Three short hymns speak to the Waters as goddesses. They flow sleepless to the sea in channels Indra dug; some are of heaven, some dug, some free-flowing. Varuna walks among them judging truth and lies; Agni has entered them. The singer asks for their sap as from loving mothers, for the medicine Soma says they hold, for long life, and that they carry off whatever evil, lie or false oath is his. He asks for the sweet wave that became Indra's drink, which the Child of the Waters guards.
The Atharvaveda repeats the Rigveda's water verses as charms for cattle, strength, health and wealth, adds waters of desert and marsh, waters dug, waters brought in jars and rain, and calls the Waters golden-hued, those in whom Savitar and Agni were born.
What is different here:
Same verses turned to practical charms; adds the jar and the birth of Savitar in the Waters.
In the daily sandhya prayer the worshipper sprinkles water on the body with kusha grass while reciting the first three verses of Rigveda 10.9. The step is called marjana, also a bath with mantras.
What is different here:
The hymn as a living daily rite; no river needed, a few drops stand for the Waters.
South India · Andhra Pradesh, Telangana, Tamil Nadu, Maharashtra, AssamAll traditions
Twelve rivers each have a festival once in twelve years, when Jupiter enters that river's zodiac sign; crowds bathe, give gifts and honour ancestors, mostly in the first twelve days. The list differs by region: Bhima in Maharashtra, Tamraparni in Tamil Nadu, Brahmaputra in Assam. An astrological work of 1426, the Jataka Parijata, tells of a Brahmin named Pushkara to whom Shiva gave the power to live in water and purify the holy rivers, and who enters each river at Brihaspati's request as Jupiter changes sign.
What is different here:
Medieval astrological lore, not in the early texts; Shiva and Brihaspati appear; the river list varies between Maharashtra, Tamil Nadu, Assam and the Telugu states.
Sources: Hymns of the Rigveda, tr. R. T. H. Griffith (1896), hymns read for the Vedic layer; Dashashwamedh Ghat (Wikipedia); Hymns of the Atharva-Veda, tr. R. T. H. Griffith (1895); Marjana, Hindupedia (from Swami Harshananda, A Concise Encyclopedia of Hinduism); Sandhyavandanam (Wikipedia); Pushkaram (Wikipedia)