Placid Lake
18-0076-00 CROW WING COUNTY
Lake Water Quality
Summary
Placid Lake is located 5 miles south of Deerwood, MN in Crow Wing
County. It is a long lake covering 185 acres (Table 1).
Placid Lake has no inlets or outlets, which classify it as a groundwater
seepage lake. Lakes without outlets can experience swings in water
levels due to precipitation.
Water quality data have been collected on Placid Lake from 2000-2014
(Tables 2 & 3). These data show that the lake is mesotrophic (TSI = 42)
with clear water conditions most of the summer and excellent
recreational opportunities.
Placid Lake has an organized association that is involved in activities
such as water quality monitoring and education.
Table 1. Placid Lake location and key physical characteristics.
Location Data
MN Lake ID:
Physical Characteristics
18-0076-00
Surface area (acres):
185.6
County:
Crow Wing
Littoral area (acres):
33.5
Ecoregion:
Northern Lakes and Forests
% Littoral area:
18.1
Major Drainage Basin:
Mississippi R. – Brainerd
Max depth (ft), (m):
21.0, 6.4
Latitude/Longitude:
46.42589/-93.881949
Inlets:
0
Invasive Species:
None (as of 2014)
Outlets:
0
Public Accesses:
1
Table 2. Availability of primary data types for Placid Lake.
Data Availability
Transparency data
Excellent data set from 2000-2014.
Chemical data
Good data set from 2001-2003, but not enough for trend
analysis.
Recommendations
For recommendations refer to page 18.
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Lake Map
Figure 1. Map of Placid Lake with 2010 aerial imagery and sample site locations, inlets and outlets, and public
access points.
Table 3. Monitoring programs and associated monitoring sites. Monitoring programs include the Citizen Lake
Monitoring Program (CLMP), Minnesota Pollution Control Agency (MPCA), Outdoor Corps (OC).
Lake Site
201
Depth (ft)
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Monitoring Programs
CLMP: 2000-2014; MPCA: 1982; OC: 2001-2003
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Average Water Quality Statistics
The information below describes available chemical data for Placid Lake through 2014 (Table 4).
Data for total phosphorus, chlorophyll a, and Secchi depth are from the primary site 201.
Minnesota is divided into 7 ecoregions based on land use, vegetation, precipitation and geology.
The MPCA has developed a way to determine the "average range" of water quality expected for
lakes in each ecoregion. For more information on ecoregions and expected water quality ranges,
see page 11. Placid Lake is in the Northern Lakes and Forests Ecoregion.
Table 4. Water quality means compared to ecoregion ranges and impaired waters standard.
Ecoregion
Range1
14 – 27
4 – 10
< 15
8 – 15
Impaired
Waters
Standard2
> 30
>9
Parameter
Total phosphorus (ug/L)
3
Chlorophyll a (ug/L)
Chlorophyll a max (ug/L)
Secchi depth (ft)
Dissolved oxygen
Mean
16.9
4.2
14.0
15.8
Total Kjeldahl Nitrogen
NA
<0.4 – 0.75
Dissolved oxygen depth profiles
show that the lake mixes
periodically in summer.
No data available.
Alkalinity (mg/L)
NA
40 – 140
No data available.
Color (Pt-Co Units)
NA
10 – 35
No data available.
pH
8.0
7.2 – 8.3
Chloride (mg/L)
NA
0.6 – 1.2
Within the expected range for
the ecoregion. Lake water pH
less than 6.5 can affect fish
spawning and the solubility of
metals in the water.
No data available.
Total Suspended
Solids (mg/L)
Conductivity (umhos/cm)
NA
<1 – 2
No data available.
51.0
50 – 250
TN:TP Ratio
NA
25:1 - 35:1
Within the expected range for
the ecoregion.
No nitrogen data available.
See page 8
Interpretation
Results are within the expected
range for the Northern Lakes
and Forests Ecoregion.
< 6.5
(mg/L)
1
th
th
The ecoregion range is the 25 -75 percentile of summer means from ecoregion reference lakes
For further information regarding the Impaired Waters Assessment program, refer to http://www.pca.state.mn.us/water/tmdl/index.html
3
Chlorophyll a measurements have been corrected for pheophytin
Units: 1 mg/L (ppm) = 1,000 ug/L (ppb)
2
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Water Quality Characteristics - Historical Means and Ranges
Table 5. Water quality means and ranges for primary sites.
