kaupaku Str

Goldfish Stream

UpperAnahola

Ditch

Kaneha Ditch

1

2 3

10

11 12

159°21'

22°9'

22°8'

159°21'

22°9'

22°8'

5

4

6

7 8 9

5

4

6

7 8 9

9a

EXPLANATION

2

11

+0.44

-0.14

0 1 2 MILES

0 1 2 KILOMETERS

+0.45

+0.17 +0.04

+1.55

A. Wet-season seepage run, 4/15/2011

+0.16

+0.78 +0.85

-0.14

-0.58

+0.28

+0.83

-0.14

B. Dry-season seepage run, 9/2/2011

Base modified from U.S. Geological Survey digital

data. Universal Transverse Mercator projection,

zone 4, North American Datum 1983.

Study area drainage-basin

boundariess

Makee diversion system 

near study area

Seepage-run measurement 

stations and identifier

Main channel

Tributary and ditch

Seepage-run stream reachesNumber shows water gain or

loss in million gallons per day. 

Gains or losses in reach exclude

inflows from tributaries. 

Gaining reach

Losing reach

26 Availability and Distribution of Low Flow in Anahola Stream, Kauaÿi, Hawaiÿi
Discharge measurements for stations 10, 11, and 12, 

in the lower reaches of Anahola Stream, were made in the 

late-afternoon hours when rainfall was more frequent. These 

measurements indicated Anahola Stream continued to gain 

flow; however, most of the flow was gained downstream 

from station 10. In the 1.4-mi reach between stations 9 and 

10, the stream gained a flow of 0.04 Mgal/d, representing 

less than 1-percent increase in flow from the upstream site 

to the downstream site. In the 1.1-mi reach between stations 

10 and 12, the stream gained a flow of 1.55 Mgal/d, or a 

26-percent increase in flow between the two stations—which 

excluded the 0.91 Mgal/d of inflow measured at Kaupaku 

Stream (station 11). The measured gain downstream from 

station 10 may have been affected by localized rainfall that 

occurred during the time when the discharge measurements 

were made. Two consecutive discharge measurements 

were made at station 12; the measured flows for the first 

and second measurements were 8.60 and 8.47 Mgal/d, 

respectively. The first measurement was made after the field 

technicians noticed debris flowing downstream, indicating 

possible runoff that may have caused a rise in stage. The 

second measurement was made when the stage was receding 

by 0.03 ft; therefore, this measurement was likely more 

representative of pre-rain conditions. Although the discharge 

measurements for stations 10 and 12 were made at nearly 

the same time, the stage did not change at station 10. This 

further supported the assumption that localized rainfall may 

have occurred near tributary Kaupaku Stream, causing the 

stage in the stream to rise near station 12.

Dry Season. —The dry-season seepage run consisted 

of 13 discharge measurements (table 12, fig. 16). The 

measurements were made under stable-flow conditions 

because no change in stage was detected at the reference 

point at the start and end of the seepage run, and during 

the period when each discharge measurement was being 

made. During the seepage run, all the water in the stream 

was diverted into the Upper Anahola Ditch at the diversion 

intake, leaving the stream channel immediately downstream 

of the upper intake dry. The diverted flow was observed 

to have returned to the stream at 760 ft altitude or about 

0.2 mi downstream from the upper intake. Station 2 was 

located about 0.3 mi downstream from the location where 

the diverted flow returned to the stream. Discharge at station 

2 was assumed to represent the total natural streamflow in 

Anahola Stream. Seepage-run discharge measurements show 

that the 0.6-mi reach between stations 1 and 2 gained a flow 

of 0.16 Mgal/d, representing a 12-percent increase in flow 

from the upstream site to the downstream site. All of this 

gain occurred downstream from the dry reach and between 

the point of return flow and station 2. Between stations 2 

and 4, the 2.3-mi reach had seepage gains of 0.78 Mgal/d, 

representing a 51-percent increase in flow between the two 

stations. In addition to the seepage gains of 0.78 Mgal/d, 

a tributary on the left bank at altitude 680 ft (station 3) 

contributed an additional 0.43 Mgal/d in this reach. Between 

stations 4 and 7, tributary Keaÿoÿopu Stream (station 5) 

contributed 1.07 Mgal/d to the total flow, and Anahola 

Stream had seepage losses of 15 percent (0.58 Mgal/d) 

of its total flow in the 0.3-mi reach downstream from the 

confluence. Station 7 was immediately downstream from 

a raised gravel bed, similar to the gravel bed upstream of 

station 9, which directed a majority of the flow to the left 

side of the stream where the discharge was measured. The 

condition may have resulted in an unquantified amount 

of subsurface flow that bypassed station 7. Discharge 

measurements in the 0.5-mi reach between stations 7 

and 9 show a seepage gain in flow of 0.28 Mgal/d, which 

represents a 9-percent increase in flow from the upstream 

site to the downstream site. This gain excluded the 0.36 

Mgal/d of inflow from the right-bank tributary (station 8). 

