North Long Lake CROW WING COUNTY

Transcription

1 North Long Lake CROW WING COUNTY Lake Water Quality Summary North Long Lake is located about eight miles north of Brainerd in Crow Wing County. It covers 6,143 acres, which places it in the upper 5% of lakes in Minnesota in terms of size. North Long Lake has three distinct basins: a western basin with a maximum depth of 25 feet, a main basin with a maximum depth of 97 feet, and an eastern basin with a maximum depth of 68 feet. It has one main inlet and one main outlet in addition to some intermittent tributaries, which classifies it as a drainage lake. North Long Lake is located in the Crow Wing River Major Watershed. Sugar Bush Creek flows north from North Long Lake into Round Lake, and Bishop Creek flows from Round Lake into Gull Lake. From Gull Lake the water flows south through a series of lakes to the Crow Wing River. The Crow Wing River joins the Mississippi River southwest of Brainerd. Water quality data have been collected on North Long Lake since 1973 (Tables 2-3). These data show that the lake is mesotrophic (page 9). Mesotrophic Lakes have clear water most of the summer with occasional algae blooms. The North Long Lake Association's purpose is to support the residents and guests of North Long Lake and the Brainerd, Minnesota, lakes area. The Association has been involved in numerous activities including water quality monitoring, education, and clean water legislative issues. Table 1. North Long 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: None as of 2011 Physical Characteristics Surface area (acres): 6,143 Littoral area (acres): 3,905 % Littoral area: 64% Max depth (ft), (m): 97, 29.6 Table 2: Availability of data and an observation of the quantity of sample points. Data Availability Transparency data Chemical data Inlets: 1 County Ditch 13 plus some intermittent tributaries Outlets: 1 Sugar Bush Creek Public Accesses: 4 Numerous yearly Secchi readings from through the MPCA CLMP program. Extensive Phosphorus and Chlorophyll a data have been collected. Inlet/Outlet data No inlet or outlet data exist for North Long Lake. Recommendations For recommendations refer to page 18. RMB Environmental Laboratories, Inc. 1 of North Long Lake

2 Lake Map Figure 1. Map of North Long Lake 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 Citizen Lake Monitoring Program (CLMP), Minnesota Pollution Control Agency (MPCA), Thirty Lakes Watershed District (TLWD), and RMB Environmental Laboratories Lake Monitoring (RMBEL). Basin Lake Site Depth (ft) Monitoring Programs East TLWD: , 1981, 1984, 1989; MPCA: 1998; CLMP: 2011 East 202*primary 30 CLMP: ; RMBEL: East CLMP: 1984, Main MPCA: 1981, 1998 Main CLMP: ; TLWD: 2011 Main CLMP: 1984, , Main CLMP: Main CLMP: , , , , 2009, 2011 Main CLMP: 1991 Main 210* primary 97 MPCA: 1998; TLWD: , 1984, 1989, ; RMBEL: West 204* primary 25 CLMP: 1975, 1991, , ; MPCA: 1981, 1998; RMBEL: West CLMP: RMB Environmental Laboratories, Inc. 2 of North Long Lake

3 Average Water Quality Statistics The information below describes available chemical data for North Long 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 1981 and 1998 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. Parameter East Bay Main Bay West Bay Ecoregion Range 1 Interpretation Total phosphorus (ug/l) Results are within the Chlorophyll a (ug/l) Chlorophyll a max (ug/l) <15 Secchi depth (ft) Dissolved oxygen Total Kieldahl Nitrogen (mg/l) Dimictic see page 8 Dimictic see page 8 Polymictic see page 8 expected range for the ecoregion and indicative of a mesotrophic lake. For more on mesotrophic lakes, see page 9. 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 Characteristic of a hard water lake. Lake water ph less than 6.5 can affect fish spawning and the solubility of metals in the water. Chloride (mg/l) Slightly above the ecoregion average, which could be due to the proximity of Hwy 371 (road salts), but still considered low level. Total Suspended Solids <1-2 Within the expected range for (mg/l) the ecoregion. Conductivity (umhos/cm) Within the expected range for the ecoregion. Total Nitrogen :Total Phosphorus 35:1 32:1 42:1 25:1 35:1 The lake is phosphorus limited, which means that algae growth is limited by the amount of phosphorus in the lake. 1 The ecoregion range is the 25 th -75 th percentile of summer means from ecoregion reference lakes 2 Chlorophyll a measurements have been corrected for pheophytin Units: 1 mg/l (ppm) = 1,000 ug/l (ppb) RMB Environmental Laboratories, Inc. 3 of North Long Lake

