Loon Lake ITASCA COUNTY

Transcription

1 Loon Lake ITASCA COUNTY Lake Water Quality Summary Loon Lake is located 5 miles west of Grand Rapids, MN in Itasca County. It is a long lake covering 231 acres (Table 1). Loon Lake has one inlet and one outlet, which classify it as a drainage lake. Water enters Loon Lake from Long Lake in the southwest. The outlet flows north to Jay Gould Lake, which joins the Mississippi River. Water quality data have been collected on Loon Lake since 1991 (Tables 2 & 3). These data show that the lake is mesotrophic (TSI = 4) with clear water conditions all summer and excellent recreational opportunities. Loon Lake has an organized association that is involved in activities such as water quality monitoring and education. Table 1. Loon Lake location and key physical characteristics. Location Data MN Lake ID: County: Itasca Ecoregion: Northern Lakes and Forests Major Drainage Basin: Mississippi R. Headwaters Latitude/Longitude: / Invasive Species: None ( as of 214) Physical Characteristics Surface area (acres): 231. Littoral area (acres): N/A % Littoral area: N/A Max depth (ft), (m): 69., 21. Inlets: 1 Outlets: 1 Public Accesses: 1 Table 2. Availability of primary data types for Loon Lake. Data Availability Transparency data Good data set from Chemical data Good data set, but not enough for trend analysis. Inlet/Outlet data None available. Recommendations For recommendations refer to page 19. RMB Environmental Laboratories, Inc. 1 of Loon Lake

2 Lake Map Figure 1. Map of Loon Lake with 21 aerial imagery and illustrations of sample site locations, inlets and outlets, and public access points. Table 3. Monitoring programs and associated monitoring sites. Monitoring programs include the Citizen Lake Monitoring Program (CLMP), Atmospheric and Nonpoint Trends in MN Lakes LCMR study (LCMR), Clean Water Legacy Surface Water Monitoring (CWL), Itasca County Lake Assessment (ICLA), Mercury Trends (MT), MPCA Lake Monitoring Program Project (LMPP). Lake Site Depth (ft) Monitoring Programs 1 6 LCMR: 1995; ICLA: CLMP: 1992, ; ICLA: *primary site 69 CLMP: 1995; CWL: ; LMPP: MT: 211 RMB Environmental Laboratories, Inc. 2 of Loon Lake

3 Average Water Quality Statistics The information below describes available chemical data for Loon Lake through 214 (Table 4). Data for total phosphorus, chlorophyll a, and Secchi depth are from the primary site 22. 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 11. Loon Lake is in the Northern Lakes and Forests Ecoregion. Table 4. Water quality means compared to ecoregion ranges and impaired waters standard. Impaired Parameter Mean Ecoregion Range 1 Waters Standard 2 Total phosphorus (ug/l) > 3 3 Chlorophyll a (ug/l) > 9 Chlorophyll a max (ug/l) 9. < 15 Secchi depth (ft) < 6.5 Interpretation Results are better than the expected range for the Northern Lakes and Forests Ecoregion. Dissolved oxygen See page 8 Dissolved oxygen depth profiles show that the lake mixes in spring and fall (dimictic). Total Kjeldahl Nitrogen (mg/l).72 <.4.75 Indicates insufficient nitrogen to support summer nitrogeninduced algae blooms. Alkalinity (mg/l) Indicates a low sensitivity to acid rain and a good buffering capacity. Color (Pt-Co Units) Indicates clear water with little to no tannins (brown stain). ph 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) Higher than the expected range for the ecoregion. Total Suspended Solids (mg/l) 2.4 <1 2 Indicates low suspended solids and clear water. Conductivity (umhos/cm) Higher than the expected range for the ecoregion. TN:TP Ratio 29:1 25:1-35:1 Within the expected range for the ecoregion, and shows the lake is phosphorus limited. 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, ug/l (ppb) RMB Environmental Laboratories, Inc. 3 of Loon Lake

