Water Resources

2.1 Core concepts

• Water is a cyclic resource with abundant supplies on the globe. About 71% of the earth's surface is covered with water, but freshwater constitutes only about 3% of total water, and only a very small proportion of freshwater is effectively available for human use. The availability of freshwater varies over space and time, and tensions over its sharing have become contested issues among communities, regions and states (NCERT §Introduction, p. 41).
• India's water budget — India accounts for 2.45% of world surface area, 4% of world water resources and more than 17% of world population. Total precipitation-based water in a year is about 4,000 cubic km. Availability from surface water and replenishable groundwater is 1,869 cubic km, but only 60% of this can be put to beneficial use — so the total utilisable water resource is 1,122 cubic km (NCERT §Water Resources of India, p. 41).
• Surface water — four major sources: rivers, lakes, ponds and tanks. India has about 10,360 rivers and tributaries longer than 1.6 km each. Mean annual flow in all river basins is 1,869 cubic km, but topographical, hydrological and other constraints mean only about 690 cubic km (32%) of available surface water can actually be utilised (NCERT §Surface Water Resources, pp. 41–42).
• Water flow in a river depends on the size of its catchment area or river basin and the rainfall within its catchment. India has high spatial variability in precipitation, concentrated mainly in the monsoon season. The Ganga, Brahmaputra and Indus have huge catchment areas. Given that precipitation is relatively high in the catchments of the Ganga, Brahmaputra and Barak, these three rivers — though accounting for only about one-third of the country's total area — contribute about 60% of total surface water resources. Much of the annual flow of south-Indian rivers like the Godavari, Krishna and Kaveri has been harnessed, but harnessing of the Brahmaputra and Ganga basins is yet to be done (NCERT p. 42).
• Groundwater — total replenishable groundwater resources are about 432 cubic km. Utilisation is very high in Punjab, Haryana, Rajasthan and Tamil Nadu, moderate in Gujarat, Uttar Pradesh, Bihar, Tripura and Maharashtra, and low (only a small proportion of potential) in Chhattisgarh, Odisha and Kerala. If the present trend continues, demand for water will outstrip supplies, leading to social upheaval and disruption (NCERT §Groundwater Resources, p. 42).
• Lagoons and backwaters — India's vast coastline is very indented in some states; this has formed a number of lagoons and lakes. Kerala, Odisha and West Bengal have vast surface-water resources in these lagoons and lakes. Although the water is generally brackish, it is used for fishing and for irrigating paddy crops, coconut etc. (NCERT §Lagoons and Backwaters, p. 42).
• Water demand and utilisation — India has traditionally been an agrarian economy, with about two-thirds of its population dependent on agriculture. Hence, irrigation has been given very high priority in the Five Year Plans, with multipurpose river-valley projects like Bhakra-Nangal, Hirakud, Damodar Valley, Nagarjuna Sagar and the Indira Gandhi Canal Project. India's water demand is currently dominated by irrigational needs. Agriculture accounts for 89% of surface water and 92% of groundwater utilisation; industry accounts for 2% of surface water and 5% of groundwater; the domestic sector accounts for 9% (surface) — i.e. the domestic share is higher in surface than in groundwater (NCERT §Water Demand and Utilisation, p. 42).
• Demand of water for irrigation — irrigation is necessary because of spatio-temporal variability in rainfall. Large tracts of the country are deficient in rainfall and drought-prone — north-western India and the Deccan plateau constitute such areas. Even in areas of ample rainfall like West Bengal and Bihar, breaks in monsoon or its failure create dry spells detrimental to agriculture. Water-hungry crops like rice, sugarcane and jute make irrigation necessary (NCERT pp. 42–44).
• Provision of irrigation makes multiple cropping possible and yields are higher on irrigated than unirrigated land. High-yielding varieties need regular moisture supply, which is why the Green Revolution strategy succeeded largely in Punjab, Haryana and western Uttar Pradesh. In Punjab, Haryana and western UP, more than 85% of net sown area is under irrigation; of the total net irrigated area, 76.1% in Punjab and 51.3% in Haryana is irrigated by wells and tubewells, showing very high groundwater development — and consequent groundwater depletion (NCERT §Demand of Water for Irrigation, p. 44).
