Change in the concentration of nitrate in rivers

Documentation

Indicator: Change in the concentration of nitrate in rivers

Tag: WAT003

Definition: Percentage of change in the concentration of nitrate in rivers between 2000 and 2021

Unit: % of change in concentration

Spatial coverage: EU (national values are available for 18 Member States: Belgium, Cyprus, Czechia, Germany, Denmark, Estonia, Spain, Finland, France, Ireland, Italy, Lithuania, Latvia, Poland, Romania, Sweden, Slovenia, Slovakia)

Time coverage: 2000-2021

Update frequency: Every year

DPSIR: State

Other policies: None

Method: 1) Application of automatic quality control procedures to the annual mean concentrations reported either as disaggregated (multiple records per monitoring site per year) or aggregated (one aggregated record per monitoring site per year), resulting in the exclusion of certain data from further analyses; 2) application of a semi-manual procedure focusing on suspicious values having a major impact on the country time series and on the most recently reported data (e.g. outliers, consecutive values deviating strongly from the rest of the time series, whole time series deviating strongly in level compared to other time series for that country, where values for a specific year are consistently far higher or lower than the remaining values for that country), resulting in the removal of such values from the analyses and their checking with the country; 3) aggregation of the remaining values by country and at EU level by averaging across all sites for each year; 4) calculation of the difference in concentration between the year 2000 and the year 2021.

Reference: Nutrients in freshwater in Europe - European Environment Agency, (https://www.eea.europa.eu/ims/nutrients-in-freshwater-in-europe ), accessed 14 November 2023

Producer: European Environment Agency

Provider: European Environment Agency

Validated: True

Peer reviewed: False

Documented: True

Open source: False

Web service

Accessible: True

Spatial scope (Member States): True

Spatial scope (EU27): True

Spatial scope (global): False

Accuracy uncertainties: Methodology uncertainty: nutrient conditions vary throughout the year depending on, for example, season and flow conditions. Hence, the annual average concentrations should ideally be based on samples collected throughout the year. Using annual averages representing only part of the year introduces some uncertainty, but it also makes it possible to include more sites, which reduces the uncertainty in spatial coverage. Moreover, the majority of the annual averages represent the whole year. Datasets uncertainty: the indicator is meant to give a representative overview of nutrient conditions in European rivers. This means it should reflect the variability in nutrient conditions over space and time. Countries are asked to provide data on rivers according to specified criteria. The datasets for rivers include almost all countries within the EEA, but the time coverage varies from country to country. It is assumed that the data from each country represents the variability in space in their country. Likewise, it is assumed that the sampling frequency is sufficiently high to reflect variability in time. In practice, the representativeness will vary between countries. Each annual update of the indicator is based on the updated set of monitoring sites. This also means that due to changes in the database, including changes in the QC procedure that excludes or re-includes individual sites or samples and retroactive reporting of data for the past periods, which may re-introduce lost time series that were not used in the recent indicator assessments, the derived results of the assessment vary in comparison to previous assessments. Waterbase contains a large amount of data collected over many years. Ensuring the quality of the data has always been a high priority. Still, suspicious values or time series are sometimes detected and the automatic QC routines exclude some of the data. Through the communication with the reporting countries, the quality of the database can be further improved. Rationale uncertainty: using annual average values provides an overview of general trends and geographical patterns in line with the aim of the indicator. However, the severity of shorter-term, high-nutrient periods are not reflected.

Comments: None

Storage: None