But Mother Ganga has become very sick.

"When I was a boy of five, I used to drink the water, it was so pure. After a few years, I saw it getting dirty. I used to be disturbed when I saw an animal carcass floating towards me," says Mishra. "The state of the river is a tragedy."

Both priest and engineer, Mishra teaches electronics at the local Banaras Hindu University. In his spare time, he performs the job entrusted to him by his father, the late Professor Veer Bhadra Mishra, who taught hydraulic engineering and who, decades ago, became distressed at the raw sewage, industrial effluent and rubbish being pumped into the river.

In 1982, the elder Mishra set up the Sankat Mochan Foundation. Its aim was - and still is, since the river has become even dirtier - to clean the Ganges. Given that this task has proved too much for successive Indian governments, with all the resources of the state at their command (not to mention the billions of dollars that have poured in from international aid organisations), it can be said with no disrespect that the foundation has failed totally.

On a muggy, monsoon day with grey skies and clouds hanging low over the city, the river looks healthy; the water levels are high, swollen from the rains, and the current is strong. But, as Mishra keeps warning anyone who will listen, if Indians continue this pitiless abuse of their most sacred river, it will become little more than a filthy, fetid sewer.

When the current drops, it already bears a strong resemblance.

The Ganges flows for 2,500km from the Himalayas through five states in which a total of 400 million Indians live, and depend on the river for food and water. As it passes through 100 towns and cities, it absorbs all their human and industrial waste.

Millions of litres of untreated sewage from the towns along the Ganges enter the river every day. By the time it reaches Varanasi it has become one of the most polluted rivers in the world.

Varanasi flings its own special confection into the toxic brew: partially cremated, putrescent corpses that belong to families who are perhaps too poor to buy sufficient quantities of wood for a thorough job and the ash of bodies that have been more successfully incinerated. The funeral pyres burn day and night on the cremation ghats ("ghat" is the word for the steps that descend to the river).

Manikarnika, the main cremation ghat, offers a tableau that looks like a Hieronymus Bosch-Francis Bacon co-creation. Surrounded by unbelievable filth, male mourners gather to cremate their loved ones on squelchy, littered ground, amid foraging cows, stray dogs and goats. Logs are piled high, looking menacingly eager to claim their next body. The main building on the ghat is a large, blackened, windowless structure that seems haunted. The only splash of colour in this grim scene is the red and gold of the shrouds covering the corpses. Then plumes of smoke rise and the fires blaze.

Local scientist and environmentalist B. D. Tripathi estimates that 32,000 bodies are cremated on the ghats every year, resulting in 300 tonnes of ash and 200 tonnes of half-burnt human flesh, all of which is thrown into the river. He doesn't estimate the number of animal carcasses thrown into the water.

Distinguished people such as Tripathi know how serious the problem is but somehow India's collective will has failed. In this country, problems take generations to solve. The desire to act is missing - and not just in Varanasi. Umpteen other water bodies all over the country, including the stunning Dal Lake, in Kashmir, are polluted by raw sewage and other filth.

The Ganges, though, has a new champion.

Prime Minister Narendra Modi is a devout Hindu who contested the May general election from Varanasi and won the seat by a thumping majority. On the day he returned to the ancient city, formerly known as Benares, to thank its citizens for his victory, he made a vow to clean up the river and Varanasi as a whole. In several speeches since, he has spoken of the filth in India and how Indians must develop clean habits.

"Tourists come [to Varanasi] because of its reputation for spirituality and antiquity," says Sanjay Sahani, a slightly built, 21-year-old boatman. "When they arrive, they curse me and say, 'Never again'."

If Modi has his way, Varanasi will be reborn as a sort of spiritual Venice, attracting millions of tourists and offering an experience that is unforgettable - in a pleasant way.

In June, at a special conference on cleaning the Ganges in New Delhi, Minister of Water Resources Uma Bharti said four ministries were working together, along with scientists and engineers, to draw up a plan. Moreover, Mishra says, meetings have taken place in Varanasi between NGOs (including his own) and government officials, such as Modi's most trusted aide, Amit Shah.

The government has allocated US$340 million for cleaning the river. Germany, having successfully cleaned up the Rhine, once one of the most polluted rivers in Europe, wants to lend its expertise and the Indian Army has offered to set up a task force to help the clean-up. Last month, the government began a six-month project to install hi-tech sensors at crucial points along the Ganges to monitor industrial waste, giving real-time data on which factories are pumping excessive effluent into it. The culprits will, it has been promised, face legal action.

Normally, such talk would lead to the rolling of eyes. After all, the first effort to clean the river was discussed in the early 1980s, when then prime minister Indira Gandhi met Mishra Snr and urged him to set up his foundation.

A few years later, in 1986, another prime minister, Rajiv Gandhi - Indira's son - launched the Ganga Action Plan, declaring: "We have allowed the pollution of this river, which is the symbol of our spirituality. In the years to come, not only the Ganga but all our rivers will be clean and pure, as they were thousands of years ago."

That campaign failed and others came and went. The level of toxins and dangerous bacteria found in the river is now 3,000 times higher than what the World Health Organisation considers safe.

Not that any of the statistics deter the multitude of Hindu pilgrims, many of them from poor families in rural India, who arrive in the city after a monstrously uncomfortable train journey. As they walk down to the ghats, they are visibly excited to see their holiest of holies.

The men and boys strip down to their underpants to take a dip. Modesty dictates that women wade in draped in saris. It is a moment of spiritual ecstasy.

