The underground water system fits the Orogenic Carpathian macro-region. In this area the aquifer layers are spread and relatively high, due to abundant rainfall, leading to the existence of a positive hydrographical balance. The underground waters participate in proportion of 30% to supply the surface hydrographical network, especially in the mountain sector, and less in the depression area.
Rivers – Uz River Basin, mostly located in a mountain area with rainfall exceeding 7-800 mm / year, is characterized by a high density of hydrographical network. Uz River and its tributaries have continually carved the relief, contributing in large measure to its current fragmentation and energy. Uz Valley, crossing different hard geological formations, is presented as a whole succession of depression basins and sectors of clough aspect. These cloughs are accompanied by enormous debris, as can be seen on the slope located between Bărzăuţa (right tributary of Uz River), and Nasolea Mare Fall (on the Uz River). The river makes its way through the well forested mountains, areas which have created extremely beautiful cloughs. Among the larger and very interesting tributaries, there are mentioned:
- On the right side – Bărzăuţa (20 km), Izvorul Negru (the Black Spring), Turbulea, Basca, Groza, Izvorul Alb (the White Spring) (now flows into lake “Poiana Uzului”);
- On the left side – in the upper course, it receives Eghersec, Oreg, Rata, Sovet, Măgheruş and Copuria tributaries, and the creeks Răchitiş 1 and 2, Plopu, Chitici, Câmpului and Boiştea find their way into the lake.
In terms of sanitation, Uz River water fits into category 1 sanitation, with cleanliness of 96-99%, it is transparent, colourless, odourless and with an oxygen content ranging from 9-14 mg / l.
Still waters - are represented by natural reservoirs and ponds. Bălătău Lake, which is 3 km away, was formed after a massive poorly cemented rock slide, in thickness of 30-40 m, on a slope of 30 degrees, barring the river bed of Izvorul Negru River, in the section called Rupturile de la Focul lui Ivan ("Ivan's Fire Rifts").
“Poiana Uzului” Lake is an artificial lake and is situated on Uz River on its entry in Dărmăneşti depression. The lake was created to supply water and to subordinate hydropower.