Big Deep Lake
11-0277-00 CASS COUNTY
Lake Water Quality
Summary
Big Deep Lake is located near Hackensack, MN in
Cass County. It is a long and narrow lake covering
535 acres (Table 1).
Big Deep Lake has two inlets and one outlet, which
classify it as a drainage lake. Water enters Big Deep
Lake from Boy River and Bass Pond in the south. The
Boy River exits in the northeast corner of Big Deep
Lake and carries water eastward toward Leech Lake.
Water quality data have been collected on Big Deep
Lake since 1998 (Tables 2–3). These data show that the lake is oligotrophic (TSI = 35) with clear
water conditions most of the summer and excellent recreational opportunities.
The Big Deep Lake Property Owners Association is involved in many activities including water
quality monitoring, loon watches, and is a member of the Association of Cass County Lakes
(ACCL).
Table 1. Big Deep Lake location and key physical characteristics.
Location Data
Physical Characteristics
MN Lake ID:
11-0277-00
Surface area (acres):
535
County:
Cass
Littoral area (acres):
48
Ecoregion:
Northern Lakes and Forests
% Littoral area:
9
Major Drainage Basin:
Upper Mississippi River
Max depth (ft):
107
Latitude/Longitude:
46.9121, -94.3869
Inlets:
2
Invasive Species:
None as of 2011
Outlets:
1
Public Accesses:
None
Table 2. Availability of primary data types for Big Deep Lake.
Data Availability
Transparency data
Good data set from 1998-2002, 2005-2011.
Chemical data
Not available.
Inlet/Outlet data
Not available.
Recommendations
For recommendations refer to page 18.
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Lake Map
Figure 1. Map of Big Deep Lake with 2010 aerial imagery and illustrations of sample site locations and lake
inlets and outlets.
Table 3. Monitoring programs and associated monitoring sites. Monitoring programs include the Whitefish
Chain and Surrounding Lakes WAPOA (WCSL) and Citizen Lake Monitoring Program (CLMP).
Lake Site
201
202
203* Primary Site
204
Depth (ft)
60
50
100
30
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Monitoring Programs
CLMP: 2008-2010
CLMP: 1998-2002, 2005-2011; WCSL: 2001-2002
CLIMP: 1998-2002, 2005-2011
CLIMP: 2005-2011
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Water Quality Characteristics - Historical Means and Ranges
Table 4. Water quality means and ranges for primary sites. Years monitored for Secchi data: 1998-2002,
2005-2011.
Parameters
Secchi Depth Mean (ft):
Secchi Depth Min:
Secchi Depth Max:
Number of Observations:
Primary
Site
203
201
202
204
19
11
28
49
22
18
25
8
19
11
26
49
22
18
26
29
Figure 2. Big Deep Lake total phosphorus, chlorophyll a and transparency historical ranges. The arrow
represents the range and the black dot represents the historical mean (Primary Site 203). 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 mean transparency in Big Deep Lake ranges from 12.0 to 25.0 feet. The transparency
throughout the lake appears to be relatively uniform, with the best transparency occurring at the
deepest spot, site 203 (Figure 3). There is a gap in the data set between 2002-2005, and the
transparency jumped higher during that time frame. Transparency monitoring should be continued
annually at site 203 in order to track water quality changes.
Transparency: Annual Means
30
Secchi Depth (ft)
25
20
15
Site 201
10
Site 202
5
Site 203
Site 204
0
Figure 3. Annual mean transparency compared to long-term mean transparency.
Big Deep Lake transparency ranges from 11 to 28 ft at the primary site (203). Figure 4 shows the
seasonal transparency dynamics. The transparency in Big Deep Lake does not change much over
the summer, which is typical for a lake with good clarity. 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
1998
1999
2000
25
2001
Secchi Depth (ft)
2002
20
2003
2004
2005
15
2006
2007
10
2008
2009
5
2010
2011
0
Poly. (Pattern)
Figure 4. Seasonal transparency dynamics and year to year comparison (Primary Site 203). 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. Big Deep Lake was rated as being "crystal clear" 89% of the time
by samplers between 2008-2011 (Figure 5).
