Nutrient pollution in rivers and streams has fallen significantly in Switzerland. The target values are still occasionally exceeded in agricultural and settlement areas, and international water protection targets for the Rhine River have still not been met for nitrate.
The water quality of surface waters has improved significantly since the 1970s in terms of nutrients, and pollution has fallen substantially. However, the targets are not being met for around 20% of the monitoring sites in the National Surface Water Quality Monitoring Network (NAWA). This can be explained by the huge pressure caused by anthropogenic use, especially in agricultural and settlement areas. With the advent of over-fertilization in the 1980s, a nitrate and phosphorus reduction strategy was also developed in the international context (OSPAR). In contrast to phosphorus, the reduction target for nitrate has not yet been achieved.
The situation is problematic in smaller streams, where treated wastewater is only slightly diluted when introduced into them. Accidents (e.g. liquid manure accidents) still occur (acute risk).
Reduction in phosphate and nitrate concentrations
The data series of the National River Monitoring and Survey Programme (NADUF) show that phosphorus concentrations in rivers and streams have dropped sharply in previous years. Just like lakes, rivers have also been heavily over-fertilized since the 1950s. Improved wastewater treatment and the ban on phosphate in laundry detergents first lowered phosphorus pollution in lakes and then in rivers too. In the section of the Rhine River at Basel, for example, phosphorus levels fell by around 35% between 1990 and 2003. Since the Rhine drains approximately two-thirds of the area of Switzerland, this development is representative for a large portion of the country.
Nitrate comes mostly from agriculture and is detected particularly in groundwater. It enters streams and rivers through groundwater and surface runoff.
National water quality monitoring programme
To monitor the nutrient and pollution levels in watercourses, rivers and streams are studied at over 400 monitoring sites as part of the National Surface Water Quality Monitoring Programme (NAWA) and cantonal monitoring programmes. Monitoring is carried out at several levels: The TREND long-term monitoring programme offers a long-term overview of the state of Swiss watercourses. In the SPEZ monitoring programme, which has a shorter time frame, specific issues are clarified and problem-related special monitoring is carried out.
The National River Monitoring and Survey Programme (NADUF) monitors changes in substances in the water of selected Swiss rivers in conjunction with NAWA. Large and medium watercourses have been studied continuously since the mid-1970s, and small watercourses since 2006.
Last modification 15.06.2021