All about Water on Earth


Ever noticed the globe, why do we see more blue and less green on a map or globe? That is because 71% of earth’s surface is covered by water. Water is one of the basic necessities of life and one of the four basic elements as discovered by the ancient Greeks. Looking at this perspective, if 71% of earth’s surface is covered with water then we have ample supply of water forever. But that’s not the case, out of the total water present on earth 96.54% of it is present in form of oceans. Water present in oceans is highly corrosive and is of no use. Out of the remaining water on earth approximately 1.7% present as glaciers and about the same amount is in form of ground water. This sums up to 3.4% which is the total percentage of fresh water present on earth. Fresh water is the water humans can use for consumption for example drinking, irrigation and cleaning.

The Water Cycle. Image by: NASA Precipitation Education (CC)

The Water Cycle

The earth has limited amount of fresh water and it keeps on moving in a cycle which is termed as the water cycle. Water cycle has 4 major phases, it starts from the evaporation of water present on earth, then these evaporated vapors condensed back to liquid and forms the clouds. When the clouds get heavy and cannot hold more water, precipitation occurs and the stored water vapors in form of clouds, fall back on earth in the form of rain, hail or snow. The fallen water on the ground is then collected in the oceans, lakes, rivers or it soaks through the earth’s surface to reach the aquifers where it gets stored to be used in future.



A significant majority of earth’s fresh water is found under the ground in aquifers. An aquifer is basically a layer of water containing sand and pebbles, found below the surface of the earth. Water in an aquifer is there since forever, or it has reached there after getting soaked from the surface or from other channels. Water from aquifers can be extracted by a water well, which is basically a hole inside the earth’s surface through which water from the aquifer can be sucked using a water pump.  Aquifers beneath the earth’s surface may occur at various depths, a common thumb rule about the quality of water in aquifers is, the deeper you’ll go, the extracted water will be of better quality, cleaner and free of contaminants. This is because there are chances of impurities and contaminants in the water present in shallow aquifers.

Aquifer. Image by: Hans Hillewaert (CC), Source Wikipedia


Recharge of Aquifer

From the discussion done yet, it seems like water can only be “extracted” out of an aquifer, but that’s not the case, aquifers have their natural process of recharge which enables them to keep their water levels intact, even when a significant amount of water is being extracted out for utilization. Groundwater recharge is a hydrogeological process and it involves mainly the seeping in of rainfall water from the earth’s surface to the aquifer. To ensure the maintenance of a healthy aquifer, it is necessary to make sure that the extraction and recharge are equal. We need to keep this balance, so that the aquifer can be utilized for continuous supply of fresh water without any risk of scarcity.



Water Scarcity

In cases where extraction exceeds the recharge, aquifers starts to deplete and a point arrives where they are no longer able to provide water. Depletion of aquifers is the major source of water scarcity on the planet. This is one of the most dangerous problems for humanity. One of the United Nations Millennium Development Goals aimed to “halve the proportion of people who are unable to reach or to afford safe drinking water” by 2015. The millennium development goals have since been replaced by Sustainable Development Goals and this issue still remains in the charter as a part of Goal 6 (Clean Water and Sanitation). Unfortunately, we have already started to feel geo-political effects of water shortage, many regional conflicts (for example between India and Pakistan) have their roots in water scarcity.

Earth has been blessed with a limited amount of useful water, it now depends on the careful utilization of the available resources so that we can save it for the generations to come after us, because water is life!