In the United States, about half of fresh water consumption is due to electrical power production, mainly to cool power plants. Agriculture uses a third of water consumed in the United States but, globally, accounts for nearly 70 percent of water usage. Public water use in the United States represents only 11 percent of the total, with industrial use at 5 percent. While it is important for individuals to conserve water, most potential water savings can be found through more efficient agricultural and power production processes.
The United States is by far the biggest water consumer on the planet, with the average person using about 175 gallons per day for drinking, sanitation, cooking and bathing. This amount skyrockets to more than 4,000 gallons per day when agricultural and power production requirements are added. It is interesting to note that water usage is highest in the most arid regions of the country. As a consequence, aquifers and reservoirs are shrinking in most areas of the United States. Worldwide, one in five people face water scarcity. In places where water is scarce, resources are almost always overexploited.
Much of the overexploitation of water resources occurs because so much of it is wasted. About 95 percent of the water for domestic use goes down the drain. Sixty percent of water intended for crop irrigation never reaches the crops. According to Cornell University professor David Pimentel, a pound of wheat bread requires 250 gallons of water, using agricultural practices, as of the time of publication. The greatest potential for conserving water globally lies with improving irrigation technologies and implementing more efficient systems as widely as possible.
Water pollution contaminates fresh water supplies, rendering them unfit for human consumption. Pollution also destroys ecosystems that must be maintained to keep fresh water resources viable. In the United States, 40 percent of western rivers are contaminated by mine waste. Pollution from industrial facilities includes mercury, asbestos, lead, cyanide, sulphur, and petrochemicals. Agricultural pollution contains high levels of nitrogen and phosphorus, which can lead to toxic algae blooms. Virtually all rivers near agricultural areas, especially larger drainages, suffer from large amounts of agricultural runoff.