The State of the Environment in Denmark, 2001 National

The aquatic environment The water resource in Denmark is generally suffi cient, but the groundwater is threatened by nitrate and pesticides in some areas. Nutrient loading of the aquatic environment has decreased markedly over the past 10–15 years, but the environmental state of many water bodies is still poor. Hazardous substances 3are increasingly being detected in the aquatic environment. Photo: NERI/Jens Skriver 3.1 Introduction abstracted. After periods of dry years, Physical destruction some watercourses can consequently of water bodies Pressure on the aquatic environment dry out temporarily due to excessive Watercourses have been altered by so- is generally related to three factors: abstraction. cietal development – especially agri- Part of Denmark’s groundwater is cultural. Fields have been extensively • Water resources and excessive water unsuitable as a source of drinking water drained, and many watercourses have abstraction due to contamination with pesticides, been channelized and culverted. More- • Physical destruction of water bodies, nitrate and other substances. If the over, weed clearance has been carried e.g. channelization of watercourses, future drinking water supply is to be out in the watercourses to ensure that drainage of river valleys and recla- safeguarded, we must prevent further the water can fl ow away freely. With mation of lakes and closed fjords contamination and economize on the 90% of the formerly natural water- • Discharge of pollutants, including remaining pure groundwater. courses, this physical intervention has nutrients and hazardous substances. Figure 3.1.1 Water resources Conceptual diagram illustrating the relationship between water consumption and water resources. For exploitation of the groundwater The percentages indicate the share of total water consumption (average 1996–2000). resource to be sustainable, just as much new groundwater needs to be formed Water consumption Precipitation, Effects of excessive as we abstract for the water supply etc. and abstraction evaporation, abstraction groundwater recharge (Figure 3.1.1). The degree of exploita- and runoff Public waterworks Lack of drinking water via watercourses tion must not be so great as to nega- 56% G Lowering of the G Households groundwater table tively affect groundwater quality and G Businesses basal fl ow in watercourses. In practice, G Institutions Effects on this probably means that between 25% Commercial groundwater quality 34% and 75% of the natural groundwater G Crop holdings recharge is exploitable. Groundwater G Market gardens Drying out of watercourses G Freshwater fish farms abstraction is presently sustainable in G Effects on flora and fauna the majority of Denmark. In the eastern Industry etc. 10% part of Zealand and in some other G With own well closely populated areas, though, less new groundwater is formed than is THE STATE OF THE ENVIRONMENT IN DENMARK, 2001 – THE AQUATIC ENVIRONMENT 183 considerably deteriorated habitat con- Nutrients Many societal activities result in ditions for plants and animals. Many One of the main problems affecting the nutrients being discharged to the lakes and ponds have disappeared due Danish aquatic environment is the high aquatic environment, e.g. through to agricultural and urban development. level of nitrogen and phosphorus load- wastewater from households and in- The number of natural marine bio- ing, which both diminishes the quality dustry and loss of nutrients from agri- topes, especially the coastal variety, of the drinking water resource and de- culture and fi sh farming (Figure 3.1.2). has decreased as a result of reclamation stroys habitat conditions for plants and In some areas, atmospheric deposi- of shallow marine areas, changes in the animals. For example, drinking water tion of nutrients can also play a role. seabed in connection with extraction of with a high nitrate content is harmful to Agriculture is the main source of ni- raw materials and construction projects, health, and many nitrate-contaminated trogen loading and a major source of and modifi cation of the coastal areas. water supply wells have consequently phosphorus loading, although much In addition, the environmental state of been closed down. Algal-green lakes, phosphorus also derives from point Danish marine waters is affected by turbid and unclear water and dead ben- sources and sparsely built-up areas. fi shery and the high level of marine thic invertebrates in marine waters are The effects of excessive nutrient traffi c. other examples of the consequences of loading are especially noticeable in the excessive nutrient loading. groundwater (nitrate), in lakes (phosphorus) and in the fjords, coastal waters and open marine waters. The watercourses transport much of the Societal Input