Drammensvassdraget is a river system in Norway. It is located in Oppland and Buskerud and ends with the Drammen Drammen at the Drammensfjord. The flow rate at the mouth is about 300 m³ / s With a length of 301 km, the system is the seventh longest river in Norway. The catchment area is 17,110 km ².

The system consists of three major sub- streams; which flow together Tyrifjord and then form the Drammenselva:

  • Begnavassdraget ( with the rivers and lakes Begna, Vangsmjøsi, Slidrefjord, Strondafjord, Aurdalsfjord, Sperillen, Ådalselva and Storelva )
  • Hallingdalsvassdraget ( with the rivers and lakes Hallingdal, Krøderen and Snarumelva )
  • Randsfjordvassdraget ( with the rivers and lakes Etna, Dokka, Randsfjord, Randselva and Storelva )