Water Quality in Hilo Bay: County Proposal

WATER QUALITY IN HILO BAY

UNDER BASE AND STORM FLOW CONDITIONS

Overview: Hilo Bay waters have been known to exceed state water quality standards
since the late 1970s and were formally included on the US Environmental Protection
Agency?s (USEPA) 303(d) list of impaired waterbodies in 1998 (Koch et al. 2004).
Parameters exceeding standards include turbidity, nutrients, and fecal bacterial indicators.
The listing of Hilo Bay for nutrients and sediment has been determined solely by means
of visual assessment and not by direct measurements of these parameters.

Hawai`i County is committed to improving and restoring Hilo Bay?s ecosystem

and water quality. Correspondence from Mayor Harry Kim to the Army Corps of
Engineers (ACOE), dated January 20, 2005, requests assistance to ?improve the water
quality and circulation of Hilo Bay.? It was proposed that ACOE develop a computer
circulation model to investigate whether modifications to the breakwater ?or other
alternatives will improve the water quality? of Hilo Bay. The ACOE is committed to
developing a computer model to assess alternatives to improving water circulation within
the Bay; however, their plans do not include measuring water quality parameters
(turbidity, nutrients) within the Bay under different conditions (baseline vs. storm).
University of Hawai`i at Hilo (UHH) Marine Science Department proposes to collaborate
with Hawai`i County in conjunction with ACOE to collect essential water quality data to
better understand the relationship between water quality and circulation within Hilo Bay
and to use this data to accurately assess whether modifications to the breakwater will
improve water quality.

It is assumed that if circulation within Hilo Bay is enhanced, water quality will

improve; to date, the relationship between circulation and water quality has not been
established. More importantly, the source of turbidity, nutrients, and fecal bacterial
indicators within the Hilo Bay watershed, as well as, the response of the Bay to these
pollutants under base and storm flow conditions are unknown. The potential
effectiveness of remediation actions to improve the Hilo Bay?s water quality, like
modifying the breakwater, cannot be evaluated without knowledge about how the Bay
functions. To understand how Hilo Bay functions as an ecosystem, water quality and
circulation data are needed for the Bay, as well as water quality and discharge data for the
river draining into the Bay. UHH proposes to collect the baseline data on sediment and
nutrient inputs to the Bay, and to assess the response of the Bay to these inputs under
base and storm flow conditions. This information along with ACOE circulation data will
allow Hawai`i County to identify the best and most cost-effective remediation actions to
improve Hilo Bay water quality.

Background: In Hawai`i, there is a tremendous economic reliance on the quality and
health of coastlines. Hence, it is imperative that the fate and potential impacts of
terrestrial inputs to coastal waters are quantified. Hilo Bay is an important wildlife and
fishery area (HDOH 2000). It is also one of the longest, most accessible and least used
sand beaches on the Island of Hawai`i (Hawai`i Island Journal 2004). Only 10% of the
people who use this beach swim there (USEPA 2002), which stems from the fact that
Hilo Bay is thought to suffer from high turbidity and excessive nutrients. In fact, Hilo
Bay has been listed by HDOH and USEPA as one of the seven most troubled watersheds

in the state of Hawai`i having water quality below state and federal standards. Clearly,
more information on the water quality of the rivers draining into Hilo Bay, as well as, the
Bay itself, are needed for better management of this ecosystem.

Surprisingly, very little water quality data are available for Hilo Bay in contrast to

other Hawaiian estuaries like Kaneohe, Hanalei, and Nawiliwili Bays. Reports are scarce
and only one peer-reviewed paper exists for Hilo Bay (Silvius et al. 2005). Most water
quality data for Hilo Bay are from consultant reports for Environmental Assessments
(EA) and Environmental Impact Statements (EIS) from ACOE evaluations, and Hawai`i
Department of Health (HDOH) and the United States Geological Survey (USGS)
monitoring (Silvius et al. 2005). However, these studies were not designed to evaluate
how Hilo Bay operates under different conditions (i.e. baseflow vs. storms).

