Big Trout Lake
18-0315-00 CROW WING COUNTY
Lake Water Quality
Summary
Big Trout Lake is located just east of Pine River, Minnesota. It covers
1,363 acres, which places it in the upper 10% of lakes in Minnesota in
terms of size.
Big Trout Lake has no major inlets or outlets. It has a connection with
Lower Whitefish Lake and is tied to the Whitefish Chain of Lakes. Water
levels in 13 of the lakes of the Whitefish Chain are controlled by the U.S. Army Corps of Engineers.
They do this by adjusting water outflow levels at their dam in the city of Crosslake. The Pine River
flows into and out of Whitefish Lake and eventually joins the Mississippi River.
Water quality data have been collected on Big Trout Lake since 1975. These data show that the
lake is at the oligotrophic/mesotrophic border (TSI 39-41), which is characterized by clear water
throughout the summer and excellent recreational opportunities (page 9).
The Whitefish Area Property Owners Association has been active since 1970 (Tables 2, 3). Their
mission statement is "to promote environmental stewardship throughout the Whitefish area and the
Pine River Watershed". The Association has been involved in numerous activities including water
quality monitoring, education, state regulations, fishing and supporting local business.
Table 1. Big Trout Lake location and key physical characteristics.
Location Data
MN Lake ID:
Physical Characteristics
18-0315-00
Surface area (acres):
1,363
County:
CROW WING
Littoral area (acres):
369
Ecoregion:
Northern Lakes & Forests
% Littoral area:
27%
Major Drainage Basin:
Upper Mississippi
Max depth (ft), (m):
128, 39
Latitude/Longitude:
46.71861111/-94.15861111
Inlets:
Invasive Species:
Curly-leaf pondweed
Outlets:
Connected to Whitefish
Lake
Public Accesses:
1
Table 2: Availability of data and an observation of the quantity of sample points.
Data Availability
Transparency data
Numerous yearly Secchi readings from 1992-2011
through the MPCA CLMP program.
Chemical data
Total Phosphorus and Chlorophyll a data have been
collected by WAPOA in 2003-2011.
Inlet/Outlet data
Recommendations
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--
Big Trout Lake has no major inlets or outlets
For recommendations refer to page 19.
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Lake Map
Figure 1. Map of Big Trout Lake with 2010 aerial imagery and illustrations of sample site locations, inlets and
outlets, and public access points. The light green areas in the lake illustrate the littoral zone, where the
sunlight can usually reach the lake bottom allowing aquatic plants to grow.
Table 3. Monitoring programs and associated monitoring sites. Monitoring programs include the Citizen Lake
Monitoring Program (CLMP), Minnesota Pollution Control Agency (MPCA), and Whitefish Area Property
Owners Association (WAPOA).
Lake Site
Depth (ft)
Monitoring Programs
101
201
202
203
204
205
206* Primary Site
120
100
15
70
65
116
70
MPCA: 1986
CLMP: 1975
CLMP: 1980
CLMP: 1982-1984
CLMP: 1984, 1986-1989, 1991
CLMP: 2005
CLMP: 1992-2010; WAPOA: 2003-2011
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Average Water Quality Statistics
The information below describes available chemical data for Big Trout Lake through 2011. The
data set is limited, and all parameters, with the exception of total phosphorus, chlorophyll a and
secchi depth, are means for just 1986 MPCA data.
Minnesota is divided into seven 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.
Table 4. Water quality means compared to ecoregion ranges and impaired waters standard.
Impaired
Waters
Standard2
Parameter
Mean
Ecoregion
Range1
Total phosphorus (ug/L)
12
14 - 27
> 30
3
3
4 - 10
>9
Chlorophyll a max (ug/L)
6
<15
Secchi depth (ft)
15
7.5 - 15
Dissolved oxygen
Dimitic
Chlorophyll a (ug/L)
Interpretation
Results are better than the
expected range for the ecoregion.
