Maarg Manthan · Topic 11.2

Sources and Causes of Water Pollution

Environment & Ecology › Water Resources and Water Pollution · Topic 11.2

Water pollution is the contamination of water bodies by substances or conditions that make water unfit for its intended use and harm living things. Sources are grouped as point sources, which discharge through an identifiable pipe or drain, such as sewage outfalls and factory effluent, and non-point sources, which are diffuse, such as runoff from farms and cities. Major causes are untreated or partly treated domestic sewage, industrial effluent from tanneries, textile, paper, distilleries, chemicals and metal works, agricultural runoff carrying fertilisers and pesticides, urban storm runoff, mining and its acid drainage, thermal discharge from power plants, oil spills and shipping, solid waste and plastics, religious and social practices such as immersion of idols, and sediment from erosion. India generates far more sewage than it treats, so rivers like the Ganga, Yamuna and many urban lakes are heavily polluted. The Water (Prevention and Control of Pollution) Act, 1974 and the Central Pollution Control Board address it.

5 min read · UPSC Prelims · Environment & Ecology · Water Resources and Water Pollution

At a Glance

Point source Pipe or drain
Non-point source Diffuse runoff
Biggest source Domestic sewage
Law Water Act, 1974
Body CPCB
Exam link UPSC Prelims, Environment & Ecology: Water Resources and Water Pollution

Where Does It Fit?

This topic follows the account of water resources and describes how that water is contaminated. It leads to the measures of pollution, its effects, eutrophication and specific contaminants such as arsenic and mercury. Previous topic: Surface Water Resources and Groundwater Resources. Next topic: Measurement of Water Pollution.

What Are the Main Sources of Water Pollution?

Source	Pollutants and examples
Domestic sewage	Organic matter, pathogens, nutrients, detergents; untreated sewage from towns enters rivers like the Ganga and Yamuna
Industrial effluent	Heavy metals, acids, dyes, oils and toxic chemicals from tanneries, textile, paper and pulp, distilleries and chemical works
Agricultural runoff	Fertilisers, pesticides and animal waste; a main non-point source
Urban runoff	Oil, grease, litter and metals washed from roads and roofs
Mining	Acid mine drainage, heavy metals and sediment
Thermal discharge	Hot water from power plants lowers oxygen and harms aquatic life
Oil and shipping	Spills, ballast water and discharge from ports

What Other Causes and Controls Matter?

Solid waste and plastics: dumping of garbage and plastics in drains and rivers
Religious practices: idol immersion, flowers, ash and offerings
Sand mining and erosion: raise sediment load and muddiness
Groundwater pollution: leaching from landfills, septic tanks, fertilisers and industrial lagoons
Natural sources: fluoride and arsenic from rocks, salinity from sea water
Legal control: Water Act 1974, Water Cess Act 1977, Environment Protection Act 1986
Treatment: sewage treatment plants and effluent treatment plants
Namami Gange: a programme begun in 2014 to clean the Ganga

What Else Should You Remember?

Point source: easy to identify and regulate, such as a drain outlet or factory pipe
Non-point source: hard to trace and control, such as runoff over many fields
Pathogens: bacteria, viruses and protozoa from human and animal waste cause cholera, typhoid and dysentery
Organic pollutants: use up oxygen as they decay
Inorganic pollutants: acids, salts, metals
Nutrients: nitrogen and phosphorus cause eutrophication
Toxic organic chemicals: pesticides, PCBs and dioxins
Heavy metals: lead, mercury, cadmium, chromium and arsenic
Sediments: the largest by weight and reduce light and clog gills
Radioactive substances: from mining, nuclear power and hospitals
Thermal pollution: changes temperature and oxygen
Sewage treatment gap: CPCB surveys show that treatment capacity in Indian cities is well below sewage generation, and many plants run below capacity
Common effluent treatment plants: shared plants for clusters of small units
Zero liquid discharge: a rule for some industries to recycle all waste water
Polluted river stretches: CPCB identifies river stretches that fail water quality criteria
Water Act 1974: created the CPCB and State Pollution Control Boards
CPCB: Central Pollution Control Board, a statutory body set up in 1974
Polluter pays principle: those who pollute bear the cost of cleaning
NGT: National Green Tribunal hears cases on river pollution
Ganga pollution: sewage, industrial waste and cremation and religious practices affect the river
Yamuna in Delhi: heavily polluted stretch due to sewage and drains
Link to previous: see Surface Water Resources and Groundwater Resources
Link to next: see Measurement of Water Pollution
Link to eutrophication: see Algal Bloom and Eutrophication
Caution: sewage generation and treatment figures change with each CPCB survey, so check the latest
Exam hint: classify sources as point and non-point and link each with a law or control
Oil spills: tanker accidents, ship washing and port leaks spread oil that coats water surfaces and shores
Mine drainage: water draining from coal and sulphide mines turns acidic and carries iron and metals into streams
Septic tanks and soak pits: poorly built tanks and latrine pits near wells can seep into groundwater
Detergents and household chemicals: phosphates from detergents add to nutrient pollution
Hospital and pharmaceutical waste: antibiotics and chemicals in waste water pose emerging risks
Illegal discharge: night-time release of untreated effluent by some factories is hard to detect

