Lake Hubert CROW WING COUNTY

Transcription

1 Lake Hubert CROW WING COUNTY Lake Water Quality Summary Lake Hubert is located two miles southeast of Nisswa, Minnesota, in Crow Wing County. It is oval-shaped and covers 1,287 acres. According to a 1942 DNR report, Lake Hubert had no normal outlet. In August 1939, a diversion ditch from Clark Lake was constructed to raise the then low level of Lake Hubert by flow from Clark Lake. The outflow from Lake Hubert now passes through Clark Lake and on to the Gull River. The Gull River eventually joins the Mississippi River. A small stream from Little Hubert Lake is the only inlet to Lake Hubert. Water quality data have been collected on Lake Hubert since These data show that the lake is mesotrophic (TSI 43). Mesotrophic lakes are commonly found in north-central Minnesota and have clear water with occasional algal blooms in late summer (page 9). The Lake Hubert Conservation Association has been involved in numerous activities including water quality monitoring, education, Healthy Lakes Initiative, promoting safety, promoting good fishing, and distributing newsletters. Table 1. Lake Hubert location and key physical characteristics. Location Data MN Lake ID: County: Crow Wing Ecoregion: Northern Lakes and Forest Major Drainage Basin: Upper Mississippi River Latitude/Longitude: / Invasive Species: Curly-Leaf pondweed Physical Characteristics Surface area (acres): 1,287 Littoral area (acres): 465 % Littoral area: 36% Max depth (ft), (m): 83 (ft), 25.3 (m) Inlets: 1 Outlets: 1 Public Accesses: 1 Table 2. Availability of primary data types for Lake Hubert. Data Availability Transparency data Excellent data source from , 1984, Chemical data Inlet/Outlet data Excellent data source from , 1984, 1989, , 2006, Not available. Recommendations For recommendations refer to page 18. RMB Environmental Laboratories, Inc. 1 of Lake Hubert

2 Lake Map Figure 1. Map of Lake Hubert with 2010 aerial imagery and illustrations of lake depth contour lines, sample site locations, inlets and outlets, and public access points. The light green areas in the lake illustrate the littoral zone, where the sunlight can usually reach the lake bottom, allowing aquatic plants to grow. Table 3. Monitoring programs and associated monitoring sites. Monitoring programs include the Minnesota Thirty Lakes Watershed District (TLWD) Citizen Lake Monitoring Program (CLMP) Lake Site Depth (ft) Monitoring Programs CLMP: CLMP: CLMP: CLMP: CLMP:1995, , * Primary site 80 CLMP: ; TLWD: , 1984, 1989, , 2006, 2009, CLMP: ; TLWD: CLMP: , 2012 RMB Environmental Laboratories, Inc. 2 of Lake Hubert

3 Average Water Quality Statistics The information below describes available chemical data for Lake Hubert from , 1984, 1989, , 2006, 2009, and (Table 4). Data for all parameters are from the primary site 206. 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. 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) > 40 3 Chlorophyll a (ug/l) > 14 Chlorophyll a max (ug/l) 7 < 15 Secchi depth (ft) < 1.4 Dissolved oxygen Total Kjeldahl Nitrogen (mg/l) Dimictic see page 8 Interpretation Results are within the expected range for the ecoregion. Dissolved oxygen depth profiles show that the deep areas of the lake are anoxic in late summer < 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) Slightly above the expected range for the ecoregion. Total Suspended Solids (mg/l) 1.8 <1 2 Indicates low suspended solids and clear water. Conductivity (umhos/cm) Within the expected range for the ecoregion. Total Nitrogen : Total Phosphorus 29:1 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 Lake Hubert

4 Water Quality Characteristics - Historical Means and Ranges Table 5. Water quality means and ranges for primary sites. Parameters Primary Site 206 Total Phosphorus Mean (ug/l): 16.9 Total Phosphorus Min: 7 Total Phosphorus Max: 46 Number of Observations: 44 Chlorophyll a Mean (ug/l): 3.4 Site 205 Site 207 Chlorophyll-a Min: < 1 Chlorophyll-a Max: 7 Number of Observations: 43 Secchi Depth Mean (ft): Secchi Depth Min: Secchi Depth Max: Number of Observations: Figure Figure 2. Lake 2. Lake Hubert insert total total phosphorus, phosphorus, chlorophyll chlorophyll a, and a and transparency transparency historical historical ranges. ranges. The The arrow 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 206). xxx). Figure Figure adapted adapted after Moore and Thornton, [Ed.] Lake and Reservoir Restoration Guidance Manual. (Doc. No. EPA 440/ ) after Moore and Thornton, [Ed.] Lake and Reservoir Restoration Guidance Manual. (Doc. No. EPA 440/ ) RMB Environmental Laboratories, Inc. 4 of Lake Hubert

