The stream system of the region and its characteristics are determined by the terrain, climate, and by the petrographical conditions. The western, high ridge of the Hășmaș mountains is a divide, it divides the catch-basin of the Siret river from the catch-basin of the Mureș in the west and from the catch-basin of the Olt in the southeast. The Mureș river arises from the Arama Neagra side of the Giurgeului mountains and running northwards takes the streams of the tributary valleys. In the Giurgeului basin it flows slowly, so it is marginated with marshes, mainly at the borders of Voșlobeni, Joseni and Remetea. The Olt river arises from the marshy moors situated in the Sóvető mountains, about 15 kilometres from the headwater of the Mureș. It flows southwards beginning from the foot of the Hășmașul Mare mountains, through Bălan, to the Ciucului Sus basin.
An other important stream of the land is the Bicaz brook; its origin goes back in the time of the overflow of the Red Lake. The brook flows across a natural dam, through the Bicaz gorge, then into the Bistrița river. Its left-side branches are the Cupaș, Lăpuș, Șugău and Jedan brooks. Its right-side branches are the Bicajel, Surduc and Dămuc brooks. The streams in the southern side of the Hășmaș mountains are catched by the right branches of the Faget brook and by the left braches of the Iavardi brook; then through the Rece brook it flows into the Trotuș river.
Source: Pál T. - Rab J. - Wild F. - Csíki K.