and Effects of nutrients that are input to the lakes activities eutrophication occurrence of and the coastal waters. nutrients in the Point sources aquatic environment Effects on aquatic G WWTPs ecosystems Hazardous substances G Separate industrial G Turbid, unclear discharges water Numerous hazardous substances are G Sparsely built-up areas G Algal-green lakes G Dead benthic inverte- found in the aquatic environment Freshwater fish farms brates and oxygen deficit NH3 that derive from our use of chemical Agriculture Atmospheric Point- Effects on man substances (Figure 3.1.3). The most G Manure Fertilizer deposition source G High nitrate content in application widespread contamination of the G Commercial fertilizer NOx NH3 inputs drinking water Leaching G Toxic algae aquatic environment is due to pesti- from arable Watercourses, G Odeour nuisances land lakes, cides and pesticide residues. Our Soil coastal and marine wastewater contains many hazard- Groundwater waters ous substances derived from deter- gents and other substances we fl ush Figure 3.1.2 into the sewers. In addition, many Conceptual diagram illustrating the relationship between human activity, input of nutrients and substances are used in industrial effects on the aquatic environment. production and in the transport sector, e.g. the additive MTBE in unleaded petrol. Consumption of Input to and Effects of Numerous organic pollutants are chemical substances occurrence hazardous in various in the aquatic substances found in the groundwater, including sectors of society environment pesticides and substances leaching Industry Effects on from contaminated sites. Pesticides G Chemical substances ecosystems also occur in watercourses. Concern in production G Effect on species such and products as gastropods, fish, is being expressed about hormone- seals and polar bears like substances, which can change the Combustion of fossil fuels and waste Effects on man sexual characterist ics of such species as Atmospheric Point- G G Energy production deposition source Toxic or roach. In the coastal waters it has re- G Transport inputs carcinogenic substances cently become apparent that hazardous Agriculture G Substances that G Use of pesticides Soil Water- Coastal affect the immune substances such as the antifouling courses and system, fertility or agent TBT can affect marine gastro- and marine the hormone system Ground- lakes waters water pods. Hazardous substances in the marine environment are described Figure 3.1.3 thematically in Section 3.6.2. Conceptual diagram illustrating the relationship between consumption of hazardous substances and their occurrence and effects in the aquatic environment. 184 THE STATE OF THE ENVIRONMENT IN DENMARK, 2001 – THE AQUATIC ENVIRONMENT Photo: Roskilde County/Per Helmgaard 3.2 Inputs to the Over the past 25 years, Denmark has the 1970s, the majority of the wastewa- aquatic environment made considerable investments in an ter only underwent limited treatment. effective wastewater treatment system Today, in contrast, the wastewater treat- The nutrients, organic matter, heavy encompassing sewers and treatment ment plants remove the majority of the metals and hazardous substances that of the wastewater at treatment plants. oxygen-consuming organic matter as are input to the aquatic environment The majority of properties in Denmark well as phosphorus and nitrogen (Fig- derive from many sources. These can are now connected to the sewerage ure 3.2.1). Phosphorus and nitrogen be subdivided into point sources and system, and the majority of household removal was mainly incorporated into diffuse sources. The point sources and industrial wastewater is led the wastewater treatment plants after encompass: through municipal or private treat- adoption of the Action Plan on the ment plants before being discharged Aquatic Environment in 1987. • Wastewater treatment plants, sepa- into the sea or watercourses. In 1999, Just under 60% of the wastewater led rate industrial discharges, fresh- the 25 largest and most advanced to the municipal treatment plants de- water fi sh farms, stormwater out- wastewater treatment plants treated rives from households and service en- falls, sparsely built-up areas and nearly half of all wastewater. terprises, while the remainder derives marine fi sh farms. Wastewater treatment has been con- from industrial enterprises. More than siderably expanded and improved. In 100 major industrial plants have their The diffuse sources encompass: • Cultivated land, uncultivated coun- Figure 3.2.1 Wastewater treatment (%) tryside and atmospheric deposition. Trend in wastewater 100 treatment. MBND, MBNDC 3.2.1 Wastewater Key: 80 MC, MB, MBC Mechanical and treatment plants M = Mechanical Untreated 60 The wastewater that is led to the waste-

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