Station 9a was located in Lower Anahola Ditch to measure 

flow diverted from Anahola Stream into the ditch. A 

measured flow of about 0.14 Mgal/d at station 9a returned 

to the stream about 600 ft downstream of the lower intake 

and downstream from station 9. The combined discharge 

at stations 9 and 9a was considered the total natural flow 

in the stream downstream from the lower intake. Between 

stations 9 and 10, the 1.4-mi reach gained a flow of 0.85 

Mgal/d, representing a 22-percent increase in flow from 

the upstream site to the downstream site. Discharge 

measurements in the 1.1-mi reach between stations 10 and 

12 indicated a seepage loss of 0.14 Mgal/d, representing 

a 3-percent decrease in flow from the upstream site to the 

downstream site. Kaupaku Stream (station 11) contributed a 

flow of 0.72 Mgal/d within this reach.

Results of the seepage runs show that Anahola Stream 

was generally a gaining stream under natural low-flow 

conditions. According to the flow-duration discharges 

estimated with the record-augmentation technique, flows 

measured at the LFPR stations on the main channel of 

Anahola Stream during the wet-season seepage run were 

between the Q72 to Q78 discharges and flows measured 

during the dry-season seepage run were at about the Q80

discharge. Therefore, discharge measurements taken 

during the seepage runs were representative of base-flow 

conditions. During the wet-season seepage run, Anahola 

Stream at the downstream-most station (upstream of 

tributary Kaÿalula Stream) had more than five times the 

flow that was measured at the station upstream of the upper 

intake (seepage-run station 1). In the 6.1-mi seepage-run 

reach, the estimated total gain including tributary inflow 

was 6.97 Mgal/d. About 42 percent of that gain was from 

groundwater discharge to the main channel of Anahola 

Stream. During the dry-season seepage run, about 34 

percent of the estimated total gain (3.93 Mgal/d) was from 

groundwater discharge to the main channel of Anahola 

Stream. The relatively large amounts of groundwater 

discharge to Anahola Stream is evidence that the aquifer 

system in the Anahola drainage basin may be similar to that 

of the southern Lïhuÿe Basin, which is characterized by 

low-permeability (low hydraulic conductivity) lava flows 

saturated to near land surface.

Streamflow Characteristics 27
Streamflow Availability Scenarios 

Seepage-run discharge measurements can be used to 

estimate surface-water availability under regulated conditions 

of the stream if parts of the Makee diversion system—upper 

and lower intakes—in the study area are restored in the future. 

For example, during the wet-season seepage run, 1.50 Mgal/d 

of flow was measured upstream of the upper intake and 5.97 

Mgal/d of flow was measured near the lower intake at station 

9 (table 12). In the case that all the water in the stream is 

diverted at the upper intake, the amount of water remaining 

in the stream near the lower intake would be 5.97 Mgal/d 

less 1.50 Mgal/d (amount diverted at the upper intake), or 

4.47 Mgal/d. In the case that all the water is diverted at the 

upper and lower intakes, the amount of water remaining in 

the stream at the downstream-most discharge-measurement 

location on Anahola Stream (station 12, fig. 16) would be 8.47 

Mgal/d (discharge measured at station 12) less 1.50 Mgal/d 

(amount diverted at the upper intake) and 4.47 Mgal/d (amount 

diverted at the lower intake), or 2.50 Mgal/d. These scenarios 

assume that the groundwater gains observed during the wetseason seepage run are representative of groundwater gains in 

Anahola Stream for the period when water is diverted.

The Hawaii State Water Code mandates that the 

Commission on Water Resource Management (CWRM) 

establish a statewide instream-use protection program 

(Chapter 174C-71, Hawaii Revised Statutes) for the purpose 

of protecting instream uses. The principal mechanism that the 

CWRM has for protecting these instream uses is to establish 

instream-flow standards. “Each instream flow standard shall 

describe the flows necessary to protect the public interest 

in the particular stream. Flows shall be expressed in terms 

of variable flows of water necessary to protect adequately 

fishery, wildlife, recreational, aesthetic, scenic, or other 

beneficial instream uses in the stream in light of existing 

and potential water developments including the economic 

impact of restriction of such use” (Chapter 174C-71, Hawaii 

Revised Statutes). The amount of surface water available for 

agricultural use in the Anahola Stream drainage basin may be 

reduced when CWRM establishes an instream-flow standard 

for Anahola Stream. 

