How do we get Fresh Water
- The three-fourth of the earth’s surface is covered with water.
- But only a small proportion of it accounts for freshwater that can be put to use.
- This freshwater is mainly obtained from surface run off.
- Ground water is continually being renewed and recharged through the hydrological cycle.
- All water moves within the hydrological cycle ensuring that water is a renewable resource
Water scarcity : It is caused by over-exploitation, excessive use of and unequal access to water among different social groups.
An area having ample water resources can have to face water scarcity due to the following reasons :
- Greater demand for water by large and growing population and unequal access to it.
- Water resources are being over-exploited to expand agriculture and consequently ground water levels are falling.
- Post independent India has witnessed intense industrialization and urbanization, exerting increasing pressure on fresh water resources.
- Multiplying urban centers with large and dense populations have further aggravated the problem of water scarcity.
- In housing societies or colonies, most of the houses have their own ground water pumping devices to meet the water needs. Thus, water resources are being over exploited
Multi-purpose river projects and integrated water resource management :
- The history reveals use of many sophisticated hydraulic structures from ancient times, such as dams of stone, reservoirs or lakes, embankments and canals for irrigation.
- Some ancient hydraulic structures are listed below :
- Sringaverapura near Allahabad had a sophisticated water harvesting system, which channelized the flood water of the Ganga River. It dates back to 1st century B.C.
- There are many extensively built dams, lakes and irrigation systems. The most important Lake is Sudarshan lake at Junagarh in Gujarat.
- Bhopal Lake is one of the largest artificial lakes built in the 11th century A.D.
- In the 14th century, the tank in Hauz Khas, Delhi was constructed by Iltutmish for supplying water to the Siri Fort area
What is a dam ? What is its Classification?
- A dam is a barrier across flowing water that obstructs, directs the flow, often creating a reservoir, lake or impoundment.
- Dams are classified according to structure, intended purpose or height.
- Based on structure and the materials used, dams are classified as timber dams, embankment dams.
- According to the height, dams can be categorised as large dams and major dams or alternatively as low dams, medium height dams and high dams.
Jawaharlal Nehru proudly proclaimed dams as the temples of modern India
The reason being that it would integrate development of agriculture and the village
economy with rapid industrialisation and growth of the urban economy.
Uses of dams :
- Hydro Electricity generation
- Water supply for domestic and industrial uses
- Flood control
- Inland navigation
- Fish breeding
Important Multipurpose Projects
- Damodar Valley Corporation – built on river Damodar – beneficiary states are Jharkhand and West Bengal
- Bhakra Nangal– built on river Sutlej-beneficiary states are Punjab, Haryana and Rajasthan, Himachal Pradesh
- Hirakud – built on river Mahanadi – beneficiary state is Odisha.
- Kosi – built on river Kosi – beneficiary state is Bihar and our neighbouring country Nepal.
- Chambal Valley – built on river Chambal – beneficiary states are Madhya Pradesh and Rajasthan
Reasons for opposing multi-purpose projects
- Blocking of channels due to their construction and blockage of natural flow.
- River bottom become silty.
- Reduction in the food of riverine life.
- Degradation of forests and soils due to submergence during floods
- Rain water harvesting system was a viable alternative of multipurpose projects both socio-economically and environmentally.
- In hilly and mountainous regions, people built diversion channels like ‘gul’ or ‘kul’ in western
Himalaya for agriculture.
- Roof-top rain water harvesting was commonly practiced to store drinking water particularly in Rajasthan.
- In West Bengal, people develop inundation channels to irrigate their fields.
- In semi arid regions it was converted into rain fed storage structures called khadins and jahads that allowed the water to stand and moist the soil.
In Rajasthan to store drinking water. Roof-top rain water harvesting is done through the following ways :
- Roof top rain water is collected using a PVC pipe.
- Filtered using sand and bricks.
- Underground pipe takes water to sump for immediate usage.
- Excess water from the sump is taken to the well.
- Water from the well recharges the underground tanks.
- Later take water from the well.
Previous Year Asked Questions From This Topic
- Why is roof top water harvesting important in Rajasthan? Explain.
Answer. Roof top water harvesting is important in Rajasthan because :
- It was commonly practised to store drinking water.
- The rainwater can be stored in the tanks till the next rainfall, making it an extremely reliable source of drinking water when all other sources are dried up, particularly in the summers.
- Rain water, or palar pani, as commonly referred to in these parts, is considered the purest form of natural water.
- Many houses construct underground rooms adjoining the ‘ tanka’ to beat the summer heat as it would keep the room cool
- Some houses still maintain the tanks since they do not like the taste of tap water.
2. Describe any four traditional methods of rain water harvesting adopted in different parts of India.
3. In recent years, multipurpose projects and dams have come under great scrutiny and opposition. Explain why
- In recent years, multipurpose projects and large darns have come under great scrutiny and oppposition for a variety of reasons.
- Regulating and damming of rivers affect their natural flow.
- River’s diversion and barricading due to building of dams affect migration and spawning of aquatic life
- The reservoirs lead to decomposition of soil and land degradation.
- The dams have triggered floods due to sedimentation in the reservoir and release of excess water during heavy rains.
- Large scale displacement of local communities, local people who give up their land for the projects hardly receive any benefit.
- Interstate water disputes with regard to sharing the costs and benefits of multi-purpose projects are leading to tension between states, e.g., Kaveri Godavari dispute, Sabarrnati water dispute.
- Sometimes, multipurpose projects induced earthquakes, caused water borne-diseases and
pests, and led to pollution resulting from excessive use of water.