Professor Nicolae Panin
The River Danube is one of the most important European waterways, flowing 2,857 kilometres across the continent from the Schwarzwald (Black Forest) Massif in Germany down to the Black Sea. Few people know that the Danube flows between two Black Forests: the first, mentioned above, is at the river source; the second is within the Danube Delta near the zone of the river mouth, and is called the Caraorman Forest, which in Turkish means Black Forest.
Nevertheless, the "Blue" Danube remains forever a river of life, a river of great economic and political importance to the European continent and, primarily, to the ten countries that border it: Ukraine, Moldova, Romania, Bulgaria, Yugoslavia, Croatia, Hungary, Slovakia, Austria and Germany.
The Danube drainage basin extends to 817,000 km2 with more than 15 countries sharing the Danube catchment area. Some 120 medium and large size tributaries, more than 30 of which are navigable, constitute the Danube Basin hydrographic network.
According to its geographical layout and geological structure, the Danube Basin can be divided into three major units.
1. The upper Danube rises as two small streams - the Breg and Brigach - from the eastern slopes of the Black Forest Mountains and extends down to the Devin Gate (Hungarian Gate), east of Vienna. The upper Danube Basin includes in the north the Swabien and Franconian Alb, part of the Bavarian and Bohemian Forests down to the Austrian M?hl and the Bohemian-Moravian Uplands. To the south lie the Swabian-Bavarian-Austrian foothills, up to the watershed divide in the Central Alps. The morphology of the valley varies from canyon-like to low, sometimes marshy, landscape.
2. The middle Danube Basin covers an area from the Devin Gate, connecting Leitha Massif with the Little Carpathians, to the mighty fault section between the Southern Carpathians and the Balkan Mountains, at the Iron Gate Gorge. The middle section of the Danube Basin is confined by the Carpathians in the north and east, and Karnische Alps, Karawanken, Julischen Alps and Dinaric range of mountains in the west and south. This closed mountainous encirclement embraces the South- and East-Slovakian Lowland (Little Alfφld - Alfφld means plain in Hungarian), the Hungarian or Pannonian Depression (Great Alfφld) and the Transylvanian Uplands. The flatness of the two Alfφlds is interrupted by the low peaks of the Western Carpathians and the Trans-Danubian Mountains, where the Danube passes through Visegrαd Gorge. Except where it passes through the gorge, it looks more like a flatland river, with low banks and braided course.
3. The lower Danube Basin is situated downstream from the Iron Gates, where the river crosses the South Carpathian Mountains. The basin is formed by the Lower Danube Plain (Romanian Plain) and Bulgarian Lowlands; by the surrounding uplands and mountains (Carpathians and Balkans); the Dobrogean territory; the Siret and Prut basins and the Bugeac plateau (Moldovan and Ukrainian territories). The river was once almost unnavigable within the Iron Gates due to a very high current velocity (up to 5-6 m/s). In the second half of the last century, the problem of navigation in this section was solved by digging a lateral channel and adding a parallel railway, which allowed rivercraft to be towed upstream against the current. Beyond the Iron Gates, the lower Danube flows across a wide plain, the river becoming shallower and broader. The last section of the lower Danube is represented by the Danube Delta, where the river splits into three main channels: Kilia, Sulina and St. George.
The birth of the Danube
The River Danube is a typical example of a so-called "polygenetic valley". The river links a series of basins, former lakes or inland seas, separated by mountainous chains: Vienna basin in the upper part; Little Plain (Little Alfφld) and Great Plain (Great Alfφld or Pannonian basin) in the middle part of the river; and Dacian Plain (Vallachian or Lower Danube Plain) below the Iron Gates. All these territories were parts of the Neogene Paratethys Sea, which was situated inside the Alpine system, and continued eastward up to the Aral Sea region.
In its run towards the sea, the river has to cross the most significant mountain barrier in Central Europe - the South Carpathian Chain. How, why and when did the Danube manage to penetrate the mountains through the Iron Gates or Djerdap Gorge, the largest and most spectacular gorges in Europe? These questions have not yet found a generally accepted answer. Let us briefly examine the problem of Iron Gate genesis and, implicitly, that of the formation of the River Danube as it is today, starting in Germany and finishing by flowing into the Black Sea.
The Iron Gates connect the Pannonian and Dacian (Vallachian-Pontian) basins. The gorge is more than 100 kilometres long and consists of several alternating wide reaches -Liubcova, Donji Milanovac and Orsova are the main ones - and narrows - Golubac, Gospodjin Vir and the Small and the Great Cazane.