< 6.5
Dissolved oxygen depth profiles
show that the deep areas of the
lake are anoxic in late summer.
see page 8
0.38
0.40 - 0.75
Indicates insufficient nitrogen to
support summer nitrogen-induced
algae blooms.
Alkalinity (mg/L)
101
40 - 140
Indicates a low sensitivity to acid
rain and a good buffering
capacity.
Color (Pt-Co Units)
6.7
10 - 35
Indicates very clear water with
little to no tannins (brown stain).
pH
8.2
7.2 - 8.3
Characteristic of a hard water
lake. Lake water with pH less
than 6.5 can affect fish spawning
and the solubility of metals in the
water.
Chloride (mg/L)
1.4
0.6 - 1.2
Slightly above the ecoregion
average but still considered low
level.
Total Suspended Solids
1.5
<1 - 2
Within the ecoregion average
range.
210
50 - 250
Within the ecoregion average
range.
31:1
25:1 – 35:1
Indicates the lake is phosphorus
limited, which means that algae
growth is limited by the amount of
phosphorus in the lake.
Total Kieldahl Nitrogen
(mg/L)
(mg/L)
Specific Conductance
(umhos/cm)
Total Nitrogen :Total
Phosphorus
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.
Parameters
Total Phosphorus Mean (ug/L):
Total Phosphorus Min:
Total Phosphorus Max:
Number of Observations:
Chlorophyll a Mean (ug/L):
Chlorophyll-a Min:
Chlorophyll-a Max:
Number of Observations:
Secchi Depth Mean (ft):
Secchi Depth Min:
Secchi Depth Max:
Number of Observations:
Site
206
12
6
22
40
3
<1
6
40
15
6.5
23.5
86
Figure 2. Big Trout Lake total phosphorus, chlorophyll a and transparency historical ranges. The arrow
represents the range and the black dot represents the historical mean (Primary Site 206). Figure adapted
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 means for Big Trout Lake range from 11.6-17.7 ft (Figure 3). Transparency was
highest in 1993 and 1999. 2000-2011 transparency was lower than the long-term mean. For trend
analysis, see page 10. Transparency monitoring should be continued at site 206 to track water
quality in Big Trout Lake.
20
Transparency: Annual Means
18
16
Secchi Depth (ft)
14
12
10
8
6
4
Annual Means
2
Long-term Mean
0
Figure 3. Annual mean transparency for site 206.
Big Trout Lake transparency ranges from 6.5 to 23.5 feet throughout the summer. Figure 4 shows
the seasonal transparency dynamics. The maximum Secchi reading is usually obtained in early
summer. Big Trout Lake transparency is high in May and June and declines through August. The
transparency then rebounds in October after fall turnover. 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
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
1992
1993
25
1994
1995
Secchi Depth (ft)
20
1996
1997
15
1998
1999
2000
10
2001
2003
5
2004
2005
0
2006
2007
Figure 4. Seasonal transparency dynamics and year-to-year comparison (site 206). The grey 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. Big Trout Lake was rated as being "crystal clear" 59% of the time
between 1989-1991, and 2003-2011 (Figure 5).
Physical Appearance Rating
2%
39%
59%
59%
Crystal clear water
39%
Not quite crystal clear – a little algae visible
2%
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. Physical appearance rating, as rated by the volunteer monitor.
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As the secchi depth decreases, the perception of recreational suitability of the lake decreases. Big
Trout Lake was rated as being "beautiful" 80% of the time from 1989-1991, and 2003-2011.
Recreational Suitability Rating
20%
80%
Beautiful, could not be better
20%
Very minor aesthetic problems; excellent for
swimming, boating
0.3%
Swimming and aesthetic enjoyment of the lake
slightly impaired because of algae levels
0%
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
80%
Figure 6. Recreational suitability rating, as rated by the volunteer monitor.
Total Phosphorus
Total phosphorus was
evaluated in Big Trout
Lake in 2003-2011.
