This dataset contains national information on dredging events where the material is not disposed at sea, reported by HELCOM Contracting Parties, as encouraged by HELCOM Recommendation 36/2 (https://helcom.fi/action-areas/industrial-municipal-releases/dredging/). Please note that this data collection is not conducted in all HELCOM countries, as this is not required under their national legislation, or the data might be unavailable for other reasons. The reporting of dredging sites is mandatory only for those events, where the dredged material is disposed at sea. This data set represents complimentary data of dredging sites where the material is NOT disposed at sea and where the reporting is done on voluntary basis, but still encouraged by the HELCOM Recommendation 36/2. The data regarding dredging activities where the material is not disposed at sea is usually not followed up upon. Therefore, the dataset may not include all dredging activities where the material is not disposed at sea nor is it certain that those activities included have been carried out. Attribute information Dredging ID: Unique id for the event, provided by data provider Latitude coordinate (WGS84, decimal degrees) Longitude coordinate (WGS84, decimal degrees) Dredging Activity: Type of dredging (Capital / Maintenance / Environmental) Description of dredged material: sand, silt, mud, clay, gravel, stones, rock, mixed, other (please specify) Date (dd/mm/yyyy): The date of the dredging event as precise as possible: dd/mm/yyyy, mm/yyyy or yyyy Year: Year of the dredging event Duration: An estimate of the duration of the dredging event Amount of material dredged Unit for the amount (ton/m3) Area of dredging event (m2): An estimation of the area dredged, if available Depth (m): An estimation of the depth where dredging occured Dredging method: digging/dredging device (open, enclosed), suction device, flushing, other (please specify) Notes: Other notes of the activity

This dataset contains dredging sites reported by HELCOM Contracting Parties, according to the HELCOM Recommendation 36/2 (https://helcom.fi/action-areas/industrial-municipal-releases/dredging/). Reporting of dredging sites connected to disposal events became mandatory starting from 2023 data, when the HELCOM Guidelines for Management of Dredged Material at Sea was updated. Before this, reporting of dredging sites was not mandatory, but several Contracting Parties report information about dredging activities. The dredging sites are grouped by spatial data type to point, line and polygon datasets. The dredging site includes a link to corresponding site where the material has been deposited. Attribute information (heading for downloadable shapefile): Dredging ID (Dredging_I): Dredging site id, where material originates from Deposit site (Helcom site ID) (Helcom_sit): Unique id for deposit site Deposit site link (Deposit_si): Link to deposit site, where material from this dredging site is deposited Site name (Site_name): Name of the dredging site Type of area dredged (Type_of_ar): Type of area that was dredged (e.g. harbour or sea) Dredging activity (Dredging_a): Maintenance or capital dredging Material dredged (Material_d): The type of material dredged (e.g. sand, silt) Year (Year): Year of activity Country (Country): Contracting Party of HELCOM Sub-basin (Sub_basin): HELCOM sub-basin (assessment unit level 2) where activity has taken place Quality flag (Quality_fl): Quality flag of data - Quality assured: Data is quality assured either in the annual verification or in a separate quality assurance process by EN DREDS - No quality assurance: Data is not quality assured due to the reason that process has not been carried out - No Quality assurance possible: Data quality assurance process has been made, but it was not possible to find the reference data to verify the parameters

