Drau, River, also: Drava, east Tirol, Carinthia, western tributary of the River Danube, 749 km long (261 km lie on Austrian territory), third-largest (11.828 km2 ) catchment area in Austria after the rivers Donau and Inn. 310 m3/second average annual flow rate of the River Drau at Lavamuend (incl. the River Lavant); the stretch before the mouth of the River Gailitz (at Arnoldstein) offers very high to high water quality. The Drau rises close to the Toblacher Heide region (South Tyrol) in the Pustertal valley (Val Pusteria); below Oberdrauburg the Drau flows through Carinthia until it reaches Slovene territory just before Unterdrauburg (Dravograd); called Drava on its further course, it flows through the lowland of the Podravina area in Croatia and into the Danube just below the town of Osijek. Most important tributaries of the Drau in Austria are the southern Weissenbach, Gail and Vellach and northern Isel, Moell, Lieser, Afritzer Bach, Gurk and Lavant rivers. The Oesterreichische Draukraftwerke AG in Klagenfurt (OeDK) operates 10 hydroelectric power stations in Carinthia. Until 1785 the River Drau formed the border between the dioceses of ( Diocese) Salzburg and Aquileia.
The Drau Valley is U-shaped and composed of several smaller valleys: Pustertal valley (above the Lienzer Klause), Oberdrautal valley (from the "Tiroler Tor" to the narrow passage at Sachsenburg), Lurnfeld Basin (between the mouths of the rivers Moell and Lieser), Unterdrautal valley (from Spittal to Villach), Rosental (between Rosegg and the mouth of the River Vellach) and Jaun Valley (between Vellach and Schwabegg). The Drau valley is an important road and rail connection between east and west. Major Austrian cities on the river: Lienz, Spittal an der Drau and Villach; most important business activities in the Drau Valley: tourism, mechanical engineering, manufacture of footwear, electrotechnical industry, supply of electricity and agriculture.