At the corner of the C. Fockstraat and Spoorsingel you can see one of the 210 locations in Delft where the groundwater level is continuously measured. The groundwater monitoring station is located underneath the square lid (which is labeled ‘peilbuis’, literally translated as ‘level tube’). This was originally installed in 1970 and since it was upgraded in 2014, it provides continuous measurements of the groundwater level. The city of Delft uses this information to know how much rainwater can safely be stored below ground. More generally, monitoring the groundwater is useful for knowing if the groundwater level is too high (which can cause problems such as damp basements and moisture damage to buildings) or too low (which can cause trees and other plants to wilt and die). In order to monitor the groundwater level, the city and the Water Board Delfland have installed 210 groundwater monitoring stations (‘wells’) throughout Delft.

Groundwater monitoring in and around Delft

Most of the 210 wells extend about two metres into the ground and measure the shallow groundwater level. This is the groundwater level slightly below ground level (street level), which you will encounter if you dig a hole in the ground. There are also wells that measure the deep groundwater level; these wells extend to the pleistocene sand layer. They actually measure the water pressure in that layer. Here you can read how this happens.

There are many groundwater level monitoring wells in Delft and the surrounding area.

You can follow the trends of the groundwater level in your area for over the past 10 years, via this website. Below you see an example of the groundwater level in relation to NAP (National water reference level) at the corner of the Spoorsingel and the C. Fockstraat. The ground level here is 26 cm above NAP. You can see that the groundwater here is about a meter below that ground level. You can also see two large outliers. The groundwater monitoring well was probably broken at that time.

The groundwater level shows a cyclical behaviour. If you look closely you will see that the groundwater level is low at the end of summer and high at the end of winter – this is of course caused by the variation in precipitation over the seasons.

Groundwater level variation compared to NAP since 2013 at the corner of C. Fockstraat and Spoorsingel.

Here you can read what groundwater is, and here what the effect is of the former groundwater extraction by DSM, which is now being phased out.

Read more about the groundwater monitoring stations, zoom in on Delft, measuring point PB 1.01 (Spoorsingel 72).