Big Trout Lake CROW WING COUNTY

Transcription

1 Big Trout Lake CROW WING COUNTY Lake Water Quality Summary Big Trout Lake is located just east of Pine River, Minnesota. It covers 1,363 acres, which places it in the upper 10% of lakes in Minnesota in terms of size. Big Trout Lake has no major inlets or outlets. It has a connection with Lower Whitefish Lake and is tied to the Whitefish Chain of Lakes. Water levels in 13 of the lakes of the Whitefish Chain are controlled by the U.S. Army Corps of Engineers. They do this by adjusting water outflow levels at their dam in the city of Crosslake. The Pine River flows into and out of Whitefish Lake and eventually joins the Mississippi River. Water quality data have been collected on Big Trout Lake since These data show that the lake is at the oligotrophic/mesotrophic border (TSI 39-41), which is characterized by clear water throughout the summer and excellent recreational opportunities (page 9). The Whitefish Area Property Owners Association has been active since 1970 (Tables 2, 3). Their mission statement is "to promote environmental stewardship throughout the Whitefish area and the Pine River Watershed". The Association has been involved in numerous activities including water quality monitoring, education, state regulations, fishing and supporting local business. Table 1. Big Trout Lake location and key physical characteristics. Location Data MN Lake ID: County: CROW WING Ecoregion: Northern Lakes & Forests Major Drainage Basin: Upper Mississippi Latitude/Longitude: / Invasive Species: Curly-leaf pondweed Physical Characteristics Surface area (acres): 1,363 Littoral area (acres): 369 % Littoral area: 27% Max depth (ft), (m): 128, 39 Inlets: Connected to Whitefish Outlets: Public Accesses: Lake 1 Table 2: Availability of data and an observation of the quantity of sample points. Data Availability Transparency data Chemical data Numerous yearly Secchi readings from through the MPCA CLMP program. Total Phosphorus and Chlorophyll a data have been collected by WAPOA in Inlet/Outlet data -- Big Trout Lake has no major inlets or outlets Recommendations For recommendations refer to page 19. RMB Environmental Laboratories, Inc. 1 of Big Trout Lake

2 Lake Map Figure 1. Map of Big Trout Lake with 2010 aerial imagery and illustrations of sample site locations, inlets and outlets, and public access points. The light green areas in the lake illustrate the littoral zone, where the sunlight can usually reach the lake bottom allowing aquatic plants to grow. Table 3. Monitoring programs and associated monitoring sites. Monitoring programs include the Citizen Lake Monitoring Program (CLMP), Minnesota Pollution Control Agency (MPCA), and Whitefish Area Property Owners Association (WAPOA). Lake Site Depth (ft) Monitoring Programs MPCA: CLMP: CLMP: CLMP: CLMP: 1984, , CLMP: * Primary Site 70 CLMP: ; WAPOA: RMB Environmental Laboratories, Inc. 2 of Big Trout Lake

3 Average Water Quality Statistics The information below describes available chemical data for Big Trout Lake through The data set is limited, and all parameters, with the exception of total phosphorus, chlorophyll a and secchi depth, are means for just 1986 MPCA data. Minnesota is divided into seven ecoregions based on land use, vegetation, precipitation and geology. The MPCA has developed a way to determine the "average range" of water quality expected for lakes in each ecoregion. For more information on ecoregions and expected water quality ranges, see page 11. Table 4. Water quality means compared to ecoregion ranges and impaired waters standard. Impaired Parameter Mean Ecoregion Range 1 Waters Standard 2 Interpretation Total phosphorus (ug/l) > 30 3 Chlorophyll a (ug/l) > 9 Chlorophyll a max (ug/l) 6 <15 Secchi depth (ft) < 6.5 Dissolved oxygen Dimitic see page 8 Results are better than the expected range for the ecoregion. Dissolved oxygen depth profiles show that the deep areas of the lake are anoxic in late summer. Total Kieldahl Nitrogen Indicates insufficient nitrogen to support summer nitrogen-induced (mg/l) algae blooms. Alkalinity (mg/l) Indicates a low sensitivity to acid rain and a good buffering capacity. Color (Pt-Co Units) Indicates very clear water with little to no tannins (brown stain). ph Characteristic of a hard water lake. Lake water with ph less than 6.5 can affect fish spawning and the solubility of metals in the water. Chloride (mg/l) Slightly above the ecoregion average but still considered low level. Total Suspended Solids (mg/l) Specific Conductance (umhos/cm) Total Nitrogen :Total Phosphorus 1.5 <1-2 Within the ecoregion average range Within the ecoregion average range. 31:1 25:1 35:1 Indicates the lake is phosphorus limited, which means that algae growth is limited by the amount of phosphorus in the lake. 1 The ecoregion range is the 25 th -75 th percentile of summer means from ecoregion reference lakes 2 For further information regarding the Impaired Waters Assessment program, refer to 3 Chlorophyll a measurements have been corrected for pheophytin Units: 1 mg/l (ppm) = 1,000 ug/l (ppb) RMB Environmental Laboratories, Inc. 3 of Big Trout Lake

