Water Resources Chapter - 3
1. Importance of Water
- Water is vital for survival, agriculture, industry, domestic use, and ecological balance.
- About 71% of Earth’s surface is covered with water, but only 2.5% is freshwater.
- India receives most of its rainfall from the monsoon, making water conservation crucial.
2. Water Scarcity & Its Causes
- Water scarcity refers to a situation where the availability of water is insufficient to meet demand. Causes include:
- Overuse and misuse of water (excessive irrigation, industrial usage)
- Unequal distribution of rainfall
- Deforestation and urbanization (reducing groundwater recharge)
- Water pollution (chemical wastes, sewage disposal)
- Climate change and droughts
- Large population growth increasing demand for water
Need for Water Conservation and Management
Water is one of the most precious natural resources, essential for life, agriculture, industries, and ecosystems. However, due to increasing demand and misuse, water scarcity has become a major issue. Therefore, water conservation and management are necessary for the following reasons:
1. To Address Water Scarcity
- Unequal distribution of water across regions causes shortages.
- Overuse and wastage lead to depletion of available water sources.
- Many regions in India, like Rajasthan, suffer from chronic water shortages.
2. Increasing Demand Due to Population Growth
- The growing population puts pressure on water resources.
- More water is needed for drinking, sanitation, agriculture, and industries.
- If not managed properly, future generations may face severe water crises.
3. Climate Change and Droughts
- Irregular rainfall patterns due to global warming affect water availability.
- Prolonged droughts in some areas worsen water shortages.
- Sudden floods wash away freshwater, making it unavailable for use.
4. Overuse in Agriculture and Industry
- Agriculture consumes about 70% of freshwater through irrigation.
- Inefficient irrigation methods (like flood irrigation) waste a lot of water.
- Industries discharge untreated wastewater, polluting rivers and lakes.
5. Depletion of Groundwater
- Excessive extraction of groundwater leads to lowering of water tables.
- Many wells and tube wells have dried up due to overuse.
- Groundwater takes a long time to replenish, so conservation is crucial.
6. Pollution of Water Bodies
- Industrial waste, sewage, and plastic pollution contaminate rivers, lakes, and oceans.
- Waterborne diseases like cholera and dysentery spread due to contaminated water.
- Cleaning polluted water is costly and difficult.
7. Protecting Biodiversity and Ecosystems
- Water is essential for wetlands, forests, and wildlife.
- Many aquatic species are endangered due to water pollution and depletion.
- Sustainable water management ensures ecological balance.
8. Energy Production
- Hydroelectric power generation depends on adequate water levels.
- Water scarcity can lead to power shortages in hydro-dependent regions.
9. Economic Growth and Development
- Industries like textiles, food processing, and manufacturing require water.
- A lack of water can slow down economic activities.
- Efficient water management supports sustainable development.
10. Traditional Knowledge & Cultural Importance
- Ancient methods like rainwater harvesting, stepwells, and tanks help in water conservation.
- Respecting water resources aligns with cultural and religious traditions in India.
Uses and Importance of Dams
Dams are massive structures built across rivers to store, regulate, and control water flow. They play a crucial role in water conservation, irrigation, power generation, and flood control. Below are the key uses and importance of dams:
1. Irrigation
- Dams store water and provide a steady supply for agriculture.
- They help in canal irrigation, ensuring year-round farming.
- Prevents crop failures in drought-prone regions.
- Example: Indira Gandhi Canal (Rajasthan) gets water from the Bhakra Nangal Dam.
2. Hydroelectric Power Generation
- Dams help generate renewable electricity using the force of stored water.
- Hydroelectric power (HEP) is clean, sustainable, and reduces dependence on fossil fuels.
- Example: Tehri Dam (Uttarakhand) generates hydroelectricity for North India.
3. Flood Control
- Dams prevent flooding by controlling excess river water.
- They release water gradually, reducing the impact of heavy rainfall and storms.
- Example: Hirakud Dam (Odisha) controls floods in the Mahanadi River.
4. Domestic and Industrial Water Supply
- Dams provide water for drinking and household use.
- Many industries rely on dam water for manufacturing, cooling, and processing.
- Example: Sardar Sarovar Dam (Gujarat) supplies water to cities and industries.
5. Inland Navigation
- Dams help maintain water levels in rivers and canals for boat transport.
