What is Groundwater?

May 12, 2020 by SWCD

What is groundwater?

Groundwater is the water beneath our feet—the stuff underground, stored in the cracks and spaces between soil, sand, and rocks. Groundwater is stored in aquifers, which are underground formations of permeable rock or loose material which can produce useful quantities of water when tapped by a well. It’s easy to think of an aquifer as a large underground lake, just keep in mind that it’s not usually a cavern filled with water but a layer of soil and rock with water filling all the tiny spaces, kind of like a saturated sponge.

Here’s a little visualization: remember days spent at the beach when you were little? Did you ever dig holes in the sand, only to have them seep full of water? That is the water table, the area where the ground is permanently saturated with water. Aquifers work the same way. Groundwater in aquifers comes to the surface in springs, seeps into lakes and streams, and is pulled up through wells.

In Minnesota, groundwater supplies 75% of our drinking water and 90% of our agricultural irrigation water. A lot of that irrigation is centered around Otter Tail County, where the crops benefit from irrigation because our sandy soils don’t hold a lot of water. We depend on plentiful and clean groundwater, not only for the water we drink but also for the food we eat.

The availability of groundwater depends on the bedrock, types of soils, and the history of glaciers, and these all play off of each other. The glaciers that covered our part of the state many, many years ago left lots of sand in their wake, which water runs through very easily. Deeper down, the water collects in vast sand beds easily, and this is where we draw much of our water from. While this sand makes it easy to draw water from the aquifer, it can also make it easy for contaminants to get to the groundwater.

In our area, one of the primary contaminants we worry about is nitrates. Nitrogen, used by farmers to fertilize their crops and landowners to fertilize their lawns, easily passes through the soil and enters the groundwater. When it is pulled back up with our drinking water, it can cause health concerns, especially in infants and elderly. Overapplication of fertilizers, failing septic systems, and pets and livestock all can contribute to high nitrates in drinking water.

There are a few easy ways we can all protect the groundwater we drink. Use best management practices for applying fertilizers or pesticides on crops or lawns and use native plants that don’t need water or fertilizer in your gardens. Get your septic system inspected and fix any problems (ask Otter Tail County Land and Resources about any available grants to help you do so), and dispose of all household hazardous waste appropriately. It’s easy to just turn on the faucet and not think about where the water comes from, but hopefully now it’s a little easier to see all the ways we impact the water we drink!

For a great video on groundwater, check out https://www.youtube.com/watch?v=gxENTkMmyEE

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