4 Water Quality Characteristics - Historical Means and Ranges Table 5. Water quality means and ranges for primary sites. Parameters Site 206 Total Phosphorus Mean (ug/l): 12 Total Phosphorus Min: 6 Total Phosphorus Max: 22 Number of Observations: 40 Chlorophyll a Mean (ug/l): 3 Chlorophyll-a Min: <1 Chlorophyll-a Max: 6 Number of Observations: 40 Secchi Depth Mean (ft): 15 Secchi Depth Min: 6.5 Secchi Depth Max: 23.5 Number of Observations: 86 Figure 2. Big Trout Lake total phosphorus, chlorophyll a and transparency historical ranges. The arrow represents the range and the black dot represents the historical mean (Primary Site 206). Figure adapted after Moore and Thornton, [Ed.] Lake and Reservoir Restoration Guidance Manual. (Doc. No. EPA 440/ ) RMB Environmental Laboratories, Inc. 4 of Big Trout Lake

5 Transparency (Secchi Depth) Transparency is how easily light can pass through a substance. In lakes it is how deep sunlight penetrates through the water. Plants and algae need sunlight to grow, so they are only able to grow in areas of lakes where the sun penetrates. Water transparency depends on the amount of particles in the water. An increase in particulates results in a decrease in transparency. The transparency varies year to year due to changes in weather, precipitation, lake use, flooding, temperature, lake levels, etc. The annual means for Big Trout Lake range from ft (Figure 3). Transparency was highest in 1993 and transparency was lower than the long-term mean. For trend analysis, see page 10. Transparency monitoring should be continued at site 206 to track water quality in Big Trout Lake. 20 Transparency: Annual Means Secchi Depth (ft) Annual Means Long-term Mean 0 Figure 3. Annual mean transparency for site 206. Big Trout Lake transparency ranges from 6.5 to 23.5 feet throughout the summer. Figure 4 shows the seasonal transparency dynamics. The maximum Secchi reading is usually obtained in early summer. Big Trout Lake transparency is high in May and June and declines through August. The transparency then rebounds in October after fall turnover. The dynamics have to do with algae and zooplankton population dynamics, and lake turnover. It is important for lake residents to understand the seasonal transparency dynamics in their lake so they are not worried about why their transparency is lower in August than it is in June. It is typical for a lake to vary in transparency throughout the summer RMB Environmental Laboratories, Inc. 5 of Big Trout Lake

6 25 20 Seasonal Transparency Dynamics Secchi Depth (ft) Figure 4. Seasonal transparency dynamics and year-to-year comparison (site 206). The grey line represents the pattern in the data. User Perceptions When volunteers collect secchi depth readings, they record their perceptions of the water based on the physical appearance and the recreational suitability. These perceptions can be compared to water quality parameters to see how the lake "user" would experience the lake at that time. Looking at transparency data, as the secchi depth decreases the perception of the lake's physical appearance rating decreases. Big Trout Lake was rated as being "crystal clear" 59% of the time between , and (Figure 5). 2% Physical Appearance Rating 59% Crystal clear water 39% 59% 39% Not quite crystal clear a little algae visible 2% Definite algae green, yellow, or brown color apparent 0% High algae levels with limited clarity and/or mild odor apparent 0% Severely high algae levels Figure 5. Physical appearance rating, as rated by the volunteer monitor. RMB Environmental Laboratories, Inc. 6 of Big Trout Lake

