Long Lake

East Otter Tail County Water Quality Factsheet
Series
Long Lake
Vitals
MN Lake ID:
Zoning Authority:
Lake Classification:
Major Drainage Basin:
Latitude/Longitude:
Water Body Type:
Invasive Species:
DNR ID: 56-0388-02
56-0388-02
The City of Vergas
Drainage Lake
Red River
46.65191667/-95.77475000
Public
None
Physical Characteristics
Surface area (acres):
Littoral area (acres):
% Littoral area:
Max depth (ft):
Mean depth (ft):
Inlets/Outlets/Accesses:
Lakeshed to lake area ratio:
1,289
529
41%
128
31
3/1/2
6:1
Total Phosphorus
Long Lake is phosphorus limited, which means that algae
and aquatic plant growth is dependent upon available
phosphorus. Total phosphorus was evaluated in Long Lake
from 1996-1998, 2001-2003, 2007, and 2009-2011. These
data do not indicate much seasonal variability. The majority
of the data points are in the mesotrophic range, although
early season data (mostly May) are in the eutrophic range.
This could be attributed to spring thaw and rains in the
watershed. Total phosphorus has no trend.
Chlorophyll a
Chlorophyll a is the pigment that makes plants and algae
green. It is tested in lakes to determine the algae
concentration or how green the water is. Chlorophyll a
Long Lake total phosphorus, chlorophyll a, and transparency historical ranges.
concentrations greater than 10 ug/L are perceived as a mild
The arrow represents the range and the black dot represents the historical mean
algae bloom, while concentrations greater than 20 ug/L are
(Primary Site 206). Figure adapted after Moore and Thornton, [Ed.]. 1988. Lake
and Reservoir Restoration Guidance Manual. (Doc. No. EPA 440/5-88-002)
perceived as a nuisance. Chlorophyll a was evaluated on
Long Lake in from 1996-1998, 2001-2003, 2007, and 20092011. Concentrations reached 10 ug/L, most years,
indicating major algae blooms. Chlorophyll a concentrations had no trend.
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, therefore they are only
found 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 annual mean transparency for Long Lake ranges from 0.2 to 10 feet, and appears
Long Lake
relatively uniform throughout the lake. Transparency on the lake has no trend.
100
Hypereutrophic
70
Eutrophic
50
Mesotrophic
40
Trophic State Index (TSI)
Phosphorus (nutrients), chlorophyll a (algae concentration), and Secchi depth (transparency) are
interrelated. As phosphorus increases, there is more food available for algae, resulting in increased
Oligotrophic
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 or averaged. In order to standardize these
0
measurements to make them directly comparable, we convert them to a tropic state index (TSI).
The mean TSI for Long Lake is 49; falling on the mesotrophic/eutrophic border (TSI 49-51) which is characterized by moderately
clear water for most of the summer. “Meso” means middle or mid; therefore, mesotrophic means a medium amount of
productivity. If the water quality becomes more eutrophic the lake will start to have extended periods of green water.
Local association information: The Vergas-Long Lake Association
Long Lake
56-0388-02 OTTERTAIL COUNTY
Lake Water Quality
Summary
Long Lake is located on the northeast side of Vergas,
MN in Otter Tail County. The lake has an elongated
shape that is oriented roughly west-east, and covers
1,289 acres.
Long Lake has three inlets and one outlet, which
classify it as a drainage lake. The inlet on the north
side of the lake, near the narrows, receives water from
Rose Lake. The two additional inlets are located along the south shore of the eastern basin. The
outlet is located on the east shore of the lake. Water moving out of the lake flows about a quarter of a
mile before joining the Otter Tail River system.
Water quality data have been collected on Long Lake in 1985-1992 and 1996-2011. These data show
that the lake is at the mesotrophic/eutrophic border (TSI 49-51), with characteristic clear water in the
summer and good recreational opportunities (page 9).