This dataset contains disposal sites reported by HELCOM Contracting Parties, according to the HELCOM Recommendation 36/2 (https://helcom.fi/action-areas/industrial-municipal-releases/dredging/). The disposal sites are grouped by spatial data type to pointwise, line and polygon datasets. Data covers the years 2006-2023. The data format is defined in the HELCOM Guidelines for management of dredged material at sea (https://helcom.fi/action-areas/industrial-municipal-releases/dredging/). Attribute information (heading for downloadable shapefile): Helcom site ID (Helcom_sit): Unique id for deposit site Dredging ID (Dredging_I): Dredging site id, where material originates from Unique ID (Unique_ID): Unique id for each depositing activity (Helcom site ID + Dredging ID + year) Site name (Site_name): Name of the deposit site Type of area dredged (Type_of_ar): Type of area that was dredged (e.g. harbour or sea) Dredging activity (Dredging_a): Maintenance or capital dredging Material deposited (Material_d): The type of material deposited (e.g. sand, silt) Amount deposited (tonnes) (Amount_dep): Amount of material that has been deposited to deposit site, tonnes dry weight Amount beneficial use (tonnes) (Amount_ben): Amount material used for beneficial purposes, tonnes dry weight Beneficial use (Beneficial): Description of beneficial use Year (Year): Year of activity Country (Country): Contracting Party of HELCOM Sub-basin (Sub_basin): HELCOM sub-basin (assessment unit level 2) where activity has taken place Comments (Comments): General comments related to activity Contaminants Cd - SPAH9: Amount of contaminant deposited, in tonnes dry weight Contaminants SPCB7 - MBT : Amount of contaminant deposited, in kilograms dry weight Other contaminants (kg) (Other_cont): Any other contaminant deposited (substance indicated in "notes") Petroleum HC (tonnes) (Petroleum_): Amount of Petroleum HC deposited, in tonnes dry weight HCB - DEHP DBP BBP: Amount of contaminant deposited, in kilograms dry weight Contaminant notes (Contaminan): Notes related to contaminant load Permit (Permit): Deposit site permit reference Quality flag (Quality_fl): Quality flag of data - Quality assured: Data is quality assured either in the annual verification or in a separate quality assurance process by EN DREDS - No quality assurance: Data is not quality assured due to the reason that process has not been carried out - No Quality assurance possible: Data quality assurance process has been made, but it was not possible to find the reference data to verify the parameters

This dataset contains disposal sites reported by HELCOM Contracting Parties, according to the HELCOM Recommendation 36/2 (https://helcom.fi/action-areas/industrial-municipal-releases/dredging/). The disposal sites are grouped by spatial data type to pointwise, line and polygon datasets. Data covers the years 2006-2023. The data format is defined in the HELCOM Guidelines for management of dredged material at sea (https://helcom.fi/action-areas/industrial-municipal-releases/dredging/). Attribute information (heading for downloadable shapefile): Helcom site ID (Helcom_sit): Unique id for deposit site Dredging ID (Dredging_I): Dredging site id, where material originates from Unique ID (Unique_ID): Unique id for each depositing activity (Helcom site ID + Dredging ID + year) Site name (Site_name): Name of the deposit site Type of area dredged (Type_of_ar): Type of area that was dredged (e.g. harbour or sea) Dredging activity (Dredging_a): Maintenance or capital dredging Material deposited (Material_d): The type of material deposited (e.g. sand, silt) Amount deposited (tonnes) (Amount_dep): Amount of material that has been deposited to deposit site, tonnes dry weight Amount beneficial use (tonnes) (Amount_ben): Amount material used for beneficial purposes, tonnes dry weight Beneficial use (Beneficial): Description of beneficial use Year (Year): Year of activity Country (Country): Contracting Party of HELCOM Sub-basin (Sub_basin): HELCOM sub-basin (assessment unit level 2) where activity has taken place Comments (Comments): General comments related to activity Contaminants Cd - SPAH9: Amount of contaminant deposited, in tonnes dry weight Contaminants SPCB7 - MBT : Amount of contaminant deposited, in kilograms dry weight Other contaminants (kg) (Other_cont): Any other contaminant deposited (substance indicated