Objectives and Goals:
1. Define Water as a Resource.
2. Water: Some facts and figures.
3. What is Water Scarcity?
4. Water Resource Management and Conservation.
5. Multipurpose river dam projects.
6. Advantages and disadvantages of Multipurpose River dam projects.
7. Narmada Bachao Andolan.
8. Irrigation leads to change in cropping pattern.
9. Rain water harvesting.
10. Bamboo drip irrigation system.
Water - Some Facts and Figures:
1. Out of total volume of water on earth; 96.5% exists in oceans and seas.
2. About 2.5% of total water is available as freshwater.
3. 70% of total freshwater is present as frozen ice in icebergs and glaciers.
4. A little less than 30% of total freshwater is stored as groundwater.
5. India receives about 4% of global precipitation.
6. India ranks 133rd in the world in terms of water availability per person per annum.
7. The total renewable water resources in India are estimated at 1,897 sq km per annum.
8. It is predicted that large parts of India will join regions with absolute water scarcity; by 2025.
Water scarcity is the lack of sufficient available water resources to meet the demands of water usage within a region.
1. Overexploitation of water, excessive use and unequal access to water among different social groups are the main causes of water scarcity.
2. Large population needs ever more water.
3. Large scale farming needs lot of water for irrigation.
4. 4. Rapid Urbanization and Industrialization.
5. Demand has been increasing but the process of natural recharge of groundwater has suffered because of several reasons.
(a) Large scale deforestation has disturbed the natural recharge of groundwater at many places.
(b) Construction of concrete buildings, factories and roads has also made the ground less impervious to rainwater. This has almost totally stopped the percolation of Rainwater to recharge groundwater.
6. Excess use of chemical fertilizers, pesticides and insecticides has contaminated groundwater at many places. The contamination is at such a high level that water has become unfit for human consumption.
7. Sewage and effluents are being discharged into rivers and ponds; without being treated. This has turned most of the rivers into filthy drains.
MULTI-PURPOSE RIVER PROJECTS
Water Resource Management:
• India had a long tradition of building various structures to manage water resources. Irrigation systems were built as early as during the Mauryan Empire.
• At present, many multipurpose dam projects have been built in India.
• These dams serve many purposes. For e.g.:
(a) They prevent flood by checking the flow of water.
(b) The water from the dams is used through a system of canals to irrigate far flung areas.
(c) Dams are also used for electricity generation.
(d) Drinking water is also supplied from the dams.
• But dams have caused a lot of people being displaced from their ancestral lands.
• Additionally, a vast area of land gets submerged in the catchment area of dam.
• This results in large scale environmental consequences.
• Due to these reasons, many groups have begun protesting against building of large dams. "Narmada Bachao Andolan", "Tehri Dam Andolan", etc. are examples of such movements.
• Irrigation has also changed the cropping pattern of many regions with farmers shifting to water intensive and commercial crops. This has great ecological consequences like salinisation of the soil. At the same time, it has transformed the social landscape i.e. increasing the social gap between the richer landowners and the landless poor.
• Most of the rainwater just flows off without seeping down the ground.
• This can be prevented by using rainwater harvesting.
• Rainwater can be collected for future use or can be channelized to recharge groundwater.
• Rooftop rainwater harvesting is ideal to be applied at small scale.
• Many infrastructure projects; like Metro rail and flyovers have also started making provisions for rainwater harvesting.
Some of the methods used for Rainwater Harvesting:
(a) In hill and mountainous regions, people built diversion channels like the 'Guls' or 'Kuls' of the Western Himalayas for agriculture.
(b) In arid and semi-arid regions, agricultural fields were converted into rain fed storage structures that allowed the water to stand and moisten the soil like the 'khadins' in Jaisalmer and 'Johads' in other parts of Rajasthan.
(c) Rooftop rainwater harvesting was commonly practiced to store drinking water, particularly in Rajasthan. Roof top rain water harvesting is the most common practice in Shillong,
(e) In the flood plains of Bengal, people developed barrage channels to irrigate their fields.
(f) Bamboo drip irrigation system is a 200 year old system of tapping stream and spring water by using bamboo pipe. Bamboo drip irrigation system is practiced in Meghalaya.
Rooftop Rainwater Harvesting:
(a) In the semi-arid and arid regions of Rajasthan, particularly in Bikaner, Phalodi and Barmer, almost all the houses traditionally had underground tanks or tankas for storing drinking water.
(b) The tanks could be as large as a big room; one household in Phalodi had a tank that was 6.1 metres deep, 4.27 metres long and 2.44 metres wide.
(c) The tankas were part of the well-developed rooftop rainwater harvesting system and were built inside the main house or the courtyard. They were connected to the sloping roofs of the houses through a pipe. Rain falling on the rooftops would travel down the pipe and was stored in these underground 'tankas'.
(d) The first spell of rain was usually not collected as this would clean the roofs and the pipes.
(e) The rainwater from the subsequent showers was then collected.
(f) The rainwater can be stored in the tankas till the next rainfall making it an extremely reliable source of drinking water when all other sources are dried up, particularly in the summers.
(g) Rainwater, or Palar Pani, as commonly referred to in these parts, is considered the purest form of natural water.
(h) Many houses constructed underground rooms adjoining the 'tanka' to beat the summer heat as it would keep the room cool.
Important facts of Rooftop Rainwater Harvesting:
(a) In western Rajasthan, sadly the practice of rooftop rainwater harvesting is on the decline as plenty of water is available due to the perennial Rajasthan Canal, though some houses still maintain the tankas since they do not like the taste of tap water.
(b) In Gendathur, remote backward villages in Mysore, Karnataka, villagers have installed, in their household's rooftop, rainwater harvesting system to meet their water needs. Nearly 200 households have installed this system and the village has earned the rare distinction of being rich in rainwater. Gendathur receives an annual precipitation of 1,000 mm, and with 80 per cent of collection efficiency and of about 10 fillings, every house can collect and use about 50,000 litres of water annually. From the 20 houses, the net amount of rainwater harvested annually amounts to
(c) Tamil Nadu is the first state in India which has made roof top rainwater harvesting structure compulsory to all the houses across the state. There are legal provisions to punish the defaulters.
(d) Roof top rain water harvesting is the most common practice in Shillong, Meghalaya. It is interesting because Cherapunjee and Mawsynram situated at a distance of 55 km. from Shillong receive the highest rainfall in the world, yet the state capital Shillong faces acute shortage of water. Nearly every household in the city has a roof top rain water harvesting structure. Nearly 15-25 per cent of the total water requirement of the household comes from roof top water harvesting.