4 Water Quality Characteristics - Historical Means and Ranges Table 5. Water quality means and ranges for primary sites. Parameters Site 21 Primary Site 22 Total Phosphorus Mean (ug/l): Total Phosphorus Min: 17 3 Total Phosphorus Max: 31 2 Number of Observations: 2 11 Chlorophyll a Mean (ug/l): Chlorophyll-a Min: Chlorophyll-a Max: Number of Observations: 1 16 Secchi Depth Mean (ft): Secchi Depth Min: Secchi Depth Max: Number of Observations: 2 17 Figure Figure 2. Loon 2. Lake Lake insert total phosphorus, total phosphorus, chlorophyll chlorophyll a and a transparency and transparency historical historical ranges. ranges. The arrow The arrow represents represents the the range range and and the the black black dot dot represents represents the the historical historical mean mean (Primary (Primary Site Site 22). xxx). Figure Figure adapted adapted after Moore and Thornton, [Ed.] Lake and Reservoir Restoration Guidance Manual. (Doc. No. EPA 44/5-88-2) after Moore and Thornton, [Ed.] Lake and Reservoir Restoration Guidance Manual. (Doc. No. EPA 44/5-88-2) RMB Environmental Laboratories, Inc. 4 of Loon 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 mean transparency in Loon Lake ranges from 12.2 to 15.5 feet (Figure 3). The annual means hover very close to the long-term mean. For trend analysis, see page 1. Transparency monitoring should be continued annually at site 21 in order to track water quality changes. Secchi Depth (ft) Transparency and Precipitation Precipitation Secchi Mean Precipitation (in) Figure 3. Annual mean transparency compared to long-term mean transparency. Loon Lake transparency ranges from 2.9 to 14. ft at site 21. Figure 4 shows the seasonal transparency dynamics. Loon Lake has very consistent transparency all summer. This is characteristic of a lake with very low nutrients, as there are not enough nutrients to feed algae blooms. The dynamics have to do with algae and zooplankton population dynamics, and lake turnover. RMB Environmental Laboratories, Inc. 5 of Loon Lake

6 Secchi Depth (ft) Seasonal Transparency Dynamics Figure 4. Seasonal transparency dynamics and year to year comparison (Site 21). The black line represents the pattern in the data. User Perceptions When volunteers collect Secchi depth readings, they record their perceptions of the water based on the physical appearance and the recreational suitability. These perceptions can be compared to water quality parameters to see how the lake "user" would experience the lake at that time. Looking at transparency data, as the Secchi depth decreases the perception of the lake's physical appearance rating decreases. Loon Lake was rated as being "crystal clear" 53% of the time by samplers at site 22 between 1991 and 214 (Figure 5). 6% Physical Appearance Rating 53% Crystal clear water 41% 53% 41% Not quite crystal clear a little algae visible 6% Definite algae green, yellow, or brown color apparent % High algae levels with limited clarity and/or mild odor apparent % Severely high algae levels Figure 5. Loon Lake physical appearance ratings by samplers. RMB Environmental Laboratories, Inc. 6 of Loon Lake

7 As the Secchi depth decreases, the perception of recreational suitability of the lake decreases. Loon Lake was rated as being "beautiful" 81% of the time from 1991 to 214 (Figure 6). Recreational Suitability Rating 6% 13% 81% Beautiful, could not be better 13% Very minor aesthetic problems; excellent for swimming, boating 6% 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 81% % 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 Loon Lake is phosphorus limited, which means that algae and aquatic plant growth is dependent upon available phosphorus. Total phosphorus was evaluated in Loon Lake in 1997, 1998 and 214. There are not enough data to determine a seasonal pattern in the lake. The majority of the data points fall into the oligotrophic range (Figure 7). Total Phosphorus (ug/l) Mesotrophic Oligotrophic Total Phosphorus Phosphorus should continue to be Figure 7. Historical total phosphorus concentrations (ug/l) for Loon Lake site 22. monitored to track any future changes in water quality. RMB Environmental Laboratories, Inc. 7 of Loon 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 1 ug/l are perceived as a mild algae bloom, while concentrations greater than 2 ug/l are perceived as a nuisance. Chlorophyll a (ug/l) Chlorophyll a Minor Algae Chlorophyll a was evaluated in Loon Lake in , (Figure 8). Chlorophyll a concentrations remained below 1 ug/l in all years, indicating no algae blooms. Figure 8. Chlorophyll a concentrations (ug/l) for Loon Lake at site 22. 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. Loon Lake is a deep lake, with a maximum depth of 69 feet. Dissolved oxygen profiles from data collected in 213 show stratification developing mid-summer (Figure 9). The thermocline appears to be at around 5-7 meters ( feet) and the oxygen is depleted below this depth in late summer. Figure 9. Dissolved oxygen profile for Loon Lake. RMB Environmental Laboratories, Inc. 8 of Loon Lake

