Gull Lake CASS & CROW WING COUNTIES

Transcription

1 Gull Lake CASS & CROW WING COUNTIES Lake Water Quality Summary Gull Lake is located just northwest of Brainerd, Minnesota, on the border of Cass and Crow Wing Counties. It covers 9,947 acres, which places it in the upper 5% of lakes in Minnesota in terms of size. Gull Lake is part of a chain of lakes that consists of 8 lakes and connecting channels covering 13,000 acres. Gull Lake has two inlets and one outlet, which classifies it as a drainage lake. It occurs in the Crow Wing River Watershed. Water flows south from Upper Gull Lake into a navigable channel that connects to Gull Lake. Bishops Creek also flows into Gull Lake from Round Lake on the east. The Gull River flows out of the south end of Gull Lake, and continues south to the Crow Wing River. The Crow Wing River then eventually joins the Mississippi River. Water quality data have been collected on Gull Lake from (Tables 2, 3). These data show that the lake is mesotrophic. Mesotrophic lakes are commonly found in north-central Minnesota and have clear water with occasional algal blooms in late summer. The Gull Chain of Lakes Association mission statement says it is devoted to the restoration and continued preservation of the highest water quality and environmental standards achievable, promotion of the responsible use of land and water resources and recreational safety on the Gull Chain of Lakes. The Association has been involved in numerous activities including water quality monitoring, education, promotion of safety, buoys, fishing and supporting local business. Table 1. Gull Lake location and key physical characteristics. Location Data MN Lake ID: County: Cass and Crow Wing Ecoregion: Northern Lakes & Forests Major Drainage Basin: Upper Mississippi Latitude/Longitude: / Invasive Species: Zebra mussels, Curly-leaf pondweed, Heterosporis Physical Characteristics Surface area (acres): 9,947 Littoral area (acres): 2,825 % Littoral area: 28% Max depth (ft), (m): 80, 24.3 Inlets: 2 Bishop's Creek Outlets: 1 Gull River Public Accesses: 4 Table 2: Availability of data and an observation of the quantity of sample points. Data Availability Transparency data Chemical data Numerous yearly Secchi readings from through the MPCA CLMP program. There is a good amount of Total Phosphorus and Chlorophyll a data, but not enough for a trend anlalysis. Inlet/Outlet data Tributary data have been collected in Recommendations For recommendations refer to page 19. RMB Environmental Laboratories, Inc. 1 of Gull Lake

2 Lake Map Figure 1. Map of Gull Lake 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. Programs include Citizen Lake Monitoring Program (CLMP), Minnesota Pollution Control Agency (MPCA), RMB Environmental Laboratories Lakes Monitoring Program (RMBEL). Lake Site Depth (ft) Monitoring Programs 101* Primary Site 70 MPCA: , 1989, 2004 CLMP: MPCA: , 1989 CLMP: CLMP: ; MPCA: MPCA: ; CLMP: , * Secondary Site 40 CLMP: * Primary Site 35 CLMP: ; RMBEL: CLMP: CLMP: ; MPCA: MPCA: MPCA: MPCA: The following sites are not included in this table: sites 100, 202 and 203 (data only from ); site 207 (data only from 1993)) RMB Environmental Laboratories, Inc. 2 of Gull Lake

