High groundwater levels and spring discharge rates
The indicator provides a national overview of the frequency of unusually high groundwater conditions year on year. If the groundwater level becomes extremely high due to above-average precipitation, substantial damage can be caused to landscapes and buildings. Moreover, this can trigger near-surface landslips and mudslides. Based on the CH2018 climate scenarios, it must be assumed that precipitation intensity and strength will tend to increase long term and high groundwater levels and spring discharge rates as defined in the indicator may occur more frequently.
In 1987/1988, 1995, 1999–2002, 2006/2007, 2012/2013 and 2016 the indicator was above 50%, i.e. the majority of NAQUA-QUANT monitoring stations recorded above-average days with high groundwater levels and/or spring discharge rates. The floods of 1999 and the prolonged precipitation surplus from 2000 to 2002 resulted in unusually high values for the indicator. A long-term trend cannot yet be detected. Periods of several years with high groundwater levels and spring discharge rates are succeeded by periods of several years with normal or low levels and discharges. For this reason the indicator is not evaluated.
- Related indicators
- Flood 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 high 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 and/or spring discharge rate is above the mean monthly 90th percentile on average over the 20 year period, the groundwater conditions at the monitoring station are described as "high". The indicator defines the percentage of these monitoring stations in the relevant year.