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CHARACTERIZATION OF THE PHYSICAL ENVIRONMENT IN HE'EIA
FISHPOND, 'OAHU, HAWAI'I
A THESIS SUBMITTED TO
THE GLOBAL ENVIRONMENTAL SCIENCE
UNDERGRADUATE DIVISION IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
BACHELOR OF SCIENCE
GLOBAL ENVIRONMENTAL SCIENCE
MAY 2010
ByLindsey R. Benjamin
Thesis Advisor
Margaret McManus
I certify that I have read this thesis and that, in my opinion, it is satisfactory in scope andquality as a thesis for the degree of Bachelor of Science in Global Environmental Science.
THESIS ADVISOR
Margaret McManusDepartment of Oceanography
ACKNOWLEDGEMENTS
I would like to thank Margaret McManus, Kathleen Ruttenberg, Chip Young, Becky
Briggs, Jane Schoonmaker, and Rene Tada for their support during the writing of this
thesis.
This research was supported by a grant/cooperative agreement from the National Oceanic
and Atmospheric Administration; projects R/EL-42 and R/AQ-84, which are sponsored
by the University of Hawaii Sea Grant College Program, SOEST, under Institutional
Grants NA05OAR4171048 and NA09OAR4170060 from NOAA Office of Sea Grant,
Department of Commerce. The views expressed herein are those of the authors and do
not necessarily reflect the views of NOAA or any of its subagencies. UNIHI-
SEAGRANT-XB-10-01.
ABSTRACT
iv
The physical characteristics of Heeia Fishpond are important in studying the fishpond
system as a whole. Information about the flow rates and water exchange, the forces
influencing water movement, and the physical gradients in the pond is essential to
understanding the environment. Acoustic current meters were placed at the pond makahas,
or openings, to collect data to make rating curves. Pressure sensors were used to collect
pressure data for both flow rate calculations and frequency spectra. A YSI probe was
used at the makaha and internal sites to monitor surface and bottom temperature and
salinity. The majority �3 10! of the water exchange with the environment occurs through
the northeast corner, through sites TM and OM1. Most of the variability in the water flux
is due to the tides, though a shift in the winds from Trade to Kona does have some effect.
Surface and bottom gradients in temperature and salinity are due to colder, low salinity
river inputs in the northwest and warmer, high salinity inputs along the eastern side of the
pond. This thesis forms a physical framework for the continuing biological and chemical
studies in He'eia Fishpond.
TABLE OF CONTENTS
Acknowledgements.Abstract.
List of Tables.
List of Figures.Chapter 1: Introduction.
Hawai'ian Fishponds.He'eia Fishpond.Circulation Studies of Fishponds.
Chapter 2: MethodsStudy Site........................................................Instrumentation..
Data AnalysesWater Temperature and Salinity
Chapter 3: Results.Time-Series .
Rating Curves.Spectra.Flux
The Effects of Kona Winds on Water Flux
Temperature....................................................Salinity
Chapter 4: DiscussionChapter 5: Conclusions.References.
.1v
v1
.4 5
.7
.7
.8
12
14
15
15
20
28
31
36
.....37
38
40
43
42
~Pa e
2. Makaha tidal data for 03/10/08 to 04/10/08.
3. Rating curve formulas for all makaha.
.....36
Table
1. Instrument properties.
4. Kona wind flux change.....
LIST OF TABLES
.10
16
27
v1
v11LIST OF FIGURES
~Pa e
1. Map of Heeia Fishpond with study points marked..
2. Timeline of instrument deployment.
3. Depth for all makaha for 10/03/08-10/04/08 17-19
4. Rating curves for all makaha. 21-26
5. Spectra for all makaha. 29-30
6. Flux for spring flood, spring ebb, neap flood, and neap ebb tides.
7. Temperature at the surface and bottom on 11/17/07
32-35
37-38
8. Salinity at the surface and bottom on 11/17/07. .....39
CHAPTER 1: INTRODUCTION
Hawai'ian Fishponds
Ancient fishponds:
Ancient Hawai'i had a system of integrated agricultural practices that stretched from
mauka to makai mountain to ocean!. The land was divided into strips called ahupua'a
from inland to ocean, which were managed as a whole unit. The ali'i, or kings, allowed
the konohiki, or chiefs, to manage the ahupua'a; these konohiki divided their ahupua'a
into smaller sections to be managed by 'ohana, or individual families Costa-Pierce 1987,
Wyban 1992!.
