TAPATĪ A daughter of Sūrya.
1)
Genealogy. Descending in order from Viṣṇu are Brahmā--Marīci--Kaśyapa--Sūrya--Tapatī.
2)
Birth. Sūrya married Saṁjñā daughter of Viśvakarmā. He begot of Saṁjñā two children named Kālindī and Yama. At that time Sūrya (Sun) was not of the form as seen now. Saṁjñā, unable to bear the splendour of Sūrya who was of the shape of an egg entrusted her maid Chāyā with the work of serving her husband and left for a temple in the guise of a mare to do penance. Chāyā disguised as Saṁjñā served Sūrya for a very long period. Sūrya begot of her two children, Śanaiścara and Tapatī. Besides these, Sūrya had another daughter named Sāvitrī also.
[Chapter 47, Bhaviṣya Purāṇa] .
3)
Marriage. There was a mighty king in the Lunar race called Ṛkṣa in the beginning of Kṛtayuga. He had a son named Saṁvaraṇa. He was made king of his country by his father even while he was a boy. He was a pious and righteous man. Vasiṣṭha was his Guru and he taught Saṁvaraṇa the Vedas along with the Aṅgas. Once Saṁvaraṇa entrusting the administration of the state to Vasiṣṭha went to do penance in the forests. On his way he followed a deer for a long distance on horseback and reached a deep forest named Vaibhrāja alone. There he saw a lotus pond full of blossomed lotuses and Kalhāra flowers. Celestial maidens were playing there without interruption. Among them he saw a very beautiful maiden. She was Tapatī daughter of Sūrya. Even at first sight they became lovers. The king looking at her lost his balance and fell from the horse. At once great and charming Gandharvas approached the king and sprinkling water on his face brought him back from swoon. Tapatī was also upset and the other nymphs took her to her father's house and consoled her. Saṁvaraṇa returned on horse-back to his residence the city of Pratiṣṭhā. But the king neither slept nor ate any food. The sage Vasiṣṭha knew that all the ailments of the king were due to his love for Tapatī, daughter of Sūrya. So he flew up by his yogic powers and met Sūrya sitting in his chariot in all splendour. The sage described to Sūrya the love affair between Saṁvaraṇa and Tapatī and pleaded on behalf of the king for giving Tapatī to Saṁvaraṇa. Sūrya was pleased to hear that and sent Tapatī along with Vasiṣṭha to Saṁvaraṇa. Before long the marriage of Tapatī with Saṁvaraṇa was celebrated solemnly at Pratiṣṭhānagara. The celebrated emperor Kuru was the son born to Tapatī of Saṁvaraṇa.
[Chapter 21, Vāyu Purāṇa] . 4).
How she got that name. Because she was the daughter of Sūrya who makes the sky hot (tapa) by his brilliance, she was called Tapatī.
[Śloka 6, Chapter 171, Ādi Parva] . 5).
Tapatī becomes river Narmadā. Śūrya, father of Tapatī, blessed her and said she would thereafter flow west from the Vindhya as a river named Narmadā. The present holy river Narmadā is but Tapatīdevī transformed.
[Chapter 47, Bhaviṣya Purāṇa] .