The Vergas-Long Lake Association was organized in 1996. The purpose of the Vergas-Long Lake
Association is to represent and protect the interests of the residents and property owners on the lake.
The Association “seeks to protect the ecology of the lake and the surrounding area, the preservation
of the natural beauty of the lake and surrounding area, and the promotion of safe boating, swimming,
and recreational opportunities and activities for all residents and guests.”
Table 1. Long Lake location and key physical characteristics.
Location Data
Physical Characteristics
MN Lake ID:
56-0388-02
Surface area (acres):
1289
County:
Otter Tail
Littoral area (acres):
529
41%
Ecoregion:
Northern Central Hardwood
Forests
% Littoral area:
Max depth (ft), (m):
128
Major Drainage Basin:
Red River
Inlets:
3
Latitude/Longitude:
46.65191667 / -95.77475000
Outlets:
1
Invasive Species:
None
Public Accesses:
2
Table 2. Availability of primary data types for Long Lake.
Data Availability
Transparency data
Excellent continuous data from site 202. Several new sites
starting recording readings in 2011.
Chemical data
Good data set from site 202.
Inlet/Outlet data
No inlet or outlet data
Recommendations
For recommendations refer to page 18.
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Lake Map
Figure 1. Map of Long Lake with 2010 aerial imagery and illustrations of lake depth contour lines, 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. Programs include Minnesota Pollution Control
Agnecy Lake Monitoring Program (MPCA), Citizen Lake Monitoring Program (CLMP), and RMB Environmental
Laboratories Monitoring Program (RMBELMP).
Lake Site
Depth
(ft)
Monitoring Programs
101
102
104
201
202
50
30
60
25
95
203
204
125
100
MPCA: 1999; CLMP: 2011
MPCA: 1999; CLMP: 2011
MPCA: 1999
CLMP: 1985-1992, 1994; RMBELMP: 2000, 2004-2006
MPCA: 1999; RMBELMP: 1996-1998, 2001-2004, 2006, 2007, 2009-2011;
CLMP: 1998-2010
CLMP: 2011
CLMP: 2011
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Average Water Quality Statistics
The information below describes available chemical data for the primary site (202) of Long 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 1999 data.
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
10.
Table 4. Water quality means compared to ecoregion ranges and impaired waters standard.
Impaired
Waters
Standard2
Parameter
Mean
Ecoregion
Range1
Total phosphorus (ug/L)
25
23 - 50
> 35
3
8
5 - 22
> 12
Chlorophyll a max (ug/L)
19
7 - 37
Secchi depth (ft)
9.2
4.9 – 10.5
Dissolved oxygen
Dimitic
Chlorophyll a (ug/L)
Interpretation
Results are within the expected
range for the ecoregion. For
more information about
Impaired Waters Assessment,
see page 12.
< 4.5
Dissolved oxygen depth profiles
show that the deep areas of the
lake are anoxic in late summer.
See page 9
0.6
< 0.60 – 1.2
Indicates insufficient nitrogen to
support summer nitrogeninduced algae blooms.
Alkalinity (mg/L)
157
75 - 150
Indicates a low sensitivity to
acid rain and a good buffering
capacity.
Color (Pt-Co Units)
5
10 - 20
Indicates clear water with little
to no tannins (brown stain).
pH
n/a
8.6 – 8.8
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.
Chloride (mg/L)
9.4
4 - 10
Within the expected range for
the ecoregion.
Total Suspended Solids
3.6
2-6
Indicates low suspended solids
and clear water.
Conductivity (umhos/cm)
n/a
300 - 400
Within the expected range for
the ecoregion.
Total Nitrogen :Total
Phosphorus
41:1
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 Kjeldahl Nitrogen
(mg/L)
(mg/L)
Not available (n/a)
1
The ecoregion range is the 25th-75th percentile of summer means from ecoregion reference lakes
2
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)
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Water Quality Characteristics - Historical Means and Ranges
Table 5. Water quality means and ranges for primary sites. Years monitored: 1976, 1986-2008.
