Land Reclamation in the Netherlands since 1300.
How much of the Netherlands is below sea-level?
But this is not the only problem in the Netherlands. There are many rivers in the country.
The rivers discharge by gravitation at low tide. At high tide, the water level in the rivers rises due to a decrease in discharge. The water level at the river estuaries is at sea level. The waterways that are below sea level are the large drainage systems that are only joined with the main rivers with inlets, locks, and pumping stations. Large pumping stations (like the one in Katwijk) have a pumping capability that is high enough to drain the inland waterways called boezem to the wanted water level (at Katwijk about -0.61 meters below mean sea level). The deep polders (at about 5 meters below mean sea level) discharge water from those territories on the boezem with smaller pumping stations.
Pumps, for example, every raindrop that falls in Flevoland (the sizeable human-made island in the heart of the Netherlands), has to be pumped out.
Approximate numbers: 750mm of rain, of which 500mm evaporates, that’s 250mm of pumping, or 250 liters/ m2, or 250.000 m3 / km2, Flevopolder is 970 square km, so each year 240 million cubic meters of water needs to be pumped out.
About all water that drops below sea level is pumped out, it often pumped to river/canals, which flow directly to the sea, but all of it is first pumped up.
Forth percent of the Netherlands is below sea level, so that would be 13600 km2 and 3,4 billion cubic meters of water every year. The Rhine runs with 2330 m3/sec, so it needs to flow 17 days to get 3,4 billion km3 of water (the Mississippi needs to flow 56 hours while the amazon can do it in under 5 hours).
– Land Reclamation in Monaco (1861 – 2024)