ABSTRACT
We felt it essential to describe these canals in a separate chapter because they possess certain characteristics that set them apart from other types. While all other canals are dimensioned to carry a given rate of water flow that is necessary for the irrigation of a specific area, to supply drinking water to a population centre, to supply water to a hydroelectric plant for electrical power generation or for the transport of drainage water to a given point, etc., navigation canals require dimensions that are sufficiently large, together with a slow enough water speed to permit navigation along them. It is, of course, required that the canal connects the points that are to be linked for the traffic of goods. Not all countries or even regions have made equal use of navigation
canals. Whereas in Central Europe, including France and England, artificial canal navigation has been very frequent, and also along rivers, in general, optimum conditions for such use have not been available in Spain. This is in spite of the interest shown by its monarchs and governors throughout history. In fact, only two navigation canals have really been constructed, both of which are no longer employed for this purpose: The Castilla Canal and the Imperial Canal of Aragon (Figure 13.1). Both were put into service during the second half of the eighteenth century. On the other hand, in other countries, goods transport by rivers and artificial canals has been extremely useful because of the lower costs involved, together with increased capacity, which was previously much higher than any other method. The power requirements for goods transportation along navigation canals
is approximately one-sixth of that for roadway movement. In some situations, navigation canals were converted for irrigation pur-
poses, as in the cases of the two mentioned Spanish canals, but, throughout the world, there are still many in operation and interest continues with the construction of new ones under favourable circumstances. These may combined with other uses, producing
multi-purpose canals, which is why we felt that we could not possibly omit them from a book dealing with canals. In this respect, mention must be made of the Danube-Main Canal, which was completed in 1992, 171 km long, with sixteen locks, each 200m long, which links the Danube and the Rhine rivers for navigation, so that shipping from the Black Sea can reach the North Sea.
