Data and updating

Access and use

The data and resulting data products (tables, figures and maps) available on the indicator web pages can be used freely given that the source is cited. The indicator should be cited as following:

HELCOM (2018) Inputs of nutrients to the sub-basins. HELCOM core indicator report. Online. [Date Viewed], [Web link].

ISSN 2343-2543



Data on air- and waterborne nutrient inputs from 1995 to 2015 are used in this indicator. Data reporting has not been perfect and gaps exist in the dataset. For waterborne inputs, the PLC6 project corrected suspicious data and filled in data gaps for 1995-2014 to establish a complete and consistent dataset. 2015 data has been added and assessed by BNI, Stockholm University and DCE, Aarhus University [Reference to the dataset when the indicator is published]. Gaps in time series of national air emissions have also been corrected by EMEP experts.

Data on actual (non-normalized) riverine flow as well as atmospheric and waterborne inputs of nitrogen and phosphorus are available at the link below:

Data: Inputs of nutrients to the subbasins - 2018 indicator version.

Waterborne inputs

The dataset behind the present assessment was compiled by the PLC6 project and updated by DCE, Aarhus University and BNI, Stockholm University in cooperation with Reduction Scheme Core Drafting Group, RedCore DG.

Data on waterborne inputs, water flow and retention are reported by Contracting Parties to the PLC-Water database with reporting WEB application. The data are verified and quality assured using the PLC water database verification tools and national expert quality assurance.

There are gaps in time series of national inputs in the PLC water database. Therefore DCA and BNI amended the dataset filling in missing and correcting suspicious data to establish an assessment dataset which then was checked and approved for use in this indicator by the Contracting Parties. A description of the methods used to fill data gaps in is given in chapter 1.2 in BSEP 141 and documentation prepared by the PLC-5.5 project.

Data on water- and airborne inputs are available from 1995-2015 and cover entire drainage basin of the Baltic Sea.

Inputs are calculated from measurements taken from monitored rivers and point sources as well as calculated estimates or modelled inputs from unmonitored areas. Quality assurance guidelines for sample analysis are described in the PLC guidelines and intercalibration activities are carried out periodically. The most recent intercalibration activity with published results was carried out under the PLC-6 project. New regional intercalibration has been perform in early 2018 by the PLC-7 project and the result will be publish later in 2018.

No official information about the uncertainty of inputs of nutrients or organic matter or flow data have been reported to HELCOM yet, but uncertainty estimates are included as a request to be reported by the Contracting Parties in the PLC-6 guidelines. The uncertainty of annual total waterborne nitrogen and phosphorus inputs are computed for each individual sub-basin based on statistical analysis of input trends for the period 1995-2015 (see. Trend analysis and statistical processing).


Airborne inputs

Atmospheric input data for all Baltic Sea sub-basins are available for the period 1995-2014. Atmospheric transport and deposition of nitrogen compounds are used for modelling atmospheric deposition to the Baltic Sea based on official emission data reported by EMEP Contracting Parties and expert estimates. Atmospheric input and source allocation budgets of nitrogen (oxidized, reduced and total) to the Baltic Sea basins and catchments were computed using the latest version of EMEP/MSC-W model. EMEP/MSC-W model is a multi-pollutant, three-dimensional Eulerian model. It takes into account processes of emission, advection, turbulent diffusion, chemical transformations, wet and dry depositions, and inflow of pollutants into the model domain. Further it includes a meteorological model. A comprehensive description of the model and its applications is available on the EMEP website.

Compared with the first evaluation of MAI fulfilment (Svendsen et al. 2015), EMEP has implemented revised models and used updated emissions figures. This lead to revised inputs on normalized nitrogen air deposition to Baltic for 1995-2012, increasing the annual deposition to the Baltic Sea with between 16 to 23 %. The increase on annual nitrogen deposition to the individual sub-basins is between 9 and 27 %. Further EMEP since the latest evaluation of MAI (HELCOM, 2018) as change the resolution for calculating deposition from 50km*50km grid to 0.1°*0.1° (approx. 11km*11km grid). The higher resolution is applied for the annual nitrogen deposition 2000-2016. This reduce annual nitrogen deposition to Bothnian Bay (between 10-18%) and GUR (4-11%) while it is increased to Gulf of Finland (1-10%), Danish Straits (6-12%) and Kattegat (1-4%). For the sum of sub-basins (the Baltic Sea) there changes are less than 1%.

