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Washburn Lake Report generation: 2008, RMB Environmental Laboratories 1 of 12

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

Mean depth (ft): West Basin: 25.7 (m): 7.8 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

Numerous yearly secchi readings from 1986-2008 through the MPCA CLMP program.

Chemical data

Extensive Phosphorus and Chlorophyll a data have been collected.

Inlet/Outlet data

No inlet or outlet data exist for Washburn Lake.

Recommendations For recommendations refer to page 12.


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


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. Parameter

West Bay Site 101 Mean

North Bay Site 202 Mean

East Bay Site 204 Mean

Ecoregion

Range1

Interpretation

Total phosphorus (ug/L) 15.0 12.3 15.8 14 - 27 Chlorophyll a (ug/L) 2 5.3 5.0 4.7 4 - 10 Chlorophyll a max (ug/L) 9 9 14 <15 Secchi depth (ft) 11.8 12.9 10.8 7.5 - 15

Results are within the expected range for the ecoregion and indicative of a mesotrophic lake. For more on mesotrophic lakes, see page 9.

Dissolved oxygen see page 8 see page 8 see page 8 Dissolved oxygen depth profiles show that the deep areas of the lake are anoxic in late summer.

Total Kieldahl Nitrogen (mg/L)

0.57 0.61 0.80 0.4 - 0.75 Indicates insufficient nitrogen to support summer nitrogen-induced algae blooms.

Alkalinity (mg/L) 78 83 72 40 - 140 Indicates a low sensitivity to acid rain and a good buffering capacity.

Color (Pt-Co Units) 10 10 10 10 - 35 Indicates clear water with little to no tannins (brown stain).

pH 8.1 8.3 8.5 7.2 - 8.3 Characteristic of a hard water lake. Lake water pH less than 6.5 can affect fish spawning and the solubility of metals in the water.

Chloride (mg/L) 0.90 0.87 0.93 0.6 - 1.2 Within the expected range for the ecoregion.

Total Suspended Solids (mg/L)

2 1.5 2.4 <1 - 2 Site 204 is slightly higher than the ecoregion average, but still considered low level.

Conductivity (umhos/cm) 125 157 114 50 - 250 Within the expected range for the ecoregion.

Total Nitrogen :Total Phosphorus

30:1 39:1 45:1 25:1 – 35:1 The lake is phosphorus limited, which means that algae growth is limited by the amount of phosphorus in the lake.

Data Source: 1986, 2004 Minnesota Pollution Control Agency Lake Assessment Program 1The ecoregion range is the 25th-75th percentile of summer means from ecoregion reference lakes 2Chlorophyll a measurements have been corrected for pheophytin Units: 1 mg/L (ppm) = 1,000 ug/L (ppb)


Water Quality Characteristics - Historical Means Years monitored: 1986-2008

West Basin

North Basin

East Basin

Parameters Site 101

Site 201

Site 203

Site 206

Site 202

Site 205

Site 207

Site 208

Site 204

Total Phosphorus Mean (ug/L): 15.0 13.1 12.3 15.8Total Phosphorus Min: 6 8 8 9Total Phosphorus Max: 33 19 20 31Number of Observations: 28 20 25 33Chlorophyll a Mean (ug/L): 5.3 5.6 5.0 4.7Chlorophyll-a Min: 2 2 2.0 1Chlorophyll-a Max: 9 8 9.0 14Number of Observations: 28 20 24 32Secchi Depth Mean (ft): 11.8 13.1 10.2 11.0 12.9 15.3 13.9 14.6 10.8Secchi Depth Min: 5.9 8.0 4.5 5.5 8.2 10.5 9.0 10.5 6.0Secchi Depth Max: 17.0 18.5 16.0 17.0 18.5 21.0 19.0 19.0 18.0Number of Observations: 40 160 310 67 49 286 148 34 405

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)


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.

Transparency: Annual Means

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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.


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).

2%

94%

4%

Figure 5. Physical appearance rating for all three basins, as rated by the volunteer monitor (1986-2008).

Site 201 Western Basin

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

Physical Appearance Rating

7%

66%

27%

42%

56%

2%

Site 204 Eastern Basin

Site 205 Northern Basin


Figure 7. Historical total phosphorus concentrations (ug/L) for Washburn Lake (graph represents averages for each site throughout the growing season from 2005-2008).

10%

90% 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 concen-trations 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.

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

Recreational Suitability Rating 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).

9%

68%

23%

0%

Site 201 Western Basin

Site 204 Eastern Basin

72%

28%

Site 205 Northern Basin

Total Phosphorus

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Chlorophyll a Chlorophyll a is the pigment that makes plants and algae green. Chlorophyll a is tested in lakes to determine the algae concentration or how "green" the water is. Chlorophyll a 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 was evaluated in Washburn Lake in 1986 and 2004-2008 (Figure 8). Chlorophyll a concentrations remained below 10 ug/L in all years at all sites, indicating clear water most of the summer. The chlorophyll a concentrations stay relatively steady throughout the summer, which is consistent with the transparency results (Figure 4). Dissolved Oxygen

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 fish. The north and west basins of Washburn Lake are very deep - 90 ft and 111 ft, respectively. Both sites 101 and 103 stratified and dropped below 5 mg/L around 10 meters during most of the summer. The eastern basin is shallow and mixes throughout the summer (Figure 9). These results indicate that game fish will not be present below 10 meters in the north and west basins in mid-summer due to low oxygen levels. This occurrence is typical in mesotrophic Minnesota lakes.

Figure 8. Chlorophyll a concentrations (ug/L) for Washburn Lake (graph represents averages for each site throughout the growing season from 2005-2008)

Figure 9. Dissolved oxygen and temperature profile for Washburn Lake on August 16, 2004.

Chlorophyll a

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100

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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 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 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. 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. TSI Attributes Fisheries & Recreation <30 Oligotrophy: Clear water, oxygen throughout

the year at the bottom of the lake, very deep cold water.

Trout fisheries dominate.

30-40 Bottom of shallower lakes may become anoxic (no oxygen).

Trout fisheries in deep lakes only. Walleye, Tullibee present.

40-50 Mesotrophy: Water moderately clear most of the summer. May be "greener" in late summer.

No oxygen at the bottom of the lake results in loss of trout. Walleye may predominate.

50-60 Eutrophy: Algae and aquatic plant problems possible. "Green" water most of the year.

Warm-water fisheries only. Bass may dominate.

60-70 Blue-green algae dominate, algal scums and aquatic plant problems.

Dense algae and aquatic plants. Low water clarity may discourage swimming and boating.

70-80 Hypereutrophy: Dense algae and aquatic plants.

Water is not suitable for 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.

Trophic State Index North BasinSite 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.

Figure 10. Trophic state index chart with corresponding trophic status.

Washburn Lake


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.


increased algae

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 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.

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).

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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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 http://www.minnesotawaters.org/index.php?uberKey=1292

Cass County Environmental Services Department

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

DNR Fisheries Office 1601 Minnesota Drive, Brainerd, MN 56401 (218) 828-2550 http://www.dnr.state.mn.us/lakefind/index.html

Regional Minnesota Pollution Control Agency Office

7678 College Road, Suite 105, Baxter, MN 56425 (218) 828-2492 http://www.pca.state.mn.us

Regional Board of Soil and Water Resources Office

1601 Minnesota Drive, Brainerd, MN 56401 (218) 828-2383 http://www.bwsr.state.mn.us

Inlet/Outlet Data Assessment

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