A Napoga is a 12yearold girl in Ghana（加纳）， Africa. It is hard for her family to get clean water. Every morning， she leaves home at half past five to get clean water for her family in a village far away. It takes her six hours to get enough clean water for daily（日常） cooking and drinking. She has no time to go to school or to play with her friends. Millions of people in the world are like Napoga. They cant get enough clean water to keep healthy. Earth Day is April 22. But on all other days， we must also remember it. The water we use is the most important natural resource（自然资源） on the earth. Water covers 70% of the earths surface（表面）. But most of that is sea water. We can’t use it for very many things. Fresh water covers only 1% of the earths surface. You probably feel lucky that your life isn’t as hard as Napogas. But that doesn’t mean you dont have to worry about water. We all face serious water problems. One of them is water pollution. All kinds of things from cars， factories， farms and homes make our rivers， lakes， and oceans dirty. Polluted water is very bad for people to drink. And dirty water is bad for fish， too. Now， 34% of all kinds of fish are dying out. How do cars and factories make our water dirty？ First， they pollute the air. Then， when it rains， the rain water comes down and makes our drinking water dirty. Dirty rain， called acid rain（酸雨）， is also bad for plants， animals and buildings. Scientists say that in 30 years， more than half of the people in the world wont have enough clean water. We have to learn how to save more water for ourselves and our children. Here is some advice for saving water： ●Turn off the water while you brush your teeth. You can save as much as 450 liters（升） each month. ●Leaky taps（漏水的龙头） waste a lot of water. Fix them right away！ ●You can easily cut your 10minute showers（沐浴） in half—and you’ll be just as clean. ●When you wash dishes， dont let the water run. ●Only wash clothes when you have a lot to wash. If your washing machine isnt full， youre wasting water！ Acid rain ________.