The data indicate that
phosphorus
concentrations are
lowest in July, and
higher in May and
September (Figure 7).
This dynamic could be
related to lake turnover
during those months.
There was one
unusually high
phosphorus data point
in July of 2008.
Total Phosphorus
25
20
Total Phosphorus (ug/L)
Big Trout Lake is
phosphorus limited,
which means that algae
and aquatic plant
growth is dependent
upon available
phosphorus.
Mesotrophic
15
10
2003
2004
2005
2006
2007
2008
2009
2010
2011
5
Oligotrophic
0
Figure 7. Historical total phosphorus concentrations (ug/L) at site 206 for Big Trout
Lake.
Phosphorus should continue to be monitored to track any future changes in water quality.
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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
2003
2004
10
2005
Chlorophyll a (ug/L)
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.
2006
8
2007
6
2008
2009
4
2010
2011
2
Minor Algae
Bloom
0
Figure 8. Chlorophyll a concentrations (ug/L) for Big Trout Lake.
Chlorophyll a was evaluated in Big Trout Lake in 2003-2011 (Figure 8). Chlorophyll a
concentrations remained well below 10 ug/L, indicating clear water all summer and no nuisance
algae blooms.
Dissolved Oxygen
Dissolved Oxygen (mg/L)
0
2
4
6
8
10
12
14
1
2
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.
3
4
5
6
7
8
9
10
Depth
11
(m)
12
Big Trout Lake is a relatively deep lake, with a maximum depth
of 128 ft. Dissolved oxygen profiles from 1992-2001 indicate
that Big Trout Lake stratifies in the summer (Figure 9). The
thermocline occurs at 36-42 feet, although the oxygen does not
drop below 5 mg/L. This is excellent habitat for Cisco (Tullibee)
fish. Big Trout Lake is designated by the DNR as a Cisco refuge
lake. To read more about this designation, see the bottom of
page 16. In addition, Big Trout Lake is stocked with Lake Trout.
13
14
15
16
17
18
Figure 9. Dissolved oxygen profiles for Big Trout
Lake in 2001.
19
20
21
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Trophic State Index
Table 6. Trophic State Index.
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.
The results from these three measurements cover different
units and ranges and thus cannot be directly compared to
each other or averaged. In order to standardize these
three measurements to make them directly comparable,
we convert them to a trophic state index (TSI).
Trophic State Index
TSI Total Phosphorus
TSI Chlorophyll-a
TSI Secchi
TSI Mean
Site 206
40
41
38
40
Trophic State:
Oligotrophic/
Mesotrophic
Numbers represent the mean TSI for each
parameter.
100
The mean TSI for Big Trout Lake falls on the border
between oligotrophic and mesotrophic (39-41). There is
good agreement between the TSI for phosphorus,
chlorophyll a and transparency, indicating that these
variables are strongly related (Table 6).
Hypereutrophic
70
Eutrophic
Lakes on the oligotrophic/mesotrophic
border (TSI 39-41) are characteristic of
Big Trout Lake
clear water throughout the summer and
are excellent for recreation (Table 7).
The bottom of the deep areas of the lake becomes
anoxic (no oxygen) during the summer, which is
inhospitable to game fish. This occurrence is common in
Minnesota lakes.
50
Mesotrophic
40
Oligotrophic
0
Figure 10. Trophic state index chart with
corresponding trophic status.
Table 7. Trophic states and corresponding lake and fishery conditions.
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.
There is not enough historical data to perform trend analysis for total phosphorus or chlorophyll a
on Big Trout Lake. Site 101 had enough transparency data to perform a short-term and long-term
trend analysis (Table 8). The data was analyzed using the Mann Kendall Trend Analysis.
Table 8. Trend analysis for Big Trout Lake.
Lake Site
Parameter
Date Range
Trend
Probability
206
Transparency
1992-2011
Declining
99.9%
206
Transparency
2000-2011
Improving
90%
Transparency Trend for Big Trout Lake
25.0
Secchi Depth (ft)
20.0
15.0
10.0
Long-term trend
Short-term trend
5.0
0.0
Figure 11. Long-term and short-term transparency trends for site 206 in Big Trout Lake.