3 Average Water Quality Statistics The information below describes available chemical data for site 101 on Gull 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 1989 and 2004 data. Minnesota is divided into seven ecoregions based on land use, vegetation, precipitation and geology. The MPCA has developed a way to determine the "average range" of water quality expected for lakes in each ecoregion. For more information on ecoregions and expected water quality ranges, see page 11. Table 4. Water quality means compared to ecoregion ranges and impaired waters standard. Impaired Parameter Mean Ecoregion Range 1 Waters Standard 2 Interpretation Total phosphorus (ug/l) > 30 Results are within the expected range for the ecoregion. Chlorophyll a (ug/l) > 9 Chlorophyll a max (ug/l) 10 <15 Secchi depth (ft) < 6.5 Dissolved oxygen see page 8 Dissolved oxygen depth profiles show that the deep areas of the lake are anoxic in late summer. Total Kieldahl Nitrogen Indicates insufficient nitrogen to support summer nitrogen-induced (mg/l) algae blooms. Alkalinity (mg/l) Indicates a low sensitivity to acid rain and a good buffering capacity. Color (Pt-Co Units) Indicates very clear water with little to no tannins (brown stain). ph Characteristic of a hard water lake. Lake water with ph less than 6.5 can affect fish spawning and the solubility of metals in the water. Chloride (mg/l) Slightly above the ecoregion average but still considered low level. Total Suspended Solids (mg/l) Specific Conductance (umhos/cm) Total Nitrogen :Total Phosphorus 2.9 <1-2 Slightly above the ecoregion average but still considered low level Within the ecoregion average range. 33:1 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 Gull Lake

4 Water Quality Characteristics - Historical Means and Ranges Table 5. Water quality means and ranges for primary sites. Parameters Site 101 Site 205 Site 206 Site 209 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. Gull Lake total phosphorus, chlorophyll a and transparency historical ranges. The arrow represents the range and the black dot represents the historical mean (Primary Site 101). Figure adapted after Moore and Thornton, [Ed.] Lake and Reservoir Restoration Guidance Manual. (Doc. No. EPA 440/ ) RMB Environmental Laboratories, Inc. 4 of Gull 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. Site 205, at the south end of the main bay, had consistently higher mean transparencies than site 206 in Booming Out Bay. The annual means for Gull range from 7-13 ft (Figure 3). Transparency was highest in , and For trend analysis, see page Transparency: Annual Means 14 Secchi Depth (ft) Site 101 Site 205 Site 206 Site 209 Figure 3. Annual mean transparency for sites 101, 205, 206 and 209. Gull Lake transparency ranges from 4.5 to 20 feet throughout the summer. This range is indicative of a dynamic lake. Figure 4 shows the seasonal transparency dynamics. The maximum Secchi reading is usually obtained in early summer. Lake transparency is high in May and June, and then declines through August. The transparency then rebounds in October after fall turnover. This transparency dynamic is typical of a northern Minnesota lake. 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 Gull Lake

6 Secchi Depth (ft) Seasonal Transparency Dynamics Average Poly. (Average) Figure 4. Seasonal transparency dynamics and year-to-year comparison (site 205). 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. Gull Lake was rated as being "not quite crystal clear" 61% of the time between , and (Figure 5). 4% 0% Physical Appearance Rating 35% 35% Crystal clear water 61% Not quite crystal clear a little algae visible 4% Definite algae green, yellow, or brown color apparent 61% 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 Gull Lake

7 As the Secchi depth decreases, the perception of recreational suitability of the lake decreases. Gull Lake was rated as being "beautiful" 46% of the time from , and (Figure 6). Recreational Suitability Rating 3% 1% 46% Beautiful, could not be better 50% Very minor aesthetic problems; excellent for swimming, boating 46% 3 % Swimming and aesthetic enjoyment of the lake slightly impaired because of algae levels 50% 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 Gull Lake is phosphorus limited, which means that algae and aquatic plant growth is dependent upon available phosphorus. Total phosphorus was evaluated in Gull Lake in , 1989, , 2004, and Figure 7 shows all phosphorus data since The majority of the data points fall into the mesotrophic range. Total Phosphorus (ug/l) Total Phosphorus 35 Eutrophic Mesotrophic 10 5 Oligotrophic 0 Figure 7. Historical total phosphorus concentrations (ug/l) for Gull Lake. Site 101, 2004 Site 201, 2004 Site 206, 2007 Site 206, 2008 Site 206, 2009 Site 209, 2004 Booming Out Bay Mean Main Lake Mean Site 206, in Booming Out Bay, has slightly higher phosphorus concentrations than the main basin. Steamboat Bay (201) and Wilson Bay (209) have similar phosphorus concentrations to the main basin (101). Phosphorus should continue to be monitored to track any future changes in water quality RMB Environmental Laboratories, Inc. 7 of Gull Lake