in "notes") Petroleum HC (tonnes) (Petroleum_): Amount of Petroleum HC deposited, in tonnes dry weight HCB - DEHP DBP BBP: Amount of contaminant deposited, in kilograms dry weight Contaminant notes (Contaminan): Notes related to contaminant load Permit (Permit): Deposit site permit reference Quality flag (Quality_fl): Quality flag of data - Quality assured: Data is quality assured either in the annual verification or in a separate quality assurance process by EN DREDS - No quality assurance: Data is not quality assured due to the reason that process has not been carried out - No Quality assurance possible: Data quality assurance process has been made, but it was not possible to find the reference data to verify the parameters

Dataset description: The assessment dataset contains data on water flow and annual nutrient inputs (total nitrogen and phosphorous loads) from catchments and from point sources (municipal, industrial and aquaculture) directly discharging to the Baltic Sea sub-basins. The dataset is produced by regional experts (PLC implementation group) through statistical analysis and filling data gaps in the data reported by national experts to the HELCOM PLC-water database. The dataset includes actual (non-normalized), and water flow normalized annual inputs of total nitrogen (TN) and total phosphorus (TP) from monitored and unmonitored areas per Balic Sea sub-basin. It also contains data on total nitrogen (TN) and total phosphorus (TP) annual inputs from point sources (industrial, municipal and aquaculture) aggregated per country and per sub-basin discharging directly into the Baltic Sea sub-basins. The dataset is published as MS Excel workbook, consisting of several sheets. The sheets provide assessment data for flow, total nitrogen and total phosphorus, as well as background information on data treatment and aggregation. Spatial delineation of catchments is provided in the catchment dataset accessed through HELCOM Metadata Catalogue - (PLC) Assessment catchments (spatial data). Datasets can be related using Source_Code field. The dataset is used in HELCOM Baltic Sea Environmental Fact Sheet (BSEFS) on Waterborne nitrogen and phosphorus inputs and water flow to the Baltic Sea published annually. Dataset content: Excel workbook contains the following tables: AggregationsOfIncompleteRiverTi – the table enlists aggregation of monitored areas of sub-catchments with incomplete time-series with unmonitored areas (country specific), UnmonitoredAreasMergedInMonitor – the table enlists aggregation of unmonitored and monitored areas into unified catchments (country specific). OriginalRivers_Flow, OriginalRivers_TN, OriginalRivers_TP – time series of flows (m3/s) and total N and P (tonnes/year) inputs as reported to PLC-Water database for monitored rivers OriginalUnmonitored_Flow, OriginalUnmonitored_TN, OriginalUnmonitored_TP - time series of flows (m3/s) and total N and P inputs (tonnes/year) as reported to PLC-Water database for unmonitored areas Rivers_Flow (m3/s), Rivers_TN (tonnes/year), Rivers_TP (tonnes/year) - non-normalized inputs from rivers and unmonitored areas, Rivers_NormTN (tonnes/year), Rivers_NormTP (tonnes/year) - normalized inputs from rivers and unmonitored areas, Industry_TN (tonnes/year); Industry_TP (tonnes/year) – aggregated input from industrial point sources discharging directly into the Baltic Sea, Municipal_TN (tonnes/year); Municipal_TP (tonnes/year) – aggregated input from municipal WWTPs discharging directly into the Baltic Sea, Aquaculture_TN (tonnes/year); Aquaculture_TP (tonnes/year) – aggregated input from aquaculture discharging directly into the Baltic Sea. Tables under items 3-6 contain the following fields: Source_Code, Name, Country code, Basin code, 1995, …, 20XX Where water flow is given in m3s-1 and TN/TP tonnes year-1 for each year. Tables under items 7-9 contain the following fields: Country code, Basin code, 1995, …., 20XX Where TN/TP is given in tonnes year-1 for each year. Data update: Metadata is updated by HELCOM Secretariat annually by 1 July. The dataset is updated by HELCOM Secretariat annually by 1 July.