Total Phosphorus Mean (ug/L):
Primary
Site
201
16.9
Total Phosphorus Min:
Total Phosphorus Max:
Number of Observations:
5.0
21.0
14
Parameters
Chlorophyll a Mean (ug/L):
4.2
Chlorophyll-a Min:
Chlorophyll-a Max:
Number of Observations:
1.0
14.0
14
Secchi Depth Mean (ft):
15.8
Secchi Depth Min:
Secchi Depth Max:
Number of Observations:
5.5
27.0
158
Figure
2. Lake
“insert”
phosphorus,
chlorophyll
a and
transparency
historical
ranges.
arrow
Figure
2. Placid
Lake
totaltotal
phosphorus,
chlorophyll
a and
transparency
historical
ranges.
The The
arrow
represents
the
range
and
the
black
dot
represents
the
historical
mean
(Primary
Site
xxx).
Figure
adapted
represents the range and the black dot represents the historical mean (Primary Site 201). Figure adapted
after Moore and Thornton, [Ed.]. 1988. Lake and Reservoir Restoration Guidance Manual. (Doc. No. EPA 440/5-88-002)
after Moore and Thornton, [Ed.]. 1988. Lake and Reservoir Restoration Guidance Manual. (Doc. No. EPA 440/5-88-002)
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Transparency (Secchi Depth)
Transparency is how easily light can pass through a substance. In lakes it is how deep sunlight
penetrates through the water. Plants and algae need sunlight to grow, so they are only able to
grow in areas of lakes where the sun penetrates. Water transparency depends on the amount of
particles in the water. An increase in particulates results in a decrease in transparency. The
transparency varies year to year due to changes in weather, precipitation, lake use, flooding,
temperature, lake levels, etc.
The annual mean transparency in Placid Lake ranges from 11.4 to 18.2 feet (Figure 3). The
annual means hover fairly close to the long-term mean. For trend analysis, see page 10.
Transparency monitoring should be continued annually at site 201 in order to track water quality
changes.
18
90
16
80
70
14
12
Secchi Depth (ft)
100
10
Precipitation
60
Secchi
50
Mean
8
40
6
30
4
20
2
10
0
0
Precipitation (in)
Transparency and Precipitation
20
Date
Figure 3. Annual mean transparency compared to long-term mean transparency.
Placid Lake transparency ranges from 5.5 to 27.0 ft at the primary site (201). Figure 4 shows the
seasonal transparency dynamics. The maximum Secchi reading is usually obtained in early
summer. Placid Lake transparency is high in May and June, and then declines through August.
This transparency dynamic is typical of a Minnesota lake. The dynamics have to do with algae and
zooplankton population dynamics, and lake turnover.
It is important for lake residents to understand the seasonal transparency dynamics in their lake so
that they are not worried about why their transparency is lower in August than it is in June. It is
typical for a lake to vary in transparency throughout the summer.
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Seasonal Transparency Dynamics
30
1982
2000
2001
25
Secchi Depth (ft)
2002
2003
20
2004
2005
15
2006
2007
10
2008
2009
5
2010
2011
0
2012
Figure 4. Seasonal transparency dynamics and year to year comparison (Primary Site 201). The black line
represents the pattern in the data.
User Perceptions
When volunteers collect Secchi depth readings, they record their perceptions of the water based
on the physical appearance and the recreational suitability. These perceptions can be compared
to water quality parameters to see how the lake "user" would experience the lake at that time.
Looking at transparency data, as the Secchi depth decreases the perception of the lake's physical
appearance rating decreases. Placid Lake was rated as being "not quite crystal clear" 59% of the
time by samplers at site 201 between 2000 and 2014 (Figure 5).
Physical Appearance Rating
6%
35%
59%
35%
Crystal clear water
59%
Not quite crystal clear – a little algae visible
6%
Definite algae – green, yellow, or brown color
apparent
0%
High algae levels with limited clarity and/or mild
odor apparent
0%
Severely high algae levels
Figure 5. Placid Lake physical appearance ratings by samplers.
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As the Secchi depth decreases, the perception of recreational suitability of the lake decreases.
Placid Lake was rated as being "beautiful" 70% of the time from 2000 to 2014 (Figure 6).
Recreational Suitability Rating
4% 2%
24%
70%
Beautiful, could not be better
24%
Very minor aesthetic problems; excellent for
swimming, boating
4%
Swimming and aesthetic enjoyment of the lake
slightly impaired because of algae levels
2%
Desire to swim and level of enjoyment of the lake
substantially reduced because of algae levels
0%
Swimming and aesthetic enjoyment of the lake
nearly impossible because of algae levels
70%
Figure 6. Recreational suitability rating, as rated by the volunteer monitor.
