The Netherlands has no lack of water and the water infrastructure is highly developed. There are several large natural waterways — the rivers. Over time these natural waterways have been connected to each other by artificial water ways, canals. To manage the difference in water levels a normal height datum was developed to refer to different water levels: NAP, the Amsterdam Ordinance Level.
The Netherlands is situated at the mouth of the Rhine, Meuse and the smaller Scheldt rivers. These rivers are mainly rainfed, although a small volume is melting water from the Alps. Other smaller rivers that originate abroad but flow through the Netherlands are of trivial significance in comparison to these three.
Rhine- The Rhine, the most important river of the Netherlands, is both a glacial and rain-fed river. The indications ‘glacial’ and ‘rain-fed’ arise from the sources of the river: the Rhine is fed by both rainwater and melting ice from glaciers. It originates in Switzerland and runs through Germany and the Netherlands before exiting to the North Sea. In total, the Rhine is 1320 kilometers (820 mi) long. The discharge is on average 2200 m3 per second (78,000 cu ft/s), but its discharge can vary quite a bit over the range of a year. During an extreme event in 1995, the discharge increased to 13000 m3 per second (462,000 cu ft/s), while in 2003 the lowest discharge was only 800 m3 per second (28,000 cu ft/s). One of the characteristics of a rain river is that the variation between the highest and lowest output is larger than that of a glacial river. When it rains heavily, the output is high, and when it does not rain, the output is greatly reduced. The average glacier river however maintains a much more gradual drainage due to continuous melting. As the rainfall in winter is much higher than in summer, the highest water levels usually occur during winter.
After entering the Netherlands, the Rhine branches into three main rivers: the IJssel, the Nederrijn (Lower Rhine), and the Waal. The IJssel turns North, while the other two eventually join again and, together with the Meuse, reach Rotterdam. Parts of the Rhine have been canalized (i.e., made into canals) in order to improve the navigability of the river. Moreover, it ensures the water supply of the North of the Netherlands and, in particular, the IJssel Lake.
Meuse- The Meuse is a purely rain-fed river and is considerably smaller than the Rhine. It rises in France and, flowing through Belgium and the Netherlands, it drains into the North Sea. Although not so small (925 km/ 575 mi long), its discharge is only 10 percent of the Rhine. The variation in water level, however, is much higher, since it is purely rain-fed.
Scheldt- Only the mouth of the river Scheldt lies within the Dutch border. The river connects the second largest port of Europe, Antwerp, in Belgium, with the North Sea. When designing the Delta Plan after the flood of 1953, the primary reason not to dam the Westerschelde (literally, “Western Scheldt”) was to maintain accessibility to the port of Antwerp because of the port’s worth to Belgium’s economy.
At least 36 major canals were dug in the Netherlands, mostly to improve accessibility to the different ports and connect them to the major rivers. The Amsterdam-Rhine canal, for example, is a canal of 72 kilometers (45 mi) that connects Amsterdam with the Rhine, and thus with the industrial areas of Germany. Another example is the Juliana canal (named after Queen Juliana), which provides a bypass for a particularly un-navigable part of the Meuse. The Nieuwe Waterweg (New Water Way) is the canal that opened the connection between Rotterdam and the sea to larger ships. For this large project vast dunes had to be dug out to open the entrance to the sea.
Normaal Amsterdams Peil (NAP), Amsterdam Ordinance Level, finds its origin in ships coming to and from the port at Amsterdam. The ships had to pass through a sluice to get past the dam in the Amstel River (which is where Amsterdam derives its name from). During high tide, however, the water level outside the city would rise above the water level inside the city. To prevent flooding the operator would close the sluice. The water level was marked by a bench mark, which is the origin of NAP. In 1683 an official touchstone for NAP was set up, which can still be seen in Amsterdam.
The first time this datum is mentioned in historical literature is in 1673. In 1818 the NAP was established as a nationalized reference point. In 1879 Germany also adopted NAP, although they called it “Normal Null.” Sweden and Austria soon followed. Both in 1955 and in 1973 the NAP was chosen as reference for the common European standard for water levels, in an effort to standardize the water level references in Europe. Most European countries still have their own reference points related to average sea levels of the Black Sea, Mediterranean, North Sea, Atlantic Ocean and the like. The NAP is close to mean sea level at the Dutch coast. It remains to be seen if NAP will survive as a reference point, with the modern technologies making it possible to calculate the average sea water level worldwide, which might make more intuitive to use as a reference point for future international standards.