Water Resources — Notes

Water Scarcity and the Need for Water Conservation and Management

Water Scarcity: A situation where the demand for water exceeds the available supply. This can occur not only in regions with low rainfall but also in areas with high rainfall if the water is polluted or access is unequal.

Causes of Water Scarcity:

• Uneven Distribution: Water availability varies significantly across different regions due to differences in seasonal and annual precipitation.
• Over-exploitation: Excessive use of water, particularly for irrigation to boost food production and by industries and urban populations.
• Pollution: Contamination of freshwater sources by domestic and industrial waste, chemicals, pesticides, and fertilisers, making it unfit for human use.
• Large and Growing Population: Increased demand for water for domestic use and food production.
• Urbanisation and Industrialisation: These lead to higher water and energy requirements and increased pressure on existing freshwater resources.

Why Water Scarcity Matters:

• Threatens food security and livelihoods.
• Can lead to ecological crises and degradation of natural ecosystems.
• Causes health hazards due to polluted water.
• Contributes to social inequalities due to unequal access.

Remember

Water scarcity is not just about the quantity of water available, but also its quality and the equitable distribution of access.

Exam-smart

Case studies of cities facing water scarcity despite high rainfall (due to pollution or over-extraction) are common. Be ready to explain the multiple reasons for scarcity beyond just rainfall.

Hydraulic Structures in Ancient India

Ancient Indians had sophisticated methods for water management and storage:

• Sringaverapura (Allahabad, 1st Century BC): Sophisticated rainwater harvesting system channeling floodwater of the Ganga.
• Mauryan Period: Extensive construction of dams, lakes, and irrigation systems.
• Kalinga, Nagarjunakonda, Bennur, Kolhapur: Evidences of advanced irrigation works.
• Bhopal Lake (11th Century): One of the largest artificial lakes of its time.
• Hauz Khas, Delhi (13th-14th Century): Tank constructed by Allauddin Khilji to supply water.

Remember

Traditional water management systems were often highly integrated with local ecological conditions and community needs.

Exam-smart

Questions might ask to identify or describe traditional hydraulic structures and their significance.

Multi-Purpose River Projects and Integrated Water Resources Management

Multi-purpose Projects: Large river valley projects designed to serve multiple purposes beyond just irrigation.

Purposes Served:

• Irrigation: Providing water to agricultural fields.
• Hydroelectric Power Generation: Producing electricity from flowing water.
• Domestic and Industrial Water Supply: Meeting the water needs of cities and industries.
• Flood Control: Regulating river flow to prevent floods.
• Recreation: Boating, tourism, etc.
• Inland Navigation: Facilitating water transport.
• Fish Breeding: Creating suitable habitats for aquatic life.

Examples:

• Bhakra-Nangal Project (Sutluj-Beas River): Used for hydel power and irrigation.
• Hirakud Project (Mahanadi Basin): Integrates water conservation with flood control.
• Sardar Sarovar Project (Narmada River): Aims to supply water to drought-prone areas of Gujarat and Rajasthan, and irrigate large areas.

Advantages of Multi-purpose Projects:

• Integrated approach to water resource management.
• Contribute to national development and economic progress.
• Provide essential resources like water and electricity.
• Can help control floods and droughts.

Disadvantages and Criticisms:

• Environmental Impacts:
• Poor Sediment Flow: Affects natural river flow and leads to excessive sedimentation in reservoirs, creating rocky stream beds.
• Habitat Fragmentation: Hinders the migration of aquatic fauna, especially for spawning.
• Submergence of Land: Floodplains are submerged, leading to decomposition of vegetation and soil.
• Induced Earthquakes: Increased pressure on the Earth's crust.
• Water-borne Diseases and Pests: Creation of new habitats for disease vectors.
• Pollution: Due to excessive water use and industrial discharge.
• Social Impacts:
• Displacement of People: Large-scale displacement of local communities, leading to loss of livelihood and cultural heritage.
• Inter-state Water Disputes: Disagreements over water sharing and diversion between states (e.g., Krishna-Godavari dispute).
• Economic Impacts:
• Changes in Cropping Patterns: Farmers may shift to water-intensive commercial crops, leading to soil salinisation.
• Deprivation of Silt: Floodplains are deprived of silt, a natural fertiliser, leading to land degradation.

Remember

While multi-purpose projects offer significant benefits, their environmental and social costs must be carefully considered and mitigated.

Exam-smart

A common question type involves comparing the advantages and disadvantages of multi-purpose projects, often presented in a case study format.

Schemes for Water Management

• Jal Jeevan Mission (JJM): Aims to provide assured supply of potable piped water to every rural household at 55 litres per capita per day.
• Atal Bhujal Yojana (Atal Jal): Focuses on improving groundwater management in water-stressed Gram Panchayats by encouraging community participation and behavioural change towards conservation.
• Pradhan Mantri Krishi Sinchayee Yojana: Ensures access to protective irrigation for all farms, improves water use efficiency, and promotes sustainable water conservation practices.

Rainwater Harvesting

Rainwater Harvesting: The process of collecting and storing rainwater for future use. This is a sustainable method of managing water resources, especially crucial in areas facing water scarcity.

Traditional Methods:

• Guls and Kuls (Western Himalayas): Diversion channels built for agriculture.
• Rooftop Rainwater Harvesting (Rajasthan): Storing water from rooftops in underground tanks (tankas) for drinking.
• Inundation Channels (Bengal): Used for irrigating fields in floodplains.
• Khadins (Jaisalmer) and Johads (Rajasthan): Structures built in agricultural fields to allow water to stand and moisten the soil.
• Tanka (Western Rajasthan): Underground tanks built within or near houses to store drinking water.

Modern Adaptations:

• Rooftop Rainwater Harvesting: Commonly adapted in both rural and urban areas to store water for domestic use.
• Mechanism: Rainwater from sloping roofs is collected via pipes and stored in underground tanks or sumps. Excess water can be used to recharge groundwater through abandoned dug wells or hand pumps.
• Mandatory in Tamil Nadu: The state has made rooftop rainwater harvesting compulsory for all buildings.
• Common in Shillong, Meghalaya: Despite high rainfall, the city uses rooftop harvesting to meet a significant portion of its water needs.
• Bamboo Drip Irrigation (Meghalaya): A 200-year-old system that uses bamboo pipes to transport spring water over long distances to irrigate fields, with water flow regulated by manipulating pipe positions.

Benefits of Rainwater Harvesting:

• Increases water availability: Provides a supplementary source of water, especially during dry periods.
• Recharges groundwater: Helps replenish underground water levels.
• Reduces reliance on other sources: Decreases dependence on groundwater and surface water.
• Environmentally friendly: Reduces the need for large infrastructure projects and conserves natural water bodies.
• Cost-effective: Can be implemented at household or community level with relatively low costs.
• Improves water quality: Rainwater is considered a pure form of natural water.

Remember

Rainwater harvesting is a vital method for both water conservation and augmenting water supply, particularly in regions with seasonal rainfall.

Exam-smart

Questions often require describing specific traditional or modern rainwater harvesting techniques and explaining their importance and applicability in different regions.

Classification of Water Scarcity Situations