Several major flood events of recent years have encouraged research focused on a better understanding of climatological and hydrological causes of floods. In practice, these findings can be used in flood risk management, and in the light of ongoing climate change, also in preparing effective adaptation strategies. This study builds on the results of the Wetrax+ research project which combined a stochastic weather generator and a high-resolution fully-distributed rainfall-runoff model to produce a unique dataset of 10 000 years of hourly simulations of air temperatures, precipitations and river discharges in the Upper Danube River basin. As the generated dataset accounted for the expected changes in the frequencies and persistence of the identified weather patterns, it was used to assess the possible changes in the very extreme flows in the study basin. The length of the dataset maintained that numerous flood events that were larger than the most extreme observed floods occurred in the dataset and were available for analysis. The results indicated that on average the floods should occur sooner in the year in most of the Upper Danube sub-basins. Moreover, the frequency of floods associated with weather patterns related to heavy precipitation also increased. Despite the predictions about the future, changes in weather pattern frequencies cannot be taken for granted the results of the study can be useful in identifying the sources and causes of the most extreme floods helping those responsible to focus their mitigation efforts on certain sub-basins.

How to cite: Valent, P., Komma, J., Breinl, K., Bertola, M., Haslinger, K., Lexer, A., Thanheiser, S., Homann, M., and Blöschl, G.: Assessment of the impact of expected changes in the frequency of weather patterns on extreme flows in the Upper Danube basin, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13990, https://doi.org/10.5194/egusphere-egu23-13990, 2023.

As the climate change and the research surrounding it intensifies, the assessment of the hydrological regime for the decision making processes also gains significance, as the design values are directly used for example for floods and droughts management.

In this contribution we have analysed changes in the long-term mean annual discharges at 113 water gauging stations with long term observations in the period 1961-2020 over different time periods. To identify potential changes in the hydrological regime, the analysis was focused on the comparison of the 10, 20, 30, 40, 50-year long moving averages of the long-term mean annual discharges in the period 1961-2020 in comparison with the 1961-2000 reference period currently used in Slovakia for calculation of design values.

The results point out that the new reference period to be used for calculating design values in Slovakia should include the time period after the year 2000, but to determine its precise length, more detailed analysis, especially in the area of the low flows, is needed.

Acknowledgement: This work was supported by the Slovak Research and Development Agency under the Contract no. APVV-20-0374.

How to cite: Jeneiova, K., Poorova, J., Danacova, Z., Melova, K., and Kotrikova, K.: Analysis of changes in long-term mean annual discharge in Slovakia, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5669, https://doi.org/10.5194/egusphere-egu23-5669, 2023.

Changes in the hydrological cycle are increasingly influenced by climate change. Every year, droughts and floods increase and strongly threaten the landscape, buildings, human settlements and lives. Climate data from climate scenarios are used to predict extreme events in the future. Many methods can process the climate data and evaluate the hydrological characteristics, according to which it is possible to determine the changes in the hydrological regime in the landscape.

The paper aims to characterize future changes in the hydrological regime for eight selected basins of Slovakia, which were divided into four groups according to location, i.e., eastern Slovakia, northern Slovakia, central Slovakia, and western Slovakia. The input data include mean daily discharges and are divided into four groups. The first group consists of observed daily discharges provided by the Slovak Hydrometeorological Institute and represents the reference period from 1981 to 2010. The second group generates mean daily discharges using the HBV type TUW rainfall-runoff model in 1981-2010. The third and fourth groups simulate mean daily discharges using the meteorological inputs from the KNMI and MPI climate scenarios, containing data from 1981 to 2100. The available data were inputs to The Indicators of Hydrologic Alteration program, and subsequent analyses are focused on mean monthly discharges, M-day minimum and maximum discharges, the occurrence of maximum and minimum discharge, and baseflow index. For assessing the future changes in hydrological regime characteristics, the reference and future period 2070-2100 were compared.

The results indicated that the spring's most significant decrease in mean monthly discharges occurred in eastern Slovakia. Summer is characterized by a decrease in mean monthly discharges throughout Slovakia, especially in eastern Slovakia. In eastern Slovakia, a decrease in selected M-day minimum discharges is also expected. Minor changes are expected in the characteristics of the 90-day minimum discharge Q_90d in the Topľa – Hanušovce and Topľou gauging station. The most significant changes can be expected in the Laborec - Humenné gauging station, where the 90-day minimum discharge Q_90d can decrease by up to 38% compared to the reference period. The results show a rise of M-day maximum discharges of up to 50% in the gauging stations in the eastern part of Slovakia. The minimum discharge is shifted from November/January to October and the maximum from March to February/March.

