Better understanding of the salinisation of Dutch groundwater

Published: 9 October 2020

In the Dutch coastal provinces, the groundwater is already brackish to saline at a shallow depth. That can lead to problems if we want to use the groundwater to produce drinking water, for industrial processes or for agriculture. Fresh groundwater stocks are also under pressure from climate change, including sea level rise. That makes it important for government authorities, industry and drinking water companies to have a clear picture of the location of fresh groundwater resources, how much we can extract sustainably, and how these stocks will develop in the future.

Deltares has worked with Arcadis on a new model for calculating the salinity of groundwater in the Netherlands on behalf of Rijkswaterstaat, provincial authorities, water authorities and drinking water companies. The model has now been included in the Dutch Hydrological Instruments.

All kinds of measurements provide us with a clear picture of groundwater salinity. But we cannot measure everywhere and measurements are particularly scarce at greater depth. The innovative interpolation method used here provides an overview of the current salinity of Dutch groundwater. In addition to the absolute values for salinity, we also provide information for the first time about the level of certainty of those values. The new three-dimensional visualisation can be seen on NHI website. The file can be downloaded from the NHI data portal.

NHI fresh-salt groundwater concentration

High resolution makes this unique

Groundwater is constantly on the move. Due to the draining of polders over the course of centuries, salt groundwater is still flowing to the surface. Salinisation may increase as a result of climate change and sea level rise. The new model for the whole of the Netherlands now makes it possible to simulate this flow of fresh and salt groundwater in different land use and climate scenarios. In that way, we can study how the salinisation of our fresh groundwater supplies will develop in the coming century and how we can respond. The high resolution of the model on the national scale is unique in the world. Moreover, by using new innovative parallel numerical calculation techniques, we can complete the calculations for many scenarios faster than ever before.