- Waterways are a cost-effective and eco-friendly mode of transport.
- Example: Farakka Barrage (West Bengal) improves navigation in the Hooghly River.
6. Fishing and Aquaculture
- Dams create artificial lakes (reservoirs) that support fishing industries.
- Local communities depend on these reservoirs for livelihood and food supply.
- Example: Govind Sagar Lake (Bhakra Nangal Dam) is famous for fish farming.
7. Recreation and Tourism
- Dams attract tourists for boating, picnics, and water sports.
- Reservoirs provide scenic beauty and boost the local economy.
- Example: KRS Dam (Karnataka) is a major tourist attraction.
8. Groundwater Recharge
- Dams help recharge groundwater by storing excess rainwater.
- This prevents over-extraction of groundwater and maintains water tables.
9. Drought Management
- By storing water, dams provide a steady supply during dry seasons.
- They help drought-prone areas maintain water security.
- Example: Jayakwadi Dam (Maharashtra) provides water to drought-hit regions.
Negative Aspects of Dams
While dams provide many benefits, they also have several negative impacts on the environment, society, and economy. Some of the major disadvantages of dams include:
1. Displacement of People
- Large dams often submerge villages, homes, and farmland, forcing people to relocate.
- Many tribal and rural communities lose their traditional land and livelihoods.
- Example: Sardar Sarovar Dam (Gujarat) displaced thousands of people.
2. Environmental Damage
- Dams disturb natural river flow, affecting aquatic ecosystems.
- Flooding of forests and wetlands leads to loss of biodiversity.
- Traps sediments that are important for soil fertility downstream.
3. Risk of Earthquakes and Landslides
- Large reservoirs create stress on the Earth’s crust, increasing the risk of earthquakes.
- Landslides occur due to water pressure on hills and mountains.
- Example: Tehri Dam (Uttarakhand) is in an earthquake-prone zone.
4. Disruption of Aquatic Life
- Dams block fish migration, affecting breeding and fishing industries.
- Changes in water temperature and oxygen levels impact aquatic biodiversity.
- Example: Farakka Barrage (West Bengal) affected fish movement in the Ganges.
5. Waterlogging and Salinization
- Poor drainage around dams leads to waterlogging, damaging crops.
- Excess water in soil causes salt buildup (salinization), reducing soil fertility.
6. High Construction and Maintenance Costs
- Dams require huge investments, often exceeding budgets.
- Costly maintenance and repairs make them economically challenging.
- Example: Bhakra Nangal Dam was extremely expensive to construct.
7. Disruption of Natural Flood Cycles
- Rivers naturally flood to replenish soil fertility, but dams prevent this.
- Downstream areas suffer from reduced silt deposition and poor agricultural productivity.
8. Climate Change Contribution
- Decomposed vegetation in reservoirs releases methane, a greenhouse gas.
- Large reservoirs contribute to local climatic changes.
9. Political and Social Conflicts
- Water-sharing disputes arise between states and countries.
- Example: Cauvery River Water Dispute between Karnataka and Tamil Nadu.
10. Risk of Dam Failure
- If a dam breaks, it causes catastrophic flooding, leading to loss of life and property.
- Example: Machchu Dam Disaster (Gujarat, 1979) killed thousands due to dam failure.
What is Rainwater Harvesting?
Rainwater harvesting (RWH) is the process of collecting, storing, and using rainwater for various purposes like irrigation, drinking, and groundwater recharge. It is an effective way to conserve water and prevent water scarcity.
Types of Rainwater Harvesting in India
1. Rooftop Rainwater Harvesting :- Tamil Nadu is the first state in India which has made rooftop rainwater harvesting structure compulsory to all the houses across the state.
- Collecting rainwater from rooftops and storing it in tanks or allowing it to percolate into the ground.
- Used in urban areas and villages to meet domestic water needs.
- Example: Tamil Nadu has made rooftop rainwater harvesting mandatory in buildings.
2. Surface Runoff Harvesting
- Collecting rainwater from roads, courtyards, and open areas and directing it to storage tanks or recharge pits.
- Helps prevent urban flooding and recharges groundwater.
3. Groundwater Recharge Methods
- Percolation Pits: Small pits filled with stones or sand to allow rainwater to seep into the ground.
