Lake Ossawinnamakee CROW WING COUNTY

Transcription

1 Lake Ossawinnamakee CROW WING COUNTY Lake Water Quality Summary Lake Ossawinnamakee is located by Breezy Point, MN in Crow Wing County. It is an elongated L shape basin that covers 689 acres (Table 1). Lake Ossawinamakee has six inlets and one outlet, which classify it as a drainage lake. Four of the inlets drain from bordering lakes, Clear Lake, Kimble Lake, Rat Lake, and Pelican Lake. The additional inlets drain from small areas of land and wetlands on the south side of the lake. Water flows out of Lake Ossawinnamakee into the Pelican Brook, located on the far east shore of the lake. The Pelican Brook joins the Pine River about 3.5 miles southeast of the outlet. Water quality data have been collected on Lake Ossawinnamakee in 1975, (Tables 2-3). These data show that the lake is at the oligotrophic/mesotrophic border (TSI 39-41), which is characteristic of clear water throughout the summer and excellent recreational opportunities. The Lake Ossawinnamakee Property Owners Association formed in They monitor water quality, build and maintain loon nests, and maintain buoys, as well as additional activities. There is also an active Lake Ossawinnamakee Improvement District. Table 1. Lake Ossawinnamakee 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: Eurasian watermilfoil Zebra mussels Physical Characteristics Surface area (acres): 689 Littoral area (acres): 314 % Littoral area: 46% Max depth (ft), (m): 63 Inlets: 6 Outlets: 1 Public Accesses: 1 Table 2: Availability of data and an observation of the quantity of sample points. Data Availability Transparency data Chemical data Inlet/Outlet data Good amount of data from from Citizen Lake Monitoring Program. Good amount of phosphorus and chlorophyll a data, but not enough for a trend analysis. No inlet data is available. The MPCA maintains a Citizen Stream Monitoring site at the outlet that collects observational data. Recommendations For recommendations refer to page 18. RMB Environmental Laboratories, Inc. 1 of Ossawinnamakee Lake

2 Lake Map Figure 1. Map of Lake Ossawinnamakee illustrating bathymetry, lake sample site locations, stream inlets and outlets and aerial land use. The green shaded 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. (MPCA: Minnesota Pollution Control Agency, CLMP: Citizens Lake Monitoring Program, WAPOA: Whitefish Area Property Owners Association) Lake Site Depth Monitoring Programs (ft) MPCA: CLMP: , *secondary site 60 CLMP: , ; MPCA: CLMP: , CLMP: CLMP: CLMP: 1986, , ; MPCA: *primary site 45 CLMP: 1975, ; MPCA: 1993; WAPOA: CLMP: 2010 RMB Environmental Laboratories, Inc. 2 of Ossawinnamakee Lake

3 Average Water Quality Statistics The information below describes available chemical data for the primary site (211) of Lake Ossawinnamakee through The data set is limited, and all parameters with the exception of total phosphorus, chlorophyll a and secchi depth, are means for just 1993 data. 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 9. Table 4. Water quality means compared to ecoregion ranges and impaired waters standard. Impaired Parameter Mean Ecoregion Range 1 Waters Standard 2 Interpretation Total phosphorus (ug/l) > 30 3 Chlorophyll a (ug/l) > 9 Chlorophyll a max (ug/l) 6 <15 Secchi depth (ft) < 6.5 Dissolved oxygen Dimictic (see page 8) Results are better than the expected range for the ecoregion. Dissolved oxygen depth profiles show that the deep areas of the lake are anoxic in late summer. Total Kieldahl Nitrogen Indicates insufficient nitrogen to support summer nitrogen-induced (mg/l) algae blooms. Alkalinity (mg/l) Indicates a low sensitivity to acid rain and a good buffering capacity. Color (Pt-Co Units) Indicates clear water with little to no tannins (brown stain). ph Indicates a hardwater lake. Lake water ph less than 6.5 can affect fish spawning and the solubility of metals in the water. Chloride (mg/l) Slightly higher than the expected range for the ecoregion, but still considered low level. Total Suspended Solids (mg/l) Specific Conductance (umhos/cm) Total Nitrogen :Total Phosphorus 1.4 <1-2 Indicates low suspended solids and clear water Within the expected range for the ecoregion. 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 Ossawinnamakee Lake

