phosphorous include fertilizers from lawns and gardens, leaves and grass clippings, pet and wildlife waste, and automobile emissions. CRWD is within the Northern Central Hardwood Forest (NCHF) ecoregion. It is one of seven ecoregions in Minnesota and is characterized as an area with fertile soils with agriculture as the dominant land use in rural areas. In most lakes in the NCHF ecoregion, phosphorous is the least available nutrient; therefore, the concentration of phosphorous controls the extent of algal growth. Algal growth in turn affects the clarity and recreational potential of lakes. Chlorophyll-a (Chl-a) is a pigment present in algae. Measuring Chl-a concentration is a proxy for measuring algal population. Algal blooms can make recreation unpleasant and prevent it entirely, and certain species of algae are toxic to humans and other animals. In addition, as algae die and decompose, oxygen is consumed from the water column and made unavailable for fish and other aquatic animals. Chronic low dissolved oxygen concentrations (<5 mg/L) may result in fish kills and low diversity of aquatic species (Kalff, 2002). Sediment is another major constituent of stormwater runoff. Excessive amounts of sediment negatively impacts water clarity and impairs benthic aquatic habitat. The reduction or removal of sediment from stormwater is essential because other pollutants, such as phosphorus, adhere to sediment particles and are transported in suspension. Sediment originates from erosion of soil particles from construction sites, lawns, stream banks, and lake shores as well as sand application to roadways and parking lots for traction in the winter. Water transparency, or water clarity, (determined using a Secchi disk) is another concern in area lakes. Lakes with high water clarity are generally considered healthier, and are characterized by more submerged aquatic plant growth, as clear water allows light to permeate to lower depth levels (Kalff, 2002). Increased plant growth also provides better habitat for aquatic organisms, including fish. Poor water clarity is a result of increased turbidity caused by suspended sediments, organic matter, and/or phytoplankton (algae). Heavy metals, such as lead and copper, are also pollutants of concern in CRWD because they can be toxic in high concentrations. Also, heavy metals can bioaccumulate in organisms, which is of concern to wildlife and humans. Potential sources of metals from road surface runoff include auto exhaust, tire wear, brakes, and some winter de-icing agents. Pathogens, which include bacteria and viruses, also contribute to the water quality degradation of CRWD water resources. They impact recreation and pose potential health risks to humans. Sources of pathogens include illicit sanitary connections to storm drains, and animal waste. Chloride in water bodies is a contaminant of concern for CRWD. High concentrations of chloride can harm fish and plant life by creating a saline environment. Also, once in dissolved form, chloride cannot be removed from a water body. Chloride is primarily sourced from road salt application for de-icing in the winter months.
2013 CRWD Lakes Monitoring Report
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