Why is there a water crisis even though 3 4 th of the Earth's surface is covered by water?

Of the total water available on earth, 97 % is found in oceans, 2 % as ice on the peaks and the poles and the remaining 1 % is in rivers, lakes, ponds and beneath the earth's surface. We use this underground water by digging wells. Water is also present in the atmosphere in the form of water vapour, mist and clouds. Though oceans are the biggest source of water on earth, many substances like common salt and other minerals are present in ocean water in large quantities. Due to these, the water becomes salty or saline. Therefore, water available in the oceans cannot be used for daily activities like drinking, bathing, washing clothes or irrigation. Water present in icebergs is pure though it cannot be used easily. Of the total water available on earth, the quantity of water which can be used by human beings is very small. This is equivalent to 1 ml of usable water out of every 10 litre available, that is 0 . 01 % . Hence, the quantity of water available for our use is really very small and that is why the water crisis is there even though 3 4 th of the Earth's surface is covered by water. So, we should use water carefully and prevent its wastage.