engleski

How hydropower dams alter the flow regimes of Balkan rivers

Balkan rivers, which harbour high aquatic biodiversity, face a boom of hydropower dam construction. We reviewed the distribution and trends of hydropower plants (HPPs) in Slovenia, Croatia, Bosnia and Herzegovina, Serbia, Bulgaria and Montenegro. Furthermore, we analysed flow regime alterations induced by various types of HPPs (run-of-the-river, storage hydropower plants). Currently, 1043 HPPs are operating in the area, among which 779 plants are small HPPs (<1 MW), 174 medium (1-10 MW) and 90 large (>10 MW). An additional number of 1866 HPPs is currently planned to be built, mostly in Serbia and Bulgaria. Thereby, 463 of 1866 HP projects (25%) are planned in protected areas. The various HPP types have generally strong but varying effects on flow regimes, ultimately producing a flow regime differing from the pre- impact natural flow regime. Daily flow data show that depleted river reaches and those downstream of storage HPPs are subjected to most severe flow regime alterations, while run-of-the-river and diversion HPPs cause less severe hydrological alterations. Hydropeaking operation of storage HPPs induce additional impacts by rapid fluctuations of water levels, which strongly affect macroinvertebrate communities and they may cause the extinction of sensitive species protected by the Habitat Directive, and their replacement by more tolerant species or even invasive species. We conclude that the total extent of flow alteration by HPPs only gets visible if sub-daily hydrological data would be available, but this is not the case for most rivers in Balkans yet.

Hydroelectric Power Plants, dams, flow regime alteration, hydropeaking, protected areas, Balkan rivers

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