The newest data (Posea et al., 1963; M. Maroviζ et al., 1997) suggest that almost the entire Danube breakthrough route in the Iron Gates section is controlled by faults. Displacement along faults in different geological periods led to the formation of several small basins (Liubcova, Donji Milanovac, Orsova etc.), which were ingressed from the Pannonian basin. At that period, direct communication between the two basins may have existed. In the late Sarmatian, a particularly active rise in the Carpathian arc occurred: in the Iron Gates section the Mounts of Almaj suffered the largest uplift and became the watershed divide between two palaeo-rivers that followed the water retreat from both sides, Pannonian and Dacian. The "Dacian palaeo-Danube" with a larger water discharge captured the "Pannonian palaeo-Danube". In prevailing opinion, the capture was realised at the end of the Pliocene or the beginning of Quaternary, some 1.6 million years ago. Thereafter, the River Danube began to cut its single gorge-like channel as a result of combined phases of mountain rising and base level (lake or sea level) lowering.
Once the crossing of the Carpathian Mountains had been effected, the River Danube flowed into the Dacian Lake, which had a linkage with the Black Sea in an area corresponding approximately to the present-day Danube Delta. The evolution of the Dacian Lake during the Pleistocene was entirely dependent on Black Sea level variations at that time, and the large sea level rises and falls, due to different Pleistocene glacial and interglacial phases, strongly influenced the development of the Dacian region. (For example in the last glacial period, about 20,000 years ago, the Black Sea level dropped by about 130 metres.)
Assuming that the Danube cut the Carpathian Chain at the beginning of Quaternary (Eopleistocene), the river needed another fairly long period of time (till the Early Upper Pleistocene) to reach the Black Sea as it flows at present. Generally speaking, the River Danube Basin appears as a succession of basins descending down to the Black Sea: Vienna basin, Little Alfφld, Great Alfφld, Dacian basin, Black Sea. The river had its own development in each of these basins and finally reached its present-day course late in the Quaternary - geologically speaking, the Danube is a latecomer to the Black Sea. The present-day landscape is the synergetic result of all the above natural factors. The influence of human activity came later - only in the last century and a half. Compared to the geological changes to the environment, the anthropogenic ones are on another scale of importance and time.
The characteristics of the river
From the hydrographical point of view, the Danube Basin has an almost symmetrical pattern: 44% of the total river basin area lies on the right bank, and 56% on the left bank; 15 important right bank and 20 significant left bank tributaries flow into the River Danube. Nevertheless the right bank tributaries provide a substantially larger contribution (about 66%) than the left bank tributaries (only 34%) to the total run-off of the River Danube. About 120 tributaries empty into the Danube.
The chart below shows the main Danube tributaries and their contribution to the total water discharge of the river. The major part of water inflow originates from the downstream ends of the upper and middle Danube Basins.
* The River Timok has a drainage basin smaller than the limit accepted for this table; nevertheless it is included in the table because it represents the border both between geographical units and between Yugoslavia and Bulgaria.
In spite of the fact that one third of the total Danube drainage basin lies in the lower Danube reach, the tributaries in this section do not make a very significant water contribution to the total. In this lower section, the left-bank tributaries prevail over the right-bank ones. From the right bank, the major Danube tributaries are, from west to east, Timok in the Yugoslavian Federation - forming in its lower course the border with Bulgaria - and Ogosta, Yantra, Lom, Iskar, Vit, and Osam in Bulgarian territory. The left bank of the Lower Danube is within Romanian territory, almost 98% of which is drained by the Danube.
The Danube fluvial system has the following characteristics: a length of 2,860 km; drainage basin of ca. 817,000 km2, characterised by a mean annual rainfall of 816 mm, a mean annual evaporation of 547 mm and mean annual run-off of 246 mm; an average annual water discharge at the upper end of the delta of 6,550 m3 s-1 (Almazov et al., 1963; Stanηik et al., 1988).
More recent computation and statistical processing of data, collected over almost 130 years (Bondar, 1991, 1993), estimates the multi-annual water discharge of the River Danube into the Black Sea at QD = 6.047 m3.s-1 with a tendency to slight increase. The extreme water discharge values recorded till now are: Q max. 1970 year = 15,540 m3.s-1 and Q min. 1954 year = 1,610 m3.s-1.
The average annual suspended sediment discharge before the building of the Iron Gates dam was 2,140 kg.s-1 (67,5 millions t/year), out of which sandy alluvia formed approximately 10%. According to Bondar (1991, 1993), the multi-annual sediment discharge at the River Danube mouths was: RD = 51.7 million t/year, with a decreasing multi-annual tendency.