Dataset description: The dataset reflects spatial delineation of monitored and unmonitored catchments used for the assessment of waterborne nutrients inputs to the Baltic Sea sub-basins (Baltic Sea Environmental Fact Sheet) in the HELCOM Pollution Load Compilation. Polygonal features in the dataset cover entire river catchments without distinguishing between sub-catchments located in upstream countries. Some countries even combine unmonitored and monitored parts of river catchments into a single catchment. The Source Code attribute in the dataset corresponds to the Source_Code in the Assessment data on waterborne input of nutrients dataset. The data is reported to the HELCOM Map and Data Service (MADS) and quality assured by Contracting Parties to HELCOM in accordance with the HELCOM Guidelines for the annual and periodical compilation and reporting of waterborne pollution inputs to the Baltic Sea (HELCOM PLC-Water Guideline). Dataset content: Polygonal feature class contains the following attributes: Sub-catchment code (subc_code): Unique code for river catchments and unmonitored areas Sub-catchment name (subc_name): Name of river catchment or unmonitored area River code (r_code): Unique code of the river included in HELCOM PLC assessment. Sub-basin code (subb_code): The Baltic Sea sub-basin where the river drains to. Country code (c_code): The Country on which territory the river mouth is located, for border rivers both are mentioned. Monitoring (monitoring): The monitoring status of the river (M=monitored and U=unmonitored). Marked as monitored only if the catchment has been monitored for the entire time series. Transboundary (transboundary): Listing all countries that have the rivers drainage area on its territory. Area km2 (area_km2): The total area of the catchment in square kilometres. Year (year). Country codes used in the dataset correspond to: DK-DENMARK; EE-ESTONIA; FI-FINLAND; DE-GERMANY; LV-LATVIA; LT-LITHUANIA; PL-POLAND; RU-RUSSIA; SE-SWEDEN. The Baltic Sea sub-basin codes used in the dataset are: ARC-ARCHIPELAGO SEA; BAP-BALTIC PROPER; BOB-BOTHNIAN BAY; BOS-BOTHNIAN SEA; GUF-GULF OF FINLAND; GUR-GULF OF RIGA; KAT-KATTEGAT; SOU-SOUND; WEB-WESTERN BALTIC. Visualization: Map of catchments in the HELCOM Pollution Load Compilation. Data update: Metadata is updated by HELCOM Secretariat annually by 1 April. The dataset is updated by HELCOM Secretariat annually by 1 April.

Dataset description: This dataset contains data on water flows, actual waterborne (riverine plus direct) inputs and atmospheric deposition of nutrients. Furthermore, it includes normalized total (atmospheric and waterborne) inputs of nitrogen and phosphorus into the Baltic Sea. The data are used in the HELCOM core indicator of nutrient inputs (nitrogen and phosphorus) to the Baltic Sea marine ecosystem (Inputs of nutrients - HELCOM indicators). The data is presented in the format of MS Excel workbook consisting of 3 sheets. Sheets of nitrogen inputs and phosphorus inputs integrate 4 tables each. These tables contain time series, starting from 1995, of assessed nutrient input values: waterborne actual (riverine+direct), atmospheric deposition (actual), total actual input (air+water), normalize total input (air+water). Nitrogen and phosphorus inputs are assessed for the following Baltic Sea sub-basins: Bothnian Bay (BOB), Bothnian Sea (BOS), Baltic Proper (BAP), the Gulf of Finland (GUF), the Gulf of Riga (GUR), Danish Straights (DS), Kattegat (KAT) and the whole Baltic Sea (BAS). All input data is given in tonnes per year (tonnes/year). The Flow sheet contains only one table with an annual water flow data time-series for each sub-basin of the Baltic Sea given in cubic meters per year (m3/s). The river input data is based on riverine monitoring data and estimation of loads from unmonitored areas by countries in the frame of national monitoring programs. Data on waterborne inputs and water flow is reported by Contracting Parties to the PLC-Water database. The data are verified and quality assured using the PLC water database verification tools and national expert quality assurance. Atmospheric deposition of nitrogen for all Baltic Sea sub-basins is computed using the latest version of EMEP MSC-W model and data on official emissions reported by EMEP Contracting Parties. Dataset content: Excel workbook contains the following sheets: Nitrogen inputs – time-series of waterborne actual (riverine+direct), atmospheric deposition (actual), total actual input (air+water), normalized total input (air+water) (tonnes/year) . Phosphorus inputs – time-series of waterborne actual (riverine+direct), atmospheric deposition (actual), total actual input (air+water), normalized total input (air+water) (tonnes/year). flow - annual water flow data time-series (m3/s). Visualization: MS Excel workbook. Data update: Metadata is updated by HELCOM Secretariat annually after adoption of indicator report. The dataset is updated by HELCOM Secretariat annually after adoption of indicator report.