Total Phosphorus
Placid Lake is phosphorus
limited, which means that
algae and aquatic plant
growth is dependent upon
available phosphorus.
Eutrophic
25
Total Phosphorus (ug/L)
Total phosphorus was
evaluated in Placid Lake in
2001-2003. The data do
not indicate much
seasonal variability. The
majority of the data points
fall into the
mesotrophic/oligotrophic
border (Figure 7).
Total Phosphorus
30
20
Mesotrophic
2001
15
2002
2003
10
5
Oligotrophic
Phosphorus should
continue to be monitored
to track any future
changes in water quality.
0
Figure 7. Historical total phosphorus concentrations (ug/L) for Placid Lake site 202.
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Chlorophyll a
Chlorophyll a is the
pigment that makes
plants and algae
green. Chlorophyll a is
tested in lakes to
determine the algae
concentration or how
"green" the water is.
Chlorophyll a
12
Chlorophyll a (ul/L)
10
Chlorophyll a
concentrations greater
than 10 ug/L are
perceived as a mild
algae bloom, while
concentrations greater
than 20 ug/L are
perceived as a
nuisance.
1982
8
2001
6
2002
2003
4
Minor Algae
2
0
Figure 8. Chlorophyll a concentrations (ug/L) for Placid Lake at site 202.
Chlorophyll a was
evaluated in Placid Lake in 1982, 2001-2003 (Figure 8). Chlorophyll a concentrations were below
10 ug/L in all three years, indicating clear water. There was not much variation over the years
monitored and chlorophyll a concentrations remained relatively steady over the summer.
Dissolved Oxygen
Dissolved Oxygen (mg/L)
0
2
4
6
8
10
12
0
1
2
Depth (m)
3
4
5
Dissolved Oxygen (DO) is the amount of oxygen dissolved in
lake water. Oxygen is necessary for all living organisms to
survive except for some bacteria. Living organisms breathe in
oxygen that is dissolved in the water. Dissolved oxygen
levels of <5 mg/L are typically avoided by game fisheries.
Placid Lake is a relatively shallow lake, with a maximum depth
of 21 feet. Dissolved oxygen profiles from data collected in
2003 show periodic stratification developing mid-summer
(Figure 9). In a shallow lake, the water column never
completely stratifies. Any windy day can mix up the water
column causing phosphorus from the anoxic lake bottom to
re-suspend into the water. This phenomenon is known as
internal loading.
6
7
8
9
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Figure 9. Dissolved oxygen profile for Placid Lake.
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Trophic State Index (TSI)
TSI is a standard measure or means for calculating the
trophic status or productivity of a lake. More specifically,
it is the total weight of living algae (algae biomass) in a
waterbody at a specific location and time. Three
variables, chlorophyll a, Secchi depth, and total
phosphorus, independently estimate algal biomass.
Table 6. Trophic State Index for Placid.
Phosphorus (nutrients), chlorophyll a (algae
concentration) and Secchi depth (transparency) are
related. As phosphorus increases, there is more food
available for algae, resulting in increased algal
concentrations. When algal concentrations increase,
the water becomes less transparent and the Secchi
depth decreases. If all three TSI numbers are within a
few points of each other, they are strongly related. If
they are different, there are other dynamics influencing
the lake’s productivity, and TSI mean should not be
reported for the lake.
Trophic State Index Site 201
TSI Total Phosphorus 45
TSI Chlorophyll-a
45
TSI Secchi
37
TSI Mean
42
Mesotrophic
Trophic State:
Numbers represent the mean TSI for each
parameter.
100
Hypereutrophic
70
Eutrophic
50
The mean TSI for Placid Lake falls into
Placid Lake
the mesotrophic range (Figure 10).
There is good agreement between the
TSI for phosphorus, chlorophyll a,
indicating that these variables are strongly related
(Table 6). The TSI for transparency is lower, but it
could be because there many more years of
transparency data than phosphorus and chlorophyll a
data.
Mesotrophic
40
Oligotrophic
0
Mesotrophic lakes (TSI 50-70) are characterized by
Figure 10. Trophic state index chart
moderately clear water most of the summer. "Meso"
with corresponding trophic status.
means middle or mid; therefore, mesotrophic means a
medium amount of productivity. Mesotrophic lakes are commonly found in central Minnesota and
have clear water with algal blooms in late summer (Table 7).
Table 7. Trophic state index attributes and their corresponding fisheries and recreation characteristics.
TSI
Attributes
Fisheries & Recreation
<30
Oligotrophy: Clear water, oxygen throughout
Trout fisheries dominate
the year at the bottom of the lake, very deep
cold water.