7 As the secchi depth decreases, the perception of recreational suitability of the lake decreases. Big Trout Lake was rated as being "beautiful" 80% of the time from , and % Recreational Suitability Rating 80% Beautiful, could not be better 20% Very minor aesthetic problems; excellent for swimming, boating 0.3% Swimming and aesthetic enjoyment of the lake slightly impaired because of algae levels 80% 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. Total Phosphorus Big Trout Lake is phosphorus limited, which means that algae and aquatic plant growth is dependent upon available phosphorus. Total phosphorus was evaluated in Big Trout Lake in The data indicate that phosphorus concentrations are lowest in July, and higher in May and September (Figure 7). This dynamic could be related to lake turnover during those months. There was one unusually high phosphorus data point in July of Total Phosphorus (ug/l) Total Phosphorus Mesotrophic Oligotrophic Figure 7. Historical total phosphorus concentrations (ug/l) at site 206 for Big Trout Lake. Phosphorus should continue to be monitored to track any future changes in water quality. RMB Environmental Laboratories, Inc. 7 of Big Trout Lake

8 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 (ug/l) Chlorophyll a Figure 8. Chlorophyll a concentrations (ug/l) for Big Trout Lake Minor Algae Bloom Chlorophyll a was evaluated in Big Trout Lake in (Figure 8). Chlorophyll a concentrations remained well below 10 ug/l, indicating clear water all summer and no nuisance algae blooms. Dissolved Oxygen Depth (m) Dissolved Oxygen (mg/l) 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 Trout Lake is a relatively deep lake, with a maximum depth of 128 ft. Dissolved oxygen profiles from indicate that Big Trout Lake stratifies in the summer (Figure 9). The thermocline occurs at feet, although the oxygen does not drop below 5 mg/l. This is excellent habitat for Cisco (Tullibee) fish. Big Trout Lake is designated by the DNR as a Cisco refuge lake. To read more about this designation, see the bottom of page 16. In addition, Big Trout Lake is stocked with Lake Trout Figure 9. Dissolved oxygen profiles for Big Trout Lake in RMB Environmental Laboratories, Inc. 8 of Big Trout Lake

9 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). Table 6. Trophic State Index. Trophic State Index Site 206 TSI Total Phosphorus 40 TSI Chlorophyll-a 41 TSI Secchi 38 TSI Mean 40 Oligotrophic/ Trophic State: Mesotrophic Numbers represent the mean TSI for each parameter. 100 The mean TSI for Big Trout Lake falls on the border between oligotrophic and mesotrophic (39-41). There is good agreement between the TSI for phosphorus, chlorophyll a and transparency, indicating that these variables are strongly related (Table 6). Lakes on the oligotrophic/mesotrophic border (TSI 39-41) are characteristic of clear water throughout the summer and Big Trout Lake are excellent for recreation (Table 7). The bottom of the deep areas of the lake becomes anoxic (no oxygen) during the summer, which is inhospitable to game fish. This occurrence is common in Minnesota lakes. Hypereutrophic Eutrophic Mesotrophic Oligotrophic Figure 10. Trophic state index chart with corresponding trophic status. Table 7. Trophic states and corresponding lake and fishery conditions. TSI Attributes Fisheries & Recreation <30 Oligotrophy: Clear water, oxygen throughout Trout fisheries dominate the year at the bottom of the lake, very deep cold water Bottom of shallower lakes may become anoxic (no oxygen). Trout fisheries in deep lakes only. Walleye, Cisco present 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 Eutrophy: Algae and aquatic plant problems possible. "Green" water most of the year. Warm-water fisheries only. Bass may dominate Blue-green algae dominate, algal scums and aquatic plant problems. Dense algae and aquatic plants. Low water clarity may discourage swimming and boating 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 A trophic state index for lakes. Limnology and Oceanography. 22: RMB Environmental Laboratories, Inc. 9 of Big Trout Lake