4 Water Quality Characteristics - Historical Means and Ranges Table 5. Water quality means and ranges for primary sites. Parameters Primary Site 211 Site 204 Total Phosphorus Mean (ug/l): 11 9 Total Phosphorus Min: 6 7 Total Phosphorus Max: Number of Observations: 22 4 Chlorophyll a Mean (ug/l): 2 2 Chlorophyll-a Min: <1 2 Chlorophyll-a Max: 6 4 Number of Observations: 22 4 Secchi Depth Mean (ft): Secchi Depth Min: Secchi Depth Max: Number of Observations: Figure 2. Lake Ossawinnamakee total phosphorus, chlorophyll a and transparency historical ranges. The arrow represents the range and the black dot represents the historical mean (Primary Site 211). Figure adapted after Moore and Thornton, [Ed.] Lake and Reservoir Restoration Guidance Manual. (Doc. No. EPA 440/ ) RMB Environmental Laboratories, Inc. 4 of Ossawinnamakee 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. For all the sites that had more than 20 transparency data points, the mean transparency ranges from 15.3 to 18.2 feet. The transparency throughout the lake appears to be relatively uniform, with the best transparency occurring in the western basin. Sites 211 and 204 consistently have similar transparency readings. These are both deep locations on Lake Ossawinnamakee. Transparency monitoring should be continued annually at sites 211 and 204 in order to track water quality changes. The last 6 years, transparency readings have been better than the long-term mean. 25 Transparency: Annual Means 20 Secchi Depth (ft) Long term Mean Figure 3. Annual mean transparency compared to long-term mean transparency, sites 211 and 204. Lake Ossawinnamakee transparency ranges from 8 to 24 ft at the primary site (211). Figure 4 shows the seasonal transparency dynamics. Lake Ossawinnamakee transparency remains fairly consistent throughout the summer. Some lakes vary throughout the summer while some lakes stay constant. It is common for transparency to improve after turnover in the spring and late fall. The dynamics have to do with algae population dynamics and lake turnover. RMB Environmental Laboratories, Inc. 5 of Ossawinnamakee Lake

6 Secchi Depth (ft) Seasonal Transparency Dynamics pattern Poly. (pattern) 0 26 Feb 17 Apr 6 Jun 26 Jul 14 Sep 3 Nov Figure 4. Seasonal transparency dynamics and year to year comparison (Primary Site 211). 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 Ossawinnamakee was rated as being "crystal clear" 64% of the time between at site % Physical Appearance Rating 64% Crystal clear water 35% 35% Not quite crystal clear a little algae visible 1% Definite algae green, yellow, or brown color apparent 64% 0% High algae levels with limited clarity and/or mild odor apparent 0% Severely high algae levels Figure 5. Physical appearance rating, as rated by the volunteer monitor ( ). RMB Environmental Laboratories, Inc. 6 of Ossawinnamakee Lake

7 As the secchi depth decreases, the perception of recreational suitability of the lake decreases. Lake Ossawinnamakee was rated as being "beautiful" 74.5% of the time from at site % Recreational Suitability Rating 25.2% 74.5% Beautiful, could not be better 25.2% Very minor aesthetic problems; excellent for swimming, boating 0.3% Swimming and aesthetic enjoyment of the lake slightly impaired because of algae levels 74.5% 0% Desire to swim and level of enjoyment of the lake substantially reduced because of algae levels 0% Swimming and aesthetic enjoyment of the lake nearly impossible because of algae levels Figure 6. Recreational suitability rating, as rated by the volunteer monitor ( ). Total Phosphorus Lake Ossawinnamakee is phosphorus limited, which means that algae and aquatic plant growth is dependent upon available phosphorus. Total phosphorus was evaluated in Lake Ossawinnamakee in 1993, at site 211. Figure 7 only shows the recent data. The data do not indicate much seasonal variability. The majority of the data points fall into the oligotrophic range with some points in the mesotrophic range. Total Phosphorus (ug/l) Phosphorus should continue to be monitored to track any future changes in water quality Total Phosphorus Mesotrophic Oligotrophic Figure 7. Historical total phosphorus concentrations (ug/l) for Ossawinnamakee Lake at site RMB Environmental Laboratories, Inc. 7 of Ossawinnamakee 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 was evaluated in Lake Ossawinnamakee in 1993, at site 211. Figure 8 only shows the recent data. Chlorophyll a concentrations for all dates at all sites remained below 10 ug/l, indicating clear water all summer. Chlorophyll a concentrations remained relatively steady over the summer. These results are consistent with the transparency results in that it does not vary much over the course of the summer. Dissolved Oxygen Chloophyll a (ug/l) Chlorophyll a Minor Algae Figure 8. Chlorophyll a concentrations (ug/l) for Lake Ossawinnamakee at site 211. 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 Ossawinnamakee is a relatively deep lake, with a maximum depth of 63 ft. Dissolved oxygen profiles from indicate that both sites 2004 in the western bay and 211 in the eastern bay stratify in the summer. Benthic phosphorus samples taken in 1993 at site 204 ( ug/l) and 211 (38-57 ug/l) indicate minor internal loading. Figure 9 illustrates stratification in the summer of 1993 at site 211. This is a representative DO profile for Lake Ossawinnamakee. Figure 9. Dissolved oxygen profile for Ossawinnamake Lake in 1993 at site 211. RMB Environmental Laboratories, Inc. 8 of Ossawinnamakee Lake

