Indicator water

Groundwater temperature

The temperature of groundwater is one of its most important characteristics, and a key factor influencing its hydrochemical and biological state. It affects the dissolved oxygen content of the water, as well as the degree of mineralisation. At higher temperatures there may also be an increase in microbial activity – an indicator of groundwater quality. With climate change, in particular, in mind, it is important to monitor how groundwater temperature changes over time.

Assessment of the state
impossible to evaluate impossible to evaluate
Assessment of the trend
impossible to evaluate impossible to evaluate
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
Comment

In a long-term comparison, 2015–19 was a period in which groundwater temperatures tended to be higher than average. Indeed, high temperatures were recorded at just over half of measuring sites in 2018 and 2019, although it is not yet possible to identify any consistent trend periods of several years of low or high groundwater temperatures alternate with a certain regularity. For this reason, the indicator is not evaluated at present.

The CH2018 Climate Change Scenarios suggest that we can assume that the frequency, duration and intensity of hot periods are likely to increase in the long term. Direct anthropogenic factors, such as infrastructure or the use of geothermal energy, can also have a regional effect on groundwater temperature. A slight increase in groundwater temperature, as reflected in the indicator, can be expected overall over time.

International comparison

No standard indicator exists at present in international indicator systems such as that of the EEA. Certain countries currently take similar approaches, however. Austria is one example here.

Method

In a year-by-year comparison, the indicator provides a nationwide overview of the incidence of low, normal and high groundwater temperatures.

The data is supplied from the measuring sites serving the QUANT module of the NAQUA National Groundwater Monitoring programme (around 50 operated by the federal government, and 50 by the cantons), which continuously monitor groundwater temperature. The indicator is based on a calculation of the percentage of the annual number of measuring sites recording low, normal or high temperatures. The mean annual temperature is determined for each individual measuring site, and compared with the corresponding 10th or 90th percentile over 20 years. If the annual mean is below the 10th percentile for 20 past observation years, groundwater temperature is described as low, and if it is higher than the 90th percentile it is termed high. The groundwater temperature is said to be normal if the annual mean lies between the 10th and 90th percentiles.

 
Last updated on: 28.07.2020

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