10 Trend Analysis For detecting trends, a minimum of 8-10 years of data with 4 or more readings per season are recommended. Minimum confidence accepted by the MPCA is 90%. This means that there is a 90% chance that the data are showing a true trend and a 10% chance that the trend is a random result of the data. Only short-term trends can be determined with just a few years of data, because there can be different wet years and dry years, water levels, weather, etc, that affect the water quality naturally. There is not enough historical data to perform trend analysis for total phosphorus or chlorophyll a on Big Trout Lake. Site 101 had enough transparency data to perform a short-term and long-term trend analysis (Table 8). The data was analyzed using the Mann Kendall Trend Analysis. Table 8. Trend analysis for Big Trout Lake. Lake Site Parameter Date Range Trend Probability 206 Transparency Declining 99.9% 206 Transparency Improving 90% 25.0 Transparency Trend for Big Trout Lake Secchi Depth (ft) Long-term trend Short-term trend Figure 11. Long-term and short-term transparency trends for site 206 in Big Trout Lake. Site 206 shows a statistically significant declining trend in transparency from (Figure 11). However, since 2000, there is an improving significant trend occurring, which means that the lake is rebounding from the previous decline. Transparency monitoring should continue at site 206 so that this trend can be tracked in future years. If the lake continues to improve, the long-term trend should not be declining in the future. See the recommendations on page 19 for more insight to the trends. RMB Environmental Laboratories, Inc. 10 of Big Trout Lake

11 Ecoregion Comparisons Minnesota is divided into 7 ecoregions based on land use, vegetation, precipitation and geology (Figure 12). The MPCA has developed a way to determine the "average range" of water quality expected for lakes in each ecoregion. From , 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. Big Trout Lake is in the Northern Lakes and Forests Ecoregion. The means for phosphorus and chlorophyll a were within the ecoregion ranges, while the transparency is better than the ecoregion range (Fig 13). Figure 12. Map of Minnesota with the seven ecoregions Total Phosphorus (ug/l, ppb) Chlorophyll-a (ug/l, ppb) Secchi depth (ft) increased algae crystal clear 0 0 NLF Big Trout Ecoregion NLF Ecoregion Big Trout a b c 25 NLF Ecoregion Big Trout Figures 13a-c. Big Trout Lake ranges compared to Northern Lakes and Forest Ecoregion ranges. The Big Trout Lake total phosphorus and chlorophyll a ranges are from 30 data points collected in May-September of The Big Trout Lake Secchi depth range is from 76 data points collected in May-September from RMB Environmental Laboratories, Inc. 11 of Big Trout Lake

12 Lakeshed Data and Interpretations Lakeshed Understanding a lakeshed requires an understanding of basic hydrology. A watershed is defined as all land and water surface area that contribute excess water to a defined point. The MN DNR has delineated three basic scales of watersheds (from large to small): 1) basins, 2) major watersheds, and 3) minor watersheds. The Pine River Major Watershed is one of the watersheds that make up the Upper Mississippi River Basin, which eventually drains south to the Gulf of Mexico (Figure 14). This major watershed is made up of 69 minor watersheds. Big Trout Lake is located in minor watershed (Figure 15). Figure 14. Pine River Watershed. Figure 15. Minor 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. Big Trout Lake falls within the lakeshed (Figure 16). Though very useful for displaying the land and water that contribute directly to a lake, lakesheds are not always true watersheds because they may not show the water flowing into a lake from upstream streams or rivers. While some lakes may have only one or two upstream lakesheds draining into them, others may be connected to a large number of lakesheds, reflecting a larger drainage area via stream or river networks. For further discussion of Big Trout Lake s full watershed, see page 17. The data interpretation of the Big Trout Lake lakeshed includes only the immediate lakeshed as this area is Figure 16. The Big Trout Lake lakeshed ( ). RMB Environmental Laboratories, Inc. 12 of Big Trout Lake

