Ayodhya Mahatmyam is a text that consists of 10 chapters describing various holy waters and holy shrines of ayodhya, this text is a part of Vashnava Kanda from Skanda Purana.
Chapter Two of Ayodhya Mahatmyam tells us about the holy waters of ayodhya Brahmakunda, RunaMochana, Paapamochana, Sahasradhaara teertha