The Cerna (Hungarian: Cserna) is a river in Romania, a left tributary of the river Danube. The Cerna has its source on the south-east side of the Godeanu Mountains and flows into the Danube near the town Orșova. The upper reach of the river is sometimes called Cernișoara. With a length of 79 km (49 mi) and its basin of 1,380 km2 (530 sq mi), it carves an erosive tectonic valley with numerous gorges, quite deep sometimes. There is a man-made lake on it (Tierna), just before it crosses the Băile Herculane spa, to perpetuate the old toponimic od Dierna.[clarification needed] The upper course of the Cerna is part of the Domogled-Valea Cernei National Park. The Cerna flows through the villages and towns Cerna-Sat, Țațu, Băile Herculane, Pecinișca, Bârza, Topleț, Coramnic and Orșova.

The Valea lui Iovan-Cerna dam is located on the Cerna River at its intersection with the Valea lui Iovan River. The Cerna reservoir has a maximum volume of 124 million m3 and an area of 292 ha.

The Herculane Dam is the second important barrier obstructing the waters of the Cerna River. It is located 7 km upstream from Băile Herculane, has a volume of 15.8 million m3, a retention level NNR of 235 m above sea level, and an area of 75.2 ha.

The Cornereva Dam is located on the main tributary of the Cerna, Belareca (with a discharge of 6.24 m³/s) approximately 5 km upstream from the village of Cornereva.

At the end of its journey, the Cerna flows into the Danube at Orșova via a large bay. This bay was formed when the Danube entered the Cerna's mouth following the construction of the Iron Gates I dam, which caused water levels to rise.

Tributaries

The following rivers are tributaries of the river Cerna (from source to mouth):