Dataset description: This spatial dataset displays catchment areas of the Baltic Sea sub-basins for which the nutrient input to the marine environment and the fulfilment of the maximum allowable inputs of nutrients (MAI) are assessed. Attributes to the polygonal features reflect results of the latest assessment of total normalized input of total nitrogen (TN) and total phosphorus (TP) to the sub-basin from all pathways (riverine, direct, airborne), which are used as HELCOM Core indicator to assess progress towards maximum allowable input (MAI) of nutrients to the Baltic Sea Inputs of nutrients - HELCOM indicators. The assessment takes into account statistical uncertainty which is added to the computed input value. Thus, the fulfilment of MAI means that the nutrient input after adding the statistical uncertainty is below the agreed maximum allowable input value. Attributes TN status and TP status indicate whether MAI is fulfilled or not which is visualized in a simple traffic light colour scheme. The green colour of a catchment indicates that input plus statistical uncertainty was lower than MAI, red colour - input (without statistical uncertainty) was higher, and yellow indicates that input value was lower than MAI but statistical uncertainty does not allow to determine whether MAI was fulfilled. The assessment is performed in accordance with the HELCOM Guidelines for the annual and periodical compilation and reporting of waterborne pollution inputs to the Baltic Sea (HELCOM PLC-Water Guideline). Dataset content: Polygonal feature class contains the following attributes: Sub-basin code (subb_code): Code of the Baltic Sea sub-basin (used for PLC assessment) MAI of total nitrogen (MAI_TN): Maximum allowable input of total nitrogen to respective sub-basin (tons/year) MAI of total phosphorus (MAI_TP): Maximum allowable input of total phosphorus to respective sub-basin (tons/year) Total nitrogen (TN): assessed input of total nitrogen to respective sub-basin (tonnes/year) Total phosphorus (TP): assessed input of total phosphorus to respective subbasin (tonnes /year Total nitrogen uncertainty (TN_uncert): statistical uncertainty of the assessment (tonnes /year) Total phosphorus uncertainty (TP_uncert): statistical uncertainty of the assessment (tonnes /year) Total nitrogen status (TN_status): fulfilment of MAI for TN (fulfilled, not fulfilled, undefined). Total phosphorus status (TP_status): fulfilment of MAI for TP (fulfilled, not fulfilled, undefined). Catchment area (Area): in square kilometres. Year (Year). The following Baltic Sea sub-basin codes are used in the dataset: BAP-BALTIC PROPER; BOB-BOTHNIAN BAY; BOS-BOTHNIAN SEA; GUF-GULF OF FINLAND; GUR-GULF OF RIGA; KAT-KATTEGAT; DS-Danish Straights. Visualization: Map of fulfilment of MAI for nitrogen input to the Baltic Sea - visualizes catchment areas of the Baltic Sea sub-basins in relation to fulfilment of maximum allowable inputs of total nitrogen. Map of fulfilment of MAI for phosphorus input to the Baltic Sea - visualizes catchment areas of the Baltic Sea sub-basins in relation to fulfilment of maximum allowable inputs of total phosphorus. Data update: Metadata is updated by HELCOM Secretariat annually after adoption of indicator report. The dataset is updated by HELCOM Secretariat annually after adoption of indicator report.

These data sets spans multiple oceanographic, chemical, physical, and geomorphological layers. Bathymetric complexity was captured through broad- and fine-scale Bathymetric Position Indices, along with seafloor depth, slope, and ruggedness. Seafloor characteristics included sediment type* and wave exposure estimates. Water column properties were described using measurements of oxygen, salinity, temperature, pH, and nutrient concentrations (nitrate and phosphate) at both bottom and surface layers, each described by mean values and standard deviations. Stratification were characterized by Secchi depth, mixed layer depth, and sea ice concentration. Productivity was approximated by chlorophyll-a concentration. Surface and subsurface variability in wave conditions and satellite-derived sea surface temperature were also collected. Swedish sediment information published with permission from the Swedish Maritime Authority: Decision 23-06009 (12 Sep 2024). To prepare the layers, we applied a procedure designed to iteratively extrapolate missing values in a raster layer by applying a moving window mean filter. It first aligns the input raster to the target grid (Baltic Sea grid at 250 m resolution) using a specified projection method, then repeatedly fills in missing data based on the mean of neighboring cells within a circular window of user-defined size (2 in this case). This iterative process continues