13 the land surface that flows directly into Big Trout Lake. The lakeshed vitals table identifies where to focus organizational and management efforts for each lake (Table 9). Criteria were developed using limnological concepts to determine the effect to lake water quality. KEY Possibly detrimental to the lake Warrants attention Beneficial to the lake Table 9. Big Trout lakeshed vitals table. Lakeshed Vitals Rating Lake Area 1,363 acres descriptive Littoral Zone Area 500 acres descriptive Lake Max Depth 128 ft. descriptive Lake Mean Depth 48 ft. descriptive Water Residence Time NA NA Miles of Stream 0.3 descriptive Inlets Outlets Connection to Whitefish Lake Connection to Whitefish Lake Major Watershed 11 Pine River descriptive Minor Watershed descriptive Lakeshed descriptive Ecoregion Northern Lakes and Forest descriptive Total Lakeshed to Lake Area Ratio (total lakeshed includes lake area) 6:1 Standard Watershed to Lake Basin Ratio (standard watershed includes lake areas) 6:1 Wetland Coverage 4.4% Aquatic Invasive Species Public Drainage Ditches Public Lake Accesses 1 Curly-leaf pondweed Present Miles of Shoreline 8.51 descriptive Shoreline Development Index 1.6 Public Land to Private Land Ratio 0.5:1 Development Classification General Development Miles of Road 15.4 descriptive Municipalities in lakeshed Forestry Practices Feedlots Sewage Management Lake Management Plan Lake Vegetation Survey/Plan None County Forest Management: None Individual Subsurface Sewage Treatment Systems (Inspection and assessment required for all permits and property transfers within the Shoreland Protection Zone) Healthy Lakes & Rivers Partnership program, 2008 None RMB Environmental Laboratories, Inc. 13 of Big Trout Lake

14 Land Cover / Land Use The activities that occur on the land within the lakeshed can greatly impact a lake. Land use planning helps ensure the use of land resources in an organized fashion so that the needs of the present and future generations can be best addressed. The basic purpose of land use planning is to ensure that each area of land will be used in a manner that provides maximum social benefits without degradation of the land resource. Changes in land use, and ultimately land cover, impact the hydrology of a lakeshed. Land cover is also directly related to the lands ability to absorb and store water rather than cause it to flow overland (gathering nutrients and sediment as it moves) towards the lowest point, typically the lake. Impervious intensity describes the lands inability to absorb water, the higher the % impervious intensity the more area that water cannot penetrate in to the soils. Monitoring the changes in land use can assist in future planning procedures to address the needs of future generations. Figure 17. The Big Trout Lake ( ) lakeshed land cover ( Phosphorus export, which is the main cause of lake eutrophication, depends on the type of land cover occurring in the lakeshed. Figure 17 depicts Big Trout Lake s lakeshed land cover. The University of Minnesota has online records of land cover statistics from years 1990 and 2000 ( Table 10 describes Big Trout Lake's lakeshed land cover statistics and percent change from 1990 to Due to the many factors that influence demographics, one cannot determine with certainty the projected statistics over the next 10, 20, 30+ years, but one can see the transition within the lakeshed from agriculture, grass/shrub/wetland, and water acreages to forest and urban acreages. The largest change in percentage is the decrease in grass/shrub/wetland cover (57.3%); however, in acreage, forest cover has increased the most (668 acres). In addition, the impervious intensity has increased, which has implications for storm water runoff into the lake. The increase in impervious intensity is consistent with the increase in urban acreage. RMB Environmental Laboratories, Inc. 14 of Big Trout Lake