8 Chlorophyll a Chlorophyll a is the pigment that makes plants and algae green. Chlorophyll a is tested in lakes to determine the algae concentration or how "green" the water is. Chlorophyll a concentrations greater than 10 ug/l are perceived as a mild algae bloom, while concentrations greater than 20 ug/l are perceived as a nuisance. Chlorophyll a (ug/l) Chlorophyll a Figure 8. Historical chlorophyll a concentrations (ug/l) for Gull Lake. Site 101, 2004 Site 201, 2004 Site 206, 2007 Site 206, 2008 Site 206, 2009 Site 209, 2004 Minor Algae Major Algae Chlorophyll a was evaluated in Gull Lake in , 1989, , 2004, and Figure 8 shows all phosphorus data since Chlorophyll a concentrations for Wilson Bay (209) remained below 10 ug/l, indicating clear water most of the summer. At the remaining sites, the chlorophyll a concentrations exceeded 10 ug/l, which indicates mild algae blooms toward the end of the summer. Dissolved Oxygen Dissolved Oxygen (mg/l) Depth 9 (m) 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. Gull Lake is a relatively deep lake, with a maximum depth of 80 ft. Dissolved oxygen profiles from , 1989 and 2004 indicate that the three main bays (Main, Wilson, Steamboat) stratify in the summer. Benthic phosphorus samples taken in 1989 and 2004 indicate that internal loading occurs (TP= ug/l). Figure 9 illustrates stratification in the summer of 2004 in all three bays. The thermocline exists around 9-10 meters (30-33 ft). Figure 9. Dissolved oxygen profile for Gull Lake on August 26, RMB Environmental Laboratories, Inc. 8 of Gull 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 Trophic State: concentrations increase, the water becomes less transparent and the Secchi depth decreases. Table 6. Trophic State Index. Trophic State Index In order to standardize these three measurements to make them directly comparable, we convert them to a trophic state index (TSI). Site 101 Main Basin The mean TSI for Gull Lake falls in the mesotrophic range (Figure 10). There is good agreement between the TSI for phosphorus, chlorophyll a and transparency, indicating that these variables are strongly related (Table 6). Gull Lake The TSI for chlorophyll a was higher than that of total phosphorus and transparency for most of the bays. Booming Out Bay has the highest TSI, which is approaching eutrophic conditions (TSI 50). Site 206 Booming Out Bay Hypereutrophic Eutrophic Mesotrophic Oligotrophic Site 209 Wilson Bay TSI Total Phosphorus TSI Chlorophyll-a TSI Secchi TSI Mean Numbers represent the mean TSI for each parameter Site 201 Steamboat Bay Mesotrophic Mesotrophic Mesotrophic Mesotrophic Mesotrophic lakes (TSI 40-50) are characterized by moderately clear water most of the summer (Table 7). "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. 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 Gull 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 Gull Lake. Site 205 in the south end of the main basin and site 206 in Booming Out Bay have over 8 years of transparency data, which is enough data to perform a short-term and long-term trend analysis (Table 8). The data was analyzed using the Mann Kendall Trend Analysis. Table 8. Trend analysis for Gull Lake. Lake Site Parameter Date Range Trend Probability 205 (Main Bay) Transparency No Trend (Main Bay) Transparency No Trend (Booming Out Bay) Transparency Declining 99% 206 (Booming Out Bay) Transparency Declining 95% 14 Transparency Trend for Booming Out Bay 12 Secchi Depth (ft) Figure 11. Long-term transparency trend for Booming Out Bay in Gull Lake. Site 206 shows a statistically significant declining trend in transparency from and from (Figure 11). The transparency has declined an average of approximately 1.5 feet since Site 205 in the main bay shows no trend from Transparency monitoring should continue at both sites so that this trend can be tracked in future years. RMB Environmental Laboratories, Inc. 10 of Gull 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. Gull Lake is in the Northern Lakes and Forests Ecoregion. The mean total phosphorus, chlorophyll a and transparency (Secchi depth) for Gull Lake are all within the expected ecoregion ranges (Figure 13). Figure 12. Map of Minnesota with the seven ecoregions Total Phosphorus (ug/l, ppb) Chlorophyll-a (ug/l, ppb) Secchi depth (ft) increased algae crystal clear a 0 NLF Ecoregion Gull Lake b 0 NLF Ecoregion Gull Lake c 25 NLF Ecoregion Gull Lake Figures 13a-c.Gull Lake ranges compared to Northern Lakes and Forest Ecoregion ranges. The Gull Lake total phosphorus and chlorophyll a ranges are from 33 and 29 data points, respectively, collected in May- September of , 1989, 2004, and The Gull Lake Secchi depth range is from 689 data points collected in May-September from RMB Environmental Laboratories, Inc. 11 of Gull 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 Missisippi River Basin, which eventually drains south to the Gulf of Mexico (Figure 14). This major watershed is made up of 136 minor watersheds. Gull 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. Gull Lake falls within the Gull ( ) 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 connected to a large number of lakesheds, reflecting a larger drainage area via stream or river networks. For further discussion of Gull Lake s full watershed, containing all the upstream lakesheds, see page 17. The data interpretation of the Gull Lake lakeshed is only the immediate lakeshed, not including the upstream lakesheds, as this area is the land surface that flows directly into Gull Lake. Figure 16. The Gull ( ) Lakeshed. This area is the land and water surface that flow directly into Gull Lake. RMB Environmental Laboratories, Inc. 12 of Gull Lake