9 Trophic State Index Phosphorus (nutrients), chlorophyll a (algae concentration) and Secchi depth (transparency) are related. As phosphorus increases, there is more food available for algae, resulting in increased algal concentrations. When algal concentrations increase, the water becomes less transparent and the Secchi depth decreases. The results from these three measurements cover different units and ranges and thus cannot be directly compared to each other or averaged. In order to standardize these three measurements to make them directly comparable, we convert them to a trophic state index (TSI). Table 6. Trophic State Index. Trophic State Index Site 211 TSI Total Phosphorus 43 TSI Chlorophyll-a 40 TSI Secchi 35 TSI Mean 39 Oligotrophic/ Trophic State: Mesotrophic Numbers represent the mean TSI for each parameter. 100 The mean TSI for Lake Ossawinnamakee is on the oligotrophic/mesotrophic border (TSI 39-41) (Figure 10). There is good agreement between the TSI for phosphorus, chlorophyll a and transparency, indicating that these variables are strongly related (Table 6). Lakes on the oligotrophic/mesotrophic border (TSI 39-41) are characteristic of clear water throughout the summer and are excellent Ossawinnamakee for recreation (Table 7). The bottom of Lake the deep areas of the lake becomes anoxic (no oxygen) during the summer, which is inhospitable to game fish. This occurrence is common in Minnesota lakes. Hypereutrophic Eutrophic Mesotrophic Oligotrophic Figure 10. Trophic state index chart with corresponding trophic status. Table 7. Trophic State Index categories and corresponding lake 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 Ossawinnamakee 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 Lake Ossawinnamakee. Site 211 had over 8 years of transparency data, which was enough data to perform a long-term trend analysis (Table 8). The data was analyzed using the Mann Kendall Trend Analysis. Table 8. Trend analysis for Lake Ossawinnamakee. Lake Site Parameter Date Range Trend Probability 211 Transparency Improving 95% 211 Transparency No Trend Total Phosphorus Insufficient data Chlorophyll a Insufficient data Transparency Trend for Lake Ossawinnamakee 25.0 Secchi Depth (m) Site Figure 11. Transparency (ft) trend for site 211 from The black line represents the trend in the data. Site 211 is showing a significant improving trend in transparency from ; however, no trend was observed when looking at just the last decade of data. The transparency has improved an average of approximately 4.5 feet since 1986 (Figure 11). Transparency monitoring should continue at both sites (211 and 204) so that this trend can be tracked in future years. RMB Environmental Laboratories, Inc. 10 of Ossawinnamakee 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. Lake Ossawinnamakee is in the Northern Lakes and Forests Ecoregion. The mean total phosphorus was within the expected ecoregion ranges. Chlorophyll a mean was lower and transparency (secchi depth) was higher (Fig 13). Figure 12. Map of Minnesota with the seven ecoregions Total Phosphorus (ug/l, ppb) Chlorophyll-a (ug/l, ppb) Secchi depth (ft) increased algae 0 NLF Ecoregion Ossawinnamakee 30 NLF Ecoregion 0 NLF Ossawinnamakee Ecoregion Ossawinnamakee crystal clear Figures 13a-c. Lake Ossawinnamakee ranges compared to Northern Lakes and Forest Ecoregion ranges. The Lake Ossawinnamakee total phosphorus and chlorophyll a ranges are from 26 data points collected in May-September of 1993, The Lake Ossawinnamakee secchi depth range is from 490 data points collected in May-September from RMB Environmental Laboratories, Inc. 11 of Ossawinnamakee Lake

