Denmark has a total land area of 43,000 km2. The population of Denmark constitutes 5.1 million, the population density accordingly being 120 inhabitants per km2. The long coastline of Denmark in proportion to its area means that it is dominated by a large number of small river catchments and short rivers. The three largest rivers only drain about 14 per cent of the land area. Denmark has 468 lakes with an surface area greater than 0.05 km2 (5 ha). The typical Danish lake is small, shallow and has a short water residence time. The coastline is 7,300 km long and one quarter of the coastline borders the open sea (ie. the North Sea and the Skagerrak). The remaining three quarters of the coastline borders fjords, estuarine areas and semiclosed coastal areas (eg. the Kattegat, the Belts and the Baltic).


Surface water quality monitoring

Involved institutions

Surface water monitoring in Denmark has been undertaken since the early 1970s. The 14 Danish counties have been responsible for inland surface water and coastal water monitoring and management, while the Ministry of Environment and Energy is responsible for monitoring the marine areas. During the 1970s and 1980s much information on the environmental state of surface waters was collected and reported by the counties. The use of information on a national level was, however, rather limited, primarily because the previously decentralized Danish monitoring was suffering from widely differing regional efforts, differing staff qualifications, incommensurable methods, differing sampling strategies, etc. This situation changed when the nation-wide monitoring programme was established in 1988.

In 1987 the Danish Government passed the Action Plan on the Aquatic Environment. The main objectives of the Action Plan are to reduce the nitrogen and phosphorus discharge by 50 and 80 per cent, respectively. In connection with the Action Plan it was decided to establish a monitoring programme to observe the reduction in discharge of nutrients and monitor the effects on the biological communities in the aquatic environment. The programme assembles nation-wide information on the sources and distribution of nutrients in inland waters (groundwater, rivers and lakes) and the nutrient loading of the marine environment. In addition, the programme provides information on the water quality of ground water, inland surface waters and marine waters. The Danish Environmental Protection Agency has the overall responsibility for the monitoring programme.

In order to obtain the above information, monitoring sites have been established at locations all over Denmark in connection with a comprehensive sampling programme. The regional authorities (the 14 Danish counties) are responsible for monitoring groundwater, rivers, lakes and coastal waters, while the National Environmental Research Institute (NERI) is responsible for monitoring the open sea and the atmospheric deposition. NERI and Geological Survey of Denmark (GSD) have the responsibility of national planning, coordination, and national annual reporting of the environmental state of the aquatic environment. The counties report the results of their monitoring activities annually, and these reports together with key data are the basis for the national environmental reports. The national authorities ensure through advising, technical meetings, and technical guidelines appropriate operation and coordination of the various monitoring activities. Consistency and comparability of information processed is ensured by national coordination and guidelines and technical reports on monitoring, sampling frequency, variables to be measured, etc. The monitoring programme has in all significantly improved the information basis for decisions to be taken in relation to the environmental state of the aquatic environment.


Rivers and streams

The nation-wide aquatic monitoring programme includes three river monitoring programmes R1-R3. The general river monitoring programme R1 has two main purposes; a network comprising 238 sampling sites provides detailed information on nutrient loading and biological conditions of rivers draining various representative catchments (eg. forest and natural, agricultural, and urban), whereas a network comprising 130 sampling sites in 125 river systems provides an overall estimate of nutrient loading to Danish coastal waters. Many sampling sites are included in both networks, the river networks consisting of totally 261 sampling sites in 240 rivers and 125 river systems. Water samples are taken at fortnightly to monthly intervals and analyzed for general chemical and physical variables. The R2 monitoring programme aims at establishing information on the water quality of springs and brooks and the network consists of sampling sites in 58 springs, of which 45 are situated in agricultural areas and 12 in nonagricultural areas. Sampling takes places four times annually and the samples are analyzed for general chemical and physical variables. The R3 monitoring programme consists of six small (< 15 km2) agricultural catchment areas selected as being representative of the soil types, climatic conditions and farming practices in Denmark. The objectives are to monitor the impact of farming on the leaching of nutrients to the surface water and upper layers of groundwater. In the catchment, the quality of soil water, drainage water, upper groundwater and river water are assessed. Sampling is generally undertaken at weekly or fortnightly intervals and analyzed for general chemical and physical variables and pesticides. Additionally, land-use practices (crops grown, use of fertilizers, etc.) in the catchments are described annually.