After 1970, following the building of Iron Gates I dam (942.95 kilometres from the Black Sea) and the hydrotechnical amelioration works along the Danube tributaries, the sediment discharge decreased by approximately 10-20%. In 1983, the second barrage, at Ostrovul Mare (864 kilometres), was built up and this new closing of the Danube induced a really catastrophic decrease in the sediment discharge: in all the stations the measured sediment discharge dropped by 35-50% compared to the mean value of pre-damming sediment flux regime. At present, therefore, one can estimate that the Danube total average sediment discharge cannot be larger than 30-35 million t/year, out of which 4-6 million t/year are sandy material (Panin, 1996). This is the only amount of sandy sediment contributing yearly to the littoral zone sedimentary budget, which since 1970 became severely reduced, with the beaches suffering catastrophic erosion, up to 15-20 m/year in certain sections. It is also obvious that the present-day sediment load of the Danube originates mainly in the eroded bottom sediments of the river course and this is affecting the entire ecosystem, as well as the civil TYPEering works along the river.
The Danube Basin is under Atlantic, Mediterranean and continental influence. Alternating Atlantic and continental effects can be observed within the entire basin; the Oceanic and Mediterranean influences are more frequent and intensive in the upper Danube than in the more continental lower Danube. Average annual air temperature within the basin ranges from - 6.2?C to +12?C. The lowest value is reported from Sonnblick, while the highest mean annual temperature was observed in the Pannonian Basin and in the Danube Delta, at the Black Sea coast. The precipitation regime depends on humid air masses transported from the Atlantic and Mediterranean and on advective processes within the frontal zone of the western wind zone. In addition to advective precipitation, convective processes in the form of rainfall and storm showers contribute to the precipitation total. Convective, mainly summer, precipitation is characteristic of the continental basins, while advective precipitation occurs under the influence of maritime air masses. Average annual precipitation ranges between 3,000 mm in the mountains to 400 mm in the delta area. For the lower Danube, the values are 500-600 mm/year. The wind regime is characterised by the prevalence of western winds within the entire basin. Their origin is the sub-polar depression and they generally convey humid air masses from the Atlantic to the European continent. The easterly winds carry drier air masses from the Euro-Asiatic continent into the Danube Basin and have an opposite effect. In the winter period, they prevail in the middle and in the lower Danube Basins. In the middle basin, such winds are called "Košava", blowing from the south-east; in the lower basin they are known as "Crivγt", a north-eastern wind.
3. Demographic and socio-economic characteristics
According to official data, the total population of the countries sharing the River Danube drainage basin is about 225 million, while the population living directly within the Danube Basin is almost 83 million (37% of the total). There are five countries (Austria, Slovenia, Slovakia, Hungary, and Romania) where almost the entire population lives in the Danube Basin.
(ii) Economic activities
The Danube Basin countries have extremely different economic development levels reflected by Gross Domestic Product (GDP), which varies from country to country (more than $2,000 billion in Germany and less than $2 billion in Moldova).
The structure of GDP is also very different in the Danube Basin countries, depending on both natural conditions and economic development level:
- The share of the agricultural sector ranges from 1.1% in Germany to more than 34% in Romania;
- The industrial sector ranges from 19% in Romania to 44.8% in Ukraine;
- Tertiary sector production ranges from 37.4% in Ukraine to more than 70% in Austria.
(Source: Strategic Action Plan for the Danube River Basin)
The River Danube was declared at the Crete Conference in 1994 to be one of the ten most important Transport Corridors (Corridor No.VII) linking West Europe to Central and Eastern Europe and providing a bridge between Europe and Asia through its strategic location. The Danube Corridor is considered to be an important element for economic development in the region. Since 1984, the waterway link to the Black Sea has been shortened by about 250 kilometres by the Danube-Black Sea canal, which starts at Cernavoda and ends at Constantza. The opening of the Rhine-Main-Danube canal in 1992 made the Danube Corridor more accessible and more economically profitable for Western countries.
Unfortunately, the wars in Yugoslavia, especially the most recent one, temporarily stopped traffic on the River Danube and slowed down the economic development of the countries downstream from the region of war.
(iv) Energy and hydraulic works
Regulation works in certain sections of the Danube River started in the 16th century. At the beginning, these works tried to control or to limit the damage caused by flood peaks. Afterwards other purposes were added: to improve navigation; to improve water use for irrigation, industry and domestic supplies; hydropower development etc. The works consist of barrages for reservoir lakes, dykes and embankments for flood protection, canals, dredging and cut-offs for shortening the waterway and for improving navigation and drainage/irrigation networks.
The hydropower capacity of the Danube Basin is very important: the total installed hydroelectric capacity is currently over 29,000 MW.