12 Lakeshed Data and Interpretations Lakeshed Understanding a lakeshed requires an understanding of basic hydrology. A watershed is defined as all land and water surface area that contribute excess water to a defined point. The MN DNR has delineated three basic scales of watersheds (from large to small): 1) basins, 2) major watersheds, and 3) minor watersheds. The Pine River Major Watershed is one of the watersheds that make up the Upper Missisippi River Basin, which eventually drains south to the Gulf of Mexico (Figure 14). This major watershed is made up of 69 minor watersheds. Lake Ossawinnamakee is located in minor watershed (Figure 15). Figure 14. Pine River Watershed. Figure 15. Minor Watershed The MN DNR also has evaluated catchments for each individual lake with greater than 100 acres surface area. These lakesheds (catchments) are the building blocks for the larger scale watersheds. Lake Ossawinnamakee falls within the Ossawinnamakee ( ) lakeshed (Figure 16). Though very useful for displaying the land and water that contribute directly to a lake, lakesheds are not true watersheds because they do 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 Figure 16. The Ossawinnamakee ( ) Lakeshed. This area is the land and water surface that flow directly into Ossawinnamakee Lake. connected to a large number of lakesheds, reflecting a larger drainage area via stream or river networks. For further discussion of Lake Ossawinnamakee s full watershed, containing all the upstream lakesheds, see page 17. The data interpretation of the RMB Environmental Laboratories, Inc. 12 of Ossawinnamakee Lake

13 Lake Ossawinnamakee lakeshed is only the immediate lakeshed, not including the upstream lakesheds, as this area is the land surface that flows directly into Lake Ossawinnamakee. 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 Ossawinnamakee lakeshed vitals table. Lakeshed Vitals Rating Lake Area 689 acres descriptive Littoral Zone Area 314 acres descriptive Lake Max Depth 63 ft. descriptive Lake Mean Depth Water Residence Time 21 ft. 6-7 years Miles of Stream 1.5 descriptive Inlets 6 Outlets 1 Major Watershed 11 Pine River descriptive Minor Watershed descriptive Lakeshed descriptive Ecoregion Northern Lakes and Forest descriptive Total Lakeshed to Lake Area Ratio (total lakeshed includes lake area) 7:1 Standard Watershed to Lake Basin Ratio (standard watershed includes lake areas) 44:1 Wetland Coverage 6.0% Aquatic Invasive Species Eurasian watermilfoil (2002) Zebra mussels (2003) Public Drainage Ditches Present Public Lake Accesses 1 Miles of Shoreline 13.4 descriptive Shoreline Development Index 3.7 Public Land to Private Land Ratio 0.1:1 Development Classification General Development Miles of Road 28.4 descriptive Municipalities in lakeshed Forestry Practices Feedlots Sewage Management Lake Management Plan Breezy Point, CrossLake County Forest Management: None Individual Subsurface Sewage Treatment Systems (Inspection and assessment required for all permits and property transfers within the Shoreland Protection Zone) Healthy Lakes & Rivers Partnership program Lake Vegetation Survey/Plan Minnesota DNR 2005 & 2009 RMB Environmental Laboratories, Inc. 13 of Ossawinnamakee Lake

14 Land Cover / Land Use The activities that occur on the land within the lakeshed can greatly impact a lake. Land use planning helps ensure the use of land resources in an organized fashion so that the needs of the present and future generations can be best addressed. The basic purpose of land use planning is to ensure that each area of land will be used in a manner that provides maximum social benefits without degradation of the land resource. Changes in land use, and ultimately land cover, impact the hydrology of a lakeshed. Land cover is also directly related to the lands ability to absorb and store water rather than cause it to flow overland (gathering nutrients and sediment as it moves) towards the lowest point, typically the lake. Impervious intensity describes the lands inability to absorb water, the higher the % Figure 17. The Ossawinnamakee Lake lakeshed ( ) land cover ( 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 Ossawinnamakee s lakeshed. The University of Minnesota has online records of land cover statistics from years 1990 and 2000 ( Table 10 describes Lake Ossawinnamakee s lakeshed land cover statistics and percent change from 1990 to Due to the many factors that influence demographics, one cannot determine with certainty the projected statistics over the next 10, 20, 30+ years, but one can see the transition within the lakeshed from agriculture, grass/shrub/wetland, and water acreages to forest and urban acreages. The largest change in percentage is the decrease in grass/shrub/wetland cover (32%); however, in acreage, forest cover has increased the most (208 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 Ossawinnamakee Lake

