ABSTRACT
The construction of dams and reservoirs in karst regions results in considerable environmental impacts. Mostly the impacts are positive and predictable (flood reduction, water supply improvement, power production, infrastructure improvement, and reduction of deforestation), but in some cases they are negative and unpredictable. The common negative environmental impacts are: severe changes to spring discharge, deterioration of groundwater quantity and quality, threats to endemic fauna, induced seismicity, and induced occurrence of collapse dolines and some other secondary uncertainties. For example, construction of the Trebišnjica Hydrosystem (Herzegovina) is expected to eliminate recharge through many ponors resulting in a loss of recharge to the East Herzegovina karst aquifers of around 6 billion m3 per annum. The low flow discharge of some springs has been increased but the annual average discharge at the large springs has decreased considerably. For example, the average yearly discharge of Ombla Spring was reduced from 33.8 m3 s−1 in natural conditions to 24.4 m3 s−l after construction. Submergence of the Trebišnjica spring zone by Bileća reservoir prolonged the duration of floods in the Fatnicko Polje.
