Topic-1 : Water Scarcity and the need for Water Conservation; Multipurpose River Projects: Integrated Water Resource Management
- 3/4th of the Earth’s surface is covered with water, but freshwater accounts for a small proportion.
- Freshwater is mainly obtained from surface run off and ground water which is continually renewed and recharged through the hydrological cycle.
- 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’.
- Freshwater : Water not from the sea and is not salty or brackish.
- Ground water : The water which exists below the ground surface in the zone of saturation can be extracted through well or any other means or emerges as springs and base flows in streams and rivers.
- India receives nealy 4 per cent of the global precipitation and ranks 133 in the world in terms of water availability per person per annum.
- The total renewable water resources of India are estimated at 1,897 sq km per annum.
- By 2025, it is predicted that large parts of India will join countries or regions having absolute water scarcity.
- Water scarcity : Shortage of water as compared to its demand is known as water scarcity.
- Due to variations in seasonal and annual precipitation the availability of water varies over place and time.
- Water scarcity is mainly caused due to the excessive use and unequal acces to water for different social groups.
- An area having ample water resources can face water scarcity due to the following reasons:
i) Greater demand for water by large and growing population and unequal access to it.
ii) Water resources are being over-exploited to expand agriculture and consequently ground water levels are falling.
iii) Post-independent India has witnessed intense industrialisation and urbanisation, exerting increasing pressure on freshwater resources.
iv) Multiplying urban centres 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 groundwater 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.
- 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.
- Some ancient hydraulic structures are listed below:
i) 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.
ii) There are many extensively built dams, lakes and irrigation systems. The most important lake is Sudarshan lake.
iii) Bhopal lake is one of the greatest artificial lakes built in the 11th century A.D.
iv) In the 14th century the tank in Hauz Khas, Delhi was constructed by Iltutmish for supplying water to the Siri Fort area.
- Dam : A dam is a barrier across flowing water that obstructs, directs or retards the flow, often creating a lake or impoundment.
- Based on structure and materials used, dams are classified as timber dams, embankment dams or masonry dams, with several subtypes.
- According to the height, dams can be categorized as large dams and major dams or alternatively as low dams, medium height dams and high dams.
- 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 Bhaskra Nangal Dam.
- Uses of dams:
ii) Electricity generation
iii) Water supply for domestic and industrial uses
iv) Flood control
vi) Inland navigation
- Thus, dams are now referred to as multipurpose projects.
- Jawaharlal Nehru produly proclaimed dams as the temples of modern India because of their poetntial to integrate development of agriculture and the village economy with rapid industrialisation and growth of the urban economy.
- Reasons for opposing multi-purpose projects:
i) Poor sediment flow.
ii) Excessive sedimentation at the bottom of the reservoir
iii) Poorer habitats for the rivers’ aquatic life
- Multi-purpose projects and large dams have also been the cause of many new environmental movements like the ‘Narmada Bachao Andolan’ and the ‘Tehri Dam Andolan’
- Resistance to these projects has primarily been due to the large-scale displacement of local communities.
- Irrigation facilities has changed the cropping pattern of many regions with farmers shifting to water intensive and commercial crops. This has greawt ecological consequnces like salinisation of the soil.
- It has transformed the social landscape i.e. increasing the social gap between the richer landowners and the landless poor.
- Inter-state water disputes are also becoming common with regard to sharing the costs and benefits of the multi-purpose project.
- The dams that were constructed to control floods have triggered floods due to sedimentation in the reservoir.
- It was also observed that the multi-purpose projects induced earthquakes, caused waterborne diseases and pests and pollution resulting from excessive use of water.
- Narmada Bachao Andolan or save Narmada Movement is a Non Governmental Organisation (NGO) that mobilised tribal people, farmers, environmentalists and human righsts activists against the Sardar Sarovar Dam being built across the Narmada river in Gujarat. It originally focused on the environmental issues related to trees that would be submerged under the dam water.
- Sardar Sarovar Dam has been built over the Narmada River in Gujarat. This is one of the largest water resource projects of India covering four states – Maharashtra, Madhya Pradesh, Gujarat and Rajasthan.
Topic-2 : Rainwater Harvesting
- Rainwater 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.
- Guls or Kuls : In hill and mountainous regions, people build diversion channels like the ‘Gul’ or ‘Kuls’ of Wester Himalayas for agriculture.
- Innundation canal : It is meant to direct flood water 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 that occurs when the soil is infiltrated to full capacity and excess water from rain, melted snow or other sources flows over the land.
- Rainwater harvesting system was a viable alternative of multipurpose projects both socio-economically and environmentally.
- In hill and mountainous regoins, people built diversion channels like the ‘guls’ or ‘kuls’ of the Western Himalayas for agriculture.
- Following steps are followed for Roof-top rainwater harvesting:
i) Roof top rain water is collected using a PVC pipe.
ii) Filtered using sand and bricks.
iii) Underground pipe takes water to sump for immediate usage.
iv) Excess water from the sump is taken to the well.
v) Water from the well recharges the underground aquifer.
vi) Later take water from the well.
Roof-top rainwater harvesting was commonly practised in Rajasthan to store drinking water.
- In aird and semi-arid regions of Rajasthan , almost all houses traditionally had underground tanks for storing drinking water.
- Rainwater is also referred to as, palarpani, and it is considered as the purest form of natural water.
- Today, in western Rajasthan, the practice fo rooftop rainwater harvesting is on the decline as plenty of water is availabel 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 rainwater harvesting is the most common practice in Shillong in Meghalaya.
- In Meghalaya , a 100-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 had made roof-top rain water harvesting structures compulsory. There are legal provisions to punish the defaulters.
Bamboo Drip Irrigation System
- Bamboo pipes are used to divert perennial springs on the hilltops to the lower reaches by gravity.
- The channel sections, made of bamboo, divert water to the plant site where it is distributed into branches, again made and laid out with different forms of bamboo pipes.
- The flow of water into the pipes is controlled by manipulating the pipe positions.
- If the pipes pass a road, they are taken high above the land.
- Reduced channel sections and diversion units are used at the last stage of water application. The last channel section enables water to be dropped near the roots of the plant.