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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