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Ground Water Environmental Geography Essay, Research Paper

Western Carolina University

The Importance of Ground Water

Environmental Geography 150

29 November 2000

Justin Bono

Many people assume that water is an unlimited natural resource. Is this true? Although water appears abundant, recent circumstances indicate that it is seriously vulnerable to pollution and depletion. Throughout this essay we will examine what ground water is, how it is important in the water cycle, how it’s contamination can affect us, and what we can do to protect our ground water from contamination.

Ground water is the water found in spaces between soil particles and rocks, within cracks of the bedrock. “Ground water constitutes approximately 4% of all water in the hydrologic cycle.” (Averett, McKnight, 1986) Some ground water can be found beneath the land surface in most of the United States. Because of its availability and general good quality, ground water is widely used for household needs and other purposes.

Water can be found beneath the ground almost everywhere. About 97% of the world’s fresh water is ground water. The quality and amount of ground water that is available varies from place to place. Major reservoirs of ground water are referred to as aquifers. “Aquifers in some of the provinces extended underground far beyond the areas where they are mapped at or near the land surface.” (Ground Water Atlas of the United States) These aquifers occur in two types of geologic formations. Consolidated formations are those composed of solid rock with ground water found in the cracks. Unconsolidated formations are composed of sand and gravel, cobblestones, or loose earth or soil material. The amount of ground water in an unconsolidated formation varies depending on how closely packed the solid materials are and how fine-grained they are. Sand and gravel, and cobblestone formations are generally high-yield aquifers, whereas, finer-grained earth materials may have low yields.

Aquifers and aquifer systems can be grouped into three categories, depending on the degree of consolidation of the rocks and deposits that compose the aquifers. Rocks of Precambrian, Paleozoic, and early Mesozoic ages generally are consolidated; rocks of Cretaceous and Tertiary ages generally are semi consolidated; and deposits of Quaternary age generally are unconsolidated. (Ground Water Atlas of the United States)

Most people are more familiar with surface water than ground water. Surface water bodies such as lakes, streams and oceans can be seen all around, but not ground water bodies. One important difference between ground water and surface water bodies is that ground water moves much slower than surface water. Water in a stream may move several feet per minute, but water in an aquifer may move only several feet per month. This is because ground water must overcome more friction, or resistance, to move through small spaces between rocks and soil underground.

The exchange of water between surface water bodies and aquifers is important. Rivers usually start as small streams and get larger as they flow downstream. The water they gain is often ground water. Such a stream is called a gaining stream. It is also possible for streams to lose water to the ground at some points. In these cases, aquifers are replenished or recharged by water from the losing stream. A stream that flows near the surface of an aquifer will lose water to the aquifer if the water surface in the stream is higher than the water table of the aquifer. A stream will gain water if the water surface of the stream is lower than the water table in the adjacent land. “The water in transit through ground water systems may also be viewed as water in storage.” (Speidel, Ruedisili, 1988)

Ground water is an integral part of the water cycle. The cycle starts with precipitation falling on the surface. Runoff from precipitation goes directly into lakes and streams. “Some of the precipitation return to the atmosphere by evapotranspiration (evaporation plus transpiration by plants), but much of it either flows overland into streams as direct runoff or enters streams as base flow (discharge from one or more aquifers).” (Ground Water Atlas of the United States) The remaining water, called recharge water, drains down through the soil to the saturated zone, where water fills all the spaces between soil particles and rocks. “Upon percolating downward below the water table, soil waters become ground waters.” (Berner, Berner, 1987) The top of the saturated zone is the water table, which is usually the level where water stands in a well, if the local geology is not complicated. Water continues to move within the saturated zone from areas where the water table is higher toward areas where the water table is lower. When ground water comes to a lake, stream or ocean it discharges from the ground and becomes surface water. This water then evaporates into the atmosphere, condenses, and becomes precipitation, thus completing the water cycle.

Ground water is often taken for granted. In many locations pollution is beginning to change the quality of the water. Contaminants which threaten people’s health have been found in several important ground water reservoirs. Some of the contaminants may be so expensive to remove that they make the water virtually unusable for years. “Dissolved solids in ground water primarily result from chemical interaction between the water and the rocks or unconsolidated deposits through which the water moves.” (Ground Water Atlas of the United States)

Ground water becomes polluted when undesirable substances become dissolved in water at the lands surface and are carried down, or leached, to the aquifer with the percolating water. To determine whether a particular substance will pollute a particular aquifer, the properties of

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