• Lake Aging

Your Lake is Aging. Help The Process Go Slowly.

From the time our lakes were formed by the glacier, they began to age. Over many thousands of years, every lake goes through a slow process in which plants grow and die, streams and runoffs bring in sediment and the lake bed fills in.

Some lakes age faster than others. For example, deep lakes with rocky bottoms and fed by groundwater springs tend to age very slowly. Shallow lakes with soft bottoms friendly to weed growth, and with streams flowing in tend to age faster.

One indicator of how fast a lake will age is its trophic state – how rich it is in nutrients that cause algae and weeds to grow. Scientists place lakes into three basic trophic states: oligotrophic, mesotrophic and eutrophic.

  • Oligotrophic lakes (“oligo” means “few”) are poor in nutrients. They tend to be deep with sandy or rocky shorelines. The water is clear; weeds and algae are sparse. These lakes age slowly.
  • Eutrophic lakes, on the other end of the scale, tend to be shallower with mucky bottoms. In the summer, they become very green with algae and choked with weeds. These lakes age very quickly.
  • Mesotrophic lakes fall between the two extremes. Many northern Wisconsin lakes are mesotrophic.

The basic difference between these lake types in the level of nutrients in the water. Development of homes and businesses tends to accelerate lake aging, as it can add nutrients through erosion, lawn fertilizer runoff and failing septic systems.

By following good management practices, each lake association and each property owner can help limit the addition of nutrients and let lakes age naturally – which is to say, more slowly.

Did You Know? Your septic system should be inspected each year and pumped out every three years to keep it working properly and protect lake water quality.

NOTE: This is one in a series of articles sponsored by OCLRA (www.oclra.org) and will be made available to you on this website over the next year. A new article will appear every month or so.

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