The Most Polluted River in India Is Not the Ganga or Yamuna

The most polluted river in India today is not the Ganga or the Yamuna, as many might assume — it is the Cooum River, a severely contaminated waterway that winds through the southern metropolis of Chennai.

For decades, the Ganga and Yamuna have dominated headlines around river pollution. Yet the country’s most toxic stretch of water now flows quietly through Tamil Nadu, its condition emblematic of a nationwide crisis.

Rivers across India, lifelines for millions, are choking under unprecedented levels of contamination. Their decline threatens public health, destroys fisheries, jeopardises agriculture and destabilises fragile ecosystems. For the poorest communities, who rely most heavily on rivers for daily survival, the consequences are devastating.

According to the latest assessment by the Central Pollution Control Board (CPCB), 46% of India’s rivers are now considered polluted. Its 2022-2023 review found that 296 river stretches failed to meet safe water-quality criteria — a slight improvement from 351 polluted stretches in 2018, but still an alarming indicator of the scale of India’s water crisis.

Where India’s Most Polluted Rivers Flow

India measures water pollution largely through Biochemical Oxygen Demand (BOD), an indicator of organic contamination. Water becomes unsafe for bathing when BOD exceeds 3 mg/L. But several river stretches record BOD levels above 30 mg/L—classified as Priority I, the most polluted category.

These Priority I stretches span 14 states, including Assam, Delhi, Gujarat, Haryana, Himachal Pradesh, Karnataka, Madhya Pradesh, Maharashtra, Meghalaya, Punjab, Tamil Nadu, Uttar Pradesh, Uttarakhand and West Bengal.

Some of the country’s most industrialised corridors fall within these zones, from the Yamuna in Delhi to the Sabarmati in Ahmedabad and the Sutlej in Punjab.

Pollution sources remain depressingly consistent: untreated municipal sewage, toxic industrial discharges, agricultural runoff and rampant dumping of solid waste.

Almost 40 million L of wastewater enter India’s water bodies each day. DevelopmentAid estimates that 90% of sewage is discharged without any treatment, while industries contribute 300-400 million tonnes of waste annually.

Which Is the Most Polluted River in India?

The Cooum’s stretch between Avadi and Sathyanagar in Tamil Nadu now holds the grim distinction of being the most polluted river in India, with BOD levels soaring beyond 345 mg/L, according to Central Pollution Control Board.

The 72-km-long river, once celebrated as the “Thames of South India,” is now suffocated by industrial discharge, domestic sewage and mountains of solid waste. It flows through some of Chennai’s most densely populated zones before meeting the Bay of Bengal — carrying with it a toxic load accumulated from decades of neglect.

Untreated Sewage Plagues Cooum

Instances of illegal dumping persist. In March 2024, residents reported witnessing a private tanker emptying untreated sewage from Mogappair bridge. A year later, little had changed. With sewer lines disconnected from treatment plants, entire neighbourhoods — including Rail Nagar with its 2,000 residents — were allegedly releasing sewage directly into the river.

Locals told The Times of India the situation had become “unbearable,” particularly during the monsoon season when contaminated water spills onto roads and stagnates for days.

New Sewage Treatment Plants and Infiltration Systems

Efforts by the Chennai Rivers Restoration Trust and Chennai Metro Water Supply and Sewerage Board have struggled to keep pace with the scale of pollution. While new sewage treatment plants and infiltration systems are under development, experts warn that temporary fixes — such as laying sewer lines over the riverbed — could worsen leakage risks.

According to ecological platform Ecohubmap, specialists argue that strengthening Chennai’s existing sewage infrastructure must take precedence if the Cooum is ever to recover.

River Pollution Threatens Sabarmati

In Gujarat, the Sabarmati — Ahmedabad’s historic lifeline — is now India’s second most polluted river, with the stretch between Raysan and Vautha recording BOD levels of 292 mg/L.

This pollution is driven by dense clusters of textile, chemical and pharmaceutical industries. Recent studies show high concentrations of antibiotics in the water, threatening aquatic life and raising concerns about antimicrobial resistance.

Authorities have cracked down, severing drainage connections to 393 industrial units in 2022 for illegal waste dumping. In June 2025, a massive cleanup mobilised over 90,000 volunteers and removed 945 metric tonnes of waste — the river’s most significant cleaning effort in six years. Yet, the deeper causes remain unaddressed.

Is Yamuna More Polluted Than Ganga?

Both rivers remain heavily polluted, but CPCB categorises all assessed stretches of the Yamuna as Priority I, making it one of the country’s worst-performing major rivers. The Ganga, by comparison, falls under Priority IV or V across most locations.

In 2024–25, faecal coliform levels in the Yamuna skyrocketed to 4.9 million mpn (most probable number) per 100 mL, far exceeding safe limits. Officials removed 1,300 tonnes of waste in March 2025, but by November, toxic foam — caused by detergents and industrial chemicals — had returned with force.

Environmental activist Vimlendu Jha warns that the foam is a symptom of deeper contamination. “[Defoamers] simply remove the foam, giving the impression that the river is cleaner […] The river is completely dead,” he says. “CPCB data classifies Yamuna’s water quality as E class — unfit even for animal bathing, fit only for industrial cooling.”

A new study by The Energy and Resources Institute (TERI) on microplastics prompted India’s Environment Minister Manjinder Singh Sirsa to call for a multi-pronged strategy involving sewage treatment, industrial regulation, solid waste management and public awareness.

“The findings shared by TERI give us a roadmap to tackle microplastics, frothing and other pollutants,” Sirsa told local media.

Yet, Delhi lacks facilities to treat the high levels of surfactants entering the Yamuna daily. Officials say, “It will take a long time to control surfactants unless there is a determined limit for surfactant levels.”

No Silver Bullet For Water Pollution in India

The central government’s three-year plan to clean the Yamuna has sparked scepticism. Shailendra Yashwant, senior advisor to Climate Action Network South Asia, argues that focusing on cleaning rather than preventing pollution is flawed.

“As long as the focus remains on cleaning the river and not stopping the pollution, it is not possible to clean up the Yamuna,” says Yashwant.

He adds that unplanned development along riverbanks, rampant sandmining and weak enforcement make restoration nearly impossible. “Industries that were shut down because they were polluting the river have been allowed to reopen […] despite being illegal.”

The Ganga fares no better. In West Bengal alone, the National Green Tribunal found 258.67 million L of untreated sewage flowing daily into the river in 2024. During the 2025 Kumbh Mela — a religious gathering that attracted over 660 million visitors — despite extensive preparations, several stretches still recorded unsafe BOD and faecal coliform levels.

Even large-scale cleanups — such as the 3,500 kg of waste removed from Patna ghats in October 2025 under Namami Gange — barely scratch the surface. Despite more than USD 2.6 billion spent on Ganga and Yamuna cleanups since 1993, meaningful recovery remains elusive.

India Is Running Out of Time To Save its Highly Polluted Rivers

India’s polluted rivers are not merely an ecological tragedy — they are an unfolding public health emergency and a stark indictment of decades of mismanagement.

From the Cooum to the Ganga, each polluted stretch tells the same story: fragmented policies, inadequate sewage treatment, unchecked industrial discharge and enforcement systems stretched far beyond capacity.

Cleaning rivers is no longer enough. India must prevent pollution at its source, overhaul wastewater infrastructure, enforce environmental regulations and restore natural river flows that have been crippled by dams and urban sprawl.

Without swift, systemic action, the country risks not only losing some of its most sacred and historic waterways, but also jeopardising the health, livelihoods and future of millions who rely on them every single day.