Comprehensive Study Notes on Water Resources and Management

Global Water Availability and the Hydrological Cycle

• Distribution of Water on Earth: Approximately three-fourths of the Earth's surface is covered with water ($\frac{3}{4}$). However, only a small proportion is freshwater that can be utilized for human consumption and activity.
• Sources of Freshwater:   - Surface runoff.   - Groundwater.
• The Hydrological Cycle: This cycle ensures that water is a renewable resource; water is continually being renewed and recharged through this process. All water on Earth moves within this cycle.
• Predictive Scarcity: Despite the abundance and renewability of water, it is predicted that by the year 2025, nearly two billion people will live in conditions of absolute water scarcity.

Understanding Water Scarcity

• Misconception of Scarcity: Scarcity is often associated only with low-rainfall or drought-prone regions, such as the deserts of Rajasthan where women collect water in earthen pots (matkas) and travel long distances.
• Primary Causes of Scarcity:   - Variation in Precipitation: The availability of water varies across different spaces and times due to seasonal and annual precipitation changes.   - Over-exploitation: Excessive use and depletion of water resources faster than they can recharge.   - Unequal Access: Disparities in water access among different social and economic groups.
• Impact of Population Growth:   - A large and growing population increases demand for domestic use.   - Greater food requirements lead to the expansion of irrigated areas for dry-season agriculture.   - Irrigated Agriculture: This is the largest consumer of water. Modern solutions include developing drought-resistant crops and dry farming techniques.
• Groundwater Depletion: Many farmers have private wells and tube-wells for irrigation. While this increases productivity initially, it leads to falling groundwater levels, threatening future water availability and food security.
• Urbanization and Industrialization:   - Industrial Pressure: Post-independent India seen massive growth in industries and MNCs (Multinational Corporations) that are heavy users of water.   - Energy Needs: Much of the energy for industries and urban centers comes from hydroelectric power.   - Urban Lifestyles: Dense urban populations and lifestyles in housing societies (using private groundwater pumping) have exacerbated resource depletion.
• Qualitative Water Scarcity: Even in areas with ample water quantity, the resource may be unusable due to pollution from:   - Domestic and industrial wastes.   - Chemicals and pesticides.   - Fertilizers used in agriculture.

National Water Missions and Initiatives

• Jal Jeevan Mission (JJM):   - Goal: To enable every rural household to have an assured supply of potable piped water through functional tap connections.   - Service Level: 55 litres per capita per day on a regular long-term basis.
• Atal Bhujal Yojana (Atal Jal):   - Scope: Implemented in 8,220 water-stressed Gram Panchayats across 229 administrative blocks/talukas in 80 districts of seven Indian states: Gujarat, Haryana, Karnataka, Madhya Pradesh, Maharashtra, Rajasthan, and Uttar Pradesh.   - Regional Impact: These states account for 37% of India's water-stressed (over-exploited, critical, and semi-critical) blocks.   - Key Objective: Encouraging behavioral changes in communities from a consumption-based attitude to one of conservation and smart management.
• Pradhan Mantri Krishi Sinchayee Yojana (PMKSY):   - Objective: Ensure protective irrigation for all agricultural farms (har khet ko pani).   - Focus: Improving on-farm water use efficiency (per drop more crop) and expanding cultivable areas under assured irrigation.

