Water-an Endless Cycle

26 Water-an Endless Cycle Water is essential to life on earth. Next to air, it's our most important substance. It is, in fact, the source of life. Trees need water. So do birds, insects, fish, grasses, flowers and honeybees. All living things-from the tiniest insects to the tallest trees-need water to survive. Nearly 70 percent of the human body is water. We use it for many internal processes including control of body temperature, food digestion, nutrient transportation, and waste removal. In fact, we can survive only a few days without this life-giving substance. Fortunately for us, there is nearly the same amount of water on earth today as there was more than 100 million years ago. Believe it or not, the water we drink today is actually the very same water that people drank in the past. How can that be? Water is simply recycled in a process known as the water cycle. Water is continuously moving and changing form as it goes through the steps of this cycle: evaporation, condensation, precipitation, and collection.

In a nutshell, here is how the water cycle works. First, water is collected on the earth. Heat causes the water to turn into vapour in a process called evaporation. Water vapour then rises and condenses. Then it rains or snows, which is called precipitation. Water falls back to earth where it is collected, and the cycle starts over again. In the natural environment, here is how the water cycle functions. The sun warms up the water in lakes, rivers, and oceans, turning it into vapour. This vapour begins to rise. As the vapour rises, it cools and collects dust. Finally, it forms clouds. Precipitation happens when the air gets filled with too much condensed water. The clouds get heavy and are unable to hold the water. That's when it rains or snows. As the precipitation reaches earth, it is collected in lakes, rivers and in the ground. Soon, the water cycle begins again, ensuring our survival. It is really a remarkable process-just one of many that keep the delicate balance here on earth.