Changes in groundwater levels?

By Mike Ekberg, Manager for Water Resources Monitoring and Analysis

Groundwater levels in the aquifer beneath downtown Dayton fluctuate throughout the year. Locally, groundwater levels often peak in winter or spring and decline to their annual low in the fall. However, we’re seeing changes to the normal up-and-down cycle of groundwater in the aquifer in a couple of downtown wells.

Graphic of depth to groundwater

Groundwater levels fluctuate throughout the year. But the annual low groundwater level at the Apple Street and South Main Street observation well shows a decline over the past 25 years.

The annual low groundwater levels in two downtown observation wells are showing a distinct downward trend, declining as much as 25 feet over the past 10 years. In fact, recent groundwater levels at both wells tend to be below monthly normals for much of the year. What’s causing the drop?

Geothermal systems may be the reason
An increase in geothermal heating and cooling systems in Dayton may be the cause. In the last 15 years or so, several buildings in downtown Dayton installed open loop geothermal systems. Open loop systems pull groundwater from high-capacity wells —tied to the aquifer beneath Dayton—to create heat and air conditioning.

If too many geothermal systems draw water from the same area, that could cause a significant drop in average groundwater levels. That’s happening now in these two wells in downtown Dayton. And yet, these wells—and the Dayton area–still have plenty of groundwater

Water supply safe
Is the aquifer going to go dry? Not likely. The buried valley aquifer, which stores this region’s groundwater, holds 1.5 trillion gallons of water. That said, in areas where a lot of groundwater is pulled from the aquifer, it’s possible for one well to cause another well to go dry. This situation is most likely to occur during summer months when water demand for cooling systems peak.

MCD tracks groundwater levels at more than 100 monitoring wells in the region. The City of Dayton tracks groundwater levels at more than 300 monitoring wells throughout its well fields and within the aquifer. City officials say their well field areas are not impacted by the pumping of groundwater downtown.

Can geothermal systems continue to be a workable option for Dayton buildings? Yes, provided there’s a plan to balance the number of systems and well locations.

Better water planning prevents problems
Steps to ensure this balance include:

  1. Inventory high-capacity geothermal wells in the downtown area.
  2. Fully understand current groundwater levels throughout the area.
  3. Assess the potential impact of new geothermal wells on existing wells and storm sewers.
  4. Site wells strategically.

With these steps, Dayton—and other cities—can ensure existing geothermal systems will not be harmed by adding new systems, and all the systems will be sustainable.

 

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Where’s the best tasting water in the world? Hamilton, Ohio, of course

By Mike Ekberg, water resources manager

The City of Hamilton has created the best tasting water in the world using groundwater from the Great Miami River Buried Valley Aquifer. The city received the gold medal for Best Municipal Water at the 25th anniversary Berkeley Springs International Water Tasting in West Virginia held in February.

What is this “aquifer” anyway?

Think of the Great Miami Buried Valley Aquifer as a giant container with porous sand and gravel that can trap and hold water. Have you ever poured a bucket of water into sand? The sand absorbs the water quickly and it disappears from sight. A sand and gravel aquifer soaks up water in a similar way.

Where is it and where did it come from?

The buried valley aquifer generally underlies the Great Miami River and major tributaries such as the Stillwater and Mad rivers and Twin Creek.  The sand and gravel deposits that make up the buried valley aquifer were deposited by ancient rivers that existed before the present day Great Miami River took shape. These ancient rivers carried large amounts of water from melting glaciers during the end of the last ice age.

Map showing the location of the buried valley aquifer (light blue) in relation to the Great Miami River drainage area.

Map showing the location of the buried valley aquifer (light blue) in relation to the Great Miami River drainage area.

How much water?

The buried valley aquifer is the most productive aquifer in the Great Miami River Watershed. Municipal drinking water wells, like the city of Hamilton’s, can sometimes yield more than 3,000 gallons per minute. In comparison, there are many places in Ohio where wells can produce no more than 25 gallons per minute and often fewer.

Large groundwater yields are possible because:

    • Our region receives abundant annual precipitation in the form of rain and snow which resupplies the buried valley aquifer.
    • The buried valley aquifer is able to absorb large quantities of water quickly.
    • The groundwater in the buried valley aquifer interacts with the water in the Great Miami River and can supply each other with water.
    • Most of the water pumped out of the buried valley aquifer is returned to the Great Miami River Watershed when wastewater is discharged in the streams and rivers. This offsets water losses that occur when some of the water  is pumped out of the aquifer and released into another watershed. For example, groundwater is used in the production of beer, which could be shipped outside the watershed for purchase.
Graphic showing interconnected nature of the buried valley aquifer and the Great Miami River

This graphic shows the interconnected nature of the buried valley aquifer and the Great Miami River. Water normally flows from the aquifer to the river (top), but flows often reverse during floods.

How the aquifer improves our lives

Besides being the main source of drinking water for a majority of communities along the Great Miami River, the buried valley aquifer:

  • Provides our region with a safe and plentiful supply of water that can be treated to drinking water quality standards fairly inexpensively when compared with using water from a rive lake.
The buried valley aquifer is our region’s #1 source of drinking water.

The buried valley aquifer is our region’s #1 source of drinking water.

  • Supplies businesses and industry with a reliable supply of water. For example, the Miller Coors Brewery in Trenton uses water from the buried valley aquifer for its brewing process.
  • Improves the quality of life in the region by providing continuous flow to the Great Miami River even during dry periods. This flow sustains water for fish habitat and makes the Great Miami River attractive for kayaking and rowing. For example, nearly half of the annual water flow in the Great Miami River at the city of Hamilton comes from the buried valley aquifer.
  • Provides potential geothermal heating and cooling opportunities. Groundwater in the buried valley aquifer remains around 56 °F year round and can be used by geothermal heating and cooling systems.

If the water in the aquifer was polluted or depleted, our region would be less resilient in coping with drought conditions, seasonal water shortages might be more commonplace, and communities might have to pay for more expensive treatment to make the groundwater safe for drinking. .

So, while the city of Hamilton’s water received the gold medal at the Berkeley Springs International Water Tasting, it’s clear our buried valley aquifer made the award possible. Yes, our buried valley aquifer is worthy of a top prize.