Home Programme Description Study region Publications Publication: Ambio Special Issue 2015 People Calendarium

Ekoklim has two main study regions

Ekoklim (2015) publication on long-term changes in Norrström

Elmhagen B, Destouni G, Angerbjörn A, Borgström S, Boyd E, Cousins SAO, Dalén L, Ehrlén J, Ermold M, Hambäck P, Hedlund J, Hylander K, Jaramillo F, Lagerholm VK, Lyon SW, Moor H, Nykvist B, Pasanen-Mortensen M, Plue J, Prieto C, van der Velde Y, Lindborg R. 2015. Interacting effects of change in climate, human population, land use and water use on biodiversity and ecosystem service. Ecology and Society 20(1): 23. Download pdf

The Norrström Drainage Basin


A major part of the work within Ekoklim will be carried out in the Norrström drainage basin (NDB) in Sweden. The drainage basin is large, 22 650 km², and includes two of Sweden’s largest lakes, Lake Mälaren and Lake Hjälmaren (Fig 1). The basin is rather flat and low-lying with numerous lakes. It is underlain by granitic and gneiss-granitic bedrock covered by clay deposits and mostly thin (up to 5 meters) till deposits (Fig 2).

The capital of Sweden, Stockholm, is situated in the Norrström area, and the region as a whole is the most densely populated region in the country. It has undergone rapid urbanization and industrialization and some land sites around Lake Hjälmaren and Lake Mälaren are contaminated. However, the waters in Norrström provide several important ecosystem services. Lake Mälaren is, for example, the main regional water supply for the 1.5 million people in the Stockholm region. Norrström is also famous for salmon fishing and there are more than 30 different species of fish (Fig 3). The surroundings of Lake Mälaren are also known for their high nature and cultural values, as well as the good opportunities for outdoor recreation. The archipelago outside the Norrström basin, directly affected by the activities in the catchment, is also an important area for nature conservation and recreation.

Ecology, hydrology and land use

The Norrström basin consists of 4% built-up areas, 36% agricultural and open land, 49% forest (mostly in the north-western part of the basin), 1.5% wetlands and 9.5% inland waters. Agriculture is an important form of land use because of the fertile soils in the region (Fig 1).

The combination of dense population, agriculture and industry implies strong eutrophication and pollution pressures. These are transferred to the inland surface waters and the coastal waters of the Baltic Sea through the soil and groundwater systems of the basin (Fig 4). These pressures need to be abated for a number of reasons:

(i) The high regional value of the ecosystem service provided by the only available main water supply for Stockholm, Lake Mälaren.

(ii) The sensitive coastal and marine ecosystems of the Stockholm archipelago and the Baltic Sea, which must be safeguarded according to international Baltic region agreements as well as the Swedish environmental policy.

(iii) The requirements of the EU Water Framework Directive. Abatement may involve a number of potential measures at the inland sources themselves, further downstream (e.g. by constructed wetlands and/or reactive barriers), and in the coastal zone.

Administration of the catchment

The Norrström drainage basin is the administrative catchment of Lake Mälaren. It constitutes the main part of the Swedish water management district Northern Baltic Proper, one of a total of five Swedish water districts that have been established in accordance with the requirements of the EU Water Framework Directive. The main water authority for this district, Swedish Water, as well as the main municipal water utility companies Stockholm Water and Norrvatten and the general Swedish sector organization of water utility companies, are important end users and interested partners to various research projects.

In addition, there are a number of other authorities, organisations, companies and NGOs which either are responsible for, or use/impact the water resources in Norrström. They may also be interested in either actively participating in, or using the outcomes from, the eco-hydrological projects related to this drainage basin.

Ongoing research

The Norrström Drainage Basin has been used as a natural field laboratory both by the hydrological research group and by the different ecological departments at Stockholm University. This provides Ekoklim with the advantage of building new research on a comprehensive and coherent set of ecological and hydrological background data. The Ekoklim programme comprises, among other things, development of hydrological models and projections of climatic effects in the region.

In collaboration with the Swedish Water Management Authority for the Northern Baltic Proper District (which includes NDB and for which the track leader Georgia Destouni is member of the board), the answers from this research will guide the development and application of efficient mitigation-adaptation methods to meet new water management requirements and targets posed, e.g., by the EU Water Framework Directive (2000/60/EC) and the Groundwater Directive (2006/60/EC). The Norrström Basin is also one of the showcases for the UNESCO IHP network of EHP Demonstration Projects which aim to identify, quantify and improve the critical interrelationships between water, biota and social systems for sustainable water management using the UNESCO IHP Ecohydrology concept, coordinated by Georgia Destouni.

Several different landscapes within the catchment have also been used for ecological studies in relation to land use and land use change. To estimate effects of land use change on biodiversity and ecosystem services we use historic cadastral maps to estimate land use through time (Fig. 5). Using a space-for-time experimental set-up we investigate the relationship between changes in species richness and composition as an effect of land use. An example of an ongoing project is a study of how climate change and agriculture affect wetlands in the area, in particular with regard to biodiversity and ecosystem services (Fig 6). Another interesting aspect is the impact of agriculture on the aquatic fauna via nutrient flows in streams and lakes (Fig 7).

Fig 1. The study region of Ekoklim the Norrström Basin

Fig 2. Digital elevation model of the Norrström Basin


Fig 3. Stockholm area with outlets from the Norrström Basin


Fig 4. Agricultural activities contribute strongly to eutrophication and the spread of pollutions in the Norrström basin.


Fig 5. Interpretation of historical maps to relevant land use (land cover) classes reveals changes in the landscape.

Fig 6. To investigate the impact on ecosystem services in Norrström, study areas with different amounts of agricultural land are chosen.

Fig 7. Wetland in the Norrström Basin