Why should we care about this issue
The environmental quality of lakes and rivers in Denmark has improved since the 1990s. However, nearly two‑thirds of the lakes and half of the rivers do not have a sufficient ecological quality. At national level, the groundwater resources are exploited at a sustainable rate, but locally there are problems with over‑exploitation and pollution with pesticides and nitrate.
The state and impacts
The ecological quality of the Danish lakes is controlled by nutrients. A significant decrease in the load of nutrients has been observed since the 1990s. The average level of phosphorus and nitrogen in Danish lakes has decreased by 26 % and 18 % respectively from 2000 to 2008. This has led to a significant improvement in the ecological quality in many Danish lakes, such as improvements in the water turbidity and better conditions for the bottom vegetation.
Figure 1 (3.1.1): Development of the concentration of phosphorous, nitrogen and chlorophyll-a (indicator for algae growth) in 19 Danish lakes. Source: National Environmental Research Institute.
Figure 2 (3.1.2): Development in the water turbidity in 20 Danish lakes. Source: National Environmental Research Institute.
In 2008, the water quality in 54 % of the Danish rivers was classified as good or very good, compared to 42 % in 2000. However, pesticides are measured in 70 % of the monitoring water samples. The improvement in the ecological quality of rivers is mainly due to better sewage treatment and a more careful physical maintenance.
Figure 3 (3.2.1): Development in the ecological quality (Danish River Fauna Index) in Danish rivers. Measurements are from approximately 250 stations in a wide range of small and larger rivers. Source: National Environmental Research Institute.
Figure 4 (3.2.2): Concentration of nitrogen in rivers grouped after the dominant nitrogen source, i.e. aquaculture, agriculture, nature and waste water treatment plants (WWTP). Source: National Environmental Research Institute.
Figure 5 (3.2.3): Concentration of phosphorous in rivers grouped after the dominant phosphorus source, i.e. aquaculture, agriculture, nature and waste water treatment plants (WWTP). Source: National Environmental Research Institute.
Pollution with pesticides and nitrate in groundwater wells closes between 25 and 150 drinking water wells every year. The frequency of pesticides in groundwater drillings has increased since 2000. In 2008 pesticides were detected in 40 % of the drillings from the surveillance programme, and in 11 % of the drillings the concentration of pesticides was above the limit value of 0.1 mg/l. In approximately 17 % of the drillings the concentration of nitrate was above the limit value. Groundwater drillings for drinking water, where concentrations of pesticides or nitrate are above the drinking water limit values, are often closed.
Figure 6 (3.3.3): Pesticide concentration in public groundwater wells. Criteria for including wells in the data are that pesticides are detected more than once from 1993-2008. Source: Geological Survey of Denmark and Greenland (GEUS).
Figure 7 (3.3.4): Concentration of nitrogen in groundwater wells. Data are from 2003-2008.
Source: Geological Survey of Denmark and Greenland (GEUS).
The key drivers and pressures
A reduction in the leaching and run-off of nutrients from the agricultural sector and an improved sewage treatment has led to a significant improvement of the Danish aquatic environment.
Livestock production produces approximately 35 million tonnes of liquid and solid manure per year. This is used in agricultural crop production in addition to commercial fertilisers. Excess nitrogen leaching to the aquatic environment was reduced by 12 % from 2000 to 2007. Excess nitrogen leaching data in 2008 is not available, however surplus nitrogen continues to decrease and from 2007 to 2008 by 1 %. The surplus phosphorus decreased by nearly 32 % from 2000 to 2008, although a decrease in leaching of phosphorus has not yet been measured.
The pesticide application frequency in agricultural production increased by more than 50 % from 2000 (2.07 times per year) to 2008 (3.16 times per year).
Figure 8 (MTR2009:1.2.1): Leaching of nitrogen from the root zone and surplus phosphorus in the agricultural sector. The Danish ’Green Growth‘ plan set new reduction targets for nitrogen and phosphorus. For phosphorus, the target is defined differently compared to the previous set reduction target (i.e. Water Environment Plan III) and therefore cannot be compared with existing data. Therefore the old target is shown in the figure. The target for nitrogen set in the ’Green Growth‘ plan is recalculated to a figure for leaching from the root zone as shown in the figure. Source: Faculty of Agricultural Sciences and National Environmental Research Institute.
