SB 5.17.5
tatra caturdha bhidyamana caturbhir namabhis catur-disam abhispandanti nada-nadi-patim evabhinivisati sitalakananda caksur bhadreti.
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
On top of Mount Meru, the Ganges divides into four branches, each of which gushes in a different direction [east, west, north and south]. These branches, known by the names Sita, Alakananda, Caksu and Bhadra, flow down to the ocean.