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Water is a unique and remarkable compound, essential to all forms of life. Human beings and the flora and fauna cannot survive without water on this planet. A large amount of life on this planet is aquatic based i.e., can only survive in water. It is the most abundant substance after air in the earth's biosphere.
Let us quickly review distribution of water resources. Oceans, seas and other saline inland water bodies, make 97.3% of the total global supply of water which is not available for human consumption due to high salt content. Fresh water accounts for only 2.7% of the total estimated global water supply! Of this percentage, 75% of the fresh water is frozen in polar ice caps and the glaciers, like those in the Himalayas. Some fresh water is blocked in inaccessible areas under the ground. The fraction of fresh water available for humans is estimated at less than 0.003% of the total global water availability! Even though water is a renewable source, its evident conservation of water and non-pollution of freshwater sources is a must, given its vital importance both biologically and chemically and continuing global population explosion.
Of the fresh water available there are three main sources. The first one is rainwater (or precipitation). India receives an overall rainfall of about 105 to 117 cm annually resulting in 3 million m3 of water. Most of this water collects in the few months during monsoon. This is a huge quantity and is the largest in the world. The second source is surface water; there are 14 major river systems such as Ganga, Brahmaputra, Godavari, Krishna and Cauvery. Nearly all major Indian rivers have dams on them for redirecting water for irrigation, and for hydroelectric power generation. Other surface water surface water sources include ponds, lakes and streams.
The third is ground water or underground aquifers which is the water that percolates down the surface soil into pore spaces of rocks. The total volume of ground water found in the aquifer is estimated to be 42.3 x 1010 m3. Ground water provides soil moisture for plants and supplements for streams and lakes. It is a reserve supply of water that the agricultural sector and urban water supply sectors are tapping increasingly. The water table indicates the level at which ground water is found, and rises and falls according to the level water that percolates down to this level during the rains and the amount that is pulled out from it. In spite of vast irrigation networks and dams, groundwater is being over-exploited; most of the increase in irrigation capacity in India, in the last two decades has come from groundwater (84%). Regeneration of aquifers is far slower than today's consumption trends and one can say that the water table of most Indian cities and many agricultural areas is on the decline.
What is the scenario with the water situation in India? In India most of water supply and regeneration is dependant on the monsoon rains. There are some worrying facts about the water situation. The effects of world climate change are being all over including the Indian subcontinent. The increased temperature levels are resulting in changing weather patterns. For a country like India whose agricultural activities (and water infrastructure related projects) is still dependant on regular monsoon rainfall in different rain zones, it is a cause of worry for adequate and reliable water supply. Erratic rainfalls like heavy rains in areas receiving minimal rainfall (Rajasthan floods of 2006 in Barmer and surrounding districts), scanty rains in areas receiving good rain fall e.g. Karnataka and A.P drought of 2006, melting of glaciers are causing problems in surface water supply ground water recharge and agriculture.
The use of mega dam projects necessary for agricultural irrigation also has its disadvantages as compared to many traditional decentralized localized irrigation networks used efficiently, but now largely abandoned. The amount of water impounded behind dams since 1960 has quadrupled world wide. Major diversion of water from the rivers course has resulted in many down steam areas having reduced ground water recharge. This includes urban areas which have huge requirements of water and depend on dams and reservoir supply. Cities have an additional problem; they need to clear vegetation from land to build roads, parking lots, commercial malls and residential flats etc. The large concreting of surface areas does not allow water to seep into the ground to be stored in aquifers leading to water shortages. Because of this, there are water run off or water remaining on the surface increases the likelihood surface run-off and urban flooding that damages buildings.
Activity
Study the rainfall patterns in India from an atlas and identify where water is abundant and the regions of water scarcity.
| One of China's major rivers, the Yellow River, has run dry for part of the year since 1985. And in 1997 it failed to reach the sea for 226 days! The main reason is that on its way to the sea, the river's waters are diverted into fields for agriculture and into the growing cities for consumption, sanitation and industry
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It is evident that human intervention can change the availability of water in various regions; it can also lead to pollution of water sources.
Dams have been answer to huge and consistent supply of water and electric power needed for modern agriculture and urban cities. Large dams ensure the storage of adequate water, particularly during lean seasons and they also make available water supply to arid and semi-arid areas where rainfall is scanty. Canal systems leading from these dams can transfer large amounts of water to great distances and bring greenery to considerable areas. Considerable semi-arid and arid zones of Rajasthan and Gujrat have benefited from this canal.