Fishponds were a part of this system beginning as early as 1200AD Wyban 1992!, with
pond workers living on the ahupua'a under control of the konohiki. Fish were extensively
raised in the ponds, and the catch was distributed to everyone involved with the
ahupua'a: ali'i, konohiki, 'ohana, and other pond workers Costa-Pierce 1987!.
Four distinct types of fishponds existed in ancient Hawai'i: loko i'a kalo taro fishponds!,
loko wai freshwater fishponds!, loko pu'uone brackish water fishponds!, and loko
kuapa seawater fishponds! Costa-Pierce 1987, Kikuchi 1976!. Loko i'a kalo were
freshwater ponds that combined kalo or taro farming with raising of freshwater fish,
prawns, and green algae. Kalo was planted in rows of mounded earth, creating corridors
for fish to swim. Loko wai were much like loko i'a kalo without the kalo, although they
frequently had a small connection to the sea, making them technically brackish ponds
Kikuchi 1976!. Freshwater fish, prawns, and some fish that move from sea to freshwater
milkfish, mullet! were grown in ponds that had been carved out of the natural
topography. In addition, an edible mud was produced in loko wai Wyban 1992!. Ponds
that were situated on land with stream inputs but connected to the sea by a ditch were
loko pu'uone. A sluice gate or makaha was usually present in the ditch so inputs from the
sea could be shut off if desired, and the pond was kept separated from the sea by mounds
of sand Wyban 1992!. A wide variety of fish that could acclimate to both fresh and salt
water were kept in loko pu'uone.
The final type of fishpond, loko kuapa, was unique to Hawai'i, and a great achievement
in mariculture Costa-Pierce 1987!. The pond consisted of a walled-off section of a bay
or protected reef Wyban 1992!. Makaha in these ponds were made of a fairly fine mesh
of plant material that allowed the very young fish to pass, but not older fish; the smaller
fish from the sea would enter the fishpond to feed on the algae cultivated there, and could
only leave if they did not grow too large to fit back through the mesh. Thus, the pond was
stocked by nature instead of by man. The walls around these ponds ranged from 46m to
1920m in length, and were made of rocks and fill Costa-Pierce 1987!. Usually the walls
were left porous, but in a few ponds coralline algae was cultivated in the wall; coralline
algae secretes limestone which acts as mortar, sealing the wall Wyban 1992!. The walls
of loko kuapa were sloped, with a greater slope on the seaward side of the wall to
dissipate wave energy. Ponds ranged in size from 1 to 523 acres Wyban 1992!
Post-contact influence on fishponds:
In 1819, King Kamehameha II abolished the kapu system, or Hawai'ian system of laws
and religion Kikuchi 1976!. This system had, among other things, ensured the ali'i
complete control over their lands, resources, and people. It had functioned as a barrier
between invasive Western culture and native Hawai'ian culture, keeping the Hawai'ian
lifestyle alive Kikuchi 1976!. With its abolition came changes in Hawai'ian culture that
eventually lead to a near total Westernization of Hawai'ians.
Before 1848, all the land and resources in Hawai'i were property of the ali'i. However, in
a legislative move known as the Great Mahele ' division' !, land became a commodity
that could be bought and sold Costa-Pierce 1987, Wyban 1992!. With this decision, the
integrated agricultural system fell apart as ahupua'a were no longer kept whole, and
anyone could purchase land for other purposes. Without the support of the rest of the
ahupua'a, and with fishponds now viewed as an economic venture as opposed to a food
source, fishponds rapidly fell into disuse. In 1873 there were an estimated 241 ponds,
with 24 ponds covering 1046 acres in Kane'ohe Bay, 'Oahu. By 1975, there were only 28
ponds in Hawai'i, with 25 on 'Oahu; there are at least remnants of 12, with 7 in
functional condition Wyban 1992, Devaney 1982, Kelly 1976!. Most fishponds in
Kane'ohe Bay were filled shortly after World War II Devaney 1982!.
