While groundwater levels and spring discharges in Switzerland are stable in the long term, they fluctuate throughout the year on account of the cumulative amount of precipitation in the preceding months. Groundwater quantity usually varies across regions from year to year, and changes in levels are subject to a certain time delay depending on weather conditions.
Infiltration from river water is primarily responsible for groundwater levels in the unconsolidated aquifer reservoirs in the broad flood plains of the rivers Rhone, Aare, Ticino, Reuss, Limmat, Thur and Rhine. In the unconsolidated and consolidated rock in other regions, groundwater is formed predominantly from melt water or rainwater runoff, depending on the elevation. During dry periods, groundwater widely feeds the smaller rivers of the Swiss Plateau. The variable recharge conditions and the interrelationship between surface water and groundwater cause typical seasonal fluctuations in groundwater levels and spring discharges. Groundwater use, land use, soil improvement, construction and climate change can all have an impact on the status and trend of groundwater levels and spring discharges.
Groundwater levels reflect the weather conditions
Groundwater levels and spring discharges across the country are continually recorded at around 100 NAQUA National Groundwater Monitoring sites. The levels reflect the weather conditions on the surface, though in attenuated form and subject to a time delay. Long periods of precipitation – especially in winter – increase groundwater recharge. In contrast, sustained periods of drought – particularly in summer and autumn – can result in low groundwater levels and spring discharge, thus affecting the groundwater quantity.
Long-term trend is stable
Long-term weather patterns (temperature and precipitation) in Switzerland are often correlated with periodic fluctuations in groundwater levels lasting for several years, entailing a regular succession of low and high water situations. Within this general pattern, significant regional differences are the norm.
In recent times, the dry years of 2011, 2015, 2018, 2019 and 2020 in particular led to low groundwater levels and spring discharges. In contrast, years with above-average amounts of precipitation (e.g. 1999–2002, 2021) resulted in generally high groundwater levels and spring discharges.
The difference in high and low water situations varies depending on the particular features of the aquifer. For example, groundwater resources connected to watercourses react quickly to heavy precipitation, whereas deeper groundwater resources often do not react to individual rainfall and only show a slight change in level after a few months of prolonged rainfall or drought.
Last modification 17.05.2022