Ganga Dussehra, on the Shukla Dashami of Jyeshtha, marks the day the Ganga descended from heaven to the earth — the Ganga-avataran. It is held that a bath in the river on this day, or even the remembrance of her, washes away ten kinds of sin (dasha-hara), and so the day is kept above all at the ghats, in the water itself.

The number ten runs through the rite: ten dips, ten lamps, ten flowers, ten of every offering, for the ten sins the Ganga carries away. The great river-towns — Haridwar, Rishikesh, Varanasi, Prayagraj, Garhmukteshwar, Patna — fill for the day, and the evening Ganga aarti reaches its fullest.

Coming at the height of summer, just before the monsoon, it is also a festival of water's mercy — the gift of the river honoured in the season when water is most longed for.

The sixty thousand sons of King Sagara were burnt to ash by the sage Kapila's glance, and their souls could find no release. Generations later, Bhagiratha undertook a fierce penance to bring the heavenly Ganga down to earth, so that her waters might touch their ashes and free them. Ganga agreed but warned that her fall would shatter the earth; so Shiva received her in his matted locks and let her down gently in seven streams. Bhagiratha led her across the land to the sea and to his ancestors' ashes, and they were freed. For that descent she is also called Bhagirathi.

The Ganga has been venerated since the earliest layers of the tradition — the Rigveda names her among the rivers, and the great tirthas along her course grew into the spiritual capitals of the north. Ganga Dussehra crystallised as the annual festival of her descent, and the riverfront cities built their identity around it: the stone ghats of Varanasi, the Har-ki-Pauri at Haridwar and the organised evening aarti are the living continuation of a very old reverence for the river as mother and purifier.

The descent of Ganga is told in the Ramayana's Bala Kanda (the Bhagiratha episode), the Bhagavata and Devi Bhagavata Puranas and the Skanda Purana, which contains an extensive Ganga mahatmya. The dasha-hara rite of the tenth of Jyeshtha, and the merit of the bath, are set out in the Purana chapters and the tirtha manuals; the Ganga stotra of Adi Shankara is commonly recited.

Ganga Dussehra falls in the fierce heat just before the monsoon, when rivers run low and water is most precious — a season that makes the reverence for the river, and the giving of water and cooling things in charity, immediate and practical. The gathering at the ghats and the honouring of the river also carry an old ecological sense: the health of the community was, quite literally, the health of its water.

King Sagara's sixty thousand sons, digging the earth in search of a lost sacrificial horse, disturbed the sage Kapila at his meditation and were burnt to ash by his opened eyes. Their souls, unpurified, could not rise. His descendant Anshuman, then Dilipa, then Bhagiratha, each tried to free them; it fell to Bhagiratha to undertake the great penance that would bring the celestial Ganga to touch their remains.

Brahma granted the boon but said the earth could not bear her fall. So Bhagiratha prayed to Shiva, who agreed to take the torrent upon his head. Ganga descended in her pride, meaning to sweep even Shiva away — and vanished into the endless coils of his hair, humbled, to be released at last in gentle streams. Bhagiratha led her down from the Himalaya, across the plains to the sea, and over the ashes of his ancestors, who rose freed. On the day of that descent the river is worshipped still.