Estimated, natural flow-duration curves can be adjusted, 

based on a given instream-flow standard, to determine how 

much water is available for agricultural use. A discharge 

equal to the instream-flow standard is required to remain 

in the stream at a specific location and, therefore, is not 

available for offstream uses such as agriculture. The estimated, 

natural flow-duration discharge less the discharge equal to 

the instream-flow standard is the amount of water available 

for agricultural use. Low-flow duration discharges estimated 

at the LFPR stations can be used to assess the amount of 

water available under low-flow conditions in the case that 

the instream-flow standard is established at one of the 

LFPR stations on Anahola Stream. The amount of surface 

water available for agricultural use upstream of the upper 

intake (station 16085500), between 50 and 95 percent of the 

time, given a variety of instream-flow standards potentially 

established by the CWRM at that location is shown in figure 

18. The estimated, natural flow-duration discharges at this 

LFPR station that were adjusted to compute surface-water 

availability for agricultural use are presented in table 11. In the 

hypothetical case that no instream-flow standard is established 

Flow Flow

Gravel bed Gravel bed

Figure 17. Photograph of 

raised gravel bed on the right 

bank immediately upstream 

of seepage-run measurement 

station 220854159210601 

(station 9) on Anahola 

Stream, Kauaÿi, Hawaiÿi.

28 Availability and Distribution of Low Flow in Anahola Stream, Kauaÿi, Hawaiÿi
in Anahola Stream and the stream is allowed to run dry, the 

uppermost curve in figure 18 would represent the amount of 

water available upstream of the upper intake, between 50 and 

95 percent of the time, for agricultural use. The four additional 

curves represent the amount of water available for agricultural 

use upstream of the upper intake when the Q95, Q90, Q80, 

and Q70 discharges estimated at station 16085500 (table 11) 

are flows required by CWRM to remain in the stream. For 

example, if the instream-flow standard established upstream 

of the upper intake at station 16085500 is the Q95 discharge 

of 0.97 Mgal/d, no diversion of water may occur 5 percent 

of the time, corresponding to when the flow in the stream is 

0.97 Mgal/d or less. The amount of water potentially available 

for diversion at the upper intake would be greater than or 

equal to 1.7 Mgal/d 50 percent of the time. If the instreamflow standard established is the Q70 discharge of 1.8 Mgal/d, 

no diversion of water may occur 30 percent of the time, 

corresponding to when the flow in the stream is 1.8 Mgal/d or 

less. The amount of water potentially available for diversion 

at the upper intake would be greater than or equal to 0.90 

Mgal/d 50 percent of the time. Generally, the amount of water 

available for agricultural use would decrease as the amount of 

water required to remain in the stream increases. 

Limitations of Approach

Low-flow duration discharges at the LFPR stations were 

estimated using the MOVE.1 record-augmentation technique. 

The accuracy of the estimates is largely associated with (1) 

the strength of the correlation between concurrent discharges 

at the index and LFPR stations; (2) the number of LFPR 

measurements available for record-augmentation analysis; 

Figure 18. Plot showing flow-duration 

curves indicating the amount of flow 

available for agricultural use at the Upper 

Anahola Ditch diversion intake, Kauaÿi, 

Hawaiÿi, based on data for water years 

1961–2011 under a variety of potential 

instream-flow standards. 

and (3) how accurately the period of record (base period) 

from which the flow-duration discharges at the index stations 

were computed represents long-term flow conditions. Selected 

regression statistics computed by the SREF program that help 

to evaluate the record-augmentation results are presented in 

table 10. Correlation coefficients (r) of the MOVE.1 statistical 

relations are between 0.88 and 0.96, indicating strong 

correlations between concurrent discharges at the index and 

LFPR stations. The relatively small RMSE values suggest that 

the statistical relations generally provide accurate predictions 

of the flow-duration discharges at the LFPR stations. The 

MOVE.1 statistical relations with index station 16071500 

appear to provide slightly more accurate low-flow duration 

estimates than the relations with index station 16097500, as 

indicated by generally higher coefficients of efficiency (E). 

