The Aheloy River or Achelous is a river in eastern Bulgaria

Bulgaria

Bulgaria , officially the Republic of Bulgaria , is a parliamentary democracy within a unitary constitutional republic in Southeast Europe. The country borders Romania to the north, Serbia and Macedonia to the west, Greece and Turkey to the south, as well as the Black Sea to the east...

. It originates in the Aytos

Aytos

Aytos , sometimes written Aitos and Ajtos, is a town located in eastern Bulgaria some 30 kilometers from the Bulgarian Black Sea Coast and belonging to the administrative boundaries of Burgas Province. It is the administrative centre of the homonymous Aytos Municipality...

-Karnobat

Karnobat

Karnobat is a town in the Burgas Province, Southeastern Bulgaria. It is the administrative centre of the homonymous Karnobat Municipality. As of December 2009, the town has a population of 18,480 inhabitants.-Geography:...

 mountain, 1.5 kilometres from Dryankovets

Dryankovets

Dryankovets is a village in the municipality of Aytos, in Burgas Province, in southeastern Bulgaria.-References:...

, and flows directly into the Black Sea

Black Sea

The Black Sea is bounded by Europe, Anatolia and the Caucasus and is ultimately connected to the Atlantic Ocean via the Mediterranean and the Aegean seas and various straits. The Bosphorus strait connects it to the Sea of Marmara, and the strait of the Dardanelles connects that sea to the Aegean...

 south of the village of Aheloy

Aheloy

Aheloy is a town and seaside resort in Burgas Province, eastern Bulgaria. it has 2,175 inhabitants. It is situated on the Bulgarian Black Sea Coast between the major port of Burgas to the north and the bustling tourist centres Nessebur , Slunchev Bryag and Sveti Vlas to the south.One of the...

. The Aheloy River has a length of 39.9 kilometres and has an irrigation reservoir, the Aheloy Reservoir, built along its flow. The river's drainage basin

Drainage basin

A drainage basin is an extent or an area of land where surface water from rain and melting snow or ice converges to a single point, usually the exit of the basin, where the waters join another waterbody, such as a river, lake, reservoir, estuary, wetland, sea, or ocean...

 covers 141 square kilometres and its average discharge

Discharge (hydrology)

In hydrology, discharge is the volume rate of water flow, including any suspended solids , dissolved chemical species and/or biologic material , which is transported through a given cross-sectional area...

 is 0.7 cubic metres per second

Second

The second is a unit of measurement of time, and is the International System of Units base unit of time. It may be measured using a clock....

.

The river is famous for being the site of the Battle of Anchialus of 20 August 917 between Bulgarian ruler Simeon I

Simeon I of Bulgaria

Simeon I the Great ruled over Bulgaria from 893 to 927, during the First Bulgarian Empire. Simeon's successful campaigns against the Byzantines, Magyars and Serbs led Bulgaria to its greatest territorial expansion ever, making it the most powerful state in contemporary Eastern Europe...

 and the Byzantines

Byzantine Empire

The Byzantine Empire was the Eastern Roman Empire during the periods of Late Antiquity and the Middle Ages, centred on the capital of Constantinople. Known simply as the Roman Empire or Romania to its inhabitants and neighbours, the Empire was the direct continuation of the Ancient Roman State...

 under Leo Phocas

Leo Phocas

Leo Phokas was an early 10th-century Byzantine general of the noble Phokas clan. As Domestic of the Schools, he led a large-scale campaign against the Bulgarians in 917, but was heavily defeated. He then plotted to seize the throne, but was outmaneuvered however by the admiral Romanos Lekapenos...

, one of the largest battles in the Middle Ages

Middle Ages

The Middle Ages is a periodization of European history from the 5th century to the 15th century. The Middle Ages follows the fall of the Western Roman Empire in 476 and precedes the Early Modern Era. It is the middle period of a three-period division of Western history: Classic, Medieval and Modern...

 and one of the greatest military successes of the First Bulgarian Empire

First Bulgarian Empire

The First Bulgarian Empire was a medieval Bulgarian state founded in the north-eastern Balkans in c. 680 by the Bulgars, uniting with seven South Slavic tribes...

.