Hydroelectric energy is generated by building dams that force moving water to turn machinery like turbines connected to generators, producing electricity. It is one of the oldest and most reliable renewable energy sources, but building large hydroelectric schemes has disadvantages like high costs and impacts on wildlife habitats and river ecosystems. An experiment is described where pouring water into a turbine attached to a bulb demonstrates how kinetic energy from moving water can be transformed into electrical energy powering a light.