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:
Primary
Site
202
201
25
10
61
54
8
<1
19
54
9.2
4.5
19.0
152
24
12
47
18
9
2
22
18
10.0
5.0
20.0
76
Figure 2. Long Lake total phosphorus, chlorophyll a, and transparency historical ranges. The arrow
represents the range and the black dot represents the historical mean (Primary Site 202). 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 found 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.
For all the sites that had more than 20 transparency data points, the mean transparency ranges from
0.2 to 10.0 feet. The transparency throughout the lake appears to be relatively uniform. The annual
means remained near the long-term mean for the primary site (202). Transparency monitoring should
be continued annually at sites 203 and 205 in order to track water quality changes.
18
Transparency: Annual Means
16
Secchi Depth (ft)
14
12
10
8
6
Site 201
4
Site 202
2
Long-term Mean, Site 202
0
Figure 3. Annual mean transparency compared to long-term mean transparency, sites 201 and 202.
Long Lake transparency ranges from 4.5 to 19.0 ft at the primary site (202). Figure 4 shows the
seasonal transparency dynamics. The maximum Secchi reading is usually obtained in early summer,
with high transparency in May and June, and declining through August. The transparency then
rebounds in October after fall turnover. This visibility dynamic is typical of a northern Minnesota lake,
and is influenced by algae and zooplankton populations, 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 visibility is lower in August than it is in June. It is typical for a
lake to vary throughout the summer.
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Seasonal Transparency Dynamics
20
18
Secchi Depth (ft)
16
14
12
10
8
6
4
2
0
1996
1997
1998
1999
2000
2001
2002
2003
2004
2005
2006
2007
2008
2009
2010
2011
Poly. (Pattern)
Figure 4. Seasonal transparency dynamics and year to year comparison (Primary Site 202). The dark gray line
represents the seasonal pattern of the data.
User Perceptions
When volunteers collect Secchi depth readings, they record their observations of the water based on
the physical appearance and 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. Long Lake was rated as being not quite crystal clear 51% of the time between
1998, 1999, and 2006-2011 (site 202). The one result of severely high algae was on April 23, 2006.
5% 1%
Physical Appearance Rating
6%
37%
51%
6%
Crystal clear water
51%
Not quite crystal clear – a little algae visible
34%
Definite algae – green, yellow, or brown color
apparent
5%
High algae levels with limited clarity and/or mild
odor apparent
1%
Severely high algae levels
Figure 5. Physical appearance rating, as rated by the volunteer monitor from 1998, 1999, and 2006-2011.
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As the Secchi depth decreases, the perception of recreational suitability of the lake decreases. Long
Lake was rated as being beautiful 19% of the time from 1998, 1999, and 2006-2011 (site 202).
Recreational Suitability Rating
9%
19%
32%
40%
19%
Beautiful, could not be better
40%
Very minor aesthetic problems; excellent for
swimming, boating
32%
Swimming and aesthetic enjoyment of the lake
slightly impaired because of algae levels
9%
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 1998, 1999, and 2006-2011.
Total Phosphorus
Total Phosphorus
1996
70
Total Phosphorus (ug/L)
Long Lake is
phosphorus limited,
which means that
algae and aquatic
plant growth is
dependent upon its
availability.
1997
1998
60
1999
50
2001
40
Total phosphorus was
evaluated in Long
30
Lake in 1996-1998,
Eutrophic
2001-2003, 2007, and
20
2009-2011. The data
Mesotrophic
do not indicate great
10
seasonal variability.
Most of the data falls
Oligotrophic
within the mesotrophic
0
range, though early
season data (mostly
May) are in the
Figure 7. Historical total phosphorus concentrations (ug/L) for Long Lake.
eutrophic range.
This could be due to
spring thaw and
rains in the watershed.
