water is very important to the human beings.but now many rivers and lakes are polluted. 

　　and what shall we do ???

　　we can do like these things:

　　first we must protect the factory form pouring waste water into the river

　　second we should stop people from throwing litter into the river.many kinds of litter may pollute the envirenment.

　　finally we can tell the visitors how important the water is.

　　after doing these things,i think water will become clearer sooner or later.