Abstract

The seven biggest rivers cover half of the Baltic Sea catchment area. Nearly 55 million people inhabit their catchment areas, meaning that anthropogenic pressure is high. Anthropogenic pressure is highest in the southern catchments, where population is densest and agricultural activity is intense. Consequently, the nutrient loads are high in the south: For example, in 2017 the area specific total nitrogen load of the River Nemunas was 838 kg km-2, whereas it was 133 kg km-2 for the River Kemijoki (in the north). The variation in the area specific total phosphorus loads was in 2017: The River Göta älv 4.3 kg km-2 and the River Nemunas 26 kg km-2. The seven rivers exported 372,000 t of total nitrogen and 13,500 t of total phosphorus into the Baltic Sea in 2017, which was nearly 40% of the total nitrogen and phosphorus loads of the Baltic Sea. The Neva River contributed over 40% of the total flow into the Baltic Sea Catchment area, but the River Vistula had the highest total nitrogen and total phosphorus loads in 2017 with 30% and 28% respectively. Total phosphorus load showed a statistically significant decrease from 1995 to 2017, with total phosphorus being decreased by 6,000 t (30%), but the trends for individual rivers varied greatly. The decreasing tendency in the total nitrogen load found previously had levelled off. To enable division of nutrient load reductions according to their origin country nutrient input ceilings were established for five of the seven biggest rivers (the 5 biggest transboundary rivers). In 2017 the remaining reduction to fulfill the input ceiling of those five rivers was 71,000 t of total nitrogen and 8600 t of total phosphorus. The proportion of the remaining TN reduction of the five biggest rivers was 56% of the total remaining TN reduction of the whole Baltic Sea and 88% of the remaining TP reduction respectively.

Published in

Baltic Sea Environment Proceedings
2021, number: 178
Publisher: Helsinki Commission

SLU Authors

• Sonesten, Lars

  • Department of Aquatic Sciences and Assessment, Swedish University of Agricultural Sciences
    

Associated SLU-program

Coastal and sea areas
Lakes and watercourses
Eutrophication
Use of FOMA data


Sustainable Development Goals

Ensure availability and sustainable management of water and sanitation for all
Conserve and sustainably use the oceans, seas and marine resources for sustainable development


UKÄ Subject classification

Oceanography, Hydrology, Water Resources
Geochemistry
Ecology


Permanent link to this page (URI)

https://res.slu.se/id/publ/113939