According to the increasing base flow index, the Váh River basin will have the best conditions for maintaining minimum discharges in drier periods. In the other basins, the values of the baseflow index decrease.

An increase in mean monthly discharges may indicate future, increasing precipitation in given basins, predominantly in liquid form, or, on the other hand, increasing temperatures that can eliminate snow cover.

Acknowledgement:

This study was supported by PhD student project ARPMP. The study was also supported by the Slovak Research and Development Agency under Contract No. APVV-20-0374.

How to cite: Sabová, Z., Németová, Z., and Kohnová, S.: Comparison of spatial and temporal future changes of hydrological regime in selected river basins of Slovakia, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6181, https://doi.org/10.5194/egusphere-egu23-6181, 2023.

The Thaya is a trans-national river basin that is situated in the Czech Republic and Austria. Different human activities in the basin and multiple water uses increase the water demand. This increase, combined with the recent droughts events in 2017 and 2018, has recently resulted in reconsidering the water management strategies for future climates. This contribution aims to evaluate the effect of climate change on the water balance of the Thaya. The aim is to apply two different hydrological models in an identical setting (the same model inputs, scenarios, and regional and water use data) and to identify water availability and its change under various climate and water use scenarios. The assessments compare BILAN and TUWmodel hydrological models coupled with the WATERRES water use module and a large sample of climate projections (the CMIP5 and CMIP6 models), which represent various socioeconomic pathways combined with projections of possible changes in water use. The results will demonstrate an insight into how the water balance in different parts of the Thaya basin has changed in the past and what are the possible effects of climate change on these water resources in the future.

How to cite: Parajka, J., Vizina, A., Komma, J., Valent, P., Štepánek, P., Haslinger, K., Schellander-Gorgas, T., Viskot, M., Fischer, M., Froschauer, W., Trnka, M., and Blöschl, G.: Impact of climate change on the water balance of the Thaya basin, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14941, https://doi.org/10.5194/egusphere-egu23-14941, 2023.

Abstract 

Climate change and anthropogenic activities could have extensive impacts of coastal areas especially Deltas and lowlands that may be extremely affected by sea level rise and different human activities. According to the IPCC reports, the mean sea levels have been raised between 10 to 20 cm over the last century and expected to rise between 20 to 88 cm at the end of the current century. If no actions are taken, this rise could have extensive effects on coastal areas such as shoreline erosion, submergence of coastal cities and increasing the seawater intrusion into coastal aquifers. Also, anthropogenic activities including changes in the land use could increase such effects. This study aims to highlight the effect of climate change and anthropogenic activities on the Nile Delta of Egypt. The study focusses on the eastern part of the Nile Delta (Port Said governorate) where many changes in the land use have been observed in the last decades. The effect of climate change and anthropogenic activities on the Nile Delta are detected using GIS, RS data and numerical models. The Digital Shoreline Analysis System (DSAS) with ArcGIS are used in monitoring the shoreline change (SLC) based on satellite images for 50 years from 1974 to 2023. GIS is used to monitor shoreline changes and forecast future changes for the next 10 and 20 years. The results indicated that the shoreline had shifted inland with varying values along the coasts between 1974 and 2023, and the predictions indicated that it would continue to shift in 2034 and 2044. The rate of shoreline loss was 14 m/year from 1974 to 2000 and 16 m/year from 2001 to 2023 and predicted to be 12 m/year from 2023 to 2044. RS and GIS are used for investigating the land use changes (LUC) over the last 50 years for the period from 1974 to 2023 based on satellite images that were geometrically corrected by Supervised Classification to identify LUC in the Nile Delta. The results for the study period from 1974 to 2023 (50 years) reveal that urbanization has increased 18%, vegetation cover has increased 22%, water bodies and fish farms increased 40% and the bare land decreased 60% due to the development of the area in the studied period. The Eastern part of the Nile Delta is enormously affected by climate change and anthropogenic activities which require application of protection measures. Significant changes in shoreline and land cover for the study area were observed in the period from 1974 to 2023. Policy makers may use the results of this study to develop adaptation plans to safeguard the Nile Delta from anthropogenic activities and climate change.

Keywords: Climate change, anthropogenic activities, shoreline change (SLC), land use change (LUC), RS and GIS, Nile Delta of Egypt.

