Washburn Lake - Cass County, Minnesota

Washburn Lake 11-0059-00 CASS COUNTY
Summary
Washburn Lake is located about three miles northwest of the town of Outing in
northern Cass County. It covers 1,590 acres, which places it in the upper 10% of
lakes in Minnesota in terms of size.
Washburn Lake has three distinct basins: a western basin with a maximum depth of
111 feet, a northern basin with a maximum depth of 90 feet, and an eastern basin
with a maximum depth of 25 feet.
Washburn Lake is located near the top of the Pine River Major Watershed. Daggett
Brook flows south from Island and George Lakes into the west basin of Washburn Lake and then
outlets Washburn Lake at the south end. Flow continues south through Daggett Brook, a series of
lakes, and the Pine River that enters the Mississippi River at the south end of the watershed.
Water quality data have been collected on Washburn Lake from 1986-2008. These data show that
the lake is mesotrophic (page 9). Mesotrophic Lakes have clear water most of the summer with
occasional algae blooms.
The mission of Lake Washburn Association is to ensure that the beautiful lake and its environment
will survive to be enjoyed by those generations that follow us. The Association has been involved
in numerous activities including water quality monitoring, education, Healthy Lakes Initiative,
promotion of safety, and is a member of the Association of Cass County Lakes (ACCL).
Vitals
MN Lake ID: 11-0059-00
County:
Cass
Ecoregion:
Northern Lakes and Forest
Major Drainage Basin: Upper Mississippi River
Latitude/Longitude: 46.875/-94.00027778
Water Body Type: Public
Monitored Sites
(Primary):
101, 202, 204, 206
Monitored Sites
(Secondary):
201, 203, 205, 207, 208
Invasive species: none documented
Physical Characteristics
Surface area (acres): 1,590
Littoral area (acres): 748
% Littoral area: 48%
Max depth (ft): 111 (m): 33.8
West Basin: 25.7 (m): 7.8
Mean depth (ft):
East Basin: 4.9 (m): 1.5
Lakeshed area (acres): 7,405
Lakeshed : lake area ratio 4.7:1
Inlets
1 – Daggett Creek
Outlets
1 – Daggett Creek
Accesses
1 public
Data Availability
Transparency data
Chemical data
Inlet/Outlet data
Numerous yearly secchi readings from 1986-2008
through the MPCA CLMP program.
Extensive Phosphorus and Chlorophyll a data have
been collected.
No inlet or outlet data exist for Washburn Lake.
Recommendations For recommendations refer to page 12.
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Figure 1. Map of Washburn Lake illustrating bathymetry, lake sample site locations, stream inlets and outlets
and aerial land use. The pink shaded areas in the lake illustrate the littoral zone, where the sunlight can
usually reach the lake bottom allowing aquatic plants to grow.
Lake Site Depth (ft) Monitoring Programs
101 (3901) 90 CLMP: 2001-2002; MPCA: 2004, 1986; Outdoor Corps: 2004; RMB Lab: 2006-2008
103 60 MPCA: 2004, 1986
201 65 CLMP: 1986-1995, 2003-2007
202 80 CLMP: 1986, 1999, 2001-2002; Outdoor Corps: 2004; RMB Lab: 2005-2008
203 25 CLMP: 1986-2007
204 (104) 20 CLMP: 1986-2008; MPCA: 1986; Outdoor Corps: 2004; RMB Lab: 2005-2008
205 65 CLMP: 1986-2007
206 15 CLMP: 1993-1995, 2003-2008; RMB Lab: 2005-2008
207 22 CLMP: 2000-2007
208 30 CLMP: 2005-2007
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The information below describes available chemical data for Washburn Lake through 2008. The
data set is limited, and all parameters with the exception of total phosphorus, chlorophyll a and
secchi depth are means for just 1986 and 2004 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.
