In 2003, Germany opened a water-filled bridge that lets cargo ships cross over the Elbe River; the 3,012-foot crossing connected two major canals

A ship floating along the river, but not on it, sounds like the setup to a conundrum. That's precisely what happens every day near the German city of Magdeburg, where the Magdeburg Water Bridge carries barges and cargo vessels above the Elbe River in a concrete trough of water. The German Federal Waterways and Shipping Administration (GDWS) says the structure is 918 meters (roughly 3,012 feet) long and is Europe's longest navigable canal bridge. The bridge carries artificial waterways over the river, allowing freight traffic to continue uninterrupted.

Why a bridge over a river was even needed

Germany's inland waterways are served by two main routes: the east-west Mittelland Canal and the Elbe-Havel Canal leading to Berlin. However, the Elbe River flows straight through their path, and it's at a lower level than both canals. Before 2003, boats heading for Berlin had to leave the canal, descend to the Elbe via locks, proceed several miles upriver, and then climb back up the canal system. Shallow Elbe waters during dry periods made it impossible for heavily laden barges to make the journey. Vessels were forced to lighten their cargo, or wait for rains before they could proceed. The lack of a direct link between the two waterways had frustrated planners since the early 1900s. According to the city of Magdeburg, construction of a connecting canal began before World War II and stopped in 1942 as the conflict drained resources and the workforce. Until Germany's division, there was little motivation to complete the east-west route, and the half-built piers were left to languish.

How the water bridge actually solved it

Since Germany was reunited in 1990, reconnecting the eastern and western waterways has become a priority once again. Construction began in 1997 under the overall name Verkehrsprojekt Deutsche Einheit Nr. 17. To avoid the drop down the Elbe, the engineers decided to build a concrete trough that would carry water from the canal, forming a bridge over the river. This way, ships could pass through without entering the Elbe. The trough holds several meters of water, enough for loaded vessels to pass through it, GDWS says. However, on the German side of the river, the Rothensee and Hohenwarthe double locks allow ships to reach the bridge and the rest of the canal system. German authorities call this whole system the Magdeburg Water Bridge, and it is not a bridge in the usual sense. The water bridge opened for navigation on October 10, 2003, thus ending the long era of waterways being disconnected by the Elbe.

What this means for how Germany moves goods

Ships traveling between the industrial Rhineland and Berlin are no longer limited by seasonal changes in the river's depth. By eliminating a bottleneck, the bridge lets manufacturers and shippers keep moving heavy goods along the canal system year-round, regardless of the Elbe's water level, a less expensive alternative to trucks. The crossing eliminated the detour ships once took down into the Elbe and back up through the canal locks, a route that depended on the river's depth and added extra distance. Germany's solution to this topographic problem was ingenious but not unique. Other countries have also built artificial water lifts to help navigate over obstacles. Europe has some small, historic navigable aqueducts, but none have the capacity to handle the huge commercial traffic of the Magdeburg crossing.

A structure built to be used, not just seen

Today, 23 years after its opening, the GDWS is still described as an important engineering achievement, and the city of Magdeburg hosts visitors who come to see the bridge. Its unusual design attracts visitors who come to watch cargo ships pass over the river in a water-filled trough. After all, the next time someone sees a ship heading to Berlin from a port on the German side, it may be traveling over the river in the canal above.