State of knowledge on Hilo Bay ? Hilo Bay is considered a salt wedge estuary

that is stratified with a freshwater surface layer existing up to a mile offshore (Dudley &
Hallacher 1991). This stratification is most pronounced during wet season when surface
runoff to Hilo Bay is high. The dense saline layer moves offshore at depth with the tide
and the upper freshwater layer is pushed shorewards by easterly and northeasterly trade
winds. There is minimal mixing between freshwaters and saltwater layers inside the
breakwater because wave energy is low. Low wave energy also allows sediments carried
by the rivers to settle out into the lower salty layer, where they may be transported back
into the Bay with the incoming tide. Tidal velocities are probably too low to re-suspend
bottom sediments, but suspended sediments will move in and out of Hilo Bay with the
tide.

The Hilo Bay watershed has one of the highest precipitation rates on the Hawaiian

Islands, ranging from 3 meters on the coast to 6 meters at the upper elevations annually
(Juvik & Juvik 1998). Hence, it is no surprise that the amount of freshwater entering
Hilo Bay is far greater than any other Hawaiian estuary. Surface waters are primarily
discharged into Hilo Bay from the Wailoa and Wailuku Rivers. Wailoa River is a
groundwater-fed flood-control channel that discharges into Waiakea Pond prior to
entering Hilo Bay. Waiakea Pond is the single largest source of groundwater into Hilo
Bay (M & E Pacific 1980). It is estimated that and 1.8 million cubic meters of
groundwater enters the Bay in this area (M & E Pacific 1980). The Wailuku River is the
largest perennial river in the state and the largest source of surface water to Hilo Bay.
The average flow of water from the Wailuku River into Hilo Bay is 1 million cubic
meters (range: 40 thousand -7 billion cubic meters; M & E Pacific 1980). Surprisingly,
little is known about the inputs of sediments and nutrients from these rivers. Currently,
HDOH, in collaboration with USGS, are quantifying storm inputs of sediments and
nutrients from Waiakea and Alenio gulches (both feed into Wailoa River) to Hilo Bay as
a part of HDOH total daily maximum load (TMDL) program. Inputs of sediments and
nutrients from the Wailuku River are currently being measured by UHH (Dr. Tracy
Wiegner, Marine Science) and US Department of Agriculture Forest Service (Dr. Richard
MacKenzie). Response of Hilo Bay to these inputs is unknown.

Much of the concern surrounding Hilo Bay?s water quality stems from the fact

that Hilo Bay?s waters are not clear. High-relief drainage and intense rainfall in Hilo
Bay?s watershed may contribute to naturally high sediment loads observed in the rivers
during storms. It is suspected that the Wailuku River delivers the majority of sediments
to Hilo Bay during storms and is the reason behind the poor water clarity in the Bay.

Wailoa

Wailuku

(�M

)

Figure 2. Comparison of average (�SD) nitrate concentrations in the Wailoa and
Wailuku Rivers, Hilo, HI over October 19, October 26, November 2, and November 9.
Data were collected by the MARE 350 class during Fall 2005 semester.

Preliminary data from UHH has found that turbidity is 10 times higher in Wailuku River
than Wailoa River during recent storms in October and November 2005 (Figure 1).
Currently, it is not known how long the Bay?s waters stay turbid following a storm and

whether these sediment
inputs impact the
ecosystem.

Another possible

factor contributing to the
low water clarity in Hilo
Bay are algal blooms.
Algal blooms result when
nutrients are prevalent and
their presence gives coastal
waters a greenish tint. As
previously mentioned, the
USEPA 303(d) impaired
listing for Hilo Bay for

excessive nutrients was based solely on visual assessment. From these assessments, it
was assumed that Hilo Bay had high nutrient concentrations because the water had ?a
greenish tint?, resulting from suspected algal blooms (Silvius et al. 2005). Actual
nutrient and chlorophyll a (chl a) data for
Hilo Bay are scarce. Preliminary data from
UHH indicates that nutrient concentrations
are five times greater in the Wailoa than the
Wailuku River (Figure 2), suggesting that
Wailoa may be the primary surface water
source of nutrients to Hilo Bay (MARE 350
unpublished data). The effect of these
nutrient inputs to Hilo Bay has not been
assessed to date.

The temporal scale over which the

few turbidity and nutrient samples were collected is inadequate to characterize the range
of conditions experienced in Hilo Bay. It is assumed that inputs of sediments and
nutrients to Hilo Bay are high during storms; however, these events have not been
historically targeted. Current research efforts by UHH, HDOH, and USGS are beginning
to quantify storm inputs of sediments and nutrients into Hilo Bay from the Wailuku
River, Alenio Gulch, and Waiakea Gulch. Information on how Hilo Bay responds to
storms over temporal and spatial scales is not known. Storm inputs of nutrients are
thought to stimulate algal blooms; however, no direct measurements have verified this.
Additionally, the importance of these algal blooms as a food source to higher trophic
levels, like commercially and recreationally important fish, is unknown.

