Section 319
NONPOINT SOORCE PROGRAM SUCCESS STORY
Eradication of Invasive Species Restores Lake Water Quality
WatPfbodv ImnroVPd The dan9er of toxins from blooms of blue-green algae led offi-
y ^ cials to sometimes close Diamond Lake for contact use recre-
ation. As a result, Oregon Department of Environmental Quality (ODEQ) included Diamond Lake
on the 1998 303(d) list of impaired waters for pH and algae. Excess algae resulted from a shift
in the trophic levels after the introduction of tui chub, a nonnative fish species. After careful
planning, project partners successfully eradicated the fish in the fall of 2006, and water qual-
ity conditions improved dramatically. Currently, all water quality standards are being met and
ODEQ expects to remove Diamond Lake from the list in the next assessment cycle in 2010.
Problem
Diamond Lake is situated between two volcanic
peaks in the southern Oregon Cascade Mountains
in the Umpqua National Forest (Figure 1). Perched
at 1,580 meters, or about 1 mile elevation, Diamond
Lake developed into a world-renowned trout fishery
after Oregon Fish and Game officials began stock-
ing it with rainbow trout in 1910.
Oregon first added Diamond Lake to its 303(d) list
of impaired waters in 1998 due to high pH and chlo-
rophyll a values found during the summer when the
lake experienced excessive algal blooms. In 2004 it
was also listed for low dissolved oxygen and high
pH values during the fall, winter and spring. Algae
blooms resulted from a shift in trophic levels due
to the introduction of tui chub, a nonnative species
offish used as live bait by recreational fishermen.
The tui chub overtook the lake's ecosystem and
consumed many of the small aquatic organisms
that normally control algae growth. Toxic blue-green
algae proliferated, which caused the lake to fail to
support its designated uses of aesthetics, fishing
and water contact recreation.
ODEQ developed the Umpqua Basin Total
Maximum Daily Load (TMDL) in 2006. TheTMDL
determined that biomass limitation through the
eradication of the tui chub would improve water
quality and restore the lake's beneficial uses.
Bathymetry
Project Highlights
Thorough planning efforts led to a well-coordinated
drawdown of the lake in September 2006 and
subsequent treatment with rotenone to remove the
Figure 1. Depth
contours of
Diamond Lake
in the Umpqua
National Forest.
tui chub. Rotenone is a naturally occurring chemi-
cal derived from the roots of several tropical and
subtropical plant species. Routinely used to control
unwanted fish species, rotenone is rapidly broken
down in soil and water and usually loses toxicity
within six days. The lake drawdown reduced the
quantity of water to be treated and maximized the
mechanical removal of tui chub biomass before
rotenone application. Pretreatment netting removed
68,000 pounds of tui chub. Mechanical and hand
removal of the dead chub after rotenone treatment
recovered an additional 35,000 pounds of tui chub
carcasses. All chub were composted and later used
as a nutrient supplement for farming operations.
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Results
Diamond Lake met all water quality standards not
long after chub removal. In late 2007, chlorophyll
a values decreased from a high of 50/jg/L before
rotenone treatment to less than 10/jg/L (the water
quality criterion) after treatment (Figure 2). Algal
production is being held in check by the reestab-
lished zooplankton populations. Midsummer water
Figure 2. Reduction
in algal blooms, as
represented by chlo-
rophyll a, before and
after chub removal.
Figure 3. Transparency
depths with and
without tui chub
shows the Secchi
disk readings at the
height of the tui chub
population in 2006
and extreme clarity in
the summer of 2007.
Figure 4. Observed
overall decrease in pH
after eradication of
tui chub. Excursions
over the pH criteria
in 2007 are natural
and can occur during
extended periods
of above-average
air temperature and
below-average wind
velocities.
Feb
Oct
Apr May Jun Jut Aug Sep Oct Mov
7
Apr May Jun
Quality
^ Standard
Aug Sep Oct Nov Dec
clarity increased from an average of 10 feet to
nearly 50 feet, the lake's depth at its deepest point
(Figure 3), and blue-green algae declined from the
dominant type of algae to a very small percent-
age of the algal community. The lake remained
cooler in 2007, which can be attributed to reduced
algal populations in the upper layers that absorb
solar energy. After the spring of 2007, scientists
observed that pH values recovered to below or near
the 8.5 criteria value (Figure 4). Zooplankton popula-
tions have rebounded and trout restocking led to
increased angler catches in 2007.
Water quality improvements have restored the
aquatic life designated use. On the basis of the
data, ODEQ expects this waterbody to continue
to meet standards in the future, warranting the
delisting from the 2010 303(d) list of impaired
waterbodies.
Partners and Funding
The project co-leaders included Umpqua National
Forest and Oregon Department of Fish and Wildlife.
ODEQ led water quality efforts, while many private
and public entities played supporting roles. State
Representative Susan Morgan brought together a
wide range of responsible and interested parties
focused on solving the deteriorating Diamond Lake
water quality conditions. Additional partners include
Partners for Umpqua Watersheds, Oregon Wildlife
Heritage Foundation, Oregon Division of State
Lands, Oregon Department of Agriculture, Douglas
County, PacifiCorp, and several other state and
federal agencies.
Clean Water Act section 319 funds helped support
several phases of the project, including database
development, baseline monitoring fortheTMDL
assessment and analyses of water quality following
lake drawdown and rotenone application. In total,
this project used $166,338 of section 319 funds,
including the state match. Diamond Lake's restored
waters generate $3.5 million annually for the state
and local economies.
To keep Diamond Lake sparkling, Oregon
Department of Fish and Wildlife, Oregon State
Marine Board, Umpqua National Forest, and ODEQ
have launched an intensive invasive species preven-
tion campaign. The partners are communicating
the following message: "Spread the word...not the
unwanted species."
I
U.S. Environmental Protection Agency
Office of Water
Washington, DC
EPA841-F-08-001E
May 2008
For additional information contact:
Paul Heberling, Umpqua Basin Team Coordinator
541-687-7428
heberling.paul@deq.state.or.us
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