Austria Hydrography

Now and extension. – The original medieval name of Ostarrichi or Osterriche (“eastern domain”) appears under the Latin form of Austria for the first time in 996, in a document of Otto III to designate a Marca of the Empire (Ost Mark) intended for defense against the Avars and included in the Bavarian dukedom. Built along the Danube on both sides of the Enns, it became a duchy dependent only on the kingdom in 1156, roughly within the limits of present-day Lower Austria (Austria under the Enns) and Upper Austria (Austria above the Enns); the duchy increased in 1192 in Styria and part of Carniola. Then came into possession of the powerful House of Habsburg (1282), it expanded its dominions – within the territories of the present Republic and neighboring ones – first on the Duchy of Carinthia (1335), then on the County of Tyrol (1363) and on several occasions on Vorarlberg (1363-1473), while elevating the duchy of Austria to archduchy (1477). However, all these fiefdoms legally retained their independence, while confusing their territorial history with that of the Habsburgs (v.), up to the Pragmatic sanction of 1713, for which all these dominions were declared “Austrian hereditary provinces” and formed an indivisible and inseparable whole; in 1779, they increased the Bavarian Innviertel, annexed to Upper Austria. This unity which, together with the other Habsburg dominions, was proclaimed under the name of the Austrian Empire (1804), was increased by the Duchy of Salzburg (1809) and confirmed with the compromise of 1867, for which the Habsburg monarchy was divided into two domains.

Hydrography. – Austria, within its present borders, belongs to the Danube hydrographic system; however many of its watercourses have the basin largely not included within its territory. The Danube itself (v.) Does not cross the Austrian territory for about 350 km. of its upper course, from Passau to Bratislava, receiving only three Austrian alpine rivers, the Salzach, the Traun and the Enns. But it is truly the navigable river of Austria with an average flow rate in Vienna of kmc. 55.4 million per year, with constant flow rates (runoff factor 52.6%) and somewhat more pronounced soft flows in summer, while for about 32 days in winter it carries ice. The other northern Alpine rivers have much higher runoff ratios compared to rainfall, which sometimes rise to 70%, and therefore very considerable capacities. They have soft summers, and lean very accentuated winters, in relation to the type of alpine rainfall. The Inn (v.), The largest of the northern rivers, is not Austrian except for its middle course, from Hochfinstermünz to Kufstein, but has a very high runoff ratio (90%), glacial regime to prolonged lean winter (October- April), rapid ascent in April and maximums in July-September. The Salzach, which derives water from the glaciers of the Hohe Tauern, also has runoff ratios of over 90%, with minimum flows in February and maximum flows in August. The Traun, a completely pre-Alpine river, has a coefficient of only 65%, but due to the series of subalpine lakes it crosses, it has almost constant flows, with a soft light from May to September. The Enns instead, which runs longitudinally to the Low Tauern, only 62% of the water that falls into its basin flows out and has a very irregular regime. There is a lack of reliable data for the Mur, which has a short peak in June; the Drava has a runoff coefficient of 70% and a somewhat sub-Mediterranean regime, with early soft in spring and prolonged in autumn. For Austria 2007, please check extrareference.com.

There is generally an insufficient regime in Austrian watercourses, especially for the winter lean ones, which do not find compensation in other rivers with different regimes, nor in existing lakes in Austrian territory. In fact, of the two largest, Lake Constance (395 meters above sea level), to the west, is almost entirely outside Austria, and that of Neusiedl, at its eastern end (114 meters above sea level), is very shallow, has a variable perimeter and it is located 60 m. lower than the nearby Danube, so that it cannot be used as a reserve of water energy. The other major peripheral Alpine lakes of glacial origin are found only at the two northern and southern extremes of the state territory. In Upper Austria, Lake Atter (46.7 sq km, capacity 3934 million sq km) and Traun Lake (25.6 sq km, capacity sq km. 2302 million) are linked to the other surrounding minors (Irr See, Mond See, St. Wolfgang See, Altausseer See, Grundl See), but only feed the Traun basin. To the south, the Carinthian lakes are all grouped together in the Klagenfurt basin and on the Alta Drava (lakes of Wörth and Millstatt, surface area respectively 21.6 and 13.3 sq km, capacity 2302 and 1213 million sq km) at the almost border of the state, so that they have no influence on the Austrian river regime.

The hydraulic forces of the Republic were calculated (1925) at 3,694,000 HP. in the lean period; these were mainly supplied by Styria and Tyrol, with 760,000 HP. each, followed by Carinthia and Upper Austria (56 and 50,000 HP.). 1,650,000 HP are used today. and 335,000 are going to be.

Austria Hydrography

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