The first hydropower dam on the Danube (the Kachlet dam) was built at Vilshofen (2,230 kilometres) in the period from 1924 to 1927. On the German reach of the river, there are another six large barrages in addition to the Kachlet dam.
The biggest hydropower and navigation system along the entire Danube is located at the Iron Gates. Within the Iron Gates gorges, the hydroelectric potential is of 11,250 kW/km, as a result of large water discharge (average value - 5,520 m3/s) and an average slope of 0.22%.
The Iron Gates I dam (942.9 kilometres from the Black Sea) includes a spillway 441metres in length in its central part, two lateral hydropower stations (Romanian and Yugoslavian), each 214 metres in length (with a total installed power of 2,100 MW and a theoretical yearly average production of 10,500 GWh), and two double locks disposed on the river banks with an annual traffic capacity of about 53 million tons. The Iron Gates I retention reservoir has a water surface of about 133 km2, the water volume varying between 2.83 km3 at a water level of 70 metres and 1.35 km3 at a level of 63 metres (the levels refer to the Black Sea Sulina reference system). At high water level, the backwater created by the dam extends upstream beyond the confluence of the Tisza river with the Danube (1,220 kilometres from the Black Sea).
About 80 kilometres downstream, the second Iron Gates system was built and started operation in December 1984. The hydropower station of Iron Gates II provides a total installed power of 540 MW at a design water discharge of 6800 m3s-1 and a water head of 10.3 metres. The annual production of electric power of the hydropower station Iron Gates II reaches 2,610 GWh. The retention reservoir has a surface of about 63.25 km2 and a total water volume of about 0.425 km3.
The third large hydropower system is located at Gabcikovo, near Bratislava, and provides some 10% of Slovak Republic electricity.
As early as the seventh century BC, Greeks reached the Black Sea coast, the Danube Delta and the lower Danube, calling it Istros. The oldest description of the Danube, of its Delta and the Black Sea, is provided in the fifth century BC by Herodotus in his Histories. In the second century BC, Claudius Ptolemaeus (Ptolemy) gave valuable information on the Danube and its mouths in his Geographic Guidebook or Geographia. Coordinates of many geographic points, such as bifurcations of channels, river mouths and ancient cities, and measurements of the distances between these points are provided in this work.
Romans succeeded the Greeks along the Black Sea coasts. They established the northern boundary of their empire along the Danubius. In the second century AD, they built a bridge across the Danube at Drobeta (very close to the Iron Gates), conquered Dacia and expanded the influence of the Roman Empire north of the river.
The river continued to play an important political and economical role in the Middle Ages. During the 14th and 15th centuries, the Ottoman Empire spread to South-Eastern and Central Europe, relying on the course of the River Danube as a natural defence line, reinforced by a string of fortresses built along it. The Austro-Hungarian Empire recognised the navigational potential of the Danube and this was the starting point for better mapping and assessment of the river. Illustrations and maps of the Danube became numerous and the first printed map was drawn by N Vischer in Amsterdam in 1640.
The Austro-Turkish treaty, signed in 1616, allowed Austrian navigation along the middle and lower Danube, and Russia conquered the right to navigate the lower Danube after 1774. The Anglo-Austrian and the Russian-Austrian conventions of 1838 and 1840 declared navigation free along the entire river. After the Crimean War, the Paris Treaty of 1856 set up the first Danube Commission as an international body in charge of the supervision of the river as an international waterway. An impressive number of maps and descriptions date from the 17th and 18th centuries. Since the 19th century, Russian, English, Austro-Hungarian and especially Danube Commission maps and studies marked an important improvement in the knowledge and illustration of the River Danube and its Delta.
In 1921 and 1923, the Statute of the River and the establishment of the International Danube Commission were approved by Austria, Germany, Yugoslavia, Bulgaria, Romania, Great Britain, Italy, Belgium, Czechoslovakia, Hungary and Greece.
During the Second World War, free navigation was interrupted again until 1948 when a new European Danube Convention was signed and the Danube Commission reconstituted.
