Chapter 5. Water Resources

Water Sources

* Water is essential for domestic use, cultivation and also for industries.
*  Around 97% of the total water available on the earth lies in the seas and oceans.
* Only 2.5% exits as fresh water.
* Nearly 70% of the fresh water is locked in ice and glaciers.
* Just under 30% of its exits as groundwater
* Only 0.3% exits in rivers, lakes and ponds.
* A tiny fraction occurs on a form fit for human and industrial consumption.
* India receives around 4% of the total rainfall in the world.
* India is ranked 133rd in the world in terms of water availability per person per year.
* Water scarcity is posing an alarming threat in most parts of the world, including India.

Water Scarcity


* The unavailability of sufficient clean water to meet personal, domestic and
industrial requirements in an area is called water scarcity.
Factors that lead to water scarcity are:
   *  Increasing demand
   *  Unequal access
   *  Over exploitation
   *  Contamination.

* An increase in population increases the demand for fresh water.

* More land brought under cultivation increase the demand for water resources.
* Rapid industrialization exerts greater demand on water resources.
* Unequal access to water resources leads to water scarcity
* Overuse of tube – wells by modern housing societies to provide water to their residents is also over-exploitation of underground water resources.
* The use of chemical fertilizers and pesticides in modern agriculture leads to pollution of fresh surface water and groundwater.

We need to conserve water to:

   * Keep ourselves healthy
   *  Promote economic growth
   *  Ensure food security.

Multi – Purpose River Projects


* A dam is a structure that forms a barrier across a river to regulate the flow of
water.
* Modern dams are also used to generate electricity and supply water to industries and households.
* Dams are also used to control flooding by regulating the flow of water.
* The reservoirs created behind several dams are used for fish breeding.
* Dams are called multipurpose river projects due to the many ways that they offer to manage our water resources.
* A dam creates an enormous reservoir of water that submerges vast stretches of the surrounding area.
* Major benefits of large multi-purpose projects go to big landowners, while the local, poor, landless people have little to gain.
* Dams block upstream migration of fish for breeding, putting several species in danger
* The sudden release of large quantities of water from a dam results in large-scale flooding in plains areas.
* Most of the multi-purpose river projects in India so far have not met their desired objectives.

Rain Water Harvesting

* The process of collecting rain water during the wet season, to meet our fresh
water requirements e in the dry season, is called rainwater harvesting.
* In the semi-arid region of Rajasthan, earthen check dams, called johads , are used to collect rain water that percolates into the ground raises the level of ground water.

In rooftop rain water harvesting system:

   *  Gutters and PVC pipes to collect rain water falling on the roof.
   *  The water is filtered through sand and bricks, and stored in tanks for immediate use.
   *  Excess water is diverted o wells to recharge groundwater.

In bamboo drip irrigation:

   *  Bamboos are split to make shallow channels.
   *  These channels are used to divert water from rain-fed springs to farms.
   *  Channels sections in the farm allow the water to drip near the roots of the plants.

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