• Over-use of groundwater has lowered the water table; over-withdrawals in Rajasthan and Maharashtra have increased fluoride concentration in groundwater, and this practice has led to increased arsenic in parts of West Bengal and Bihar (NCERT p. 44).
• PMKSY (Pradhan Mantri Krishi Sinchayee Yojana) — launched by the Central Government in 2015–16 with an overarching vision of ensuring access to some means of protective irrigation for all agricultural farms. Broad objectives: (i) enhance physical access of water on the farm and expand cultivable area under assured irrigation — "Har khet ko pani"; (ii) promote integration of water source, distribution and efficient use through appropriate technologies and practices; (iii) improve on-farm water-use efficiency to reduce wastage and increase availability in both duration and extent — "Per drop more crop"; (iv) introduce sustainable water-conservation practices; (v) ensure integrated development of rain-fed areas using the watersheds approach (NCERT "Do You Know?" box, p. 44).
• Emerging water problems — declining per-capita availability of water (population rising), and pollution by industrial, agricultural and domestic effluents (NCERT §Emerging Water Problems, p. 44).
• Deterioration of water quality — water quality refers to its purity. Water gets polluted by foreign matters such as micro-organisms, chemicals, industrial and other wastes that render it unfit for human use. Pollutants in lakes/streams/rivers/oceans dissolve or lie suspended, damaging aquatic systems; they also seep down and pollute groundwater (NCERT §Deterioration of Water Quality, pp. 44–45).
• Water Conservation and Management — since freshwater availability is declining and demand is rising, the need has arisen to conserve and effectively manage this resource for sustainable development. Desalinisation from sea is considered negligible due to high cost. India needs to develop water-saving technologies, prevent pollution, encourage watershed development, rainwater harvesting, water recycling and reuse, and conjunctive use of water (NCERT §Water Conservation and Management, p. 45).
• Prevention of Water Pollution — major rivers retain better water quality in less densely populated upper stretches in hilly areas; in plains, river water is used intensively for irrigation, drinking, domestic and industrial purposes. Drains carrying agricultural (fertilisers, insecticides), domestic (solid and liquid wastes) and industrial effluents join the rivers; concentration of pollutants is highest in summer when flow is low. The Central Pollution Control Board (CPCB) in collaboration with State Boards monitors water quality of national aquatic resources at 507 stations, and finds organic and bacterial contamination to be the main source of river pollution. The Yamuna river is the most polluted river in the country between Delhi and Etawah. Other severely polluted rivers include the Sabarmati at Ahmedabad, Gomti at Lucknow, the Kali, the Adyar, the Cooum (entire stretches), the Vaigai at Madurai, the Musi at Hyderabad and the Ganga at Kanpur and Varanasi. Groundwater pollution has occurred due to high concentrations of heavy/toxic metals, fluoride and nitrates (NCERT §Prevention of Water Pollution, p. 46).
• Legal framework: Water (Prevention and Control of Pollution) Act 1974, Water Cess Act 1977 and Environment Protection Act 1986 — but these have not been implemented effectively (in 1997, 251 polluting industries were located along rivers and lakes). The Water Cess Act 1977 has had marginal impact. Public awareness and action can be very effective in reducing pollutants from agricultural activities, domestic and industrial discharges (NCERT p. 47).
• Recycle and Reuse of Water — use of lesser-quality reclaimed wastewater can be an attractive option for industries for cooling and fire-fighting; in urban areas water after bathing and washing utensils can be used for gardening; water used for washing vehicles can also be used for gardening. This would conserve better-quality water for drinking. Currently recycling is on a limited scale, but there is enormous scope (NCERT §Recycle and Reuse of Water, p. 47).
• Watershed Management — efficient management and conservation of surface and groundwater resources. It involves prevention of runoff and storage and recharge of groundwater through methods like percolation tanks, recharge wells, etc. In a broader sense, watershed management includes conservation, regeneration and judicious use of all resources — natural (land, water, plants, animals) and human — within a watershed (NCERT §Watershed Management, p. 47).
• Central and State Governments and NGOs run watershed programmes:
