The Schermer Drainage Mills: How Fifty Windmills Emptied a Lake
In the summer of 1635, one of the great lakes of North Holland simply ceased to exist. The Schermeer, a broad body of water lying between the town of Alkmaar and the already-drained Beemster, had been pumped dry by a coordinated network of around fifty windmills — one of the largest concentrations of drainage mills ever assembled for a single project. The water they lifted, stage by stage, out of the lake basin left behind a floor of clay several metres below sea level. That floor became the Schermer polder, and it has remained dry farmland for nearly four centuries, guarded first by its mills and later by the pumping stations that replaced them.
A lake made by peat and storms
The Schermeer was not an ancient lake. Like most of the large inland waters of North Holland, it grew out of human hands and bad weather. For centuries, the peat bogs of the region had been cut and dug for fuel, leaving the land surface lower, wetter and more fragile. Storm floods then did the rest: wind-driven water gnawed at the soft peat banks, and small ponds merged into ever larger lakes. By the sixteenth century the Schermeer had swallowed a wide swathe of former peatland and was still growing, eating away at the shores of villages such as Schermerhorn, which sat on a ridge of higher ground between the Schermeer and the Beemster.
For the people living around it, the lake was a double-edged presence. It offered fishing, reed cutting and shipping routes, but every winter storm pushed its waves closer to farms and churchyards. A growing lake in a densely settled landscape was, in the long run, a threat that could not be ignored — and in the Dutch Republic of the early seventeenth century, threats of this kind had begun to look like business opportunities.
Land as an investment: the reclamation boom
The Schermer was drained at the tail end of a remarkable wave of lake reclamations in North Holland. The Beemster had been pumped dry in 1612, followed by the Purmer, the Wormer and the Heerhugowaard in the decades after. Each project followed a similar pattern: wealthy investors — merchants, regents and officeholders from cities such as Amsterdam and Alkmaar — formed a company, obtained a charter from the States of Holland, and put up the enormous capital needed for dikes, canals and mills. Their reward was the new land itself, divided into lots and sold or leased as farmland.
Engineers of the era, most famously Jan Adriaanszoon Leeghwater with the Beemster, had shown that even deep lakes could be conquered if enough mills worked together. When the Schermer's turn came in the 1630s, the method was well rehearsed. First a ring dike was thrown up around the entire lake, with a ring canal — the ringvaart — dug along its outside. The canal served both as a shipping route and as the reservoir into which the mills would discharge the lake water. Only when the ring was closed could the real pumping begin.
Fifty mills in relay: the staged pumping system
The central problem of the Schermer was depth. The bottom of the lake lay several metres below the level of the surrounding waterways, far more than any single windmill could manage. A drainage mill of the period lifted water with a scoop wheel, essentially a paddle wheel turning in a close-fitting masonry trough, and a scoop wheel can only raise water a limited height — roughly a metre to a metre and a half at best. Pumping the Schermer in one lift was physically impossible.
The solution was the molengang, the mill gang: mills arranged in series, each lifting the water one step higher. A lower mill raised water from the lake bed into an intermediate basin; the next mill lifted it from that basin to a higher one; an upper mill finally discharged it into the ring canal. Around fifty mills were built and organised into such relays around the polder. From the ring canal, the water flowed into the regional storage network of canals and lakes known as the boezem, and from there it was released to the sea through sluices when the tide stood low. It was a cascade of coordinated lifts, powered entirely by wind, and it worked: within about two years of the mills starting work, the lake bed fell dry in 1635.
The binnenkruier: North Holland's inside winder
The mills that drained the Schermer belonged to a type characteristic of North Holland: the binnenkruier, or inside winder. These are large octagonal smock mills, their wooden frames covered with thatch, standing on low brick bases beside the water they had to move. What sets them apart is how the cap is turned to face the wind. In most Dutch mills the miller winds the cap from outside, using a tailpole or an external gallery. In a binnenkruier the entire operation happens inside: the miller climbs into the cap and turns it with a winch mechanism from within the mill itself.
Below the cap, the machinery followed a robust and well-proven logic. The sails drove a brake wheel, which transferred power down a massive upright shaft to the pit wheel and the scoop wheel at the base. Later, some North Holland polder mills were fitted with an Archimedean screw instead of a scoop wheel, which could lift water higher in a single stage. The mills were also homes: the miller and his family lived inside the octagonal body, among the beams and gears, with living quarters squeezed around the machinery. Tending a polder mill was not a trade with fixed hours — when the wind blew and the water stood high, the mill ran, day or night.
Keeping the polder dry: four centuries of maintenance
Draining the lake was only the beginning. A polder several metres below sea level collects water constantly — rain falls on it, and groundwater seeps in through the surrounding soil. The Schermer mills therefore did not retire in 1635; they settled into centuries of routine duty, pumping the surplus out of the polder's grid of ditches and back up into the ring canal. The new land itself was laid out with the geometric confidence typical of Golden Age reclamations: straight roads, rectangular parcels, farmsteads at regular intervals — a planned agricultural landscape drawn onto the old lake floor.
Along the ring canal stood another special group of mills, the strijkmolens, whose task was not to drain the polder itself but to move water from one level of the regional boezem to another, helping the whole storage system cope when water had to be shifted toward the sea. Together, polder mills and strijkmolens formed a single water machine spread across the landscape, managed by the local water authority and dependent on nothing more than wind, timber and constant human attention.
From fifty to eleven: decline and rescue
The wind machine met its match in the twentieth century, when mechanical pumping stations took over the polder's drainage. Once a motor-driven station could do the work of dozens of mills regardless of the weather, most of the Schermer's windmills lost their purpose. Many were demolished or dismantled in the decades that followed — the fate of thousands of mills across the Netherlands in the same period.
Yet the Schermer escaped total loss. Eleven of its mills still stand today, preserved as protected monuments and maintained by volunteer millers. Among them is the museum mill at Schermerhorn, where visitors can climb through the working machinery of a genuine seventeenth-century polder mill and see the scoop wheel, the living quarters and the inside winding gear at first hand. Nearby, a row of strijkmolens along the canal still shows how mills once stood in formation, ready to pass water from level to level. The surviving mills are kept in working order, and on windy days some of them still turn — no longer indispensable, but still able to do the job they were built for almost four hundred years ago.
Explore on the map
The Schermer's surviving mills stand close together in the open landscape north of Amsterdam, and they are easy to combine into a single visit — the museum mill at Schermerhorn makes a natural starting point. You can find each of them, along with thousands of other windmills across the Netherlands and the rest of the world, on our interactive map. Zoom in on the polder between Alkmaar and the Beemster, and the ring canal with its mills traces the outline of the lake that vanished in 1635.