Physical Appearance Rating
11%
89%
Crystal clear water
11%
Not quite crystal clear – a little algae visible
0%
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
89%
Figure 5. Big Deep Lake physical appearance ratings by samplers from 2008-2011
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As the Secchi depth decreases, the perception of recreational suitability of the lake decreases. Big
Deep Lake was rated as being "beautiful" 94% of the time from 2008-2011 (Figure 6).
Recreational Suitability Rating
6%
94%
94%
Beautiful, could not be better
6%
Very minor aesthetic problems; excellent for
swimming, boating
0%
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
Figure 6. Recreational suitability rating, as rated by the volunteer monitor from 2008-2011.
Dissolved Oxygen
0
2
Dissolved Oxygen (mg/L) 4
6
8
10 12
14
0
1
2
3
6/14/2002
7/12/2002
8/16/2002
9/10/2002
4
5
6
Depth (m)
7
8
9
10
11
12
13
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.
Big Deep Lake is a very deep lake, with a maximum depth
of 107 feet. Dissolved oxygen profiles from 2002 indicate
that Big Deep Lake stratifies in the summer. In fact, the
oxygen shows an interesting pattern in that it is highest
from 7-9 meters (23 - 30 feet). This pattern is called a
Metalimnetic Oxygen Maxima. It is caused by algae
producing oxygen in that area of 7-9 meters deep. This
pattern is usually only observed in lakes with good
transparency and a very small closed deep basin, which
applies to site 203 in Big Deep Lake (Table 3). This small
deep hole stratifies very strongly as there is not much
surface area for wind mixing.
14
15
16
The hypolimnion does not get depleted of oxygen, which is
good habitat for cold water fish.
16.5
Figure 7. Dissolved oxygen profile
for Big Deep Lake in 2002 at site 203.
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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).
The transparency TSI for Big Deep Lake falls into the
oligotrophic range (Figure 8, Table 5).
Oligotrophic lakes (TSI 0-39) are characteristic of
extremely clear water throughout the summer and sandy
or rocky shores. They are excellent for
recreation. Some very deep oligotrophic
Big Deep
lakes are able to support a trout fishery
Lake
(Table 6).
Table 5. Trophic State Index for Big Deep Lake.
Trophic State Index Site 205
TSI Total Phosphorus NA
TSI Chlorophyll-a
NA
TSI Secchi
35
Oligotrophic
Trophic State:
Numbers represent the mean TSI for each
parameter.
100
Hypereutrophic
70
Eutrophic
50
Mesotrophic
40
Oligotrophic
0
Figure 8. Trophic state index chart with
corresponding trophic status.
Table 6. 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.
Big Deep Lake only had enough data to perform a trend analysis for transparency; however, there
is a data gap between 2002 and 2005 (Table 7, Figure 9). The data was analyzed using the Mann
Kendall Trend Analysis.
Table 7. Trend analysis for Big Deep Lake.
Lake Site
Parameter
Date Range
Trend
203
Transparency
1998-2002, 2005-2011
No trend
201
Transparency
1998-2002, 2005-2011
No trend
Transparency Trend for Big Deep Lake
30
Secchi Depth (ft)
25
20
15
10
5
0
Figure 9. Transparency (ft) trend for site 202 from 1998-2002, 2005-2011.
Even though the graph looks like the transparency is increasing (Figure 9), there is no significant
statistical trend in transparency for Big Deep Lake. Since 2005, the transparency has been higher
than it was in the 1990s. 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. 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.
Big Deep Lake is in the
Northern Lakes and Forests
Ecoregion (Figure 10). The
mean transparency (Secchi
depth) for Big Deep is better
than the ecoregion ranges
(Figure 11).
Figure 10. Minnesota Ecoregions.
0
Secchi depth (ft)
5
10
increased
algae
15
20
25
30
crystal
clear
NLF
Ecoregion
Big Deep
Figures 11a-c. Big Deep Lake ranges compared to
Northern Lakes and Forests Ecoregion ranges. The Big
Deep Lake secchi depth range is from 133 data points
collected in May-September from 1998–2011.
