Follow-up assessment concept

What are net inputs and nutrient input ceilings?

Net input is an estimate of the input to a Baltic Sea basin that is caused by sources within a particular country (or for atmospheric inputs in some cases a collection of countries). The waterborne net input is calculated as the sum of direct coastal point sources and rivers discharging into the Baltic Sea within the country, plus contribution (after estimated retention) via rivers discharging to the Baltic Sea in another country minus contributions to the inputs that can be attributed to upstream countries. The input of nitrogen through atmospheric deposition due to emissions in the country is added to the waterborne net inputs. For more information see the section "In depth information" on Calculation of net inputs.

Nutrient input ceiling is the target net input for each (relevant) country and sub-basin combination. The sum of nutrient input ceilings for a sub-basin is equal to the Maximum Allowable Input for that basin. Nutrient input ceilings are calculated for all of the seven sub-basins. For more information see the section "In depth information" on Calculation of nutrient input ceilings.

Waterborne transboundary inputs were original estimated from input measurements at the relevant borders taking into account retention in the downstream countries. For this assessment, due to time constraints and no new transboundary input data reported from several rivers, it was assumed that transboundary contributions have changed in proportion to the waterborne inputs of the downstream HELCOM country. If transboundary inputs have develop differently than inputs in waterborne inputs in receiving countries and the transboundary inputs are the main or only contributions to a sub-basin from a HELCOM Country (e.g. as Lithuanian inputs to Gulf of Riga) then this can affect the evaluation of fulfilment of CART. For more information see the section "In depth information" on Calculation of net inputs.

Reference inputs comprising of normalized waterborne and airborne inputs for the period 1997-2003 were established for the calculation of MAI and CART agreed on in 2013. For more information, see the PLC-5.5 report and the summary report on development of MAI and CART.

In the Ministerial declaration the reduction relative to this reference were agreed (CART), but in this assessment we rather use the equivalent nutrient input ceiling that is simply reference net input minus CART for a country and basin. For basins without reduction requirement a nutrient input ceiling can also be calculated. For more information see the section "In depth information" on Calculation of nutrient input ceiling.


How the fulfilment of nutrient input ceiling is assessed

A time series of normalized net inputs of air- and waterborne input of nitrogen and phosphorus 1995-2012 have been established for all country by basin combination followed by a trend analysis. It is tested if there are significant decreases or increases in the inputs. Statistically significant changes are calculated and indicated as percentages change from 1995 to 2012. The statistically estimated net nitrogen and phosphorus inputs country by basin in 2012 taking into account the estimated uncertainty on these inputs are compared with the corresponding nutrient input ceilings. Fulfilment off the nutrient input ceilings are shown by colours. Hues of red indicate that the estimated net input in 2012 is higher than the nutrient input ceiling. Grey indicates that when taking into account uncertainty on the estimated net input in 2012 it can’t be evaluated if the net input is lower than the nutrient input ceiling. Green indicates that the estimated net input in 2012 with high statistical certainty is lower than the nutrient input ceiling. For more information see the report Statistical aspects in relation to Baltic Sea Pollution Load Compilation and the section "In depth information" on Calculation of fulfilment of nutrient input ceilings.


How was a dataset established?

A complete dataset with updated water- and airborne nitrogen and phosphorus inputs was established for 1995-2012 based on reported waterborne inputs to the Baltic Sea by Contracting Parties and calculation of atmospheric deposition on Baltic Sea sub-basins by EMEP.  The dataset has been quality assured, some data corrected and data gaps have been filled in to get a consistent and complete dataset, and this dataset has been approved by the Contracting Parties. For more information on how a complete dataset was established, see the PLC-5.5 report and documentation on how a complete PLC-5.5 dataset was obtained.

Airborne inputs have been climate normalized and waterborne inputs flow-normalized to create time-series with strongly reduced variability cause by annual weather and river flow variations (Reference: Statistical aspects in relation to Baltic Sea Pollution Load Compilation).

See also the section "In depth information" on Uncertainty of the assessment.


 Related information

HELCOM nutrient reduction scheme​

Core indicator on nutrient inputs (following up on progress towards maximum allowable inputs)