Overall, the Hilo Bay Restoration Plan recommends (Silvius et al. 2005):
?

Identifying sources of sediments and nutrients to Hilo Bay from surface waters
under base and storm flow conditions

Oct 26

Nov 2

Nov 9

Date

Tur

i
d
it
y
(N

)

fall

(cm)

Wailoa
Wailuku

Figure 1. Comparison of average (�SD) turbidity values in the Wailoa and Wailuku Rivers in
Hilo, HI over different rainfall amounts. Rainfall data was obtained from
http://www.prh.noaa.gov/hnl/pages/hiclimate.php. Rainfall amounts were calculated using data
from two days prior to sampling. Turbidity data were collected during MARE 350 class during
Fall 2005 semester.

Collection of baseline chemical and ecological data to substantiate visual
assessment of nutrients (making direct measurements of nutrient and chl a
concentrations)

Examining the response of algae in Hilo Bay to base and storm flow conditions

?Scientific coordination to ensure that samples are continuously and constantly
gathered, without interruptions or changes in protocols, and with much better
spatial coverage than provided by? previous studies.

The study proposed below by UHH will begin to collect critical baseline data for Hilo

Bay that is: 1) essential for understanding how the Bay functions under baseflow and
storm conditions, 2) recommended by the Hilo Bay Restoration Plan, 3) needed to
develop a successful and cost effective restoration plan, and 4) required to evaluate
whether modification of the breakwater by ACOE will improve Hilo Bay water quality.

Proposed UHH Study

Experimental Design: This study will specifically examine how storms affect

water quality (sediments, nutrients, chl a) in Hilo Bay by comparing conditions in the
Bay before and following a storm event over a one-year period. A similar design has
been successfully used by Ringuet & Mackenzie (2005) to evaluate the effects of storms
on water quality and algae in Southern Kaneohe Bay, Oahu.

Site Description: For this project, eight stations will be sampled for sediments,

nutrients, and chl a (Figure 3). Two stations will be located in the freshwater portion of
the Wailoa and Wailuku Rivers. These stations will be used to determine the amount of
sediments and nutrients entering the Bay from surface waters. Four stations will be
located inside of Hilo Bay. Two Hilo Bay stations will be located along a transect
following the Wailoa River plume (Figure 3). The other two Hilo Bay stations will be
located along a transect following the Wailuku River plume (Figure 3). This transect will
be on a slight angle to the northwest of the river?s mouth because previous studies have
shown that the Wailuku River plume is deflected northwest in Hilo Bay (Dudley &
Hallacher 1991). Two control sites
will be located outside of the Hilo
Bay breakwater (Figure 3). Plumes
from either river should not affect
these control sites. Most of the
proposed stations have been previous
sampled by UHH through research
and class projects (data shown in
Figures 1 and 2).

Sampling Strategy: Water

samples from the river and bay
stations will be collected under base
and storm flow conditions during the
wet and dry season over a one-year
period. Each station will be sampled for suspended sediments, nutrients, and chl a for
five days during each season, under both base and storm flow conditions. This time
frame was selected based on previous findings from Kaneohe Bay, where algae bloomed

Wailuku River

Wailoa River

(

Control 1

Control 2

Proposed Sites

Control Sites

Estimated
Trajectory

(

Figure 3. Proposed sampling stations in Hilo Bay.

after three to five days following a storm (Ringuet & Mackenzie 2005). Because the
focus of this study is to evaluate water quality in Hilo Bay before and after a storm, water
samples will be collected from surface waters where river sediments and algae are most
likely concentrated due to the Bay?s stratification. For this study, storm conditions will
be defined as when Hilo receives more than 5 cm of rain in 24 hours. This rainfall
amount is based on current research Dr. Wiegner, who has found that 5 cm of rain
corresponds to a rise in the Wailuku River by 1 m, which is the average stage height for a
storm event based on historical USGS data. Rainfall data for Hilo Bay will be obtained
from a NOAA website (http://www.prh.noaa.gov/hln/pages/hiclimate.php). Following a
storm, all stations will be sampled for five consecutive days. Baseflow conditions will be
defined as when Hilo receives less than 5 cm of rain over a period of five days prior to
collection (Ringuet & Mackenzie 2005)

