The Shaum is a river in the Pardrayan steppes. It starts as extension of the Videssian Sea into the steppes and divides the it into east and west. It ends a little north of the God's Dung Heap.
The river is quite large and serves as a natural border between the Khamorth and the Arshaum, the latter driving the former out of the western steppes.
As Pardraya is based on the steppes of Russia and Ukraine, the Shaum is most likely an analog of the Volga River.