Water
Nearly three-fourths of Earth’s surface is covered with water. Perhaps the most important liquid in the world, water is usually easy to get from rain, springs, wells, streams, rivers, ponds, and lakes. It fills the vast ocean beds. As vapor, water is also present in the air, where it often condenses into clouds. The bodies of most living things contain a large proportion of water. For example, water makes up about 60 percent of the weight of the human body.
Conservation
Unlike many of the world’s natural resources, water is a replenishable resource (see rainfall). However, it is vitally important that humans conserve water and help to maintain the quality of water by discontinuing practices that contaminate and pollute the supply faster than it can replenish itself.
