Major River Systems in India: Origins, Ecological Functions and Climate Threats

India is truly a country of rivers. These rivers have been home to civilisations, shaped the land and kept hundreds of millions of people alive for thousands of years. India's river network stretches over 3.4 million kilometres and drains more than 3 million square kilometres of land. Rivers here fall into two broad groups, the Himalayan rivers and the Peninsular rivers. Both groups are quite different from each other in how they are formed, where they come from and what they do.

Table of Contents

• The Himalayan River Systems
• The Peninsular River Systems
• Ecological Functions
• Climate Challenges

The Himalayan River Systems

The Himalayan rivers, the Indus, Ganga and Brahmaputra, never run dry. They get their water from two sources: the rains brought by the monsoon and the ice that melts from the Himalayan glaciers. The Ganga starts its journey from the Gangotri Glacier in Uttarakhand, at a height of about 3,900 metres. It travels more than 2,500 kilometres before finally meeting the Bay of Bengal at the Sundarbans delta, which it shares with the Brahmaputra.

The Brahmaputra begins far away, at the Angsi Glacier in Tibet. It enters India through Arunachal Pradesh, flows across Assam and then joins the Ganga in Bangladesh. In Tibet, it is called the Yarlung Tsangpo. It carries one of the largest volumes of water of any river in the world. The Indus starts near Lake Mansarovar in Tibet, passes through Ladakh and eventually empties into the Arabian Sea in Pakistan.

The Ganga has several important tributaries, the Yamuna, Ghaghra, Gandak, Kosi, Son and Chambal among them. Together, these rivers form a wide network that keeps the Indo-Gangetic Plain alive. This plain is one of the most fertile farming regions in the world and one of the most densely populated too.

The Peninsular River Systems

Peninsular rivers are very different from the Himalayan ones. They depend almost entirely on rainfall, which means they can dry up during the summer. Most of them rise from either the Western Ghats or the Eastern Ghats. The Western Ghats act like a wall that divides rivers, some flow west toward the Arabian Sea, like the Narmada, Tapi, Periyar and Mandovi. Others flow east toward the Bay of Bengal, like the Mahanadi, Godavari, Krishna, Cauvery and Tungabhadra.

The Godavari is often called the 'Dakshin Ganga', meaning the Ganga of the South. At around 1,465 kilometres, it is the second-longest river in India. It starts near Trimbakeshwar in Maharashtra. The Krishna River begins at Mahabaleshwar in the Western Ghats and travels 1,400 kilometres through Maharashtra, Karnataka and Andhra Pradesh. The Cauvery flows from Talakaveri in Karnataka and has been central to farming life in both Karnataka and Tamil Nadu for centuries.

Ecological Functions

Rivers do so much more than just carry water from one place to another. They are the backbone of India’s farming economy. Nearly 70% of India's farmland gets its water, directly or indirectly, from rivers through irrigation. Rivers also refill underground water reserves, keep the soil moist and make floodplains rich and productive.

River ecosystems are home to some extraordinary and rare creatures, the Gangetic river dolphin, the gharial, freshwater turtles and hundreds of fish species. The wetlands and floodplains along river banks are vital resting and nesting places for migratory birds. The Sundarbans delta, formed where the Ganga and Brahmaputra meet the sea, is the largest mangrove forest in the world and a UNESCO World Heritage Site.

Rivers like the Ganga and Yamuna also hold deep spiritual meaning for hundreds of millions of Hindus. They support pilgrimages, fishing communities and religious traditions that have been part of Indian life for thousands of years.

Climate Challenges

India's rivers are under serious stress because of climate change. The Himalayan glaciers that feed perennial rivers are shrinking fast. Research suggests that if carbon emissions stay high, these glaciers could lose up to 65% of their mass by 2100. When that happens, rivers like the Ganga and Brahmaputra will carry far less water in the dry season, putting hundreds of millions of people at risk.

Monsoon patterns are also changing. Heavy rains are hitting harder and more suddenly, while dry spells are lasting longer. Flash floods are becoming more destructive in river catchment areas, damaging farms, roads and homes. At the same time, Peninsular rivers are running lower than before during droughts, which is making old disputes worse, like the long-running disagreement between Karnataka and Tamil Nadu over the Cauvery River.

On top of climate change, pollution is a massive problem. Factory waste, untreated sewage, farm chemicals and plastic have badly damaged water quality across many rivers. The government launched the National Mission for Clean Ganga (NMCG) and the Namami Gange Programme to try to bring the Ganga back to health, but the results have been mixed so far.