To estimate sediment and nutrient inputs to Hilo Bay from the Wailoa and

Wailuku Rivers, water samples will be collected at the two river stations during base and
storm flow conditions. For the Wailoa station, a depth integrated sampler will be used to
collect all samples. Stage height and discharge for the Wailoa River will be measured
using a staff gage and velocity meter, respectively. For the Wailuku River, a depth-
integrated sampler will be used to collect water under base flow conditions and an
automated storm sampler will be used to collect water during storms. A storm sampler
has been installed on the Wailuku River near the USGS gage for current UHH research.
Discharge for the Wailuku River will be calculated using stage height measured at the
USGS gaging station and stage height-discharge relationship previously established by
this agency. Concentration and discharge data will be used to calculate sediment and
nutrient fluxes from the Wailoa and Wailuku Rivers to Hilo Bay under base and storm
flow conditions.

Measurements: Parameters regulated by HDOH for estuarine water quality will

be targeted for this study (HDOH 2004). Nutrients [total nitrogen (TN), ammonium
(NH

), nitrate (NO

), total phosphorus (TP), phosphate (PO

), dissolved silicon

SiO

)], pH, turbidity, total suspended sediments (TSS), and chl a will be measured

during the wet and dry season under base and storm flow conditions. Additionally,
dissolved organic carbon (DOC) and particulate carbon (PC) will be measured at the
request of ACOE for their eutrophication model. NH

(USGS I-2525), NO

(USEPA

353.4), TP (USGS I-4650-03), PO

(USEPA 365.5), and H

SiO

(USEPA 366) will be

measured using standard autoanalyzer methods. TN and DOC will be measured on a
Shimadzu TOC-V CSH, TNM-1 following the recommendations by Sharp et al 2002.
Turbidity will be measured on a Hach 2100P Turbidimeter. TSS will be measured using
standard methods (APHA et al. 1995). PC will be

analyzed on a CHN analyzer (Costech

Analytical Technologies).

Chl a will be measured using USEPA method 445.0. To

characterize the conditions at each station when sampling, physiochemical parameters
(salinity, conductivity, temperature, dissolved oxygen concentration, dissolved oxygen
percent saturation, light penetration) will be measured using a YSI multi-parameter meter
and a Li-Cor light meter, respectively. At the request of ACOE, depth profiles for these
physiochemical parameters will be measured at the six Hilo Bay stations. Meteorological
data (rainfall, winds, waves, and tides) will also be obtained for the sampling dates.

Projected Outcomes: This project will bring together researchers from UHH and ACOE
to help Hawai`i County decide on appropriate remediation actions to improve water
quality in Hilo Bay. Specifically, essential baseline water quality data for Hilo Bay will
be collected to complement circulation data being collected by ACOE. This information
will allow for a greater understanding of how Hilo Bay functions. With this
understanding, appropriate restoration actions can be developed and implemented to
improve Hilo Bay water quality.

This project will also provide a mechanism for involving the local community in

the Hilo Bay ahupua?a. This project will train undergraduate and Master?s students at
UHH. Additionally, this project will support the new analytical facility at the UHH built
with National Science Foundation funds to expand the University?s research capacity.

Results from this research will be made available to a wide audience. Scientists

will be targeted through peer-reviewed articles in scientific journals and presentations at
local and international scientific meetings. Our results will also be made available to
managers and the general public through presentations at local watershed advisory
meetings.

Projected Deliverables: The following deliverables will be provided by UHH to the
Honolulu District of the U.S. Army Corps of Engineers (USACE):
1. Nutrient sample data in formats compatible with input to the proposed USACE water
quality numerical models.
2. Draft and final report documenting nutrient sample collection, meteorological data for
the sample collection periods (to include at a minimum rainfall, winds, waves and tides),
description of sample concentration trends for each collection period, and
summary/conclusion of sampling results.
3. Final deliverables will be provided to Honolulu District personnel within 12 months
from the date of the notice to proceed.

