Outer Delft Water Walk
We walk all the way down Noordeindseweg to the pumping station of the Polder van Biesland, about 800 meters, to the truncated windmill. You can also walk on the footpath through the woods, parallel to Noordeindseweg.
Behind the mill, to the northeast, we see the Biesland Polder, with the organic care farm Hoeve Biesland. The farm shop is open daily, except Sundays, from 10:00 AM to 5:00 PM. This polder is very low, also compared to its surroundings, with a summer water level of -5.1 m NAP and a winter water level of -5.4 m NAP. This is due to intensive peat extraction in the past. This polder can only be drained via the Bieslandse Molenvaart, another Binnenboezem with a target water level of -2.14 m NAP. If the polder level is too high, the Biesland Polder pumping station pumps water to the Bieslandse Molenvaart, and then the Bieslandse Bovenpolder pumping station pumps the excess water to the Boezem (stop 7). To achieve this, the pumping station was renovated in 2018 and now has a capacity of 26 m³/min.
In the event of a water shortage, water from the Boezem is released via the Bieslandse Molenvaart canal by opening weirs in the pumping stations. Thus the water in this Binneboezem (the Bieslandse Molenvaart) can flow in two directions, unlike the Binneboezem water from the Tweemolentjesvaart and the Nootdorpse Plassen, which always flows into the polder (or is stagnant).
The “pump volute” is the heart of a pumping station.
Opposite the mill you can see the “pump volute” of the old pump, the heart of a pumping station.
The Bieslands mill around 1900 (from Mill database).
The mill was built in 1784 and pruned in 1931 because maintenance became too expensive. A centrifugal pump powered by a diesel generator was then installed. The pruned mill is now a residence where the former pumping station operator, Jan de Bruyn, lives with his wife. Jan learned to catch moles as a child and still does so as a sideline. Jan is also a clockmaker.
