I could find the following references to the Sarasvati River in the Pali Canon:
Now at that time the brahmin Sundarika Bhāradvāja was sitting not far
from the Buddha. He said to the Buddha, “But does Master Gotama go to
the river Bāhuka to bathe?”
“Brahmin, why go to the river Bāhuka? What can the river Bāhuka do?”
“Many people agree that the river Bāhuka ...