Under variety of sizes : Hydropower projects can range from small-scale run-of-river plants to massive dams, allowing for a wide range of power generation capacities to meet varying energy demands. Under multi purpose benefits : This multi-functionality feature enhances their economic and social value. Hydropower systems have relatively high energy conversion efficiencies compared to other renewable technologies. This means that a larger portion of the captured energy is converted into electricity. Under ONE MORE THING : Well Hydro - Electricity is not full of rainbows and sunshine… which brings us to the disadvantages. Under Disadvantages : Perhaps the largest disadvantage of hydroelectric energy is the impact it can have on the environment. Cities, towns, and villages have been eliminated by dams, and local cultures displaced. If people refuse to move due to construction, they have sometimes been forced out of their homes with the threat of violence. Dams also often form reservoirs that flood large areas and displace natural habitats. When dams flood areas, it creates sections of still water that kills vegetation which would emits greenhouse gasses as it rots. Another disadvantage of hydroelectric energy is the expense required to build a dam in the first place. Although they don’t cost much to operate, the time it takes for a dam to pay for itself can vary widely. Some dams took nearly 2 decades and billions of dollars to build. Despite a lack of combustible fuel, dams still offer dangers of their own. Construction accidents, as well as dam failure, can result in injury or loss of life.