2002
2003
2007
2009
2010
2011
Phosphorus should continue to be monitored to track any future changes in water quality.
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Chlorophyll a
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.
Chlorophyll a
25
1996
1997
1998
20
Chlorophyll a (ug/L)
Chlorophyll a is the pigment
that makes plants and algae
green. It is tested in lakes to
determine the algae
concentration or how green
the water is.
1999
2001
15
2002
2003
10
2007
2009
5
2010
2011
0
Chlorophyll a was evaluated
in Long Lake in 1996-1999,
2001-2003, 2007, and
2009-2011. Concentrations
Figure 8. Chlorophyll a concentrations (ug/L) for Long Lake.
reached 10 ug/L in most
years, indicating minor algae blooms.
Minor Algae
Nuisance Algae
Dissolved Oxygen
0
Dissolved Oxygen (mg/L)
5
10
Depth (ft)
0
3
6
9
12
15
18
21
24
27
30
33
36
39
42
45
48
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.
Long Lake is a deep lake, with a maximum depth of 128
feet. Dissolved oxygen and temperature profiles from
2011 show that the lake stratifies in the summer, with the
thermocline resides at approximately 27 feet. Below that
depth, the oxygen declines, but not much below 5 ug/L,
indicating that fish may be present below that depth. This
is also great cisco (tullibee) fish habitat. Long Lake is
designated by the DNR as a cisco refuge lake. For more
about this designation see page 17.
Figure 9. Dissolved oxygen and temperature
profile for Long Lake on 6/22/2011.
0
20
40
60
80
Temperature (F)
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Trophic State Index
Table 6. Trophic State Index for site 202.
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.
Trophic State Index
Site 202
Site 201
TSI Total Phosphorus 51
50
TSI Chlorophyll-a
51
52
TSI Secchi
45
44
TSI Mean
49
49
Mesotrophic/Eutrophic
Trophic State:
Numbers represent the mean TSI for each parameter.
The results from these three measurements
cover different units and ranges and thus cannot be
directly compared or averaged. In order to standardize
these three measurements to make them directly
comparable, we convert them to a trophic state index
(TSI).
100
Hypereutrophic
70
The mean TSI for the two main sites of Long
Lake fall on the border between mesotrophic
Long Lake
and eutrophic (49-51). There is fairly good
agreement between the TSI for phosphorus,
chlorophyll a, and transparency, indicating
that these variables are related. The transparency TSI is
slightly lower than the chlorophyll a TSI. This could be
due to zooplankton grazing on the smaller algae cells,
large algae particles dominate the algal community, or
loss of rooted vegetation.
Lakes on the mesotrophic to eutrophic border (TSI 4951) are characterized by moderately clear water most of
the summer. "Meso" means middle or mid; therefore,
mesotrophic means a medium amount of productivity. If
the water quality becomes more eutrophic the water will
start to have extended periods of green water.
Eutrophic
50
Mesotrophic
40
Oligotrophic
0
Figure 10. Trophic state index chart with
corresponding trophic status.
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.
There is enough historical data to perform trend analysis for total phosphorus, chlorophyll a, and
transparency on Long Lake (Table 8, Figure 11). Site 202 had over 8 years of data, which was
enough data to perform a long-term trend analysis using the Mann Kendall Trend Analysis.
Table 8. Trend analysis for Long Lake.
Lake Site
Parameter
Date Range
Trend
Probability
202
Transparency
1996-2011
No Trend
--
202
Total Phosphorus
1996-1999, 2001-2004,
2006, 2006, 2009-2011
No Trend
--
202
Chlorophyll a
1996-1999, 2001-2004,
2006, 2006, 2009-2011
No Trend
--
Long Lake Transparency Trend
20
18
Secchi Depth (ft)
16
14
12
10
8
6
4
2
0
Figure 11. Transparency (ft) trend for site 202 from 1996-2011
Site 202 showed no significant trends for any of the analyzed parameters. Visually, it appears the
transparency may be declining. Transparency monitoring should continue so that any developing
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 water quality for reference lakes.
