The Ganges River runs through northern India and is sacred to those who follow Hinduism. Hindus refer to it as the Ganga or Ganga Ma, which means Mother Ganga. More than 400 million people in India live in the area that feeds the river, known as the Ganges River Basin. A river basin is a region that is drained by a river, such as the Ganges, and any of its tributaries. This means that surface water and rainwater in the basin area flow into the nearby rivers.

The Ganges River originates in the Himalaya Mountains at Gomukh, the terminus of the Gangotri Glacier. When the ice from this glacier melts, it forms the clear waters of the Bhagirathi River. As the Bhagirathi River flows down the Himalayas, it joins the Alaknanda River, officially forming the Ganges River. As the river empties into the Bay of Bengal, the mouth forms the Ganges River Delta, the largest river delta in the world.

The Ganges River Basin is sometimes considered part of a larger river basin consisting of the nearby Brahmaputra and Meghna rivers. Known as the Ganges-Brahmaputra-Meghna (GBM) River Basin, it is one of the largest river systems in the world.

The melting water from the Himalayas, as well as water from tributaries and rainfall, all feed the river. The Ganges River flows south and east from the Himalayas, forming a canyon as it leaves the mountain. It winds its way through northern India, eventually emptying into the Bay of Bengal. The river’s many tributaries originate from the nearby countries of Nepal, Bangladesh and China (in an autonomous region called Tibet).

The Ganges River carries nutrient-rich sediment as it flows, depositing fertile soil along its shores. It supports a vast assortment of plants and wildlife. The endangered Ganges River dolphin (Platanista gangetica), the National Aquatic Animal of India, lives only in this river system, which also teems with a diverse array of native freshwater fish, including carp, catfish and mahseer. These natural resources have allowed civilizations to develop and thrive along the waterway for centuries. Hindus make pilgrimages to the river and perform ritual baths to wash away sin. Cremation ceremonies are also performed on the banks of the river, and the ashes are sometimes placed in the river as well. A Hindu goddess named Ganga is a sacred personification of the river, and Hindus consider the river to be alive. While it is not part of their religious traditions, a survey by the Pew Research Center showed that some local people of other faiths, such as Christians and Muslims, also believe that the Ganges can spiritually purify people.

Today, the river flows through well-populated regions of India, providing freshwater to the millions of people living in these regions. The river is also used for fishing, irrigation and bathing. Muslims and other non-Hindus also use the river for these same purposes, but there is tension between them and the Hindu population. Although Muslims and other Indians have rights to equal access, there have been instances where Hindus have attempted to stop Muslims from accessing the river, resulting in police and government investigations.

The Ganges River is a vital resource to Asia, but it faces many threats. Human and industrial pollutants fill the river in some areas, making it unsafe even for swimming. Experts estimate that 3 million liters (0.8 million gallons) of sewage are dumped into the river every day. Even more pollutants come from local industries like textile plants, which add toxic chemicals to the water, and water runoff from farms using pesticides. Even seemingly benign activities have increased the river’s pollution. For example, Hindus place flowers in the river as part of their religious practice. But because the flowers have been treated with chemicals to make them stay fresh for longer, and because of the volume of the flowers being used, they end up being a surprisingly significant source of pollution. The negative effect on the habitat threatens wildlife. The Ganges River dolphin, for example, is endangered and is entirely absent from significant portions of its former range.

Political and social factors are putting pressure on the Ganges River as well. As the population in regions surrounding the river swells, water demands for agriculture increases, straining water levels. This has contributed to ongoing tension between India, a primarily Hindu country, and Bangladesh, a mostly Muslim country, which share access to the Ganges along their border. In 1975, India built the Farakka Barrage, a dam that diverted water to India and away from Bangladesh. This caused rivers to dry up, damaged wetlands and increased salinity levels in the soil and freshwater sources, contributing to severe drought conditions in Bangladesh. The ecological imbalance also harmed the Sundarbans, the world’s largest mangrove forest and a UNESCO World Heritage Site. Though an agreement made in 1996 was intended to balance the water use between the two countries, researchers found that India denied Bangladesh its share of water during times of high demand.

Adding further stress to the situation, scientists say that climate change will increase stress on the Ganges. They have concluded that climate change has led to a decrease in glacial ice in the Himalayas, the source of the Ganges. Scientists predict that the amount of glacial ice runoff in the river will decrease significantly by the end of the 21st century and that the river will instead be filled by runoff, changing the composition and habitat of the river. Additionally, the river will experience more extreme and unpredictable periods of flooding and drought. Monsoons are exacerbated by climate change, so during the rainy season, more areas of the river basin will become flooded, posing a threat to the people and animals that live there, as well as to agriculture, fishing and industry. Scientists also expect the natural dry season to become even drier as rising temperatures from climate change lead to longer and more intense droughts. The people who are most vulnerable to the effects of climate change are people who work in fishing, agriculture and other industries that rely on nature, and people in marginalized groups and communities, such as those with disabilities. Experts predict that these conditions would force people to leave their homes. A 2018 report by the World Bank projects 40 million climate migrants in South Asia by 2050 unless these issues are addressed.

A number of initiatives are underway to address the many challenges facing the Ganges River Basin. Thousands of devotional flowers offered at temples along the Ganges, which once were simply discarded into the river, are now being collected and recycled through grassroots efforts. Volunteers gather these flowers from riverbanks and temples, and transform them into incense sticks, paper and natural colors used during festivals like Holi. The Indian government also has taken steps to conserve the Ganges River, but some critics argue that stronger action is needed. International organizations, such as the World Bank, have also invested in projects to clean up the Ganges. Still, greater efforts will need to be made in coming years to address years of neglect and counter the negative impacts of climate change.