He'eia Fishpond
He'eia Fishpond is an 88 acre loko kuapa located in Kane'ohe Bay, 'Oahu, built about
300 years ago Kelly 1976!. It has one of the longest walls of all the fishponds �000 feet!
surrounding it completely, even on the landward side Devaney 1982, Kelly 1975!. The
seaward side of the wall is 12 to 14 feet thick and includes coral to induce the growth of
coralline algae, making it watertight Wyban 1992, Kelly 1975!. Because of this, the
walls had to be kept in good shape to keep the water level in the pond above the
surrounding bay Kelly 1975!. There were two very major flood events that damaged the
walls of He'eia fishpond. The first, in May 1927, destroyed a section of the North West
wall; part of this destroyed wall makes an island in the pond Kelly 1975!. The second
event, in May 1965, destroyed a 600 foot section of the South West wall. He'eia fishpond
is one of the last two working fishponds on 'Oahu Yang 2000!.
Currently, He'eia fishpond is managed by Paepae o He'iea POH!, a nonprofit group
devoted to restoring and caring for the pond. POH is currently removing invasive
mangroves and repairing the section of the wall damaged in 1965 using traditional
building methods. POH grows six species of fish and 5 species of crab, though these
animals are fed as opposed to relying on the pond environment to provide for them.
Circulation Studies in Hawai'ian Fishponds
There are very few studies of circulation patterns or water transport in Hawai'ian
fishponds. Ertekin et al. �996! modeled the circulation in One Ali'i fishpond on
Moloka'i using the finite element method to solve the conservation of mass and
momentum equations. The circulation was modeled with only one of the two makaha
open, as well as with both open. The water velocity through the makaha was higher in the
case with only one open makaha, but the water in the pond was circulated more when
both makaha were open. Ertekin et al. �996! concluded that both the number of makaha
as well as their location in relation to the forces at work were important in determining
and controlling the circulation in the fishpond.
Yang �000! modeled the effects of stream runoff and winds on circulation in fishponds.
The same modeling method was used as in Ertekin et al. �996!, but yielded only
qualitative results. The magnitude of the effect of stream runoff was found to depend on
the amount of runoff; a small amount changes the purely-tidal circulation pattern only in
the area into which the stream empties, and the water velocities in this area are very
nearly equal to the stream velocity. A larger amount of runoff changes a greater portion
of the circulation pattern, and at very high runoff it causes water to flow directly from the
stream mouth to the makaha and out of the pond. Wind was found to generate small
waves within the fishpond, but it did not have much of an effect on the purely-tidal
circulation pattern. Outside the pond, the wind had a much greater effect on circulation.
Wind was found to alter the rate of water flow through the makaha by altering the flow
just outside the makaha in the surrounding waters. The effects of wind on the circulation
are larger for larger fishponds.
CHAPTER 2: METHODS
Study site
He'eia fishpond is a walled section of Kane'ohe Bay on the windward side of Oahu
Figure I!. There are four ocean-side openings in the wall of the pond, designated Triple
Makaha TM!, Ocean Makaha 1 OM1!, Ocean Break OB!, and Ocean Makaha 2 OM2!.
There are three openings connecting the freshwater source RIVER! to the pond,
designated River Makaha 1 RM1!, River Makaha 2 RM2!, and River Makaha 3 RM3!
Figure I!. TM, OM1, OM2, and RM3 are inakaha, or gated openings. OB and RM2 are
depressions in the wall that water flows over, and RM1 has very diffuse flow.
21.43
21.43
21.43
21.43
21.43
21.43
21.43
21.43
157.811 157 81 157 809 157.808 157 807 157 806
Figure 1. He'eia Fishpond with makaha and stakes marked. The red circles on the
perimeter of the pond represent makahas, the red circles in the interior of the pond
represent water sampling locations stakes!.
Instrumentation
Two Nortek Aquadopp. Profilers were used to measure current speed and direction as a
function of water depth. Three acoustic beams measure a current profile for the water
column. Pressure measurements are made with a pressure transducer on the instrument.
Three Sontek Argonaut-SW. instruments were used to measure water depth as well as
flow speed and direction. A vertical acoustic beam determines depth from scattering at
the surface, while two other acoustic beams measure two-dimensional water velocity.
HOBO pressure data loggers were used to measure pressure.
The instruments were deployed in the pond in the timeframe indicated in Figure 2. At TM,
a Nortek instrument was deployed from 08/30/07 to 11/13/07 and from 11/15/07 to
02/10/08, and a Nortek with co-located pressure sensor were on the site from 02/13/08 to
05/08/08. A Sontek instrument was deployed at OM1 from 09/13/07 to 11/13/07,
11/15/07 to 02/10/08, and from 02/13/08 to 05/08/08. Another Sontek instrument was
deployed at OB for the same time periods. At OM2, RIVER, RM1, and RM2, pressure
sensors were in place from 08/08/07 to 11/29/07, 02/26/08 to 05/08/08, and 05/18/08 to
09/01/08. In addition, a Sontek instrument was at RIVER from 09/13/07 to 11/13/07,
12/06/07 to 02/10/08, and from 02/13/08 to 05/08/08. A Nortek was in place at RM3
from 08/30/07 to 11/13/07, 11/15/07 to 02/10/08, and 03/05/08 to 05/08/08.
