RIVER

PETRE GÂŞTESCU1

Key words: Danube basin, discharge regime, hystory, management

The Danube is the second largest (805, 300 sqkm) and longest river (2,860 km) in Europe after the Volga. Its source area lies in the central-western part of Europe, in the Schwartwald, where two of its tributaries – the and the – spring from, bringing their waters together at Donaueschingen. Thence, the Danube crosses central Europe up to , the Pannonian Depression down to the junction with the , to finally pierce the Carpathian range at the Iron Gate and form a defile. It represents the southern border between the Romanian Plain and the Prebalkan Tableland. From Călăraşi (Romania) and Silistra (Bulgaria) to the Black Sea, the Danube rounds up the Dobrogea Plateau and its mountains, forming a Delta. Drainage basin The Danube covers 8% of the continent of Europe, its waters flowing on the territory of seventeen states (Germany, Switzerland, Italy, Austria, Czechia, Slovakia, , Slovenia, Poland, Croaţia, Bosnia-Hertzegovina, Albania, Yugoslavia, Romania, Bulgaria, the Republic of Moldavia, and the Ukraine). The formation process of the riverbed and valley of the Danube ended in the Late Pliocene and the Early Quaternary as the result of the successive drainage, in time, of some huge lakes from the , Pannonian and Pontic basins, themeselves separated from the vast Sarmatian Sea by the uplifting of the Alps, the Carpathians, and the Stara Planina mountains. The points of epigenetic or catchment penetrations show up today in the well-known gates or defiles (Devin, Iron Gate), dividing the river course into three distinct sectors: upper or Alpine, middle or Panonian and lower or Pontic (Walachian or Romanian). Upper course, long of 1,060 km, extends from the source area down to the Devin Gate. Right after the Brig joins the Brigach at Donaueschingen, the Danube loses in the Jurassic limestones of the Swabo-Franconian Jura Mts. Some 5 cu m/sec which run through the underground karst down to Tuttligen, in the Neckar drainage basin, a tributary of the Rhine (fig. 1). The Danube flows on between the Hercynian Swabo-Franconian Jura range, on the left, and the Prealpine heights, on the right, into the Münnich Basin at , wherefrom its channel becomes navigable. The major righthand tributaries (the Riss, , Günz, Mindel, , , Traun and the Enns) spring from the northern slopes of the Alps, accounting for the alpine discharge regime of this sector. Most of these tributaries drain a lot of lakes situated in glacial, moraine-barred valleys (the Forggen, Ammer, Starnberger, Walchen, Tegern, Chiem, Atter, Mond, Hallstätter, and the Traun). Some of the important lefthand tributaries are the Altmühl, the Naab and the , the Danube joining the last one at . The Ludwigs Canal, built on the Altmühl and the Main (a tributary of the Rhine), connects the Danube to the Rhine and the Black Sea with the North Sea. The highest discharge rate in this sector has the (810 cu m/sec), which is more than the Danube’s there (660 cu m/sec). As the riverbed slope varies from 0.6 – 0.9%, streamflow speeds by 1-3.5 m/sec. A landscape of gorges or defiles occurs wherever the Danube crosses some mountain summits or runs through hard rock, e.g. at Neuburg, Kalheim, Wachau, Bisamberg – Kahlenberg, the cataracts of Ardagger – Persenbeug, Strudel and Wirbel. The Grein-Ybbs Defile downstream the junction with the Enns, near the town of , is particulary picturesque. Defiles and cracks in slopes increase the hydropower station at Iochenstein (140 MW), Aschach (258 MW), Ottensheim, Linz etc.).

