The Struma River is the greatest river in the Western part of Bulgaria. Its catchment area is 10 800 sq.km. It takes its source from the Vitosha Mountain, runs first westward, then southward, enters the Greek territory at the Kula village and flows into the Aegean Sea. The river's length to the border is 290 km.
In the river valley of the Struma River there are 56 artificial lakes with a total volume of 141 mln cub.m. including the vast dam lakes of Studena, Pchelina and Djakovo. Due to the decrease of the industrial production in the country as a whole, the quality of the Struma waters, like most other Bulgarian rivers, bettered. The Pchelina Dam Lake is of a beneficiary effect as it stops most of the polluting agents. The sections from the town of Pernik to the town of Radomir and from the flow of the Djerman River at the village of Draganovo are highly polluted.
Working thermo-mineral and balneo-therapy establishments are included, in the Struma valley such as those in Kjustendil, Nevestino, Sapareva Banja, Rudartsi, Pernik, Knjazhevo, Sofia, Chepintsi, Birimirtsi, and others. The thermomineral springs are phenomena of an extreme national and international significance and they deserve care for preservation and enrichment.