4 Water Quality Characteristics - Historical Means Table 5. Water quality means and ranges for primary sites. Parameters East Basin Site 202 Site 206 Main Basin Site 208 Site 210 West Basin Site 204 Total Phosphorus Mean (ug/l): Total Phosphorus Min: Total Phosphorus Max: Number of Observations: Chlorophyll a Mean (ug/l): Chlorophyll-a Min: Chlorophyll-a Max: Number of Observations: Secchi Depth Mean (ft): Secchi Depth Min: Secchi Depth Max: Number of Observations: Figure 2. North Long Lake total phosphorus, chlorophyll a and transparency historical ranges. The arrow represents the range and the black dot represents the historical mean (Primary Site 210). Figure adapted after Moore and Thornton, [Ed.] Lake and Reservoir Restoration Guidance Manual. (Doc. No. EPA 440/ ) RMB Environmental Laboratories, Inc. 4 of North Long 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. All three basins are relatively similar in transparency (Figure 3). The east basin has consistently the highest transparency. Transparency monitoring should be continued annually at all sites in order to track water quality changes in the future. 20 Transparency: Annual Means Secchi Depth (ft) West Basin, Site 204 Main Basin, Site 210 East Basin, Site Figure 3. Annual transparency means for North Long Lake monitoring sites. North Long Lake transparency ranges from 5 to 35 ft at site 210 in the main basin. Figure 4 shows the seasonal transparency dynamics. North Long Lake transparency is highest in May and then it declines slightly throughout the rest of the summer. In October, the transparency rebounds to near spring levels. Transparency in some lakes varies throughout the summer, while in others it stays relatively constant. 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 North Long Lake

6 25 20 Seasonal Transparency Dynamics Secchi Depth (ft) Figure 4. Seasonal transparency dynamics and year-to-year comparison (site 210). 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. All bays of North Long Lake were rated as "crystal clear" or "not quite crystal clear" % of the time (Figure 5). Physical Appearance Rating Crystal clear water Not quite crystal clear a little algae visible Definite algae green, yellow, or brown color apparent High algae levels with limited clarity and/or mild odor apparent Severely high algae levels 6% 5% 30% 34% 27% 70% 60% 68% Site 206 Site 204 Site 205 East Basin West Basin Main Basin Figure 5. Physical appearance rating for all three basins, as rated by the volunteer monitor. RMB Environmental Laboratories, Inc. 6 of North Long Lake

