According to a local legend, Phewa Tal covers the area of a once-prosperous valley, whose inhabitants one day scorned a wandering beggar. Finding only one sympathetic woman, the beggar warned her of an impending flood: as the woman and her family fled to higher ground, a torrent roared down from the mountains and submerged the town – the “beggar” having been none other than the goddess Barahi Bhagwati. The woman’s descendants settled beside the new lake and erected the island shrine of Tal Barahi.
The other, geological, explanation is that the entire Pokhara Valley, like the Kathmandu Valley, was submerged about 200,000 years ago when the fast-rising Mahabharat ridge dammed up the Seti Nadi. Over time, the Seti eroded an ever-deeper outlet, lowering the water level and leaving Phewa Tal and several smaller lakes as remnants.