Winnibigoshish 11-0147-00 ITASCA and CASS COUNTIES
Total Page:16
File Type:pdf, Size:1020Kb
Lake Winnibigoshish 11-0147-00 ITASCA AND CASS COUNTIES Summary Lake Winnibigoshish is located at the city of Bena, MN, and spans both Cass and Itasca Counties. It covers 56,470 acres and is the 4th largest lake in Minnesota in terms of surface area. The Mississippi River enters and exits Lake Winnibigoshish. The lake water levels are affected by the operation of a dam on the Mississippi River at the lake outlet, and are managed by the U.S. Army Corps of Engineers under their general water management plan for the Mississippi River Headwaters. The Corp's water level management plan lists downstream commercial navigation, Leech Lake Chippewa Treaty resource rights, and recreational management priorities. Water quality data have been collected on Lake Winnibigoshish on and off since 1976. These data show that the lake is mesotrophic (page 9). Mesotrophic lakes are commonly found in north central Minnesota and have clear water with occasional algal blooms in late summer. Large mesotrophic lakes are excellent walleye lakes. Lake Winnibigoshish water quality and morphometry is similar to Mille Lacs and the main basin of Leech Lake, which are some of the best walleye lakes in the state of Minnesota. Lake Winnibigoshish water quality is managed by the Leech Lake Band of Ojibwe Division of Resource Management, the Minnesota Department of Natural Resources, the Cass County Environmental Services Department and the Itasca Soil and Water Conservation District. Vitals Physical Characteristics MN Lake ID: 11-0147-00 Surface area (acres): 56,470 County: Itasca and Cass Littoral area (acres): 18,904 Ecoregion: Northern Lakes and Forest % Littoral area: 33% Major Drainage Max depth (ft): 70 (m): 21.3 Upper Mississippi River Basin: Mean depth (ft): 15 (m): 4.6 Latitude/Longitude: 47.44277778/-94.2025 Lakeshed size (acres): 92,792 Water Body Type: Public Lakeshed:lake area ratio 1.6:1 Monitored Sites Mississippi River plus 101, 201 Inlets (Primary): numerous tributaries Monitored Sites 3901, 3902, 3903, 20501, Outlets 1 – Mississippi River (Secondary): 20502, 20503, 20504 Accesses 7 public Invasive species: none documented Data Availability Transparency data Transparency data only exist from 1976-1977 and 2008. Total Phosphorus and Chlorophyll a data have been Chemical data collected in 1994, 1999-2000 and 2008. Limited inlet and outlet data was collected for the Inlet/Outlet data Cass/Winnibigoshish CWP project in 1999-2000. Recommendations For recommendations refer to page 12. Lake Winnibigoshish Report generation: RMB Environmental Laboratories 1 of 13 Figure 1. Map of Lake Winnibigoshish illustrating bathymetry, lake sample site locations, stream inlets and outlets and aerial land use. The pink shaded areas in the lake illustrate the littoral zone, where the sunlight can usually reach the lake bottom allowing aquatic plants to grow. Lake Site Depth Monitoring Programs (ft) 101 36 MPCA: 2008 201 20 CLMP: 1976-1977; MPCA: 2008 3901 (20503) 30 Itasca SWCD: 1994; Leech Lake Band of Ojibwe CWP: 1999-2000 3902 35 Leech Lake Band of Ojibwe CWP: 1999-2000 3903 (20501) 65 Itasca SWCD: 1994; Leech Lake Band of Ojibwe CWP: 1999-2000 20502 50 Itasca SWCD: 1994 20504 35 Itasca SWCD: 1994 Lake Winnibigoshish Report generation: RMB Environmental Laboratories 2 of 13 The information below describes available chemical data for all sites of Lake Winnibigoshish through 2008. The data set is limited, and all parameters with the exception are means for just 1994, 1999-2000 and 2008 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. Impaired Ecoregion Waters Parameter Mean Range1 Standard2 Interpretation Total phosphorus (ug/L) 21 14 - 27 > 35 3 Results are within the expected range for Chlorophyll a (ug/L) 6 4 - 10 > 12 the ecoregion. For more information about Chlorophyll a max (ug/L) 17 <15 Impaired Waters Assessment, see page 12. Secchi depth (ft) 8 7.5 - 15 < 4.5 Dissolved oxygen see Dissolved oxygen depth profiles show that page 8 Lake Winnibigoshish is polymictic (mixes throughout the summer). Total Kieldahl Nitrogen 0.53 0.4 - 0.75 Indicates insufficient nitrogen to support summer nitrogen-induced algae blooms. (mg/L) Alkalinity (mg/L) 126 40 - 140 Indicates a low sensitivity to acid rain and a good buffering capacity. Color (Pt-Co Units) 18 10 - 35 Indicates moderately clear water with little to no tannins (brown stain). pH 8.3 7.2 - 8.3 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) 3.1 0.6 - 1.2 Slightly above the expected range for the Ecoregion, but still considered low level. Road salts used in the winter can run off into lakes when the snow melts, causing higher salinity. Total Suspended Solids 2.3 <1 - 2 Indicates low suspended solids and clear water. (mg/L) Conductivity (umhos/cm) 296 50 - 250 Slightly above the ecoregion average. High conductivity indicates high dissolved solids, which can come from watershed or human sources. Total Nitrogen :Total 25:1 25:1 – 35:1 Indicates the lake is phosphorus limited, Phosphorus which means that algae growth is limited by the amount of phosphorus in the lake. Data Source: Itasca SWCD 2004, Cleanwater Partnership Grant 1999-2000, Minnesota Pollution Control Agency 2008 1The ecoregion range is the 25th-75th percentile of summer means from ecoregion reference lakes 2For further information regarding the Impaired Waters Assessment program, refer to http://www.pca.state.mn.us/water/tmdl/index.html 3Chlorophyll a measurements have been corrected for pheophytin Units: 1 mg/L (ppm) = 1,000 ug/L (ppb) Lake Winnibigoshish Report generation: RMB Environmental Laboratories 3 of 13 Water Quality Characteristics - Historical Means Years monitored: 1976-1977, 1994, 1999-2000, 2008 Primary Site Site Parameters Site Site 3901 Site 3903 Site Site 101 201 20503 3902 20501 20502 20504 Total Phosphorus Mean (ug/L): 20 17 25 23 19 19 19 Total Phosphorus Min: 8 12 15 14 7 12 14 Total Phosphorus Max: 28 23 51 41 28 27 24 Number of Observations: 5 5 12 8 12 4 5 Chlorophyll a Mean (ug/L): 986 3 54 Chlorophyll-a Min: 5 4 2 1 1 1 Chlorophyll-a Max: 17 16 15 9 15 11 Number of Observations: 6 5 4 5 4 5 Secchi Depth Mean (ft): 10.0 7.4 Secchi Depth Min: 6.9 5.0 Secchi Depth Max: 13.5 13.0 Number of Observations: 5 39 Figure 2. Lake Winnibigoshish total phosphorus, chlorophyll a and transparency historical ranges. The arrow represents the range and the black dot represents the historical mean (Site 101). Figure adapted after Moore and Thornton, [Ed.]. 1988. Lake and Reservoir Restoration Guidance Manual. (Doc. No. EPA 440/5-88-002) Lake Winnibigoshish Report generation: RMB Environmental Laboratories 4 of 13 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. Transparency has only been monitored throughout the growing season (May-September) in 1976- 1977 and 2008. The transparency for these three years is relatively similar (Figure 3). The DNR has collected transparency data annually in July-August, but this data only represents one data point per year, so it was not used in this analysis. Transparency monitoring should be continued annually at sites 201 and 101 in order to track water quality changes. Since Lake Winnibigoshish is so large, each site can be monitored by a different volunteer, and the volunteers can make up a water quality task force. Figure 3. Historical transparency data for Lake Winnibigoshish. Lake Winnibigoshish transparency ranges from 5 to 13 ft at site 201. Figure 4 shows the seasonal transparency dynamics. Lake Winnibigoshish transparency is highest in May and then decreases throughout the summer. As with many lakes in northern Minnesota, transparency recovered somewhat in September-October. Transparency dynamics are related to algae population dynamics and lake turnover. Lake Winnibigoshish Report generation: RMB Environmental Laboratories 5 of 13 Figure 4. Seasonal transparency dynamics and year-to-year comparison (site 201). The shaded yellow line represents the average. 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 Winnibigoshish was rated as being "not quite crystal clear " 72% of the time in 1999 and 2008 (Figure 5). Physical Appearance Rating 14% 14% 14% Crystal clear water 72% Not quite crystal clear – a little algae visible 14% Definite algae – green, yellow, or brown color apparent 0% High algae levels with limited clarity and/or mild odor apparent 0% Severely high algae levels 72% Figure 5. Physical appearance rating, as rated by the lake monitor (1999, 2008). Lake Winnibigoshish Report generation: RMB Environmental Laboratories 6 of 13 As the secchi depth decreases, the perception of recreational suitability of the lake decreases.