• Haryali — a watershed development project sponsored by the Central Government, aimed at enabling the rural population to conserve water for drinking, irrigation, fisheries and afforestation. Executed by Gram Panchayats with people's participation (NCERT p. 47).
• Atal Bhujal Yojana (Atal Jal) — implemented in 8,220 water-stressed Gram Panchayats of 229 administrative blocks/talukas in 80 districts of 7 states — Gujarat, Haryana, Karnataka, Madhya Pradesh, Maharashtra, Rajasthan and Uttar Pradesh — accounting for about 37% of the total number of water-stressed (over-exploited, critical and semi-critical) blocks in India. One key aspect is bringing behavioural change in the community from consumption to conservation and smart water management (NCERT "Do You Know?" box, p. 47).
• Neeru-Meeru (Water and You) — programme in Andhra Pradesh for water-harvesting structures (NCERT p. 47).
• Arvary Pani Sansad — in Alwar, Rajasthan, has constructed percolation tanks, dug-out ponds (Johads), check dams through people's participation (NCERT p. 47).
• Tamil Nadu has made water-harvesting structures compulsory in houses — no building can be constructed without rainwater-harvesting structures (NCERT p. 47).
• Ralegan Siddhi (Case Study) — a small village in Ahmadnagar district of Maharashtra; it has become an example for watershed development throughout the country. In 1975, the village was caught in a web of poverty and illicit liquor trade. A retired army personnel settled in the village and took up watershed development — voluntary labour, family planning, prevention of open grazing and tree felling, liquor prohibition. Work began with a percolation tank (which initially leaked but was repaired by villagers); the seven wells below it swelled with water in summer for the first time. A youth group called Tarun Mandal worked to ban the dowry system, caste discrimination and untouchability; cultivation of water-intensive crops like sugarcane was banned; pulses, oilseeds and certain cash crops with low water requirements were encouraged. All local-body elections began to be held on the basis of consensus; a system of Nyay Panchayats (informal courts) was set up — since then no case has been referred to the police (NCERT Case Study, p. 48).
• Rainwater Harvesting — a method to capture and store rainwater for various uses, and to recharge groundwater aquifers. It is a low-cost, eco-friendly technique that increases water availability, checks declining groundwater table, improves quality of groundwater through dilution of fluoride and nitrates, prevents soil erosion and flooding, and arrests salt-water intrusion in coastal areas if used to recharge aquifers (NCERT §Rainwater Harvesting, p. 50).
• Traditional methods: surface storage in lakes, ponds, irrigation tanks. In Rajasthan, Kund or Tanka — a covered underground tank — is constructed near or in the house/village to store harvested rainwater. NCERT Fig. 4.3 shows four methods: harvesting through watershed management (stone wall + check dam), through lakes (Eris, Tamil Nadu), through service wells (rooftop collection → brick filter → service well) and through recharge wells (rooftop → sand filter → collection tank → recharge well).
• National Water Policy 2012 — assesses existing situation and proposes a unified national framework. Salient features: (i) emphasis on a national water framework law and comprehensive legislation for optimum development of inter-State rivers; (ii) after meeting pre-emptive needs for safe drinking water and sanitation, achieving food security, livelihood support to the poor and high-priority allocation for minimum ecosystem needs, water be treated as an economic good to promote conservation and efficient use; (iii) adaptation strategies for climate change; (iv) benchmarks for water uses (water footprints, water auditing); (v) removal of large disparity in stipulations for water supply in urban and rural areas; (vi) water-resources projects to be managed with community participation (NCERT Box, p. 50).
• Jal Kranti Abhiyan (2015–16) — launched to ensure water security through per-capita availability. Activities: (1) selection of one water-stressed village in each of 672 districts to create a 'Jal Gram'; (2) identification of model command areas of about 1,000 hectares in different parts of the country — UP, Haryana (North); Karnataka, Telangana, Tamil Nadu (South); Rajasthan, Gujarat (West); Odisha (East); Meghalaya (North-East); (3) abatement of pollution — water conservation and artificial recharge, reducing groundwater pollution, construction of arsenic-free wells in selected areas; (4) mass awareness through social media, radio, TV, print media, posters and essay-writing competitions in schools. Designed to provide livelihood and food security through water security (NCERT Box, p. 51).

