Ceahlau Mountain is a true “water castle”, its hydrographic network having a divergent aspect, until finally being collected in Bistrita River. Their water intake is supported mainly by underground streams.
Presently, Bistriţa has “disappeared” in the bordering sector of Ceahlău. Between its confluence with Bistricioara River and the Izvorul Muntelui Dam, the largest artificial barrier lake in Romania was built: Izvorul Muntelui Lake, whose shore limits Ceahlău Mountain to the east. Bistricioara marks the north and north-west limit of the mountain, spanning on a length of 12 km, between its confluence with Pintic River and its mouth in Izvorul Muntelui Lake.
Bicaz, the third river in size amongst Bistrita’s tributaries, limits the mountain to the south, beginning from its confluence with Jidanului (Caprei) River and until Bicaz city.
Apart from Bistricioara and Bicaz rivers, the first class tributaries of Bistriţa river are a number of much smaller streams: Coşusna, Izvorul Muntelui, Secu, Izvorul Alb, Tiflicul, Răciuniţa and Schitul.
The main rivers in Ceahlău have their streams underneath the slants, at heights between 1250m and 1300m, where they drain the underground waters quartered in the debris. With the exception of Pintec River, all water flows have their origin point inside Ceahlau National Park, and all are relatively short (exception being Bistra River which has 17 km in length). Among these, Pârâul lui Martin, Schitul, Slatina, Tiflicul, Izvorul Alb, Izvorul Muntelui, Bistra and Neagra are more important.
Along the longitudinal profile of the rivers with the origin point in Ceahlau, you can see many breaks in the stream (Rupturi River on Izvorul Muntelui, Bistra Mare and Bistra Mica), caused by the presence of lithology horizons that are more resistant to erosion. The most representative example is Duruitoarea Waterfall, where the waters of Rupturi River swoop upon two steps from a height of 25m.