1 “Valahia” University, Târgoviste Petre Gâştescu

In Vienna, the Danube out into three streams: Donau Kanal, Alte Donau which is abandoned but still enjoyed by holiday-makers, and the Danube proper, used for navigation. Before passing through the Devin Gate, the Danube receives a lefthand tributary – the Czeck Moravia – (average discharge 62 cu m/sec), representing about 100 km – long border between Austria and Slovakia. Middle course from the Devin Gate to Baziaş (Romania) along 725 km. The portion which narrows down at Devin represents the river passage from the Vienna to the Pannonian basins, and is imposed by the smaller Carpathian range (Male Karpati). A few kilometers away, downstream the Devin Gate and the point where the Danube enters Slovakian territory, lies , Slovakia’s capital. Between Bratislava and Komarno (Komaron on the Hungarian side), the river stretches out two arms – the Danube itself on the right, forming the border between Slovakia and Hungary, and the smaller Danube (Mali Dunaj) on the left, closing in a 90 km – long island called inland delta by the Slovaks. It is in this sector that the two countries had built a hydropower station at Gabcikova, subsequently contested by Hungary, when the Slovaks commissionned part of it. From the Smaller Carpathians (Devin Gate) and the Mid-Hungarian Mountains (Visegrad Defile), the Danube passes through the Kiss Alföld (Smaller Plain), in the South, and the Slovak Plain, in the North. Some of the main lefthand tributaries, originating from the Tatra Mts., are the Váh and the Nitra (discharge rate 139 cu m/sec), the (82 cu m/sec) and the Ipoly, which forms a border between Hungary and Slovakia long of ca 150 km. An important righthand tributary is the Raaba (96 cu m/sec). After leaving the Visegrad Defile, the Danube takes a N-S direction, flowing along 275 km right through the middle of Hungary. Budapest, its capital, lies on either side of the Danube (Buda, on the right hills by the same name, and Pesta on the left, in a somehow higher floodplain). The two sides of the city are connected by numerous older and newer bridges. The place where Budapestans go for recreation and agreement is the Margareta Island. On the southern periphery of Budapest the Danube stretches out two arms: the river proper on the right, and Soroksari-Duna on the left with the Island lying in between. Farther on, the riverbed slope getting smaller (0.05%) the Danube meanders through the Pannonian Plain, leaving behind many abandoned arms, which we call ‘morotva’ (oxbow), on both sides. From the southern section of the plain, the Danube receives its biggest tributaries, substantially increasing its water volume. First comes the Drava (670 cu m/sec), next the (814 cu m/sec) and the (1,460 cu m/sec), the last one running into the Danube in Beograde, the capital of the Federative Republic of Yugoslavia. From its junction with the Sava down to Bazias, wherefrom its lower course begins, the Danube receives three major lefthand tributaries, all coming from Romanian territory: the Tamis (Timiş), close to Beograde, the Karas (Caraş) and the Nera (right on the frontier-line between Romania and Yugoslavia). There is only one righthand tributary, the Serbian , with remarkable discharge values (210 cu m/sec). Lower course, 1,075 km, stands for Romania’s natural border with Yugoslavia, Bulgaria, the Republic of Moldavia and the Ukraine. This sector boasts the longest and most beautiful defile, viz. the Iron Gate (144 km) and the most striking asymmetry (Drobeta Turnu Severin – Călăraşi, 566 km). It is a large floodplain, with the river braiding out and closing in successively two islands (Ialomita and Braila, 195 km). This is the sector of maritime navigation and of the (Braila – Sulina, 170 km). The Iron Gate Defile stretches out between Bazias and Gura Văii, narrowing down in some sections and getting larger in others, where small basins are formed. The first narrowed section is at Coronini, where big floods (e.g. in 1897) engendered a temporary upstream lake, suggestively called Mare Album, extending beyond Beograde. Similar conditions led to the formation of the Moldova Veche islet. The tectonic limestone zone at Coronini, called the Babacain Rock, constitutes an obstacle for navigation, likewise Cozia, Doica, Islazi, Tahtalia, Vrani, Vlas, Iuţi and Pregrada. A first Iron Gate dam was built at Pregrada and Iuţi Rocks.

