The principal rivers are the Aras and Kizil Uzain, both receiving numerous tributaries and flowing into the Caspian, and the Jaghatu, Tatava, Murdi, Aji and others, which drain into the Urmia lake.
Four rivers belonging essentially to Persia, in reference to the Caspian watershed, are the Seafid Rud or Kizil Uzain on the southwest, the Herhaz on the south and the Gurgan and Atrek at the south-eastern corner of that inland sea.
The Kizil Uzain takes up some important affluents and is called Seafid Rud from the point where it breaks through the Elburz to the sea, a distance of 70 m.
The greater portion of the province is a lowland region extending inland from the sea to the base of the mountains of the Elburz range and, though the Sefid Rud (White river), which is called Kizil Uzain in its upper course and has its principal sources in the hills of Persian Kurdistan, is the only river of any size, the province is abundantly watered by many streams and an exceptionally great rainfall (in some years 50 in.).