The river has two sources. The longer branch, known as Siyahsu (meaning dark water, Kurdish Av-e Resh), rises near the villaqe of Toptepe in Mardin Province, Turkey, and flows 10 km to the confluence with the shorter branch, known as Beyazsu (meaning white water, Kurdish Av-e Spi).
Freshwater mussels and turtles live in the river. Trout are also raised commercially.
- Confluence of Siyahsu and beyazsu, Google Maps
- Source of Beyazsu, Google Maps
- Source of Siyahsu, Google Maps