15 Table 10. Lake Ossawinnamkee s lakeshed land cover statistics and % change from 1990 to 2000 ( % Change Land Cover Acres Percent Acres Percent 1990 to 2000 Agriculture % Decrease Grass/Shrub/Wetland % Decrease Forest % Increase Water % Decrease Urban % Increase Impervious Intensity % % Decrease % Increase % Increase % Increase % Decrease % Increase % Increase Total Area Total Impervious Area (Percent Impervious Area Excludes Water Area) % Increase Demographics Lake Ossawinnamakee 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, Ideal Township has a similar extrapolated growth projection (Figure 18). Figure 18. Population growth projection for Ideal Township, City of Breezy Point, and Crow Wing County. (source: hy.state.mn.us/resour ce.html?id=19332) Percent 120% 100% 80% 60% 40% Population Growth Projection Compared to 2006 Population City of Breezy Point; 2006 population: 1,642 Crow Wing County total; 2006 population: 61,038 Ideal Township; 2006 population: % 0% Year RMB Environmental Laboratories, Inc. 15 of Ossawinnamakee Lake

16 Lake Ossawinnamakee 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 Ossawinnamakee 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 (73%) 17% Public (10%) Developed Agriculture Forested Uplands Other Wetlands Open Water County State Federal Land Use (%) 1.1% 0.8% 44.6% 21.6% 4.9% 17% 2.2% 7.6% 0.2% Runoff Coefficient Lbs of phosphorus/acre/ year Estimated Phosphorus Loading Acerage x runoff coefficient <1 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 Ossawinnamakee Lake

17 Table 12. Suggested approaches for watershed protection and restoration of DNR-managed fish lakes in Minnesota. Watershed Disturbance (%) < 25% Watershed Protected (%) Management Type > 75% Vigilance < 75% Protection 25-60% n/a Full Restoration > 60% n/a Partial Restoration Comments 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. Lake Ossawinnamakee is classified with having 28.3% of the watershed protected and 3.1% of the watershed disturbed (Figure 19). Therefore, Lake Ossawinnamakee should have a protection focus. Goals for the lake should be to limit any increase in disturbed land use. In addition, Lake Ossawinnamakee was designated by DNR Fisheries as a high valued fishery lake because of its cisco population. 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 Ossawinnamakee, whether through direct overland flow or through a creek or river. All of the 20 upstream lakesheds have the same management focus (protection). Percent of the Watershed Protected 0% 75% 100% Ossawinnamakee Lake (28.3%) Percent of the Watershed with Disturbed Land Cover 0% 25% 100% Ossawinnamakee Lake (3.1%) Figure 19. Lake Ossawinnamakee lakeshed s Figure 20. Upstream lakesheds that contribute water percentage of watershed protected and disturbed. to the Ossawinnamakee lakeshed. Color-coded RMB Environmental Laboratories, Inc. based on management focus (Table 12). 17 of Ossawinnamakee Lake

18 Ossawinamakee, Status of the Fishery (as of 06/22/2009) Ossawinamakee is a 644 acre lake located about three miles north of Breezy Point in Crow Wing County. The lake is heavily developed with 343 homes/cabins and one campground/recreational vehicle park along its 13.1 miles of shoreline (26.2 homes per mile). The maximum depth is 63' with about 35% of the lake being 15' deep or less. A variety of sand, marl, gavel and rubble substrates occur in shallow waters which helps support a diverse aquatic plant community. There is a public access located on the east end of the lake. Lake users need to take extra precautions when transporting equipment from this lake as Eurasian watermilfoil and zebra mussels, both prohibited invasive species, are present. Walleye are currently stocked as fingerlings at a rate of 2 pounds/littoral acre every other year. The 2009 walleye catch rate fell to 0.9/gill net, the lowest rate recorded in any of the nine assessments since Average size increased to 20.6" and 3.9 pounds in The northern pike catch rate decreased to 7.1/gill net, down from a high of 9.6/gill net in Average size was 21.2" and 2.3 pounds with 26% of these fish measuring at least 24". Largemouth bass were caught in high numbers in gill nets (1.25/gill net) and low numbers in trap nets (0.2/trap net) when compared to similar lakes. Bluegills were captured at a rate of 42.2/trap net, similar to the 2003 catch and "high" relative to similar lakes. Growth was slow and 17% of bluegills sampled measured at least 7". Important forage species for this lake include yellow perch and tullibee. While the catch rate for yellow perch (1.1/gill net) showed a statistically significant increase from 2003, the catch remains "very low" when compared to similar lakes. Tullibee, which had been captured in high numbers in recent surveys, decreased to a catch of 2.1/gill net, about "average" for 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 at sites 211 and 204 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. Phosphorus and chlorophyll a monitoring should continue at site 211, as the budget allows, to track future water quality trends. If land use becomes a concern, the inlets could be monitored for phosphorus coming into the lake. Inlet monitoring will show the effectiveness of upstream restoration/protection projects in the watershed. Overall Conclusions Overall, Lake Ossawinnamakee has good water quality, and is in fair shape for lakeshed protection. Volunteer water quality samplers rated this lake as beautiful, could not be better 74.5% of the time and having very minor aesthetic problems 25.2% of the time. It is an oligotrophic/mesotrophic lake (TSI=39) with an improving trend in transparency over the past decade. Ten percent (10%) of the lakeshed is in public ownership, and 28% of the lakeshed is protected, while only 3% of the lakeshed is disturbed (Figure 19). RMB Environmental Laboratories, Inc. 18 of Ossawinnamakee Lake

