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| December 14, 2020 Post 120 |
| groundwater and lake water |
Mysterious, silent and mostly unseen, water cycles endlessly throughout our world. It’s said that our world’s water supply was established eons ago, and we still aren’t certain where it all came from. Ultimately, though, we do know it came from the stars through the process of atomic fu
When we consider water, often we think of the ocean, or perhaps a river or a lake. But close to a third of the planet’s total freshwater supply, consists of ground water, while most of the rest of our water is locked up in ice.
Twice I have found springs on the beach both times at the base of a lake shore bluff. I knew it was ground water because the iron rich seeps and little pools were above the level of the lake and the rust stained pebbles bordering the seep testified to its duration.
Ground water is a mystery to most. Springs seem nothing short of miraculous. As a kid I longed to find a clear cold pure spring bubbling up out of the ground somewhere on our land. Maybe those childhood tales of water sprites associated with magical springs fueled my search.
Ground water resides in aquifers, saturated areas of sand, gravel or silt that lie at varying depths beneath the surface. Rather than an underground river, an aquifer is more like a saturated sponge. However, water does move within an aquifer. Where and how quickly it moves depends on the surrounding rocks and soils and other subsurface geology. It can and does interact with flowing creeks and rivers, too. Sometimes the surface water moves into and recharges the aquifer beneath. And sometimes the aquifer feeds the river o
Last spring rapid erosion of the lake shore bluff bases revealed some odd little caves and caverns at several locations near Fair Haven. Puzzled by these I sent a photo to a geologist who recently had published a paper on the interior structure of our ice age drumlins. He replied that these were formed from groundwater seeps. ( See photo of me above in one of these “caves”.) I noticed a distinct vein of gravel within another one and wondered if this could have been part of the aquifer.
As many country dwellers with less than generous well water supplies know, aquifers are limited in quantity. Two of my former homes had hand dug shallow wells. In the spring the water lay just a few feet down but by fall the shallow wells were low or even totally dry. Aquifers are mainly recharged by precipitation that falls, soaks into the ground and slowly percolates into the soil. That’s why when the forests were logged off two hundred years ago, many springs and small creeks by the lake dried up. Rapid runoff prevents rain from recharging aqui
In the spring sometimes you may see a dark line of wet soil running across a bluff face often near the top as in the photo. This corresponds to an aquifer perched high above the lake. But later in the summer the distinctive dark streak disappears.
Ground water helps stabilize the marshes and wetlands along our lake shore. It’s estimated that the total volume of groundwater within the Great Lakes basin is about equal to that contained within Lake Michigan. Its interaction with Lake Ontario is not well understood, but we can be certain that it exists and affects the lake’s water quality. A hydrogeologist Dr. Audry Sawyer, who works at Ohio State, says that our aquifers are an ‘undervalued resource’ in need of further study.
He’s quoted on line saying, “There are many times when the groundwater quality is much better than the surface water lying above it, so we want to protect aquifers and keep them as pristine as we can, because they’re a nice back-up resource when there are times we can’t
But because they are out of sight and out of mind and because the water moves slowly he adds “I think it’s easy to mismanage them, pump dry and deplete, because there are fewer stewards for them.”
Find an interesting video here (select and paste link into url bar as I don’t know how to make it ‘live’)
https://www.greatlakesnow.org/2019/09/aquifer-groundwater-great-lakes/
This video shows how one aquifer interacted with another. As in the town in the video, my childhood home in western Wayne County near the lake had a deep water well that was salty and a shallow water well with good quality but inadequate quantity. This town in the video spent big bucks to connect to Lake Michigan after it ran out of groundwater.