Hydropower is a clean, domestic and renewable energy source, which converts kinetic energy from falling water into electricity, without consuming more water than is produced by nature. It depends upon the movement of water from areas of higher elevation to areas of lower elevation.

        Among the advantages of hydropower energy we can mention the low operating costs, because the fuel, water, comes free to charge. This contributes to provide inexpensive electricity, because no fossil fuels are required to produce the electricity, and the earth's hydrologic cycle naturally replenishes the "fuel" supply. Hydropower is also one of the most efficient ways to generate electricity; modern turbines can convert as much as 90% of the available energy into electricity. Hydropower energy produces no greenhouse gases or other air pollution. Besides, it leaves behind no waste. And, unlike other energy sources such as fossil fuels, water is not destroyed during the production of electricity – it can be reused for other purposes.

        Hydropower energy is very abundant; anywhere rain falls, there will be rivers. If a particular section of river has the right terrain to form a reservoir, it may be suitable for dam construction. Moreover, since water is a naturally recurring domestic product and is not subject to the whims of foreign suppliers, there is no worry of unstable prices, transportation issues, production strikes, or other national security issues.

        Hydropower is very reliable and convenient because it can respond quickly to fluctuations in demand. A dam's gates can be opened or closed on command, depending on daily use or gradual economic growth in the community. The production of hydroelectricity is often slowed in the nighttime when people use less energy. When a facility is functioning, no water is wasted or released in an altered state; it simply returns unharmed to continue the hydrologic cycle.

        One feature of hydropower, which is often overlooked, is that the reservoir of water resulting from dam construction, which is essentially stored energy, can support fisheries and preserves, and provide various forms of water-based recreation for locals and tourists. Land owned by the hydroelectric company is often open to the public for hiking, hunting, and skiing. Therefore, hydropower reservoirs contribute to local economies.

        All these benefits of hydropower energy have made it the leading source of renewable energy. Worldwide, about 20% of all electricity is generated by hydropower. The advantages of hydropower are therefore convincing, but there are some serious drawbacks that are causing people to reconsider its overall benefit. Hydropower plants can significantly impact the surrounding area and provoke opposition for numerous social, environmental, economic and safety reasons. The main reason for opposition worldwide is the huge number of people that have been evicted from their lands and homes to make way for reservoirs. It is estimated that the construction of hydropower plants have displaced about 30 to 60 million people, usually poor people who are further impoverished economically and suffer cultural decline, high rates of sickness and death, and great psychological stress.

        The livelihoods of people downstream of dams can also be severely affected, through the destruction of fisheries, the contamination of water supplies and the loss of seasonal floods, which bring fertile silt and water to agricultural land. Dam reservoirs can also become breeding grounds for waterborne diseases such as malaria, leishmaniasis and schistosomiasis. Now, can we consider hydropower to be a "clean" source of energy? I believe the answer is no as the destruction of forest cover as well as the emissions from reservoirs (particularly in the tropics) resulting from the slow decomposition of inundated vegetation, make a significant contribution to global warming.