These water bodies are not considered pristine, but
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.
Long Lake is in the Central
Hardwood Forest Ecoregion.
The mean total phosphorus,
chlorophyll a, and
transparency (Secchi depth)
for Long Lake are all within
the expected ecoregion
ranges.
Figure 12. Minnesota Ecoregions.
70
120
0
2
60
4
50
60
40
6
Secchi depth (ft)
80
Chlorophyll-a (ppb)
Total Phosphorus (ppb)
100
40
30
increased
algae
8
10
12
14
20
16
20
10
crystal
clear
18
0
0
CHF
Ecoregion
Long
20
CHF
Ecoregion
Long
CHF
Ecoregion
Long
Figures 13a-c. Long Lake ranges compared to Central Hardwood Forest Ecoregion ranges. The Long Lake
total phosphorus and chlorophyll a ranges are from 52 data points collected in May-September of 1996-1999,
2001-2004, 2006, 2006, and 2009-2011. The Long Lake Secchi depth range is from 152 data points collected
in May-September from 1996-2011.
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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 Otter Tail River Major Watershed is one of the watersheds that make up the Red River Basin,
which drains north to Lake Winnipeg (Figure 14). This major watershed is made up of 106 minor
watersheds. Long Lake is located in minor watershed 56022 (Figure 15).
Figure 14. Otter Tail River 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.
Long Lake falls within
lakeshed 5602201 (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 many, reflecting
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Figure 15. Minor Watershed 56022.
Figure 16. Long Lakeshed (5602201) with land ownership, lakes, county
lines, and wetlands illustrated.
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2011 Long Lake
a larger drainage area via stream or river networks. For further discussion of Long Lake’s full
watershed, containing all the upstream lakesheds, see page 17. The data interpretation of the Long
lakeshed includes only the land surface that flows directly into the lake.
The lakeshed vitals table identifies where to focus organizational and management efforts for each
lake. 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. Long Lake lakeshed vitals table.
Lakeshed Vitals
Rating
Lake Area
Littoral Zone Area
Lake Max Depth
1289 acres
551 acres
128 feet
Lake Mean Depth
Water Residence Time
Miles of Stream
Inlets
Outlets
Major Watershed
31
NA
1.5
3
1
56 – Otter Tail River
Minor Watershed
Lakeshed
Ecoregion
Total Lakeshed to Lake Area Ratio (total
56022
5602201
North Central Hardwood Forests
lakeshed includes lake area)
Standard Watershed to Lake Basin Ratio
(standard watershed includes lake areas)
Public Lake Accesses
Miles of Shoreline
Shoreline Development Index
Public Land to Private Land Ratio
Development Classification
Miles of Road
2
12.16
2.4
0.03:1
Recreational Development
19.4
Municipalities in lakeshed
Forestry Practices
Feedlots
Vergas
No county forest plan
8
Individual Waste Treatment Systems (last
county-wide inspection in 2004)
None
None
RMB Environmental Laboratories, Inc.
descriptive
descriptive
descriptive
descriptive
25:1
5.4%
None as of 2011
None
Lake Management Plan
Lake Vegetation Survey/Plan
NA
descriptive
6:1
Wetland Coverage
Aquatic Invasive Species
Public Drainage Ditches
Sewage Management
descriptive
descriptive
descriptive
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Land Cover / Land Use
The activities that occur within
the lakeshed can greatly impact
a lake. Land use planning helps
ensure the use of resources in
an organized fashion so the
needs of the present and future
generations can be best
addressed. The purpose of land
use planning is to ensure
acreage 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. Cover
is 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
on the landscape. Impervious
intensity describes the lands
inability to absorb water, the
Figure 17. Long lakeshed (5602201) land cover
higher the % impervious intensity the
(http://land.umn.edu).
more area that water cannot
penetrate into the soil. Monitoring the changes in land use can assist in future planning procedures to
address the needs of future generations.