Figure 9 (1.2.2): Frequency of pesticide application in Danish agriculture. Because the calculation method changed in 1998 and the target set for frequency of application is based on an old method, both are shown. Reference: Statistics Denmark and The Danish Environment Agency.
The main part of the use of freshwater in Denmark is from groundwater resources, including industrial and agricultural use. Exploitation of groundwater has decreased since the beginning of the 1990s and has been stable since 2000. Consumption through the public water supply accounted for 60 %, agriculture and aquaculture for 34 % and industry for 6 % in 2006.
Figure 10 (3.4.1): Water extraction in Denmark including public water supply, commercial water supply (agriculture and aquaculture) and industrial production. Figures from 2007-2008 is not included due to the implementation of a new municipality reform in Denmark. Source: Geological Survey of Denmark and Greenland (GEUS).
The 2020 outlook
The most recent efforts to improve the ecological quality of lakes and rivers are defined in the action plan ’Green growth‘. Reduction goals are set for the leaching of phosphorus to lakes and rivers by 210 tonnes and for the leaching of nitrogen to marine waters by 19 000 tonnes by 2015. The impact from pesticides is regulated by a target set for the pesticide application frequency of 1.7. In addition, it has been agreed to improve the physical conditions of 7 300 km.
The impacts of nitrates and pesticides on groundwater quality are indirectly affected by the initiatives to improve the ecological quality in rivers and lakes including establishing a 25 m-pesticide‑free zone around public water wells by 2013.
At the national level, groundwater resources are exploited at a sustainable rate, but locally there are problems with over exploitation and pollution with pesticides and nitrate. A sustainable exploitation of groundwater is calculated at 1 000 million m3 per year. In 2006, the Danish exploitation of groundwater was 653 million.
Existing and planned responses
The EU Water Framework Directive from 2000 is implemented in Danish legislation in the national Environmental Objective Act from 2003. Efforts to improve the ecological quality of freshwaters are defined by reduction goals for the leaching of phosphorus to lakes and nitrogen to marine waters, by improving the physical condition of rivers and reducing the use of pesticides. The initiatives are defined in the Government action plan ‘Green growth’ from 2009.
An example is the national implementation of initiatives, defined in the EU Framework for community action, concerned about the sustainable use of pesticides from 2009. These initiatives are concerned with issues such as training of professional users of pesticides, general pesticide storage procedures, application and disposal procedures of residues and packing as well as introduction of compulsory inspection of sprayers, the inclusion of integrated pest management (IPM) and notification obligations for spraying.
The ’Green Growth‘ plan also set standards for improvement of sewage treatment facilities in the countryside and better treatment of rainwater overflow. Regional environmental centres were mandated to provide regional action plans by the end of 2009 for implementation of the environmental goals defined in the ‘Green Growth’ action plan.
At the national level, several measures have been identified including, for example, an increased pesticide tax and the introduction of a market‑based nitrogen quota system.
Normander, B., Henriksen, C.I., Jensen, T.S., Sanderson, H., Henrichs, T., Larsen, L.E. & Pedersen, A.B. (red.) 2009: Nature and Environment 2009 – Part B: Factsheets. National Environmental Research Institute (NERI), Aarhus University, 170 p. – NERI scientific report series, no. 751. (In Danish) http://www.naturogmiljoe.dmu.dk/
Wiberg-Larsen, P. (red.) 2010: Rivers 2008. NOVANA. National Environmental Research Institute, Aarhus University. 66 p. – NERI scientific report series, no. 764. (in Danish) http://www2.dmu.dk/Pub/FR764.pdf
Jørgensen, T.B., Bjerring, R., Landkildehus, F., Søndergaard, M., Sortkjær, L. & Clausen, J. 2009: Søer 2008. NOVANA. Danmarks Miljøundersøgelser, Aarhus Universitet. 46 s. - Faglig rapport fra DMU nr. 763. http://www.dmu.dk/Pub/FR763.pdf
Government 2009: Action plan “Green Growth”. http://www.mim.dk/NR/rdonlyres/D5E4FC9A-B3AC-4C9A-B819-C42300F23CCA/0/GROENVAEKST_2904rapporten.pdf (in Danish)