Long-Term Changes in the Ecological Conditions of the Iskar River (Danube River Basin, Bulgaria)

The Iskar River, a Danube tributary, is the longest Bulgarian inland river, flowing through seven geographical areas of Bulgaria. It crosses one of the most urbanised and densely populated areas in Bulgaria—the city of Sofia and its surroundings; and it plays a major role in water supply for drinking, household and industry, discharge of sewage, irrigation, and power generation in the area. Therefore, the Iskar River has been subjected to growing pressure from human activities for long periods of time. This chapter presents a review of the available information about human activities in the Iskar River basin, Bulgaria, and their impact on the hydrological and ecological conditions of the river. The data presented and the case study illustrates the long-term changes in the ecological status based on benthic macroinvertebrates and fish. The results of this and similar studies may contribute to the implementation of the Management Plan for the Danube River Basin in Bulgaria, as well as for the River Basin Management Plan.