The Zalomka () is a karstic river in the southern part of Bosnia and Herzegovina, and as part of the Neretva river system it is one of the largest sinking rivers in the country and Dinarides. It rises under the Morine plateau, near Brajićevići village in Gacko municipality, but also collects its upper course waters from Gatačko Polje.
Geography
The Zalomka is a karstic sinking river and part of the Neretva river system that collect its waters in the southeastern Bosnia and Herzegovina. Its main feature is intermittent nature of its flow, which depends on seasons and precipitations. It is one of the largest sinking rivers in the country and Dinaric Alps. The Zalomka River in its upper course runs through western fringes of Gatačko Polje, and in a section from Rašćelice to Fojnica is called Đerope. After passing through shallow gorge the river enters another large karst field or polje, namely Nevesinjsko Polje, where it is also called the Kolješka River.
The Zalomka's major tributaries are the Batuša, Markov Creek, Novaci, Jamnik, Sopiljski Creek a.k.a. "Babova Jama" (Jama=pit), Zovidol River, Bukovik, Vučine.
The Zalomka River basin, particularly as part of the Nevesinjsko Polje, is a tectonic depression that is bounded by mountain ranges of different heights and highlands. The southern reaches of the polje is framed by relatively low mountains, while bordering on the Velež (mountain) on the east, in the north with the Crvanj mountain and the Morine plateau on the northeast, on the east-southeast are the mountains of Bjelasnica and Bab. The exact boundaries of the plateau and watersheds are difficult to determine in the karst due to the extreme porosity and cracking of the limestone that drains water underground.
Hydrology
Throughout its course the Zalomka empties certain part of its waters into numerous estavelle, biggest of which is the last one near village of Biograd, which is also the lowest place of the field at 799 m a.s.l. With a swallow capacity of , this particular estavelle is one of the largest in the Dinaric Alps' karst. It is directly linked to the source of the Bunica which is situated at 37 m a.s.l., so that the sharp difference in height is reflected in the rate of groundwater flow, whose notional (fictive) speed is up to , making it the fastest underground flow in the Dinaric karst. The ratio between the highest and lowest water level in the underground is 312 m, which is the largest amplitude in the world.
The Zalomka retain its waters for roughly 200 days per year. During the dry season, Zalomka dries up significantly on most of its course, leaving fish-rich pools also suitable for swimming. During late winter and most of the spring, water level gets significantly higher.
Upper Horizons Hydroelectric Power Stations System
Regardless of high ecological value and even higher vulnerability, the plans of harnessing hydroelectric energy from hydropower in Eastern-Herzegovina karst of Bosnia and Herzegovina are seriously considered by municipal and entity governments with revival of an old HES Upper Horizons concept, so works on the initial stage of the project are already underway with construction of water canals and tunnels, as well as a dam for reservoir of HPP Dabar in Dabarsko Polje. The location permit for construction has been issued.