Atmospheric deposition of oxidized and reduced nitrogen was computed for the entire EMEP domain, which includes the Baltic Sea basin and its catchment (Data figure 17). Calculations are done annual on data from two years prior to the calculations. For further details see the annual report by EMEP to HELCOM  Atmospheric Supply of Nitrogen, Lead, Cadmium, Mercury and Dioxins/Furanes to the Baltic Sea in 2011.

Data on air emissions and atmospheric deposition are maintained by EMEP and can be accessed via the EMEP website.

The results of the EMEP Unified model are routinely compared to available measurements at EMEP and HELCOM stations. The comparison of calculated versus measured data indicates that the model predicts the observed air concentrations of nitrogen within an accuracy of approximately 20-30%. Further work is required on reducing uncertainties in emission data and better parameterization of physical processes in the EMEP Unified model to increase the accuracy in future model estimates.

No official information about the uncertainty of provided nitrogen emission data have been sent to EMEP from neither EMEP nor HELCOM Contracting Parties, and consequently further work on emission uncertainty is essential. Submitted emissions data are passing through QA/QC procedures and stored in the EMEP Centre for Emission inventories and Projections CEIP in Vienna, Austria. Reviews about the consistency, comparability and trends of national inventories are available at  There are gaps in time series of national emissions that have to be corrected by experts to make the time series complete.

There are limited data on phosphorus deposition and no emission data for the modelling work has been available for evaluation. For most countries, measurements only covered wet deposition and there was a lack of data on particulate and dry deposition. A fixed deposition rate of 5 kg P per km2 to the Baltic Sea has been used in the PLC-5.5 assessment (HELCOM 2014b, HELCOM 2015). The estimates of phosphorus deposition rates are mainly based on the data from monitoring stations close to the coast line of the Baltic Sea. But there are very few monitoring stations on small islands in the Baltic Sea, and therefore the use of the data mainly from stations on land might lead to an overestimation of deposition. Many monitored concentrations (dry and wet deposition) are very low and close to detection limit. Therefore, the atmospheric phosphorus deposition data and the applied deposition rate is rather uncertain for the whole Baltic roughly ±50% and for minor basins as Gulf of Riga and The Danish Straits even higher uncertainty exists. As atmospheric deposition on average only constitutes 9% of total phosphorus inputs, these uncertainties are less critical than in the case of atmospheric deposition of nitrogen, which on average constitutes 26% of total nitrogen inputs to the Baltic Sea.


Data figure 1.png

Data figure 1. The EMEP model domain used for computations on atmospheric deposition.


Arrangements for updating the indicator

Annual total waterborne inputs of nitrogen, phosphorus and their fractions are reported every year by the HELCOM Contracting Parties and compiled by the PLC Data Manager at the Marine Research Centre, Finnish Environment Institute (MK/SYKE). The data collection is based on a combination of monitored data (measurements at monitoring stations close to river mouth and at point sources) and estimates of inputs from unmonitored areas.

The HELCOM PLUS is a modernized PLC database including QA facilities when uploading, and inserting data, and which allow data reports, quality assures from the Contracting Parties improved access to the waterborne input data. Further assessment dataset will be available in an assessment database under development.

Data on air emissions are reported to EMEP, which subsequently models the atmospheric deposition to the Baltic Sea. EMEP host the emission and deposition data, which can be accessed via their website. EMEP is contracted by HELCOM to provide selected data products on an annual basis.

The Baltic Nest Institute (BNI), Sweden, and Danish Centre for Environment and Energy (DCE), Aarhus University, Denmark has in cooperation with Reduction Scheme Core Drafting Group, RedCore DG   elaborated the present core pressure indicator on nutrient inputs.