30-40
Bottom of shallower lakes may become anoxic
Trout fisheries in deep lakes only. Walleye,
(no oxygen).
Cisco present.
40-50
Mesotrophy: Water moderately clear most of
No oxygen at the bottom of the lake results in
the summer. May be "greener" in late summer.
loss of trout. Walleye may predominate.
50-60
Eutrophy: Algae and aquatic plant problems
Warm-water fisheries only. Bass may
possible. "Green" water most of the year.
dominate.
60-70
Blue-green algae dominate, algal scums and
Dense algae and aquatic plants. Low water
aquatic plant problems.
clarity may discourage swimming and boating.
70-80
Hypereutrophy: Dense algae and aquatic
Water is not suitable for recreation.
plants.
>80
Algal scums, few aquatic plants
Rough fish (carp) dominate; summer fish kills
possible
Source: Carlson, R.E. 1997. A trophic state index for lakes. Limnology and Oceanography. 22:361-369.
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Trend Analysis
For detecting trends, a minimum of 8-10 years of data with 4 or more readings per season are
recommended. Minimum confidence accepted by the MPCA is 90%. This means that there is a
90% chance that the data are showing a true trend and a 10% chance that the trend is a random
result of the data. Only short-term trends can be determined with just a few years of data, because
there can be different wet years and dry years, water levels, weather, etc, that affect the water
quality naturally.
Placid Lake had enough data to perform a trend analysis on transparency (Table 8). The data was
analyzed using the Mann Kendall Trend Analysis.
Table 8. Trend analysis for site 202.
Lake Site
Parameter
201
Total Phosphorus
201
Chlorophyll a
201
Transparency
Date Range
2001-2003
2001-2003
2000-2014
Trend
Insufficient data
Insufficient data
No trend
Transparency Trend for Placid Lake
30
Secchi Depth (ft)
25
20
15
10
5
06/30/2000
08/03/2000
09/21/2000
06/22/2001
07/25/2001
09/05/2001
05/26/2002
06/28/2002
07/26/2002
09/16/2002
07/02/2003
08/12/2003
05/28/2004
07/20/2004
10/06/2004
08/01/2005
05/26/2006
07/25/2006
06/19/2007
08/02/2007
06/23/2008
08/06/2008
06/09/2009
08/28/2009
07/05/2010
09/01/2010
06/24/2011
08/14/2011
07/14/2012
09/21/2012
07/29/2013
5/28/2014
9/4/2014
0
Figure 11. Transparency (feet) trend for site 202 from 2000-2014.
Placid Lake shows no evidence of a transparency trend (Figure 11). This means the water quality
is stable. Transparency monitoring should continue so that this trend can be tracked in future
years.
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Ecoregion Comparisons
Minnesota is divided into 7 ecoregions based on land
use, vegetation, precipitation and geology (Figure
12). The MPCA has developed a way to determine
the "average range" of water quality expected for
lakes in each ecoregion. From 1985-1988, the MPCA
evaluated the lake water quality for reference lakes.
These reference lakes are not considered pristine,
but are considered to have little human impact and
therefore are representative of the typical lakes within
the ecoregion. The "average range" refers to the 25th
- 75th percentile range for data within each ecoregion.
For the purpose of this graphical representation, the
means of the reference lake data sets were used.
Placid Lake is in the
Northern Lakes and Forest
Ecoregion. The mean total
phosphorus, chlorophyll a
and transparency (Secchi
depth) for Placid Lake are
within the ecoregion ranges
(Figure 13).
Figure 12. Minnesota Ecoregions.
80
30
0
25
5
Chlorophyll-a (ug/L, ppb)
60
50
40
30
20
20
Secchi depth (ft)
Total Phosphorus (ug/L, ppb)
70
15
10
increased
algae
10
15
20
25
5
crystal
clear
10
0
30
0
NLF
Ecoregion
Placid
NLF
Ecoregion
Placid
NLF
Ecoregion
Placid
Figure 13. Placid Lake ranges compared to Northern Lakes and Forest Ecoregion ranges. The Placid Lake
total phosphorus and chlorophyll a ranges are from 14 data points collected in May-September of 20012003. The Placid Lake Secchi depth range is from 158 data points collected in May-September of 20002014.
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Lakeshed Data and Interpretations
Lakeshed
Understanding a lakeshed requires an understanding of basic hydrology. A watershed is defined
as all land and water surface area that contribute excess water to a defined point. The MN DNR
has delineated three basic scales of watersheds (from large to small): 1) basins, 2) major
watersheds, and 3) minor watersheds.