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 Lake Hubert ranges from 9.0 to 18.0 feet at the primary site 206. All of the sites seem to have relatively similar transparency results. You would expect the best transparency results to be found in the deepest areas of the lake. The sites appear to follow the same pattern of ups and downs, which illustrates seasonal variability. Transparency monitoring should be continued annually at site 206 in order to track water quality changes. Secchi Depth (ft) Annual Mean Transparency Site 206, primary Site 207 Site 208 Annual Mean Figure 3. Annual mean transparency compared to long-term mean transparency. Lake Hubert transparency ranges from 8 to 21.9 ft at the primary site (206). Figure 4 shows the seasonal transparency dynamics. The maximum Secchi reading is usually obtained in early summer. Lake Hubert transparency is high in May and June, and then declines through August. 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 that 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 Lake Hubert

6 25 Seasonal Transparency Dynamics Secchi Depth (ft) Poly. (Mean) Figure 4. Seasonal transparency dynamics and year to year comparison (Primary Site 206). 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. Lake Hubert was rated as being "not quite crystal clear" 91% of the time by samplers at site 203 between 2003 and 2012 (Figure 5). Physical Appearance Rating 6% 3% 3% Crystal clear water 91% Not quite crystal clear a little algae visible 6% 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 91% Figure 5. Lake Hubert physical appearance ratings by samplers. RMB Environmental Laboratories, Inc. 6 of Lake Hubert

7 As the Secchi depth decreases, the perception of recreational suitability of the lake decreases. Lake Hubert was rated as having "very minor aesthetic problems" 87% of the time from (Figure 6). Recreational Suitability Rating 10% 3% 3% Beautiful, could not be better 87% Very minor aesthetic problems; excellent for swimming, boating 10% Swimming and aesthetic enjoyment of the lake slightly impaired because of algae levels 0% Desire to swim and level of enjoyment of the lake substantially reduced because of algae levels 87% 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 Lake Hubert is phosphorus limited, which means that algae and aquatic plant growth is dependent upon available phosphorus. Total phosphorus was evaluated in Lake Hubert in , The data do not indicate much seasonal variability. The majority of the data points fall into the mesotrophic range (Figure 7). Some data points drop into the oligotrophic range and occasionally the phosphorus was high into the eutrophic range. Total Phosphorus (ug/l) Eutrophic Mesotrophic Oligotrophic Total Phosphorus Phosphorus should continue to be monitored to track any future changes in water quality. Figure 7. Historical total phosphorus concentrations (ug/l) for Lake Hubert site 206. RMB Environmental Laboratories, Inc. 7 of Lake Hubert

8 Chlorophyll a Chlorophyll a is the pigment that makes plants and algae green. Chlorophyll a is tested in lakes to deter mine 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 Minor Algae Chlorophyll a was evaluated in Lake Hubert at site 206 in Figure 8. Chlorophyll a concentrations (ug/l) for Lake Hubert at site , and , (Figure 8). Chlorophyll a concentrations remained well below 10 ug/l on all sample dates indicating clear water most of the summer. There was not much variation over the years monitored and chlorophyll a concentrations remained relatively steady over the summer. 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 fisheries. Lake Hubert is a deep lake with a maximum depth of 83 feet. Figure 9 displays a dissolved oxygen profile from August of The thermocline in August was around 31 feet, which means that game fish, especially cisco, will not be present deeper than 31 feet. Figure 9. Dissolved oxygen profile for Lake Hubert in RMB Environmental Laboratories, Inc. 8 of Lake Hubert

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 Lake Hubert falls into the mesotrophic range (Figure 9). There is good agreement between the TSI for phosphorus, chlorophyll a and transparency, indicating that these variables are strongly related (Table 6). Lake Hubert 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 algal blooms in late summer (Table 7). They are also good for walleye fishing. Table 6. Trophic State Index for site 206. Trophic State Index Site 206 TSI Total Phosphorus 45 TSI Chlorophyll-a 43 TSI Secchi 40 TSI Mean 43 Trophic State: Mesotrophic Numbers represent the mean TSI for each parameter. Hypereutrophic Eutrophic Mesotrophic Oligotrophic Figure 10. Trophic state index chart with corresponding trophic status. 0 Table 7. Trophic state index attributes and their corresponding fisheries and recreation characteristics. TSI Attributes Fisheries & Recreation <30 Oligotrophy: Clear water, oxygen throughout Trout fisheries dominate the year at the bottom of the lake, very deep cold water 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 Lake Hubert

