Water

Looking at water, you might think that it's the most simple thing around. Pure water is colorless, odorless, and tasteless. But it's not at all simple and plain and it is vital for all life on Earth. Where there is water there is life, and where water is scarce, life has to struggle.

Water Use
Water truly is a resource that gets used and used for everything. The same water can be utilized many times.

From the mountains, the river flows through a reservoir and past urban, rural, and industrial settings. Water is available from surface sources, such as rivers, ponds, and lakes, and from ground-water sources called aquifers.

Recreation, hydroelectric power generation, nature's needs, and transportation are instream uses, which means that the water remains in the river. Consequently, very little water is consumed. The water can be reused farther downstream. Mining, public supply, commercial, domestic, wastewater-treatment, agriculture, thermoelectric power generation, and industrial are offstream uses, which means that the water is withdrawn from a source such as the river or ground. But only a part of the water withdrawn is actually consumed, so the remaining part is returned to the river or ground and can be used again. Different offstream uses consume different proportions of the water they withdraw.

Water Quality
What is water quality? To some people, water quality may suggest only "clean" water for drinking, swimming, and fishing. But to the farmer or manufacturer, water quality may have an entirely different meaning. One of the most important issues concerning the quality of water is how that water will be used. Water that is perfectly fine for irrigation might not be suitable for drinking or swimming.

The quality of water can change as it flows over the land surface as rivers, streams, lakes, or ponds (surface water), or under the land surface (ground-water). Because surface and ground waters are interconnected in some areas, changes in the quality of surface water can affect the quality of the area's ground-water, and vice versa. These changes in water quality may be due to natural factors or human activities.

As rock minerals come in contact with water, some dissolve and become part of the surface- or ground-water system. Other natural materials, such as soil or organic matter, become suspended in the water and move from one place to another. The effects of human activities on water may result from land disturbances, which increase the amount of rock minerals, soils, or organic matter available to be transported by and dissolved in water, or from the addition of human-made pollutants. When water is degraded to a point that affects its use for a particular purpose, it has become polluted.

Water pollution originates from two very different sources: point sources and nonpoint sources. Human activities are associated with point sources (wastewater-treatment plant, storm drain, and factory) and nonpoint sources (suburban lawn, parking lot, construction site, landfill, logging area, septic tank, and agricultural field).

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