2.2 Definitions to memorise

2.3 Diagrams / processes to remember

• Fig. 4.1 — India: River Basins (p. 43): shows West-Flowing rivers (Indus Basin, Mahi, Sabarmati, Narmada, Tapi; Group 1 — rivers in Kuchchh, Saurashtra and Luni; Group 2 — rivers south of Tapi) and East-Flowing rivers (Ganga, Brahmaputra, Barak, Mahanadi, Brahmani-Baitarni, Godavari, Krishna, Pennar, Kaveri; Group 1 between Mahanadi and Pennar; Group 2 between Pennar and Kanniyakumari).
• Fig. 4.2 — The Ganga and its tributaries and towns located on them (p. 45): marks Delhi (Yamuna — Poor Quality), Prayagraj, Varanasi, and the downstream stretch in Bihar/West Bengal (Poor Quality); identifies the hilly upper stretch as Good Quality.
• Fig. 4.3 — Various Methods of Rainwater Harvesting (p. 49): four panels — (i) Watershed Management using stone wall + check dam; (ii) Lakes (Eris) — village settlements around a harvested lake; (iii) Service Wells — rooftop collection through brick filter into a service well; (iv) Recharge Wells — rooftop collection through sand filter and collection tank into a recharge well.
• Process — Water budget: precipitation (4,000 cu km) → surface flow + replenishable groundwater (1,869 cu km) → 60% beneficial use → utilisable resource (1,122 cu km). Of the 1,869 cu km of surface flow, only 690 cu km (32%) is actually utilisable (p. 41–42).
• Process — Ralegan Siddhi transformation (1975 onward): village in poverty + illicit liquor → retired army personnel arrives → percolation tank + voluntary labour → seven wells swell → ban on water-intensive sugarcane → pulses/oilseeds promoted → Tarun Mandal + Nyay Panchayats → social cohesion + agricultural prosperity (Case Study, p. 48).

2.5 Key data table (NCERT figures from this chapter)

2.4 Common confusions / NTA trap points

• Students confuse "total water from precipitation" (4,000 cu km), "surface + replenishable groundwater" (1,869 cu km) and "utilisable water" (1,122 cu km). NTA likes to swap these figures.
• Also confuse utilisable surface water (690 cu km, 32%) with the total utilisable resource (1,122 cu km, 60% of 1,869) — two different numerators.
• The 89% / 92% trap: 89% is agriculture's share of surface water; 92% is agriculture's share of groundwater. Domestic share is 9% in surface but lower in groundwater.
• Industry's share — 2% surface / 5% groundwater — students often invert.
• Groundwater development trap: very high in Punjab, Haryana, Rajasthan, Tamil Nadu (over-exploited); moderate in Gujarat, UP, Bihar, Tripura, Maharashtra; low in Chhattisgarh, Odisha, Kerala — NTA often asks "low-utilisation" states.
• 60% of total surface water resources come from Ganga + Brahmaputra + Barak even though they cover only one-third of the country's area — students invert this.
• Yamuna (Delhi to Etawah) is the most polluted river; Ganga is polluted only at Kanpur and Varanasi stretches — students wrongly mark Ganga as "most polluted river".
• Tanka/Kund is in Rajasthan, Johad is from Alwar (Rajasthan, Arvary Pani Sansad), Eris is from Tamil Nadu, Neeru-Meeru is Andhra Pradesh — geographic tagging is a frequent trap.
• Ralegan Siddhi is in Ahmadnagar district, Maharashtra — not Pune, Aurangabad or any other district.
• PMKSY launch year is 2015–16, same year as Jal Kranti Abhiyan; do not confuse the two — PMKSY is irrigation-focussed ("Har khet ko pani / Per drop more crop"), Jal Kranti Abhiyan is village-stress focussed ("Jal Gram").
• Atal Bhujal Yojana — 8,220 GPs, 229 blocks, 80 districts, 7 states — the seven states are Gujarat, Haryana, Karnataka, Madhya Pradesh, Maharashtra, Rajasthan and Uttar Pradesh (note: Punjab is NOT in this list, despite being heavily over-exploited).
• The Brahmaputra and Ganga basins are largely UNHARNESSED, whereas the Godavari, Krishna and Kaveri have been harnessed — students often reverse this NCERT statement.
• Fluoride and arsenic contamination patterns — fluoride in groundwater in Rajasthan and Maharashtra (over-withdrawal); arsenic in parts of West Bengal and Bihar — do not swap the regions.
• CPCB monitors 507 stations — not 50 or 5,070; the main source of river pollution is organic and bacterial contamination, not industrial.