The Saar river, and its two source rivers, flow first through the Moselle department, in the Lorraine region; then, for a short distance, flow through the Bas-Rhin department, in the Grand Est region. From Sarrealbe to Sarreguemines, the Saar flows along the border with Germany. At Sarreguemines, the Blies river, the largest tributary of the Saar, flows into the Saar and its discharge rises from 20.9 m³/s to 41.5 m³/s.