International legal frameworks, agreements and programmes
As an international river crossing Europe from west to east, sharing its waters with ten countries, carrying downstream its load of anthropogenic waste and bearing responsibility for the environmental state of its own wetlands (including its delta) and of the Black Sea, the Danube requires joint multilateral co-operation for protection and sustainable integrated management.The main legal instruments for conducting the environmental rescue and sustainable management of the River Danube/Black Sea system are as follows:
- Danube Navigation Convention (Belgrade Convention, signed in 1948) regulates the international navigation on the Danube River and includes certain water pollution control measures;
- Convention on Wetlands of International Importance, especially as Wildfowl Habitat (Ramsar Convention), signed in 1971;
- Convention on the Protection and Use of Transboundary Watercourses and International Lakes (Helsinki Convention 1992) - provides a framework for co-operation on transboundary water quality and use problems;
- The Environmental Programme for the Danube River Basin (EPDRB) was established in Sofia in September 1991 by the Danubian countries, donors and international finance institutions, G-24 countries and NGOs. A Task Force was established in Brussels in February 1992 and a first Programme Work Plan was endorsed. Phase I focused on the institutional building and on the development of a Strategic Action Plan (SAP). The SAP was approved through the Danube River Basin Environmental Declaration in 1994 in Bucharest. The development was mostly supported by PHARE/TACIS and by the United Nations Development Programme/Global Environment Facility (UNDP/GEF);
- Convention on Biological Diversity, signed in 1992 by the European Union (EU) and some other 80 countries;
- The Danube River Protection Convention (DRPC), signed in Sofia (June 1994) and entered into force from October 1998. The Convention is designed for basin-wide co-operation with transboundary relevance focusing on pollution prevention, control and reduction. The implementation of DRPC is realised by the International Commission for Protection of the Danube River (ICPDR). DRPC through the ICPDR is able to join the objectives and requirements deriving from the EU Water Framework Directive (EU/WFD);
- Convention on the Protection of the Black Sea (CPBS) against Pollution signed in 1992 at Bucharest which came into force in 1994;
- Declaration on the Protection of the Black Sea (Odessa Declaration - 1993) formulates the principles stated by the CPBS, the goals and the priorities and actions to be taken in order to rehabilitate and protect the Black Sea. Both the Bucharest Convention and the Odessa Declaration are also dealing with the influence of the Danube on the environmental state of the Black Sea;
- The Black Sea Environmental Programme (1993-1996) and the Strategic Action Plan for the Rehabilitation and Protection of the Black Sea, signed in October 1996. The Black Sea Action Plan states that "… it is imperative that strategies for the reduction of nutrients be adopted for this river. The provisions in the Danube Strategic Action Plan (maintenance of 1995 levels) clearly are insufficient for addressing the eutrophication problem in the Black Sea";
- Environmental Action Programme for Central and Eastern Europe (EAP), endorsed in 1993 at ministerial level, represents a wide consensus on environmental reconstruction and sustainable development.
Religion, Science and the Environment
Symposium III, "Religion, Science and the Environment: Danube - River of Life" was dedicated to highlighting the environmental, socio-economic and political problems of the Danube macro-system: delta, coastal zone, Black Sea. The present book is the expression of common, synergetic efforts of Religion and Science to save the macro-system, to improve the political, socio-economical and ecological state of the Danube and the entire region, including the riparian countries, and to save and reinforce the peace of humankind.
Almazov A.A., Bondar C., Diaconu C., Ghederim Veturia, Mihailov A.N., Mita P., Nichiforov I.D., Rai I.A., Rodionov N.A., Stanescu S., Stanescu V., Vaghin N.F., 1963 - Zona de vγrsare a Dunγrii. Morfografie hidrologicγ: 396 p., Ed. Tehnicγ, Bucharest.
Bondar C., State I., Cernea D., Elena Harabagiu, 1991 - Water flow and sediment transport of the Danube at its outlet into the Black Sea. Meteorology and Hydrology, 21, 1: 21-25, Bucharest.
Cviji? J., 1908. Entwicklungsgeschichte des Eisernen Tores. Peterm.Mitt.Erganzungsheft, 100, p.1-64, Gotha.
Gαbris G., 1994. Pleistocene evolution of the Danube in the Carpathian Basin. Terra Nova, 6, p.495-501.
Marovi? M., Grubi? A., Djokovi? I., Tolji? M., Vojvodi? V., 1997. The genesis of Djerdap Gorge.
In: Intern.Symp. - Geology in the Danube Gorges, p.99-104, Belgade-Bucharest.
Marovi? M., Grubi? A., Djokovi? I., Tolji? M., Vojvodi? V., 1997. The neoalpine tectonic pattern
of Djerdap Region. In: Intern.Symp. - Geology in the Danube Gorges, p.111-115, Belgade-Bucharest.
Posea Gr., 1964. Defileul Dunγrii. Natura, seria Geogr.-Geol.,XVI, 1, p. 45-49, Bucharest.
Stancik A., Jovanovic S. et al., 1988 - Hydrology of the river Danube. Priroda Publ. House: 271 p. Bratislava.
Strategic Action Plan for the Danube River Basin 1995-2005, Revision 1999. Programme Coord.Unit, UNDP/GEF Assistance, 159 pp, Vienna.