In 793, the Emperor Charlemagne ordered the construction of a canal—the Fossa Carolina (German: Karlsgraben)—connecting the Swabian Rezat, a tributary of the Rednitz, to the Altmühl near Treuchtlingen.

This canal had a narrow channel, with many locks, and a shortage of water in the peak section, so the operation of the waterway soon became uneconomic—especially given the rapidly advancing construction of the railway network in the southern German countryside.

The canal finally was abandoned in 1950, after a decision was made to not repair damage it had suffered from Allied bombing during World War II.

To finance the waterway, the RMD was given control of the water resources of the Main, Danube, Lech, Altmühl, and Regnitz.

In 1966, the Duisburger Vertrag, an agreement between Bavaria and the Federal Republic of Germany, was reached for financing the completion of the project.

The length of the canal is 171 kilometres (106 mi); the summit elevation (between the Hilpoltstein and Bachhausen locks) is 406 metres (1,332 ft) above sea level.

[4] The height difference along the north ramp of the canal—from the Main at Bamberg to the crest elevation—is 175 metres (574 ft), with 11 locks.

Finally a pumped storage artificial lake Dürrlohsee that sits even higher in elevation than the summit pound makes up the difference if the aforementioned sources of water are not sufficient.

use kilometres (km) sea level (m) lock (m) There were different forecasts of freight transport volumes, from which benefit–cost ratio could be derived.

In 1981, a Federal Minister for Transport cost–benefit account assumed an estimated traffic volume of only 2.7 million tonnes per year for the Main-Danube Canal, and a benefit–cost ratio of 0.52:1.

One of the proponents commissioned a study by the Ifo-Institut München, predicting an estimated 5.5 million tonnes per year for the traffic volume on the Main-Danube Canal.

The Main-Danube Canal makes it possible for aquatic animals to spread from Western to Eastern Europe and vice versa.

In order to maintain navigable water levels for the waterway in the Main, Regnitz and Rednitz valleys, water must be diverted via the Altmühlüberleiter canal & tunnel from the upper Altmühl to the Brombachsee reservoirs, across the European Watershed between the drainage basins of the Danube and Rhine.

On the other hand, the canal carries cargo traffic that would otherwise require 250,000 truck trips annually, or as an alternative, 3,000 freight trains on the Deutsche Bahn rail network.

The force of the water was so great that it dug a 10-metre (33 ft) wide crater and swept away cars, people and houses.

The long-distance Challenge Roth triathlon, which is held annually in July, includes a 3.8-kilometre (2.4 mi) swim in the Main-Danube Canal at Hilpoltstein.