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. Lake Hubert had enough data to perform a trend analysis for Transparency (Table 8). The data was analyzed using the Mann Kendall Trend Analysis. Table 8. Trend analysis for site 207. Lake Site Parameter Date Range Trend Probability 207 Transparency No trend -- All Sites Chlorophyll a -- Insufficient data -- All Sites Total Phosphorus -- Insufficient data Lake Hubert Transparency Trend 25 Secchi Depth (ft) Figure 11. Transparency (feet) trend for site 207 from Lake Hubert shows no statistical evidence of water quality trends (Figure 11). That means that the water quality is stable. Transparency monitoring should continue so that this trend can be tracked in future years. RMB Environmental Laboratories, Inc. 10 of Lake Hubert

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. Lake Hubert is in the Northern Lakes and Forest Ecoregion. The mean total phosphorus and chlorophyll a readings for Lake Hubert are slightly better than the ecoregion ranges (Figure 13). Figure 12. Minnesota Ecoregions Total Phosphorus (ug/l, ppb) Chlorophyll-a (ug/l, ppb) Secchi depth (ft) increased algae crystal clear 0 NLF Ecoregion Hubert 0 NLF Ecoregion Hubert 25 NLF Ecoregion Lake Hubert Figure 13. Lake Hubert ranges compared to Northern Lakes and Forest Ecoregion ranges. The Lake Hubert total phosphorus ranges are from 29 data points collected in May-September of 1974 and and chlorophyll a ranges are from 28 data points collected in May-September of 1974 and The Lake Hubert Secchi depth range is from 50 data points collected in May-September of RMB Environmental Laboratories, Inc. 11 of Lake Hubert

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 Crow Wing River 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). This major watershed is made up of 136 minor watersheds. Lake Hubert is located in minor watershed (Figure 13). Figure 14. Crow Wing 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. Lake Hubert falls within 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 Lake Hubert s watershed, containing all the lakesheds upstream of the Lake Hubert lakeshed, see page 17. The data interpretation of the Lake Hubert lakeshed includes only the immediate lakeshed as this area is the land surface that flows directly into Lake Hubert. Figure 16. Lake Hubert lakeshed ( ) with land ownership, lakes, wetlands, and rivers illustrated. RMB Environmental Laboratories, Inc. 12 of Lake Hubert

13 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. Lake Hubert lakeshed vitals table. Lakeshed Vitals Rating Lake Area 1287 acres descriptive Littoral Zone Area 465 acres descriptive Lake Max Depth 81 feet descriptive Lake Mean Depth feet Water Residence Time NA NA Miles of Stream 0.2 descriptive Inlets 1 Outlets 1 Major Watershed 12 Crow Wing River descriptive Minor Watershed descriptive Lakeshed descriptive Ecoregion Northern Lakes and Forests descriptive Total Lakeshed to Lake Area Ratio (total lakeshed includes lake area) 2:1 Standard Watershed to Lake Basin Ratio (standard watershed includes lake areas) 3:1 Wetland Coverage (NWI) 2.9% Aquatic Invasive Species Public Drainage Ditches Public Lake Accesses 1 Curly-leaf pondweed None Miles of Shoreline 6.0 descriptive Shoreline Development Index 1.2 Public Land to Private Land Ratio 0.1:1 Development Classification General Development Miles of Road 4.4 descriptive Municipalities in lakeshed Nisswa County Forest Management: Forestry Practices Feedlots None Individual Subsurface Sewage Treatment Sewage Management Systems (Inspection and assessment required for all permits and property transfers within the Shoreland Protection Zone) Lake Management Plan 2005 Lake Vegetation Survey/Plan None RMB Environmental Laboratories, Inc. 13 of Lake Hubert

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. 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 Lake Hubert s lakeshed. The National Land Cover Dataset has online records of land cover statistics from years 2001 and Although some of this data is 12 years old, it is the most recent data set that is comparable. Table 10 Figure 17. Lake Hubert lakeshed ( ) land cover ( describes Lake Hubert s lakeshed land cover statistics and percent change from 2001 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 transitions occurring within the last 12 years within the lakeshed. RMB Environmental Laboratories, Inc. 14 of Lake Hubert