Wind and tide measurements come from Coconut Island in Kane'ohe Bay.
10
Sample RateInstrument Feature
current speed
current direction
every 15 minutesNortek
current speed
Sontek current direction every 15 minutes
depth
every 15 minutesHOBO pressure
temperaturecontinuouslyYSI
salinity
Table 1. Instrument type, measurement, and sample rate.
I l'L"LJL'I il.
!LILf
I L'
I 'U
C'rl
E
O
e
E
0
E
11
12Data Analyses
Calculation of flow rate:
Using the water speed and depth from either the Sontek or Nortek instruments along with
the makaha dimensions, flow rates in m /s were determined for each of the rectangular
makaha TM, OM1, OM2, RM3! from the equation:
P = wdv sin�!
where w is the makaha width, d is the water depth, v is the magnitude of the water
velocity, and 0 is the direction of the water flow, with 0 = 0 corresponding to flow
directly through the makaha. For OB, water flows over a flat wall, so the flow rate in m /s
was also determined by Equation I!, with w as the length of the wall instead of makaha
width, and only for d>0.86m the height of the wall!. For RIVER, water flows through an
irregularly-shaped bed. A profile of bed depth across the site was made, and the areal
aspect of Equation I!, wd, was calculated from the profile assuming water fills in the
deepest parts of the bed first. For RM2, the wall that water flows over is at an angle with
respect to the ground, so that the areal part of Equation I! was calculated in the same
way as RIVER.
Construction of rating curve: 13
Spectral analysis:
Spectral analysis is the evaluation of the frequency components of a time series signal to
determine patterns of cycles in the data. The depth data for each makaha or pressure data
converted to depth! were evaluated using Fourier transforms to make a spectrum of
power in terms of frequency.
Flux volume calculations:
In order to determine the importance of flow through each makaha through a tidal cycle,
flow volumes for spring flood, spring ebb, neap flood, and neap ebb tides were examined.
Pressure data from each part of a tidal cycle was converted to flow volume using the
rating curves, and the total flux through each makaha for spring flood tide, spring ebb
tide, neap flood tide, and neap ebb tide was determined.
A rating curve is a curve relating the discharge from a river or outlet to the stage or height
of the water at the outlet. The curve is usually given as discharge as a function of stage,
though stage is represented as the vertical axis and discharge as the horizontal axis.
To construct a rating curve, the flow rates calculated above were averaged for every
depth, giving average flow rate discharge! as a function of water depth stage!. Curves
were fitted to this data, forming rating curves.
Water Temperature and Salinity: 14
A YSI probe was used to create depth profiles at each of the sites during water sample
collection. The upper 20 cm and lower 20 cm temperature and salinity data were
averaged for each site to create surface and bottom averages. For each property, a
colorbar was designed to fit the data ranges necessary, and dots of the appropriate color
were plotted at the location of the sample site with a map of the fishpond superimposed
on top. An attempt was made to produce an interpolated colormap for each property;
however, the location of the data points made artifacts within the colormap which were
not present in the data.
CHAPTER 3: RESULTS 15
Time-Series
Wind
During the period between 03/10/08 and 04/10/08 winds were dominated by north east
trades 90'/o! Figure 3a!. Winds from the south west i.e. Kona winds! occurred 10'/o of
this period. Trade winds ranged from 0.8 to 9.4 m/s with an average wind speed of 11.0
m/s. Kona winds ranged from 0.2 to 1.7 m/s with an average wind speed of 0.7 m/s
Tide
The tides in this region are semi-diurnal and mixed. During the study period spring tides
occurred around 03/13/08, 03/27/08, and 04/10/08 and neap tide occurred around
03/20/08 and 04/03/08 Figure 3!. The average water depth in Kane'ohe Bay was 0.29 m,
with a maximal tidal range of 0.44 m. The average water depths and maximum tidal
ranges for each makaha are reported in Table 2. Across all sites, the average water depth
was 0.55 m and maximal tidal range was 0.41 m.