However, mega dam projects have both pros and cons. They have met with considerable resistance by people in some cases in India. The Narmada dam has been met with continuous resistance since its inception by the local people organized into the 'Narmada Bachao Andolan' (Save the Narmada Movement) by social workers. Similarly, the Tehri Dam on the river Ganga in Uttranchal
faces similar opposition. Such large dams have been criticized primarily because
of the following aspects
Social Aspect
The dams submerge forever the traditional living areas and cause loss of traditional sources of livelihood. A large number of villagers and tribals who have been displaced by various development projects are largely poor. They do not get any benefits from these projects and are alienated from their lands and forests without adequate compensation or proper rehabilitation. The oustees of the Tawa Dam built in the 1970s are still fighting for the benefits they were promised.
Economic Cost
Huge amounts of public money are spent on Dams. Critics feel that the net benefits to the people and society are not proportionate and lopsided favouring urban industrial and government priorities, generation of power and irrigation at the expense of local people in the dam belt area.
Environmental Cost
Dams contribute enormously to deforestation and the loss of biological diversity. They can also result in potentially huge accidents during disasters like earthquakes.
The embracing of centralized mega water management and regulation has also led to two more criticisms. The politicization and mismanagement of water supply baised towards selected few, due to lack of equitable distribution of water people close to the source of dam irrigation grow water intensive crops like sugarcane and rice while people farther downstream do not get any water. Secondly, loss of local control on water resources and loss of local decentralized methods of irrigation which were judicious and much closer to the ground in terms of identifying water needs and tailoring optimal solutions.
In fact, an alternate system of decentralised tanks and canals has been used in various parts of India since ancient times. These were generally local interventions managed by local people who assured that the basic minimum requirements for both agriculture and household needs were met throughout the year. The use of this stored water was strictly regulated and the optimum cropping patterns based on the water availability were arrived at on the basis of decades/centuries of experience. The maintenance of these irrigation systems was also a local affair. These mega-projects led to the neglect of the local irrigation methods, and the government also increasingly took over the administration of these systems that were left.
Almost 90% of the rainwater in India is running off every monsoon and only 10% of the rainwater is utilized (collected and stored). Rainwater harvesting is the process of collection and storage of rainwater with the purpose of consuming it or using it to recharge ground water. If more of this water is collected and stored, it could alleviate the growing water shortage and stall the impending water crisis, already being faced in many areas and cities in India.
Rain Water Harvesting
Rainwater harvesting can be surface runoff harvesting that collects the rainwater runoff from paved and unpaved surfaces in village or town and is directed into open tanks or wells; low yield bore wells and percolation pits to recharge subsurface aquifers. Measures to keep that water clean by not allowing polluting activities to take place in the catchments should also be ensured. It can also be Rooftop Harvesting where rainwater is collected from rooftops, filtered, stored in tanks and then used for all appropriate purposes usually domestic.
The aim of Rainwater harvesting is to:
- Regenerate the primary resources of land and water sources
- Help produce secondary resources for plants and animals to avoid any ecological imbalance
Most water harvesting techniques are highly specific to an area and the benefits are also localized. In many degraded areas in the plains water harvesting has semi-circular shaped earthen embankments or low, straight concrete and rubble "check dams" built across seasonally flooded gullies. Monsoon rains fill ponds behind dwelling structures. Some of these large earthen embankments or low "check dams" can store water from up six months till a full year until the monsoons arrives again.
In the past rain water harvesting has been used extensively in India's dry areas of India to store water. These include early water harvesting forms that have structures and water conveyance. For example the village ponds or tanks adjoining natural catchment areas in Rajasthan called Khadins, and nadis; check dams or diversion weirs built across rivers known as bandharas and virdas in Maharashtra and Gujarat, bundhis in Madhya Pradesh and bundala Uttar Pradesh, the traditional flood water harvesting system called ahars and pynes in Bihar, kulhs or surface channels diverting water from fast growing streams in Himachal Pradesh, ponds in the Kandi belt of Jammu region, and eris (tanks) in Tamil Nadu, surangams in Kerala, and kattas in Karnataka. Many are still in use today and their main purpose of such water harvesting has been to recharge the ground water beneath. Ground water spreads out to recharge wells, does not evaporate, and provides moisture for vegetation over a wide area. Ground-water is also relatively protected from contamination by human and animal waste.
In conclusion the management of water resources of a country does require government interventions like the national river commission under which the Ganga action plan I and II and major irrigation projects are managed. But one also needs to involve and utilize the local people and resources for water regeneration and harvesting.
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