SB 5.17.6
sita tu brahma-sadanat kesaracaladi-giri-sikharebhyo ’dho ’dhah prasravanti gandhamadana-murdhasu patitvantarena bhadrasva-varsam pracyam disi ksara-samudram abhipravisati.
Translation by His Divine Grace A. C. Bhaktivedanta Swami Srila Prabhupada:
The branch of the Ganges known as the Sita flows through Brahmapuri atop Mount Meru, and from there it runs down to the nearby peaks of the Kesaracala Mountains, which stand almost as high as Mount Meru itself. These mountains are like a bunch of filaments around Mount Meru. From the Kesaracala Mountains, the Ganges falls to the peak of Gandhamadana Mountain and then flows into the land of Bhadrasva-varsa. Finally it reaches the ocean of salt water in the west.