Aarhus University Seal / Aarhus Universitets segl

No. 356: Aquatic Environment and Nature 2018. NOVANA


Boutrup, S., Jung-Madsen, S., Nielsen, V.V., Svendsen, L.M., Bang, K., Blicher-Mathiesen, G., Thodsen, H., Hansen, J.W., Høgslund, S., Johansson, L.S., Ellermann, T., Thorling, L. & Frank-Gopolos, T. 2019. Vandmiljø og Natur 2018. NOVANA. Tilstand og udvikling - faglig sammenfatning. Aarhus Universitet, DCE – Nationalt Center for Miljø og Energi, 56 s. - Videnskabelig rapport nr. 356. http://dce2.au.dk/pub/SR356.pdf


This report summarizes the results from the National Danish Monitoring program NOVANA for the year 2018 and the development in a number of parameters for the period 1990-2018. The basis for data, reservations, e.g. in relation to uncertainties on results, or specific conditions in a single year are not included in this report, but can be found in the scientific background reports. It is therefore necessary to consult these scientific reports if the results are to be used in, for example, a decision-making process.

The reporting of data is influenced by the error analyses of total N and total P that were made for surface water in 2016 and the first quarter of of 2017 (see Larsen et al., 2018). It has been possible to restore data on total N and total P in streams for use in the calculation of nutrient transport and nutrient inputs to the sea from the whole of 2016 and the part of 2017 where analysis errors occurred. For other types of water (seas, lakes, etc.), it has not been possible to report total N and P. However, there is no error in the analyses of nitrate and phosphate, which is why these are included in this year’s report, where relevant.

There are similar types of errors in some of the analyses of total N and P from the period 2007-2014. Preliminary restoration of data has been carried out where total N in streams is corrected by 1.3% and total P is not corrected (error of only 0.13%) (Larsen, 2018). This forms the basis for the calculation of the transport of N and P in this report. The overall result of the recovery is not yet available, so further recovery of data from the period 2007-14 may take place in the course of 2020.


Since 1990, there has been an overall reduction of almost 50% in the content of nitrogen in the surface water environment. This generally correlates well with a reduction of sources, listed here as the development in fertiliser use and in emissions from wastewater treatment plants. The nitrogen surplus (added minus harvested) was the highest in 2018 since the early 2000s. In 2018, the lowest yields were harvested since 1990 due to prolonged drought, much sun and high temperatures from mid-April and four months ahead. A possible effect of changes in the nitrogen surplus on the leaching of nitrogen depends on a number of factors, including catch crops.

In 2018, the total nitrogen input from soil to sea was approximately 53,000 tonnes N – against 64,000 tonnes N in 2017. If year-to-year variations in runoff (normalised) are taken into account, the 2018 input was approximately 58,000 tonnes of N, which is generally the same as in 2017, where it was 60,000 tonnes N. The nitrogen input from soil to sea has generally been at the same level over the last 10 years.

It is still too early to assess the overall effect of the increased consumption of nitrogen and the compensatory catch crops, which were made possible by the Food and Agriculture Package in 2015.


For phosphorus, the relationship is somewhat different. Since 1990, there has been a marked reduction of 50-65% in the phosphorus content of surface water, which is attributable to improved waste water treatment – primarily at the large wastewater treatment plants and industrial plants – until about year 2000. The total phosphorus input to the sea in 2018 was approximately 1,700 tonnes, which is about 20% lower than in 2017. Runoff from land was 16% lower in 2018 than in 2017, but, in addition, the amount of phosphorus in wastewater from a person has fallen from 1.0 to 0.72 kg P/year, which has reduced discharges following rain events and from scattered dwellings.

Metals and organic environmentally hazardous substances

Through precipitation, surface water and soil receive much more zinc than any of the other metals. There was a significant decrease in the input from 1989 to around the millennium, although there has been a slight increase over the last 10 years.

Pesticides are among the organic environmentally hazardous substances included in the monitoring. As in previous years, the pesticide prosulfocarb was found in the greatest amount among the 19 substances measured in precipitation. The deposition was highest in autumn, i.e. just after the spraying season. In addition, in 2017 and 2018, measurement was made of pesticides in the air, including prosulfocarb. Also in the air, prosulfocarb was found in the highest concentration and with the highest concentrations in autumn.


