Great Miami Buried Valley Aquifer

Not all rain or snow that falls within the Great Miami River Watershed flows directly into the Great Miami River. Some of it seeps into the ground and into the Great Miami Buried Valley Aquifer (GMBVA). With its abundant supply of high quality groundwater, the GMBVA is the most important aquifer in southwest Ohio. This system consists of highly permeable sand and gravel deposits as thick as 200 feet that can store approximately 1.5 trillion gallons of groundwater. An estimated 97 percent of the population (2.3 million people) in the Great Miami River Watershed relies on its groundwater for their drinking water supply. The GMBVA yields in excess of 2,000 gallons of water per minute are possible in wells near large streams, and much of the groundwater maintains a constant temperature of 56 degrees Fahrenheit.

Sole Source Aquifer Designation

The U.S. EPA designated the GMBVA as a sole source aquifer in 1988. A sole source aquifer designation applies only to aquifers that serve as the sole or principal source of drinking water for an area. This designation signifies that contamination of the aquifer would create a significant hazard to public health. Aa result of this designation, all federally funded projects constructed near the aquifer, and its principal recharge zone, are subject to U.S. EPA review. This insures that projects are designed and constructed in a manner that does not create a significant hazard to public health.

Importance of Protecting Groundwater - Be Water Wise!

The groundwater in the buried valley aquifer provides flow for the Great Miami River; In turn, the Great Miami River helps recharge water levels in the aquifer. This means that our drinking water resources are vulnerable to sources of pollution and contamination that happen at the surface and in our rivers. It is important for all of us to take action in our daily lives - and it can be quite easy too! 

Learn how to be water wise with these 9 tips

What is an aquifer?

An aquifer is an underground reservoir, made up of layers of soil, sand, gravel or rock that can be saturated with groundwater. Aquifers generally hold sufficient water to be used as a water supply. There are two basic types of aquifers:

• Unconfined aquifers are made up of loose, coarse sediments such as sand and gravel. In this type of aquifer, groundwater moves between the sediment particles. In general, groundwater flows from high areas to lower areas and generally mimics the direction of flow of the streams and rivers that lay above it. The Great Miami Buried Valley Aquifer is an unconfined aquifer.
• Confined aquifers are a solid formation of rock lying beneath the surface of the soil containing enough water in its cracks and small spaces to provide water for wells. Confined, or 'bedrock aquifers' are the source of many private drinking water wells in the Great Miami River Watershed, and generally produce enough water for residential home use. In bedrock aquifers, groundwater can move between the sediment particles (in cases like sandstone) or it can move along fractures within the rock. In the Great Miami River Watershed, you would not find underground caves filled with flowing water, though there are a few places in Ohio where you would find this type of geology.

Some Other Useful Terms

• A water table marks the highest level of the groundwater beneath the ground's surface.
• The area between the ground's surface and the water table is called the unsaturated zone, or zone of aeration. In this zone, you will find some water, but you will also find air filling the spaces between soil and rock particles. Any water in this area, called soil moisture, could be used by plant roots. The entire area below the water table is the saturated zone. This zone marks the area where every pore or crack in soil and rock is completely filled in (saturated) with water.