West Bay
Site 101
Mean
North Bay
Site 202
Mean
East Bay
Site 204
Mean
Ecoregion
Parameter
Range 1 Interpretation
Total phosphorus (ug/L) 15.0 12.3 15.8 14 - 27 Results are within the
Chlorophyll a (ug/L) 2 5.3 5.0 4.7 4 - 10 expected range for the
Chlorophyll a max (ug/L) 9 9 14

Water Quality Characteristics - Historical Means
Years monitored: 1986-2008
Parameters
West Basin
Site
101
Site
201
Site
203
North Basin
East
Basin
Total Phosphorus Mean (ug/L): 15.0 13.1 12.3 15.8
Total Phosphorus Min: 6 8 8 9
Total Phosphorus Max: 33 19 20 31
Number of Observations: 28 20 25 33
Chlorophyll a Mean (ug/L): 5.3 5.6 5.0 4.7
Chlorophyll-a Min: 2 2 2.0 1
Chlorophyll-a Max: 9 8 9.0 14
Number of Observations: 28 20 24 32
Secchi Depth Mean (ft): 11.8 13.1 10.2 11.0 12.9 15.3 13.9 14.6 10.8
Secchi Depth Min: 5.9 8.0 4.5 5.5 8.2 10.5 9.0 10.5 6.0
Secchi Depth Max: 17.0 18.5 16.0 17.0 18.5 21.0 19.0 19.0 18.0
Number of Observations: 40 160 310 67 49 286 148 34 405
Site
206
Site
202
Site
205
Site
207
Site
208
Site
204
Figure 2. Washburn Lake total phosphorus, chlorophyll a and transparency historical ranges. The arrow
represents the range and the black dot represents the historical mean (Primary Site 101). 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. Figure 3 shows that in most years, site 205 in the northern basin had
the best transparency and sites 203 and 204 had the lowest transparency. These results make
sense in that sites 203 and 204 are the shallowest sites.
The long-term transparency data set for Washburn Lake is excellent since 1986. Transparency
monitoring should be continued annually at all sites in order to track water quality changes in the
future.
20
Transparency: Annual Means
Secchi Depth (ft)
18
16
14
12
10
8
6
4
2
0
Site 201
Site 203
Site 204
Site 205
Site 207
1986
1988
1990
1992
1994
1996
1998
2000
2002
2004
2006
2008
Figure 3. Annual transparency means for Washburn Lake monitoring sites.
Washburn Lake transparency ranges from 10.5 to 21 ft at site 205. Figure 4 shows the seasonal
transparency dynamics. Washburn Lake transparency is highest in May and then it declines
slightly throughout the rest of the summer. Transparency in some lakes varies throughout the
summer, while in others it stays relatively constant. The transparency dynamics are related to lake
turnover and algae population dynamics.
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Figure 4. Seasonal transparency dynamics and year-to-year comparison (Site 205).
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. The northern basin of Washburn
Lake was rated as having crystal clear water
42% of the time, while the western basin and
eastern basin were 2% and 7% respectively
(Figure 5).
Physical Appearance Rating
Crystal clear water
Not quite crystal clear – a little algae visible
Definite algae – green, yellow, or brown
color apparent
High algae levels with limited clarity and/or
mild odor apparent
Severely high algae levels
4%
2%
7%
2%
27%
42%
56%
94%
66%
Site 201
Western Basin
Site 204
Eastern Basin
Site 205
Northern Basin
Figure 5. Physical appearance rating for all three basins, as rated by the volunteer monitor (1986-2008).
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As the secchi depth decreases,
the perception of recreational
suitability of the lake decreases.
The basins differ somewhat in
rating. The northern basin was
rated as being beautiful 72% of
the time, while the eastern and
western basins were rated as
beautiful 9-10% of the time
(Figure 6).
Recreational Suitability Rating
Beautiful, could not be better
Very minor aesthetic problems; excellent for
swimming, boating
Swimming and aesthetic enjoyment of the lake slightly
impaired because of algae levels
Desire to swim and level of enjoyment of the lake
substantially reduced because of algae levels
Swimming and aesthetic enjoyment of the lake
nearly impossible because of algae levels
10%
23%
0%
9%
28%
72%
90%
Site 201
Western Basin
Site 204
Eastern Basin
68%
Site 205
Northern Basin
Figure 6. Recreational suitability rating for all three basins, as rated by the volunteer monitor (1986-2008).