15 Table 10. Lake Hubert s lakeshed land cover statistics and % change from 2001 to 2006 ( % Change Land Cover Acres Percent Acres Percent 2001 to 2006 Agriculture No Change Forest % Increase Grass/Shrub/Wetland % Decrease Water % Decrease Urban % Increase Impervious Intensity % % Increase % Increase No Change No Change Total Area Total Impervious Area (Percent Impervious Area Excludes Water Area) % Increase Demographics Lake Hubert is classified as a general development lake. General development lakes usually have more than 225 acres of water per mile of shoreline, 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 6 below. Compared to Crow Wing County as a whole, Lake Edward Township has a slightly lower extrapolated growth projection, while the city of Nisswa has a higher extrapolated growth projection. (Figure 18). 40% Population Growth Projection Percentage of 2006 Population 30% 20% 10% 0% Lake Edward Township; 2006 population: 2,049 City of Nisswa; 2006 population: 2,047 Crow Wing County; 2006 population: 61, Extrapolation Figure 18. Population growth projection for Lake Edward Township, the city of Nisswa, and Crow Wing County (source: RMB Environmental Laboratories, Inc. 15 of Lake Hubert

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 Lake Hubert s lakeshed is privately owned and composed primarily of forested uplands (Table 11). In addition, a large portion of land found within the other category was verified as being forested. 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 (31%) 66% Public (3%) 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 <1 0 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 Lake Hubert

17 Table 12. 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% % n/a Full Restoration > 60% 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. Lake Hubert s lakeshed is classified with having 67.5% of the watershed protected and 1.7% 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. Figure 20 displays the upstream lakesheds that contribute water to the lakeshed of interest. All of the land and water area in this figure has the potential to contribute water to Lake Hubert, whether through direct overland flow or through a creek or river. There are 2 upstream lakesheds of the Lake Hubert lakeshed. Percent of the Watershed Protected 0% 75% 100% Lake Hubert (67.5%) Percent of the Watershed with Disturbed Land Cover 0% 25% 100% Lake Hubert (1.7%) Figure 19. Lake Hubert s lakeshed percentage of watershed protected and disturbed. Figure 20. Upstream lakesheds that contribute water to the Lake Hubert lakeshed. Color-coded based on management focus (Table 12). RMB Environmental Laboratories, Inc. 17 of Lake Hubert

18 Status of the Fishery (DNR, as of 08/20/2007) Hubert Lake is 1,294 acres in size and is located one mile southeast of Nisswa in Crow Wing County. A public access is located on the west side of the lake. Maximum depth is 83' and 36% of the lake is 15' deep or less. The lake is heavily developed with 28.1 homes/cabins per shoreline mile and 5 resorts/camps of various types and sizes as of Shoreline substrate is composed primarily of sand with occasional areas of gravel, rubble, or boulders. The aquatic plant community is relatively diverse with 22 species observed. Emergent plants such as bulrush are important for shoreline protection, maintaining water quality, and provide essential spawning habitat for bass and panfish species. Submerged plants provide food and cover needed by fish and other aquatic species. Walleye fingerlings are stocked every third year at a rate of 0.5 lbs per littoral acre. The 2007 catch was 7.1/gill net which is average for similar type lakes. Eleven year classes were represented with year classes where stocking was done accounting for 87% of the walleye catch. No walleyes less than 15" were sampled resulting in a relatively good average length and weight of 19.8" and 2.8lbs. The northern pike catch of 4.3/gill net was average for similar lakes and is typical of past catches on Hubert. Average length and weight were 19.6" and 1.8 lbs. with 14% of these fish measuring at least 24". A 12" maximum regulation for bass was implemented in 2005, requiring the immediate release of all large and smallmouth bass 12" and larger. While it is too early to evaluate the effectiveness of this regulation, the populations of both species appear to be in good shape. Spring electrofishing resulted in a largemouth bass catch rate of 56/hr with an average length of 11.0" and 29% measuring at least 12". Smallmouth bass were caught at a rate of 11/hr and had a mean length of 16.3" with 91% measuring at least 12". Black crappie and bluegill were present in average numbers when compared to trap net catches in similar lakes. Forage species in the lake include yellow perch, cisco, and white suckers. No cisco or suckers were caught in 2007 and the yellow perch catch of 0.4/gill net is below average and the lowest to date for Hubert. See the link below for specific information on gillnet surveys, stocking information, and fish consumption guidelines. Key Findings / Recommendations Monitoring Recommendations Transparency monitoring at site 206 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 at site 206, as the budget allows, to track trends in water quality. Additional sampling could include monitoring the lake inlet from Little Hubert to assess changes in the nutrient load from upstream lakesheds. Overall Summary Lake Hubert is a mesotrophic lake (TSI = 43) with no evidence of a trend in water quality. The total phosphorus, chlorophyll a ranges are within or slightly better than the ecoregion ranges. Three percent (3%) of the lakeshed is public land and most of the private land use is categorized as forested uplands (10.7%) (Table 11). This land use category is generally good for water quality. Only 1.6% of the private land is categorized as developed. When considering the MN DNR water RMB Environmental Laboratories, Inc. 18 of Lake Hubert