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. Gull Lake lakeshed vitals table. Lakeshed Vitals Rating Lake Area 9,947 acres descriptive Littoral Zone Area 879 acres descriptive Lake Max Depth 80 ft. descriptive Lake Mean Depth NA NA Water Residence Time NA NA Miles of Stream 1.27 descriptive Inlets Outlets 2 Bishop Creek, Upper Gull Lake 1 Gull River 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) 19:1 Wetland Coverage 3.6% Aquatic Invasive Species Zebra mussels, Heterosporis, Curly-leaf pondweed Public Drainage Ditches None Public Lake Accesses 4 Miles of Shoreline descriptive Shoreline Development Index 3.3 Public Land to Private Land Ratio 0.45:1 Development Classification General Development Miles of Road 72.2 descriptive Municipalities in lakeshed Forestry Practices Feedlots Sewage Management Lake Management Plan Lake Vegetation Survey/Plan None County Forest Management: None Individual Subsurface Sewage Treatment Systems (Inspection and assessment required for all permits and property transfers within the Shoreland Protection Zone) Healthy Lakes & Rivers Partnership program, 2006 None RMB Environmental Laboratories, Inc. 13 of Gull Lake

14 Land Cover / Land Use The activities that occur on the land within the lakeshed can greatly impact a lake. Land use planning helps ensure the use of land resources in an organized fashion so that the needs of the present and future generations can be best addressed. The basic purpose of land use planning is to ensure that each area of land will be used in a manner that provides maximum social benefits without degradation of the land resource. Changes in land use, and ultimately land cover, impact the hydrology of a lakeshed. Land cover is also directly related to the lands ability to absorb and store water rather than cause it to flow overland (gathering nutrients and sediment as it moves) towards the lowest point, typically the lake. Impervious intensity describes the lands inability to absorb water, the higher the % impervious intensity the more area that water cannot penetrate in to the Figure 17. The Gull Lake ( ) lakeshed land cover ( 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 Gull Lake s lakeshed land cover. The University of Minnesota has online records of land cover statistics from years 1990 and 2000 ( Table 10 describes Gull 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 and water acreages to forest, grass/shrub/wetland, and urban acreages. The largest change in percentage is the decrease in agriculture cover (58.5%); however, in acreage, forest cover has increased the most (359 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 Gull Lake