Site 206 shows a statistically significant declining trend in transparency from 1992-2011 (Figure
11). However, since 2000, there is an improving significant trend occurring, which means that the
lake is rebounding from the previous decline. Transparency monitoring should continue at site 206
so that this trend can be tracked in future years. If the lake continues to improve, the long-term
trend should not be declining in the future. See the recommendations on page 19 for more insight
to the trends.
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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.
Figure 12. Map of Minnesota with the
seven ecoregions.
60
30
50
25
0
5
40
30
20
20
Secchi depth (ft)
Chlorophyll-a (ug/L, ppb)
Total Phosphorus (ug/L, ppb)
Big Trout Lake is in the
Northern Lakes and Forests
Ecoregion. The means for
phosphorus and chlorophyll a
were within the ecoregion
ranges, while the
transparency is better than
the ecoregion range (Fig 13).
15
10
increased
algae
10
15
crystal
clear
20
10
5
0
a
25
0
NLF
Ecoregion
Big Trout
b
NLF
Ecoregion
Big Trout
c
NLF
Ecoregion
Big Trout
Figures 13a-c. Big Trout Lake ranges compared to Northern Lakes and Forest Ecoregion ranges. The Big
Trout Lake total phosphorus and chlorophyll a ranges are from 30 data points collected in May-September of
2003-2008. The Big Trout Lake Secchi depth range is from 76 data points collected in May-September from
1992-2008.
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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 Pine River Major Watershed is one of the watersheds that make up the Upper Mississippi
River Basin, which eventually drains south to the Gulf of Mexico (Figure 14). This major watershed
is made up of 69 minor watersheds. Big Trout Lake is located in minor watershed 11065 (Figure
15).
Figure 14. Pine River Watershed.
Figure 15. Minor Watershed 11065.
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. Big Trout Lake falls
within the lakeshed 1106500 (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 Big Trout Lake’s full watershed, see
page 17. The data interpretation of the
Big Trout Lake lakeshed includes only
the immediate lakeshed as this area is
Figure 16. The Big Trout Lake lakeshed (1106500).
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the land surface that flows directly into Big Trout 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. Big Trout 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
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
1,363 acres
500 acres
128 ft.
48 ft.
NA
0.3
Connection to Whitefish Lake
Connection to Whitefish Lake
11 – Pine River
11065
1106500
Northern Lakes and Forest
descriptive
descriptive
descriptive
descriptive
NA
descriptive
descriptive
descriptive
descriptive
descriptive
6:1
6:1
4.4%
Curly-leaf pondweed
Present
1
8.51
1.6
0.5:1
General Development
15.4
None
County Forest Management:
http://www.co.crowwing.mn.us/index.aspx?NID=261
None
Individual Subsurface Sewage Treatment
Systems (Inspection and assessment required for all
descriptive
descriptive
permits and property transfers within the Shoreland
Protection Zone)
Healthy Lakes & Rivers Partnership program,
2008
None
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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 lands 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 lands 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. The Big Trout Lake (1106500) lakeshed land cover
(http://land.umn.edu).
Phosphorus export, which is the
main cause of lake eutrophication, depends on the type of land cover occurring in the lakeshed.
Figure 17 depicts Big Trout Lake’s lakeshed land cover.
The University of Minnesota has online records of land cover statistics from years 1990 and 2000
(http://land.umn.edu). Table 10 describes Big Trout Lake's lakeshed land cover statistics and
percent change from 1990 to 2000. Due to the many factors that influence demographics, one
cannot determine with certainty the projected statistics over the next 10, 20, 30+ years, but one
can see the transition within the lakeshed from agriculture, grass/shrub/wetland, and water
acreages to forest and urban acreages. The largest change in percentage is the decrease in
grass/shrub/wetland cover (57.3%); however, in acreage, forest cover has increased the most (668
acres). In addition, the impervious intensity has increased, which has implications for storm water
runoff into the lake. The increase in impervious intensity is consistent with the increase in urban
acreage.