The Mississippi River-Brainerd Major Watershed is one of the watersheds that make up the Upper
Mississippi Basin, which drains south to the Gulf of Mexico (Figure 14). This major watershed is
made up of 128 minor watersheds. Placid Lake is located in minor watershed 10091 (Figure 15).
Figure 14. Miss. River-Brainerd Major Watershed.
Figure 15. Minor Watershed.
The MN DNR also has evaluated catchments
for each individual lake with greater than 100
acres surface area. These lakesheds
(catchments) are the “building blocks” for the
larger scale watersheds. Placid Lake falls
within lakeshed 1009101 (Figure 16).
Though very useful for displaying the land
and water that contribute directly to a lake,
lakesheds are not always true watersheds
because they may not show the water
flowing into a lake from upstream streams or
rivers. While some lakes may have only one
or two upstream lakesheds draining into
them, others may be connected to a large
number of lakesheds, reflecting a larger
drainage area via stream or river networks.
For further discussion of Placid Lake ’s
watershed, containing all the lakesheds
upstream of the Placid Lake lakeshed, see
page 17. The data interpretation of the
Figure 16. Placid Lake lakeshed (1009101)
with land ownership, lakes, wetlands, and
rivers illustrated.
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Placid Lake lakeshed includes only the immediate lakeshed as this area is the land surface that
flows directly into Placid Lake.
The lakeshed vitals table identifies where to focus organizational and management efforts for each
lake (Table 9). Criteria were developed using limnological concepts to determine the effect to lake
water quality.
KEY
Possibly detrimental to the lake
Warrants attention
Beneficial to the lake
Table 9. Placid Lake lakeshed vitals table.
Lakeshed Vitals
Lake Area
Littoral Zone Area
Lake Max Depth
Lake Mean Depth
Water Residence Time
Miles of Stream
Inlets
Outlets
Major Watershed
Minor Watershed
Lakeshed
Ecoregion
Total Lakeshed to Lake Area Ratio (total
lakeshed includes lake area)
Standard Watershed to Lake Basin Ratio
(standard watershed includes lake areas)
Wetland Coverage (NWI)
Aquatic Invasive Species
Public Drainage Ditches
Public Lake Accesses
Miles of Shoreline
Shoreline Development Index
Public Land to Private Land Ratio
Development Classification
Miles of Road
Municipalities in lakeshed
Forestry Practices
Feedlots
Sewage Management
Lake Management Plan
Lake Vegetation Survey/Plan
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Rating
descriptive
descriptive
descriptive
NA
NA
descriptive
214 acres
133 acres
39 feet
NA
NA
0 miles
0
0
10 - Mississippi River-Brainerd
10091
1009101
Northern Lakes and Forests
descriptive
descriptive
descriptive
descriptive
6:1
6:1
9.2%
None
0
1
4.61 miles
2.25
1:17.9
Recreational Developent
2.21 miles
None
None
1
Individual Subsurface Sewage Treatment Systems
descriptive
descriptive
(Inspection and assessment required for all permits and
property transfers within the Shoreland Protection Zone)
None
DNR, 1995
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Land Cover / Land Use
The activities that occur on the
land within the lakeshed can
greatly impact a lake. Land
use planning helps ensure the
use of land resources in an
organized fashion so that the
needs of the present and future
generations can be best
addressed. The basic purpose
of land use planning is to
ensure that each area of land
will be used in a manner that
provides maximum social
benefits without degradation of
the land resource.
Changes in land use, and
ultimately land cover, impact
the hydrology of a lakeshed.
Land cover is also directly
related to the land’s ability to
absorb and store water rather
than cause it to flow overland
(gathering nutrients and
sediment as it moves) towards
the lowest point, typically the
lake. Impervious intensity
describes the land’s inability to
absorb water, the higher the %
impervious intensity the more
area that water cannot
penetrate in to the soils.
Monitoring the changes in land
use can assist in future
planning procedures to
address the needs of future
generations.
Figure 17. Placid Lake lakeshed (1009101) land cover (NLCD 2011).
Phosphorus export, which is the main cause of lake eutrophication, depends on the type of land
cover occurring in the lakeshed. Figure 17 depicts the land cover in Placid Lake ’s lakeshed.
The National Land Cover Dataset (NLCD) has records from 2001 and 2011. Table 10 describes
Placid Lake’s lakeshed land cover statistics and percent change from 2001 to 2011. Overall, there
was not much change over this decade.
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Table 10. Placid Lake’s lakeshed land cover statistics and % change from 2001 to 2011 (Data Source:
NLCD).
