“I hope we grow old, but we never grow up.”
- Niall Horan, Never Grow Up
It’s a fact of life – we’re aging. Time is moving forward each day. But age is just a number, right?
How we live each day affects our health and longevity. What we eat, how active we are, and the quality of our relationships with others affects how quickly our age shows on our face and body. Genetics also come into play in determining our baseline and susceptibility to certain health conditions.
Lakes are similar. After the glaciers receded, they left us over 10,000 lakes. Lakes go through a natural aging process where they gradually receive nutrients (phosphorus and nitrogen) and sediment from the surrounding land and become more fertile and shallow. This process is called eutrophication. Eutrophication is a natural process that a lake goes through over thousands of years. Lines of erosion through the landscape into lakes are like the lines that become more pronounced on our faces as we age.
Like our underlying genetics, lakes also have different starting baselines and susceptibility to certain health conditions. The geology and glacial formation of a lake usually determines its shape, size and depth. These factors contribute to nearly all physical, chemical and biological properties of a lake. Northern Minnesota was scraped fairly clean down to the bedrock, with boulders, sand and clay left behind, while southern Minnesota was left with a rich, fine prairie (now agricultural) soil.
Deep lakes have different dynamics than shallow lakes, and most of all, deep lakes have more water. The more water a lake has (volume), the better it is able to dilute what runs into it. Shallow lakes are lakes where the sunlight can reach the entire bottom. Generally, this corresponds to about 15 feet deep or less. Since the sunlight can reach the bottom, aquatic plants are able to grow there. In deep lakes, the bottom does not receive sunlight, so no plants grow there and it stays dark and cold.
Another major factor affecting lake condition is the size of its watershed and where the lake sits within the watershed. A watershed is an area of land where all the water drains into the same river system – water runs downhill.
This concept could be thought of as our ancestors and extended family. Certain characteristics and behaviors can pass down through generations, affecting our health today.
If a lake has a very small watershed or is at the top of a watershed (in topography terms), the lake usually has better water clarity than a lake at the bottom of a large watershed. As water flows downhill through a watershed it picks up sediment from erosion and nutrients from runoff. This sediment and nutrients can feed algae and cause the lake to become “greener”.
The modifications humans have made in the watershed affect the speed at which a lake ages. This aging is sped up by building impervious surface and tilling the land. Human-affected lake aging is called cultural eutrophication.
For us humans, preventative healthcare and a healthy lifestyle can help our overall quality of life and longevity. It can help us feel younger than our numerical age.
This is also true for lakes. If we prevent runoff and stabilize shoreline erosion we slow the aging process of a lake, and protect its water quality, helping it “stay young”.
I hope we grow old but we never grow up.
Moriya Rufer is a water quality professional with 20 years experience working with lakes in northern Minnesota.
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