Watershed Achievements Report

a Success Story . . .
Lake Shaokatan: A prairie lake with improving water quality
Section 319 and Clean Water Partnership grants along with
Clean Water Legacy funds were used to help improve water
quality in Lake Shaokatan in southwestern Minnesota by
addressing feedlot runoff, farming and urban sources of
pollutants, and failing septic systems.
Plagued by toxic blue-green algal blooms for several
years, the lake is now recording all-time lows of
phosphorus (P), the nutrient that causes algae, and
showing other signs of improvement.
Typical of many shallow lakes in agricultural watersheds,
Lake Shaokatan’s condition shows that long-term efforts
can make a difference. This 995-acre lake near the town
of Ivanhoe in Lincoln County has a maximum depth of
ten feet. Excessive nutrient runoff from neighboring farm
fields and developed shorelines likely led to extensive
algae blooms in the lake. The lake has a history of water
quality problems including severe nuisance blue-green
blooms, low oxygen levels in summer and winter, and
periodic fish kills.
Lake Shaokatan was part of a Clean Water Partnership
effort, sponsored by the Yellow Medicine Watershed
District, involving the MPCA, state and federal agencies,
local groups, and local units of government. A detailed
diagnostic study started in 1991 and restoration efforts
were underway by 1993.
These efforts included rehabilitation of three animal
feedlots, four wetland areas, and shoreline septic systems.
The result was a 58% reduction in P loading into the lake.
By 1994, P levels in the lake had dropped significantly.
This decrease resulted in reductions in the frequency and
severity of nuisance algal blooms. In addition, water clarity
increased and residents reported that rooted plants –
instead of algal plants – were increasing.
The MPCA officially listed the lake as impaired in 2002,
requiring a Total Maximum Daily Load (TMDL) study to
determine the maximum amount of nutrients the lake can
accept and still meet standards. That study led to further
restoration efforts that are now paying off.
The level of P in Lake Shaokatan has dropped significantly
in recent years, with the blue lines indicating the summer
means and the red line showing the water quality standard
of 90 parts per billion (ppb) maximum. Additional sampling
in future years will show if Lake Shaokatan can be delisted
as an impaired water.
TP ppb
450
400
350
300
250
200
150
100
50
0
Annual Total Phosphorus in Lake Shaokatan
1989 – 2014
Making a difference: Local
watershed partners
From an article in the online journal Water Laws
Terry Renken served on the Board of Managers of the
Yellow Medicine River Watershed District. His involvement
with the Lake Shaokatan project began when he was
designated by the Yellow Medicine River Watershed District
as the watershed district’s project representative.
Terry’s ultimate satisfaction with the completion of the
project has been in watching the public’s excitement about
Lake Shaokatan’s improvements.
“Lake lots are now developing at a rapid pace. Economic
values have increased, as well as the lake’s increased
recreational value. The Picnic Point County Park rests along
the south shore, offering campsites, a new playground, and
a newly created beach. A supper club has reopened on the
north shore.”
According to Terry, “through the Lake Shaokatan Project,
new knowledge was gained. As a result, the Yellow
Medicine River Watershed District has grown, redeveloping
and extending its interests, broadening our horizons.”
Minnesota Pollution Control Agency www.pca.state.mn.us 3