until either all missing values are filled or a predefined number of iterations is reached, with early termination if convergence occurs. This procedure ensures that extrapolation respects the spatial extent of the reference grid and provides progress updates during processing. This metadata covers following predictor layers: Bottom Oxygen (Mean) - Mole concentration of dissolved molecular oxygen in sea water at the bottom (µmol/L) Bottom Oxygen (CV) - Coefficient of variation of dissolved molecular oxygen in sea water at the bottom (%) Bottom Salinity (Mean) - Sea water salinity at seafloor (PSU) Bottom Salinity (CV) - Coefficient of variation of sea water salinity at seafloor (%) Bottom Temperature (Mean) - Sea water potential temperature at seafloor (ºC) Bottom Temperature (CV) - Coefficient of variation of sea water potential temperature at seafloor (%) Broad-Scale Bathymetric Position Index - Bathymetric position index, ratio of average depth within 4 km radius to average depth within 20 km radius (m) Chlorophyll-a (Mean) - Mass concentration of chlorophyll a in sea water (mg/m³) Chlorophyll-a (CV) - Coefficient of variation of mass concentration of chlorophyll a in sea water (%) Coarse substrate - Coarse substrate probability of occurrence (%) Depth attenuated exposure at the seafloor - Depth attenuated exposure at the seafloor Distance from the coastline - Distance from the coastline (m) Distance from the nearest river - Distance from the nearest river (m) Fine-Scale Bathymetric Position Index - Bathymetric position index, ratio of average depth within 500 m radius to average depth within 5 km radius (m) Hard substrate - Hard substrate probability of occurrence (%) Mixed Layer Depth (Mean) - Ocean mixed layer thickness defined by sigma theta (m) Mixed Layer Depth (CV) - Coefficient of variation of ocean mixed layer thickness defined by sigma theta (%) Sand substrate - Sand substrate probability of occurrence (%) Sea Ice Concentration (Mean) - Sea ice fraction (%) Sea Ice Concentration (CV) - Coefficient of variation of sea ice fraction (%) Sea surface height (Mean) - Sea surface height above sea level Sea surface height (CV) - Coefficient of variation of sea surface height above sea level (%) Seafloor Depth - Depth in meters below sea surface (m) Seafloor Rugosity within 3 cell radius - Rugosity within 3 cell radius Seafloor Slope - Steepness of the seafloor slope in degrees (Degrees) Secchi Depth (Mean) - Secchi depth of sea water (m) Secchi Depth (CV) - Coefficient of variation of secchi depth of sea water (%) Soft substrate - Soft substrate probability of occurrence (%) Surface Ammonium (Mean) - Mole concentration of ammonium in sea water (µmol/L) Surface Ammonium (CV) - Coefficient of variation of mole concentration of ammonium in sea water (%) Surface Carbon Dioxide (Mean) - Surface partial pressure of carbon dioxide in sea water (µatm) Surface Carbon Dioxide (CV) - Coefficient of variation of surface partial pressure of carbon dioxide in sea water (%) Surface Nitrate (Mean) - Mole concentration of nitrate in sea water (µmol/L) Surface Nitrate (CV) - Coefficient of variation of mole concentration of nitrate in sea water (%) Surface Oxygen (Mean) - Mole concentration of dissolved molecular oxygen in sea water at the surface (µmol/L) Surface Oxygen (CV) - Coefficient of variation of mole concentration of dissolved molecular oxygen in sea water at the surface (%) Surface pH (Mean) - Sea water pH reported on total scale (pH) Surface pH (CV) - Coefficient of variation of sea water pH reported on total scale (%) Surface Phosphate (Mean) - Mole concentration of phosphate in sea water(µmol/L) Surface Phosphate (CV) - Coefficient of variation of mole concentration of phosphate in sea water (%) Surface Primary Productivity (Mean) - Net primary production of biomass expressed as carbon per unit volume in sea water (mg C/m³/day) Surface Primary Productivity (CV) - Coefficient of variation of net primary production of biomass expressed as carbon per unit volume in sea water (%) Surface Salinity (Mean) - Sea water salinity at surface (PSU) Surface Salinity (CV) - Coefficient of variation of sea water salinity at surface (%) Surface Temperature (Mean) - Sea water potential temperature at surface (ºC) Surface Temperature (CV) - Coefficient of variation of sea water potential temperature at surface (%) Terrain Aspect - Aspect, i.e., direction in which the slope is facing out of 360 degrees (N, S, E, W) Wave Height Max (Mean) - Sea surface wave significant height (m) Wave Height Max (CV) - Coefficient of variation of sea surface wave significant height (%) * Swedish sediment information published with permission from the Swedish Maritime Authority: Decision 23-06009 (12 Sep 2024).

