Water

Ground Water in Indiana

by Robert T. Duncan

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Between 60 to 72 percent of Indiana's population relies on ground water for drinking and household uses. In 1995 it was estimated that 1.52 million people were supplied water from private domestic wells (Solly and others, 1998), and 2.1 million people were supplied by public water supply systems from a ground-water source. Approximately 303 million gallons per day of ground water was pumped by public water supply systems registered as significant water withdrawal facilities (100,000 gallons per day capacity) in 1992. Approximately 4,200 public water supply systems and countless industries use ground water as their source of water.

Ground water in the pore spaces between sand grains. Water is blue.

Despite its wide use as a source of water in Indiana, ground water is a poorly understood resource by most people. A mental picture of underground lakes or rivers may be the view many people have of ground water. Though this type of ground-water system exists under very specific geologic conditions, it is not the common ground-water system in Indiana. Ground water is subsurface water that fills all the pore space of soils and geologic formations below the water table (Freeze and Cherry, 1979). For ground water to be useful, it must be present in sufficient quantity, of good quality, and in the right kind of geologic formation to supply the intended use. When a geologic formation can provide water to a well, it is called an aquifer. Aquifers can be characterized by a variety of measurable attributes. Geologic formations composed of sand and gravel deposits or fractured limestone formations are commonly saturated with water and make excellent aquifers in Indiana. If the geologic formation is not sufficiently permeable to provide enough water for use, it is called an aquitard or aquiclude. In most cases it is easy to decide if something is an aquifer or not, but, in many cases, what makes an aquifer or aquitard is very dependent on where you are and what you want to do with the ground water.

There are two basic types of aquifers: confined and unconfined. Unconfined aquifers generally occur near the surface and the top of the ground water surface in this type of aquifer is called the water table. The tops of unconfined aquifers are often exposed to the surface or have a very thin covering of non-aquifer material. Confined aquifers usually occur at depth and are confined between two aquitards. In confined aquifers, the water level in a well will rise above the top of the aquifer.

Examples of common aquifer types in Indiana.

Usable, good quality ground water can be produced from within a few feet of the surface to several hundred feet below the surface. Ground-water use is heavily concentrated in the northern two-thirds of Indiana because the geology is favorable for highly productive aquifers.

In general, ground-water quality is good and ground water is safe to drink in Indiana. Natural constituents such as iron, manganese, sulfate, and hardness are common nuisances, but do not pose health threats. Naturally occurring contaminants are, however, occasionally found in wells above EPA-established health protection levels. Ground water can be, and has been, contaminated by human activities. How easily ground water is contaminated is dependent on the geology of the area and on how the contaminants are managed by people. Contaminants found in the ground water in Indiana include: industrial chemicals, nitrates from agricultural applications and waste water disposal, salt from salt piles and road applications, and gasoline and other petroleum products.

As is the case in other states, millions of dollars have been spent in Indiana on characterizing and cleaning up ground water, or on added treatment costs before the water is distributed to the public. In the city of Elkhart, over one million dollars was spent building large towers to remove solvents in the late 1980s. The system has been in use for a decade at an operational cost of $100,000 per year. The city of South Bend is building a similar treatment system to save a wellfield. In Valparaiso, the state of Indiana is cleaning up salt contamination in an aquifer used by the public water supply system. The projected cost of cleanup is over 1 million dollars and may exceed 3 million dollars. Millions more have been spent and will be spent in characterizing quality and implementing ground-water cleanups throughout the state.

Responsibility for protecting and characterizing Indiana's ground water is divided among a number of local, state, and federal agencies; the Indiana Department of Environmental Management, Indiana Department of Natural Resources, Office of the Indiana State Chemist, Indiana State Department of Health, Indiana Geological Survey, U.S. Geological Survey, and the U.S. Environmental Protection Agency are examples of such agencies. Because almost any human activity can have an impact on ground-water quality, we must envision the consequences of our actions. A little care and common sense can go a long way towards protecting the quality of this very valuable resource.

References

Solley, W.B., Pierce, R.R., and Pelrman, H.A., 1998, Estimated use of water in the United States in 1995. U.S. Geological Survey Circular 1200, 71p.

Freeze, R.A., and Cherry, J.A., 1979, Groundwater. Prentice-Hall, Englewood Cliffs, N.J., 604p.