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Implementation Improves Water Quality in Lake Shaokatan
Waterbody Improvsd Within an agricultural watershed in southwestern Minnesota,
the 995-acre Lake Shaokatan experienced extensive algal blooms
from excessive nutrient and sediment runoff. The Minnesota Pollution Control Agency (MPCA)
officially placed the lake on the Clean Water Act (CWA) section 303(d) impaired waters list in
2002 for failing to meet its aquatic recreation and life use designations. Local partners conducted
implementation activities in the watershed such as tile inlet removal, septic system upgrades, and
upland best management practices (BMPs); these led to lasting reductions in phosphorous levels
and a corresponding reduction in nuisance algae. As a result of more than 20 years of restoration
implementation activities, recent monitoring data showed that Lake Shaokatan met water quality
standards (WQS) and was removed from the CWA section 303(d) list in 2018.
Problem
Located near the town of Ivanhoe, In Minnesota's
Lincoln County, Lake Shaokatan has a watershed-to-
lake ratio of 9:1 and covers 13.9 square miles (Figure
1). The primary land use is agricultural, including
about 12 percent pasture/rangeland and 43 percent
cropland). Excessive nutrient and sediment runoff
from cropland, manure application, animai feedlots,
pastureland, livestock access, failing septic systems,
and developed shorelines likely led to extensive aigae
biooms in the lake. The shallow lake (maximum depth
of 10 feet) has a history of water quality problems,
including severe nuisance blue-green algai blooms,
low-oxygen ievels in summer and winter, and periodic
fish kills.
Local partners received a Phase I grant in April 1991
through the MPCA's Clean Water Partnership (CWP)
program to complete a diagnostic study and imple-
mentation plan to determine the cause and sources of
pollution to Lake Shaokatan. Restoration efforts began
in March 1993 and included rehabilitating three animal
feedlots, four wetland areas, and several failing septic
systems. These efforts resulted in a 58 percent reduc-
tion in phosphorus loading into the lake. By 1994,
phosphorus levels in the lake dropped significantly,
with concentrations near the state WQS of 90 parts
per billion (ppb), down from 200-350 ppb in previous
summers. This decrease resulted in reductions in the
frequency and severity of nuisance algal blooms. Plant
surveys in 2000 and 2002 found essentially no rooted
plants. In addi tion, water monitoring data collected
in 1999-2001 showed that levels of phosphorus and
Figure 1. The Lake Shaokatan watershed is used primarily
for agriculture.
chlorophyll-o exceeded WQS. These increases were
largely attributed to a major runoff event from an
abandoned feediot in the shoreland area of the iake.
Project Highlights
In 2004 a total maximum daily load (TMDL) project
began that identified sources of phosphorus and addi-
tional implementation activities to meet WQS. During
the time of the TMDL project, local partners continued
to advance ongoing implementation activities in the
watershed such as tile inlet removal, septic system
upgrades, and upland BMPs.
The improvements made to Lake Shaokatan can-
not be limited to a single effort, but rather a suite of
Legend
• Feedlots
¦¦ Open Water
¦[ Developed
Forest/Shrub
¦i Rangeland
I I Cropland
CD Wetland

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Figure 2. Lake Shaokatan now boasts clear shallows
and a grassy lakeshore.
BMPs installed in the lake's watershed. To target the
livestock manure entering the lake, partners worked
with producers to update feedlots, relocate and/or
retire feedlots, and manage the animal waste runoff.
Additionally, open tile intakes were replaced with
alternative intakes or removed to reduce the amount
of polluted surface water entering the tile system and
getting into the lake. Partners completed several wet-
land restorations, adopted conservation easements,
and re-routed tile lines. A pasture fence was installed
along the shoreline to keep cattle out of the lake.
Many existing failing septic systems were upgraded for
residents within the watershed, including Picnic Point
County Park, the Lighthouse Supper Club, and a private
campground. Several seasonal trailer homes along
the lake shore that were not in compliance with local
ordinance were removed.
Results
Typical of many shallow lakes in agricultural water-
sheds, Lake Shaokatan's condition shows that long-
term efforts can make a difference (Figure 2). Recent
monitoring of Lake Shaokatan has shown phosphorus
concentrations in 2013 and 2014 registered some
all-time lows for the lake (Figure 3). Data in 2014 show
that the lake met the phosphorus WQS of 90 ppb.
These decreases resulted In less frequent algal blooms.
In both 2013 and 2014, water clarity averaged 5.6 feet
(1.7 meters). In 2014, chlorophyll-o remained below
30 ppb (a level that Indicates nuisance blooms) all sum-
mer and averaged 9 ppb — a stark contrast to typical
summer-means of 60 to 70 ppb.
In 2014, the composition of algae shifted to include
diatoms and other forms indicating cleaner water.
Figure 3. Lake Shaokatan summer mean total
phosphorus (TP) levels have declined.
Rooted plants were evident across the lake in 2014 to
present, according to observations by MPCA staff, a
Minnesota Department of Natural Resources (DNR)
aquatic plant survey, and shoreline property owners.
Because Lake Shaokatan met WQS for phosphorus
and chlorophyll-o based on recent years of monitor-
ing data, MPCA removed the lake from the 303(d)
impaired waters list in 2018.
Partners and Funding
Many local, state, and federal stakeholders have
come together to achieve the necessary sustained
reduction in phosphorus loading to achieve lasting
improvements in the lake's overall health. Partners
include area landowners, Lake Shaokatan Association,
Lake Shaokatan Sportsman's Club, Lincoln County
Environmental Office, Lincoln County Soil and Water
Conservation District (SWCD), Yellow Medicine River
Watershed District (YMRWD), Minnesota Board of
Water and Soil Resources, MDNR, MPCA, U.S. Fish and
Wildlife Service, and the U.S. Environmental Protection
Agency.
Lake Shaokatan restoration efforts have been sup-
ported by a total of $994,000 from local landowners
($119,900) and other local match ($100,000), Lincoln
SWCD ($240,000), and MPCA ($382,000). Specific
funding sources include a numerous state CWP
grants (1991: $47,791 plus $47,791 YMRWD match;
1993: $239,645 pius $239,654 YMRWD match; 2000:
$50,000 plus $110,000 Lincoln County match; 2004:
$45,000 plus $82,404 local match). Other sources
include a 2004 CWA section 319 grant for TMDL devel-
opment ($62,804) and a local match ($1,603).
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U.S. Environmental Protection Agency
Office of Water
Washington, DC
EPA 841-F-18-Q01KK
November 2018
For additional information contact:
Mark Hanson
Minnesota Pollution Control Agency
507-476-4259 • Mark.Hanson@state.mn.us
Mike Weckwerth
Minnesota Pollution Control Agency
507-476-4267 • Michael.Weckwerth@state.mn. us

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