Water Resources
Class 12 · Geography
4 ideas in Class 12 Geography, explained in plain words, with games and quizzes to practise.
Surface and Groundwater Availability
Part of: Water Availability and Sectoral Demand
India holds only four percent of global freshwater resources despite supporting over seventeen percent of humankind. Annual rainfall yields around 4000 cubic kilometres of water, but due to terrain limits and seasonal flow surges, utilisable water totals only 1122 cubic kilometres. Of this, surface water offers 690 cubic kilometres and replenishable underground aquifers yield 432 cubic kilometres. Perennial basins like the Ganga and Brahmaputra hold the bulk of surface runoff.
Why it matters. Understanding water availability helps citizens evaluate why regions face acute thirst despite massive monsoons. It shows why storage and river basin management are essential to prevent drought.
Key words
- utilisable water
- : Volume of precipitation and runoff that can be captured and put to practical use.
- replenishable groundwater
- : Subsurface water in aquifers refilled annually by rain and surface percolation.
- brackish water
- : Slightly salty water found in coastal lagoons suitable for select crops and fishing.
- catchment area
- : The entire land basin drained by a river system and its connecting tributaries.
Try it in two minutes
- Compare India's world population share with its water resource share.
- Discuss why much of monsoon flood water flows uncaptured into the sea.
- Look at a map to see which major rivers flow through northern and southern plains.
- Explain how coastal lagoons provide water for fishing and salt-tolerant crops.
Try at home. Note down how many hours tap water runs in your area and estimate daily household intake.
Sectoral Demand and Irrigation Pressures
Part of: Water Availability and Sectoral Demand
Agriculture is the largest consumer of water in India, taking about 89 percent of surface water and 92 percent of groundwater supplies. Spatio-temporal rainfall variability and the demands of high-yielding seeds make irrigation indispensable. In northwestern states like Punjab and Haryana, over 85 percent of net sown area is irrigated, predominantly by tubewells. Heavy drawdown has lowered aquifers and concentrated hazardous elements like fluoride and arsenic in drinking water.
Why it matters. Examining sectoral water demands reveals why farming decisions shape water security. It helps learners grasp how unmanaged tubewell pumping risks desertification and toxic water contamination.
Key words
- sectoral water demand
- : Distribution of total available water among agriculture, industry and homes.
- aquifer overdraft
- : Pumping underground water faster than natural rainfall can recharge the table.
- soil salinisation
- : Accumulation of dissolved mineral salts in topsoil due to excessive irrigation.
- multiple cropping
- : Growing two or more crops sequentially on the same land parcel in one year.
Try it in two minutes
- Ask why farmers need irrigation during dry winter and hot summer months.
- Identify two high-water crops grown widely in irrigated plains.
- Discuss what happens to the water table when tubewells pump day and night.
- Explain how falling groundwater tables cause mineral poisoning in wells.
Try at home. Check whether food crops grown near your town depend on canal water, tubewells, or seasonal rains.
Water Pollution and Legislative Controls
Part of: Water Conservation and Governance
River water quality deteriorates rapidly as streams leave mountain valleys and enter densely populated plains. Sewage, agricultural runoff laden with pesticides, and untreated factory effluents enter river channels. During low-flow summer months, pollutant concentrations spike dangerously. Central and state pollution control boards monitor water health, but legislation like the Water Act 1974 requires stricter enforcement and community vigilance.
Why it matters. Learning about water degradation equips students to detect toxic discharge pathways and champion river basin cleanups. It shows that water security is about clean quality as well as total quantity.
Key words
- effluent
- : Liquid industrial discharge or municipal wastewater flowing into river channels.
- organic contamination
- : Pollution caused by sewage and decomposed biological waste carrying harmful microbes.
- Central Pollution Control Board
- : Apex statutory body responsible for tracking and regulating aquatic health across India.
- water quality
- : Measurement of water purity and suitability for living organisms and human use.
Try it in two minutes
- Trace a river from mountain source to crowded industrial plains.
- List three sources of waste that enter open drains and canals.
- Explain why river pollution worsens when water levels drop in summer.
- Discuss how reclaiming factory greywater protects drinking rivers.
Try at home. Check whether dirty wash water from your street connects to an open drain, septic tank, or sewage pipe.
Watershed Management and Rainwater Harvesting
Part of: Water Conservation and Governance
Watershed management coordinates the protection, recharge and prudent use of all water, land and biomass resources within a natural drainage basin. Simple structures like check dams, percolation tanks and rooftop collection catch rainwater before it runs away. Programs like Haryali, Neeru-Meeru in Andhra Pradesh and Arvary Pani Sansad in Rajasthan prove that people's active involvement transforms drought-prone villages into lush, secure communities.
Why it matters. Learning about watershed techniques equips future planners with decentralized water solutions. It illustrates how community action revives village wells without waiting for massive state dams.
Key words
- watershed management
- : Integrated conservation and recharge of water, soil and vegetation within a basin.
- rainwater harvesting
- : Capturing and storing rainwater runoff or channeling it into underground aquifers.
- percolation tank
- : An excavated basin built across a stream to trap runoff and recharge nearby wells.
- tanka
- : A covered underground storage cistern built in arid Rajasthan to collect roof rain.
Try it in two minutes
- Define what a watershed basin is using a sloping bowl shape.
- Identify two traditional recharge structures like ponds and percolation tanks.
- Discuss how Ralegan Siddhi transformed its economy using voluntary labour.
- Explain why rooftop rainwater harvesting is compulsory in Tamil Nadu.
Try at home. Inspect your roof or school building to locate where rainwater gutters drain.
What your child will practise
- Sectoral Demand and Irrigation Pressures: Jungle Quick Fire (Quick Fire)
- Surface and Groundwater Availability: Candy Quick Fire (Quick Fire)
- Surface and Groundwater Availability: Space Puzzle (Clue Puzzle)
- Water Pollution and Legislative Controls: Desert Quick Fire (Quick Fire)
- Watershed Management and Rainwater Harvesting: Jungle Puzzle (Clue Puzzle)
- Quiz: Sectoral Demand and Irrigation Pressures (8 questions)
- Quiz: Surface and Groundwater Availability (8 questions)
- Quiz: Water Pollution and Legislative Controls (8 questions)
- Quiz: Watershed Management and Rainwater Harvesting (8 questions)