Phosphorus export, the main cause of lake eutrophication, depends on the type of land cover
occurring in the lakeshed. Figure 17 depicts the land cover in Long 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 available to compare
over a decade of time. Table 10 describes Long 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 and grass/shrub/wetland, to forest and urban acreages.
The largest change in percentage is the decrease in agriculture cover (57.8%). 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. Long 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
Agriculture
4671
66.28
4467
63.39
4.4% Decrease
Grass/Shrub/Wetland
274
3.89
209
2.97
23.7% Decrease
Forest
589
8.36
752
10.67
27.7% Increase
Water
1282
18.19
1253
17.78
2.3% Decrease
Urban
232
3.29
366
5.19
57.8% Increase
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)
6847
33
56
51
41
11
7
97.16
0.47
0.79
0.72
0.58
0.16
0.1
6732
23
51
63
93
54
30
95.53
0.33
0.72
0.89
1.32
0.77
0.43
1.7% Decrease
30.3% Decrease
8.9% Decrease
23.5% Increase
126.8% Increase
390.9% Increase
328.6% Increase
7047
63
1.09
7047
143
2.47
127% Increase
Demographics
Long Lake is classified as a recreational
development lake. This type of lake usually has 60225 acres of water per mile of shoreline, 3-25
dwellings per mile of shoreline, and is more than 15
feet deep.
The Minnesota Department of Administration
Geographic and Demographic Analysis Division
has extrapolated the future population of the area,
in 5-year increments, out to 2035. Compared to Otter Tail County as a whole, Hobart Township has a
higher extrapolated growth projection, whereas the City of Vergas has a much lower growth projection
(Figure 18).
Figure 18. Population growth
projection for Hobart Township and
City of Vergas and Otter Tail
County. (source:
http://www.demography.state.mn.us/
resource.html?Id=19332)
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2011 Long Lake
Long Lake Lakeshed Water Quality Protection Strategy
Each lakeshed has a unique combination 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, and 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 use within Long lakeshed is agricultural (Table 11). This land can be the
focus of development and protection efforts in the lakeshed.
Table 11. Percent land use in private versus publicly owned land with corresponding phosphorus loading and
protection/restoration idea (Sources: Otter Tail County Parcel Data, National Wetlands Inventory, and the 2006
National Land Cover Dataset).
Private (78%)
Land Use (%)
19%
Public (3%)
Developed
Agriculture
Forested
Uplands
Other
Wetlands
Open
Water
County
State
Federal
4.1%
47.1%
18.2%
3.8%
4.8%
19%
2.9%
0.1%
0%
0.45 - 1.5
0.26 - 0.9
0.09
0.09
0.09
0.09
0.09
130–435
862–2985
115
31
16
<1
0
Cropland
Focus of
development and
protection
efforts
State
Forest
National
Forest
Runoff
Coefficient
Lbs of
phosphorus/acre/
year
Estimated
Phosphorus
Loading
Acerage 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 those with more than 25% require 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
Disturbance
Protected
Comments
Type
(%)
(%)
> 75%
Vigilance
< 75%
Protection
25-60%
n/a
Full Restoration
> 60%
n/a
Partial Restoration
< 25%
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%.
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. Lakesheds 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 potential tools that can protect
these high-value resources for the long term.
Long Lake is classified with having 21.4% of the watershed protected and 54.1% disturbed (Figure
19), therefore, it should have a full restoration focus. Goals for the lake should limit any increase in
disturbed land use. The main bay of Long Lake was designated by DNR Fisheries as a high valued
fishery lake because of its cisco population.
Figure 20 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 Long Lake, whether through
direct overland flow or a creek or river. Seven of the 12 upstream lakesheds have the same
management focus (full restoration).