7 As the Secchi depth decreases, the perception of recreational suitability of the lake decreases. The basins differ somewhat in rating; however, all are rated as "beautiful" or having "very minor aesthetic problems" % of the time (Figure 6). Recreational Suitability Rating Beautiful, could not be better Very minor aesthetic problems; excellent for swimming, boating Swimming and aesthetic enjoyment of the lake slightly impaired because of algae levels Desire to swim and level of enjoyment of the lake substantially reduced because of algae levels Swimming and aesthetic enjoyment of the lake nearly impossible because of algae levels 7% 6% 24% 3% 28% 93% Site 206 East Basin Figure 6. Recreational suitability rating for all three basins, as rated by the volunteer monitor. 70% Site 204 West Basin 69% Site 210 Main Basin Total Phosphorus North Long Lake is phosphorus limited, which means that algae and aquatic plant growth is dependent upon available phosphorus. Total phosphorus was evaluated in all three bays of North Long Lake in and All the sites have relatively similar phosphorus concentrations, with the exception of some high individual data points (Figure 7). The majority of the data falls into the mesotrophic range. Total Phosphorus (ug/l) Total Phosphorus East Bay Figure 7. Historical total phosphorus concentrations (ug/l) for North Long Lake. West Bay Main Bay RMB Environmental Laboratories, Inc. 7 of North Long 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) 14 Chlorophyll a East Bay 6 West Bay 4 Main Bay 2 Minor Algae 0 Figure 8. Historical chlorophyll a concentrations (ug/l) for North Long Lake. Chlorophyll a was evaluated in all three sites of North Long Lake in Chlorophyll a concentrations remained below 10 ug/l in all but two data points, indicating clear water most of the summer. The chlorophyll a concentrations stay relatively consistent throughout the summer, and are relatively similar for all three sites (Figure 8). 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. The main and east basins of North Long Lake are relatively deep, and dissolved oxygen profiles show that they stratify in the summer. The west basin is shallower and mixes throughout the summer on windy days (Figure 9). These results indicate that game fish will not be present below 10 meters (33 ft) in the main and east basins in mid-summer due to low oxygen levels. This occurrence is typical in mesotrophic Minnesota lakes Figure 9. Dissolved oxygen profile for North Long Lake on July 14, This is a representative profile for North Long Lake. RMB Environmental Laboratories, Inc. 8 of North Long 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. Table 6. Trophic State Index. Trophic State Index West Basin Main Basin East Basin TSI Total Phosphorus TSI Chlorophyll-a TSI Secchi TSI Mean Trophic State: Mesotrophic Mesotrophic Mesotrophic Numbers represent the mean TSI for each parameter. In order to standardize these three measurements to make them directly comparable, we convert them to a trophic state index (TSI). The mean TSI for North Long Lake indicates all basins are mesotrophic (Figure 10). There is good agreement between the TSI for phosphorus, chlorophyll a and transparency, indicating that these variables are strongly related. In addition, all three basins are relatively similar in TSI (Table 6). North Long Lake Hypereutrophic Eutrophic Mesotrophic Mesotrophic lakes (TSI 40-50) are characterized by moderately clear water most of the summer (Figure 10). "Meso" means middle or mid; therefore, mesotrophic means a medium amount of productivity. Mesotrophic lakes are commonly found in north-central Minnesota and have clear water with some algal blooms in late summer. Oligotrophic Figure 10. Trophic state index chart with corresponding trophic status. 0 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 North Long 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 North Long Lake. There was enough transparency data for all basins to perform trend analyses (Table 7). The data was analyzed using the Mann Kendall Trend Analysis. Table 7. Trend analysis for North Long Lake. Basin Lake Site Parameter Date Range Trend Probability West 204 Transparency No Trend -- West 204 Transparency Declining 90% Main 210 Transparency Declining 90% East 206 Transparency Improving 99.9% 25 Transparency Trend, West Bay, North Long Lake Secchi Depth (ft) Trend Trend Figure 11. Transparency trend for the North Long Lake west basin from There are a few different trends going on in North Long Lake. The west bay has no long-term trend from , but a declining short-term trend from (Figure 11). Runoff from highway 371 could be impacting the west basin. In the main basin there is a declining trend in transparency occurring since The east basin has an improving trend of approximately 2 feet in transparency from Transparency monitoring should continue in all basins so that these trends can be tracked in the future. RMB Environmental Laboratories, Inc. 10 of North Long 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. North Long Lake is in the Northern Lakes and Forests Ecoregion. The mean total phosphorus, chlorophyll a and transparency (Secchi depth) for the North Long Lake are within the expected ecoregion ranges (Fig. 13). In addition, all bays are very similar in water quality. Figure 12. Map of Minnesota with the seven ecoregions Total Phosphorus (ug/l, ppb) NLF Ecoregion North Long West North Long Main North Long East Chlorophyll-a (ug/l, ppb) a b c NLF Ecoregion North Long West North Long Main North Long East Secchi depth (ft) increased algae crystal clear Figures 13a-c North Long Lake ranges compared to Northern Lakes and Forest Ecoregion ranges. The North Long Lake total phosphorus and chlorophyll a ranges are from data points in each basin collected in May-September from The North Long Lake Secchi depth range is from data points in each basin collected in May-September from RMB Environmental Laboratories, Inc. 11 of North Long 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 Crow Wing 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 136 minor watersheds. North Long Lake is located in minor watershed (Figure 15). 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. North Long Lake 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 North Long Lake s full watershed, containing all the upstream lakesheds, see page 17. The data interpretation of the North Long Lake lakeshed is only the immediate lakeshed, not Figure 16. The North Long Lakeshed ( ). RMB Environmental Laboratories, Inc. 12 of North Long Lake

13 including the upstream lakesheds, as this area is the land surface that flows directly into North Long 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. North Long Lake lakeshed vitals table. Lakeshed Vitals Rating Lake Area 6,143 acres descriptive Littoral Zone Area 3,905 acres descriptive Lake Max Depth 97 ft. (29.6 m) descriptive Lake Mean Depth 16 ft. (4.9 m) Water Residence Time 6.4 years NA Miles of Stream 3.57 descriptive Inlets Outlets 1 County Ditch 13, plus intermittent tributaries 1 Sugar Bush Creek Major Watershed 12 - Crow Wing River descriptive Minor Watershed descriptive Lakeshed descriptive Ecoregion Northern Lakes and Forest 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 10% Aquatic Invasive Species None Public Drainage Ditches 1 County Ditch 13 Public Lake Accesses 4 Miles of Shoreline descriptive Shoreline Development Index 1.9 Public Land to Private Land Ratio 0.1:1 Development Classification General Development Miles of Road 22.8 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) None None RMB Environmental Laboratories, Inc. 13 of North Long 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. Figure 17. The North Long Lake ( ) lakeshed land cover ( 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. Phosphorus export, which is the main cause of lake eutrophication, depends on the type of land cover occurring in the lakeshed. Figure 17 depicts North Long Lake s lakeshed land cover. The University of Minnesota has online records of land cover statistics from years 1990 and 2000 ( Table 10 describes North Long 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 agriculture cover (70.3%); however, in acreage, forest cover has increased the most (562 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 North Long Lake

