The Cerna () 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 OrÃÂova. The upper reach of the river is sometimes called CerniÃÂoara. With a length of and its basin of , 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 BÃÂile Herculane spa, to perpetuate the old toponimic od Dierna. 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, ÃÂaÃÂu, BÃÂile Herculane, PeciniÃÂca, Bârza, TopleÃÂ, Coramnic and OrÃÂova.
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 BÃÂile 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 mó/s) approximately 5 km upstream from the village of Cornereva.
At the end of its journey, the Cerna flows into the Danube at OrÃÂova 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.
The following rivers are tributaries of the river Cerna (from source to mouth):