Percent of the Watershed Protected
0%
75%
100%
Long Lake
(21.4%)
Percent of the Watershed with Disturbed Land Cover
0%
25%
100%
Long Lake
(54.1%)
Figure 20. Long lakeshed’s percentage of watershed
protected and disturbed.
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Figure 21. Upstream lakesheds that contribute water
to the Long lakeshed. Color-coded based on
management focus (Table 12).
2011 Long Lake
Long Lake, Status of the Fishery (as of 06/16/2003)
Long Lake is a 1,273 lake located in north-central Otter Tail County. The southwest shoreline of
the lake abuts the city of Vergas, MN. The lake is composed of two distinct basins; the west basin
is characteristic of an oligotrophic lake (deep and unfertile), while the east basin is characteristic of
a mesotrophic lake (moderately deep and fertile). Several intermittent inlets are located along the
north and south shorelines of the lake. An outlet to the Otter Tail River is located along the east
shoreline of the lake. These inlets and outlet are not navigable by boat.
The immediate watershed is composed primarily of agricultural land interspersed with hardwood
woodlots. The maximum depth of Long Lake is 128 feet; however, 42% of the lake is less than 15
feet in depth. Secchi disk readings have ranged from 8.0 to 14.0 feet. Periodic plankton/algae
blooms throughout the summer months can influence Secchi disk readings.
Long Lake is included in lake class 22 of the MNDNR lake classification scheme. Residential
development is scattered around the entire shoreline of the lake and is approximately 30% of the
shoreline use; this development consists of homes, cottages, and resorts. In reference to the 1995
lake resurvey, there are approximately 96 homes/cottages and four resorts located on Long Lake.
Approximately 40% of the shoreline remains undeveloped mixed hardwoods. A DNR-owned
concrete public water access is located off of Minnesota State Highway 228 along the northwest
shoreline of the lake. A city park is located along the west shoreline of the lake, with a handicap
accessible fishing pier available for public use.
The shoal water substrates consist primarily of sand and gravel. Large stands of hardstem bulrush
and common cattail are prevalent around the shoreline of the lake. These emergent aquatic plants
provide valuable fish and wildlife habitat, and are critical for maintaining good water quality. They
protect shorelines and lake bottoms, absorbing and break down pollutants. Emergent plants
provide spawning areas for fish such as northern pike, largemouth bass, and panfish. They also
serve as important nursery areas for all species of fish. Due to their ecological value, emergent
plants may not be removed without a DNR permit.
Long Lake can be ecologically classified as a bass-panfish-walleye lake; this is reflected in the
assemblage of the fish community. Walleye, northern pike, largemouth bass, and bluegill are the
dominant game species. The prolificacy of these species can be attributed to the abundance of
suitable spawning habitat. The northern pike test-net catch rate exceeded the upper limit of the
normal range for class 22 lakes, with age data indicating reproduction rates are consistently good.
Northern pike ranged in length from 16.8 to 32.1 inches with an average length and weight of 21.6
inches and 2.3 pounds. At four years of age, pike attain an average length of 20.3 inches. Long
Lake is a popular with largemouth bass anglers. Summer test-net indices are not reliable
indicators of largemouth bass abundance or size structure; however, bass were sampled that
ranged in length from 8.8 to 16.2 inches, and angler reports have been positive. The bluegill testnet catch rate exceeded the upper limit of the normal range for class 22 lakes; this is consistent
with previous surveys. Age data indicate that the 1997 year class is very strong, with 18 percent of
the bluegills at 7.0 inches or greater in length. Bluegills attain an average length of 6.7 inches at
seven years of age.