19 quality modeling, the threshold where water quality tends to decline is 25%, and Lake Hubert is at 1.7% (Figure 19). Lake Hubert has 2 additional lakesheds that flow into it, but it still has a relatively small drainage area. This means that water flowing in from other lakesheds or overland flow, along with land practices around the lake are the main impacts to the lake s water quality. Ciscos (Coregonus artedi) can be an early indicator of eutrophication in a lake because they require cold hypolimnetic temperatures and high dissolved oxygen levels. The DNR Fisheries survey in 2007 reported that although ciscos are forage fish for Lake Hubert, there were no ciscos caught that year. Priority Impacts to the Lake While only 1.7% of the lakeshed is developed, much of this development occurs along the shorelines of Hubert Lake itself as it is heavily developed within the first tier. The DNR fisheries report says that the lake is heavily developed with 28.1 homes/cabins per shoreline mile and 5 resorts/camps of various types and sizes as of There has been an increase in urban and impervious surface areas between 2001 and The goal should be to minimize any additional first and second tier development and impervious surface area. Mean chloride data from site 206 in 2002 is higher (3.4 mg/l) than the excepted range for the ecoregion (<1-2 mg/l). Chloride does not affect plant and algae growth at this level, but it can be used as an indicator of possible water pollution from human activity. The most likely sources of chloride, and other containments, are septic systems, animal waste, potassium chloride fertilizer (potash), and road-salting chemicals. Best Management Practices Recommendations The management focus for Hubert Lake should be to protect the current water quality and the lakeshed. Efforts should be focused on managing and/or decreasing the impact caused by additional development, including second tier development, and impervious surface area. Project ideas include protecting land with conservation easements, smart development, shoreline restoration, rain gardens, and septic system maintenance. There are some large undeveloped parcels on the south end of the lake that would be good candidates for conservation easements or wildlife management areas. The shoreline in that location is ringed with wetlands, and is most likely good quality fish and wildlife habitat. Project Implementation The best management practices above can be implemented by a variety of entities. Some possibilities are listed below. Individual property owners Shoreline restoration Rain gardens Aquatic plant bed protection (only remove a small area for swimming) Lake Associations Lake condition monitoring Ground truthing visual inspection upstream on stream inlets Shoreline inventory study by a consultant RMB Environmental Laboratories, Inc. 19 of Lake Hubert

20 Soil and Water Conservation District (SWCD) & Natural Resources Conservation Service (NRCS) Shoreline restoration Stream buffers Work with farmers to o Restore wetlands o Implement conservation farming practices o Land retirement programs such as Conservation Reserve Program 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. Since conversion of small cabins to large lake homes could be a future issue, strengthening county shoreline ordinances such as set-backs, impervious surface limits and shoreline alteration (installation of retaining walls and removing trees) will help to protect water quality. Organizational contacts and reference sites Lake Hubert Conservation Association Crow Wing County Land Services Department Crow Wing Soil and Water Conservation District DNR Fisheries Office Regional Minnesota Pollution Control Agency Office Regional Board of Soil and Water Resources Office P O Box 1352, Lake Hubert, MN Laurel Street, Suite 14, Brainerd, MN Laurel Street, Suite 13, Brainerd, MN (218) Minnesota Drive, Brainerd, MN (218) College Road, Suite 105, Baxter, MN (218) Minnesota Drive, Brainerd, MN (218) RMB Environmental Laboratories, Inc. 20 of Lake Hubert