15 Table 10. Big Trout lakeshed land cover statistics and % change from 1990 to 2000 ( % Change Land Cover Acres Percent Acres Percent 1990 to 2000 Agriculture % Decrease Forest 5, , % Increase Grass/Shrub/Wetland % Decrease Water 1, , % Decrease Urban % Increase Impervious Intensity % 0 7, , % Decrease % Increase % Increase % Decrease % Decrease % Decrease % Increase Total Area 8,145 8,145 Total Impervious Area (Percent Impervious Area Excludes Water Area) % Increase Demographics Big Trout Lake is classified as a general development lake. General development lakes usually have more than 225 acres of water per mile of shoreline and 25 dwellings per mile of shoreline, and are more than 15 feet deep. The Minnesota Department of Administration Geographic and Demographic Analysis Division extrapolated future population in 5-year increments out to These projections are shown in Figure 18 below. Compared to Crow Wing County as a whole, the city of Crosslake has a higher extrapolated growth projection, while Ideal and Timothy Townships, as well as the cities of Fifty Lakes and Manhattan Beach, have lower extrapolated growth projections (Figure 18) Population Growth Projection Figure 18. Population growth projection for Crow Wing County.and area Townships (source: aphy.state.mn.us/r esource.html?id=1 9332) Percentage of 2006 Population 70% 60% 50% 40% 30% 20% 10% 0% Ideal Township & City of Fifty Lakes; 2006 population: 983 & 406, respectively Timothy Tow nship; 2006 population: 155 City of Manhattan Beach; 2006 population: 62 City of Crosslake; 2006 population: 2,052 Crow Wing County; 2006 population: 61,038-10% Extrapolation RMB Environmental Laboratories, Inc. 15 of Big Trout Lake

16 Big Trout Lakeshed Water Quality Protection Strategy Each lakeshed has a different makeup of public and private lands. Looking in more detail at the makeup of these lands can give insight on where to focus protection efforts. The protected lands (easements, wetlands, public land) are the future water quality infrastructure for the lake. Developed land and agriculture have the highest phosphorus runoff coefficients, so this land should be minimized for water quality protection. The majority of the land within Big Trout s lakeshed is made up of private forested uplands. This land can be the focus of development and protection efforts in the lakeshed. Table 11. Land ownership, land use/land cover, estimated phosphorus loading, and ideas for protection and restoration in the lakeshed (Sources: Crow Wing County parcel data, National Wetlands Inventory, and the 2006 National Land Cover Dataset). Private (55%) 19% Public (26%) Developed Agriculture Forested Uplands Other Wetlands Open Water County State Federal Land Use (%) 3% 4.5% 27% 18.5% 2% 19% 1% 24% 1% Runoff Coefficient Lbs of phosphorus/acre/ year Description Focused on Shoreland Cropland Focus of development and protection efforts Open, pasture, grassland, shrubland Protected Potential Phase 3 Discussion Items Shoreline restoration Restore wetlands; CRP Forest stewardship planning, 3 rd party certification, SFIA, local woodland cooperatives Protected by Wetland Conservation Act County Tax Forfeit Lands State Forest National Forest DNR Fisheries approach for lake protection and restoration Credit: Peter Jacobson and Michael Duval, Minnesota DNR Fisheries In an effort to prioritize protection and restoration efforts of fishery lakes, the MN DNR has developed a ranking system by separating lakes into two categories, those needing protection and those needing restoration. Modeling by the DNR Fisheries Research Unit suggests that total phosphorus concentrations increase significantly over natural concentrations in lakes that have watershed with disturbance greater than 25%. Therefore, lakes with watersheds that have less than 25% disturbance need protection and lakes with more than 25% disturbance need restoration (Table 12). Watershed disturbance was defined as having urban, agricultural and mining land uses. Watershed protection is defined as publicly owned land or conservation easement. RMB Environmental Laboratories, Inc. 16 of Big Trout Lake