9 Trophic State Index (TSI) TSI is a standard measure or means for calculating the trophic status or productivity of a lake. More specifically, it is the total weight of living algae (algae biomass) in a waterbody at a specific location and time. Three variables, chlorophyll a, Secchi depth, and total phosphorus, independently estimate algal biomass. 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. If all three TSI numbers are within a few points of each other, they are strongly related. If they are different, there are other dynamics influencing the lake s productivity, and TSI mean should not be reported for the lake. The mean TSI for Loon Lake falls into the mesotrophic range (Figure 1). There is good agreement between the TSI for phosphorus, chlorophyll a and transparency, indicating that these variables are strongly related (Table 6). Loon Lake Table 6. Trophic State Index for Loon Lake. Trophic State Index Site 21 TSI Total Phosphorus 37 TSI Chlorophyll-a 41 TSI Secchi 4 TSI Mean 4 Trophic State: Mesotrophic Numbers represent the mean TSI for each parameter. Hypereutrophic Eutrophic Mesotrophic Oligotrophic Mesotrophic lakes (TSI 4-5) 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 algal blooms in late summer (Table 7). They are also good for walleye fishing. Figure 1. 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 <3 Oligotrophy: Clear water, oxygen throughout Trout fisheries dominate the year at the bottom of the lake, very deep cold water. 3-4 Bottom of shallower lakes may become anoxic (no oxygen). Trout fisheries in deep lakes only. Walleye, Cisco present. 4-5 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. 5-6 Eutrophy: Algae and aquatic plant problems possible. "Green" water most of the year. Warm-water fisheries only. Bass may dominate. 6-7 Blue-green algae dominate, algal scums and aquatic plant problems. Dense algae and aquatic plants. Low water clarity may discourage swimming and boating. 7-8 Hypereutrophy: Dense algae and aquatic Water is not suitable for recreation. plants. >8 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 Loon Lake

10 Trend Analysis For detecting trends, a minimum of 8-1 years of data with 4 or more readings per season are recommended. Minimum confidence accepted by the MPCA is 9%. This means that there is a 9% chance that the data are showing a true trend and a 1% 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. Loon Lake had enough data to perform a trend analysis on transparency (Table 8). The data was analyzed using the Mann Kendall Trend Analysis. Table 8. Trend analysis for Loon Lake. Lake Site Parameter Date Range Trend 22 Total Phosphorus , 214 Insufficient data 22 Chlorophyll a , Insufficient data 21 Transparency , No trend 25 Loon Lake Transparency Trend Secchi Depth (ft) /29/1991 6/22/1992 8/27/1992 1/24/1992 7/9/1994 9/3/1994 6/12/1995 8/5/1995 9/23/1995 9/14/1996 8/14/1997 6/27/1998 9/26/1998 7/24/1999 6/29/2 9/3/2 8/11/21 6/2/22 1/9/22 9/18/23 9/3/24 7/29/25 7/19/26 7/5/27 11/4/27 9/2/28 9/3/29 1/13/21 8/23/212 Figure 11. Transparency (feet) trend for site 21 from , Loon Lake shows no evidence of a transparency trend (Figure 11). This means the transparency in the lake is stable. Transparency monitoring should continue so that trends can be tracked in future years. RMB Environmental Laboratories, Inc. 1 of Loon 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. Loon Lake is in the Northern Lakes and Forests Ecoregion. The mean total phosphorus, chlorophyll a and transparency (Secchi depth) for Loon Lake are better than the ecoregion ranges (Figure 13). Figure 12. Minnesota Ecoregions. 6 3 Total Phosphorus (ug/l, ppb) Chlorophyll-a (ug/l, ppb) Secchi depth (ft) increased algae crystal clear NLF Ecoregion Loon NLF Ecoregion Loon 25 CHF Ecoregion Loon Figure 13. Loon Lake ranges compared to Northern Lakes and Forest Ecoregion ranges. The Loon Lake total phosphorus and chlorophyll a ranges are from 11 data points collected in May-September of , 213. The Loon Lake Secchi depth range is from 2 data points collected in May-September of RMB Environmental Laboratories, Inc. 11 of Loon 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 Mississippi Headwaters Major Watershed is one of the watersheds that make up the Upper Mississippi River Basin, which drains south to the Gulf of Mexico (Figure 14). Loon Lake is located in minor watershed 76 (Figure 15). Figure 14. Major Watershed. Figure 15. Minor Watershed. The MN DNR also has evaluated catchments for each individual lake with greater than 1 acres surface area. These lakesheds (catchments) are the building blocks for the larger scale watersheds. Loon Lake falls within lakeshed 763 (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 Figure 16. Loon Lake lakeshed (763) with land ownership, lakes, into them, others may be wetlands, and rivers illustrated. connected to a large number of lakesheds, reflecting a larger drainage area via stream or river networks. For further discussion of RMB Environmental Laboratories, Inc. 12 of Loon Lake

