Groundwater temperature

To date, there has been no observable overall increase in groundwater temperature across Switzerland. In certain regions of the country, however, a slight rise in groundwater temperatures indicates the impact of climate change. For example, groundwater temperatures are rising by up to 0.06 °C per year in the Alpine region, in unconsolidated rock outside valley floors in the Central Plateau, and in the Jura. Direct human impacts on groundwater are also leading to measurable changes in groundwater temperature in densely populated areas.

The temperature of groundwater near the surface is influenced by air temperature. Groundwater temperature around surface waters is also affected by the temperature of infiltrating river water. In densely populated areas, the rise in groundwater temperature results from warming caused by infrastructure, rock and underground tunnels, underground car parks or direct thermal input into groundwater (e.g. from building cooling). Other direct impacts in urban areas can also have the opposite effect (temperature decrease), as in the case of heat extraction from the subsurface for heating systems.

Current status reflects seasonality

Groundwater temperature is continuously recorded at around 100 National Groundwater Monitoring NAQUA gauging stations across the country. In groundwater close to the surface, which is typical for Switzerland, the groundwater temperature exhibits a characteristic annual cycle which lags about two months behind changes in air temperature. Depending on the nature of the subsoil, the groundwater temperature varies by between one and several degrees Celsius over the course of the year. In 2021, the mean groundwater temperature at the individual measuring stations was between 5 and 15 °C. In accordance with the altitude of the catchment areas, the lowest groundwater temperatures of below 10 °C occurred in the Jura and in the Alps. In the Central Plateau and on the southern side of the Alps, temperatures ranged from 10 to 13 °C. The highest values, i.e. above 13 °C, were recorded in urban areas.

Development over time stable to slightly increasing

It is possible to identify multi-year periods with relatively low and relatively high groundwater temperatures corresponding to the superordinate air temperature patterns. This can been seen in the high annual temperatures recorded at a comparatively larger number of gauging stations. For example, in the heatwave year 2018 and in the subsequent years 2019 and 2020, high groundwater temperatures were recorded in Switzerland at around half of the gauging stations in the QUANT module (groundwater quantity) of the NAQUA National Groundwater Monitoring. There has also been an increase in groundwater temperatures in recent years (2015–2021), particularly in urban areas.

Monitoring sites in the National Groundwater Monitoring programme NAQUA (QUANT module). Mean groundwater temperature in 2021 compared with the period 2001 to 2020.
Low 2021: 4 Normal 2021: 69 High 2021: 27 Low 2020: 2 Normal 2020: 52 High 2020: 46 Low 2019: 7 Normal 2019: 51 High 2019: 42 Low 2018: 3 Normal 2018: 51 High 2018: 46 Low 2017: 10 Normal 2017: 62 High 2017: 28 Low 2016: 13 Normal 2016: 56 High 2016: 31 Low 2015: 4 Normal 2015: 66 High 2015: 30 Low 2014: 14 Normal 2014: 78 High 2014: 8 Low 2013: 12 Normal 2013: 82 High 2013: 6 Low 2012: 8 Normal 2012: 81 High 2012: 11 Low 2011: 5 Normal 2011: 87 High 2011: 8 Low 2010: 16 Normal 2010: 79 High 2010: 5 Low 2009: 14 Normal 2009: 80 High 2009: 6 Low 2008: 9 Normal 2008: 78 High 2008: 13 Low 2007: 12 Normal 2007: 72 High 2007: 16 Low 2006: 43 Normal 2006: 52 High 2006: 5 Low 2005: 19 Normal 2005: 67 High 2005: 14 Low 2004: 18 Normal 2004: 63 High 2004: 18 Low 2003: 4 Normal 2003: 84 High 2003: 12 Low 2002: 0 Normal 2002: 92 High 2002: 8 Low 2001: 0 Normal 2001: 90 High 2001: 10 Low 2000: 9 Normal 2000: 91 High 2000: 0
Percentage of measuring sites recording low, normal and high groundwater temperatures during the year in question.

Data for the graph: Excel
Source: FOEN

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Last modification 17.05.2022

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