BEVAE-181 Study Notes — Block 2 Unit 4: Land and Water Resources
Detailed study notes for BEVAE-181 Block 2 Unit 4. Covers renewable vs non-renewable resources, the hydrological water cycle (all seven processes), global water distribution, groundwater zones (aeration, saturation, water table, aquifer), India's rainfall figures, floods and droughts with causes and mitigation, traditional water harvesting methods (johads, kunds, kuls, bamboo drip, rooftop harvesting), soil types of India, soil formation stages, land degradation statistics (FAO 1996), and soil erosion control methods. Includes eight SVG diagrams, SAQs, and terminal question answers. Free PDF download.
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4.3 Renewable Water Resource — Water Cycle, Forms of Water
4.4 Over-exploitation of Groundwater & Degradation of Water Sources
4.5 Floods and Droughts — Causes, Effects, Water Harvesting
4.6 Conservation and Management of Water Resources
4.7 Non-Renewable Land Resource — Soil Types, Formation, Degradation
4.8 Land Use Planning and Management
4.9 Summary
SAQ Self-Assessment Questions 1–2 with Answers
TQ Terminal Questions with Model Answers
⚡ Quick Revision Card
Block 2 · Unit 4
Land and Water Resources
Nature has given us land and water as its two most vital gifts. Water is a renewable resource but only ~1% is accessible. Soil and land are non-renewable — once degraded, they take thousands of years to recover. This unit explores these critical resources, their over-exploitation, degradation, and how to conserve and manage them wisely for future generations.
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Section 4.1
Introduction
Natural resources are the wealth nature has given us — essential for survival and development of all life forms. Our demand is rapidly increasing because of the tremendous increase in human population and indiscriminate use without realising their limits.
⚠️ The Core Problem: Intensive and unregulated use of land (cultivation, grazing, exploitation of plant material) has adversely affected plant communities and soil regeneration. Industries add toxic wastes to water bodies. Mining causes quantitative and qualitative deterioration of water resources. Resources are NOT unlimited.
🎯 Expected Learning Outcomes
Define renewable and non-renewable resources
Explain how human activities in agriculture and industry degrade land and water resources
Describe how environmental degradation leads to conditions of floods and droughts
Explain soil erosion and desertification; how wise planning enables sustainable use of land and water
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Section 4.2
Renewable and Non-Renewable Resources
Renewable vs Non-Renewable Resources — At a Glance
🧠 Key insight: Water is RENEWABLE (cycles back) but SOIL is NON-RENEWABLE (takes 1000s of years to form one centimetre of topsoil). This is why soil conservation is so critical!
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Section 4.3
Renewable Water Resource
Water is one of the most essential components of life. Only 1% of all water on Earth is readily accessible for human use. Of this: 73% → agriculture, 20% → industry, 7% → domestic/recreational.
Global Water Distribution — Where is Earth's Water?
Key fact: Only 3% of Earth's water is fresh. Of that, 80% is frozen. Groundwater = 98.4% of usable liquid fresh water!
Type of Fresh Water
% of Fresh Water
% Available for Use
Frozen (Ice caps, glaciers)
80.00%
—
Liquid (Total)
20.00%
—
Lakes
0.20%
1.0%
Soil
0.04%
0.2%
Rivers
0.02%
0.1%
Atmosphere
0.02%
0.1%
Biological (Metabolic)
0.001%
0.005%
Groundwater
19.7%
98.4%
Source: IGNOU BEVAE-181 Block 2, Table 4.1
🇮🇳 India's Water: India receives average rainfall of 400 m ham (million hectare metres)/year. Of this: 185 m ham → surface water, 50 m ham → underground water, 165 m ham → stored in soil. Total fresh water exceeds present and future needs — but uneven distribution causes chronic shortage.
The Water Cycle (Hydrological Cycle)
The movement of water on Earth is continuous, forming complex inter-related loops. The water cycle involves atmosphere, sea, earth, and all living biota.