Table 2. Makaha tidal data for 03/10/08 to 04/10/08. 16
Makaha
Abbreviation m! Range m!
0.430.57TM
OM1 1.10 0.37
Ocean Break OB 0.490.89
Ocean Makaha 2 OM2 0.43 0.40
River 0.430.38RIVER
River Makaha 1 RM1 0.47 0.38
River Makaha 2 RM2 0.45 0.38
River Makaha 3 RM3 0.14 0.39
Makaha
Triple Makaha
Ocean Makaha 1
Average Water Depth Maximum Tidal
01
~ 05
- ~ 05
01
- ~ 15
-0 2
- ~ 25
-0 3
04/1 304/0603/3003/2303/1 603/09
15
�~ 5
003/09 ~ 4/1 3~ 4/06~ 3/30~ 3/23~ 3/1 6
15
05
0~ 3/09 04/1 3~ 4/06~ 3/30~ 3/23~ 3/1 6
15
05
~ 4/1 304/06~ 3/3003/2303/1 6~ 3/39
15
~ 5
003/09 ~ 4/1 304/06~ 3/30~ 3/23~ 3/1 6
15
05
~ 4/1 3~ 4/06~ 3/3003/33~ 3/1 6~ 3/09
15
~ 5
003/09 ~ 4/1 304/06~ 3/30~ 3/23~ 3/1 6
15
05
~ 4/1 3~ 4/06~ 3/30~ 3/3303/1 6~ 3/09
05
~ 309
003/09
Figure 3. Wind a!, predicted tide b!, and depth for TM c!, OM1 d!, OB e!, OM2 f!,
RIVER g!, RM1 h!, RM2 i!, and RM3 j! from 03/10/08 to 04/10/08.
Rating Curves 20
Rating curves for flow into and out of TM, OM1, OM2, OB, and RM3 were made.
RIVER and RM2 have only a single rating curve because of unidirectional flow. The
rating curves for TM in, TM out, OM1 in, OM1 out, OB in, OB out, and RIVER are
logarithmic curves of the form of:
y � b
�!x=ae '
where flow volume is x, water depth is y, a is the amplitude, b is the offset in the
horizontal asymptote, and c is the degree of curvature. The rating curves for OM2 in and
OM2 out are partial Gaussian curves of the form of:
- y-cj'
x = a+be �!
�!x = ay+ b
for flow volume x, depth y, slope a, and intercept b. The rating curve for RM3 in is an
asymmetric Gaussian curve formed by joining two partial Gaussian curves of the form
given in Equation �!. Actual formulas for the rating curves are given in Table 3.
where flow volume is x, depth is y, a is the horizontal displacement, b is the amplitude, c
is the offset in the peak, and d is the width of the bell. The rating curves for RM2 and
RM3 out are linear curves of the form:
09
0 ~
07
06
6 05
04
03
02
01
~ 2~ 1~ 000040 02 ~ 06discharge m3/sec
09
0 ~
07
06
6 05
04
03
02
01
~ 015~ 01~ 0050 ~ 02 0 025 ~ 03 ~ 035 ~ 04 ~ 045 005discharge m3/sec
22
15
~ 9 ~ 01 ~ 02 ~ 03 004 01
15
14
13
~ 9 002 ~ 04 ~ 08 0 08discharge m3/sec
~ 1 ~ 12 014
13E
12
F
12
~ 05 0 05 0 07 ~ 08 ~ 09discharge m3/ssc
23
12
6 m ~ 9
08
~ 7
7050201 ~ 30 40discharge m3/sec
13
12
E 5, 09
08
~ 7
~ 6
~ 5 605040201 ~ 30discharge m3/sec
24
07
~ 65
06
~ 55
05E
~ 45
04
~ 35
03
~ 25
02~ 35~ 30 2501~ 05 015 02
discharge m3/sec
07
E 05
04
03
020 ~ 2502~ 05 ~ 1 015
discharge m3/sec
09
085
0 ~
075
Ere 07
065
055
0505~ 40201 ~ 3
discharge m3/sec
~ 61
0 605
~ 6
60 595
~ 59
0 585
~ 58 ~ 45~ 4~ 350302~ 15~ 1 ~ 25discharge m3/sec
~ 9
0 85
~ ~
0 756
~ 7
0 65
~ 6
0 55 ~ 09~ 08~ 07~ 06~ 03~ 02~ ~ 1 004 ~ 05discharge m3/sec
26
0 55 0 ~ 04discharge m3!sec
Figure 4. Rating curves for TM in a!, TM out b!, OM1 in c!, OM1 out d!, OB in e!,
OB out f!, OM2 in g!, OM2 out h!, RIVER i!, RM2 j!, RM3 in k!, and RM3 out I!.