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The Iron Gate hydropower station, shared jointly by Romania and Yugoslavia, was commissioned in 1971, having been operated at full capacity (2,100 MW) ever since. The construction of a the dam at Gura Văii and the formation of a storage lake flooded the Ada- kaleh Island and some Roman vestiges. A second hydropower station (Iron Gate II), downstream the Iron Gate, was also built jointly with Yugoslavia. In this sector, the largest Danube tributaries lie on the leftside, in Romanian territory (the , the and the Argeş); although rightside afluents from Yugoslavia and Bulgaria are more numerous, they are much smaller (the Timoc, Ogosta, , Vit, , Iantra and the Lom). In 1954, a road and rail bridge was built between Giurgiu (Romania) and Ruse (Bulgaria). Between Călăraşi to Brăila, the Danube unbraids and its many arms encompass the floodplain itself which, rich in lakes and backwaters and frequently flooded, has been suggestively named Balta Ialomiţei (Borcei) and Balta Brăilei (‘balta’ stands for floodplain). Both were dyked and the land used for farming. An impressive bridge for rail traffic, the longest in Europe, was built between 1890 and 1895 by engineer Anghel Saligny. It was a remarkable performance for that time, spanning the river form Feteşti to Cernavodă. A second bridge for road and rail traffic was commissioned in 1987. Not far away, downstream, where waters gather into a single channel, there stands another bridge for the road traffic (totalling 1,450 m, of which 750 m are suspended over the Danube). This bridge, the longest over the Danube, was opened to traffic in 1970. The last subsector of the river goes from the city-port of Brăila down to the Black Sea. It is known as the maritime sector, because high-tonnage sea vessels started entering the Sulina Arm (where rectification works were completed) and navigate up to Brăila beginning with the 20th century. The distance covered is 92 sea miles, or 170 km. Moreover, in this subsector the Danube receives two of its largest lefthand tributaries, the and the Pruth. Rectification works have facilitated the navigation of vessels as far as the top of the delta (Ceatal Chilia) with the consequent flourishing of the city-ports of Brăila, Galaţi (Romania) and Reni (Ukraine). Apart from it, the river is a bordeline between Romania, the Republic of Moldova and the Ukraine. This is the subsector of the Danube Delta which extends between the Chilia Arm in the North (117 km), Arm (19 km) and Sfântul Gheorghe Arm in the South (109 km), totalling an area of 4,152 sqm. Eighty-two per cent of this territory (3,446 sqkm) lies in Romania. The perpetual territorial evolution of this geographical unit is the outcome of the Danube’s discharge (6,472 cu m/sec of water and 58 mill. t/year of sediment); on the one hand, and of wave battering the shore, on the other. The Delta was and still is Europe’s unique faunistic and floristic repository. Despite massive anthropic pressure on this environment for agricultural, forestry and fish-farming purposes (until 1989), the delta still preserves many areas in natural condition. In 1990, the Danube Delta, together with the Razim-Sinoie Lake complex in the South and the marine waters up to the 20 m isobath have been declared a biosphere reserve, benefiting by adequate legislation, management and administration. Discharge regime In the upper course, the Danube regime is determined by its alpine tributaries increasing the water volume in June. The middle and the lower course of the river stand under the influence of the Drava and the Sava, which bring much water in spring (April-May), depleting the volume in autumn (september-october). In winter and summer, discharge is moderate (fig. 2). Average discharge. There is progressive up-to-downstream increase in the average multiannual discharge of 1,470 cu m/sec at , after the junction with the Inn; 1,920 cu m/sec in Vienna, 2,350 cu m/sec in Budapest, 5,300 cu m/sec after the junction with the Drava, the Tisza and the Sava. On reaching the delta, water volumes run up to 6,546 cu m/sec, through the contribution of its lower-section tributaries. Within the Delta itself, the water values are unevenly distributed on the three arms of the Danube: Chilia (58%), Sfântul Gheorghe (23.2%) and Sulina (18,8%). The same proportion holds for the 58 mill.

