 The Frigidolfo branch, before merging with Narcanello branch, receives the Arcanello branch, which have an average discharge of , which receives a minor branch originating from Lake Ercavallo.The Ogliolo stream, with an average discharge of and a length of (similar to the length of the main branch between the "Frigidolfo-Narcanello merge" at Ponte Di Legno and the "Oglio-Ogliolo merge" at Edolo) is sometimes considered as a "de facto" fourth branch of the Oglio river.It flows in a southwest direction, through Valcamonica and enters into the Lake Iseo at Costa Volpino.