Walleye is a primary management specie in this lake. The test-net catch rate declined after
increasing in five successive surveys. Walleye in this assessment ranged in length from 9.5 to
27.6 inches with an average length and weight of 16.3 inches and 1.8 pounds. Data from recent
test-netting assessments indicate that natural reproduction can be substantial in some years. A
biennial fingerling stocking plan was initiated in 2000, and will be evaluated in future lake surveys
to determine if this stocking sequence and natural reproduction can maintain the walleye
population at or above management goals. Walleye reach an average length of 13.5 inches at four
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years of age. The DNR does not stock any other fish species in Long Lake, as they are able to
sustain population levels at or above management goals without stocking. This is an indication of
excellent water quality and fish habitat. To maintain the excellent fishing, it is imperative to
preserve the water quality and fish habitat. Anglers can help maintain fishing quality by practicing
selective harvest. This management strategy encourages the release of medium to large-size fish,
while allowing the harvest of the more abundant, smaller fish for table fare. Releasing the medium
to large fish will ensure the lake has enough spawning-age fish annually and providing anglers with
more opportunities to catch 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=56038800
Key Findings / Recommendations
Monitoring Recommendations
Transparency monitoring at sites 201 and 202 should be continued annually. It is important to
continue transparency monitoring weekly, or at least bimonthly, every year to enable annual
comparisons and trend analyses.
Priority Impacts to the lake
Long lakeshed is rated as a full restoration due to the potential impacts of agricultural land use
(Figure 17). Beyond the first tier development around the lake, the remaining lakeshed is
predominately wetlands or agriculture. Most of the agricultural land appears to be in a
corn/soybean rotation. There are other miscellaneous crops, including alfalfa and wheat. In some
areas, the fields are within 100 feet of the lakeshore. Agricultural best management practices
should continue and/or be implemented to alleviate impact from this type of land use.
A second impact to Long Lake is development. Roads border the lake in numerous locations,
drastically increasing the amount of impervious surface. In addition, the City of Vergas is partially
located in the lakeshed. Development along the lake shore itself is not dense, however, existing
lakeshore homeowners should be cognoscente of the impact impervious surfaces on their property
have on nutrient and sediment input to the lake.
Best Management Practices Recommendations
Agricultural areas should focus on vegetative filter strips in areas of concentrated flow and field
boards, where crops are in close proximity to the shoreline. Timed application of fertilizer will
ensure utilization by the growing crops and fewer nutrients flowing into groundwater due to
overland runoff.
The management focus for Long Lake should improve the water quality and lakeshed protection.
Restoration 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.
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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)
Lake Associations
Lake condition monitoring
Internal loading monitoring
Ground truthing – visual inspection upstream on stream inlets
Watershed mapping by a consultant
Shoreline inventory study by a consultant
Soil and Water Conservation District (SWCD) and Natural Resources Conservation Service
(NRCS)
Shoreline restoration
Stream buffers
Work with farmers to
o Restore wetlands
o Implement conservation farming practices
o Participate in land retirement programs such as Conservation Reserve Program
Organizational contacts and reference sites
Long Lake Association
No contact information available.
DNR Fisheries Office
1509 1st Avenue North, Fergus Falls, MN 56537
218-739-7576
[email protected]
http://www.dnr.state.mn.us/areas/fisheries/fergusfalls/index.html
Regional Minnesota Pollution
Control Agency Office
714 Lake Ave., Suite 220, Detroit Lakes, MN 56501
218-847-1519, 1-800-657-3864
http://www.pca.state.mn.us/yhiz3e0
Regional Board of Soil and Water
Resources Office
801 Jenny Ave SW Suite 2, Perham, MN 56573
218-346-4260 ext.3
http://www.eotswcd.org/
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Long Lake
Watershed Analysis for Non-Point Water
Quality Projects
This project used computer analysis of new LiDAR elevation
data to determine which areas of the watershed have the
potential to deliver nutrients to Long Lake by surface water
runoff. This analysis does not account for how the land is
currently being used but instead highlights areas where
pollution reducing practices will have a direct benefit to the
lake.
Prepared By: Steve Henry
Otter Tail County Shoreland Specialist
4-14-2012