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No. 416: Streams 2019. Ecological status. NOVANA

Kallestrup, H., Kjær, C. & Bruus, M. 2021. Vandløb 2019. Økologisk tilstand. NOVANA. Aarhus Universitet, DCE – Nationalt Center for Miljø og Energi, 22 s. - Videnskabelig rapport nr. 416. http://dce2.au.dk/pub/SR416.pdf

Summary

 

This year’s report focuses on the ecological status of streams, more specifically the ecological status at the condition stations included in the monitoring program.  All data were gathered within the framework of the National Monitoring Program for the Aquatic Environment and Nature (NOVANA) in 2017-2019.

The ecological status of Danish streams is described based on the following quality elements: aquatic plants (Danish Stream Plant Index, DVPI), macroinvertebrates (Danish Stream Fauna Index, DVFI) and fish (Danish Fish Index for Streams, DFFVa/DFFVoe). Phytoplankton is not applicable for assessing the condition of Danish streams, but an index for phytobenthos (diatoms) is ready to be implemented. To meet the objective of the Water Framework Directive, minimum ‘good’ ecological status must be obtained for all biological quality elements at a given station. In this report, however, the ecological indicators were assessed individually to maintain focus on the condition of the streams for each individual quality element.

The present report includes the results of the biological surveys from the approx. 2400 condition stations that were scheduled to be surveyed in 2017-2019. The total amount of condition stations are 3800. Data from these stations have not previously been reported. Specifically, the results are based on available data on macroinvertebrates, aquatic plants, and fish for, respectively, 2197, 513 and 246 condition stations.

Data from the investigated stations show that the ecological status generally is poor at the condition stations, as 3-57 % of the stations did not achieve minimum ‘good’ ecological status measured with DVFI, DVPI, DFFVa or DFFVoe, respectively. Relative to DVFI, minimum ‘good’ ecological status was obtained at 57 % of the condition stations. As to DVPI, 29 % of the condition stations had minimum ‘good’ ecological status. For DFFVa, 44 % of the condition stations showed minimum ‘good’ ecological status, the corresponding figure for DFFVoe being 3 %.

A number of physical, chemical and maintenance-associated factors can explain the overall poor ecological status. Furthermore, the stations have not previously been surveyed and the ecological status is therefore unknown. In this way, data on ecological status have not existed, and, therefore, there was no point of reference for the improvement of ecological status cf. the Water Framework Directive’s goal of ‘good’ ecological status.

It should be noted that the current monitoring period (2017-2021) has not yet been completed, and the results in this report are thus based on only part of the condition station network. Thus, the results in this report can be used to describe the ecological status of the surveyed stations but cannot be extrapolated to describe the general ecological status in Danish streams assessed using DVFI, DVPI and DFFV. Especially for DFFV, the data is too weak to be considered representative of the general condition.