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Focus on Agriculture

For the week of March 12, 2012

Groundwater: Out of Sight, But Not Out of Mind

By Kevin McCray

Some 44 percent of the U.S. population depends on groundwater, the water that fills cracks and other openings in beds of rock and sand, for its drinking water supply – be it from either a public source or private well. In rural areas, the number is about 96 percent. That fact alone justifies the need for National Groundwater Awareness Week, March 11-17. But groundwater is important to us in many other ways, as well.

Groundwater provides much of the flow of many streams; often lakes and streams are “windows” to the water table. Groundwater adds 492 billion gallons per day to U.S. surface water bodies. In large part, the flow in a stream represents water that has flowed from the ground into the stream channel.

Scientists estimate U.S. groundwater reserves to be at least 33,000 trillion gallons – equal to the amount discharged into the Gulf of Mexico by the Mississippi River in the past 200 years.

The U.S. uses 79.6 billion gallons per day of fresh groundwater for public supply, private supply, irrigation, livestock, manufacturing, mining, thermoelectric power and other purposes.

Groundwater is tapped through wells placed in water-bearing soils and rocks beneath the surface of the Earth. There are nearly 15.9 million of these wells serving households, cities, business and agriculture every day. Wells are constructed by the 8,100 contracting firms employing nearly 45,000 people dedicated to providing and protecting our nation’s groundwater supplies.

Irrigation accounts for the largest use of groundwater in the United States, about 67.2 percent of all the groundwater pumped each day. Some 53.5 billion gallons of groundwater are used daily for agricultural irrigation from more than 407,913 wells. Irrigation is a major reason for the abundance of fresh produce and grains that we all enjoy.

One ton of groundwater used by industry generates an estimated $14,000 worth of output.

These facts help us connect with the important role we each play as stewards, or protectors, of groundwater. Fortunately, there are simple steps that will help protect groundwater and the well systems that distribute it.

Always use licensed or certified water well drillers and pump installers when a well is constructed or serviced, or when the pump is installed or serviced.

Keep hazardous materials away from any well. Never dump such materials, motor oil, or anything else that could impact water quality onto the land surface, into a hole or pit, or into a surface water supply.

These tips and more are available from state groundwater or water well associations, NGWA, county agricultural Extension agents or state government agencies with responsibility for groundwater. Visit www.wellowner.org to learn more.

National Groundwater Awareness Week is not a celebration such as July 4th has become. Instead, we should use the week to reflect more deeply on groundwater’s value and its contributions to our lives.


Kevin McCray is the executive director of the National Ground Water Association.