27
Site Direction Formula
x = 0.9+ 0.181og0.15
TM
x = 1.02+ 0.126 log0.18
Out
x =1.43+ 0.081og0.15
OM1
x = 1.38+ 0.061og0.005
Out
x = 0.9+ 0.07 log y!
OB
x = 0.44+ 0.08 log0.01
Out
y-o.vl!'
x = 0.75 + 0.18e
OM2
y-o.vs!'
x = 0.017+ 0.15eOut
x = 0.86+ 0.07 log0.34
RIVER Both
x = 0.06x+ 0.5755RM2 Both
y � 0.726!'
x = 0.03+ 0.058e '"' for x 0.726
y-o.vzo!'
x = 0.009+ 0.052e '"" for x ! 0.726RM3
x = 0.8 � 3.85yOut
Table 3. Formulas for rating curves given in Figure 4.
Spectra 28
The spectra show the frequency dependence of the water depth data Figure 5!. The
spectrum for TM shows strong signals at 12 and 24 hours, with a larger and sharper peak
at -0.5 days. The OM1 power spectrum has strong 12 and 24 hour signals, with the 24
hour signal having a larger spread. The spectrum for OB has a strong, slightly spread 24
hour signal with a weaker 12 hour signal. Strong 12 and 24 hour signals are present in the
OM2 spectrum, with the 12 hour signal having a sharper peak with a slightly larger
amplitude. The spectrum for RIVER shows strong, nearly equal signals at 12 and 24
hours, with the 24 hour peak having a larger spread. The RM1 power spectrum has strong
12 and 24 hour signals, with the 24 hour signal having a larger spread. The spectrum for
RM2 has a strong, slightly spread 24 hour signal with a strong, sharply peaked 12 hour
signal. Strong 12 and 24 hour signals are present in the RM3 spectrum, with the 12 hour
signal having a sharper peak with a slightly larger amplitude.
29
~ ~
Ere ~CLCL
W ~ 4CL
~ 2
00 105Penod Days!
~ ~
XE ~ 6CL
3 ~ 4
~ 2
100 5Penod Days!
E e QEo
3 04o
02
0 105Period� Days!
XE o Qoo
s 04o
02
00 105Period Days!
30
~ ~
E ~ 6CL
s 04CL
~ 2
0 4 5 6Penod Days!
~ ~
E 06CL
s ~ 4CL
~ 2
00 5Penod Days!
~ ~
Ee ~
s 04
~ 2
105Pened Days!
~ ~
6 ~ 6CL
a ~ 4CL
~ 2
00 105Pened Days!
Figure 5. Spectra for TM a!, OM1 b!, OB c!, OM2 d!, RIVER e!, RM1 fj, RM2 g!,
and RM3 h! from data from 03/10/08 to 04/10/08.
31Water Flux
The water flux through the makaha during spring flood tide Figure 5a! shows most water
passing through OM1 �.4 10 of the total flux during spring tide and neap tide!, RIVER
�.5 10!, and TM �.0 10!. A lower volume of water flows through OB �.6 10!, and a
negligible amount of flow moves through RM2, OM2, and RM3 channel �.5 to, 0.4 to,
and 0.2 10, respectively!. All makaha have water entering the pond with the exception of
RM3 during spring flood tide.
During spring ebb tide Figure 5b!, the greatest volume of water moves through OM1,
TM, and RIVER �2.5 10, 8.8 10, and 4.8 10, respectively!, while a negligible amount of
water moves through RM2, OB, OM2, and RM3 �.3 to, 1.3 to, 0.4 to, and 0.2 10,
respectively!. During spring ebb, all ocean-side makaha have water leaving the pond,
while all river-related makaha allow water to enter the pond.
During neap ebb tide Figure 5d!, the greatest volume of water flows through OM1, TM,
and RIVER �1.8 10, 8.3 10, and 7.1 /0, respectively!. A moderate to negligible amount of
During neap flood tide Figure 5c!, the greatest volume of water flows through OM1 and
TM �.8 10 and 4.8 10, respectively!. A moderate volume of water flows through OB, RM3,
and RIVER �.0 to, 2.5 to, and 2.4 10, respectively!, and a negligible amount of water
flows through RM2 and OM2 �.0 10 and 0.4 10, respectively!. During neap flood tide, all
makaha have water entering the pond with the exception of RM3.
