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EU level

The indicator assesses the annual groundwater level change across Europe, for the period 2000-2019 based on WISE SoE data. The underlying data needs to be improved by Eionet member countries to enable more robust assessment on the change in groundwater level in Europe. A significant trend with annual groundwater level has not been detected for 81% of the monitoring stations mostly due to the short length of available time series. For the remaining 19% of stations, nearly half showed a decreasing trend mostly in southern and western Europe and increasing trend mainly in Eastern Europe. Northern Europe show an equal share of increasing and decreasing trends (Figure 1a).

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  • bednamal (Malgorzata Bednarek) 22 Oct 2021 16:10:17

    POLAND

    Only one country has data since 2000 (CY).

    Heterogeneity of input time series data  - time series of various periods should not be analysed in one go. In the case of a nonlinear phenomenon like natural groundwater fluctuations differences in the length of analysed data series may lead to erroneous conclusions  - especially in case of such short periods.

    It also means that countries cannot be compared with each other.

    Units of the input data from different countries are not uniform. Polish input data are annual depths to groundwater levels measured in metres below surface level. It seems data from other countries are measured as elevations of groundwater levels with respect to sea level? This needs to be checked and recalculated where necessary.

    The above mentioned fact means that conclusions regarding the upward trend of the groundwater level in Poland in recent years are incorrect. It requires recalculation.

    “The underlying data needs to be improved by Eionet member countries” sentence should be modified. It suggests that the data are of bad quality (do you mean for example some wrong methodological approaches?). It is also unclear what you expect from the countries saying “improve” (better methodology or better quality (you mean some errors you detected?) or more data or more frequent for example?)

    • zalllnih (Nihat Zal) 26 Nov 2021 15:18:33

      Thank you for your comments.

      Besides Cyprus, also Denmark and Ireland provided groundwater level data series starting in the year 2000.

       We are aware of that heterogeneity and limitations of the groundwater level data series in the WISE database, and the uncertainties this causes for the presented Groundwater level indicator. The indicator was developed with the intention to make best use of the capacity of the available groundwater level dataset. We have improved the indicator sheet at this point in several ways:

      • In the first section of the indicator assessment we have stated more clearly the limitations and the overall approach.
      • We added the time period of data availability for each country in the note section of Figure 1a and figure 1b.
      • In the “supporting information” section the limitations and capacity of the available groundwater level data are described in more detail.

       The required units of the data are described in the WISE data dictionary. For groundwater levels this is groundwater heads (m) with respect to sea level. During revision, the data from the Polish monitoring stations were removed from indicator assessment and the indicator sheet. When the data for these monitoring station are uploaded again in the unit described by the WISE data dictionary, they can be taken up in the assessment of the groundwater level trends again.

       We agree that the sentence about the need for improvement of the data by the countries is not specific enough. This sentence was changed into: “The length and representativeness of the underlying data needs to be improved by Eionet member countries to enable more robust assessment of the change in groundwater level in Europe.”

       

       

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