#418 Dam

Dams are huge man-made structures that act as ___ on a river. Today, the main reason people build dams is to produce electricity. They are also built to restrict and control the flow of water in a river. Throughout history, dams have been used to prevent flooding and to irrigate (water) farmland. Dams supply about a sixth of the world's electricity and they significantly reduce the risk of floods and ___ . They also make water easier to access, especially in desertlike areas, where water is in low supply. There are however, some negative effects of damming rivers. Many people's homes are knocked down to make space for the dam, and flooding can ___ in the reservoir, which is the area behind the dam where water ___ . This can cause valuable farmland to become submerged under the lakes.