Hólmsá, a glacial river drawing its water from the north and east of the Mýr­dalsjökull glacier, and often getting a good share of the floods when the volcano Katla erupts. Many outlets from the north of Mýrdalsjökull combine to form the river Brennivínskvísl (“The schnaps branch”), which joins Hólmsá after this has emerged from Rauðibotn, the southern end of the Eldgjá canyon, in many falls and rapids.