Arauca River
, western tributary of the
Orinoco River
, flowing through
Venezuela
and
Colombia
. It rises in the Cordillera Oriental of the Andes mountains, near the Venezuelan-Colombian border. Its easterly course is about 500 miles (800 km) long and forms part of the Venezuelan-Colombian boundary. The Arauca flows nearly parallel to the Apure and the Meta rivers to join the Orinoco about 60 miles (100 km) southeast of
San Fernando de Apure
, Venezuela. The level nature of the
vast
surrounding plains, combined with seasonal rainfall, results in widespread flooding during the rainy season (April to November).