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Table 10. Big Trout lakeshed land cover statistics and % change from 1990 to 2000 (http://land.umn.edu).
1990
2000
% Change
1990 to 2000
Land Cover
Acres
Percent
Acres
Percent
469
5.76
368
4.52
21.5% Decrease
Agriculture
5,102
62.64
5,770
70.84
13.1% Increase
Forest
829
10.18
354
4.35
57.3% Decrease
Grass/Shrub/Wetland
1,531
18.8
1,406
17.26
8.2% Decrease
Water
214
2.63
247
3.03
15.4% Increase
Urban
Impervious Intensity %
0
1-10
11-25
26-40
41-60
61-80
81-100
Total Area
Total Impervious Area
(Percent Impervious Area
Excludes Water Area)
7,990
40
41
37
28
8
0
98.1
0.49
0.5
0.45
0.34
0.1
0
7,955
66
63
34
15
6
5
97.67
0.81
0.77
0.42
0.18
0.07
0.06
0.4% Decrease
65.0% Increase
53.7% Increase
8.1% Decrease
46.4% Decrease
25.0% Decrease
500% Increase
8,145
40
0.6
8,145
41
0.61
2.5% Increase
Demographics
Big Trout Lake is classified as a general development
lake. General development lakes usually have more than
225 acres of water per mile of shoreline 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. These
projections are shown in Figure 18 below. Compared to
Crow Wing County as a whole, the city of Crosslake has a higher extrapolated growth projection,
while Ideal and Timothy Townships, as well as the cities of Fifty Lakes and Manhattan Beach, have
lower extrapolated growth projections (Figure 18)
Population Growth Projection
70%
Percentage of 2006
Population
Figure 18.
Population growth
projection for Crow
Wing County.and
area Townships
(source:
http://www.demogr
aphy.state.mn.us/r
esource.html?Id=1
9332)
60%
50%
Ideal Tow nship & City of Fifty Lakes; 2006 population: 983 & 406, respectively
Timothy Tow nship; 2006 population: 155
City of Manhattan Beach; 2006 population: 62
City of Crosslake; 2006 population: 2,052
Crow Wing County; 2006 population: 61,038
40%
30%
20%
10%
0%
-10%
2006
2010
2015
2020
2025
2030
2035
Extrapolation
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Big Trout 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 Big Trout’s lakeshed is made up of private forested uplands. This
land can be the focus of development and protection efforts in the lakeshed.
Table 11. Land ownership, land use/land cover, estimated phosphorus loading, and ideas for protection and
restoration in the lakeshed (Sources: Crow Wing County parcel data, National Wetlands Inventory, and the
2006 National Land Cover Dataset).
19%
Private (55%)
Land Use (%)
Public (26%)
Developed
Agriculture
Forested
Uplands
Other
Wetlands
Open
Water
County
State
Federal
3%
4.5%
27%
18.5%
2%
19%
1%
24%
1%
0.45 - 1.5
0.26 - 0.9
0.09
0.09
0.09
0.09
Cropland
Focus of
development and
protection
efforts
State
Forest
National
Forest
Runoff
Coefficient
Lbs of
phosphorus/acre/
0.09
year
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 12). 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 12. Suggested approaches for watershed protection and restoration of DNR-managed fish lakes in
Minnesota.
Watershed
Watershed
Management
Comments
Protected
Disturbance
Type
(%)
(%)
Sufficiently protected -- Water quality supports healthy and
diverse native fish communities. Keep public lands protected.
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%.
> 75%
Vigilance
< 75%
Protection
25-60%
n/a
Full Restoration
> 60%
n/a
Partial Restoration
< 25%
Realistic chance for full restoration of water quality and improve
quality of fish communities. Disturbed land percentage should
be reduced and BMPs implemented.
