The Danube River has been used as an important means of transportation of soldiers for nearly 2，000 years. In the 200s， the river was the northern border of the Roman Empire， and Roman soldiers no doubt used the river. Years later， the Goths， Slavs， Huns， and other Germanic tribestribe n.部落， 部族 used the Danube to cross into the Roman Empire. Later， the Danube was used to gain access to Constantinople. The Crusaders used the Danube to travel faster on their quest to regain the Holy Land. Towards the end of the Middle Ages， the Ottoman Turks used the Danube for easier advancementadvancement n.前进， 进步 into western and central Europe.
Both the commercial and military value of the Danube are still recognized today. Many treaties have been signed to try to keep one country from having too much control of it. In the early part of the 19th century， the Danube served as a link between the industrial area of Germany and farmland of the Balkans. At this time， the Ottoman Empire was weakening， but the Russian Empire was near the height of its power. Austria and other powerful European nations recognized this threat to the area and were able to prevent Russia from gaining the Danube delta.
The Treaty of Paris signed in 1856 ended the Crimean War. The terms of this treatytreaty n.条约， 谈判 ordered that a European commission be set up to control the Danube delta. The commission made changes to the delta to make it better for commercial traffic. In 1890， Austria began a series of improvements to the delta. These improvements were known as the Iron Gate.
World War I was officially ended by the Treaty of Versailles which was signed in 1919. The European commission was confirmed in this treaty. Another commission was then set up to control the Danube above the delta.
Ever since World War II， the Danube has been hard to control. Nazi Germany took control of the whole river from 1940 until 1944. When World War II was over， the Communist Bloc created their own commission over the delta. In the earlier part of the 1990s， Slovakia diverted the Danube to bring more water to a hydroelectric plant. This caused a heated disputedispute v.争论， 辩论， 怀疑， 抗拒， 阻止， 争夺(土地，胜利等） n.争论， 辩论， 争吵 with Hungary which has been only somewhat settled.
The hydroelectric plant that caused this problem is called the Gabcikova Dam. It is located in southern Slovokia. The dam was a joint project funded by the governments of Czechoslovakia， Hungary， and Austria. Hungary and Austria pulled out of the project when they received pressure from different environmental groups.
During this time， Czechoslovakia was separated into the Czech Republic and Slovakia. The Czech Republic withdrew from the arrangement， but Slovakia decided to proceed and build the dam.
This diverted the flow of the Danube to the north. Hungary demanded that the boundary between it and Slovakia be redrawn to reflect the diversiondiversion n.转移， 转换， 牵制， 解闷， 娱乐. Instead， Slovakia agreed to allow more of the water to flow into Hungary.
One may ask why the Danube is so important. The answer to this question is twofold. The first part of the answer is its use for commercial and military transportation. The second part of the answer is the location of the Danube.
The Danube flows through the countries of Germany， Austria， Slovakia， Hungary， Serbia， Croatia， Bosnia and Herzegovina， Slovenia， Bulgaria， Romania， and the Ukraine. There are many important cities that the Danube flows through. They include Vienna， Budapest， Bratislava， and Belgrade. With the aid of canals， the Danube is connected to the Main， Oder， and Rhine Rivers. This waterway connects the North and Black Seas. For commercial transportation， the Danube is extremely valuable.
In addition to the Danube，s importance as a waterway， the Danube also is called home by many species of plant and animal life. This plant and animal life is also referred to as the flora and fauna， respectively. The Danube River basin is the longest marshlandmarshland n. 沼泽地 in Europe. It contains the greatest stretch of Reedbeds in the world. In fact， these plants dominatedominate v.支配， 占优势 the plant life of this marsh. In the delta， 1，700 sq. kilometers is covered with Reedbeds. This only leaves about 150 sq. kilometers that is not covered by Reedbeds.
Reedbeds are not the only type of vegetationvegetation n.［植］植被， (总称)植物、草木， (植物的)生长、呆板单调的生活 found along the Danube River. There are many different species of water lilies. Sandy areas along the river are covered with a grass called Stippa. There are also many forests along the Danube. They all contain their own plant life as well. In the Letea Forest， there are dunes that are 250 meters wide and 10 meters long. There are trees coupled in with these dunes that reach the height of 35 meters. This forest is also home to many rare species of plant life.
There are also many different types of animal life. There are over 300 species of birds. A large percentage of the world wide population of these species live in area of the Danube basin. The Danube delta is a very important area for fish. Over 45 species of freshwater fish live in the lakes formed by the delta. One of these species， the Acipensednidae， is endangeredendangered adj.（生命等）有危险的，有灭绝危险的，将要绝种的.
The Danube River also has an unique cultural heritage. Its history can be traced to the remains of Greek and Roman trade settlement built in the area. Modern villages and cities show a Turkish flair in their design. Unfortunately， many of these communities have been struck with disease， the most pervasive one being Cholera.
The climate of the area is rather dry. It only receives about 450 millimeters of rainfall per year. However， this number varies depending on the closeness of the sea and a myriad of inland lakes and waterways.