The objectives of the lake monitoring programme L1 are to record the magnitude of nutrient loading and to elucidate trends in lake nutrient loading and its effects on physical, chemical and biological conditions. Of a total of 468 Danish lakes larger than 5 ha, 37 are included in the monitoring programme. These lakes are studied intensively each year, including sampling and measurement of nutrients in the main tributaries, and 19 annual water samples taken from lake water and analyzed for general chemical and physical variables, phytoplankton and zooplankton. Additionally, macrophytes, fish and the chemical composition of lake sediment is studied every five years.


Marine waters

Monitoring of the marine waters is performed in close cooperation between the counties and NERI. The counties are responsible for monitoring of estuarine and coastal waters. The objectives of the nation-wide coastal and marine monitoring programme M1 are to determine how and to what extent conditions in coastal and marine waters are influenced by nutrient loading and to follow the trends in physical, chemical and biological conditions in marine areas. The sampling programme covering coastal areas includes hydrography, oxygen concentration, nutrients, plankton, zoobenthos and macrophytes. Water samples are generally taken at monthly intervals, however, at 19 intensive sampling sites 32-52 annual samples are taken. The county network includes around 200 coastal and 80 offshore sampling sites.

Water quality of the open sea is monitored during ten annual cruises in the Inner Danish waters (Kattegat, the Belt Sea and the Baltic Sea) and one cruise in the North Sea and the Skagerrak. The sampling programme for the open sea includes hydrography, oxygen concentration, nutrients, plankton and zoobenthos. The heavy metal content of sea water, fish and bivalves is monitored as well. The annual evaluations and reports of the state of the environment are supplemented with data from The Danish Institute for Fisheries and Marine Research, Swedish, German, and Norwegian investigation in the open marine areas.

Table 3.3: Danish national surface water monitoring programmes.

No. Name Responsible institution Variables Period of operation &
Sampling Frequency (SF)
Data & national
Rivers and streams
R1 Nation-wide Monitoring Programme
Monitoring of streams
NERI Chemical and physical variables
Since 1989
SF: 12-26 (52)/yr
Nation-wide, 261 sampling sites in approx. 125 river systems Database: NERI
Reporting: NERI
R2 Nation-wide Monitoring Programme
Monitoring of springs.
NERI Chemical and physical variables Since 1989
SF: 4/yr
58 springs
Database: NERI
Reporting: NERI
R3 Nation-wide Monitoring Programme
Monitoring of agricultural watersheds
NERI Chemical and physical variables on soil water, drainage water, ground water and river water. Since 1989
SF: 12-26 (52)/yr
6 agricultural watersheds Database: NERI & GSD
Reporting: NERI & GSD
R4 Inventory of biological assessment of river quality EPA Macroinvertebrates
Quality classification grades
Since 1989
SF: 1-2/yr
10,000 sampling sites
Database and reporting: EPA
L1 Nation-wide Monitoring Programme
Monitoring of lakes
NERI Chemical and physical variables in lake water and tributaries.
Phyto- & zooplankton, fish and macrophytes.
Sediment composition
Since 1989
SF: Lake water 19/yr
Tributaries 12-26/yr
Plankton 19/yr
Fish, macrophytes & sediment 1/5 yr
37 lakes
Database: NERI
Reporting: NERI
Coastal and marine areas
M1 Nation-wide Monitoring Programme
Monitoring of coastal and open marine waters
NERI Chemical and physical variables.
Phyto- & zooplankton, zoobenthos and macrophytes.
Sediment composition
Since 1989
SF: Water 8-52/yr
Plankton 8-52/yr
Zoobenthos 1/yr
Macrophytes & sediment 1/5/yr
200 coastal sampling sites and 80 offshore
sampling sites.
Database: NERI
Reporting: NERI

NERI: National Environmental Research Institute, Ministry of Environment and Energy, GSD: Geological Survey of Denmark, Ministry of Environment and Energy


Geographic coverage


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Filed under: freshwater
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