The source region of the Acher lies on the northeastern mountainside of the Vogelskopf ( sea level (NN)) an area divided into cirques formed by the ice age. The spring named the Acherquelle rises at a height of sea level (NN) in the area of the Ruhesteinloch, which is named after the Ruhestein Saddle to the east and is located between the Vogelskopf and Seekopf ( NN). The Acher initially flows northwards, descending steeply. At its confluence with the Seebach, which joins from the north from the Mummelsee below the Hornisgrinde, it turns westwards and flows through the trough-like valley of Seebach. Here the valley reaches a depth of about 550 metres between the Hornisgrinde and the Vogelskopf. In this section the Acher is also called the Seebach, a clue that the tributary stream from the Mummelsee was originally the main headstream of the Acher, despite its somewhate lower discharge. Below the Vorderseebach the Seebach merges with the Grimmerswaldbach from the north. Here the Acher valley heads south for about a kilometre roughly to where the rugged Gottschläg valley, with its Karlsruher Grat and the waterfalls at the Edelfrauengrab above Ottenhöfen, joins it. From the point where the Unterwasser valley joins from the south, the Acher continues in a northwesterly direction, flowing through the municipality of Kappelrodeck , to the Upper Rhine Plain, which it reaches in Achern, the largest town of the northern Ortenaukreis.