This specialty also includes civil engineers who are primarily concerned with maintaining water quality. These engineers work to purify drinking water supplies and to treat wastewaters so that they can be released back into streams or other bodies or water, or recycled for industrial use. The activities of this group of engineers will be described later.
Many people unfamiliar with industrial water usage would be surprised to learn that water is as important a fuel to industry as are fossil fuels. Indeed, in the huge thermoelectric power plants located along the nation's largest rivers, it is water that actually produces electricity through its conversion to steam by either fossil or nuclear fuels. To light a 100-watt bulb for ten hours requires about 4,000 gallons of water. Besides thermoelectric and hydroelectric power plants, the major industrial users of water are the paper, petroleum, chemicals, and primary metals industries. Largely through the efforts of mechanical and civil engineers, these industries have cut back water usage by about 20 percent since 1950, while U.S. industrial output has quadrupled over the same time frame.
Likewise, domestic water use has declined slightly from a peak of about 120 billion gallons per day in the mid-1980s. Irrigation, which accounts for about 40 percent of daily U.S. water usage, has transformed parts of the West, particularly California, into the nation's most productive farmland. Only about 5 percent of U.S. farmlands are irrigated but they produce about 20 percent of the nation's farm products.
Water resources engineers are typically skilled in the sciences of hydraulics or hydrology. Hydraulics is the study of the movement of water in response to applied forces and of the forces and pressures created by both moving and stationary bodies of water. Hydrology, on the other hand, is the study of the occurrence of water in the atmosphere- the fall of water to earth as precipitation, the flow of water across the surface of the earth, and the infiltration of water through the earth to underground storage areas.
Civil engineers involved with hydrology work to determine how much of the available water supply can be used safely for particular purposes without permanently depleting the water supply. Although about 4 trillion gallons of water fall daily in the United States as various forms of precipitation, all but a fraction of this water disappears quickly as runoff or through evaporation. As a result, many of the nation's underground aquifers are being depleted faster than they can be discharged, and aquifers as well as rivers, lakes, streams, and harbors are being polluted by contaminated runoff water.
In controlling the flow of water across the land surface and in storing surface water and groundwater in various locations, water resources engineers often rely on dams, floodwalls, pumping stations, aqueducts, and canals. Dams are constructed to store water for irrigation, for municipal water, and for the generation of electric power. In most cases, dams, pumping plants, and associated pipelines or aqueducts are designed to satisfy many separate purposes. This allows for the most efficient overall use of the water. To bring water to areas where rainfall is deficient, the engineers who design dams work with irrigation and drainage specialists in designing and constructing canals, aqueducts, or pipelines to transport the water.
Although the availability of water, particularly in the thirsty farmlands and cities of the West, is a major engineering concern, those who endured the massive floods of recent years have a different perspective on water. Water resources engineers also design and construct floodwalls and levees to hold back maximum flows in rivers to prevent flooding. Another flood control tool is the reservoir, designed to retain rapid runoff and flood-enhanced stream flows, so that these quantities of water can be released gradually to prevent flooding downstream.
A good example of this are the huge lakes created by engineers working with the Tennessee Valley Authority, a regional water agency created by President Franklin Roosevelt during the Great Depression to help develop one of the nation's most impoverished areas. The TVA's 47 dams along the Tennessee River and its tributaries supply electrical power, help stem flooding, and enhance navigation. As a classic example of how water projects can serve multiple purposes, Lake Cumberland, Dale Hollow Lake, Kentucky Lake, and the other TVA reservoirs also have stimulated commerce, industry, and tourism in the mid-South.
Water resources engineers are also involved in the planning, design, and construction of facilities to provide navigation on waterways throughout the United States, and of harbor facilities along the coastlines. These activities include the design and construction of dams, locks, artificial channels, canals, piers, and docks; the dredging of navigation channels; and the protection of shorelines from erosion by wind and wave action.
The focus of civil engineers working with industrial, commercial, domestic, and agricultural water users is no longer simply supplying adequate quantities of water or dredging services for barge traffic. Hand in hand with supplying and controlling water are the issues of water conservation, habitat preservation, pollution control, water recycling, and water-saving technology.
Indeed, after four decades of feverish dam building (from the 1930s to the early 1960s), we may never again see a U.S. dam project as monumental in scale as the Hoover Dam or the Glen Canyon Dam along the Colorado River. For instance, the U.S. Bureau of Reclamation, the agency whose imposing dams have changed the face of the West, now focuses most of its efforts on the design of improved spillways, dam maintenance, safety improvements, artificial reefs, and manufactured wetlands. Nonetheless, managing water for multiple uses, through the use of dams as well as through the restoration of wetlands, will continue to provide civil engineers with one of the profession's most complex but also most exciting challenges. About one in five civil engineers working in the United States is engaged in water resources engineering.
