The subsurface of much of the Netherlands comprises unconsolidated strata to depths of hundreds of metres and is thus exceptional in Europe. The strata contain water. This groundwater is located in the pore spaces between the solid particles such as sand grains, and in the deeper openings, such as fissures in the solid rock. To understand groundwater issues (availability of water, groundwater quality, etc.) knowledge about the quantity and quality of the groundwater is needed. That knowledge is not self-evident, since groundwater evades our direct observation almost everywhere. Only groundwater escaping in the form of “seepage” makes itself visible to us in a natural way. For all other observations of groundwater, we first have to intervene.
An example of such an intervention is the placing of an observation well with a filter that allows groundwater from the saturated part of the subsurface to flow into the measuring tubes. This allows the groundwater level to be measured and samples to be taken. These filters are also placed in other monitoring tubes, field drains, fire hydrants and large-diameter wells. Our country has an extensive network of measuring points that goes back a long time. This monitoring network fulfils the great need for detailed information about the Dutch subsurface, a need that is connected with the highly varied properties of our soil and shallow subsurface, the specific lack of space and the substantial population density in our country.
TNO has had a national databank of information on the groundwater and subsurface for more than fifty years. The databank contains all the data on groundwater, such as information about the location and depth of observation wells, administrative data and results of groundwater readings. In total, DINO has more than a hundred million groundwater readings measured in around twenty-three thousand monitoring wells all over the country. Provinces, water utility companies, water boards and engineering firms are among those that frequently consult the groundwater data in DINO.