Arda/ Ardas River basin


Bulgaria, Greece, and Turkey share the sub-basin of the river Arda/Ardas. The Arda/Ardas has its source in the Rodopi Mountains (Bulgaria) and discharges into the Meriç River. The Aterinska River is a tributary shared by Bulgaria and Greece.

The sub-basin has a pronounced mountainous character with an average elevation of 635 m a.s.l.

Pressures, impacts and responses

Dams are common for the Arda/Ardas sub-basin; 100 are located in Bulgarian territory. The largest ones serve multiple purposes: energy production, irrigation, industrial and drinking water supply. Flow regulation is a pressure factor resulting in hydromorphological changes; the change in the water temperature due to the construction of the big dams has had an impact on the macrozoobenthos in the downstream section of the Arda/Ardas in Bulgaria. In Greece, a dam was built close to the border with Bulgaria to regulate discharge from the Ivailovgrad Dam (Bulgaria); water from the reservoir also covers irrigation needs.

Non-treated urban wastewater, waste disposal and animal husbandry are pressure factors in the Bulgarian part of the basin, having impacts of local importance on the ecosystem. Eutrophication has been observed in the reservoirs of the (large) dams Kardgali, Studen Kladenez and Ivailovgrad. Nitrogen and organic pollution is expected to diminish since the sewerage system is being extended; it is now connecting 67% of the population. There are three new municipal wastewater plants, and a new one is under construction.

Mining activities have a local but important impact due to the presence of heavy metals in their discharges; five tailing ponds containing mining waste are potential sources of pollution. Industrial activities in the area are possible sources of heavy metals and organic pollution (impact of local importance).

There are nine waste disposal sites in the Bulgarian part; a regional disposal site is under construction.