Water Resources and Pollution
Overview
Water resources and pollution is a foundational topic in Environmental Studies for WB TET Paper I. It connects directly to a child's everyday experience—drinking water, bathing, farming, and the rivers of West Bengal—making it both relatable and examinable. The topic tests your understanding of where water comes from, how humans use it, why we must conserve it, and what happens when it gets polluted.
For the WB TET, expect questions on sources of water (surface vs groundwater), the water cycle, methods of water conservation, causes and effects of water pollution, and water-borne diseases. Pedagogy questions may ask how to teach water conservation through activities or local examples. West Bengal-specific references—Ganga, Hooghly, Sundarbans wetlands—appear frequently.
Mastering this topic also builds your ability to teach EVS as an integrated subject, linking science concepts (evaporation, filtration) with social realities (scarcity, sanitation, community practices).
Key Concepts
- Sources of water fall into two broad categories: surface water (rivers, lakes, ponds, streams) and groundwater (wells, tube wells, springs). Rainwater is the primary source that replenishes both.
- The water cycle (hydrological cycle) describes continuous movement: evaporation from water bodies → condensation into clouds → precipitation as rain/snow → collection in rivers, lakes and underground aquifers → evaporation again.
- Uses of water span domestic (drinking, cooking, bathing), agricultural (irrigation), industrial (manufacturing, cooling), and ecological (maintaining wetlands, aquatic life).
- Water scarcity arises from uneven distribution, over-extraction of groundwater, population growth, and pollution making water unfit for use.
- Water conservation means using water wisely and protecting sources. Methods include rainwater harvesting, watershed management, drip irrigation, repairing leaks, and afforestation.
- Water pollution is contamination that makes water harmful for living organisms. It can be physical (sediment, heat), chemical (pesticides, heavy metals), or biological (pathogens, sewage).
- Water-borne diseases—cholera, typhoid, jaundice, dysentery—spread when people consume or contact polluted water, a key public-health concern in rural and urban West Bengal.
- Role of community and government: Safe drinking water is a fundamental need. Jal Jeevan Mission, PHE (Public Health Engineering) schemes, and local panchayat initiatives aim to provide clean water.
Key Facts
| Fact | Detail |
|---|---|
| Earth's water distribution | About 97% is saline (oceans); only 3% is freshwater, of which roughly 68% is locked in glaciers and ice caps. |
| Groundwater share | Groundwater supplies about 85% of rural drinking water and 50% of urban water in India. |
| Safe drinking water standard | According to WHO/BIS, potable water must be free from harmful microorganisms, chemicals beyond permissible limits, and objectionable taste/odour. |
| Major rivers of West Bengal | Ganga (Hooghly), Teesta, Damodar, Ajay, Rupnarayan, Ichamati. |
| Permissible pH of drinking water | 6.5 to 8.5 (BIS standard). |
| Rainwater harvesting | Collecting and storing rainwater from rooftops or catchment areas for later use. |
| Biological Oxygen Demand (BOD) | A measure of organic pollution; higher BOD means more pollution and less oxygen for aquatic life. |
| Arsenic contamination | A serious groundwater issue in several districts of West Bengal (Murshidabad, Nadia, North 24 Parganas). |
Worked Examples
Example 1 – Identifying pollution type
Question: A factory releases hot water into a nearby river. Fish in that stretch start dying. What type of pollution is this?
Solution:
- Hot water raises the river's temperature.
- Warmer water holds less dissolved oxygen.
- Aquatic organisms suffocate due to oxygen depletion.
- This is thermal pollution (a form of physical/chemical pollution).
Example 2 – Water cycle sequence
Question: Arrange the following in correct order of the water cycle: Condensation, Precipitation, Collection, Evaporation.
Solution:
- Evaporation – water from oceans/rivers turns to vapour.
- Condensation – vapour cools and forms clouds.
- Precipitation – water falls as rain or snow.
- Collection – water gathers in rivers, lakes, or seeps underground.
Correct order: Evaporation → Condensation → Precipitation → Collection.
Example 3 – Conservation method
Question: A school in a water-scarce area wants to become self-sufficient during dry months. Suggest one method and explain briefly.
Solution:
- Rainwater harvesting is ideal.
- Install collection pipes from the school roof leading to a storage tank or recharge pit.
- During monsoon, rainwater is collected; during dry season, stored water is used for gardening, toilet flushing, or even filtered for drinking.
- Benefit: reduces dependence on external supply and teaches students conservation.
Common Mistakes
| Wrong Thinking | Correct Understanding |
|---|---|
| "All groundwater is pure and safe to drink." | Groundwater can contain arsenic, fluoride, nitrates, or microbial contamination. Testing and treatment are essential. |
| "Water pollution is only caused by factories." | Domestic sewage, agricultural runoff (fertilisers, pesticides), and improper waste disposal are equally significant sources. |
| "Boiling water removes all impurities." | Boiling kills pathogens but does not remove dissolved chemicals like arsenic or lead. Filtration or specific treatment is needed. |
| "Water cycle only involves rain and rivers." | Transpiration from plants and sublimation from ice are also part of the cycle; students often forget these. |
| "Conservation means only saving water at home." | Conservation also includes protecting catchment areas, preventing pollution, recharging aquifers, and policy measures. |
Quick Reference
- Surface water: rivers, lakes, ponds; Groundwater: wells, aquifers.
- Water cycle order: Evaporation → Condensation → Precipitation → Collection.
- 3% of Earth's water is freshwater; most is in glaciers.
- Major pollutants: sewage, industrial effluents, pesticides, thermal discharge.
- Water-borne diseases: cholera, typhoid, dysentery, jaundice.
- Conservation methods: rainwater harvesting, drip irrigation, afforestation, fixing leaks.
- Arsenic in groundwater is a critical issue in parts of West Bengal.