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Water Resources Book PDF Free Download
Chapter 3: Water Resources
You already know that three-fourth of the earth’s surface is covered with water, but only a small proportion of it accounts for freshwater that can be put to use. This freshwater is mainly obtained from surface run off and ground water that is continually being renewed and recharged through the hydrological cycle.
All water moves within the hydrological cycle ensuring that water is a renewable resource. You might wonder that if three-fourth of the world is covered with water and water is a renewable resource, then how is it that countries and regions around the globe suffer from water scarcity? Why is it predicted that by 2025, nearly two billion people will live in absolute water scarcity? Water: Some facts and figures •
96.5 per cent of the total volume of world’s water is estimated to exist as oceans and only 2.5 per cent as freshwater. Nearly 70 per cent of this freshwater occurs as ice sheets and glaciers in Antarctica, Greenland and the mountainous regions of the world, while a little less than 30 per cent is stored as groundwater in the world’s aquifers.
• India receives nearly 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. Where is then water scarcity likely to occur? As you have read in the hydrological cycle, freshwater can be obtained directly from precipitation, surface run off and groundwater.
Is it possible that an area or region may have ample water resources but is still facing water scarcity? Many of our cities are such examples. Thus, water scarcity may be an outcome of large and growing population and consequent greater demands for water, and unequal access to it. A large population means more water not only for domestic use but also to produce more food. Hence, to facilitate higher food-grain production, water resources are being over-exploited to expand irrigated areas and dry-season agriculture.
You may have seen in many television advertisements that most farmers have their own wells and tube-wells in their farms for irrigation to increase their produce. But have you ever wondered what this could result in? That it may lead to falling groundwater levels, adversely affecting water availability and food security of the people. Post-independent India witnessed intensive industrialisation and urbanisation, creating vast opportunities for us.
Today, large industrial houses are as commonplace as the industrial units of many MNCs (Multinational Corporations). The everincreasing number of industries has made matters worse by exerting pressure on existing freshwater resources. Industries, apart from being heavy users of water, also require power to run them. Much of this energy comes from hydroelectric power. Today, in India hydroeclectric power contributes approximately 22 per cent of the total electricity produced.
Moreover, multiplying urban centres with large and dense populations and urban lifestyles have not only added to water and energy requirements but have further aggravated the problem. If you look into the housing societies or colonies in the cities, you would find that most of these have their own groundwater pumping devices to meet their water needs.
Not surprisingly, we find that fragile water resources are being over – exploited and have caused their depletion in several of these cities. So far we have focused on the quantitative aspects of water scarcity. Now, let us consider another situation where water is sufficiently available to meet the needs of the people, but, the area still suffers from water scarcity. This scarcity may be due to bad quality of water.
Lately, there has been a growing concern that even if there is ample water to meet the needs of the people, much of it may be polluted by domestic and industrial wastes, chemicals, pesticides and fertilisers used in agriculture, thus, making it hazardous for human use.
| Author | NCERT |
| Language | English |
| No. of Pages | 11 |
| PDF Size | 1.3 MB |
| Category | Social Science |
| Source/Credits | ncert.nic.in |
NCERT Solutions Class 11 Social Science Chapter 3 Water Resources
1. Answer the following questions in about 30 words.
(i) Explain how water becomes a renewable resource.
Answer:
Water can be considered as a renewable resource since there will be rains and surface water and groundwater will get recharged continuously due to the 3 process involved in the hydrological cycle.
The 3 processes of the hydrological cycle are
- Evaporations
- Condensation
- Precipitation
(ii) What is water scarcity and what are its main causes?
Answer:
Many of our cities are such examples. Thus, water scarcity may be an outcome of large and growing population and consequent greater demands for water, and unequal access to it. A large population requires more water not only for domestic use but also to produce more food. Hence, to facilitate higher food-grain production, water resources are being over-exploited to expand irrigated areas for dry-season agriculture. Irrigated agriculture is the largest consumer of water. Most farmers have their own wells and tube-wells in their farms for irrigation to increase their productivity. This has adversely affected water availability and food security of the people.
(iii) Compare the advantages and disadvantages of multi-purpose river projects.
Answer:
Advantages:
- Irrigation
- Electricity generation
- Flood control
- Water supply for industrial and domestic purposes.
- Tourist attraction
- Inland navigation
Disadvantages:
- The natural flow of water is affected
- Aquatic life gets affected
- Submergence of land in the surrounding areas
- Ecological consequences
- Large scale displacement of local people.
NCERT Class 11 Social Science Textbook Chapter 3 With Answer PDF Free Download