Hydro Power

Fresh Water Fresh water is naturally occurring water on the Earth's surface in bogs, ponds, lakes, rivers and streams, and underground as groundwater in aquifiers and underground streams. Freshwater is generally characterized by having low concentrations of dissolved salts and other total dissolved solids. The term specifically excludes seawater and brackish water although it does include mineral rich waters such as chalybeate springs.

History Early uses of waterpower date back to Mesopotamia and ancient Egypt, where irrigation has been used since the 6th millennium BC and water clocks had been used since the early 2nd millennium BC. Other early examples of water power include the Qanat system in ancient Persia and the Turpan water system in ancient China.

Waterwheels and Mills Hydropower has been used for hundreds of years. In India, water wheels and watermills were built; in Imperial Rome, water powered mills produced flour from grain, and were also used for sawing timber and stone; in China, watermills were widely used since the Han Dynasty. The power of a wave of water released from a tank was used for extraction of metal ores in a method known as hushing. The method was first used at the Dolaucothl gold mine in Wales from 75 AD onwards, but had been developed in Spain at such mines as Las Medulas. Hushing was also widely used in Britain in the Medieval and later periods to extract lead and tin ores. It later evolved into hydraulic mining when used during the California gold rush. In China and the rest of the Far East, hydraulically operated "pot wheel" pumps raised water into irrigation canals. At the beginning of the Industrial revolution in Britain, water was the main source of power for new inventions such as Richard Arkwright's water frame. Although the use of water power gave way to steam power in many of the larger mills and factories, it was still used during the 18th and 19th centuries for many smaller operations, such as driving the bellows in small blast furnaces and gristmills, such as those built at Saint Anthony Falls, utilizing the 50- foot drop in the Mississippi River. In the 1830s, at the peak of the canal-building era, hydropower was used to transport barge traffic up and down steep hills using inclined plane railroads.

Hydraulic power pipes Hydraulic power networks also existed, using pipes carrying pressurized liquid to transmit mechanical power from a power source, such as a pump, to end users. These were extensive in Victorian cities in the United Kingdom. A hydraulic power network was also in use in Geneva, Switzerland. The world famous Jet d'Eau was originally the only over pressure valve of this network.

Benefits of Hydropower Hydropower is cheap, non-polluting, and many small facilities (less than 30 MW) are considered renewable energy sources. Unlike other sources of energy like nuclear power, the costs of large scale plants is declining because the facilities have been paid for by federal or state projects. Dams and reservoirs also provide recreational opportunities, flood control, irrigation, refuges for wildlife, water supply, and transportation.

Concerns of Hydropower While there are many benefits to hydropower, the facilities can severely change their local environment. Reservoirs cover large areas of land, flooding places usually dedicated to agriculture or forest preserves; obviously this seriously alters the surrounding ecosystem. Large dams also change watersheds: the quality of water, fish populations and migration patterns, silt deposits, river flow, and vegetation are often altered. In many instances of Large-scale construction of hydropower facilities, such as the Three-Georges in China, are also controversial because numerous people are displaced from their homelands. In places such as California, non-profit organizations and local citizens are developing certification programs that seek to minimize the impact of these plants. Hydropower evaluations use the following criteria to assess the impact: (1) water quality, (2) fish passage and protection, (3) river flow, (4) watershed protection, (5) cultural resource protection, (6) threatened and endangered species protection, (7) recreation, and (8) whether any natural resource committees have recommended removal of the facility ( HYPERLINK " ). If the facility meets all eight criteria, it will be certified as a low- impact, green-power plant.

The Future of Hydropower To date, the United States has developed only 20 percent of its hydropower potential. Although hydropower is non-polluting, construction of new facilities is highly controversial because of environmental and social impacts. The best location for plants is often in mountainous or rainy areas where ecosystems are fragile and often protected. Yet, new hydropower projects do not necessarily require construction since only 2,400 of 80,000 dams are used for this type of energy generation. New technology along with upgrades in current plants can increase efficiency and create energy sources without disrupting more lands.