The Drina is a 346 km long river in the Balkans, which forms a large portion of the border between Bosnia and Herzegovina and Serbia. It is the longest tributary of the Sava River and the longest karst river in the Dinaric Alps which belongs to the Danube River drainage basin. Its name is derived from the Roman name of the river which in turn is derived fro…The Drina is a 346 km long river in the Balkans, which forms a large portion of the border between Bosnia and Herzegovina and Serbia. It is the longest tributary of the Sava River and the longest karst river in the Dinaric Alps which belongs to the Danube River drainage basin. Its name is derived from the Roman name of the river which in turn is derived from Greek which is derived from the native name of Illyrian origin.