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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 Leech Lake River Major Watershed is one of the watersheds that make up the Upper
Mississippi River Basin, which drains south to the Gulf of Mexico (Figure 12). This major
watershed is made up of 75 minor watersheds. Big Deep Lake is located in minor watershed
8058 (Figure 13).
Figure 12. Leech Lake River Major Watershed.
Figure 13. Minor Watershed 8058
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 Deep
Lake falls within lakeshed
0805801 (Figure 14).
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 Figure 14. Big Deep Lake lakeshed (0805801) with land ownership, lakes,
wetlands, and rivers illustrated.
upstream lakesheds
draining into them, others
may be connected to a large number of lakesheds, reflecting a larger drainage area via stream or
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river networks. For further discussion of Big Deep Lake’s full watershed, containing all the
lakesheds upstream of the Big Deep Lake lakeshed, see page 17. The data interpretation of the
Big Deep Lake lakeshed includes only the immediate lakeshed as this area is the land surface that
flows directly into Big Deep Lake.
The lakeshed vitals table identifies where to focus organizational and management efforts for each
lake (Table 8). 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 8. Big Deep 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
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
535 acres
48 acres
69 ft.
NA
NA
4.0
2
1
8 - Leech Lake River
8058
0805801
Northern Lakes and Forests
descriptive
descriptive
descriptive
NA
NA
descriptive
descriptive
descriptive
descriptive
descriptive
12:1
86:1
14%
None as of 2011
None
None
5.0
1.5
1.7:1
Recreational Development
3.7
None
Yes, Included in Cass County Forest Plan,
2010-2019
None
Individual Waste Treatment Systems, no
county-wide inspection completed
None
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
land’s ability to absorb
and store water rather
Figure 15. Big Deep Lake lakeshed (0805801) land cover (http://land.umn.edu).
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.
Phosphorus export, which is the main cause of lake eutrophication, depends on the type of land
cover occurring in the lakeshed. Figure 15 depicts the land cover in Big Deep Lake’s lakeshed.
The University of Minnesota has online records of land cover statistics from years 1990 and 2000
(http://land.umn.edu). Although this data is 11 years old, it is the only data set that is comparable
over a decade’s time. Table 9 describes Big Deep 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 for Big Deep Lake was
the decrease in grass/shrub/wetland and agriculture cover (25% each). .
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Table 9. Big Deep Lake’s lakeshed land cover statistics and % change from 1990 to 2000
(http://land.umn.edu).
1990
2000
% Change
Land Cover
Acres
Percent
Acres
Percent
1990 to 2000
264
4.22
197
3.15
25.4% Decrease
Agriculture
4113
65.67
4524
72.23
9.9% Increase
Forest
1066
17.02
796
12.71
25.3% Decrease
Grass/Shrub/Wetland
750
11.98
672
10.73
10.4% Decrease
Water
74
1.18
78
1.25
5.4% 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)
6213
17
16
8
5
1
0
99.27
0.27
0.26
0.13
0.08
0.02
0
6213
12
13
12
7
1
2
99.27
0.19
0.21
0.19
0.11
0.02
0.03
No Change
29.4% Decrease
18.8% Decrease
50% Increase
40% Increase
No Change
0.03% Increase
6263
9
0.16
6263
12
0.21
33.3% Increase
Demographics
Big Deep 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 Cass County as a
whole, Woodrow Township has a higher extrapolated growth projection (Figure 16).
(source:http://www.demography.state.mn.us/resource.html?Id=19332)
Population Growth Projection
45%
Percentage of 2006 Population
Figure 16.
Population growth
projection for
Woodrow
Township and
Cass County.
40%
Woodrow Township; 2006 population: 706
35%
Cass County; 2006 population: 28,949
30%
25%
20%
15%
10%
5%
0%
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2006
2010
2015
2020
2025
2030
2035
Extrapolation
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Big Deep Lake 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 privately-owned land within Big Deep Lake’s lakeshed is forested uplands
(Table 10). This land can be the focus of development and protection efforts in the lakeshed.