The Hydrological Cycle — All Key Processes
Solar energy drives the water cycle: Evaporation/Transpiration → Condensation → Precipitation → Runoff → Infiltration → Groundwater → Ocean
Water vapour → ice crystals directly (no liquid phase)
Formation of frost on cold surfaces
Runoff
Excess rain flows over land along natural slope
Main source for lakes and rivers; causes floods
Sublimation
Solid ice → vapour without passing through liquid
Ice disappearing during freezing temperatures
Evaporation
Liquid water → vapour at ambient temperature
Ocean surface = largest source of atmospheric vapour
Transpiration
Water vapour lost from plant leaves
1 hectare of corn loses ~35,000 litres/day!
Forms of Water
🏊 Fresh Water
Total salt content < 1.5%. Contains dissolved salts from weathering of rocks and soil erosion. Important for aquatic vegetation and phytoplankton.
🌿 Brackish Water
Salt content 0.5–3.5%. Found in estuaries where fresh water from rivers mixes with sea water. Intermediate salinity.
🌊 Marine Water
Average salinity = 3.5% (35 parts per 1000 parts water). Some salt lakes can exceed 35%. Biotic activity greatly restricted at very high salinity.
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Section 4.4
Groundwater Zones & Degradation of Water Sources
Groundwater Zones — Zone of Aeration, Saturation, and Aquifer
📦 Box 4.1: Groundwater Depletion Crisis
Groundwater is estimated to supply ~50% of drinking water. Its availability depends on rainfall and recharge. The crisis stems from: lack of water conservation methods, inefficient use, poor groundwater recharge, and water pollution (excess fluoride, arsenic, iron, salt, organic matter). This is more a human-made crisis than a natural one. Both farming and industrial sectors increasingly use wells, draining aquifers faster than natural recharge.
Degradation of Water Sources
Most water bodies face severe pollution from agriculture, urbanisation, industrialisation, and deforestation:
Siltation of rivers/lakes (from soil erosion) → reduces water holding capacity → ravaging floods
Sewage + industrial effluents → pollution + algal blooms → fish die
Paradox: Lack of safe drinking water even in above-average rainfall areas!
💧 Agriculture — Biggest Water Consumer: 70% of world's water goes to agriculture. In Asia: 86% of annual water withdrawal. In North/Central America: 49%. In Europe: 38%. India's Green Revolution massively increased water use through irrigation. Implications: water-efficient measures giving more productivity per unit of water input are urgently needed.
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Section 4.5
Floods and Droughts
Floods vs Droughts — Key Comparison
Causes of Floods
Heavy rainfall exceeding the river's carrying capacity
Deforestation → reduced water absorption → higher runoff
Encroachment on flood plains
Silting of river beds (reduces capacity)
Poor watershed management
Flood Mitigation Measures
Construction of dams and reservoirs at appropriate places
Strengthening embankments on rivers and canals
Improving carrying capacities by periodic desilting and deepening
Diversion of flood waters to other canals and channels
Rajasthan (342,239 sq. km, ~54 million people) suffered a severe drought in 2000. 31 out of 32 districts affected (25 severely). 73.64% villages affected — 33.04 million people and 39.97 million cattle.
Severity: Out of 2,647 major water reservoirs, only 300 were filled. 75–100% of crops destroyed → mass migration for employment. Drought classified: Economic (crop/livestock loss), Environmental (soil erosion), Social (food shortage, conflicts).
Human causes aggravating drought: Felling trees for firewood, deforestation for agriculture/housing, mining, unscientific farming, indiscriminate groundwater extraction.
Water Harvesting Measures (Drought Prevention)
Traditional Water Harvesting Methods in India
SAQ 1
Self Assessment Questions — Sections 4.2–4.5
Fill in the Blanks
i) _______ is one of the most important substances for sustaining human life. ii) Movement of water on the _______ is continuous. iii) Water, a universal _______, invariably contains many soluble _______. iv) Agriculture is by far the biggest _______ of water. v) A _______ is the discharge of water that exceeds the canal capacity of the _______. vi) The Krishna _______ reached its decision in 1973. vii) Several _______ methods are being used in the traditional system of water _______.