This dataset reflects the spatial distribution of area specific inputs to the sea of total nitrogen and total phosphorus from different land-based sources. Area specific inputs to the sea are calculated for each sub-catchment designated for the HELCOM PLC assessment. The sub-catchments are the smallest areas for which loads of nutrients and hazardous substances are assessed. Sub-catchments are always located within borders of a single country and drain into one Baltic Sea sub-basin. Sub-catchments may correspond to either monitored or unmonitored areas. Unmonitored sub-catchments may represent either unmonitored parts of river catchments or aggregated unmonitored areas (depending on the reporting format of each Contracting Party). Area specific inputs to the sea are calculated applying the load-oriented approach (see PLC-Water Guideline, http://www.helcom.fi/Lists/Publications/PLC-Water%20Guidelines.pdf). It means that computed values reflect nutrient inputs from identified sources into respective Baltic Sea sub-basins, considering also retention in downstream sub-catchments. The data on sources of nutrients is obtained through national monitoring programmes and periodically reported by Contracting Parties to the HELCOM Pollution Loads Compilation (PLC-water) database as an integral part of HELCOM Pollution Loades Compilation process. The data is produced, compiled and quality assured in accordance with the HELCOM Guidelines for the annual and periodical compilation and reporting of waterborne pollution inputs to the Baltic Sea (PLC-Water Guideline, http://www.helcom.fi/Lists/Publications/PLC-Water%20Guidelines.pdf). Dataset content: Polygonal feature class contains the following attributes: 1. Source_Code: Unique code for sub-catchment 2. Name: Name of river catchment or unmonitored area 3. SubBasin: Sub-basin of the Baltic Sea the sub-catchment drains to. 4. Country: Country on which territory the sub-catchment is located. 5. Polygon area in sq.km. 6. Retention of nitrogen (%) 7. Retention of phosphorus (%) 8. Area specific inputs of Nitrogen to the sea (kg/km2) 9. Area specific inputs of Phosphorus to the sea (kg/km2) 10. NBL_TN: Area specific background inputs of Nitrogen to the sea (kg/km2) 11. NBL_TP: Area specific background inputs of Phosphorus to the sea (kg/km2) 12. Diffuse_TN: Area specific total diffuse inputs of Nitrogen to the sea (kg/km2) 13. Diffuse_TP: Area specific total diffuse inputs of Phosphorus to the sea (kg/km2) 14. AGL_TN: Area specific agricultural inputs of Nitrogen to the sea (kg/km2) 15. AGL_TP: Area specific agricultural inputs of Phosphorus to the sea (kg/km2) 16. Dif_other_TN: Area specific diffuse nitrogen inputs to the sea from sources other than agriculture (kg/km2) 17. Dif_other_TP: Area specific diffuse phosphorus inputs to the sea from sources other than agriculture (kg/km2) 18. Trans_TN: Area specific transboundary nitrogen inputs to the sea (kg/km2). 19. Trans_TP: Area specific transboundary phosphorus inputs to the sea (kg/km2). Visualization: The following maps visualize the data on area specific loads of nutrients from various sources: • Retention of Nitrogen (%) • Retention of Phosphorus (%) • Area specific total inputs of Nitrogen to the sea (kg/km2) • Area specific total inputs to the sea of Phosphorus to the sea (kg/km2) • Area specific background inputs of Nitrogen to the sea (kg/km2) • Area specific background inputs of Phosphorus to the sea (kg/km2) • Area specific total diffuse inputs of Nitrogen to the sea (kg/km2) • Area specific total diffuse inputs of Phosphorus to the sea (kg/km2) • Area specific agricultural inputs of Nitrogen to the sea (kg/km2) • Area specific agricultural inputs of Phosphorus to the sea (kg/km2) • Area specific diffuse Nitrogen inputs to the sea from sources other than agriculture (kg/km2) • Area specific diffuse Phosphorus inputs to the sea from sources other than agriculture (kg/km2) • Area specific transboundary inputs of Nitrogen load to the sea (kg/km2). • Area specific transboundary input of Phosphorus load to the sea (kg/km2).