Why Does It Matter for the Exam?

Largest source: Domestic sewage
Hard to control: Non-point
Law: 1974 Act
Current affairs link: Namami Gange
Common errors: calling farm runoff a point source

As an analytical point, India’s rivers are polluted mostly by cities, whose sewage treatment lags demand, and by diffuse farm runoff that rules cannot easily reach. Tackling both needs sewerage, reuse of treated water and cleaner farming.

Why Is This Topic Important?

Biggest Sewage
Hard Runoff
Rule 1974 Act

What Came Next?

The next topic covers the measurement of water pollution. Next topic: Measurement of Water Pollution.

Key People and Terms

Point source Identifiable outlet
Non-point source Diffuse source
Effluent Liquid waste
CPCB Central Pollution Control Board
ETP Effluent treatment plant
STP Sewage treatment plant

Exam Corner

Points to Remember

Point source: pipe.
Non-point: runoff.
Water Act: 1974.
CPCB set up in 1974.
Namami Gange: 2014.

Do Not Confuse With

Point and non-point sources Single outlet versus diffuse
CPCB and SPCB Central versus state boards
Sewage and effluent Domestic versus industrial waste

Memory Hook

Sewage, factory, field and drain, point or spread, rivers pay.

Mains Angle

Questions ask for sources and law. These points help.

Sources Point, non-point
Law 1974
Fix Treatment

A Question You May Face

An original practice question, not a past paper question.

“Discuss the sources and causes of water pollution in India and the legal and institutional measures to control it.”

How to Answer

Sources Point, non-point.
Causes Sewage, industry.
Law 1974.
Way Treatment.

GS Relevance

Prelims: point and non-point sources, law. GS Paper 3: water pollution and its control.

Frequently Asked Questions

What are the main sources of water pollution?

The main sources are domestic sewage, industrial effluent, agricultural runoff with fertilisers and pesticides, urban runoff, mining waste and acid drainage, thermal discharge from power plants, oil spills and shipping, solid waste and plastics, and some religious practices. Natural sources such as fluoride and arsenic from rocks also contaminate groundwater.

What is the difference between point and non-point sources?

Point sources discharge pollutants through an identifiable outlet such as a sewer or factory pipe and can be monitored and regulated. Non-point sources are diffuse, with pollutants washed over large areas, for example farm fertiliser and pesticide runoff or urban street runoff, and are much harder to measure and control.

Which law deals with water pollution in India?

The Water (Prevention and Control of Pollution) Act, 1974 is the main law. It created the Central Pollution Control Board and State Pollution Control Boards, which set standards, give consent to industries to discharge effluent and can take action against polluters. The Water Cess Act 1977 and Environment Protection Act 1986 add to it.

Why is untreated sewage a major problem in India?

Indian cities generate much more sewage than their treatment capacity can handle, and many treatment plants run below capacity. Untreated sewage carries pathogens, organic matter and nutrients to rivers and lakes, spreading disease, lowering oxygen and damaging aquatic life, and it is the largest source of river pollution.

What is the polluter pays principle?

The polluter pays principle holds that those who cause pollution should bear the cost of preventing, controlling and repairing the damage. Indian courts have applied it, along with the precautionary principle, in environmental cases, and it underlies fines, compensation and clean-up orders issued against polluting industries.

PYQ Practice — Statement Analysis

1 Domestic sewage is a major source of water pollution.

True

Especially in cities.

2 Agricultural runoff is a point source.

False

It is a non-point source.

3 The Water Act was passed in 1974.