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.
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.
Big Trout Lake is classified with having 45.3% of the watershed protected and 6.2% of the
watershed disturbed (Figure 19). Therefore, Big Trout Lake should have a protection focus. Goals
for the lake should be to limit any increase in disturbed land use. In addition, Big Trout Lake was
designated by DNR Fisheries as a high valued fishery lake because of its cisco population.
Figure 20 displays the area that could contribute water to the lakeshed of interest. This particular
lakeshed is a headwaters catchment, which means no additional lakesheds flow into it. The area
highlighted green is the full watershed for Big Trout Lake.
Percent of the Watershed Protected
75%
0%
100%
Big Trout Lake
(45.3%)
Percent of the Watershed with Disturbed Land Cover
0%
25%
100%
Big Trout Lake
(6.2%)
Figure 19. Big Trout Lake lakeshed’s percentage of
watershed protected and disturbed.
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Figure 20. Upstream lakesheds that contribute water
to the Big Trout lakeshed. Color-coded based on
management focus (Table 12).
2011 Big Trout Lake
Big Trout, Status of the Fishery (as of 07/18/2005)
Big Trout Lake is the only lake in the Brainerd management area that is stocked with lake trout. Big
Trout covers 1,342 acres, and is 128 feet deep. The littoral area, less than 15 ft deep, covers 27%
of the lake. Water clarity is good with a secchi depth of 18 ft. A public boat access is located on the
eastern shore, or boaters can access through a channel from Whitefish Lake. The lake is heavily
developed with 237 homes, 2 resorts, and 2 youth camps along its 8.5 miles of shoreline. A 2010
survey of the plant community found 41 native species, and one invasive plant (curlyleaf
pondweed). Protection of aquatic vegetation, especially emergent vegetation, is important for
maintaining good water quality. Also vegetation is critical for fish spawning areas as well as
providing cover for fish.
Northern pike were captured at the highest rate to date at 7.2/gillnet. Average length was 20.6
inches and weighing 2.1 lbs. Northern pike up to 34.4 inches were captured. Northern pike over 24
inches made up 19% of catch.
Walleyes are not stocked directly into Big Trout, but are stocked into connecting Whitefish Lake
annually as fry, and every other year as fingerlings. The walleye gillnet catch of 0.7/net was low,
but the average size was nice at 22.1 inches and weight at 4.2 lbs. Walleye up to 28.4 inches were
caught.
Both largemouth and smallmouth bass are present in Big Trout. Largemouth bass were sampled
throughout the Whitefish Chain, including Big Trout, by a spring electrofishing survey. They were
caught at a rate of 112.5/hr. More data can be found in the Whitefish lake report.
Bluegill numbers were above average, but their size leaves something to be desired. Average
length was 4.9 inches, and only 5% were over 7 inches. The black crappie gillnet catch was
average. All black crappies from gillnets were over 9 inches. All crappies captured in trapnets were
from the 2010 year class and were less than 4 inches in length.
Tullibee (Cisco) numbers at 12.5/gillnet were well above average. Nearly all (98%) of tullibee
(cisco) were between 6 and 8 inches in length. At this size they are a valuable forage species for
walleye, northern pike, and lake trout. Lake whitefish were also caught at above average numbers
at a rate of 1.9/ gillnet. They averaged 1.7 lbs, and would be of interest to anglers.
No lake trout were sampled in this survey, though they are present in the lake and are stocked into
Big trout every other year. Other fish species present in this survey included smallmouth bass, rock
bass, pumpkinseed sunfish, hybrid sunfish, brown bullhead, yellow bullhead, bowfin, greater
redhorse, and green sunfish.
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=18031500
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Key Findings / Recommendations
Monitoring Recommendations
Transparency monitoring at site 206 should be continued annually without gaps. It is important to
continue transparency monitoring weekly or at least bimonthly every year to enable year-to-year
comparisons and trend analyses. Phosphorus and chlorophyll a monitoring should continue at site
206, as the budget allows, to track future water quality trends.
