What is "echaz"

The Echaz is a small river in Baden-Württemberg, Germany, a tributary of the Neckar. It has its source on the Swabian Jura, near Lichtenstein, south of Reutlingen. After flowing through Pfullingen, Reutlingen and Wannweil, it discharges into the Neckar near Kirchentellinsfurt, which lies halfway between Reutlingen and Tübingen.