31 Petre Gâştescu t/sediment/year which makes the secondary delta of the Chilia Arm (in Ukraine) advance into the sea at an annual rate of about 40 – 80 m. Maximum discharge is recorded in spring, occasionally in summer, too, when waters are high: 15,100 cu m/sec at Orşova in April 1940; 15,900 cu m/sec at Olteniţa in May 1942, and 15,500 cu m/sec at Ceatal Chilia in July 1970. Minimum discharge occurs in autumn and sometimes in winter: 1,250 cu m/sec at Orşova in January 1954; 1,450 cu m/sec at Olteniţa in January 1964, and 1,350 cu m/sec at Ceatal Chilia in October 1921. As the climate is temperate continental, blocks of ice are floating on the lower course of the Danube from December until the beginning of March and, in particulary heavy winters, the ice bridge may last for 45-50 days, with traffic obstructions at Zimnicea, Călăraşi, Topalu, and Cotu Pisicii, sections closed to navigation during certain intervals. Water mineralization is moderate, despite the quantities of wastes spilt into the river by the large cites on its banks (Vienna, Bratislava, Budapest and Beograde), which has increased the quantity of water pollutants. However, the river’s impressive self-purification ability makes it recover in the lower sector, despite mineralization values coming close to 350-400 mg/l. History of Danube river The Danube is a navigable waterway of overriding importance and since very ancient times has helped bridging links between the populations inhabiting its banks. Traces of settlement date back thousands of years as people kept being attracted by fertile floodplains and terraces, the wildlife of willow forests and the wealth of fish populating the river itself and its great many lakes. Unfortunately, the Danube had not always been a bridgeway. There had been times, and they spaned five hundred years, when the lower course divided peoples. The Roman turned the river into a political frontier not easily surmounted because of the force resistance put up by the autochthonous populations, the Dacians, in particular. Therefore, the Empire set up a fleet on the Danube, built strategic roads and bridges – one at Drobeta Turnu Severin (Trajan’s Bridge), due to Appolodorus from Damascus, and another at Celei, near Corabia. The walls at Cazane preserve some stone inscriptions known by the name of Tabula Trajana and Tabula Domitiana, marking the construction of the Roman road on the right bank of the river under emperor Trajan (A. D. 98-117). Traces of Greek and Roman strongholds erected on this bank, many of which in Dobrogea, bespeak the intense activity that used to go on in the lower course during ancient times. Herodotus of Halicarnas (484-425 B. C.), the author of a nine-volume work, entitled Histories, tells about the inroads made by Darius I, the emperor of the Persae, presumably chasing the Scitians as far as Isaccea on the Danube (514 B.C.), which is an indication of the river having been navigable in those days as well. In the period of migrations, the Danube became a gateway to the Balkans. The 14th century ruler of Walachia, Mircea the Old, strengthened his cities on the Danube: Drîstor (Silistra), Giurgiu and Turnu Măgurele. Management of navigation The expansion of the Ottoman Empire and the establishment of some Turkish dominions on the river (Turnu, Giurgiu and Brăila) put limitations to navigation on the Danube, the situation being solved only in 1829 by the Treaty of Adrianopole. The European Danube Commission (EDC), set up in 1856, was assigned the management of navigation on the river and the undertaking of correction works to this end. Besides riparian states, also Great Britain and France enjoyed membership. The Commission discharged its duties until 1948, when the Convention legiferated the rights of riparian states. Under the terms of that Convention, the Romanian sector of the Danube fell under the control of the Fluviatile Administration of the Lower Danube (FALD), with central offices in Galaţi, a body belonging to the Danube Commission located in Budapest. This form of organization stimulated the development of several city-ports, which beside trading and transport functions started building and repairing river barges. Plans for connecting the Danube to the Rhine and the

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North Sea, respectively go back to the reign of Charlemagne (A.D. 793). They were aimed at extending the water transport by canal between the Altmühl (somewhere in front of Treuchtlingen) and the Main. Some traces of those works are still visible at Karlsgraben. Eventually, the two rivers were connected when the ‘Ludwigs-Donau-Main’ Canal was built (1836-1845). It cowers 177 km from Kahlheim on the Altmühl to Banberg on the Main. The Canal was operated until 1945. A new connection was made in 1959. The Main-Danube Canal, commissioned in 1992, is wide of 55 m at water level, 31 m at the bottom, and 4-4,5 m deep, with 12 m wide/190 m long spillways. It allows the passage of 90 m – long vessels (1,500 dwt) and of tugs (up to 3,000 dwt). Another goal was to shorten the distance to the Black Sea by having a canal built on the lower course of the Danube, between Cernavodă and Constanţa. Its main axis (Cernavodă – Basarabi – Agigea) was built between 1976 and 1984; the Basarabi (Poarta Albă) – Năvodari ramification was finished in 1988. In this way, access to the sea takes about 400 km less. The Danube – Black Sea Canal is long of 64.2 km (Poarta Albă – Năvodari branch 30 km), wide of 70-80 m at groundwater level and 7-7.5 m at the bottom, allowing for the passage of vessels of 5,000 dwt, and 6 m draught at a speed of 8-9 km/h, and of double-barge convoys of 3,000 dwt each, up to 296 m long and 23 m wide (fig. 3).

Fig. 1 Danube Drainage Basin

33 Petre Gâştescu

Fig. 2 The Danube River – Discharge Variation

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Fig. 3 The new Danube – Black Sea Canal; 1. Shipping canal; 2. Poarta Alba-Midia canal; 3. Look; 4. Harbour; 5. Principal bridge; 6. Railroad; 7. Asphalted road; 8. Trajan’s wall

35 Petre Gâştescu

REFERANCE

Gâştescu P., 1990, Fluviile Terrei, Edit. Sport-Turism, Bucureşti. x x x, 1983, Geografia României, vol. I, Geografia fizică, Edit. Academiei Române, Bucureşti.

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