We only have so much groundwater

Drainage ditch,
A drainage ditch between a field and road.

When you see the earth’s surface on a globe, all of the blue gives the illusion that we have water o’plenty!

But in reality, once you “hold the salt” water in oceans (97 percent) and “put the freeze” on water trapped in ice caps and glaciers (2 percent), suddenly 99 percent of the water on Earth is not directly usable by humans.

Our remaining fresh water supplies are either stored beneath the ground (in soil or fractured bedrock) or in surface water (in streams, rivers, and lakes). Of this, a mere 1 percent of fresh liquid water that we can use and which our survival depends, more than 98 percent exists beneath the land’s surface.

Water underground

Groundwater is water found below the land’s surface and fills the spaces and cracks between soils, sand grains and rocks.

If this saturated area, or zone, is capable of storing and yielding groundwater to a well, it is called an aquifer.

Aquifers are composed of permeable sediment or rock of which Ohio has three major types: sand and gravel deposits, sandstone bedrock, and carbonate bedrock (limestones and dolomites).

Here in the Heartland, our average precipitation is between 30 to 44 inches per year. As this rain and snowmelt soak into the ground, most is taken up by plants or soil, while some slowly seeps into the layers of pore space.

Replenishing aquifers

Approximately 3-16 inches of Ohio’s annual rainfall replenishes our aquifers in this process called “recharge.” The top of this saturated zone is known as the water table and water tables vary in depth — rising during wet seasons and falling deeper during dry seasons. Lakes, rivers, streams and ditches also recharge aquifers.

As part of the water cycle, groundwater does not remain stagnant underground, but moves very slowly from upland to lowland … sometimes only a few feet each year.

In Ohio, we are fortunate to have abundant groundwater resources. Approximately 45 percent of Ohioans depend on groundwater for their homes, businesses, schools, industries, farms and drinking water supplies.

Collectively, we consume more than 1 billion gallons of groundwater each day. Yet our connection to groundwater’s significance seems to be buried deeper than the water itself.


Groundwater is an especially fragile resource that is very slow-moving, mostly unseen, sluggish to recharge, and incredibly difficult to clean. So it’s incredibly surprising how ill-equipped and unarmed we are in the realm of groundwater protection.

The risks of groundwater contamination and the price of cleanup are far greater than most communities could ever imagine or afford. Groundwater contamination occurs when man-made or even naturally occurring materials seep into groundwater supplies and render it unsafe and unfit for human use.

Examples of potential pollutants include household hazardous wastes, leaking underground storage tanks and landfills, failing septic systems, runoff including fertilizers, pesticides, animal wastes, chemicals and road salt, and naturally-occurring arsenic, lead, methane, radon and other elements or gasses.

Protecting groundwater

As homeowners and residents, we can and must protect and preserve our groundwater.

The first and most critical step is that we strive to be “well educated.”

Over the past 30 years, the U.S. Centers for Disease Control and Prevention found an increased proportion of waterborne disease outbreaks associated with private household drinking water supplies, with the majority of documented outbreaks caused by groundwater.

While routine testing ensures state and federal standards in public water supplies, it is the primary responsibility of the individual well owners to ensure that the water drawn from their wells is safe.

In Ohio, more than 700,000 people have their own wells. Routine monitoring of your water well is extremely important, not only to determine the current water quality, but also to provide a baseline of quality and the ability to detect changes in future water tests.

The Ohio Department of Health recommends that private water system owners test total coliform bacteria, E. coli, nitrates, and arsenic annually as well as any time there is a change in taste, odor, or appearance of your drinking water.

In addition to your water chemistry and bacteria tests, your annual water supply maintenance check should also include a static water level check, a water yield test, and a visual inspection of the well cap and cover.

Knowing the drill

If planning a new or replacement water well, contact your local health department to begin the process of obtaining a well permit. A lot evaluation is required by a registered private water system contractor.

The Ohio Department of Health requires every well to have a permit prior to being drilled. Private water system permits are good for one year.

Within this timeframe, the installation or alteration must be performed, the system must pass a final inspection, and the water supply must pass a water test through a state-certified water testing lab.

Learn more

For more information on water well maintenance, visit odh.ohio.gov, epa.ohio.gov/home, your local health department, the Ohio Watershed Network (ohiowatersheds.osu.edu), or your local Soil and Water Conservation District.


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