Sahani sits on Tulsi Ghat, near Mishra's Hanuman temple, and closely watches a family enter the water.

"There are no lifeguards here," he says. "If a pilgrim starts drowning, we are the ones, the boatmen, who dive in to rescue them. I have rescued at least 50 people. My father rescued 100. Some pilgrims get carried away by emotion and, in their euphoria, go too far in."

Sahani's friend, tour guide Rajesh Choudhury, is a thoughtful young man of slight build and height. If the Varanasi authorities were to speak to him for five minutes, they would be given some good ideas on how to improve the ghats.

"There are no signs anywhere," he says. "We need signs all over saying 'Don't litter', 'Don't use oil, soap or shampoo when you bathe', 'Don't urinate in it', 'Don't bring your cattle into it' - build public toilets on the ghats, build changing rooms for women, build some benches where people can sit. And then, when the signs are up, we need a special police force, the Ghat Police, to enforce the rules."

When some tourists tell Choudhury that they want to take a boat out with Sahani to see the sun rise on the Ganges and ask him to come along, the tour guide becomes evasive. "I don't want them to go," he says. "On Prabhu Ghat, there will be a line of bottoms, men coming to defecate in the river. It's too embarrassing."

Since taking office on May 26, Modi has had to dwell at length in public speeches on the need for toilets, for cleanliness, for order. Never mind all that "India is poised to become a superpower" stuff, he has even had to tell civil servants to tidy up their rooms, stack files up neatly and throw away clutter. The fact he has to remind his people of such things exposes a lack of civic sense in India, particularly in the Hindi heartland.

Those in Varanasi who worry about the Ganges are hoping that Modi will be as good as his word. What encourages them is his reputation as a man of action, a trait as rare as a minotaur in India.

"If anyone can clean the river, it is Modi. If he fails, then we can forget it forever," says Nitin Sharma, a taxi driver who can barely speak because his mouth is full of paan (a mixture of chewing tobacco, areca nut and sweeteners wrapped in betel, which colours the mouth bright red/orange), a habit that Varanasi citizens are fond of.

Mishra says, with a touch of pride, that it was he who first alerted Modi, before he became prime minister, to the imminent death of the river, when the two men met in Varanasi last year. Sitting on Indian-style seating in the foundation's office, with bolsters and mattresses covered by white sheets and a garlanded photo of his father in the background, Mishra shows no sign of being dispirited about almost 30 years of failed efforts. He, too, is forced to go lowbrow, and speak about faecal coliform counts rather than faith, and about sewage rather than saving souls.

"Our slogan is 'Not a single drop of sewage should go into the Ganga'," he says.

"Hindus cannot be separated from the Ganga. It is the medium of our life. For me it is a living goddess. I cannot see our other gods or goddesses but I can look out of my window and see the Ganga."

Every time he travels, Mishra carries Ganges water with him. Whichever hotel bathroom he finds himself in, he fills a bucket (for Indian-style bathing) with water and pours a drop into it.

"When I do that, it purifies the water, turns it all into pure Ganga water," he says, the priest in him suppressing the engineer.
 

the dhobis (washermen) clean laundry in the water and hang it out to dry on the ghats; boys take a running jump from a high ledge and dive joyously into the river; holy men in saffron robes and matted hair perambulate, seeking wisdom or a gullible tourist to fleece; boys play cricket; and, as always, there is the boat ride, the high point of the Varanasi experience.

When the craft glides away from the bank, allowing the magical riverfront of mansions, temples and fortresses to come into view, often as the melancholy sound of a flute wafts over the waters from somewhere on the ghats, you might momentarily forget that Varanasi is a slum.

The noises from New Delhi about a clean-up of the Ganges sound hopeful but the underlying problem will be hard to tackle. Piles of stinking rubbish lie all over Varanasi. Pigs wallow in black stagnant pools of water. The proprietors of roadside eateries cook snacks beside open sewers infested with flies. After finishing their snacks, customers fling the wrappings onto the ground. Men spit and urinate in public. In the narrow, winding alleys of the old quarter, the rats are as big as puppies.

Even the city's cycle rickshaws are the tattiest and shabbiest in the whole country.

Mark Twain said, "Benares is older than history, older than tradition, older even than legend, and looks twice as old as all of them put together." Well, OK, but must it be so dirty?

Stanley Benjamin, 37, a baby-faced hotel manager from Kerala, south India, can't help but shudder when he describes the culture shock he faced on arriving in the city seven months ago. He looks after Suryauday Haveli, a pretty, 100-year-old mansion on Assi Ghat that has been turned into a boutique hotel.

"They always blame the government instead of looking at themselves. They keep their homes clean but throw their rubbish out onto the street. The people next door chew paan and spit it out onto our wall," he says.

Cleaning the Ganges is not a task that can be undertaken in isolation. It must be seen in the context of a cultural ethos that tolerates high levels of filth, ugliness and selfishness in public spaces. Modi commented on this mindset during a visit last month to immaculately clean Japan. While making a presentation, an official in Kyoto remarked that the Japanese had learnt their habits of cleanliness from the Buddha, who was, of course, born in India.

"Yet we in India have forgotten all this …" murmured Modi.

The Japanese have agreed to donate money and expertise to help India clean the Ganges and turn Varanasi into a version of Kyoto, a modern heritage city.

The job, however, will be like the cleaning of the Augean stables, only, unlike Heracles, these labourers won't be able to change the direction of a river to flush away the filth - for the river itself is the problem.