By Mike Ekberg, MCD water resources manager
Stories about droughts, water shortages, and aquifers drying up are in the news with regularity these days, especially in places throughout the western United States.
What are the chances that our aquifer could run dry? Are the water levels in the Great Miami River Watershed and its buried valley aquifer increasing, declining or staying the same?
According to the measurements taken by MCD over the last 30 years, the water supplies in the Great Miami River (GMR) Watershed are in what’s called a steady state. That means the amount of water that flows into and out of the watershed – the 4,000 square miles of land that drain to the Great Miami River – is relatively constant over the last 30 years.
In 2014, the Great Miami River Watershed received 39.05 inches of rain and snowmelt (inflows) – which matches the long-term average. That amount of water equals 2.7 trillion gallons of water.
Water leaving the region through evaporation and plant uptake (outflows) averages about 26 inches or nearly 1.8 trillion gallons.
On average, another 900 billion gallons of water flows into the Great Miami River through runoff each year. Runoff is water that flows over the land (overland flows), runs through soils (interflow) and into the aquifers (groundwater flow).
That’s 2.7 million gallons into the watershed and another 2.7 million gallons out of the watershed.
There are fluctuations in water levels year to year, but over the long term, precipitation and runoff balance each other out, leaving the total amount of water stored in the Great Miami River Watershed essentially the same.
Another factor in water usage is human use. The Ohio Department of Natural Resources says people use about 124 billion gallons of water per year, mostly for public water supply, industry, and cooling water for power generation. Most of that water returns to the Great Miami River Watershed through municipal sewer and industrial wastewater treatment plants. Of the 124 billion gallons of water used by people, MCD estimates only about 23 billion gallons of water is actually consumed or removed from the watershed before it reaches the Great Miami River. Although 23 billion gallons of water sounds like a huge quantity, it’s only a small amount when compared with the 2.7 trillion gallons that enter and exit the watershed each year.
While our water levels are steady today, that’s no guarantee for the future. Changing weather patterns and increasing water uses by people are unknown. That’s why it’s critical to track water over time and why MCD measures precipitation and river flows throughout the watershed using a network of gages.
Keeping an eye on water levels is vital to detecting trends so that policies and programs can safeguard our water supplies.