# Revision Notes Geography Chapter 3 Water Resources Class 10

## Important Terms to Remember

• Hydrological cycle : This is the journey that water takes as it circulates from the land to the sky and back again. It is also known as the ‘water cycle’.
• Fresh water : Naturally occurring water on earth's surface in ice sheets, glaciers, lakes, rivers and underground as groundwater, which is suitable for drinking within some form of purification.
• Ground water : The water which exists below the ground surface in the zone of saturation and can be extracted through well or any other means or emerges as springs and base flows in streams and rivers.
• Hydraulic structure : All dams, lakes, canals, wells and ponds, etc. in which rainwater is collected.
• Hydroelectricity : It is the power which is generated with the help of running water.
• Dam : A dam is a barrier across flowing water that obstructs, directs or retards the flow, often creating a reservoir, lake or impoundment.
• Multipurpose project : A multi-purpose project or river valley project serves a number of purposes simultaneously such as irrigation, flood control, generating hydroelectricity and tourism, e.g., the Bhakra Nangal Dam.
• Rain water harvesting : Rainwater harvesting is gathering, accumulating and storing rainwater for different uses.
• Aquifer : A layer of rock or soil which can absorb and hold water.
• Water scarcity : Shortage of water as compared to its demand is known as water scarcity.
• Guls or Kuls : In hilly and mountainous regions, people build diversion channels like the ‘Guls’ or ‘Kuls’ of Western Himalayas for agriculture.
• Inundation canal : It is meant to direct flood waters during the rainy season.
• Drip irrigation : It is a type of irrigation in which water gets dropped in the form of drips close to roots of the plants in order to conserve the moisture.
• Surface runoff : This is the water flow that occurs when the soil is infiltrated to full capacity and excess water from rain, melted snow or other sources flows over the land.

##### Water Resources

Summary

• The main source of water on earth is the hydrological cycle.
• \left(\frac{3}{4}\right)^{th} of the Earth’s surface is covered with water, but fresh water accounts for a small proportion. Fresh water is mainly obtained from surface run off and ground water which is continually renewed and recharged through the hydrological cycle.
• 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 :
1. Greater demand for water by large and growing population and unequal access to it.
2. Water resources are being over-exploited to expand agriculture and consequently ground water levels are falling.
3. Post independent India has witnessed intense industrialisation and urbanisation, exerting increasing pressure on fresh water resources.
4. 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 overexploited.
• 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 :
1. Sringaverapura near Allahabad had a sophisticated water harvesting system, which channelised the flood water of the Ganga River. It dates back to 1st century B.C.
2. There are many extensively built dams, lakes and irrigation systems. The most important Lake is Sudarshan lake at Junagarh in Gujarat.
3. Bhopal Lake is one of the largest artificial lakes built in the 11th century A.D.
4. In the 14th century, the tank in Hauz Khas, Delhi was constructed by Iltutmish for supplying water to the Siri Fort area.
• Uses of dams :
1. Irrigation
2. Hydro Electricity generation
3. Water supply for domestic and industrial uses
4. Flood control
5. Recreation
7. Fish breeding
• Dams are referred to as multipurpose projects.
• Jawaharlal Nehru proudly proclaimed dams as the temples of modern India because of their potential to integrate development of agriculture and the village economy with rapid industrialisation and growth of the urban economy.
• 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 :
1. Poor sediment flow
2. Excessive sedimentation at the bottom of the reservoir
3. Poorer habitats for the rivers’ aquatic life
4. Difficult for aquatic fauna to migrate
5. Submerge the existing vegetation and soil leading to its decomposition over a period of time.
• Rain water harvesting system was a viable alternative of multipurpose projects both socio-economically and environmentally.
• In hill and mountainous regions, people built diversion channels like the ‘guls’ or ‘kuls’ of the Western Himalayas for agriculture.
• In arid and semi-arid regions of Rajasthan, almost all houses traditionally had underground tanks for storing drinking water.
• Rain water is also referred to as palarpani and it is considered as the purest form of natural water.
• Today, in western Rajasthan, the practice of rooftop rainwater harvesting is on the decline as plenty of water is available due to the perennial Rajasthan Canal.
• In Gendathur, a remote and backward village in Mysore, Karnataka, villagers have installed in their household’s rooftop, rainwater harvesting system to meet their water needs.
• Roof-top rain water harvesting is the most common practice in Shillong in Meghalaya.
• In Meghalaya, a 200-year-old system of tapping stream and spring water by using bamboo pipes is prevalent.
• Tamil Nadu is the first and the only state in India which has made roof-top rain water harvesting structures compulsory. There are legal provisions to punish the defaulters.
• Roof-top rain water harvesting was commonly practised in Rajasthan to store drinking water. Roof-top rain water harvesting is done through the following ways :
1. Roof top rain water is collected using a PVC pipe.
2. Filtered using sand and bricks.
3. Underground pipe takes water to sump for immediate usage.
4. Excess water from the sump is taken to the well.
5. Water from the well recharges the underground tanka.
6. Later take water from the well.
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