19 Priority Impacts to the lake The priority impact to Lake Ossawinnamakee is the surrounding development and any future development. Though the city of Breezy Point is 2 miles to the south, along the shore of Pelican Lake, part of Lake Ossawinnamakee is located in the municipal boundary of the city. The population of Breezy Point is projected to increase 100% from 2006 to 2035 (Figure 18). The infrastructure is already in place between the lake and main city to increase the housing density. Several houses have been constructed since 2003 less than 0.5 miles from the shore. The concern with increased development is the conversion of forested land to a land use with increased impervious surfaces, such as roofs, driveways, and well groomed lawns. Phosphorus loading will increase when land use changes from forested to developed. A way to mitigate this issue is through the installation of Best Management Practices (BMPs). An additional potential impact to Lake Ossawinnamakee is the disturbance of the littoral zones by boating activity. Though Lake Ossawinnamakee is a relatively deep lake, each deep area is separated by a littoral zone (less than 15 ft.) It is very important to protect native aquatic plant beds to preserve fish habitat and water clarity in this area. In addition, large boat motors can churn up the sediment and re-suspend phosphorus, causing algae blooms. Best Management Practices Recommendations The management focus for Lake Ossawinnamakee should be to protect the water quality and the lakeshed. Lake Ossawinnamakee is currently designated as a high valued fishery lake because of its cisco population. 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. Stormwater management and sediment reduction in the cities of Breezy Point and Crosslake will benefit all the lakes in that area. 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 streams and lake. Native aquatic plants stabilize the lake s sediments and tie up phosphorus in their tissues. When aquatic plants are uprooted from a shallow 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. 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, inlet monitoring, 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. The full watershed area that contributes water to Lake Ossawinnamakee is moderate in size. Monitoring the six inlets for water quality and velocity would help identify if and/or where the highest nutrient sources to the lake. RMB Environmental Laboratories, Inc. 19 of Ossawinnamakee Lake

20 A watershed flow analysis could also be done using GIS software to see the areas of heaviest runoff into the lake. Not all the water entering Lake Ossawinnamakee will flow through the six inlets. Some will flow in smaller ditches or swales. This analysis would also help pinpoint locations to install BMPs to mitigate increases in impervious surfaces. County-wide Recommendation In order to better manage the impact of septic systems on lake water quality, it is recommended that the county implement a lake-wide septic inspection program. In a program such as this, the county would focus on one to three lakes a year, pull septic system records on those lakes, and require old systems to be inspected. This program can rotate through the county doing a few lakes each year. Organizational contacts and reference sites Lake Ossawinnamakee Property Owners Association DNR Fisheries Office Regional Minnesota Pollution Control Agency Office Crow Wing Soil and Water Conservation District Crow Wing County Environmental Services Department Minnesota Drive, Brainerd, MN brainerd.fisheries@state.mn.us 7678 College Road, Suite 105, Baxter, MN , Crow Wing County Land Services Building 322 Laurel St. Suite 13, Brainerd, MN Crow Wing County Land Services Building 322 Laurel St. Suite 14, Brainerd, MN Funding This project was funded in part by the Board of Water & Soil Resources and the Initiative Foundation, a regional foundation. RMB Environmental Laboratories, Inc. 20 of Ossawinnamakee Lake