17 Table 12. Suggested approaches for watershed protection and restoration of DNR-managed fish lakes in Minnesota. Watershed Watershed Management Disturbance Protected Comments Type (%) (%) < 25% > 75% Vigilance < 75% Protection 25-60% n/a Full Restoration > 60% n/a Partial Restoration 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. These watersheds with low disturbance and high value fishery lakes are excellent candidates for priority protection measures, especially those that are related to forestry and minimizing the effects of landscape disturbance. Forest stewardship planning, harvest coordination to reduce hydrology impacts and forest conservation easements are some potential tools that can protect these high value resources for the long term. Big Trout Lake is classified with having 45.3% of the watershed protected and 6.2% of the watershed disturbed (Figure 19). Therefore, Big Trout Lake should have a protection focus. Goals for the lake should be to limit any increase in disturbed land use. In addition, Big Trout Lake was designated by DNR Fisheries as a high valued fishery lake because of its cisco population. Figure 20 displays the area that could contribute water to the lakeshed of interest. This particular lakeshed is a headwaters catchment, which means no additional lakesheds flow into it. The area highlighted green is the full watershed for Big Trout Lake. Percent of the Watershed Protected 0% 75% 100% Big Trout Lake (45.3%) Percent of the Watershed with Disturbed Land Cover 0% 25% 100% Big Trout Lake (6.2%) Figure 19. Big Trout Lake lakeshed s percentage of watershed protected and disturbed. Figure 20. Upstream lakesheds that contribute water to the Big Trout lakeshed. Color-coded based on management focus (Table 12). RMB Environmental Laboratories, Inc. 17 of Big Trout Lake

18 Big Trout, Status of the Fishery (as of 07/18/2005) Big Trout Lake is the only lake in the Brainerd management area that is stocked with lake trout. Big Trout covers 1,342 acres, and is 128 feet deep. The littoral area, less than 15 ft deep, covers 27% of the lake. Water clarity is good with a secchi depth of 18 ft. A public boat access is located on the eastern shore, or boaters can access through a channel from Whitefish Lake. The lake is heavily developed with 237 homes, 2 resorts, and 2 youth camps along its 8.5 miles of shoreline. A 2010 survey of the plant community found 41 native species, and one invasive plant (curlyleaf pondweed). Protection of aquatic vegetation, especially emergent vegetation, is important for maintaining good water quality. Also vegetation is critical for fish spawning areas as well as providing cover for fish. Northern pike were captured at the highest rate to date at 7.2/gillnet. Average length was 20.6 inches and weighing 2.1 lbs. Northern pike up to 34.4 inches were captured. Northern pike over 24 inches made up 19% of catch. Walleyes are not stocked directly into Big Trout, but are stocked into connecting Whitefish Lake annually as fry, and every other year as fingerlings. The walleye gillnet catch of 0.7/net was low, but the average size was nice at 22.1 inches and weight at 4.2 lbs. Walleye up to 28.4 inches were caught. Both largemouth and smallmouth bass are present in Big Trout. Largemouth bass were sampled throughout the Whitefish Chain, including Big Trout, by a spring electrofishing survey. They were caught at a rate of 112.5/hr. More data can be found in the Whitefish lake report. Bluegill numbers were above average, but their size leaves something to be desired. Average length was 4.9 inches, and only 5% were over 7 inches. The black crappie gillnet catch was average. All black crappies from gillnets were over 9 inches. All crappies captured in trapnets were from the 2010 year class and were less than 4 inches in length. Tullibee (Cisco) numbers at 12.5/gillnet were well above average. Nearly all (98%) of tullibee (cisco) were between 6 and 8 inches in length. At this size they are a valuable forage species for walleye, northern pike, and lake trout. Lake whitefish were also caught at above average numbers at a rate of 1.9/ gillnet. They averaged 1.7 lbs, and would be of interest to anglers. No lake trout were sampled in this survey, though they are present in the lake and are stocked into Big trout every other year. Other fish species present in this survey included smallmouth bass, rock bass, pumpkinseed sunfish, hybrid sunfish, brown bullhead, yellow bullhead, bowfin, greater redhorse, and green sunfish. See the link below for specific information on gillnet surveys, stocking information, and fish consumption guidelines. RMB Environmental Laboratories, Inc. 18 of Big Trout Lake

