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Sometimes ground water contamination occurs naturally. Acid rain is form of contaminated precipitation that will seep into the ground water. “Fortunately, most acid rain is neutralized (buffered) by soil and rocks so ground water is protected from the impact of acid rain.” (The American Well Owner) The most serious contamination is usually the result of human activities on the land surface. An aquifer provides a plentiful water supply that often attracts a multitude of people to the overlying land. The Water is used for such activities as drinking, personal hygiene, residential maintenance, and industrial and agricultural purposes. Many of these activities involve the use and disposal of chemicals, which are potential pollutants. When these chemicals are used or disposed of incorrectly unacceptable amounts can get into the ground water and contaminate it. Several valuable aquifers have been polluted by the people living and working above them

Most human activities at the land surface cause some change in the quality of water in the aquifer beneath them. The importance of the effect of a particular activity is related to the amounts and types of contaminants released. The severity of an occurrence is also related to the ability of the soil and ground water system to degrade or dilute the contaminants, and the degree to which the contamination will interfere with uses of the water. Contamination is usually more serious in a drinking water supply than in water for other uses. Except where contaminated water is injected directly into an aquifer, essentially all ground water pollutants enter the aquifer through recharge water from the land surface. Some examples of the contaminants are pesticides, certain petroleum products, mercury, nickel, lead, nitrate nitrogen, bacteria and viruses, and petroleum residues and combustion products from automobiles along roadways. All of these are considered harmful if ingested in sufficiently high amounts of drinking water, and in some instance may be carried into surface water bodies by ground water.

Each human activity has a particular impact on ground water. Some agricultural activities add nitrate, nitrogen and pesticides to the ground water. Residential areas add nitrate, nitrogen, and pesticides from landscaping activities. Those with septic systems usually add nitrate, nitrogen, bacteria, viruses, and synthetic organics used in household cleaning products and septic tank cleaners. Industrial activities tend to add organic chemicals and metals, through in widely varying amounts. Gasoline storage area (including service stations) may have leaks and spills of petroleum products. Roadways contribute petroleum pollutants leaked from vehicles and metals from exhaust fumes. The most concentrated impact comes from older sanitary landfills, whose leach ate may contain many different chemicals at relatively high concentrations.

Since ground water moves slowly, many years may pass before a pollutant released on the land surface above the aquifer is detected in water taken from the aquifer some distance away. Unfortunately, this means that contamination is often widespread before being detected. Even if release of the contaminant is stopped, it may take many years for an aquifer to purify itself naturally. Although water can be treated to remove contaminants, this can be very costly. The best protection against water pollution is prevention.

Ground water becomes depleted in areas where more water is being drawn out of an aquifer and consumptively used than is entering or recharging the aquifer. This usually causes a lowering of the water table, making the ground water more difficult and expensive to obtain. “Deserts have been expanding rapidly in China because of drought and sinking underground water tables depleted by industrial and agricultural use and population growth.” (Dust Storms Blast Beijing). Ground water depletion is a major problem in the dry western part of the United States. In the eastern United States, precipitation continuously replenishes ground water supplies, and so depletion is most likely to be a problem in certain localized situations, or during droughts. A situation may involve someone pumping a large amount of water from a small aquifer and causing a neighbor’s well to go dry (lowering the water table below the well screen). Rapidly expanding urban areas often impose an extra burden on ground water supplies in the form of depletion and pollution. In coastal area, chronic over pumping can cause saltwater intrusion. Salt-water intrusion takes place in coastal areas where fresh water removal from the aquifer permits saline water from the ocean to intrude into the aquifer.

Protecting our ground water from contamination will require thoughtful management and cooperation on the part of citizens and the various levels of government. In many cases, land use planning is the best instrument available for protecting aquifers still containing good quality water. If potential contamination sources are prevented from locating over critical recharge areas, the risk of contamination can be greatly reduced. Careful use and proper disposal of the chemicals causing contamination is also necessary. Industries, farmers, and homeowners located above ground water supplies need to practice good management with respect to the use and disposal of chemicals. Regulations, which govern the use and disposal of hazardous wastes, need to be enforced. An equally important step is to make people aware of their potential impact on ground water. Action is needed to protect our valuable ground water resources in many parts of the United States.

Is water an unlimited natural resource? No! Although it is still plentiful now it is important that we understand and

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