Intra-annual groundwater levels and water temperature patterns in raised bogs affected by human impact in mountain areas in Poland

Highlights: • Wavelet analysis was applied to examine time series. • Wavelet coherence between hydrological and meteorological variables were quantified. • Peat bogs display high stability of groundwater level and water temperature. • Water table fluctuations are closely linked to weather conditions in summer and autumn. Over the last century, the vast majority of peatlands in Europe have experienced substantial transformation as a result of drainage works that led to an imbalance in the natural hydrologic regime as well as changes in vegetation composition. The ongoing study aims to reconstruct the natural hydrologic regime of peatlands and restore their typical vegetation communities. In this study, we examine the variability of groundwater levels and groundwater temperature in raised bogs located in the Bieszczady Mts. in southern Poland. Both groundwater table levels and groundwater temperature serve to characterise the hydrology of peatlands, which in turn is critical for plant growth and rates of relevant biochemical processes. Our objective is to determine the predominant scale of intra-annual variability in time series and identify their potential sources by assessing the adaptive response of peat bogs to key changes in weather conditions. For this purpose, data obtained from 9 monitoring wells located in peat bogs, with a varying degree of degradation, were used. Fluctuations in time series and potential linkages between selected variables were analysed in the frequency domain using the continuous wavelet transform. The results show that peat bogs exhibit a relatively high stability of groundwater table levels and groundwater temperature despite meaningful changes in weather conditions. The most visible response of peat bogs to weather conditions was observed in summer and autumn. Our study demonstrates that degraded peat bogs experience the largest decrease in groundwater table levels and more frequent fluctuations. In contrast, groundwater temperature remained stable throughout the year at all the studied bog sites.