How do you get the water level up again when you've emptied the lock so as to bring the boats down?
The natural flow from above serves to refill the lock. No water is pumped up. In Västergötland it's Lake Viken that tops up the Canal, while in Östergötland the water comes from Lake Vättern. The Canal also goes through other lakes that act as water reservoirs.

Why dig a Canal when there were natural watercourses nearby?
In the natural watercourses, too, they would have been obliged to locks. It's much harder both to build and to repair locks if you have to dam up natural watercourses. Natural waterways are also subject to wide variations in water level, which creates problems, particularly at the locks.

Why did they dig the Canal so crooked?
They followed the natural contour line, so that they could use one side as the "wall". That meant that they only needed to build a bank on one side of the Canal.
How much water does a lock hold?
It varies a bit, because the depth isn't the same in all locks. The reason is that the height differences vary. A "normal" lock is customarily taken to hold about 750 cubic metres of water. (1 m3 = 1,000 litres)

The Significance of the Canal
The rise of modern manufacturing industry in Sweden is probably the most significant consequence that the Canal has had for the country. The manufactory of Motala Verkstad was where budding engineers and foremen received their training in the new production methods. It developed a large body of know-how in the casting of iron, from which Sweden benefited. Along the way, Motala grew to be a modern industrial town. Karlsborg Fortress is seen as a direct outcome from the building of the Canal. When Sweden lost Finland in 1809, it was generally felt that Stockholm was too unprotected, situated as it was close to enemy territory. The things that would need to be protected in the event of war - armaments, gold, the royal family, the government and so on - would be safer in a strong, inland fortress. It was the Canal that made it possible to transport them there.

It took nearly a hundred years to build Karlsborg Fortress, 1820-1909, but even so, it was never quite finished and was never called upon to serve its original purpose. During the Second World War the Swedish gold reserve was stored there. Today, the Fortress is the base for the Household Cavalry Hussars, K3, the Paratroop School and the Defence Department's Survival School. Besides the defence facilities there are civilian residences, shops, a café and a museum within the grounds of the Fortress. The Canal is today one of Sweden's strongest touristic assets.

Smart solutions
When you probe into how the Canal was built it's impressive to see the ingenious yet simple ways in which various problems have been solved. Take the stem ports for example. These are ports which always stand open at several points on the Canal. They serve two purposes. Should a cave-in occur in the Canal the stem ports are supposed to close automatically in response to the water suction. The result is that only a short stretch is emptied and the accident can be kept to a minimum. Proof that it works came in 1847 when the high bank burst at Venneberga. Only 100 metres away, the stem port slammed shut. The other purpose is to enable short stretches of the Canal to be emptied for repairs.
In constructing the Canal the builders were forced to cross both streams and larger watercourses. They didn't want to get this water into the Canal. For one thing, it would make it hard to control the water level. At the time of the spring flood the basins at the locks would fill up very fast indeed. For another, the water would bring with it great quantities of silt, which would make the Canal too shallow. Accordingly, there is an impressive system of side-ditches and stone-lined culverts beneath the Canal which carry the water away to other channels. Some of the culverts are as high as a man.

Opening a port
To enable the ports to be opened the water level must be exactly the same on both sides of them. A difference of only five centimetres would impose excessive stresses on the ports and cause damage. The basins are filled through sluices, which are opened upwards, in the ports. The very first ports were opened with the aid of large booms that were pushed forward. You can see specimens in the upper port at Klämman. By as early as 1847, all ports in Östergötland had been fitted with toothed drives, which considerably simplified the work. The lower port at Klämman has them. They are also to be seen in the locks of Borensberg and Tåtorp. By 1969 it was time to modernize the ports again. Electric motors were fitted onto the draw-boom on the seven-stage locks at Berg and elsewhere. Nine years later, the engineers began introducing hydraulics, and since 1988 pretty well all the locks have been powered hydraulically.

Casting a port
To begin with, all ports were made of wood or of cast-iron with wooden planking. During the 1970s a number of them were exchanged for welded steel ports, which are now being replaced by cast-iron ports. The dimensions of the ports vary, but building new foundry patterns for every port would be far too costly. Instead, an attempt is now being made to build patterns using one-decimetre gauge blocks. The patterns are manufactured by a woodworking shop in Kristinehamn and the ports are cast in Mölltorp. The cost runs to about half a million kronor per par.