2001
2011
% Change
Land Cover
Acres
Percent Acres
Percent 2001 to 2011
1.26
0.10
0.95
0.08
-0.0241
Barren Land (Rock/Sand/Clay)
7.79
0.61
7.73
0.61
-0.0050
Cultivated Crops
708.84
55.74
708.97
55.76
0.0231
Deciduous Forest
4.29
0.34
4.50
0.35
0.0166
Developed, Low Intensity
52.83
4.15
52.56
4.13
-0.0207
Developed, Open Space
29.02
2.28
28.46
2.24
-0.0441
Emergent Herbaceous Wetlands
30.27
2.38
29.46
2.32
-0.0635
Evergreen Forest
31.62
2.49
31.21
2.45
-0.0319
Grassland/Herbaceous
165.91
13.05
166.30
13.08
0.0339
Open Water
145.97
11.48
147.39
11.59
0.1148
Pasture/Hay
5.04
0.40
4.80
0.38
-0.0184
Shrub/Scrub
88.83
6.99
89.06
7.00
0.0193
Woody Wetlands
1271.37
Total Area
Table 11. Placid Lake development area and % change from 1990-2000 (Data Source: UMN Landsat).
1990
2000
Change (acres)
Category
Acres
Percent Acres
Percent
1990 to 2000
7
0.66
9
0.80
2 acres
Total Impervious Area
36
2.83
38
2.99
2 acres
Urban Acreage
Demographics
Placid Lake is classified as a Recreational Development lake. Recreational
Development lakes usually have between 60 and 225 acres of water per mile
of shoreline, between 3 and 25 dwellings per mile of shoreline, and are more
than 15 feet deep
The Minnesota Department of Administration Geographic and Demographic
Analysis Division extrapolated future population in 5-year increments out to
2035. Compared to Crow Wing County as a whole, Deerwood Township has
a higher growth projection (Figure 18). (source:
http://www.demography.state.mn.us)
Population Growth Projection Compared to 2010 Population
30%
25%
Deerwood Township; 2010 population = 1474
Crow Wing County; 2010 population = 62,500
Ec Dev Region; 2010 population = 163,003
Percent
20%
15%
10%
5%
0%
2010
2015
2020
2025
2030
2035
Year
Figure 18. Population growth projection for adjacent townships and Crow Wing County.
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Lakeshed Water Quality Protection Strategy
Each lakeshed has a different makeup of public and private lands. Looking in more detail at the
makeup of these lands can give insight on where to focus protection efforts. The protected lands
(easements, wetlands, public land) are the future water quality infrastructure for the lake.
Developed land and agriculture have the highest phosphorus runoff coefficients, so this land
should be minimized for water quality protection.
The majority of the land within Placid Lake ’s lakeshed is privately owned forested uplands (Table
12). This land can be the focus of development and protection efforts in the lakeshed.
Table 12. Land ownership, land use/land cover, estimated phosphorus loading, and ideas for protection and
restoration in the lakeshed (Sources: County parcel data and the 2011 National Land Cover Dataset).
15.1
Private (80.4)
Land Use (%)
Runoff
Coefficient
Lbs of
phosphorus/acre/year
Estimated
Phosphorus
Loading
Public (4.5)
Wetlands
Open
Water
County
State
Federal
7.36
15.1
4.54
0
0
Developed
Agriculture
Forested
Uplands
4.11
12.20
54.25
0.45 – 1.5
0.26 – 0.9
0.09
0.09
0.09
0.09
0.09
24 –78
40 –140
62
0.7
5.198
0
0
Cropland
Focus of
development and
protection
efforts
State
Forest
National
Forest
Other
2.50
Acreage x runoff
coefficient
Description
Potential
Phase 3
Discussion
Items
Focused on
Shoreland
Shoreline
restoration
Restore
wetlands;
CRP
Open,
pasture,
grassland,
shrubland
Forest
stewardship
planning, 3rd
party
certification,
SFIA, local
woodland
cooperatives
Protected
Protected by
Wetland
Conservation
Act
County
Tax Forfeit
Lands
DNR Fisheries approach for lake protection and restoration
Credit: Peter Jacobson and Michael Duval, Minnesota DNR Fisheries
In an effort to prioritize protection and restoration efforts of fishery lakes, the MN DNR has
developed a ranking system by separating lakes into two categories, those needing protection and
those needing restoration. Modeling by the DNR Fisheries Research Unit suggests that total
phosphorus concentrations increase significantly over natural concentrations in lakes that have
watershed with disturbance greater than 25%. Therefore, lakes with watersheds that have less
than 25% disturbance need protection and lakes with more than 25% disturbance need restoration
(Table 13). Watershed disturbance was defined as having urban, agricultural and mining land
uses. Watershed protection is defined as publicly owned land or conservation easement.