15 Table 10. Gull Lake 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 8, , % Increase Forest 1, , % Increase Water 10, , % Decrease Urban % Increase Impervious Intensity % 0 20, , % Decrease % Increase % Increase % Increase % Increase % Increase % Increase Total Area 21,281 21,281 Total Impervious Area (Percent Impervious Area Excludes Water Area) % Increase Demographics Cross Lake 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, the city of Nisswa has a slightly higher 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: e.mn.us/resource.html?id=1 9332). Percentage of 2006 Population 40% 30% 20% 10% Population Growth Projection City of Nisswa; 2006 population: 2,047 Crow Wing County; 2006 population: 61,038 0% Extrapolation RMB Environmental Laboratories, Inc. 15 of Gull Lake

16 Gull 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 Gull 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 (35%) 49% Public (16%) Developed Agriculture Forested Uplands Other Wetlands Open Water County State Federal Land Use (%) 3.6% 1% 19% 9.3% 2.1% 49% 0% 15.5% 0.5% 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 Gull Lake

17 Table 12. Suggested approaches for watershed protection and restoration of DNR-managed fish lakes in Minnesota. Watershed Watershed Management Disturbance Protected Type (%) (%) Comments > 75% Vigilance Sufficiently protected -- Water quality supports healthy and diverse native fish communities. Keep public lands protected. < 25% Excellent candidates for protection -- Water quality can be maintained in a range that supports healthy and diverse native < 75% Protection fish communities. Disturbed lands should be limited to less than 25%. Realistic chance for full restoration of water quality and improve 25-60% n/a Full Restoration quality of fish communities. Disturbed land percentage should be reduced and BMPs implemented. > 60% n/a Partial Restoration 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. Gull Lake lakeshed is classified with having 65.1% of the lakeshed protected and 5.5% of the lakeshed disturbed (Figure 19). Therefore, Gull Lake should have a protection focus. Much of the protected area is the lake itself, as surface water is included in the protected status. Goals for this lakeshed 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 Gull Lake, whether through direct overland flow or through a creek or river. Forty-five of the 53 upstream lakesheds have the same management focus (protection). Percent of the Watershed Protected 0% 75% 100% Gull Lake (65.1%) Percent of the Watershed with Disturbed Land Cover 0% 25% 100% Gull Lake (5.5%) Figure 19. Gull Lake lakeshed s percentage of watershed protected and disturbed. Figure 20. Upstream lakesheds that contribute water to the Gull lakeshed. Color-coded based on management focus (Table 12). RMB Environmental Laboratories, Inc. 17 of Gull Lake

18 Gull Lake, Status of the Fishery (as of 07/16/2007) Gull Lake, at 9,418 acres, is one of the largest and most popular lakes in the Brainerd area. The lake is heavily developed with 27.8 homes/cabins per shoreline mile and 19 resorts of various types and sizes as of The maximum depth is 80' and about 30% of the lake is 15' deep or less. Shallow water substrates consist primarily of sand and gravel, although areas of rubble and boulder are also common. The aquatic plant community is quite diverse with 35 species present and is critical to maintaining 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 2007 walleye catch of 8.5/gill net is the highest to date on Gull lake. Average length and weight were 14.6" and 1.3 lbs. Twelve different year classes were represented with age 2 and age 4 (2005 and 2003 year classes, respectively) accounting for 59% of the gill net catch. These 2 year classes have accounted for much of the angler harvest in 2006 and Northern pike abundance was typical of past catches at 4.1/gill net in Average length and weight were also similar at 25.8" and 4.0 lbs. The 2004 and 2003 year classes (age 3 and 4) were the strongest, accounting for 57% of all northern pike sampled. These fish measured approximately 19" to 27". Tullibee and yellow perch are important forage species for the lake's game fish. The yellow perch catch was lower than past catches on Gull lake, but at 18.3/gill net was still average when compared to similar lakes. Tullibee abundance was also the lowest to date at 0.5/gill net. A lack of thermal habitat in 2007 resulted in large die offs of tullibee and is likely responsible at least in part for the recent decline in tullibee abundance. See the link below for specific information on gillnet surveys, stocking information, and fish consumption guidelines. Inlet Monitoring Margaret Lake, which is just west of Gull Lake, is on the Impaired Waters List for eutrophication. This means that there is more phosphorus and algae in the lake than there should be. Margaret Lake flows into Upper Gull Lake and then Gull Lake, and the northern bay (Booming Out Bay) of Gull Lake has a declining trend in transparency. As a part of the further investigation of this area, six tributaries were monitored from April 2007 to October 2011 for total phosphorus (TP) (Table 13). The results showed that Home Brook and Stony Brook had the TP (ug/l) Home Brook 58.4 Stony Brook 63.0 Mayo Brook 39.0 Cullen Brook 12.7 Lazy Brook 29.7 Spring Brook 39.2 Table 13. Stream monitoring results from highest TP concentrations. Efforts to control phosphorus should be focused on Home Brook, Stony Brook and their watersheds. RMB Environmental Laboratories, Inc. 18 of Gull Lake

