Temperature evolution in the shallow subsurface of the Netherlands

The Geological Survey of the Netherlands has extensively mapped the subsurface of the Netherlands, including a series of temperature measurements in the late 1970s and early 1980s. Over 500 temperature-depth profiles have been obtained in piezometers up to depths of few hundreds of meters. These nationally distributed measurements provide an important historical baseline relevant for drinking water quality, and subsurface energy systems. For this purpose, isothermal maps covering the Netherlands were produced for various depths.

Since these temperature-depth data were collected, substantial changes in ground surface temperatures have occurred as a result of both land-use change and global warming. In order to quantify subsurface temperature changes, and to evaluate whether the old temperature maps need to be updated, we repeated a small subset of the original temperature measurements, spread over the Netherlands in the same piezometers where historical data were obtained. This study discusses the first results of this new survey by comparing the modern data to the historical ones in relation to changes in climate and land use.