Tiêu đề 03. Chapter-2-Water Resources.pdf ✅

(B) India receives nearly 4 % of the global precipitation and ranks 133 in the world in terms of water availability per person per annum. (C) The total renewable water resources of India are estimated at 1, 897 km2 per annum. (D) By 2025, it is predicted that large parts of India will join countries or regions having absolute water scarcity. ➢ Water Scarcity Water scarcity : Shortage of water as compared to its demand is known as water scarcity. Factors responsible for water scarcity. 1. Growing Population : It is one of the basic factors which is responsible for water scarcity. Most of our cities are facing this problem due to over population. A large population means more water not only for domestic use but also to produce more food. 2. Commercialisation of Agriculture : The commercial crops need more water and other inputs. Assured means of irrigation like tubewells and wells are responsible for falling ground water levels. 3. Variation in seasonal and annual precipitation : Precipitation is the main source of water in India but arrival and departure of monsoon in India is uncertain. Even the distribution of rain fall is uneven. 4. Industrialisation and Urbanisation : The ever increasing number of industries has made matters worse by exerting pressure on existing fresh water resources. Industries apart from being heavy user of water also requires power to run them. Most of our cities are over populated. Over population over utilizes the water resources and also pollutes the existing resources. 5. Over utilization : Due to over utilization the water table has lowered. 6. Pollution : Domestic waste and industrial waste are the main factors responsible for pollution of water. Need of the hour to conserve and manage the water resources. 1. To safe guard ourselves from health hazards.
2. To ensure food security. 3. Continuation of our livelihoods and productive activities. 4. Prevent degradation of our natural ecosystem. ➢ Multi-purpose River Projects and Integrated Water-Resource Management ➢  Multi purpose Project : A multipurpose project is that which fulfils a variety of purposes at the same time. Example : irrigation, generation of electricity etc.  Main objectives or Advantages of Multipurpose Project : 1. Generation of Power : They produce neat, pollution free and cheapest energy which is the back bone of industry and agriculture. According to the economic survey 2005-06 these produce more than 30, 000 M.W. power. 2. Flood Control : These projects control the flood because water can be stored in them. These projects have converted many ‘rivers of sorrow’ into river of boon. Example River Kosi. 3. Soil Conservation : These conserve the soil because they slow down the speed of water. 4. Irrigation : They irrigate the fields during the dry seasons. Many canals have been dug and they irrigate dry areas. 5. Afforestation : Trees are systematically planted in and around reservoirs. This helps in preserving “Wild life” and natural ecosystem. 6. Water Navigation : They provide for Inland water navigation through main river or canal. It is the cheapest means of transport for heavy goods. 7. Fisheries : These provide ideal condition for the breeding of fish. Choosen varieties of fish are allowed to grow. 8. Tourist Centres : These projects are well cared and are scientifically developed. So these become the centre of tourist attraction. ➢ Disadvantages of Multipurpose Project 1. High Cost : The initial cost of building the dams is very high. It requires a lot of capital and engineering skills and modern machinery which is not available in India. 2. Adverse Impact on Environment : A vast variety of flora and fauna as well as human settlements get submerged in the water of reservoir formed by the dam. 3. Adverse effect on the fertility of the soil : Due to construction of dams there are no annual floods in the river. And because of this the soil of the down stream region does not get nutrient rich “silt”. This decreases the fertility of the soil.
4. Adverse Impact on aquatic life : Due to construction of dam on the river, the fish in the down stream area do not get sufficient nutrient material. 5. Non-availability of water throughout the year : Most of the rivers in India flow only for few months. So water is not sufficient to build a dam. 6. Disputes between different states : States have disputes over sharing of water, height of the dam and so on. 7. Displacement of local communities : The local people often have to give up their land and livelihood and their meagre access and control over resources for the greater food for the Nation. 8. Change in cropping pattern : They provide assured means of irrigation to farmers. Due to this most of the farmers have changed the cropping pattern shifting to water intensive and commercial crops. This has led to salinisation of soil leading to ecological imbalance. 9. (i) Regulating and damming of rivers affect their natural flow causing poor sediment flow and excessive sedimentation at the bottom of the reservoir, resulting in rockier stream beds and poorer habitats for the rivers aquatic life. (ii) Dams also fragment rivers making it difficult for aquatic fauna to migrate, especially for spawning. The reservoirs that are created on the floodplains also submerge the existing vegetation and soil leading to its decomposition over a period of time. ➢ Rain Water Harvesting ➢  Rainwater Harvesting : It is a technique of increasing the recharge of ground water by capturing and storing rain water by constructing structures such as percolating pits, check dams etc.  Different Techniques to Conserve Water : 1. People of mountaneous regions had built diversion channels like ‘guls’ and ‘kuls’ for agriculture. 2. Rooftop rain water havesting was commonly practiced to store drinking water. eg. Rajasthan. 3. In the flood plain of Bengal, people developed inundation channels to irrigate their fields. 4. In arid and semi-arid regions, agriculatural fields were converted into rain fed storage structure that allowed the water to stand and moisten the soil like the ‘Khadins’ in Jaisalmer and ‘Johads’ in other parts of Rajasthan.  Rain Water Harvesting through Tanks : 1. In the semi arid and arid region of Rajasthan particularly in Phalodi, Bikaner and Barmer most of the houses, have underground tanks for storing water. 2. These tanks were part of well developed roof top rain water harvesting system. 3. Rain falling on the rooftops would travel down the pipe and was stored in tankers. 4. The first spell of rain was usually not collected as this would clean the roofs and the pipes.