Total Phosphorus
Washburn Lake is phosphorus
limited, which means that algae
and aquatic plant growth is
dependent upon available
phosphorus.
Total phosphorus was evaluated in
Washburn Lake in 1986 and 2004-
2008 (Figure 7). The data indicate
that total phosphorus concentrations
stay relatively consistent
throughout the year and are
highest in May.
Site 204, the eastern basin, has
the highest average phosphorus
concentration. This result makes
sense because it is a very shallow
basin compared to the other two
basins. Site 202 in the northern
basin has the lowest average
phosphorus concentration.
Total Phosphrous (ug/L)
25
20
15
10
5
0
1-May
Total Phosphorus
Figure 7. Historical total phosphorus concentrations (ug/L) for
Washburn Lake (graph represents averages for each site throughout
the growing season from 2005-2008).
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1-Jun
1-Jul
1-Aug
1-Sep
Site 101
Site 202
Site 204
Site 206

Chlorophyll a
Chlorophyll a is the pigment
that makes plants and algae
Chlorophyll a
green. Chlorophyll a is tested
20
Site 101
in lakes to determine the algae
18
Site 202
concentration or how "green"
16
the water is.
Site 204
14
Site 206
Chlorophyll a concentrations
12
greater than 10 ug/L are
perceived as a mild algae
10
bloom, while concentrations
8
greater than 20 ug/L are
6
perceived as a nuisance.
4
Chlorophyll a was evaluated in
2
Washburn Lake in 1986 and
2004-2008 (Figure 8).
0
Chlorophyll a concentrations
remained below 10 ug/L in all
years at all sites, indicating
clear water most of the
Figure 8. Chlorophyll a concentrations (ug/L) for Washburn Lake (graph
summer. The chlorophyll a represents averages for each site throughout the growing season from
concentrations stay relatively
2005-2008)
steady throughout the summer,
which is consistent with the transparency results (Figure 4).
Dissolved Oxygen
Chlorophyll a (ug/L)
1-May
1-Jun
1-Jul
1-Aug
1-Sep
Dissolved Oxygen (mg/L)
0 2 4 6 8 10 12
0
1
2
3
4
5
6
7
Depth
(m)
8
9
10
12
14
16
18
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

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.
Trophic State Index
North Basin
Site 202
West Basin
Site 101
East Basin
Site 204
TSI Total Phosphorus 40 42 44
TSI Chlorophyll-a 46 46 44
TSI Secchi 41 42 43
TSI Mean 42 43 44
Trophic State: Mesotrophic Mesotrophic Mesotrophic
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 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 mean TSI indicates all basins are mesotrophic (Figure
10). There is good agreement between the TSI for
phosphorus, and transparency, indicating that these
variables are strongly related. The
chlorophyll a TSI is slightly higher than Washburn Lake
the others.
The east basin has a slightly higher mean TSI than the
north and west basins. These results are consistent with
the other monitoring results for Washburn Lake.
Hypereutrophic
Eutrophic
Mesotrophic
Oligotrophic
100
70
50
40
Mesotrophic lakes (TSI 40-50) are characterized by
moderately clear water most of the summer. "Meso"
means middle or mid; therefore, mesotrophic means a
medium amount of productivity. Mesotrophic lakes are
commonly found in central Minnesota and have clear
water with some algal blooms in late summer.
Figure 10. Trophic state index chart with
corresponding trophic status.
0
TSI Attributes Fisheries & Recreation
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 Washburn Lake. There was enough transparency data for all basins to perform long-term and
short-term trend analyses (Figure 11). The data was analyzed using the Mann Kendall Trend
Analysis.