15 Table 10. North Long Lake lakeshed land cover statistics and % change from 1990 to 2000 ( % Change Land Cover Acres Percent Acres Percent 1990 to 2000 Agriculture % Decrease Forest 4, , % Increase Grass/Shrub/Wetland 1, , % Decrease Water 6, , % Decrease Urban % Increase Impervious Intensity % 0 12, , % Decrease % Increase % Increase % Increase % Increase % Increase % Increase Total Area 12,970 12,970 Total Impervious Area (Percent Impervious Area Excludes Water Area) % Increase Demographics North Long 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 Compared to Crow Wing County as a whole, Lake Edward Township has a slightly lower extrapolated growth projection (Figure 18) Figure 18. Population growth projection for the city of Nisswa and Crow Wing County. Figure excludes First Assessment, which lacks population data, as well as Cass County cities and townships (source: phy.state.mn.us/reso urce.html?id=19332). Percentage of 2006 Population 40% 30% 20% 10% 0% Population Growth Projection Lake Edward Township; 2006 population: 2,049 Crow Wing County; 2006 population: 61, Extrapolation RMB Environmental Laboratories, Inc. 15 of North Long Lake

16 North Long Lake 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 North Long Lake s lakeshed is made up of private forested uplands (Table 11). 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 (46.5%) 49% Public (4.5%) Developed Agriculture Forested Uplands Other Wetlands Open Water County State Federal Land Use (%) 4% 1% 21% 13% 7.5% 49% 0% 4.5% 0% 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 North Long 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. North Long Lake is classified with having 54.4% of the watershed protected and 4.9% of the watershed disturbed (Figure 19). Therefore, North Long Lake 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 North Long Lake, whether through direct overland flow or through a creek or river. All of the 5 upstream lakesheds have the same management focus (protection). Percent of the Watershed Protected 0% 75% 100% North Long Lake (54.4%) Percent of the Watershed with Disturbed Land Cover 0% 25% 100% North Long Lake (4.9%) Figure 19. North Long Lake lakeshed s percentage of watershed protected and disturbed. Figure 20. Upstream lakesheds that contribute water to the North Long lakeshed. Color-coded based on management focus (Table 12). RMB Environmental Laboratories, Inc. 17 of North Long Lake

18 North Long Lake, Status of the Fishery (as of 07/24/2006) North Long Lake, at 5,998 acres, is one of the largest and most popular lakes in the Brainerd area. The lake is heavily developed with 21.7 homes/cabins per shoreline mile as of 1993 in addition to several resorts and campgrounds of various types and sizes. There are 4 public accesses providing many recreational opportunities. The maximum depth is 97' and about 65% of the lake is 15' deep or less. Shallow water substrates consist primarily of sand, although areas of silt, gravel, and rubble are also present. The aquatic plant community is quite diverse with 43 species present and is critical to maintaining good water quality and healthy fish populations. 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. The 2006 walleye catch of 10.1/gill net is above average for this and similar lakes. Average length and weight were similar to the previous netting in 2000 at 16.2" and 1.7lbs. Age 3-5 fish ( year classes) accounting for 62% of the gill net catch. These fish measured approximately 12" to 20" at the time of the survey. In recent years walleye have been stocked annually as fry. These fry-stocked year classes accounted for 59% of the catch, suggesting that fry stocking has been successful. In general, there are several abundant year classes from that should provide quality fishing now and in the near future. Northern pike abundance remained above average at 9.5/gill net in Average length and weight were similar to 2000 at 22.5" and 2.6 lbs with 31% measuring at least 24". The largemouth bass catch was typical of past catches on North Long and a bit higher than on similar lakes. Spring electrofishing resulted in a largemouth bass catch rate of 88.3/hr with an average length of 11.6" and 43% measuring at least 12". The bluegill catch was the lowest to date, but at 43.5/trap net, it is above average compared to similar lakes. Black crappies were present in average numbers (0.7/gill net and 0.4/trap net) when compared to past catches on North Long and similar lakes. Tullibee and yellow perch are important forage species for the lake's game fish. The tullibee catch was above average at 6.7/gill net. Yellow perch abundance has varied considerably in the past, ranging from 5.6 to 24.9/gill net. The 2006 catch of 16.7/gill net was typical for this and similar lakes. See the link below for specific information on gillnet surveys, stocking information, and fish consumption guidelines. Key Findings / Recommendations Monitoring Recommendations Transparency monitoring should be continued annually in each bay at sites 204, 210, 202. 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 in each bay, as the budget allows, to track future water quality trends. RMB Environmental Laboratories, Inc. 18 of North Long Lake

