Assessment of nutrient loads to the Baltic Sea from the Southern Baltic Region in Sweden

The Swedish government decided in 2006 to allocate funds to execute the following task: "Identify the areas, which contributes most to nutrient pollution of the coastal waters" according to the national Action Plan for the marine environment.

DHI was commissioned by the Water Authority of Southern Baltic to develop a model for two sub-regions, the Coastal Zone Area 89090, which is Southwestern coastline of Skåne, and the West Lyckebyån river basin area.

The application seeks to increase the level of detail in calculating the nutrient transport by identifying and describe the various sources and simulate concentrations and transport of nitrogen and phosphorus in a river basin for different load scenarios.

For both areas detailed MIKE BASIN models were developed simulating the loads from both point and diffuse sources, the hydrological conditions, and the in stream retention and the water quality processes for nitrogen and phosphorus. The models were calibrated against stream flow and recorded water quality. The load assessment included contribution of N and P from different land uses such as forest, farmland, open land, logging and mire, and from point sources such as sewage treatment plants, individual sewage and stormwater. A specific processes have been made to estimate of the load from the farmland.

The results were reported as continuous yearly loads to the sea from various sub-basins and various and various sources.