GEF

Unit 3  |  Water Use and Human Water Systems 72 infrastructure is an important step toward understanding and developing sustainability. Dams are a highly visible component of our water system, some of which are many stories tall and capture millions of gallons of water in vast reservoirs. Dams provide many benefits and it would be a mistake to label all of these structures as unsustainable. Constructing dams allows people to plant crops or build settlements in areas that would otherwise be covered by seawater, such as the city of Amsterdam in the Netherlands. In other cases, dams allow people to exert some control over unpredictable water flow in rivers. Water impounded by dams can be routed to irrigate farmland or supply drinking water to cities. The deeper water created by dams allows for easier river navigation, aiding the development of trade and settlement. Dams and reservoirs also create important recreation areas, such as Lake Mead in the U.S. states of Arizona and Nevada. Lake Mead is created by the Hoover Dam on the Colorado River. DAM A barrier constructed to hold back water and raise its level, the resulting reservoir being used in the generation of elec- tricity or as a water supply.