Table 10. Land ownership, land use/land cover, estimated phosphorus loading, and ideas for protection and
restoration in Big Deep lakeshed (Sources: Douglas County parcel data, National Wetlands Inventory, and
the 2006 National Land Cover Dataset).
11%
Private (33%)
Land Use (%)
Runoff
Coefficient
Lbs of
phosphorus/acre/year
Estimated
Phosphorus
Loading
Public (56%)
Developed
Agriculture
Forested
Uplands
1
2.5
20.5
0.45–1.5
0.26–0.9
0.09
0.09
0.09
0.09
0.09
23–75
41–140
114
28
1.7
313
0
Cropland
Focus of
development and
protection
efforts
State
Forest
National
Forest
Other
4
Wetlands
Open
Water
County
State
Federal
5
11
0.3
55.7
0
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 11). 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 11. Suggested approaches for watershed protection and restoration of DNR-managed fish lakes in
Minnesota.
Watershed
Watershed
Management
Disturbance
Protected
Comments
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.
Big Deep Lake’s lakeshed is classified with having 64.6% of the watershed protected and 4.0% of
the watershed disturbed (Figure 17). Therefore, this lakeshed should have a protection focus.
Goals for the lake should be to limit any increase in disturbed land use. Figure 18 displays the
upstream lakesheds that contribute water to the lakeshed of interest. All of the land and water
area in this figure has the potential to contribute water to Big Deep Lake, whether through direct
overland flow or through a creek or river. Three of the 12 upstream lakesheds have a
management focus of vigilance.
Percent of the Watershed Protected
0%
75%
100%
Big Deep Lake
(64.6%)
Percent of the Watershed with Disturbed Land Cover
0%
25%
100%
Big Deep Lake
(4.0%)
Figure 17. Big Deep Lake’s lakeshed percentage
of watershed protected and disturbed.
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Figure 18. Upstream lakesheds that contribute water
to the Big Deep lakeshed. Color-coded based on
management focus (Table 11).
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Conservation Easement Potential
In an ever-growing society, today’s landscapes are being urbanized more and more to sustain the
ever-growing population and behavior of recreational usage. In Minnesota, the land of ten
thousand lakes, it is only natural to develop properties within the boundaries and beauty of our
lakes and streams. Conservation efforts to limit or slow down the development process can only
assist in the preservation of the lakeshed and inevitably the water quality of water bodies found
within. Figure 19 identifies parcels within the lakeshed that are large enough to warrant the
investigation of parcel conservation practices and purchase.
Figure 19. Lake parcels with conservation potential (developed by John Snyder, LLAWF)
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Status of the Fishery (DNR, as of 08/14/1995)
Big Deep Lake is a 484 acre lake with a maximum depth of 107 feet. It is located six miles east of
Hackensack in northern Cass County. The Minnesota Department of Natural Resources (DNR) has
classified Minnesota's lakes into 43 different types, based on physical, chemical, and other
characteristics. Big Deep Lake is in Lake Class 23. Other area lakes in this same class include
Baby (located two miles north of Big Deep Lake), Deep Portage (located six miles northeast of
Backus), Hay (located ten miles northeast of Backus), and Stony (located two miles northeast of
Hackensack) Lakes. There is no public access on the lake and the only resort is on the north side
of lake.
An abundant northern pike population exists in Big Deep Lake. The average-size of sampled
northern pike was 17.0 inches and weighed 1.3 pounds. Some northern pike larger than 28 inches
were sampled. Growth was slow when compared to other area class 23 lakes.
Walleye were sampled at a rate typical of other area class 23 lakes. The average-size of sampled
walleye was 19 inches and weighed 2.7 pounds. It appears that some portion of the walleye
population is immigrating from other lakes by way of the Boy River. Sampled walleye were growing
at a good rate when compared to class 23 lakes.
The bluegill that were sampled showed good quality with 19% of the sample larger than 7 inches.
Quality has declined since 1972 when it was reported that 61% of the sample was larger than 7
inches. The growth rate for bluegill was slow. Six inch bluegill averaged eight years old.