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Table 13. Suggested approaches for watershed protection and restoration of DNR-managed fish lakes in
Minnesota.
Watershed
Watershed
Management
Comments
Disturbance
Protected
Type
(%)
(%)
Vigilance
Sufficiently protected -- Water quality supports healthy and
diverse native fish communities. Keep public lands protected.
< 75%
Protection
Excellent candidates for protection -- Water quality can be
maintained in a range that supports healthy and diverse native
fish communities. Disturbed lands should be limited to less than
25%.
n/a
Full Restoration
Realistic chance for full restoration of water quality and improve
quality of fish communities. Disturbed land percentage should
be reduced and BMPs implemented.
Partial Restoration
Restoration will be very expensive and probably will not achieve
water quality conditions necessary to sustain healthy fish
communities. Restoration opportunities must be critically
evaluated to assure feasible positive outcomes.
> 75%
< 25%
25-60%
> 60%
n/a
The next step was to prioritize lakes within each of these management categories. DNR Fisheries
identified high value fishery lakes, such as cisco refuge lakes. Ciscos (Coregonus
artedi) can be an early indicator of eutrophication in a lake because they require cold hypolimnetic
temperatures and high dissolved oxygen levels. These watersheds with low disturbance and high
value fishery lakes are excellent candidates for priority protection measures, especially those that
are related to forestry and minimizing the effects of landscape disturbance. Forest stewardship
planning, harvest coordination to reduce hydrology impacts and forest conservation easements are
some potential tools that can protect these high value resources for the long term.
Placid Lake’s lakeshed is classified with having 20% of the watershed protected and 15% of the
watershed disturbed (Figure 19). Therefore, this lakeshed should have a protection focus. Goals
for the lake should be to limit any increase in disturbed land use. Placid Lake is a headwaters
lakeshed, which means that no other lakesheds flow into it (Figure 20).
Percent of the Watershed Protected
0%
75%
100%
Placid Lake
(20.2%)
Percent of the Watershed with Disturbed Land Cover
0%
25%
100%
Placid Lake
(15.1%)
Figure 19. Placid Lake’s lakeshed percentage of
watershed protected and disturbed.
RMB Environmental Laboratories, Inc.
Figure 20. Lakesheds that contribute water to the
Placid Lake lakeshed. Color-coded based on
management focus (Table 13).
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Status of the Fishery (DNR, as of 06/13/1988)
Northern pike and Bluegill net catches indicated above average populations. These species catch
rates exceed the third quartile of the Brainerd area median for group I lakes that are less than 230
acres with a total alkalinity of less than 47. Yellow Bullhead, Hybrid Sunfish, Pumpkinseed and
Black Crappie exhibited average populations since the net catches were between the first and third
quartile of the area median. Brown Bullhead, Yellow Perch, and Walleye net catches indicate a
below average population with catch rates below the first quartile of the area median. The northern
pike abundance seems to indicate an upward trend. The two previous surveys (June 1971 and
June 1983) had net catches of 7.0 and 9.3/gillnet. The Northern Pike ranged in sixe from 11.1 to
31.4 at time of capture. The average size was 19.1 inches long. Age class II thru IX were present
in the nets with growth rates on the low side of average. Yellow Bullhead populations took a large
jump in gill net catches, 0.1 in 197, 9.7 in 1983, 64.33 in 1988; yet trapnet catches were down 61.0
in 1971, 66.8 in 1983 and 19.25 in 1988. The brown bullhead is quite low. The Bluegill population
has remained high with age classes IV thru X represented in the net catch and all classes indicated
a slow growth rate in comparison to statewide averages. Yellow perch population remains
extremely low. The Walleye population shows the following changes: 0.0 in 1971, 0.3 in 1983, and
0.67 in 1988. Placid Lake was stocked with Walleye fingerling in 1979, fry in 1980 and fingerling
again in 1982.
See the link below for specific information on gillnet surveys, stocking information, and fish
consumption guidelines. http://www.dnr.state.mn.us/lakefind/showreport.html?downum=18007600
Key Findings / Recommendations
Monitoring Recommendations
Transparency monitoring at site 201 should be continued annually. It is important to continue
transparency monitoring weekly or at least bimonthly every year to enable year-to-year
comparisons and trend analyses. Total Phosphorus and chlorophyll a monitoring should continue,
as the budget allows, to track trends in water quality.