32
water flows through OB, RM2, OM1, and RM3 �.2 to, 1.3 to, 0.3 to and 0.2',
respectively!. During neap ebb tide, all ocean-side rnakaha have water leaving the pond,
while the others have water entering the pond.
21 43
21 43
21 43
21 43
21 43
21 43
21 43
21 43
157 811 157 81 157.889 157 808 157 807 157 806
33
21. 43
21 43
21 43
21 43
21 43
21 43
21 43
21 43
157 811 157 81 157.809 157 808 157 807 157 806
34
21. 43
21 43
21 43
21 43
21 43
21 43
21 43
21 43
157 811 157 81 157.809 157 808 157 807 157 806
35
21. 43
21 43
21 43
21 43
2'I 43
21 43
21 43
21 43
157 811 157 81 157.809 157 808 157 807 157 806
Figure 6. Water flux as a percentage of total spring and neap water flux for spring flood
a!, spring ebb b!, neap flood c!, and neap ebb d!.
The Effects of Kona Winds on Water Flux 36
Kona Wind Flow % Change from Trade Wind Flow!Site
Flood Ebb
-43.9 13.0TM
-44.0OM1 17.3
-36.5OB 75.4
-33.8OM2 24.2
-24.2 22.7RIVER
20.1 20.1
-11.4RM3 409.6
During spring flood tide with Kona winds, flow through all sites was below normal
except RM2 and RM3, which were significantly increased. During spring ebb tide with
Kona winds, flow through all sites except RM3 was above normal.
As previously mentioned, trade winds dominated for the majority of the study 90%!.
Kona winds were present during 10% of the study. The volume of water moving through
each makaha was calculated for spring flood and spring ebb tides under Kona wind
conditions Table 4!.
Table 4. Kona wind and trade wind water flux comparison.
37Temperature
21 439
2621 438
25 75
25 521 437 25 25
25
24 7521 436
24 5
24 2521 435
24
23 75
21 434 23 5
23 25
2321 433
21 432
157 81 157 809 157 808 157 807 157 806
During water sampling on 11/17/07, water temperatures in the pond ranged from 23 to 26
degrees C Figure 7 a and b!. The surface temperatures are coldest at RM2 and OM2 and
warmest at S 1 and S3. The bottom temperatures are coldest at RM2 and OM2 and
warmest at Sl, S3, and OCN1. At S6, S8, S9, S13, OCN1, and OB, surface temperatures
are cooler than bottom temperatures.
38
21 439
2621 438 25. 75
25 5
21 437 25 25
25
21 436 24 75
24 5
24 2521 435 2423 75
21. 434 23 5
23 25
2321 433
21 432
157.81 157 809 157 808 157 807 157 806
Figure 7. Temperature on 11/17/07 at the surface a! and bottom b!.
Salinity
During sampling on 11/17/07, the salinity of the pond ranged from 0 to 33 PSU Figure 8
a and b!. At the surface, the salinity is lowest at RM1 and RM2 and highest near the
south-eastern corner of the pond. At the bottom, the salinity is lowest lowest at RM1 and
RM2 and highest near the south-eastern corner of the pond. Salinity at RM1 is
significantly higher at the bottom than at the surface. At both surface and bottom there is
a clear gradient between high and low salinities.
39
21 439
3321 438 3027
21 437 24
21
21 436 18
15
1221 435
21 434
21 433
21 432
157 81 157 809 157 808 157 807 157 806
21 439
3321 438 30
2721 437
24
21 436 18
15
1221 435
21 434
21 433
21 432
157 81 157 809 157 808 157 807 157 806
Figure 8. Salinity on 11/17/07 at the surface a! and bottom b!.
CHAPTER 4: DISCUSSION 40
In terms of flux during normal conditions, OM1 and TM allow the most water transport,
making the north east corner of the pond the most influential inlet/outlet area. The
RIVER site also shows fairly large flow volumes, particularly during neap ebb. Flux
through the north east corner of He'eia fishpond is greater during ebb tides than during
flood tides because of input from the river makaha; while water may back up during
flood tides to the river makaha, river flow is downstream and eventually into the pond.
