Nitrate exceeds the limit value of 25 mg/l in groundwater at well over a tenth of the monitoring sites across Switzerland. In areas where arable farming is predominant, concentrations are above the limit at almost 40% of the monitoring sites.
Groundwater naturally contains very little nitrate. For groundwater that is used for drinking water or is intended as such, the Waters Protection Ordinance (WPO) prescribes a limit value ('numerical requirement') of 25 milligrams per litre (mg/l). In recent years, this limit has been exceeded at 12% to 15% of the NAQUA monitoring sites nationwide.
Arable areas are affected
Elevated nitrate concentrations in groundwater are mainly due to intensive agriculture. In areas used primarily for growing arable crops or vegetables, around 40% of monitoring sites have exceeded the limit value of 25 mg/l in recent years. Mostly affected is the Swiss Plateau, with concentrations above 10 mg/l at 80% of the monitoring sites.
Evolution de la qualité des eaux souterraines captées (PDF, 2 MB, 03.02.2011)gwa 2010/12: 1083-1094
Last modification 26.08.2019