The water you don’t see and don’t hear is groundwater, the world’s invisible water storage system. National Groundwater Awareness Week, March 11-17, celebrates this little noticed natural treasure. Ohio has good reason to celebrate: it is fortunate in the amount and quality of its groundwater.

There is no better instance of the interdependence of all life than the cycle of groundwater.

Where does it come from?

Rain creates surface water, some of which feeds the rivers and streams and fills the ponds, but much of the rain soaks into the ground and moves deeper until it has filled all the cracks and pores in the rocks below. Aquifers occur where there are areas of sand, gravel or fractured stone that allow the stored water to flow. When our rivers flood, some of the floodwater may infiltrate aquifers through the flooded banks. We often speak of aquifers as “underground rivers” but they are not a river like a river in a cave, where the water can flow swiftly and there may be banks on the sides and airspace above. By comparison, groundwater flows slowly, only up to 50 feet in a day.

The best way to see groundwater is to take a look at steep, bare hillsides in the winter. Fall rains replenish groundwater, which keeps moving underground where it never freezes, and trickles out of aquifers in the hillsides, creating spectacular icicles and frozen waterfalls.

Even at its low rate of movement, groundwater supplies much as much as 80% of the water in streams and rivers. Between summer rainstorms and even in drought, walkers may notice small springs fed by groundwater that trickles streams and rivers.

Who uses groundwater?

Groundwater is also the source for well water, whether the well supports a single family, a family farm or even an entire community, as is the case for many small towns in Ohio. In 2013, Ohio’s groundwater withdrawals amounted to 727 million gallons per day, or more than 250 billion gallons per year. Surface water withdrawals amounted to more than The state’s largest consumers of ground water are public entities (461 million gallons per day).

At present, groundwater and other supplies are more than sufficient to meet Ohio’s needs.**But this good fortune is threatened by pollution and climate change.

Threats to groundwater

As it flows through the aquifer, groundwater can pick up substances that are present in soil or the stone. These include everything from excess or discarded chemicals to

minerals in the sands and rocks that are a natural part of the aquifer. Although humans cannot control every source of contamination, there are things we can do: test our wells, monitor our septic tanks, take leftover chemicals and paint to recycling, regulate our industry, maintain our sewage plants, and filter storm runoff, because all water eventually returns to earth after we use it.

Taking more water out of the ground than is naturally replenished will reduce the overall ground water supply. Rising temperatures from direct production of heat and releasing greenhouse gases that trap heat also reduce groundwater by accelerating evaporation, as will withdrawing groundwater for mining and industry and injecting it into deep wells after use. It is not known whether this contaminated water could work its way into groundwater.

Celebrate your groundwater this week

Our traditions don’t include parades, fairs and activities to celebrate our groundwater, but we can celebrate as families and friends to remind ourselves of the critical importance of the this resource. So tell the kids about groundwater, tie a ribbon around your wellhead, install a lowflow toilet or faucet flow restrictor, collect all those old solvents and paints that might go into thetrash and take them to the next recycling event.