Water resource is a source of water which can be used directly or indirectly for any purpose. It can be used for household purpose, agricultural purpose or even industrial purpose. For most household purpose and personal use by humans only fresh water is used.
Distribution of water on earth
Our planet is often called a 'blue planet' because it looks blue from space since 71 percent of earth's surface is covered with water. Water is widely distributed into three categories - fresh water and salt water. Fresh water is only three percent of total water on earth, and salt water is 97% of total water on earth.
Even though fresh water is a renewable source, its supply is decreasing. It is primarily because demand is increasing with increasing world's population and it is eventually going to exceed the supply one day. Two-third of the fresh water is frozen in glaciers and polar ice caps on north pole and south pole. Remaining one-third is found mainly groundwater and very small fraction is above ground or in the air. Sources of fresh water include surface water (river, lake or fresh water wetland), under river flow, ground water (fresh water in pore space in rock or soil), and desalination.
Distribution of fresh water on earth is quite uneven. Asia has 30.6 percent where as South America and North America takes 27.6 percent and 17.9 percent of the total fresh water. Australia has only one percent of it, Europe has 6.7 percent, Africa has 9.2 percent and middle-east has only 0.32 percent. In terms of countries, Brazil has the largest supply of fresh water followed by Russian and Canada.
Salt water is mainly found in Oceans. Low density rocks in the oceans has eroded salts of alkali earth metals resulting in saline water. Out of the total amount of saline water on earth, very little (around 100 Km square globally) is renewable.