Indicator water

Nutrients in watercourses

Nitrate and phosphate in watercourses are good indicators of water pollution by nutrients which is anthropogenic, i.e. caused by human activity. Nutrients enter the water through municipal wastewater or discharge from intensively fertilised agricultural land. A higher nitrate or phosphate concentration does not normally have negative effects in a watercourse, but high phosphate discharges into standing waters can cause eutrophication. Nutrients also pollute the seas into which the rivers flow.

Assessment of the state
medium medium
Assessment of the trend
unsatisfactory unsatisfactory
poor 2017: 0 unsatisfactory 2017: 4 fair 2017: 11 good 2017: 43 very good 2017: 42 poor 2016: 0 unsatisfactory 2016: 2 fair 2016: 10 good 2016: 45 very good 2016: 43 poor 2015: 1 unsatisfactory 2015: 3 fair 2015: 9 good 2015: 41 very good 2015: 46 poor 2014: 1 unsatisfactory 2014: 2 fair 2014: 3 good 2014: 54 very good 2014: 40 poor 2013: 1 unsatisfactory 2013: 0 fair 2013: 7 good 2013: 51 very good 2013: 41 poor 2012: 1 unsatisfactory 2012: 1 fair 2012: 11 good 2012: 45 very good 2012: 42 poor 2011: 2 unsatisfactory 2011: 3 fair 2011: 8 good 2011: 47 very good 2011: 40
Assessment distribution of the 111 NAWA monitoring stations for the parameter "Nitrate".

Data for the graph: Excel
Source: FOEN
poor 2017: 9 unsatisfactory 2017: 7 fair 2017: 11 good 2017: 21 very good 2017: 52 poor 2016: 8 unsatisfactory 2016: 6 fair 2016: 12 good 2016: 22 very good 2016: 52 poor 2015: 11 unsatisfactory 2015: 9 fair 2015: 14 good 2015: 22 very good 2015: 45 poor 2014: 10 unsatisfactory 2014: 9 fair 2014: 15 good 2014: 26 very good 2014: 40 poor 2013: 9 unsatisfactory 2013: 8 fair 2013: 14 good 2013: 37 very good 2013: 32 poor 2012: 13 unsatisfactory 2012: 9 fair 2012: 20 good 2012: 33 very good 2012: 26 poor 2011: 24 unsatisfactory 2011: 8 fair 2011: 16 good 2011: 26 very good 2011: 26
Assessment distribution of the 111 NAWA monitoring stations for the parameter "Phosphate".

Data for the graph: Excel
Source: FOEN
Comment

85% of monitoring stations for nitrate and 73% for phosphate are in good or very good condition. Targets are however being exceeded locally in agricultural and developed regions (see map). Problems occur mainly in small streams with a high wastewater content or a high proportion of intensive farming in the catchment. These small watercourses are covered by the NAWA monitoring network.

The positive evolution that can be observed on the phosphates graph is due to normal fluctuations in the runoff conditions rather than to a change in the pollution situation. Since no improvement is observed for nitrates between 2011 and 2017, the overall evolution of nutrients in watercourses is considered unsatisfactory.

Nevertheless long term time series do indicate that in general water pollution by nutrients has fallen significantly in the last few decades. The reduction in phosphorus content was particularly evident following the ban on phosphates in detergents in 1986. The phosphorus content continued to fall after 1990 due to the progressive expansion of wastewater treatment plants. Efforts in agriculture to reduce diffuse nitrate and phosphorus discharges, e.g. by less nutrient-intensive soil management and WWTP optimisation can contribute to a further reduction in nutrient concentrations in the water.

Method

The water quality is recorded jointly by the federal government and the cantons under the NAWA National Surface Water Quality Monitoring at approximately 100 monitoring stations. The chemical state of the water is evaluated on the basis of the phosphate and nitrate concentration by the method “Physico-chemical surveys, nutrients” in the modular stepwise procedure.

Basis for assessment of the trend

Parameter "Nitrate"

Targeted trend Initial value Final value Variation in % Observed trend Assessment
Growth of percentrage "very good" and "good" Average 2011-2013 Average 2015-2017 -2.26% Stabilisation unsatisfactory
Basis: Parameter "Nitrate", very good, good

 

 
Last updated on: 13.08.2019

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