In 2018, threshold values for nitrogen dioxide and particulate matter were not exceeded. The threshold requiring information to the public about high ozone levels (180 µg/m3 as the hourly average value) was not exceeded in 2018.

For all air pollutants, there has been a marked decrease in concentrations in the period during which the measurements have been made. The annual mean values of PM2.5, PM10 and nitrogen dioxide have declined by around 25% over the last 10 years, and elemental carbon has decreased by about 60% in the last nine years. From 2017 to 2018, there has been a marked increase in the long-range transport air pollutants (PM2.5, PM10 and ozone). This is not an expression of increasing emissions but a consequence of the natural meteorological variations from one year to the next.

Calculations on the health effects of the total air pollution in Denmark show about 4,200 premature deaths as an annual average for the period 2016-2018. The increase relative to last year is not due to increased air pollution but to extensive changes in model calculations. The total external costs related to air pollution in Denmark are estimated to about DKK 79 billion as an annual average for the period 2016-2018.


The aquatic environment action plans have impacted the nitrate content in groundwater. This is reflected in a clear correlation between the nitrate content in the oxygen-containing groundwater and the surplus of nitrogen in agricultural production in a given year. During the past 11 sampling years, nitrate levels in the oxygen-containing groundwater have, on average, varied around the threshold value.

In 2018, one or more pesticides or degradation products from pesticides were found in 62.8% of the surveyed intake in groundwater monitoring. The threshold value of 0.1 µg/l was exceeded in 26.4% of intakes. The proportion of the intakes investigated where pesticides were found was greater in 2018 than in the previous year. This is attributed to the fact that the samples in 2018 were mainly gathered from intakes where pesticides have previously been found, the so-called operational monitoring. At the same time, groundwater monitoring in 2018 included some degradation products of pesticides that have not been investigated in the past or investigated only for a few intakes. These substances were found at a higher frequency than substances previously investigated.

Water abstraction in Denmark includes abstraction for both drinking water and industrial purposes, including field irrigation. In 2018, abstraction for industrial irrigation was the highest in the period 1989-2018. This reflects the great need for field irrigation due to the very dry year 2018. 


The proportion of streams in at least good state (around 60%), based on measurement of macroinvertebrates, has remained stable during the last approximately 5-7 years. This is a significant improvement from the state 20 years ago where the proportion was around 20%.


Since 1989, significant improvements have occurred in a number of key parameters indicating the state of lakes. Nutrient inputs and nutrient concentrations have decreased markedly, Secchi depth has increased, and for about half of the lakes the chlorophyll a concentration (a measure of the abundance of algae) has declined.

In general, the greatest improvements occurred in the beginning of the period, while the development seems to be stagnant for the last 10-15 years. In addition, the greatest improvements have occurred in the lakes that were most polluted at the start of the monitoring period. There is a positive development in the coverage and depth distribution of submerged macrophytes in about half of the lakes investigated and a general tendency towards more predatory fish and fewer cyprinids in some of the lakes.

Marine areas

The extent of oxygen depletion in September 2018 was slightly greater than in September 2017, markedly lower than in 2016 and equal to the extent in 2014 where the summer was also very hot. Half of the oxygen-depleted area showed marked oxygen depletion. The extent of oxygen depletion in the month of September has varied somewhat in the past ten years, with the lowest levels in 2010-2012 and the highest in 2002, 2008 (Hansen, 2018) and 2016. Wind and temperature significantly influence the variation in the extent of oxygen depletion, but the supply of nutrients is a fundamental factor for the occurrence of widespread oxygen depletion.

The amount of planktonic algae in coastal waters, measured as chlorophyll a, was nearly at the same level as in 2016 and 2017 (a little higher than in 2017, but lower than in 2016) and thus higher than in the previous years. The level corresponds to the levels in the 1990s and 2000s. The abundance of marine flora (eelgrass and seaweed) has generally increased considerably over the years 2009-2013, but the positive development has stagnated in several areas in recent years.  The bottom fauna of the open inland waters has shown progress in species number since a low point in 2008, but in 2018 there were still indications of poor conditions for the bottom fauna in the North Sea and the Skagerrak and some coastal areas. Thus, there are mixed signals in the marine parameters over the past 10 years.