<p>Forested riparian areas are valuable because they are rich in biodiversity and more productive than their adjacent upland areas, but they could be threatened by drought. The groundwater level of the riparian zone is an important parameter to quantify the forest hydrological processes thus for their survival. This study examines the influence of riparian zone groundwater level dynamics on the water balance of an alder forest. </p><p>Our research area is a streamside alder ecosystem at the eastern foothills of the Alps, in Hidegvíz Valley (Hungary) experimental catchment. We analysed the water table dynamics in the period 2017-2022 using seven manually detected groundwater wells data. In the case of a selected well, we measured groundwater levels using an automatic pressure probe with high frequency. The related meteorological parameters were also collected in the immediate vicinity of the area.</p><p>Using manually measured groundwater level data we found that in summer dry periods streamside water table fall below the level of the streambed causing the stream status changes from effluent to influent. </p><p>Using high frequency water table data we analysed groundwater temporal dynamic and relationship with other environmental parameters seasonally. According to our calculations alder forest ecosystem groundwater transpiration is great in hot rainless periods. As a conclusion these riparian forest types can be characterised as a vulnerable ecosystem  in the changing climate because long dry periods will become more and more common in the future.</p><p>Acknowledgement: This article was made in frame of the project TKP2021-NKTA-43 which has been implemented with the support provided by the Ministry of Innovation and Technology of Hungary (successor: Ministry of Culture and Innovation of Hungary) from the National Research, Development and Innovation Fund, financed under the TKP2021-NKTA funding scheme.</p>

<p>Riparian vegetation forms have strong dependence on hydrological factors. Forests and meadows in valley locations are strictly protected in many cases. Knowledge of the changes in their water balance in context of climate change is critical in terms of their survival.</p><p>We studied the hydrology of a riparian alder forest and a neighbouring wet meadow at the outlet of the Hidegvíz valley experimental catchment (eastern foothills of the Alps). Interception loss (significant element of forest water balance) and groundwater uptake importance were analyzed. LAI and forest structural parameters were measured for calculating interception and remote sensing information were also used. We settled groundwater wells for groundwater level dynamics analysis. Meteorological parameters that we used for this analysis were measured in an open-air plot next to the examined ecosystems.</p><p>Remote sensing data is useful for determination of LAI and so vegetation storage capacity dynamically in an interception model. Field interception measurement is important for exact model calibration. Measurements of groundwater levels with high frequency give us the possibility to determine groundwater dynamics and to estimate vegetation water uptake. On the basis of the results, interception loss and groundwater uptake of alder forest are significantly higher, so riparian forests have greater water demand for their survival in the changing climate.</p><p>Acknowledgement: Research was supported by TKP2021-NKTA-43 project. Project no. TKP2021-NKTA-43 has been implemented with the support provided by the Ministry of Innovation and Technology of Hungary from the National Research, Development and Innovation Fund, financed under the TKP2021-NKTA funding scheme.”</p>