Basin Lake Site Parameter Date Range Trend Probability
North 205 Transparency 1987-2007 Improving 90%
North 205 Transparency 1999-2007 Improving 99.9%
East 204 Transparency 1986-2008 Improving 99.9%
East 204 Transparency 2000-2008 No Trend ---
West 203 Transparency 1986-2007 Improving 99.9%
West 203 Transparency 1999-2007 No Trend ---
Figure 11. Transparency trend for the Washburn lake north basin from 1987-2007.
Overall, the transparency in Washburn Lake is improving in all bays. In the north basin the
transparency has increased approximately one foot from 1987-2007, the west basin has increased
approximately 2 feet from 1986-2007, and the east basin has increased approximately 2 feet from
1987-2007. In the east and west basins there is no trend in transparency occurring since 1999,
which means that the transparency is not declining or improving, it is staying the same.
Transparency monitoring should continue in all basins so that this trend can be tracked in the
future.
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Ecoregion Comparisons
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. 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 25 th - 75 th percentile
range for data within each ecoregion. For the purpose
of this graphical representation, the means of the
reference lake data sets were used.
Washburn Lake is in the Northern
Lakes and Forests Ecoregion.
The mean total phosphorus,
chlorophyll a and transparency
(secchi depth) for the Washburn are within the expected ecoregion ranges
(Figures 12a-c).
60
30
0
Total Phosphorus (ug/L, ppb)
50
40
30
20
10
Chlorophyll-a (ug/L, ppb)
25
20
15
10
5
Secchi depth (ft)
5
10
15
20
increased
algae
0
NLF Ecoregion
Washburn West
Wasburn North
Wasburn East
0
a b c
NLF Ecoregion
Washburn West
Wasburn North
Wasburn East
25
crystal
clear
Figures 12a-c. Washburn Lake ranges compared to Northern Lakes and Forest Ecoregion ranges. The
Washburn Lake total phosphorus and chlorophyll a ranges are from 25-33 data points in each basin
collected in May-September of 2004-2008. The Washburn Lake secchi depth range is from 161-405 data
points in each basin collected in May-September from 1986-2008.
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Inlet/Outlet Data Assessment
No inlet or outlet data exist for Washburn Lake.
Assessment/Findings Recommendations
Transparency
Transparency monitoring at all sites continued annually. It is important to continue transparency
monitoring weekly or at least bimonthly every year to enable year-to-year comparisons and trend
analyses.
Impaired Waters Assessment 303(d) List
There are two main types of Impaired Waters Assessment for lakes: eutrophication (excess
phosphorus) for aquatic recreation and mercury in fish tissue for aquatic consumption. Washburn
Lake was listed as impaired for mercury in fish tissue in the 2006 Impaired Waters List; however it
is part of the statewide mercury TMDL, so it was removed from the 2008 Impaired Waters List.
Washburn Lake is not listed as impaired for eutrophication.
Aquatic Recreational Use Assessment 305(b)
In the 2008 MPCA Aquatic Use Assessment (305(b)), Washburn Lake was classified as fully
supporting for recreational use.
Inlet/Outlet Assessment
Because of the lack of inlet/outlet data, a mass balance project should be considered. This study
answers questions about nutrient loading into the lake and nutrient budget within the lake.
Organizational contacts and reference sites
Washburn Lake Association
Cass County Environmental
Services Department
DNR Fisheries Office
Regional Minnesota Pollution
Control Agency Office
Regional Board of Soil and Water
Resources Office
http://www.minnesotawaters.org/index.phpuberKey=1292
303 Minnesota Avenue W, P.O. Box 3000, Walker, MN 56484-3000
(218) 547-7241
http://www.co.cass.mn.us/esd/home_esd.html
1601 Minnesota Drive, Brainerd, MN 56401
(218) 828-2550
http://www.dnr.state.mn.us/lakefind/index.html
7678 College Road, Suite 105, Baxter, MN 56425
(218) 828-2492
http://www.pca.state.mn.us
1601 Minnesota Drive, Brainerd, MN 56401
(218) 828-2383
http://www.bwsr.state.mn.us
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