When comparing the flux during normal conditions and the flux during Kona wind
conditions, interesting patterns emerge Table 3!. During flood tide, the trade wind fluxes
are all larger except for RM2 and RM3. During ebb tide, the fluxes are all smaller with
The spectra all have peaks at roughly 12 and 24 hours, thus the tidal forces appear to be
the most important force in the cyclical exchange of water between the pond and its water
sources/sinks. The sharpness of a spectral peak is indicative of the accuracy in timing.
That the 12 hour peaks are sharper than the 24 hour peaks could represent that the 12
hour cycle is more precise in its timing than the 24 hour cycle. In all the spectra except
OB, the 12 hour peak is larger in magnitude than the 24 hour peak. This anomaly is likely
again! due to the fact that OB is a wall instead of makaha, so it does not allow free
exchange at all times. Interestingly, even RIVER, RM1, RM2, and RM3 also show tidal
influences; this could be because the tide runs up the river and influences the river
makahas.
trade winds than with Kona winds. There does appear to be an influence on wind 41
direction on the flux through the makahas of the fishpond. Keeping in mind that south-
west Kona winds blow in the opposite direction as the north east trades winds.
Trade winds aid in the transport of water through makahas and into the fishpond during
spring tide. While Kona winds aid in the transport of water out of the pond during ebb
tides.
An obvious northwest-southeast temperature gradient exists on both the pond surface and
bottom. The temperatures in the northwest are colder than those in the south east. This
gradient is caused by the inflow of colder water from the river makaha and warmer water
from the ocean makaha.
There is a salinity gradient from the northwest to the eastern side of the pond. The
salinity of the river water is essentially 0, while the salinity of the ocean water is 33 PSU.
The gradient is from the river water input in the North West corner to the ocean water
inputs from the makaha TM, OM1, OB, and OM2! on the eastern side of the pond.
CHAPTER 5: CONCLUSIONS 42
The majority of the flux into and out of the pond �3 10! occurs at the northeast corner,
through TM and OM1. Inputs from the river through RM2 and RM3 make up only 7 10.
The other 30 10 flows over OB, or through OM 1 and the RIVER.
The winds force water movement into and out of the fishpond. Kona winds, which are a
reversal of the normal northeast trade winds, cause a -44 10 decrease in flow through TM
and OM1 during spring flood tide, when winds push against the water flowing into the
pond. Kona winds also cause a -15 10 increase in flow through TM and OM1 during
spring ebb tide, when winds push with the water flowing out of the pond.
There are northwest-southeast gradients in temperature and salinity in both the surface
and bottom waters of He'eia fishpond. Cold freshwater inputs from the river enter at the
northwest end of the pond, while warm saltwater enters from Kane'ohe Bay along the
eastern side of the pond.
The tides are a major force acting on He'eia fishpond, as evidenced by the strong -12 and
-24 hour signals in the frequency spectra that match the Hawai'ian mixed diurnal tides.
The spectra for all makaha show these strong signals, indicating that tides affect water
flowing through all makaha, even the river makahas.
43REFERENCES
Devaney, D.M. Kaneohe: A History of Change. Bess Press. 1983. 271p.
Ertekin, R. C., H. Sundararaghavan, and A. T. F. M. Van Stiphout �996!, Molokai
fishpond tidal circulation study, Technical Report OE Report No.: UHMOE�
96203, Sea Grant Report No.:UNIHI-SEA GRANT-TR-96-03, Dept. of Ocean
Engineering, University of Hawaii at Manoa.
Kelly, M. Heeia Fishpond, a Testament to Hawaiian Fish-Farming Technology.
Department of Anthropology document prepared for Pauahi Bishop Estate. Bernice
Pauahi Bishop Museum, Honolulu, Hawaii. 1976. 21p.
Kelly, M. Loko I'a o He'eia: Heeia Fishpond. Department of Anthropology document
prepared for Pauahi Bishop Estate. Bernice Pauahi Bishop Museum, Honolulu, Hawaii.
September 1975. 56p.
Kikuchi, W.K. �976!. Prehistoric Hawaiian Fishponds. Science 193 �250!. p 295-299.
Wyban, C.A. Tide and Current: Fishponds of Hawaii. University of Hawaii Press. 1992.
192p.
Costa-Pierce, B.A. �987!. Aquaculture in Ancient Hawaii. Bioscience 37 �!. p 320-331.
44
Yang, L. �000!. A circulation study of Hawaiian fishponds. Master thesis in ocean
engineering. University of Hawaii at Manoa.
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