Significant declining trends of groundwater level and spring discharge and their comparison between two periods (2014-2023 vs 2018-2023)

The main task was to assess the existence of significant declining trends at monitoring objects of the state groundwater hydrological network. The evaluated parameters included groundwater levels and spring discharges in Quaternary and Pre-Quaternary groundwater bodies of Slovakia. Two time periods (2014-2023 and 2018-2023) were evaluated and subsequently compared with each other to identify potential differences in trends. Time series of mean annual values as well as mean annual minimum values from a total of 1455 monitoring sites were evaluated (including 1113 boreholes and 342 springs). To identify the presence of a significant declining trend, all time series were tested using the non-parametric Mann-Kendall statistical test. If the dataset followed a normal distribution, the parametric ANOVA method was also applied. For better comparison the results were visualized using map presentation. If there was one significant declining trend found, groundwater quantity status was classified as being at risk. If there were two or more declining trends in one category (average/minima) found, the groundwater body was classified as having a poor quantitative status. Finally, 17 groundwater bodies were classified at risk and five groundwater bodies in poor quantitative status for period 2014 - 2023. However, for shorter period 2018 – 2023 only two groundwater bodies were found in poor quantitative status and four groundwater bodies were classified at risk. There was an improvement in the quantitative status of three groundwater bodies declared in comparison to longer period (from poor to good quantitative status) – SK2000200P (Intergranular groundwater of the western part of the Vienna Basin), SK200220FP (Fractured and intergranular groundwater of the northern Central Slovak Neovolcanic Area), SK200240FK (Fractured and karst-fractured groundwater of the Malá Fatra), SK200290FK (Fractured and karst-fractured groundwater of the southern slopes of the Low Tatras).  In addition, 15 groundwater bodies classified at risk in longer period improved their quantitative status to good quantitative status in short period 2018-2023. Classifications of both periods define the groundwater body SK2002300P (Intergranular Groundwater of the Eastern Part of the Danube Basin and the Ipeľ Basin) in poor quantitative status and two groundwater bodies at risk SK2000400P (Intergranular groundwater of the eastern part of the Vienna Basin) and SK200590FP (Fractured and intergranular groundwater of Neovolcanic rocks).