Researchers are sounding the alarm, pointing out that one of India's most massive engineering projects could unintentionally trigger an ecological disaster across the country. The National River Linking Project (NRLP), conceived to address water scarcity by connecting surplus rivers with deficit ones, potentially risks the spread of invasive alien species.
According to a new study, these artificial waterways threaten to bypass ancient natural barriers, allowing aggressive non-native plants, fish, and animals to colonize and potentially destroy some of the planet's most diverse freshwater ecosystems.
Scientists from Ashoka Trust for Research in Ecology and the Environment (ATREE) and Yenepoya (Deemed to be University) studied how the proposed network of 15,000 kilometers of canals and 3,000 reservoirs will alter India's biological landscape. They found that areas the government intends to protect, such as biodiversity hotspots including Krishna, Godavari, and the Western Ghats, are most vulnerable to these biological invasions. By connecting these basins, the project could facilitate the migration of 15 known invasive species into previously isolated habitats.
Among the 15 studied invasive species are various plants, such as water hyacinth and water lettuce; fish, like the African catfish, common carp, guppy, and sucker catfish; mollusks, including the sharp-shelled snail; and one reptile, the red-eared slider turtle. Researchers applied a species distribution modeling method. They mapped the current locations of 15 naturalized invasive species and used climate data to predict their survival sites if movement were possible. When overlaying these suitability maps onto the proposed river linking project routes, the results showed a significant overlap. A strong positive correlation was identified, meaning that river basins rich in native species are also the most attractive environments for invaders. Thus, India's most valuable biodiversity hotspots, instead of being resistant to newcomers, actually represent invasion foci ready to occur.
The study highlights a gap in policy and provides an accurate assessment of the biological cost of connectivity. Unlike earlier works warning of human displacement or forest loss, this research presents the first spatially detailed framework of how biotic homogenization—the process of unique local species being replaced by the same few widespread invaders—could develop across the subcontinent. These findings serve as a warning signal for the future health of India's environment and the well-being of its population. Freshwater ecosystems cover less than 3% of the Earth's surface but support 10% of all known species, yet they are disappearing three times faster than forests. For a country like India, where millions depend on healthy rivers for food security, clean water, and livelihoods through inland fishing, the loss of native species can have enormous socio-economic impacts. Invasive species, such as Mozambique tilapia, can rapidly displace native fish species, leading to the collapse of traditional fishing industries and a decline in water quality.
The study emphasizes the need for ecological foresight. Researchers argue that the benefits of the National River Linking Project, such as improved irrigation and hydroelectric power, cannot be realized if the basic ecosystems are destroyed. India has the opportunity to become a leader in sustainable development by integrating invasion ecology at the initial stages of national infrastructure planning. In conclusion, the study concludes that protecting the unique biological identity of India's rivers is crucial for long-term sustainability, ensuring that the country's water systems continue to support both nature and people amidst a rapidly changing climate.
Mahatma Gandhi once observed: 'Nature provides enough to satisfy every man's needs, but not every man's greed.' These words are particularly relevant today along the rivers of India.
From Delhi to Mumbai, from Chennai to Hyderabad and Bangalore, the urban rivers of India exhibit similar problems. They have been narrowed, embanked, and then converted into channels for waste generated in rapidly growing cities. Rivers that once shaped settlements are now forced to exist by carrying sewage.
However, each river faces unique challenges. The Yamuna has lost a significant portion of its width due to floodplain encroachment and water diversion. A recent study showed that this river, which flows through northern and southern parts of the capital and is also known as the Kalindi, has shrunk by almost 68% over the last 220 years.
While the Yamuna struggles, the Sahibi River in the national capital has crossed a critical threshold and is in an ecologically degraded state, according to a report by the Central Water Committee of the Jal Shakti Ministry. Once an important seasonal river flowing through West Delhi, the Sahibi has gradually disappeared under the pressure of urban expansion. Today, most residents know it simply as the Najafgarh or Nala drain—a heavily polluted waterway carrying black sewage through the city.