As in previous years, low numbers of black crappie and largemouth bass were sampled. Summer
netting often does not sample these species relative to their abundance.
Other fish sampled include yellow perch, pumpkinseed, rock bass, yellow bullhead, brown
bullhead, black bullhead, and white sucker. Muskellunge have also been reported in Big Deep.
To help maintain quality fish populations in Big Deep Lake, lake users should safeguard aquatic
habitat by preserving or reestablishing aquatic plants and natural shorelines. Aquatic and terrestrial
plants provide food and cover for fish and wildlife. They also help protect shorelines from erosion,
and absorb nutrients and pollutants. Natural shorelines, shorelines that have not been altered by
man, help protect a lake from silt-laden runoff water. They also provide excellent places for wildlife
to feed, hide, and raise their young. Protection of the larger watershed that drains into Big Deep
Lake is also needed for maintaining water quality.
Anglers can help maintain or improve the quality fishing by practicing catch and release of medium
to large-sized fish. Releasing these fish will help maintain the quality of the fish population and
provide anglers with more opportunities to catch mor large fish in the future.
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=11027700
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Key Findings / Recommendations
Monitoring Recommendations
Transparency monitoring at sites 202, 203 and 204 should be continued annually, with 203 being
the highest priority. 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 should be monitored for at least two years to get enough data for a Minnesota
Pollution Control Agency assessment.
Overall Summary
Big Deep Lake is a very high quality water resource. It is in good shape for water quality and
lakeshed protection. Big Deep is an oligotrophic lake (TSI=35) with no detectable trends in water
quality. Fifty-six percent (56%) of the lakeshed is in public ownership, and 65% of the lakeshed is
protected, while 4% of the lakeshed is disturbed (Figure 17).
Big Deep Lake is an interesting lake limnologically, in that it is relatively small, but very deep.
Because of these qualities, it stratifies very strongly in the summer as there is not much surface
area for wind mixing. It also shows interesting oxygen dynamics, as the oxygen is highest in the
middle of the water column (Figure 7). In addition, the bottom of the lake stays pretty well
oxygenated in the summer, which is good for fish communities.
There was a large improvement in transparency between 2002 and 2005, but there is no data in
between that timeframe to show what happened. It could be related to lake water levels, but the
DNR shows no water level data for Big Deep Lake.
Priority Impacts to the lake
The priority impacts to Big Deep Lake include development, forestry and a large watershed. The
first tier around the lake is mostly developed, except for the publicly-owned southern shore (Figure
15). The development has not changed much from 1990-2000 (Table 10). If the second tier gets
developed, it could significantly change the drainage to the lake.
The forestry around the lake is managed by Cass County. It is important that trees are not clearcut near the shoreline of the lake.
Big Deep Lake has a fairly large watershed with the city of Hackensack in it. The upstream lakes
currently have good water quality. Stream buffers along the Boy River and runoff retention
upstream in the watershed will help protect Big Deep Lake’s water quality.
Best Management Practices Recommendations
The management focus for Big Deep Lake should be to protect the current water quality and the
lakeshed. Efforts should be focused on managing and/or decreasing the impact caused by
additional development, including second tier 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.
Stream buffers along the Boy River and runoff retention upstream in the watershed will help protect
Big Deep Lake’s water quality.
There are numerous large parcels of land that could be protected with conservation easements.
See Figure 19 for the location of these parcels.
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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 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
Organizational Contacts and Reference Sites
Big Deep Lake Property Owners
Association
http://www.bigdeeplake.com
Cass County Soil and Water
Conservation District
Courthouse, 1st Floor, 303 Minnesota Avenue W, PO Box 3000,
Walker, MN, 56484-3000
218-547-7399
http://www.co.cass.mn.us/soil_conservation/soil_water.html
DNR Fisheries Office
07316 State 371 Northwest, Walker, MN, 56484
218-547-1683
[email protected]
Regional Minnesota Pollution Control
Agency Office
7678 College Road, Suite 105, Baxter, MN 56425
218-828-2492, 1-800-657-3864
http://www.pca.state.mn.us/pyri3df
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