Water is often used to produce electricity. In colonial times, water mills were constructed along rivers. The water current would spin a wheel, thus generating energy. Eventually, dams were constructed to generate power on a larger scale. Dams constrict the flow of rivers, resulting in the creation of artificial reservoirs. The energy of the water passing through the dam is harnessed and converted to electricity. For a time, the Hoover Dam was the largest dam in the world, until it was surpassed by the Grand Coulee Dam. The Three Gorges Dam in China is currently the largest dam in the world. The Three Gorges Dam is capable of generating 22,500 MW.
However, there are various ethical and environmental concerns associated with dam construction. The construction of dams prevents water from flowing downstream, potentially depriving communities of a water source. Geopolitical relations could be harmed if dams are constructed in rivers that cross international borders. Furthermore, dams create large reservoirs, drastically altering the ecosystem of the surrounding area. Nearby lands previously used by animals and humans often become completely submerged. Dams also hinder the flow of sediment and fish, which further affects communities downstream. The Three Gorges Dam is infamous for the negative impact its had on nearby residents. Over 1,200,000 people were displaced by the construction of the dam. Thirteen cities, 140 towns, and 1350 villages were destroyed by the reservoir created by the dam. Erosion caused by the reservoir has caused numerous landslides and earthquakes in the area. Some Chinese scholars believe that the construction of the dam directly caused the extinction of the Chinese River Dolphin. Tidal power stations generate power using the ocean tides. Tidal power is commonly more expensive than other available options, and there are few locations where tidal power would be viable. Thus, tidal power is used infrequently. Power can also be generated by constructing wind turbines offshore. Wind energy is a clean, renewable energy source that has minimal effect on the environment. Wind energy uses airflow to turn blades that mechanically power a generator. Wind turbines generate more power as wind speed increases. Thus, it is sometimes efficient to construct wind turbines several miles offshore, where wind speed is greatest. Opponents of offshore wind energy believe that the economic cost is too high, and that the turbines are an eyesore. There are also concerns that wind turbines are dangerous to avian life. It is estimated that 200,000 to 375,000 birds are killed by wind turbines every year. However, far more birds are killed by radio towers (6.8 million annually), and by cats (1.4 billion to 3.7 billion annually). Proponents of wind energy argue that wind turbines are ultimately beneficial to birds beach they do not emit greenhouse gasses, and thus do not negatively impact the environment as much as alternative means of power generation. |