13 Loon Lake s watershed, containing all the lakesheds upstream of the Loon Lake lakeshed, see page 17. The data interpretation of the Loon Lake lakeshed includes only the immediate lakeshed as this area is the land surface that flows directly into Loon 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. Loon Lake lakeshed vitals table. Lakeshed Vitals Rating Lake Area acres descriptive Littoral Zone Area 48 acres descriptive Lake Max Depth 69 feet descriptive Lake Mean Depth NA NA Water Residence Time NA NA Miles of Stream miles descriptive Inlets 1 Outlets 1 Major Watershed 7 - Mississippi River-Headwaters descriptive Minor Watershed 76 descriptive Lakeshed 763 descriptive Ecoregion Northern Lakes and Forests descriptive Total Lakeshed to Lake Area Ratio (total lakeshed includes lake area) 3:1 Standard Watershed to Lake Basin Ratio (standard watershed includes lake areas) 6:1 Wetland Coverage (NWI) 12.3% Aquatic Invasive Species Public Drainage Ditches Public Lake Accesses 1 None Miles of Shoreline 3.61 miles descriptive Shoreline Development Index 1.7 Public Land to Private Land Ratio 1:315.5 Development Classification Natural Environment Miles of Road 1.77 miles descriptive Municipalities in lakeshed Forestry Practices Cohasset None Feedlots Sewage Management Individual Waste Treatment Systems (septic systems and holding tanks) Lake Management Plan None Lake Vegetation Survey/Plan DNR, 2 RMB Environmental Laboratories, Inc. 13 of Loon 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 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, typically the lake. Impervious intensity describes the land s inability to absorb water, the higher the % impervious intensity the more area that water cannot penetrate in to the soils. Monitoring the changes in land use can assist in future planning procedures to address the needs of future generations. Figure 17. Loon Lake lakeshed (763) land cover (NLCD 211). Phosphorus export, which is the main cause of lake eutrophication, depends on the type of land cover occurring in the lakeshed. Figure 17 depicts the land cover in Loon Lake s lakeshed. The National Land Cover Dataset (NLCD) has records from 21 and 211. Table 1 describes Loon Lake s lakeshed land cover statistics and percent change from 21 to 211. Overall, there was an increase in open water and a decrease in woody wetlands and forests, which likely shows a rise in water levels. There was not much change in impervious or urban acreage from RMB Environmental Laboratories, Inc. 14 of Loon Lake

15 Table 1. Loon Lake s lakeshed land cover statistics and % change from 21 to 211 (Data Source: NLCD) % Change Land Cover Acres Percent Acres Percent 21 to 211 Deciduous Forest Developed, Low Intensity Developed, Medium Intensity Developed, Open Space Emergent Herbaceous Wetlands Evergreen Forest Mixed Forest Open Water Pasture/Hay Shrub/Scrub Woody Wetlands Total Area Table 11. Loon Lake development area and % change from (Data Source: UMN Landsat) % Change Category Acres Percent Acres Percent 199 to 2 Total Impervious Area Urban Acreage Demographics Loon Lake is classified as a Natural Environment lake Natural Environment lakes usually have less than 15 total acres, less than 6 acres per mile of shoreline, and less than three dwellings per mile of shoreline. They may have some winter kill of fish; may have shallow, swampy shoreline; and are less than 15 feet deep. The Minnesota Department of Administration Geographic and Demographic Analysis Division extrapolated future population in 5-year increments out to 235. Compared to Itasca County as a whole, La Prairie has a higher growth projection (Figure 18). (source: Percent 25% 2% 15% 1% Population Growth Projection Compared to 21 Population La Prairie; 21 population = 673 Itasca County; 21 population = 45,58 Ec Dev Region; 21 population = 326,225 5% % Year Figure 18. Population growth projection for adjacent townships, Itasca County. RMB Environmental Laboratories, Inc. 15 of Loon Lake

