Deep or Shallow, Our County's Aquifers Need to be Conserved

All of the water we humans use in McHenry County comes from the ground. Municipal and private wells reach down into “groundwater aquifers” and pump water up for our use.

Aquifers are not underground pools. Based on information presented by Baxter & Woodman consultants at recent public meetings about groundwater in McHenry County, local aquifers are found where deposits of sand, gravel, or sandstone have water filling the spaces between sand particles (or filling cracks in the rock).

Sand & gravel aquifers are found up to 400 feet below the surface in this area. The deposits were left by the glaciers. Water actually filters down to them from the surface, perhaps taking 50 years to reach the aquifer so it can be pumped to the surface again. The City of Woodstock has six wells that extend down about 180 feet into sand and gravel aquifers. The wells can supply up to 6.8 million gallons a day. Average water use in the City is 3.6 million gallons each day.

Sandstone aquifers are up to 1300 feet below the surface. Sandstone formations are actually the remnants of ancient sea beds that were – over millennia – compressed into stone. Water from the surface eventually makes it all the way down to these ancient rocks – perhaps taking a couple of hundred years to filter down. The water that is slowly moving into these sandstone aquifers under McHenry County actually comes primarily from Boone County!

There is a lot of water under McHenry County. Most of it is found in the shallow sand and gravel aquifers. However, because water from the surface travels relatively quickly through the gravel, this water is at higher risk for pollution than the deeper aquifers.

If the deep aquifers are less likely to be contaminated, why wouldn’t we get all of our water there?

The deep aquifers have much less water in them than the shallow ones. Water experts estimate that we should only be drawing 6 million gallons a day, otherwise we are actually “mining” the aquifers. Mining is when you remove the water faster than it can be replenished (“recharged”). It is estimated that wells in the county already pull a total of 18 million gallons a day from the sandstone layer. This is not sustainable – those aquifers will eventually run dry.

There are a few simple things we can do to help ensure we continue to have ample water resources:

• Stop treating stormwater as a waste product that is sent “away” as quickly as possible. Slow it down, let it soak into the ground and recharge aquifers instead. Individuals can install “rain gardens” to catch run-off on their own properties.
• Protect farmland as a way to ensure groundwater recharge. All those farm fields do more than grow food – they also allow water to soak into the ground.
• Use native plants in our landscaping. Water use peaks in the summer when we water our thirsty lawns and landscaping. Many native plants are drought tolerant once established. They also reduce stormwater runoff and increase infiltration of water.

We have the opportunity in McHenry County to meet current and future water needs with the water resources that are available to us right beneath our feet – if we plan for it. Planning must include preserving water quality as well as managing supply and demand.