The Ganges is India's largest river. Stretching 1,570 miles across the northern half of the country, it provides water to hundreds of millions of people.

In many cases, that's not a good thing.

October 2013 | The Ganges from Rishikesh to Uttarkashi, India. | (National Geographic Creative / Alamy Stock Photo)

The Ganges is more than a source of drinking and bathing water. To millions of Hindus across the country, Ma Ganga ("Mother Ganga") is a spiritual center. It is believed to be the physical embodiment of a beloved goddess who chose to live on Earth so she could cleanse the faithful's sins.

Worshippers travel to the banks of Ma Ganga for spiritual purification in life and death. To bathe in her waters is to be granted heavenly blessings. To die in her waters, or to have one's ashes scattered there, is to break the cycle of reincarnation and achieve eternal liberation.

July 2017 | A Hindu priest performs evening prayers on the banks of the river in Devprayag, India. | (REUTERS/Danish Siddiqui)

But decades of overuse and careless pollution have taken their toll on the sacred waters. Now the second most polluted river in the world, the Ganges is dirtier than it has ever been.

January 2013 | A Hindu pilgrim dips herself into the confluence of the Ganges and the Bay of Bengal at Sagar Island, India. | (REUTERS/Rupak De Chowdhuri)

July 2017 | A damaged idol of Hindu goddess Kali floats in the Ganges in Haridwar, India. | (REUTERS/Danish Siddiqui)

The river emerges from the snowy peaks of the Himalayas — just a few miles from India's border with Tibet — crystal clear. But as the river snakes through thousands of villages and cities on its way to the Bay of Bengal it thickens and browns.

The sacred waters have become a receptacle for personal and industrial waste. In the most densely populated areas, the water's surface is nothing more than a floating trash heap. But the uglier and more dangerous reality floats below: millions of gallons of raw sewage and toxic waste from tanneries and other local industries that are dumped into the river daily.

"Yogis and meditators devoted their morning service to worshipping Ganga, but in the afternoon were throwing their candy bar wrappers and plastic bottles into it," Cameron Conaway writes in Newsweek.

The mythology surrounding the Ganges as a source of eternal freedom only exacerbates the problem: Thousands upon thousands of bodies end up decaying beneath the surface, sometimes getting lodged on the banks in giant, rotting clumps.

July 2017 | A pile of garbage along the river in Mirzapur, India. | (REUTERS/Danish Siddiqui)

July 2017 | A portion of the river that has turned red from pollution in Kanpur, India. | (REUTERS/Danish Siddiqui)

Despite the visible signs of pollution, the river's holy status makes it immune to impurities, in the eyes of believers. "Mother Ganges cannot be polluted," is a common refrain heard around the river. Children take swim lessons, worshippers bathe, and villagers continue to drink from its cloudy waters. In some cities, people "brush their teeth next to towering mounds of rubbish," Reuters reports, or wash their faces just a few feet from lifeless bodies.

The results are devastating. Contaminated waters can cause millions of cases of water-borne disease — including dysentery and typhoid — every year. India is now among the countries with the highest number of people at risk for cholera. A 2016 study found that villages closest to the river have a concentration of water-related health hazards like skin infections and dental issues.

Prime Minister Narendra Modi has pledged $3 billion to clean the river, build more treatment facilities, and move offending businesses farther away — but the plan is severely behind schedule.

Take a closer look at the desperate state of India's holy mother:

July 2017 | Untreated foaming sewage flows from an open drain into the river in Mirzapur, India. | (REUTERS/Danish Siddiqui)

July 2017 | A man cleans garbage along the banks of the river in Kolkata, India. | (REUTERS/Danish Siddiqui)

July 2017 | Relatives immerse a body in the river prior to cremation in Varanasi, India. | (REUTERS/Danish Siddiqui)

July 2017 | An employee works inside a leather tannery near the river in Kanpur, India, in July 2017. | (REUTERS/Danish Siddiqui)

July 2017 | Chemical-soaked leather pieces dry near the banks of the river. | (REUTERS/Danish Siddiqui)

July 2017 | A man washes himself in the river in Varanasi, India. | (REUTERS/Danish Siddiqui)

November 2011 | Hindu devotees gather to worship in the Ganges in Patna, India. | (REUTERS/Stringer)

July 2017 | A Hindu woman carries water from the Ganges in Kolkata, India. | (REUTERS/Danish Siddiqui)