Most people living in the United States assume they will have plenty of clean, safe water for drinking, that crops and gardens can be regularly irrigated, and that sewage will be taken care of by their local treatment plant. In many parts of the world, however, the availability of water for personal and public use cannot be taken for granted. In fact, according to the World Health Organization (WH…
Water is a fundamental need in every society. Very few human activities do not require its use. Individuals use water for drinking, cooking, cleaning, and recreation. Industry uses it to make chemicals, manufacture goods, and clean factories and equipment. Cities use water to fight fires, clean streets, and fill public swimming pools and fountains. Farmers give water to their livestock, clean thei…
At any one time, more than 97% of all the water in the hydrologic cycle is contained in the earth's oceans. By comparison, the rivers contain only 0.0001% of the earth's water at any one time and its lakes 0.007%. Nonetheless, this tiny fraction of the total water supply has shaped the course of human development. Throughout human history, societies have depended on these surface wat…
Water lies beneath almost every part of the Earth's surface—mountains, plains, and deserts—but underground water is not always easy to find, and, once found, it may not be readily accessible. Groundwater may lie close to the surface, as in a marsh, or it may occur many hundreds of feet below the surface, as in some dry areas of the nation's West. The amount of groundwater lying within a half mile under the U.S. land surface is approximately four times the amount that …
Most water in the United States is used directly or indirectly from the tap. On average, Americans on community water supplies use about 100 gallons of water per person per day. People with private wells use slightly less. According to the American Water Works Association report Residential End Uses of Water (1999) (the latest data available), about sixty-nine gallons per day are used indoors and the rest is used for activities done outdoors. Of this daily supply, only a small portion is actuall…
A view of the Earth from a satellite shows an azure planet composed almost entirely of water. The oceans that cover two-thirds of the Earth's surface to an average depth of almost 2.5 miles contain 97% of the planet's water and have a profound influence on its environment. If the ocean basins were shallower, the seas would spread across the continents, and the only dry land areas would consist of a few major high mountain ranges projecting above a continuous layer of water.…
Wetlands are transition zones between land and aquatic systems where the water table is usually near or at the surface, or the land is covered by shallow water. Wetlands can take many forms, some of which are immediately recognizable as "wet." Other wetlands appear more like dry land, and are wet during only certain seasons of the year, or at several year intervals. In fact, the U.S. Army Corps of Engineers reports that most wetlands lack surface water and waterlogged soils during …
The United States is a nation relatively rich in water resources. According to the U.S. Geological Survey's Estimated Water Use in the United States in 2000 (the latest data available), in the lower forty-eight states the total renewable supply of water is about 1,400 billion gallons per day. Nevertheless, while the nation as a whole is water-rich, this abundance is not spread evenly throughout the country. Some areas have more water than others, while some have a higher need than others.…
Sulfur dioxide and nitrogen oxides are gases that occur naturally in the Earth's atmosphere. These gases react with water, oxygen, and other chemicals in the atmosphere to form various acidic compounds, including mild sulfuric acid and nitric acid. In nature, the combination of rain and these oxides is part of a natural balance that nourishes plants and aquatic life. However, when human activity increases the amount of acid-forming chemicals in the air, the results can be harmful to human…