Meanwhile, the Mithi River in Mumbai has turned into a stormwater drain overloaded by uncontrolled urban development. The Musi in Hyderabad and the Cooum in Chennai now carry far more sewage than fresh water, and the Vrishabhavathi in Bangalore has effectively become a municipal sewage channel.
Even the mighty Brahmaputra in the Northeast, which is relatively cleaner than most urban rivers, is steadily losing land due to constant erosion amid increasing climate change and urban pressure. Together, they reveal a common truth: Indian cities have grown at the expense of the space available to rivers.
No river illustrates this transformation as dramatically as the Yamuna. Researchers from Delhi University and the Indian Institute of Science Education and Research (IISER), Bhopal, found that the average width of the Yamuna in Delhi has shrunk by almost 68%: from approximately 658 meters in 1799 to about 210 meters today. Water flow has dropped by nearly 90%, mainly due to dams, canals, and water diversion projects.
Researchers also argue that the loss of floodplains has made Delhi more vulnerable to flooding. Embankments have restricted the river to an increasingly narrow channel, which helps explain why the capital experienced record floods in 2023 despite lower river flow than during the 1978 floods. The Yamuna has long held a central place in Delhi's political discourse. Every election brings new promises to clean the river, while opposition parties accuse each other of worsening its condition.
Despite repeated assurances, the river remains heavily polluted and is often described as being on the brink of biological death. Its condition cannot be ignored. Passing through Delhi, the Yamuna carries dark, contaminated water clogged with untreated waste. Downstream, it reaches Agra, where it flows near one of the world's greatest monuments—the Taj Mahal. The contrast between the immaculate marble monument and the foul-smelling river serves as an uncomfortable reminder of India's environmental problems.
For Mumbai, the floods of July 26, 2005, were a catastrophe, claiming over 500 lives and revealing that decades of urban expansion had reduced the Mithi River to 17.8 km. According to the Mumbai Metropolitan Region Development Authority (MMRDA), suburban development over the last 25 years has 'sharply deteriorated' the water quality in the river. Once an important natural channel for stormwater runoff, the Mithi now carries untreated sewage, industrial effluents, municipal waste, and silt.
Wetlands and floodplains have disappeared under roads, industrial zones, and the Bandra-Kurla complex. Construction has narrowed the river, reducing its capacity to handle monsoon floodwaters. Although the Municipal Corporation of Mumbai stated that expansion and retaining wall construction have doubled storage capacity and tripled throughput since 2005, officials admit that pollution remains the most serious problem. The Maharashtra Pollution Control Board identifies untreated sewage, industrial discharges, and solid waste as the main causes of the river's ongoing degradation.
The BMC and MMRDA have undertaken works to expand, deepen, remove silt, build retaining walls, and implement pollution control measures along the river. The country's largest municipal body, the BMC, reported that retaining wall construction is nearly complete, while the MMRDA is implementing a sewage interception project and a pilot odor control project aimed at improving dissolved oxygen and reducing pollution. Renewed efforts to remove silt and combat illegal land grabbing have also been reported following an alleged silt removal scandal.
The Musi perhaps tells the clearest story of a river losing its natural identity. The Telangana government's Musi Waterfront Development Corporation stated that the river now flows 'almost dry' through Hyderabad because upstream reservoirs, watershed degradation, and urban encroachment have drastically reduced natural flows. What remains is mostly sewage.
The Union Ministry of Environment classifies sections of the Musi among India's 'priority polluted river stretches,' and the Jal Shakti Ministry reported that four treatment plants with a total capacity of 593 million liters per day have been created under the National River Conservation Plan. Nevertheless, untreated sewage continues to enter the river through numerous nalas or drains as Hyderabad continues to expand and transform into a full-fledged metropolis. The state is now proposing a 55 km waterfront restoration project focused on complete sewage interception, ecological restoration, and flood management, acknowledging that beautification alone cannot revive a river whose main problem is pollution.
The story of the Cooum is no less alarming. The river, which is about 65 km long, once supported transport and recreation before being overwhelmed by Chennai's urban growth. Government data presented in parliamentary records indicates a Biochemical Oxygen Demand (BOD) level in the Cooum of 105 mg/liter—one of the highest for urban rivers in India. Healthy water bodies usually have a BOD below 3 mg/liter.