The uncertainty of flow-duration discharges represented by 

these regression statistics should be considered minimums 

because the record-augmentation technique used does not 

consider the potential errors inherent in the daily mean 

discharge at the index stations and the discharge measurements 

made at the LFPR stations (Fontaine, 2003, p.35). A majority 

of the discharge measurements made at the LFPR stations 

were rated good or fair, which indicates that measurement 

errors of 5 to 8 percent were possible.

Each of the MOVE.1 statistical relations was developed 

based on nine discharge measurements made at the LFPR 

stations during the study period. These measured discharges 

were generally within flow percentiles between 95 and 45. 

Additional discharge measurements may increase the level 

of confidence of the estimated flow-duration discharges at 

the LFPR stations. The flow-duration statistics at the index 

stations and estimates at the LFPR stations are applicable to 

the base period over which they have been computed. For 

this study, 51 water years of streamflow data (1961—2011) 

not established

3.0

2.5

2.0

1.5

1.0

0.5

0 50 60 70 80 90 95

Daily mean discharge, in million gallons per day

Percentage of time indicated discharge was equaled or exceeded

Instream-flow standard in Mgal/d, 

million gallons per day 

Qxx, flow that has been equaled 

or exceeded xx percent of the 

time during the period 1961-2011

0.97 (Q95)

1.2 (Q90)

1.4 (Q80)

1.8 (Q70)

Limitations of Approach 29
were available at the index stations. Considering the length 

of record, the flow-duration statistics are considered to be 

reasonably representative of the long-term flow conditions 

at the index stations and provide flow-duration discharge 

estimates at the LFPR stations that are representative of longterm flow conditions. Extrapolation of flow-duration statistics 

beyond the base period assumes that the hydrologic condition 

of the streams during the extrapolation period is similar to the 

condition during the past 51 years.

Seepage gains and losses within a reach were computed 

as the difference between the upstream and downstream 

discharges, excluding any measured tributary inflows within 

the reach. Given the potential error inherent in the seepage-run 

discharge measurements, which could be as much as 5 to 8 

percent for measurements rated good and fair, the estimated 

seepage gains and losses may not accurately reflect the true 

gain or loss in flow within the reach. Measured tributary 

inflows within the reach introduce additional errors to the 

seepage gain and loss estimates. In the upper reaches of 

Anahola Stream, some of the estimated seepage gains include 

minor surface inflows from the banks that were too low to 

measure with the available equipment. Thus, the true gains in 

flow may be slightly lower than the estimated gains.

Summary and Conclusions

The purpose of this study is to provide information on 

the availability and distribution of natural low flow in Anahola 

Stream. Low-flow data were also collected from Goldfish 

Stream, a stream that discharges into Kaneha Reservoir. This 

information can be used for water-management decisions for 

the Anahola drainage basin. The availability and distribution 

of low flow was determined using a combination of discharge 

measurements made between February 2011 and May 2012 

at low-flow partial-record (LFPR) and seepage-run stations 

established at sites of interest. Reconnaissance-level biological 

surveys of Anahola Stream were conducted as part of the study 

to determine the distribution of native and nonnative aquatic 

stream fauna. Results of the biological surveys indicated the 

presence of the following native aquatic species in Anahola 

Stream: ÿoÿopu ÿakupa and ÿoÿopu naniha in the lower stream 

reaches surveyed; and ÿoÿopu näkea, ÿoÿopu nöpili, and ÿöpae 

kalaÿole in the middle and upper stream reaches surveyed. 

Nonnative aquatic species were found in all of the surveyed 

stream reaches along Anahola Stream.

For this study, four LFPR stations were established to 

characterize natural low-flow availability in the study-area 

streams. Three stations were established on Anahola Stream, 

one about 450 ft upstream from the Upper Anahola Ditch 

intake, one about 50 ft upstream from the confluence with 

tributary Keaÿoÿopu Stream, and one on tributary Keaÿoÿopu 

Stream about 80 ft upstream from the confluence with 

Anahola Stream. One station was established on Goldfish 

Stream about 0.4 mi upstream from the point of discharge 

into Kaneha Reservoir. Natural low-flow duration discharges 

were estimated at the LFPR stations using the MOVE.1 

record-augmentation technique. Low-flow conditions at 

the LFPR stations on the main channel of Anahola Stream 

were characterized by flow-duration discharges between the 

95th (Q95 discharge) and 50th (Q50 discharge) percentiles. 