19 Key Findings / Recommendations Monitoring Recommendations Transparency monitoring at site 206 should be continued annually without gaps. It is important to continue transparency monitoring weekly or at least bimonthly every year to enable year-to-year comparisons and trend analyses. Phosphorus and chlorophyll a monitoring should continue at site 206, as the budget allows, to track future water quality trends. Overall Conclusions Overall, Big Trout Lake has excellent water quality, and is in good shape for lakeshed protection. It is an oligotrophic/mesotrophic lake (TSI=40) with a declining long-term trend and an improving short-term trend in transparency. This means the lake is recovering from decline that occurred in the 1990s. Based on a review of aerial photos, comparing 1991 to 2003, this may be due to increasing development directly adjacent to the shore. Twenty-six percent (26%) of the lakeshed is in public ownership, and 45% of the watershed is protected, while 6% of the watershed is disturbed (Figure 19). Big Trout Lake s lakeshed is wellforested, which is good protection for water quality. When subtracting out the water area, 86% of the lakeshed is forested (Table 10). Big Trout Lake is at an advantage in that it is a headwaters catchment, which means that no other lakesheds flow into it. This means the land practices around the lake are the main impact to the lake s water quality. Big Trout Lake is the only lake in the Brainerd DNR management area that s stocked with lake trout. It is also designated as a Cisco Refuge Lake by the DNR. The deep, well oxygenated water provide good habitat for trout and ciscos (Figure 9). In the 2011 DNR Fisheries survey, the cisco population was very healthy and abundant (page 18). Priority Impacts to the lake The priority impact to Big Trout Lake is the surrounding development and any future development. There is heavy development around the shoreline of Big Trout Lake (237 homes, 2 resorts, and 2 youth camps along its 8.5 miles of shoreline), in addition to many nearby towns: Crosslake, Fifty Lakes and Manhattan Beach. The City of Crosslake alone is expected to grow another 25% in the next 10 years (Figure 18). The entire land area between Big Trout and Whitefish is divided into parcels, though many are undeveloped. The concern with increased development is the conversion of forested land to a land use with increased impervious surfaces, such as roofs, driveways, and well groomed lawns. Poor septic system maintenance could also impact water quality. Phosphorus loading will increase when land use changes from forested to developed. A way to mitigate this issue is through the installation of Best Management Practices (BMPs). Further away from the lake itself, but still within the lakeshed there are numerous tax forfeited land parcels. Some of this area is being used to silviculture (timber management). These areas would also benefit water quality by following BMPs. Best Management Practices Recommendations The management focus for Big Trout Lake should be to protect the water quality and the lakeshed. Protection efforts should be focused on managing and/or decreasing the impact caused by additional development, and impervious surface area. Project ideas include protecting land with conservation easements, enforcing county shoreline ordinances, smart development, shoreline restoration, rain gardens, and septic system maintenance. Although it may not be possible to RMB Environmental Laboratories, Inc. 19 of Big Trout Lake

20 decrease the impervious area in the lakeshed, it is possible to reduce the impact of the impervious surface by retaining stormwater instead of allowing it to runoff into the streams. County-wide Recommendation In order to better manage the impact of septic systems on lake water quality, it is recommended that the county implement a lake-wide septic inspection program. In a program such as this, the county would focus on one to three lakes a year, pull septic system records on those lakes, and require old systems to be inspected. This program can rotate through the county doing a few lakes each year. Organizational contacts and reference sites Whitefish Area Property Owners Association DNR Fisheries Office Regional Minnesota Pollution Control Agency Office Crow Wing Soil and Water Conservation District Crow Wing County Environmental Services Department Minnesota Drive, Brainerd, MN brainerd.fisheries@state.mn.us 7678 College Road, Suite 105, Baxter, MN , Crow Wing County Land Services Building 322 Laurel St. Suite 13, Brainerd, MN Crow Wing County Land Services Building 322 Laurel St. Suite 14, Brainerd, MN Funding This project was funded in part by the Board of Water & Soil Resources and the Initiative Foundation, a regional foundation. RMB Environmental Laboratories, Inc. 20 of Big Trout Lake