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 enormous reservoirs 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.