स कदाचित्सरस्वत्या उपस्पृश्य जलं शुचिः ।
विविक्त एक आसीन उदिते रविमण्डले ॥ १५ ॥
sah-he; kadacit-once; sarasvatyah-on the bank of the Sarasvati; upasprsya-after finishing morning ablutions; jalam-water; sucih-being purified; vivikte-concentration; ekah-alone; asinah-being thus seated; udite-on the rise; ravi-mandale-of the sun disc.
Once upon a time, he [Vyasadeva], as the sun rose, took his morning ablution in the waters of the Sarasvati and sat alone to concentrate.
The River Sarasvati is flowing in the Badarikasrama area of the Himalayas. So the place indicated here is Samyaprasa in Badarikasrama where Sri Vyasadeva is residing.