Freshwater - State and impacts (Switzerland)

The quality of Swiss surface water has improved significantly, with decreasing nitrate and phosphorus levels as a result of the excellent wastewater treatment infrastructure coupled with the ban on phosphorus in detergents. The discharge of micropollutants via wastewater treatment plants and diffuse sources, however, remains a challenge for water protection.

The habitat quality of a surface water body depends not only on the quality of the water, but also on its morphology, the water flow and bed-load regime and the water temperature. Approximately 10 000 km of the total Swiss water network of 65 000 km have been considerably altered by construction work; around 4000 km are culverted (passing surface water through a pipe or a closed conduit) (FOEN, 2009). In many rivers and streams, the volume of residual water remaining after abstraction is not sufficient to maintain their diverse functions. In Alpine rivers downstream from hydropower plants, hydropeaking (surge – low-flow dynamics) impairs the natural habitats. The bed-load regime is altered through stream control measures, gravel extraction and hydropower facilities. This results in more uniform and structurally impoverished habitats with declining biodiversity. The beds of water are sealed, particularly near weirs at run-of-river hydropower facilities, impairing drainage and diminishing groundwater recharge.

The average temperature in the Rhine at Basel, as an example in the Central Plateau area of Switzerland, has risen by more than 2°C in the last fifty years. Climate change and discharges of heated water (e. g. from cooling plants, or from showers and washing machines via wastewater treatment plants) are contributing to this development. Many aquatic organisms respond sensitively to this rise in temperature.

According to the results of the National Groundwater Monitoring, the overall quality of groundwater is good. Problems occur in areas of intensive agricultural use and in built-up areas, where elevated nitrate concentrations, plant protection products (PPPs) as well as pharmaceutical products and traces of chemicals from industrial processes are found. Based on current knowledge, human health is not at risk from the observed pollutant levels. However, the occurrence of pollutants, especially where these exceed the national limits, is a warning sign which needs to be taken seriously.