Under the National River Conservation Plan, projects worth ₹404.25 crore have created 264 million liters per day of treatment capacity through four sewage treatment plants, according to the Ministry of Environment. However, this project includes both the Cooum and the Adyar rivers. Nevertheless, untreated sewage from the Cooum continues to enter the river through numerous drains. An audit by the Comptroller and Auditor General noted that Tamil Nadu itself described the Cooum as an 'urban sewer collector due to the discharge of municipal and industrial waste.'
The Chennai River Restoration Trust has cleared encroached areas, relocated thousands of families, and restored areas near Island Grounds. But officials continue to acknowledge that preventing sewage inflow remains a key challenge.
If the Musi of Hyderabad resembles an open drain, the Vrishabhavathi of Bangalore has effectively become one. The Central Pollution Control Board describes the river as a 'drain for domestic and industrial sewage.' The river, before joining the Arkavathi after flowing into the Biramangala reservoir, carries a significant portion of Bangalore's treated and untreated sewage downstream.
The CPCB has repeatedly urged Karnataka authorities to strengthen sewage treatment, improve industrial effluent management, and protect floodplains. Heavy rains often wash garbage and plastic downstream. Residents near Bidadi complained that after every heavy rain, trucks carrying Bangalore waste accumulate around the bridges. The river illustrates how pollution generated in one city increasingly affects communities far beyond municipal boundaries.
The Brahmaputra also feeds some of the fastest-growing urban centers in the Northeast. From Dibrugarh to the bustling metropolis of Guwahati, cities have grown and continue to expand along the banks of the mighty river. Unlike India's urban rivers, the biggest problem with the Brahmaputra is not just sewage. It is erosion.
Every year, villages, agricultural lands, and public infrastructure disappear as one of the world's largest braided rivers changes its course. Recognizing the scale of the problem, the World Bank and the Asian Development Bank signed a $200 million agreement in 2024 to strengthen flood and erosion management along 650 km of the river in Assam. Assamese government documents describe erosion as one of the state's biggest development challenges. Protective works continue around vulnerable areas like Majuli, and future planning increasingly relies on satellite imagery, GIS mapping, and hydrological modeling.
Although pollution levels remain significantly lower than in India's megacities, officials warn that urbanization and untreated sewage around cities like Guwahati are becoming a growing concern. The Brahmaputra demonstrates that shrinking rivers are not always linked to pollution. Sometimes rivers lose land, and people lose homes. The relentless erosion and annual floods of the Brahmaputra continue to threaten millions in the Northeast. Fed by abundant monsoon rains, the river frequently overflows its banks, leaving large parts of the region flooded.
If the Ganges is India's most revered river, it is also one of the most stressed. Flowing through some of the country's fastest-growing cities, including Haridwar, Kanpur, Prayagraj, Varanasi, Patna, and Kolkata, the Ganges faces a different problem. Unlike the Yamuna, its main burden is industrial pollution, exacerbated by religious offerings, ritual waste, human remains, and huge crowds gathering during events like the Maha Kumbh.
Revered for centuries as 'Maa Ganga' and celebrated as a symbol of purity, the Ganges is now among the most polluted waterways in the world. The river is increasingly becoming a victim of urban expansion, pollution, and the reduction of natural floodplains. As cities grow, the Ganges' floodplains are steadily disappearing under roads, residential settlements, commercial properties, and embankment structures. These encroachments have narrowed the river's natural corridor, reducing its ability to flood during the monsoon, replenish groundwater, and sustain wetlands.
Pollution remains the river's biggest issue. Despite significant investments under the Namami Gange program, untreated sewage from expanding urban centers continues to enter the river through hundreds of drains. Industrial effluents, especially from tanneries, sugar mills, distilleries, and textile units, increase the pollution load, although regulatory enforcement has improved in recent years. During the dry season, reduced ecological flow due to dams and water diversion further limits the river's ability to dilute pollutants. Large-scale restoration efforts have expanded sewage treatment capacity, intercepted drains, and improved embankment infrastructure in several cities. Nevertheless, government assessments continue to emphasize that engineering projects alone are insufficient to revive the Ganges.