- Recharge Wells: Deep wells that help replenish underground water reserves.
- Check Dams: Small barriers built across streams to slow water flow and improve percolation.
- Example: Maharashtra’s Jalyukt Shivar Abhiyan promotes check dams for groundwater recharge.
Traditional Rainwater Harvesting Methods in Different States
Different regions in India have unique traditional water conservation systems suited to their geography and climate.
1. Rajasthan – Johads & Baoris
Johads: Small earthen ponds used to collect and store rainwater for drinking and irrigation.
Baoris (Stepwells): Deep wells with steps leading to water, used in dry regions.
Example: The famous Chand Baori in Rajasthan.
2. Gujarat – Stepwells (Vavs)
Vavs: Large stepwells used for water storage and groundwater recharge.
Example: The Rani Ki Vav in Patan, a UNESCO heritage site.
3. Maharashtra – Bandharas & Percolation Tanks
Bandharas: Small check dams across rivers to store and recharge groundwater.
Percolation Tanks: Large tanks that allow rainwater to seep into the ground.
Example: Panchgani region uses percolation tanks for water conservation.
4. Karnataka – Kere (Tanks) System
Large artificial lakes built to store monsoon water for drinking and irrigation.
Example: The Hesaraghatta Lake in Bengaluru.
5. Tamil Nadu – Temple Tanks & Eris
Eris (Tanks): Ancient reservoirs used for irrigation.
Temple Tanks: Water bodies near temples used for religious and water storage purposes.
Example: Madurai’s Meenakshi Temple Tank.
6. West Bengal – Dighis & Pukurs
Dighis: Large ponds built near settlements to store rainwater.
Pukurs: Small artificial ponds for drinking and irrigation.
Example: Kolkata’s East Kolkata Wetlands use pukurs for water conservation.
7. Meghalaya – Bamboo Drip Irrigation
Bamboo Pipes used to transport and distribute rainwater to fields.
An eco-friendly and efficient system followed by tribal communities.
8. Himachal Pradesh – Kuhl Irrigation System
Kuhls: Man-made water channels that divert glacial meltwater to fields.
Example: Used widely in Kangra Valley.
9. Uttar Pradesh & Bihar – Ahar-Pyne System
Ahars: Reservoirs that store rainwater.
Pynes: Small channels that distribute stored water to fields.
Example: Common in South Bihar’s rural areas.
10. Kerala – Surangams
Surangams: Tunnel-like structures dug into hills to extract groundwater.
What are Multi-Purpose River Project & Advantages
Multipurpose river projects are large-scale water management systems that serve multiple functions such as irrigation, hydroelectric power generation, flood control, water supply, and recreation. These projects help in the sustainable development of water resources.
1. Irrigation for Agriculture
Provides year-round water supply for farming.
Helps in drought-prone areas where rainfall is uncertain.
Supports high-yield farming and ensures food security.
2. Hydroelectric Power Generation
Produces clean, renewable energy by harnessing water flow.
Reduces dependence on fossil fuels and cuts down carbon emissions.
Example: Tehri Dam generates hydroelectric power for Uttarakhand and nearby states.
3. Flood Control
Prevents flooding by regulating river water flow.
Reduces loss of life, property, and crops in flood-prone regions.
4. Drinking Water Supply
Provides clean and safe drinking water to cities and rural areas.
Supports industries, domestic use, and municipal water supply.
5. Groundwater Recharge
Prevents depletion of underground water by storing excess rainwater.
Helps in maintaining water tables and preventing droughts.
6. Navigation & Transportation
Maintains water levels in rivers, allowing inland water transport.
Reduces transportation costs and boosts trade.
Example: Farakka Barrage helps navigation in the Hooghly River.
7. Tourism & Recreation
Dams and reservoirs attract tourists for boating, fishing, and picnics.
Increases revenue and employment opportunities in local areas.
8. Prevention of Soil Erosion
Controls riverbank erosion by managing the water flow.
Protects fertile lands and helps in sustainable agriculture.
9. Regional Economic Development
Encourages industrial growth by providing water and electricity.
Increases employment in farming, fishing, tourism, and power industries.
10. Climate and Drought Management
Helps in mitigating drought effects by storing water for dry seasons.
Maintains environmental balance by regulating water supply.
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