The Q95 to Q50 discharges at the LFPR station on Anahola 

Stream upstream of the upper diversion intake ranged from 

0.97 to 2.7 Mgal/d, and those at the station on Anahola 

Stream upstream of the confluence with Keaÿoÿopu Stream 

ranged from 1.7 to 4.2 Mgal/d. Low-flow conditions at the 

LFPR stations on Keaÿoÿopu and Goldfish Streams were 

characterized by flow-duration discharges between the 

95th and 20th percentiles. The Q95 to Q20 discharges at the 

LFPR station on Keaÿoÿopu Stream ranged from 0.76 to 2.4 

Mgal/d, and that at the station on Goldfish Stream ranged 

from 0.23 to 0.84 Mgal/d. On Anahola Stream immediately 

downstream of its confluence with Keaÿoÿopu Stream, the Q95

to Q50 discharges ranged from 2.7 to 6.3 Mgal/d. These flowduration estimates are applicable to the base period (water 

years 1961–2011) over which they have been computed. 

Caution must be used when extrapolating flow-duration 

statistics beyond the base period as the hydrologic condition 

of the streams may change in the future.

Wet- and dry-season seepage runs were conducted to 

characterize seasonal low-flow distribution along Anahola 

Stream. About 12 to 13 discharge measurements were made 

during each seepage run. Results of the seepage runs indicate 

that Anahola Stream was generally a gaining stream under 

natural flow conditions. Discharges measured in the wetseason seepage run were generally higher and the total amount 

of groundwater gain was larger than that of the dry-season 

seepage run. During the wet-season seepage run, Anahola 

Stream at the downstream-most station had more than five 

times the flow that was measured at the station upstream of 

the upper intake. The estimated total gain (including tributary 

inflow) in the 6.1-mi seepage-run reach was 6.97 Mgal/d 

and about 42 percent of that gain was from groundwater 

discharge to the main channel of Anahola Stream. During the 

dry-season seepage run, about 34 percent of the estimated 

total gain (3.93 Mgal/d) was from groundwater discharge 

to the main channel of Anahola Stream. The relatively large 

amount of base flow (groundwater discharge) observed was 

a result of local hydrogeologic characteristics of the aquifer 

system, which may be similar to that of the southern Lïhuÿe 

Basin and characterized by low-permeability (low hydraulic 

conductivity) lava flows that are saturated to near land surface. 

In the reaches where estimated seepage flows were within 

the range of potential error associated with the discharge 

measurements, the estimated seepage flows may not represent 

the true seepage flows within the reaches.

Results of this study were used in scenarios that describe 

(1) surface-water availability under regulated conditions 

of Anahola Stream if the upper and lower intakes are 

restored in the future; and (2) amount of flow available for 

agricultural use at the upper intake under a variety of potential 

30 Availability and Distribution of Low Flow in Anahola Stream, Kauaÿi, Hawaiÿi
instream-flow standards established by the State of Hawaiÿi 

for the protection of instream uses. Based on the wet-season 

seepage-run discharge measurements, in the case that the 

upper intake diverts all the water (1.50 Mgal/d) in Anahola 

Stream, the amount of water remaining in the stream near 

the lower intake would be about 4.47 Mgal/d. The scenario 

assumes that the groundwater gains observed during the 

wet-season seepage run are representative of the groundwater 

gains in Anahola Stream for the period when water is diverted. 

Low-flow duration discharges estimated upstream of the upper 

intake on Anahola Stream were used to determine the amount 

of water available for agricultural use under a variety of 

instream-flow standard potentially established at that location. 

If the instream-flow standard established upstream of the 

upper intake is the Q95 discharge of 0.97 Mgal/d, no diversion 

of water may occur 5 percent of the time, corresponding to 

when the flow in the stream is 0.97 Mgal/d or less. The amount 

of water potentially available for diversion at the upper intake 

would be greater than or equal to 1.7 Mgal/d 50 percent of the 

time. Generally, the amount of water available for agricultural 

use would decrease as the amount of water required to remain 

in the stream increases.

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32 Availability and Distribution of Low Flow in Anahola Stream, Kauaÿi, Hawaiÿi
Menlo Park Publishing Service Center, California

Manuscript approved for publication, November 19, 2012

Edited by Larry J. Slack and Peter H. Stauffer

Design and layout by Jeanne S. DiLeo
Cheng and Wolff—Availability and Distribution of Low Flow in Anahola Stream, Kauaÿi, Hawaiÿi—Scientific Investigations Report 2012–5264