Overall Conclusions
Overall, Big Trout Lake has excellent water quality, and is in good shape for lakeshed protection. It
is an oligotrophic/mesotrophic lake (TSI=40) with a declining long-term trend and an improving
short-term trend in transparency. This means the lake is recovering from decline that occurred in
the 1990s. Based on a review of aerial photos, comparing 1991 to 2003, this may be due to
increasing development directly adjacent to the shore.
Twenty-six percent (26%) of the lakeshed is in public ownership, and 45% of the watershed is
protected, while 6% of the watershed is disturbed (Figure 19). Big Trout Lake’s lakeshed is wellforested, which is good protection for water quality. When subtracting out the water area, 86% of
the lakeshed is forested (Table 10).
Big Trout Lake is at an advantage in that it is a headwaters catchment, which means that no other
lakesheds flow into it. This means the land practices around the lake are the main impact to the
lake’s water quality.
Big Trout Lake is the only lake in the Brainerd DNR management area that’s stocked with lake
trout. It is also designated as a Cisco Refuge Lake by the DNR. The deep, well oxygenated water
provide good habitat for trout and ciscos (Figure 9). In the 2011 DNR Fisheries survey, the cisco
population was very healthy and abundant (page 18).
Priority Impacts to the lake
The priority impact to Big Trout Lake is the surrounding development and any future development.
There is heavy development around the shoreline of Big Trout Lake (237 homes, 2 resorts, and 2
youth camps along its 8.5 miles of shoreline), in addition to many nearby towns: Crosslake, Fifty
Lakes and Manhattan Beach. The City of Crosslake alone is expected to grow another 25% in the
next 10 years (Figure 18). The entire land area between Big Trout and Whitefish is divided into
parcels, though many are undeveloped.
The concern with increased development is the conversion of forested land to a land use with
increased impervious surfaces, such as roofs, driveways, and well groomed lawns. Poor septic
system maintenance could also impact water quality. Phosphorus loading will increase when land
use changes from forested to developed. A way to mitigate this issue is through the installation of
Best Management Practices (BMPs).
Further away from the lake itself, but still within the lakeshed there are numerous tax forfeited land
parcels. Some of this area is being used to silviculture (timber management). These areas would
also benefit water quality by following BMPs.
Best Management Practices Recommendations
The management focus for Big Trout Lake should be to protect the water quality and the lakeshed.
Protection efforts should be focused on managing and/or decreasing the impact caused by
additional development, and impervious surface area. Project ideas include protecting land with
conservation easements, enforcing county shoreline ordinances, smart development, shoreline
restoration, rain gardens, and septic system maintenance. Although it may not be possible to
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decrease the impervious area in the lakeshed, it is possible to reduce the impact of the impervious
surface by retaining stormwater instead of allowing it to runoff into the streams.
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.
Organizational contacts and reference sites
Whitefish Area Property Owners
Association
DNR Fisheries Office
Regional Minnesota Pollution
Control Agency Office
Crow Wing Soil and Water
Conservation District
Crow Wing County Environmental
Services Department
http://www.minnesotawaters.org/group/whitefish/test-2-0/
1601 Minnesota Drive, Brainerd, MN 56401
218-828-2550
[email protected]
7678 College Road, Suite 105, Baxter, MN 56425
218-828-2492, 800-657-3864
http://www.pca.state.mn.us/pyri3df
Crow Wing County Land Services Building
322 Laurel St. Suite 13, Brainerd, MN 56401
218-828-6197
http://www.co.crow-wing.mn.us/swcd/
Crow Wing County Land Services Building
322 Laurel St. Suite 14, Brainerd, MN 56401
218-824-1125
http://www.co.crow-wing.mn.us/index.aspx?nid=211
Funding
This project was funded in part by the Board of Water & Soil Resources and the Initiative
Foundation, a regional foundation.
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