Ybbs, River, Lower Austria, meandering southern tributary of the River Danube, 130 km long, largely average to bad water quality (categories II-III); the mean rate of flow amounts to 29 m3/sec. at Greimpersdorf. The River Ybbs rises as River Weisse Ois near Mariazell (alt. 868 m) at the Lower Austrian/Styrian border and changes its name at Goestling an der Ybbs (alt. 532 m). The upper Ybbstal valley in the northern Lower Austrian Limestone Alps belongs to the Eisenwurzen area, the lower part widens in the foothills of the Alps near Hausmening (alt. 325 m) and forms the Ybbser Feld Plain. The River Ybbs joins the River Danube to the east of Ybbs an der Donau; the largest power station is located at Opponitz (10.8 MW). The following branches of trade and industry are of importance in the Ybbstal valley: construction of electrotechnical components (Hollenstein an der Ybbs, alt. 485 m), machine manufacturing and wood processing (office furniture) in Waidhofen an der Ybbs (alt. 362 m), steel industry in Sonntagsberg as well as wood processing in Amstetten and other municipalities. A narrow-gauge railway line connects Waidhofen and der Ybbs with Lunz am See (alt. 601 m) and Ybbsitz (alt. 414 m). The Lower Austrian Oetscher winter sports area is located east of the upper course of the River Ybbs (Lackenhof, alt. 809 m). Important tributaries of the River Ybbs include the Rivers Neuhauser Bach, Lackenbach, Bodingbach, Steinbach, Goestlingbach und Hammerbach, Kleine Ybbs, Schmarzbach, Url and Zauchbach.