Hydropower: supplies 16% world's electricity. dam commonly used to store H2O in reservoir, flows through turbine, spinning it, activating a generator that prod.s electricity. e.g. Three Gorges Dam (China) generates 84B KWh (=burning 40-50M tonnes coal/year). impacts: displaced pop. (1.9M), loss of land (111,000 hectares). has low operating costs, no CO2 emissions