16 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 Loon Lake s lakeshed is privately owned forested uplands (Table 12). This land can be the focus of development and protection efforts in the lakeshed. Table 12. Land ownership, land use/land cover, estimated phosphorus loading, and ideas for protection and restoration in the lakeshed (Sources: County parcel data and the 211 National Land Cover Dataset). Private (63.1) 36.8 Public (.2) Developed Agriculture Forested Uplands Other Wetlands Open Water County State Federal Land Use (%) Runoff Coefficient Lbs of phosphorus/acre/year Estimated Phosphorus Loading Acreage x runoff coefficient Description Focused on Shoreland Cropland Focus of development and protection efforts Open, pasture, grassland, shrubland Protected Restoration and Protection Ideas 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 13). 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 Loon Lake

17 Table 13. Suggested approaches for watershed protection and restoration of DNR-managed fish lakes in Minnesota. Watershed Disturbance (%) Watershed Protected (%) Management Type Comments < 25% > 75% Vigilance < 75% Protection 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%. 25-6% n/a Full Restoration > 6% n/a Partial Restoration 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. Loon Lake s lakeshed is classified with having 38.7% of the watershed protected and 18.7% of the watershed disturbed (Figure 19). Therefore, this lakeshed should have a protection focus. Goals for the lake should be to limit any increase in disturbed land use. Loon Lake has one other lakeshed flowing into it (Figure 2). Percent of the Watershed Protected % 1% 75% Loon Lake (38.7%) Percent of the Watershed with Disturbed Land Cover % 25% 1% Loon Lake (18.7%) Figure 19. Loon Lake s lakeshed percentage of watershed protected and disturbed. Figure 2. Lakesheds that contribute water to the Loon Lake lakeshed. Color-coded based on management focus (Table 13). RMB Environmental Laboratories, Inc. 17 of Loon Lake

18 Status of the Fishery (DNR, as of 6/5/26) Loon Lake is a 235-acre lake located 5 miles west of Grand Rapids, MN. The lake has a maximum depth of 69 ft and a littoral area of 48 acres. Loon Lake is in lake class 23 and has a public access on the southeast shore. Bulrush beds, firm shoreline, and clear water characterize the lake. Northern pike gill-net catch was 6.2/net, which was within the expected range for similar lakes. The catch rate in past assessments has varied considerably from.3 to 15.3/net. Size structure was good for fish over 21 inches, but few fish larger than 28 inches were sampled. Growth was similar to the statewide average for fish ages 1 to 6, but was slower than average for fish ages 7 to 9. Northern pike averaged 24 inches by age 9. Northern pike size structure may be improved by releasing fish over 24 inches. Large northern pike often prey on small northern pike, which helps the lake from overpopulating, increases growth for the remaining fish, and leads to improved size structure. The bluegill trap-net catch was 26.2/net and was within the expected range for similar lakes. Catch rates in past assessments have varied from 1.3 to 61.7/net. Size structure was poor with a no fish larger than 8 inches sampled. Largemouth bass were sampled using night electrofishing for a catch rate of 76.5/hour. The catch rate in this assessment was much higher than catch rates sampled in 1992 and 1999 of 23.1 and 22./hour, respectively. This assessment sampled many fish less than 8 inches, which likely increased the catch rate compared to past assessments. Size structure was poor, with few fish larger than 15 inches sampled. Growth was similar to the statewide average. Two black crappie were sampled in this assessment. Based on angler reports and past surveys, black crappie are likely more abundant than this survey would indicate. The low catch rate may be due to poor sampling of crappie that often suspend over open water, thus avoiding survey nets. Yellow perch gill-net catch was 5.2/gill net and was similar to the average value for similar lakes. Catch rates in past assessments have generally been less than 5./gill net, but have varied from 2. to 3.7/net. Size structure was poor with only one fish sampled greater than 9 inches. Tullibee or cisco catch rate was 12./gill net, which was higher than the expected range. Catch rates in past assessments have been highly variable from 5.8 to 29.7/gill net. Roughly 2/3 of the fish examined were infected with the triaenophorus parasite. Other fish sampled include, bowfin, burbot, golden shiner, pumpkinseed sunfish, rock bass, walleye, and yellow bullhead. See the link below for specific information on gillnet surveys, stocking information, and fish consumption guidelines. RMB Environmental Laboratories, Inc. 18 of Loon Lake