Multi-Purpose River Projects and Integrated Water Resources Management

• Historical Sophisticated Hydraulic Structures:   - 1st Century B.C.: Sringaverapura near Allahabad featured a system to channel floodwaters from the River Ganga.   - Chandragupta Maurya: Extensive construction of dams, lakes, and irrigation systems during his reign.   - Regional Evidences: Sophisticated irrigation works in Kalinga (Odisha), Nagarjunakonda (Andhra Pradesh), Bennur (Karnataka), and Kolhapur (Maharashtra).   - 11th Century: Construction of Bhopal Lake, one of the largest artificial lakes of its era.   - 14th Century: Allauddin Khilji (Khalji) built a tank in Hauz Khas, Delhi, to supply water to the Siri Fort area.
• Definition of a Dam: A barrier across flowing water that obstructs, directs, or retards flow. The term "Dam" often refers specifically to the reservoir (impoundment) rather than just the physical structure.   - Spillway/Weir: A section where water flows intermittently or continuously.
• Classification of Dams:   - By Structure/Material: Timber dams, embankment dams, or masonry dams.   - By Height: Low, medium-height, and high dams (alternatively large and major dams).
• Evolution of Purpose: Originally built to impound water for irrigation, modern dams are multi-purpose projects used for:   - Electricity generation.   - Domestic and industrial water supply.   - Flood control.   - Recreation and tourism.   - Inland navigation.   - Fish breeding.
• Key Indian Projects:   - Bhakra - Nangal Project: Located in the Sutluj-Beas river basin; used for hydel power and irrigation.   - Hirakud Project: Located in the Mahanadi basin; integrates water conservation with flood control.   - Sardar Sarovar Dam: Built over the Narmada River in Gujarat. It covers four states (Maharashtra, Madhya Pradesh, Gujarat, and Rajasthan) and provides irrigation to 18.45 lakh hectares in Gujarat and 2.46 lakh hectares in Rajasthan's Barmer and Jalore districts.
• Societal View: Jawaharlal Nehru termed dams the "temples of modern India" as they were seen to integrate agricultural/village development with rapid industrialization and urban growth.

Challenges and Criticisms of Large Dams

• Ecological Impact:   - Natural Flow Disruption: Dams cause poor sediment flow, leading to excessive sedimentation at the reservoir bottom.   - Stream Bed Changes: Excessive sedimentation results in rockier stream beds and degrades aquatic habitats.   - Migration Obstruction: Fragmentation of rivers prevents aquatic fauna (fish) from migrating, especially for spawning.   - Vegetation/Soil Decomposition: Reservoirs on floodplains submerge land, leading to soil degradation.
• Social and Ethical Issues:   - Large-scale displacement of local communities and loss of livelihoods.   - Inter-state water disputes, such as the Krishna-Godavari dispute (Karnataka and Andhra Pradesh objecting to Maharashtra’s water diversion at Koyna).
• Failure in Objectives:   - Flood Triggers: Ironically, sedimentation has caused some dams to trigger floods during excessive rain rather than control them.   - Loss of Silt: Dams prevent silt (a natural fertilizer) from reaching floodplains, leading to land degradation.   - Environmental Hazards: Multi-purpose projects have been linked to induced earthquakes, water-borne diseases, and pests.
• Agricultural Shifts: Irrigation leads to shifts toward water-intensive commercial crops, causing soil salinisation.

Traditional and Regional Rainwater Harvesting Techniques

• Regional Systems:   - Western Himalayas: People use diversion channels known as guls or kuls for agricultural irrigation.   - Bengal: Inundation channels are used to irrigate floodplains.   - Rajasthan (Arid Regions): Storage structures like khadins (Jaisalmer) and Johads keep water standing to moisten the soil.
• Rooftop Rainwater Harvesting in Rajasthan:   - In Bikaner, Phalodi, and Barmer, houses use underground tanks or tankas for drinking water.   - Tanka Dimensions: In Phalodi, one recorded tank was 6.1 metres deep, 4.27 metres long, and 2.44 metres wide.   - Mechanism: Connected to sloping roofs via pipes. The first rain is discarded to clean the system; subsequent rainwater is stored.   - Palar pani: The local term for rainwater, considered the purest form of water.
• Modern Examples and Mandates:   - Tamil Nadu: The first Indian state to make rooftop rainwater harvesting compulsory for all houses by law, with penalties for defaulters.   - Shillong, Meghalaya: Despite Cherapunjee and Mawsynram (the world's highest rainfall areas) being only 55 km away, Shillong faces water shortages. Consequently, households harvest 15-25% of their water needs via rooftops.   - Gendathur, Karnataka: A village in Mysuru where 200 households harvest rainwater. With an annual precipitation of 1,000 mm and 80% collection efficiency, each house can collect 50,000 litres annually.

Bamboo Drip Irrigation System

• Origin: A 200-year-old system used in Meghalaya.
• Process: Tapping stream and spring water using bamboo pipes.
• Functionality:   - Approximately 18-20 litres of water enters the bamboo system.   - It is transported hundreds of metres over hills using gravity.   - Pipe positions are manipulated to control flow.   - Eventually, the flow is reduced to 20-80 drops per minute and delivered directly to the plant's roots.