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Earth seems to be unique among the bodies in the solar system. It has life, and it has water. Of the three-quarters of the Earth that are covered by water, 97 percent of that water is salt water. This means that only three percent is fresh water, the kind that most living things depend on for survival. Moreover, of that three percent, two-thirds is frozen in the polar icecaps and glaciers around the world, where it is unavailable to most species. The remaining one percent of Earth's fresh water supports virtually all the organisms on Earth that live on land or in fresh water-in theory at least.

Why only in theory? The truth is that some of Earth's liquid fresh water can no longer support life because it is contaminated with harmful elements that cause illness or death if ingested. So, while one percent of Earth's total water might have been available for living organisms at one time, recent human activity has rendered a portion of that one percent undrinkable. How did this happen?

Earth's water is continually evaporating into the atmosphere, then precipitating back down in the form of rain or snow. As the rain and snow pass over asphalt roads, concrete, farm fields and other human-made objects, it picks up contaminants that wind up in streams, rivers, and eventually in the ground waters, lakes, and oceans of the world. Water quality may also be compromised by natural causes such as volcanic emissions. So, while the quantity of fresh water remains almost constant at one percent, the quality of that one percent is continually being degraded

Breakdown of the Earth's Fresh Water:

Earth's Fresh Water

Nonsurface Water Surface Water -
Ice 77.197 Streams & Rivers 0.004 -
Ground 22.260 Lakes 0.323
Atmosphere 0.036 -
Soil 0.180
Totals = 99.673 + 0.3270 = 100% (of Earth's 1% of Freash Water)

The portion of Earth's freshwater supply that is found in streams, rivers, and lakes is called surface water. (Ground water, and the water in the polar caps, glaciers, soil, and atmosphere, though also fresh, is not considered surface water.) It is from surface-water sources that most U.S. communities draw water for everyday use.

Clean surface water has been a concern of U. S. legislators since the 1950s and1960s, when it was observed that fish were dying in the nation's lakes. The Clean Water Act of 1972 requires that each state conduct water quality surveys to determine the overall health of its surface water supplies. Every two years the states must report their findings to the Environmental Protection Agency (EPA), which in turn prepares a biennial report to Congress. The report is a complete and up-to-date snapshot of water quality conditions throughout the country.

The states, Native American Tribes, and other jurisdictions also define appropriate uses for surface water and consider these uses when outlining water quality standards, which are then presented to the EPA for approval. One reason for these standards is to promote safe living conditions for aquatic life. These conditions, in turn, lead to fish and shellfish that are fit for human consumption and to clean water for drinking, swimming, boating, fishing, and agricultural irrigation.

Once a concern mainly of the states and federal agencies, the scarcity of clean surface water has recently attracted the attention of local communities, and more local agencies have been taking an active part in monitoring this vital commodity. In fact, your own local agency has asked your company to develop a program for monitoring the quality of the surface waters within your community's watersheds. By examining the various methods of monitoring water quality provided by the following case studies, you and your colleagues will prepare a report, with supporting rationales, containing recommendations on where, when, and how to best monitor the surface water quality in your community's watersheds.

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