19 Overall Conclusions Overall, North Long Lake has good water quality, and is in fair shape for lakeshed protection. It is a mesotrophic lake (TSI=42). The west bay and main bay have declining transparency in the last decade, while the east bay is improving. Ten percent (5%) of the lakeshed is in public ownership, and 54% of the lakeshed is protected, while 5% of the lakeshed is disturbed (Figure 19). Priority Impacts to the lake The priority impact to North Long Lake is the surrounding development and any future development. Even though a very small percentage of the lakeshed is disturbed (5%), this disturbance is focused right around the shoreline as heavy development. As of 1993, North Long Lake had 21.7 homes/cabins per shoreline mile in addition to several resorts and campgrounds of various types and sizes. From , the urban area in the lakeshed increased by 207 acres and the impervious area increased by 100 acres (Table 10). The agricultural and grassland/wetland acreages decreased over the past 20 years, being replaced by second tier development. The concern with increased development is the increased impervious surfaces, such as roofs, driveways, and well groomed lawns. Phosphorus loading will increase when land use changes to development. A way to mitigate this issue is through the installation of Best Management Practices (BMPs). Chloride monitoring shows that the west bay of North Long Lake has a non-natural chloride source. This is most likely runoff from highway 371. Chloride is higher than what is expected for lakes in the area, but it is not as high as Twin Cities lakes or the MCPA standard. See the BMP section for follow-up on this issue. An additional potential impact to the west bay of North Long Lake is the shallow nature of the bay. Because the west bay is shallow (majority of area less than 15 feet deep), it is very important to protect native aquatic plant beds to preserve fish habitat and water clarity. Large boat motors can churn up the sediment and re-suspend phosphorus, causing algae blooms. In addition, because the west bay is shallow, it could be subject to internal loading. Internal loading is when the phosphorus that is in the lake sediment re-suspends into the water column, feeding algae and plants. Phosphorus re-suspends when large boat motors churn up the sediment, and when the lake has a few calm days which allows it to loosely stratify, and then windy days, which mixes the water back up. Best Management Practices Recommendations The management focus for North Long 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 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 lake. Road salt should be applied on 371 following the MPCA s best management practices: Monitoring the runoff from 371 during spring thaw could better pinpoint if that is the chloride source or not. Native aquatic plants stabilize the lake s sediments and tie up phosphorus in their tissues. When aquatic plants are uprooted from a shallow bay such as the west bay, the lake bottom is disturbed, and the phosphorus in the water column gets used by algae instead of plants. This contributes to greener water and more algae blooms. Protecting native aquatic plant beds will ensure a healthy lake and healthy fishery. RMB Environmental Laboratories, Inc. 19 of North Long Lake

20 Studies have shown that large boat motors can re-suspend the phosphorus from the lake s sediment and cause algae blooms. Boaters should be encouraged to drive slowly through areas shallower than 10 feet. Future Studies Future studies that would better pinpoint the impacts on the lake include a shoreline inventory, spring thaw monitoring for chloride, internal loading monitoring in the west bay, and a watershed flow analysis. The shoreline inventory would consist of boating around the lake and rating each parcel as to how much of the frontage has a vegetative buffer. Spring thaw monitoring for chloride would involve taking water samples at culverts and areas of runoff from highway 371 to see if that is a major source of chloride to the lake. Monitoring for internal loading involves collecting hypolimnion water samples (water samples taken 1 foot above the lake s bottom) and corresponding dissolved oxygen profiles. A watershed flow analysis would be done using GIS software to see the areas of heaviest runoff into the lake. This analysis would also help pinpoint the best locations for rain gardens and shoreline restoration projects. Organizational contacts and reference sites North Long Lake Association Thirty Lakes Watershed District Crow Wing Soil and Water Conservation District 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 54, Merrifield, Minnesota Crow Wing County Land Services Building 322 Laurel St. Suite 13, Brainerd, MN (218) Crow Wing County Land Services Building 322 Laurel St. Suite 13, Brainerd, MN Crow Wing County Land Services Building 322 Laurel St. Suite 13, Brainerd, MN Minnesota Drive, Brainerd, MN (218) College Road, Suite 105, Baxter, MN (218) Minnesota Drive, Brainerd, MN (218) 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 North Long Lake