Hydropower contributes 17% of global electricity, surpassing nuclear, wind, solar, bioenergy, and geothermal combined. Hydropower was one of the first technologies to generate grid-scale electricity beginning in the late 19th century. Many major rivers in the United States and Europe have well-developed hydropower capacity with modest potential for major expansion. But in China, India, and parts of Africa and South America, many new projects are in the proposed and construction phases as governments seek to meet the growing demand for electricity while mitigating greenhouse gas emissions.