Overall Summary
Placid Lake is a mesotrophic lake (TSI = 42) with no evidence of a trend in water clarity, which
means the water quality is stable. The total phosphorus, chlorophyll a and transparency ranges
are within the ecoregion ranges.
Fifteen percent (15%) of the Placid Lake lakeshed is disturbed by development and agriculture
(Figure 19), but most of that is just pasture/hay (Figure 17), which have a much lower phosphorus
runoff rate than cropland. The threshold of disturbance where water quality tends to decline is
25%. Placid Lake is well under this threshold. More than half (54%) of the lakeshed is forested
which is generally good for water quality (Table 12).
Placid Lake has the advantage of a very small watershed (6:1, Table 9). The lake does not have
any major inlets, which means that it is probably groundwater fed. This means that the land use
practices around the lake are the greatest potential impact to the lake.
Priority Impacts to the Lake
The priority impact to Placid Lake would be the expansion of residential housing development
around the lakeshore. The conversion of small lake cabins to year-round family homes increases
the impervious surface and runoff from the lake lots. Much of the private land around the lake in
the first tier is only lightly developed and lot sizes are large (Figure 16). Further subdivision of
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these lakeshore lots and more concentrated development could increase the nutrient runoff into
the lake.
Overall, the development pressure for Placid Lake appears low. Data from 1990-2000 and 20012011 show there wasn’t much increase in development during that period of time (Tables 10-11).
Best Management Practices Recommendations
The management focus for Placid Lake should be to protect the current water quality and
lakeshed. Efforts should be focused on managing and/or decreasing the impact caused by
additional development and impervious surface area on existing lots (conversion of seasonal
cabins to year-round homes).
The current lakeshore homeowners can lessen their negative impact on water quality by installing
or maintaining the existing tress on their properties. Forested uplands contribute significantly less
phosphorus (lbs/acre/year) than developed land cover (Table 12). In addition, filter strips or native
vegetative buffers could be installed to decrease or slow the runoff reaching the water’s edge.
Septic systems should be pumped and inspected regularly.
The lake still has large undeveloped shoreline parcels (Figure 16). Because a lot of undeveloped
private land still exists, there is a great potential for protecting this land with conservation
easements and aquatic management areas (AMAs). Conservation easements can be set up
easily and with little cost with help from organizations such as the Board of Soil and Water
Resources and the Minnesota Land Trust. AMAs can be set up through the local DNR fisheries
office.
Project Implementation
The best management practices above can be implemented by a variety of entities. Some
possibilities are listed below.
Individual property owners
 Shoreline restoration
 Rain gardens
 Aquatic plant bed protection (only remove a small area for swimming)
 Conservation easements
Lake Associations
 Lake condition monitoring
 Ground truthing – visual inspection upstream on stream inlets
 Watershed runoff mapping by a consultant
 Shoreline inventory study by a consultant
 Conservation easements
Soil and Water Conservation District (SWCD) and Natural Resources Conservation Service
(NRCS)
 Shoreline restoration
 Stream buffers
 Wetland restoration
 Work with farmers to
o Restore wetlands
o Implement conservation farming practices
o Land retirement programs such as Conservation Reserve Program
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County-wide Recommendation
In order to better manage the impact of septic systems on lake water quality, it is recommended
that the county implement a lake-wide septic inspection program. In a program such as this, the
county would focus on one to three lakes a year, pull septic system records on those lakes, and
require old systems to be inspected. This program can rotate through the county doing a few lakes
each year.
Since conversion of small cabins to large lake homes could be a future issue, strengthening county
shoreline ordinances such as set-backs, impervious surface limits and shoreline alteration
(installation of retaining walls and removing trees) will help to protect water quality.
Organizational contacts and reference sites
Placid Area Lake Association
PO Box 311, Deerwood, MN 56444
Crow Wing County Land Services
Department
322 Laurel Street, Suite 14, Brainerd, MN 56401
218-824-1128
http://crowwing.us/index.aspx?nid=211
Crow Wing Soil and Water
Conservation District
322 Laurel Street, Suite 13, Brainerd, MN 56401
(218) 828-6197
http://www2.co.crow-wing.mn.us/swcd/
DNR Fisheries Office
1601 Minnesota Drive, Brainerd, MN 56401
(218) 828-2550
http://www.dnr.state.mn.us/lakefind/index.html
Regional Minnesota Pollution
Control Agency Office
7678 College Road, Suite 105, Baxter, MN 56425
(218) 828-2492
http://www.pca.state.mn.us
Regional Board of Soil and Water
Resources Office
1601 Minnesota Drive, Brainerd, MN 56401
(218) 828-2383
http://www.bwsr.state.mn.us
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