‹#› Southeastern Wisconsin Regional Planning Commission Big Cedar Lake Watershed Land Use and Pollutant Loading Update June 22 nd , 2020
Background and Goals ‹#› ➢ Most recent plan for Big Cedar Lake is MR 137 • Published in 2001; uses 1995 land use data ➢ Many conservation practices have been implemented since • Land easements and conservation • Stormwater management practices • Nonpoint source best management practices (BMPs) ➢ Goals: • Update land use and pollutant loading information • Evaluate changes since 1995 • Identify opportunities to enhance water quality protection efforts
1995 Watershed and Subbasins ‹#› ➢ Watershed is an area that contributes surface water runoff to a waterbody • Includes the waterbody itself • Boundaries determined by topography and hydrology • Groundwater is not generally considered in watershed delineation ➢ 1995 watershed area total was 6,641 acres • Included 932 acres for Big Cedar Lake • Contributing watershed was 5,701 acres ▪ Split into 20 subbasins
1995 Land Use ‹#› ➢ Agricultural and open land uses predominant • 3,056 acres (53% of contributing watershed) ➢ Surface waters, wetland, and woodland common • 1,428 acres (25% of contributing watershed) ▪ Includes 44-acre Gilbert Lake and 12-acre Mueller Lake ➢ Urban land use is largely residential • 746 acres of residential (13% of contributing watershed) • 476 acres of all other urban land uses combined
1995 Pollutant Loading ‹#› ➢ Different land uses contribute different types of pollutants • Rural uses generally contribute more phosphorus and sediment ▪ Can cause nutrient enrichment problems • Urban uses generally contribute more metals (e.g., cadmium, copper, zinc) ▪ Metals are toxic for humans and aquatic organisms above recommended levels ➢ Used land use data with pollutant models to estimate pollutant loads • 1995 land use used for pollutant loading in MR 137 ➢ 2,340 pounds of phosphorus and 670 tons of sediment loading per year to Lake • Primarily from rural land uses ➢ Metals loading determined to pose little threat to Big Cedar Lake
Changes in Land Use Mapping and Classification ‹#› ➢ Changes that affect comparison between 1995 and 2020 • Land use digitized in 2000 to match real property boundaries • Wisconsin Wetland Inventory in 2005 (WWI) • Reclassification of land use categories ➢ Difficult to distinguish changes in actual land use versus classification • Lake surface area and subbasin boundaries changed with digitization • Wetland acreages increased due to more accurate mapping • Roadside and open lands more explicitly mapped and classified ➢ Important to consider these effects for 1995 and 2020 comparison
2020 Land Use ‹#› ➢ Agricultural and open land uses still dominant, but fewer cultivated acres • 43% of contributing watershed • Open lands increased by 32% ▪ Land in conservation easements ▪ Conservation Reserve Program (CRP) ➢ 30% increase in residential land use • Little change in other urban uses ➢ Slight increase in wetlands and woodlands • Partially an artifact of WWI • May also reflect conservation efforts
2020 Pollutant Loading ‹#› ➢ Modeled nonpoint source pollutant loads • Phosphorus and sediment • Metals (cadmium, copper, and zinc) ➢ Subbasin 15 has highest total phosphorus and sediment loads • 1, 2, 11, 12, and 15 have highest loads per acre ➢ Decrease in pollutant loading since 1995 • Shift to less intensive rural land uses ▪ 14% decrease in phosphorus ▪ 20% decrease in sediment • Slight decrease in metals ▪ Likely mostly due to changes in mapping
Watershed and Subbasin Boundary Revisions ‹#› ➢ Watershed delineation updated to more accurately reflect current hydrology ➢ Subbasin 1 • Delineated internally draining areas north of STH 33 ▪ Do not contribute surface water to Lake ➢ Subbasin 13 ▪ Removed area that contributes to East Branch Rock River ➢ Subbasin 19 ▪ Former internally draining area now contributes to Lake ▪ Removed area that contributes to Washington Creek
Land Use and Pollutant Loading with Revisions ‹#› ➢ Revisions decreased watershed by 368 acres • 26 internally draining acres • Only Subbasins 1, 13, and 19 affected ➢ Mixture of land uses in removed areas • Agricultural, recreational, wetland, and woodland ➢ Further decreased watershed pollutant loads • 80 fewer pounds of phosphorus • 14 fewer tons of sediment • Slight decreases in metals loading
Nonpoint Source Load Reduction Goals ‹#› ➢ Big Cedar Lake watershed part of 2018 Milwaukee River TMDL • Impairments include degraded habitat, excessive algae, poor water clarity • Phosphorus and suspended solids (sediment) are identified pollutants • Watershed discharges into impaired Cedar Creek ➢ TMDL sets watershed pollutant reduction goals for Cedar Creek (MI-18): Nonpoint Source Non-permitted Pollutant Pollution Sources Urban Sources MS4 Systems Total Phosphorus 40% 69% 68% Total Suspended 63% 72% 71% Solids
Ongoing Efforts to Reduce Nonpoint Source Loads ‹#› ➢ Many active organizations implementing conservation practices within the watershed • Big Cedar Lake Protection and Rehabilitation District • Big Cedar Lake Property Owners Association • Cedar Creek Farmers • Cedar Lakes Conservation Foundation • Town of West Bend • Washington County ➢ Constructed stormwater basins, drainage channels, and other BMPs to mitigate pollutant loads ➢ Increased acreage of lands in easements and CRP
Opportunities to Reduce Loads in Urban Areas ‹#› ➢ Meet or exceed MS4 permit requirements • Improve existing BMPs and develop informational workshops ➢ Enhance stormwater management infrastructure • Direct runoff into vegetated buffers and swales ▪ Install ditch turnouts and ditch checks • Require green infrastructure/low impact development ➢ Reduce pollutants from residential areas • Enhance shoreline and riparian vegetation buffers ▪ Funding through WDNR programs • Direct roof and driveway runoff into rain gardens • Avoid pollutant spills and excessive use
Opportunities to Reduce Loads in Rural Areas ‹#› ➢ Support and collaborate with producer-led groups • Recruit to install low-cost BMPs • Provide education and outreach opportunities • Offer financial support to purchase key equipment for agricultural BMPs ▪ Cover crops, no-till, buffers ➢ Sponsor grant applications • Surface Water Grants Program (now NR 193) • Targeted Runoff Management Grant Program • Urban Nonpoint Source and Storm Water Management Grant Program
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