This 57 km long river is the longest tributary of the Vacha and drains the highest parts of the ridges Batak Mountain and Veliyshko–Videnishki of the western Rhodopes.

[2][3] It was created to conserve rare flora and fauna, and the pristine riparian forests of common alder (Alnus glutinosa) and European ash (Fraxinus excelsior).

The zone protects important populations of brown bear, chamois, red deer and Eurasian otter, as wells as the beetle Lucanus cervus.

[4] A small path branches off from the main ecological trail and leads to the Samodivsko Praskalo waterfall, among the tallest in the Rhodope Mountains, with two falls of 25 m and 45 m.[4] The river flows in Pazardzhik and Smolyan Provinces.

There are two small reservoirs along its upper course, Beglika and Toshkov Chark, as well as two major reservoir along its upper tributaries, Golyam Beglik and Shiroka Polyana, which divert part of its waters to the Batak Hydropower Cascade (254 MW), constructed mainly along the neighbouring Stara reka drainage basin to the northwest.