Lakes and Water Quality – Constant Change

water qualityWhy does the water quality of our lake seem to get worse throughout the summer?

Lakes change a great deal over the course of a year. Changes are caused by seasonal weather patterns, watershed influences, and the life cycles of the lake’s biota. During the winter, ice and snow severely limit the amount of light available for photosynthesis under the ice, so there is not much algal growth. In the spring, snowmelt washes nutrients into the lake from the shores of your lakefront property. Many of the nutrients are used by rapidly growing aquatic plants (macrophytes) near the shoreline, resulting in a “clear water” phase.

As macrophyte growth slows in mid- to late-summer, incoming nutrients and nutrients from decomposing aquatic plants become available for algae. Available nutrients, combined with warm water and plentiful sunlight, can result in a period of heavy algal growth, potentially making the lake green and scummy. Mid-summer water quality problems may be particularly acute if you live on a shallow lake where high winds can mix warm surface water all the way down to the lake’s bottom waters. When this happens, nutrients are released from the mud and sediments up into the surface water where light is plentiful and algae can flourish. In autumn, the combination of decreased daylight, cooler temperatures, and more zooplankton grazing on algae, reduces algal growth and yields clearer water once again.


Posted by Scott Freerksen “The Lake Guy”

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