Strymonas River is one of the Balkan rivers with a total length of 360klm (242klm are in Bulgaria and 118 in Greece). Bulgarians call the river Stroumia and during the Turkish domination was known as Kara-Sou. In Greek ground the river flows exclusively inside the borders of Serres prefecture and along with river Aggitis, his main tributary, they are belong to east Macedonia’s hydrographic area. Strymonas flows into Strymonikos gulf, which was named after him.
Flows from mountain Vitaza, southwest of Sofia, in a height of 2.200m. Going south, really wild at first, through rough ravines but later he shapes a fertile valley between mountains Rougien and Rila. Continuing his way to Greece, Strymonas opens up a passage between mountains Males and Pirin and few kilometers from Greece is joined by river Stroumitsa, who is flowing from mountain Plakovitsa located at southeast of Skopjia.
Strymonas enters into Greece west of village Promahonas, going through Roupel passage, that he opened up, between mountains Kerkini and Orvilos. To this point, cause of a rough change of incline of the ground, Strymonas looses his dash and splits into two branches. The west branch goes to lake Kerkini and then flows southeast where he joins again the east branch near to village Lithotopi.
Starting from this point and for the next 50klm where he joins with river Aggitis, the bed of Strymonas is artificial, with dikes and irrigation canals. This artificial bed was necessary to create because many large catastrophes happened at the past when the river was overflowing at this point. The irrigation canals take away the overflow water of the river and at the same time inseminates the valley.
Strymonas joins with Aggitis River, which is flowing from the south hills of mountain Falakro, 5klm before he ejects to Strymonikos gulf. At this place was the lake of Axinos that today is drained. Finally Strymonas goes through mountain Kerdyllia and Paggaio and ejects to the gulf, at the east of village Nea Kerdyllia, forming a small delta. Delta’s limited area is owed to influence of the waves and diffusion of materials brought by the river.
The main greek tributaries of Strymonas are river Boutkovas, flows into the small valley of Poroia in the prefecture of Serres, river Exavis, flows from mountain Kerdyllia, river Krousovitis, that flows from mountain Orvilos and river Xiropotamos that flows from mountain Mavrovouni. The total flow area of Strymonas is 16.500klm2 from which only 6.027 are in Greek land.
The river is rich in brought materials that gathered on the valley of Serres and on lake Kerkini: it’s estimated that over 4.000.000 millions m3 of materials are gathered when the average flow of water is 3,4 billions m3. His width never gets over than 250m and his depth reaches 3m.
The valley of Strymonas is the only passage of communication between Bulgaria and Greece and through it goes the highway Thessaloniki-Sofia. The petrifaction of the flow area of Strymonas is mainly transformed and composed by slates and marbles. At some areas can also be found gatherings of alluvium gold.
At the edges of the river exists a variety of aquatic vegetation and bushes that gives a charm to the river. Poplar trees, willow trees, acacias and plane trees are the most common. Many kinds of fishes live in Strymonas, like carps, perches and eels. The fauna of the ecosystem is complemented by a number of wild animals and birds that nest around the river and are depending on him.