Polders and reservoirs
Polders are areas - often lakes - that have been artificially drained. Because the ground level in polders is lower than the surrounding land, rain and seeping water have to be removed by mechanical means. Initially windmills were used, later steam powered pumping stations, and still later diesel or electric powered pumping stations, the latter fully automated.
Water pumped out of the polders first enters a water deposit or reservoir. This consists of a system of interconnected lakes, canals, rivers, ditches, etc.; in Dutch it is called "boezem". The larger the area of the system, the larger its storage capacity. From the reservoir the water is subsequently pumped to sea by other pumping stations.
Polder pumping stations keep polders drained, reservoir pumping stations keep the reservoir at level. Some pumping stations were built with the sole purpose of draining a lake, serve as a polder pumping station for some time, and subsequently be demolished. An example of these is the Cruquius, one of the three pumping stations that drained the Haarlemmermeer. Fortunately the Cruquius has been saved from demolition, and its original steam engine from 1849 can still be seen, but it can't run on steam anymore.
Steam pumping station Halfweg (1852) was a reservoir pumping station ("boezemgemaal" in Dutch). To cover the large reservoir area, comprising around 200 polders and lakes, pumping stations were built in Spaarndam, Halfweg, Gouda and Katwijk. Steam pumping station Halfweg too has been saved from demolition. And although it no longer serves to regulate the water level, some 12 days per year the boiler is fired again, the hissing of steam can be heard again, and the pumping station with its huge scoop wheels runs on steam again. But even when it's not running on steam, visitors can enjoy the museum and the sight of the beautiful and impressive machinery. Steam pumping station Halfweg is a Routepoint of The HollandRoute, part of the "European Route of Industrial Heritage (ERIH)" network.