✅ Answers (from IGNOU textbook)
i) Fresh water ii) Earth iii) Solvent, Salts iv) Consumer v) Flood, River vi) Tribunal vii) Several, Harvesting
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Section 4.6
Conservation and Management of Water Resources
By 2025, one-third of the world's population will experience severe water scarcity. Already: 1 billion+ lack safe drinking water; 3 billion lack basic sewage systems. Over 90% of sewage in developing countries returns untreated to land/water.
Key Water Conservation and Management Methods
Wastewater Treatment Process: Heavy particles settle by themselves → finer particles settled by adding alum and caustic soda → filtered through sand/earth → air blown through (removes CO₂, H₂S, adds oxygen) → chlorination kills harmful germs → water usable for irrigation. Growing algae and water hyacinth provides double benefit: cleans phosphates/nitrates from water AND the plants can produce biogas.
☀️ Desalination of Sea Water: Using solar energy, sea water is distilled to obtain fresh water of good quality. Used at Bhavnagar (Gujarat) and Churu (Rajasthan).
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Section 4.7
Non-Renewable Land Resource
Land is the foundation on which the entire ecological system rests. In 1901, India's land mass was shared by 238 million people — now by over 1,200 million people. Mismanagement (deforestation, overuse) has caused considerable damage to soil quality and landscape.
Major Soil Types of India
Major Soil Types of India — Region, Colour, Crops
Processes Involved in Soil Formation
Soil Formation — From Rock to Fertile Humus (3 Stages)
Humus = amorphous, colloidal, dark substance. Source of energy for soil microorganisms. Gives soil a loose texture → better aeration. Being colloidal → great capacity for retaining water and nutrients. Humus greatly improves soil fertility.
Land Degradation
📌 Definition
Land degradation = reduction in the capacity of the soil to produce goods and services in terms of quality and quantity. Human activities include: deforestation, farming, damming of rivers, industrialisation, mining, roads, and human settlements.
Extent
Cause
Key Impact
580 million ha
Deforestation
>200 million ha tropical forests destroyed 1975–1990
680 million ha
Overgrazing
~20% of world's pasture/rangelands damaged. Africa and Asia worst.
137 million ha
Fuelwood consumption
~1730 million m³ harvested annually
550 million ha
Agricultural mismanagement
25,000 million tonnes of soil lost to water erosion annually
19.5 million ha
Industrialisation & urbanisation
Valuable agricultural land converted to roads, mines, buildings
Source: FAO, 1996
🇮🇳 India's Wasteland: Between 30–50% of India's private and common land is ecologically degraded — referred to as "wasteland" (land not producing its potential biomass). Programmes: IWDP (Integrated Wastelands Development Project), Society for Promotion of Wasteland Development (SPWD). The Charagah development in Rajasthan (common lands allotted for cattle grazing) is a key SPWD activity.
i) _______ forms the uppermost layer of _______. ii) Mechanical forces acting upon the rocks cause physical _______. iii) _______ is a by-product of efforts to exploit land for maximum _______ production. iv) Land _______ refers to the process of deterioration in the quality of land. v) _______ are common lands allotted for cattle grazing in a _______. vi) Land should be used according to its _______ and _______. vii) Excessive irrigation causes complete _______ or water logging of the _______.
✅ Answers (from IGNOU textbook)
i) Soil, Land ii) Weathering iii) Overgrazing, Livestock iv) Degradation v) Charagahs, Village vi) Suitability, Capability vii) Saturation, Soil
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Section 4.8
Land Use Planning and Management
Land must be used according to its suitability and capability. As food needs grow, fertile agricultural land must not be encroached upon for roads and buildings. Hill areas should be kept under forest cover for fuel, fodder, timber, groundwater recharge, and flood prevention.
Measures for Soil Erosion Control
Treatment of Soil Sickness: Excessive irrigation causes waterlogging → soil loses productivity → salinisation and alkalinity. Control by sealing canal/reservoir leakage points and using only required amounts of water. Saline soils treated with gypsum + good drainage. Rotation of legumes (peas, beans) removes nutrient deficiencies.
