Water Resources
Introduction
Water is one of the most essential natural resources. It covers about 71% of the earth's surface, but only 2.5% is freshwater — and only a fraction of that is accessible for human use. India has about 4% of the world's freshwater resources but 17% of the world's population. This makes water conservation and management critical national priorities.
Section 1: Sources of Water
Surface Water
| Source | Description | Importance |
|---|---|---|
| Rivers | Perennial (Himalayan) and seasonal (Peninsular) | Irrigation, drinking, transport |
| Lakes | Natural and man-made | Water storage, recreation |
| Ponds | Small water bodies | Local water supply, groundwater recharge |
| Reservoirs | Man-made lakes behind dams | Irrigation, drinking, hydropower |
Groundwater
| Aspect | Description |
|---|---|
| Source | Rainwater that percolates into the ground |
| Aquifer | Layer of rock or sediment that holds groundwater |
| Water table | Upper level of groundwater |
| Wells and tube wells | Methods to access groundwater |
India's groundwater usage:
- ~60% of irrigated agriculture depends on groundwater
- Over 85% of rural drinking water comes from groundwater
- Groundwater levels are falling rapidly in many regions due to over-extraction
Section 2: The Water Cycle
The water cycle (hydrological cycle) describes the continuous movement of water on, above, and below the earth's surface.
| Process | Description |
|---|---|
| Evaporation | Sun's heat turns water into vapour from oceans, rivers, lakes |
| Transpiration | Plants release water vapour through their leaves |
| Condensation | Water vapour cools and forms clouds |
| Precipitation | Water falls as rain, snow, hail, or sleet |
| Runoff | Water flows over land into rivers, lakes, and oceans |
| Percolation | Water seeps into the ground to become groundwater |
Section 3: Water Scarcity
Causes of Water Scarcity
| Cause | Explanation |
|---|---|
| Population growth | More people need more water for drinking, agriculture, and industry |
| Increasing demand | Agriculture (70% of water use), industry (20%), domestic (10%) |
| Over-exploitation | Groundwater is pumped faster than it can be replenished |
| Pollution | Industrial waste, sewage, and agricultural runoff contaminate water sources |
| Climate change | Changing rainfall patterns, more frequent droughts |
| Inefficient use | Wasteful irrigation methods, leakage in water supply systems |
| Deforestation | Reduces water retention capacity of soil |
Regions Facing Water Scarcity
- Rajasthan and Gujarat — low rainfall, arid climate
- Maharashtra (especially Marathwada) — frequent droughts
- Peninsular India — seasonal rivers, dependence on groundwater
- Urban areas — growing demand exceeding supply
Section 4: Conservation of Water
Rainwater Harvesting
Rainwater harvesting is the collection and storage of rainwater for future use.
| Method | Description | Suitability |
|---|---|---|
| Rooftop harvesting | Collecting rain from rooftops into storage tanks | Urban and rural buildings |
| Check dams | Small barriers across streams to slow water flow | Hilly and semi-arid areas |
| Percolation pits | Pits dug to allow water to seep into the ground | Areas with low groundwater |
| Johad | Traditional earthen check dams (Rajasthan) | Arid regions |
| Kunds | Traditional rainwater storage structures | Desert areas |
Watershed Management
Watershed management involves the integrated management of land, water, and vegetation in a watershed (an area that drains into a common point).
Key practices:
- Contour bunding and trenching
- Afforestation on slopes
- Check dams and percolation tanks
- Sustainable agricultural practices
- Community participation
Successful examples in India:
- Sukhomajri (Haryana): Community-managed watershed restored the village's water supply
- Ralegan Siddhi (Maharashtra): Anna Hazare's watershed work transformed a drought-prone village
- Hiware Bazar (Maharashtra): Watershed development led to agricultural prosperity
Other Conservation Methods
| Method | Description |
|---|---|
| Drip irrigation | Water delivered directly to plant roots — reduces wastage |
| Sprinkler irrigation | Efficient water distribution — suitable for uneven land |
| Reuse of water | Treating and reusing wastewater for non-potable uses |
| Awareness campaigns | Educating people about water conservation |
| Water pricing | Appropriate pricing discourages wastage |
Section 5: Multipurpose River Projects
What Are Multipurpose Projects?
