Low groundwater levels and spring discharge rates
The indicator provides a national overview of the frequency of unusually low groundwater conditions year on year. If the groundwater level falls more than average due to prolonged dry periods, this can cause bottlenecks in the water supply. Unusually low groundwater levels and spring discharge rates can also be detrimental to ecosystems reliant on groundwater. Based on the CH2018 climate scenarios, it has to be assumed that summer droughts will happen more often and last longer in future and therefore low groundwater levels and spring discharge rates as defined in the indicator may occur more frequently.
In 1990-1992, 1997/1998, 2003, 2005, 2011 and 2017/2018 the indicator was above 50%, i.e. the majority of NAQUA-QUANT monitoring stations recorded above-average days with low groundwater levels and/or spring discharge rates. The dry years of 2003, 2011 and 2018 resulted in unusually high values for the indicator. A long-term tendency cannot yet be detected. Periods of several years with low groundwater levels and spring discharge rates are succeeded by periods of several years with normal or high levels and discharges.
- Related indicators
- Low-flow events
At present there is no standardised indicator in international indicator systems such as the EEA. Similar approaches are now being pursued in various countries (e.g. Belgium, Austria).
Groundwater levels and spring discharge rates are continuously recorded at the monitoring stations in the National Groundwater Monitoring NAQUA, QUANT module (some 50 FOEN monitoring stations and 50 cantonal stations). The indicator includes calculation of the annual number of monitoring stations with an above-average number of days with low groundwater levels and/or spring discharge rates. The daily averages are determined at each individual monitoring station and compared with the corresponding monthly average over 20 years of monitoring. If the number of days on which the groundwater level or spring discharge is below the mean monthly 10th percentile on average over the 20 year period, the groundwater conditions at the monitoring station are described as "low". The indicator defines the percentage of these monitoring stations in the relevant year.