19 Key Findings / Recommendations Monitoring Recommendations Transparency monitoring at sites 101, 205 and 206 should be continued annually. It is important to continue transparency monitoring weekly or at least bimonthly every year without gaps to enable year-to-year comparisons and trend analyses. Phosphorus and chlorophyll a monitoring should continue at sites 101, 205 and 206, as the budget allows, to track future water quality trends. Inlet monitoring will show the effectiveness of upstream restoration/protection projects and Margaret Lake TMDL implementation in the watershed. Overall Conclusions Overall, Gull Lake has good water quality, and is in good shape for lakeshed protection. It is a mesotrophic lake (TSI=46) with no water quality trends in the main bay, and a declining transparency trend in Booming Out Bay (north). Sixteen percent (16%) of the lakeshed is in public ownership, and 65% of the watershed is protected, while 6% of the watershed is disturbed (Figure 19). Priority Impacts to the lake Gull Lake has two priority impacts. The first is the surrounding development and any future development. Because it is one of the most popular lakes in the Brainerd Area, Gull Lake has heavy first and second tier development. It had a development density of 27.8 homes/cabins per shoreline mile and 19 resorts of various types and sizes as of 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). The second priority impact is the watershed. Gull Lake s immediate lakeshed is fairly well protected, but the watershed to the northwest has a lot of agriculture that drains into the Gull Chain of Lakes. Booming Out Bay on the north end of Gull Lake has a declining trend in transparency. This could be due to the cumulative impacts from the watershed, and the fact that Margaret Lake, which is impaired for nutrients, drains in to the north end of Gull Lake. A TMDL study will be done for Margaret Lake to determine areas for phosphorus reduction in the watershed. The implementation projects from the Margaret Lake TMDL will also benefit Gull Lake since it is downstream. Best Management Practices Recommendations The management focus for Gull Lake should be to protect the water quality and the lakeshed, and work with upstream neighbors to better protect the watershed. 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 streams. Upstream in the watershed, projects that could improve the water quality of Gull Lake include assisting area farmers with best management practices such as restoring wetlands, preserving their land in the conservation reserve program, and installing buffers along creeks and streams. RMB Environmental Laboratories, Inc. 19 of Gull Lake

20 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. Continued monitoring of the inlets for water quality and adding velocity would help identify if and/or where the highest nutrient sources to the lake. 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 Gull Lake will flow through the 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. Organizational contacts and reference sites Gull Chain of Lakes Association DNR Fisheries Office Regional Minnesota Pollution Control Agency Office Crow Wing Soil and Water Conservation District Crow Wing County Environmental Services Department Box 102, Nisswa, MN 56468, info@gullchainoflakesassociation.org 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 Gull Lake