Multipurpose river projects are large dams built across rivers to serve multiple purposes simultaneously:
| Purpose | Benefit |
|---|---|
| Irrigation | Provides water for agriculture |
| Hydroelectricity | Generates electricity |
| Flood control | Regulates river flow to prevent floods |
| Drinking water | Supplies water to cities and towns |
| Inland navigation | Creates waterways for transport |
| Recreation | Develops tourism and water sports |
Major Multipurpose Projects in India
| Project | River | State | Key Purpose |
|---|---|---|---|
| Bhakra Nangal | Sutlej | Punjab, Himachal, Haryana | Irrigation + hydropower |
| Damodar Valley Corporation (DVC) | Damodar | West Bengal, Jharkhand | Flood control + power |
| Hirakud Dam | Mahanadi | Odisha | Flood control + irrigation |
| Tungabhadra Dam | Tungabhadra | Karnataka, Andhra | Irrigation + power |
| Sardar Sarovar | Narmada | Gujarat | Irrigation + drinking water |
| Tehri Dam | Bhagirathi | Uttarakhand | Power + irrigation |
| Nagarjuna Sagar | Krishna | Andhra, Telangana | Irrigation + power |
Advantages and Disadvantages of Dams
| Advantages | Disadvantages |
|---|---|
| Reliable water supply for irrigation | Displacement of people (tribals, villagers) |
| Clean electricity (hydropower) | Submergence of forests and agricultural land |
| Flood control | Siltation reduces dam life |
| Drinking water supply | Alters river ecosystem and aquatic life |
| Recreation and tourism | Upstream floods increase in some areas |
| Employment generation | Expensive construction and maintenance |
Comparison: Traditional vs Modern Water Conservation
| Aspect | Traditional Methods | Modern Methods |
|---|---|---|
| Examples | Johad, kunds, stepwells, tanks | Dams, drip irrigation, desalination |
| Scale | Small, localised | Large, capital-intensive |
| Technology | Simple, locally available | Advanced engineering |
| Maintenance | Community-managed | Government or corporate managed |
| Cost | Low | Very high |
ICSE Exam Focus
| Question Type | Marks | Key Areas |
|---|---|---|
| Sources of water | 4 | Surface and groundwater |
| Water scarcity | 4 | Causes and affected regions |
| Rainwater harvesting | 4 | Methods with examples |
| Watershed management | 3 | Meaning, practices, success stories |
| Multipurpose projects | 4 | Examples, purposes, advantages, disadvantages |
Common Mistakes in ICSE Exams
| Mistake | Correction |
|---|---|
| Confusing 'water cycle' with 'water scarcity' | The cycle is natural; scarcity is a human/environmental problem |
| Ignoring groundwater depletion | Groundwater is being over-extracted in many parts of India |
| Thinking dams are only beneficial | Know the negative impacts — displacement, submergence |
| Forgetting traditional methods | Johad, kunds are important examples |
| Missing the role of community | Community participation is key to watershed management |
Self-Test Questions
Q1: What are the main sources of water in India? A1: India's water sources include surface water (rivers, lakes, ponds, reservoirs) and groundwater (accessed through wells and tube wells). About 60% of irrigated agriculture depends on groundwater.
Q2: What are the causes of water scarcity in India? A2: Water scarcity is caused by population growth, increasing demand (agriculture 70%, industry 20%), over-exploitation of groundwater, pollution, climate change, inefficient use, and deforestation.
Q3: What is rainwater harvesting and how is it done? A3: Rainwater harvesting is collecting and storing rainwater. Methods include rooftop harvesting (collecting rain from roofs into tanks), check dams (barriers across streams), percolation pits (allowing water to seep into ground), and traditional structures like johad and kunds.
Q4: What is watershed management? Give examples of successful projects. A4: Watershed management is the integrated management of land, water, and vegetation in a drainage basin. Successful examples include Sukhomajri (Haryana), Ralegan Siddhi (Maharashtra), and Hiware Bazar (Maharashtra), where community-managed watershed work transformed water availability.
Q5: Explain the advantages and disadvantages of multipurpose river projects. A5: Advantages include irrigation, hydropower, flood control, and drinking water supply. Disadvantages include displacement of people, submergence of forests and farmland, siltation, and alteration of river ecosystems.
Key Facts to Remember
| Fact | Detail |
|---|---|
| Earth's water cover | 71% |
| Freshwater share | 2.5% |
| India's global population share | 17% |
| India's global water share | 4% |
| Groundwater for irrigation | ~60% |
| Agriculture's water share | ~70% |
| First major multipurpose project | Bhakra Nangal (Sutlej) |
Final Summary
Water is a finite and precious resource facing increasing pressure from population growth, economic development, and climate change. India, with 4% of the world's water but 17% of its population, must manage its water resources carefully. Rainwater harvesting, watershed management, efficient irrigation, and responsible multipurpose projects are all essential strategies. For ICSE students, understanding water resources is not just about geography — it is about the most pressing environmental challenge of our time: ensuring that every person has access to clean, sufficient water.