Budget Justification: Funds are requested for 1 month of summer salary plus fringe
(June 2006 & June 2007) for Dr. Tracy Wiegner. The anticipated salary increases have
been taken into account in the budget (5% increase as of July 2005). Dr. Wiegner will be
the P.I. on this project, overseeing its overall design, sample collection and processing,
data analysis, and final presentation in written reports/manuscripts and presentations at
local and international meetings. She will collaborate with ACOE and mentor both
Masters and undergraduate students on this project. Her UHH appointment is 9 months
and does not cover salary during the summer. Funds are also requested to support one
graduate-level student research assistant in the Tropical Conservation Biology and
Environmental Science Program at UHH. Graduate-level student research assistants are
funded to work 20 hrs per week with benefits (30%). Support is also requested for an
undergraduate-level student research assistant (10 days/season; 12hours/day) at an hourly
wage of $8.85 (A3-1 level) and fringe rate of 12%. It is estimated that 1920 nutrient
samples (triplicate samples; comparable sampling scheme for proposed Hawaii Sea Grant
project on similar topic) will be generated at a cost of $3.00 to $10.00 per sample (UHH
Analytical Laboratory fees for UHH faculty). Funds for supplies are estimated at $7005
for the entire project. During the project, supply monies will be used to purchase YSI
and velocity meters, as well as a freezer to store samples. To collect samples in Hilo
Bay, a boat is needed. UHH Marine Science Department has a 20? aluminum Larson
outboard skiff at the cost of $125/day. It is estimated that $3,400 will be needed to cover
the boat fees. Travel back and forth from UHH Marine Science Department to the
Wailoa River Boat Ramp is approximately 5 miles. UHH Marine Science Department
charges $0.50/mile to use their vehicles. Funds are requested to cover overhead at a rate
of 3.5% of ?modified? direct costs.

Budget

Cost

Personnel

P.I. summer salary (1 month; June 2006)

$5,065

P.I. summer salary (1 month; June 2007)

$5,318

Fringe (2.6%; June 2006 & 2007)

$270

Research Assistant salary (graduate-level)

$17,000

Fringe

(30%)

$5,100

Research Assistant (undergraduate-level)

$2,124

Fringe

(12%)

$255

Laboratory Fess
Nutrient

Analysis

$18,240

Field Equipment & Supplies

Supplies

$7,005

Boat Fee

$2,500

Vehicle

Fee

$100

Boat Rental Fee for ACOE (6 days)

$900

University

Overhead

(3.5%)

$2,236

Total

$66,113

References:
APHA, AWWA, and WEF. 1995. Total solids dried at 103-105 C. In: Eaton, A.D.,

L.S., Clesceri, and A.E. Greenberg (eds.), Standard Methods for the Examination
of Water and Water Water, 19

edition. American Public Health Association,

Washington, D.C.

Dudley, W.C. Jr and L. E. Hallacher. 1991. Distribution and dispersion of sewerage

pollution in Hilo Bay and contiguous waters. Final report. County of Hawai`i
Department of Public Works.

HDOH. 2000. Hawai`i?s implementation plan for polluted runoff control.
HDOH. 2004. Amendment and compilation of chapter 11-54. Hawai`i administrative

rules. http://www.Hawai`i.gov/health/about/rules/11-54.pdf

Hawai`i Island Journal. 2004. What?s wrong with Hilo Bay?
Juvik, J, and S. Juvik. 1998. Atlas of Hawai`i. Department of Geography. University of

Hawai`i Press. Hilo, Hawai`i.

Koch, L., J. Harrigan-Lum, and K. Henderson. 2004. 2004 List of impaired waters in

Hawai`i prepared under Clean Water Act Section 303(d). HDOH Environmental
Planning Office.

M & E Pacific. 1980 Hilo area comprehensive study?Geological, biological and water

quality investigations of Hilo Bay. US ACOE, Honolulu District.

Ringuet, S. and F. T. Mackenzie. 2005. Controls on nutrient and phytoplankton dynamics

during normal flow and storm runoff conditions, southern Kaneohe Bay, Hawai`i.
Estuaries 28(3): 327-337.

Sharp, S.H., et al. 2002. A preliminary method comparison for measurement of dissolved

organic nitrogen in seawater. Marine Chemistry 78: 171-184.

Silvius, K., P. Moravcik, and M. James. 2005. Hilo Bay watershed-based restoration

plan. Submitted to HDOH, Polluted Runoff Control.

USEPA. 2002. National health protection survey of beaches-2001 swimming season.

http://yosemite.epa.gov/water/beach2002.nsf