19 Key Findings / Recommendations Monitoring Recommendations Transparency monitoring at site 21 should be 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. Total Phosphorus and chlorophyll a monitoring should continue, as the budget allows, to track trends in water quality. The inlet to Loon Lake appears to be minor, but if it is suspected as a phosphorus source to the lake it could be monitored for phosphorus. Overall Summary Loon Lake is a mesotrophic lake (TSI = 4) with no evidence of a trend in water clarity. The total phosphorus, chlorophyll a and transparency ranges are better than the expected ecoregion ranges. Eighteen percent (18%) of the Loon Lake lakeshed is disturbed by development and agriculture (Figure 19). The threshold of disturbance where water quality tends to decline is 25%. Loon Lake is approaching this threshold, but all of the agricultural land is pasture, not row crops or feedlots (Table 9, 11, Figure 17). Row crops and feedlots are a higher land disturbance than pasture, so the pasture has a lower potential to affect the lake s water quality. Most of the privately owned land is forested uplands (23%) or wetlands (17%), which is generally good for water quality (Table 12). Priority Impacts to the Lake The priority impact to Loon Lake would be the expansion of residential housing development and second tier development around the lakeshore. The conversion of small lake cabins to year-round family homes increases the impervious surface and runoff from the lake lots. Most of the first tier is developed except for the western shore (Figure 16). Some of the second tier remains in large parcels and has not been subdivided for development. Loon Lake is close to Grand Rapids, which increases the development pressure on the lake. Many of the developed parcels on the northern shore have cleared large areas of trees to turf lawn (Figure 1). This allows runoff to run over those properties. Best Management Practices Recommendations The management focus for Loon Lake should be to protect the current water quality and lakeshed. Efforts should be focused on managing and/or decreasing the impact caused by additional development, including second tier development, and impervious surface area on existing lots (conversion of seasonal cabins to year-round homes). The current lakeshore homeowners can lessen their negative impact on water quality by installing or maintaining the existing trees on their properties. Forested uplands contribute significantly less phosphorus (lbs/acre/year) than developed land cover (Table 12). Forested uplands can be managed with Forest Stewardship Planning. In addition, filter strips or native vegetative buffers could be installed to decrease or slow the runoff reaching the water s edge. Especially focus on adding more vegetation and trees to the large parcels on the north shore. Septic systems should be pumped and inspected regularly. The lakeshed still has large undeveloped shoreline parcels (Figure 16). Because a lot of undeveloped private land still exists, there is a great potential for protecting this land with conservation easements and aquatic management areas (AMAs). Conservation easements can be set up easily and with little cost with help from organizations such as the Board of Soil and RMB Environmental Laboratories, Inc. 19 of Loon Lake

20 Water Resources and the Minnesota Land Trust. AMAs can be set up through the local DNR fisheries office. Project Implementation The best management practices above can be implemented by a variety of entities. Some possibilities are listed below. Individual property owners Shoreline restoration Rain gardens Aquatic plant bed protection (only remove a small area for swimming) Conservation easements Lake Associations Lake condition monitoring Ground truthing visual inspection upstream on stream inlets Watershed runoff mapping by a consultant Shoreline inventory study by a consultant Conservation easements Soil and Water Conservation District (SWCD) and Natural Resources Conservation Service (NRCS) Shoreline restoration Stream buffers Wetland restoration Forest stewardship planning Work with farmers to o Restore wetlands o Implement conservation farming practices o Land retirement programs such as Conservation Reserve Program Organizational contacts and reference sites Loon Lake Association Itasca County Environmental Services Department Itasca Soil and Water Conservation District DNR Fisheries Office Regional Minnesota Pollution Control Agency Office Regional Board of Soil and Water Resources Office 124 NE 4 th St., Grand Rapids, MN (218) East Highway 2, Grand Rapids, MN (218) East Highway 2, Grand Rapids, MN (218) Lake Avenue South, Duluth, MN 5582 (218) Minnesota Drive, Brainerd, MN 5641 (218) RMB Environmental Laboratories, Inc. 2 of Loon Lake