Schwarzbach has its origin in the southern range of hills that separates
Klettgau from the
Rhine. Its headwaters lie approximately two kilometers northwest of the municipality of
Rafz in Switzerland and one kilometer east of the village Berwangen in
Dettighofen, Germany. South of Dettighofen, the river forms a short section of the
Germany–Switzerland border. After about four kilometers the Schwarzbach runs entirely on German territory, passing the villages Bühl and Riedern am Sand, and leaving its valley near Riedern am Sand to flow across the plain of Klettgau. Shortly after it enters the plain, roughly halfway through its course, the creek Seegraben flows into it from the east. Like Schwarzbach, Seegraben also originates along Switzerland's northern border in the southern hills of Klettgau, near the Swiss village of Osterfingen and the valley Wangental. On the plain in Klettgau, the Schwarzbach flows further west with a gentle slope. It flows through the village Grießen and passes Geißlingen further south. Near upper
Lauchringen, it flows into the Klingengraben from the left with a flow of approximately . == Infrastructure ==