📋 Unit 4 — Summary
Renewable resources (water, forests, wildlife) regenerate naturally. Non-renewable resources (coal, minerals, soil) cannot be regenerated once used — soil takes 1000s of years per centimetre!
Only 3% of Earth's water is fresh; 80% of that is frozen. Only 1% of ALL water is accessible. Of this, 73% goes to agriculture. India receives 400 m ham/year rainfall.
Water cycle: Evaporation → Transpiration → Condensation → Precipitation → Runoff + Infiltration → Groundwater → Ocean. Driven by solar energy.
Groundwater exists in two zones: Zone of Aeration (air + water) and Zone of Saturation (all water). The Water Table is the boundary. Aquifer = rock layer through which water percolates.
Floods kill 20,000+/year, affect 75 million annually. Droughts are "creeping calamities" developing slowly. Both preventable through proper land-use and water management.
Traditional water harvesting: johads, kunds, kuls (up to 10 km long, Spiti), bamboo drip irrigation (NE India), rooftop harvesting (Rashtrapati Bhavan — 1 lakh litre tank).
Soil forms by: Weathering → Mineralisation → Humification → Humus (dark, colloidal, retains water and nutrients, improves fertility).
Land management: Use land per suitability + capability. Control erosion by vegetation, drainage, check dams, coir netting. Restore fertility by crop rotation with legumes. Treat saline soils with gypsum.
Terminal Questions with Detailed Answers
Exam-style questions from the IGNOU textbook.
1
What are renewable and non-renewable resources? Explain with examples.
✅ Model Answer
Renewable Resources: Resources regenerated by natural processes over time. They can be used repeatedly if managed wisely. Examples: Forests (trees grow back), water (cycles through the hydrological cycle), wildlife, pastures, and aquatic life. Water is renewable because it gets recycled through the water cycle.
Non-Renewable Resources: Resources that cannot be regenerated once used — formed over millions of years, permanently lost when consumed. Examples: Fossil fuels (coal, petroleum — burn up and cannot be recovered), minerals, and soil (one centimetre of topsoil takes thousands of years to form).
The key difference is the timescale of renewal: renewable resources renew within a human lifetime; non-renewable resources take geological timescales to form.
Recharging Groundwater: Storm water, wastewater, or domestic drains fed into pits/trenches. Flood water injected into aquifers through deep pits or spread on fields through ditches.
Wastewater Treatment and Reuse: Sedimentation (alum + caustic soda) → filtration (sand/earth) → aeration → chlorination → usable for irrigation. Water hyacinth and algae absorb phosphates and nitrates.
Desalination: Solar energy used to distil sea water to fresh water (Bhavnagar, Gujarat; Churu, Rajasthan).
Reducing Overconsumption: Fix leaking taps, implement efficient irrigation systems, change cropping patterns to reduce water use.
Diverting Surplus Water: Divert excess flood water to water-scarce regions — removes flood danger while benefiting dry areas.
3
Describe the essential components of land management.
✅ Model Answer
Land management has two essential components:
A. Soil Management:
(i) Control of Soil Erosion: Plant grasses, shrubs, trees as vegetative cover; construct drainage systems; build check dams to prevent gully formation (e.g., Chambal ravines); stone walls along coasts; tree/shrub windbreaks in deserts; coir netting on vulnerable slopes.
(ii) Restore Fertility: Crop rotation with legumes (peas, beans add nitrogen); apply organic matter (green manures, straw) to improve water retention; treat saline soils with gypsum + good drainage.
(iii) Prevent Waterlogging: Seal leakage in canals, reservoirs; use only required amounts of water in irrigation.
B. Land Use Planning:
Use land per suitability (load-bearing ability) and capability (fertility). Reduce encroachment of fertile agricultural land for non-agricultural purposes. Keep hill areas under forest cover. Select industry/dam/mining sites carefully to minimize environmental disruption.