Garudapurana 1.83.44

1.83.44

dṛṣṭvaitāni pitṝṃścāryavaṃśyānviṃśatimuddharet /
brahmāraṇyaṃ mahānadyāḥ paścimo bhāga ucyate //

having seen these, he delivers twenty noble generations of ancestors. / The Brahmāraṇya is said to be the western part of the Mahānadī;