Nitrate in groundwater in Europe

Nutrients such as nitrogen and phosphorus, not absorbed by plants, are lost and become pollutants when present in excessive amounts. This includes high levels of nitrate (NO₃) in groundwater, which poses a threat to the environment and human health.

Reducing high levels of nitrate in groundwater has been a target of EU policy since the adoption of the Nitrates Directive. Mineral fertilisers and manure are main sources of nitrate concentrations in EU groundwaters and an estimated 80% of the nitrogen discharge to the EU aquatic environment stems from agriculture. A large part of nutrients lost to surface- and groundwaters reaches the sea. Around 30% of surface water and 80% of marine waters monitored under the Nitrates Directive are eutrophic.

Several directives address nitrogen losses to the environment . The Groundwater Directive and Drinking Water Directive set the maximum allowable concentration for nitrate at 50mgNO₃/l in order to protect human health and the environment.

The Zero Pollution Action Plan, Biodiversity strategy and Farm to Fork strategy are initiatives of the European Green Deal, which aims to reduce nutrient losses to the environment by 50% in the EU, by 2030. The reduction could lower groundwater nitrate concentrations and decrease the number of monitoring stations with nitrate concentrations above 50mg/l, compared to the reference period 2012-2015.

Despite legislation addressing nutrient pollution, the average nitrate (NO₃) concentration in monitored EU groundwaters did not change significantly from 2007 to 2023, decreasing from 19.3 to 18.1mgNO₃/l but with a large variability as shown by the confidence interval in Figure 1. The Nitrates Directive reporting data over the period 2016-2019 shows 14.1% of groundwater monitoring stations exceeded the maximum allowable concentration of 50mgNO₃/l. This is slightly higher than the observed 13.2% from the reporting period of 2012-2015.

An analysis from the Joint Research Centre modelled impacts in a high ambition scenario of improvements in domestic wastewater treatment and reduction of nutrient emissions to air. It used measures under the CAP 2023-2027, needed to achieve the Biodiversity and Farm to Fork strategy targets. The measures, where CAP measures are relevant for groundwater, could together reduce the nutrient load in European seas by 30% for nitrogen and 20% for phosphorus by 2030. While these potential reductions would be substantial, they still fall below the target of 50% reduction overall in nutrient losses.

EU Member States report groundwater nitrate concentrations under the Nitrates Directive. At country level, nitrate concentrations in groundwater monitoring stations for the period 2016-2019 are distributed into four classes (Figure 2). Class 1 represents monitoring stations where concentrations are below 25mg/l. At the other end of the scale, Class 4 shows the share of stations that exceed the 50mgNO₃/l maximum allowable concentration.

All 27 EU Member States had some groundwaters with reported nitrate concentrations above the maximum allowable concentration of 50mgNO₃/l (class 4). The seven countries with more than 15% of their groundwater monitoring stations exceeding this maximum level were Belgium, Cyprus, Germany, Luxemburg, Malta, Portugal, and Spain. In contrast, the seven countries with more than 80% of groundwater monitoring stations below 25mg/l (class 1) were Croatia, Finland, Hungary, Ireland, Latvia, Poland and Sweden.