How to cite: Abd-Elhamid, H., Zeleňáková, M., Kabeel, A. E., Mahdy, M., Barańczuk, J., and Barańczuk, K.: Assessment of climate change impacts and anthropogenic activities on the eastern part of the Nile Delta of Egypt, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8647, https://doi.org/10.5194/egusphere-egu23-8647, 2023.

In the effort to successfully sustain the forests in Hungary: the most important limitation factors are the available water sources and the climate conditions. As the expected effects of the climate change (e.g.: decrease of precipitation in the vegetation period, the increase in frequency of the extreme intensity precipitation events, increase of the length of drought periods, increase of the evapotranspiration due to the mean temperature increase) this will be an increasing challenge to the forest managers in future. The forest stands have an ability to reduce the temperature, increase the humidity and soften the drying effect of the strong wind. So, the protection of our forest stands will become the one of most important tasks in our future. Thus, the research of the interconnection between the forests and the hydrological cycles is an urgent meanwhile difficult task due to the complexity of these systems. Our recent work presents the main conclusions of the recent drought period by our hydro-meteorological system.

Acknowledgements:

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.

How to cite: Bolla, B. and Horváth, B.: What are the effects of forests on the hydrological cycle in connection with the changing climate?, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3342, https://doi.org/10.5194/egusphere-egu23-3342, 2023.

Rising El Niño–Southern Oscillation (ENSO) variability is expected to influence Earth’s forest ecosystems, through changes in how coordinated annual tree growth is across large spatiotemporal scales. However, the mechanisms by which changes in ENSO variability affect tree growth remains poorly understood, especially in understudied subtropical forests. We use a newly built tree ring network collected from 4,028 trees at 144 forest locations across East Asian subtropical forests (EASF) at subcontinental scales (∼2,000 km), to assess long-term influences of ENSO on the spatiotemporal variability in tree radial growth across China. Our results demonstrate a west-east dipole pattern of synchronized tree growth in EASF moisture-limited tree populations, with positive growth responses to El Nino in southeastern China, and negative growth responses in the southwestern China. Specifically, trees grew more in El Niño years in eastern populations, but less in western populations. This pattern likely results from the contrasting effects of ENSO on drought limitation along a longitudinal gradient. Our results also show that increasingly severe El Niño/La Niña years have caused a sharp rise in tree growth coherence over past 150 years in these moisture-limited populations. A further increase in climate variability, as is expected with climate change, could destabilize subtropical forest ecosystems by synchronizing tree growth to an unprecedented level. In all, our results highlight the need for further research on the ecological implications of rising synchrony, given its increasing relevance to global forest ecosystems in a time of rising climate variability.

How to cite: Su, J., Gou, X., HilleRisLambers, J., Zhang, D., Zheng, W., Xie, M., and Manzanedo, R.: Increasing ENSO variability synchronizes tree growth in subtropical forests, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-12726, https://doi.org/10.5194/egusphere-egu23-12726, 2023.

Forests are increasingly exposed to extreme global warming-induced climatic events. However, the immediate and carry-over effects of extreme events on forests are still poorly understood. Using eddy covariance data from 34 forest sites in the Northern Hemisphere, we analyzed the responses of ecosystem gross primary productivity capacity under light saturation (GPP2000) of forest ecosystems to late spring frost (LSF) and growing season drought. The immediate and carry-over effects of frost and droughts on needle-leaf (NF) and broadleaf (BF) forests were analyzed. Path analysis was applied to reveal the plausible reasons behind the varied responses of forests to extreme events. The results show that LSF had clear immediate effects on the GPP2000 of both NF and BF. However, GPP2000 of NF was more sensitive to drought than that of BF. There was no interaction between LSF and drought in either NF or BF; instead, drought effects were masked by the LSF effect in NF. Path analysis further showed that the response of GPP2000 to drought differed between NF and BF, mainly due to the difference in the sensitivity of canopy conductance. Moreover, LSF had a more severe and long-lasting carry-over effect on forests compared to drought. These results enrich our understanding of the mechanisms of forest response to extreme events across forest types.

How to cite: Chen, L.: Immediate and carry-over effects of late spring frost and growing season drought on forests in the Northern Hemisphere, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-2442, https://doi.org/10.5194/egusphere-egu23-2442, 2023.

The combination of flash droughts and high temperature may have a significant effect on the ecosystem because of the soil and atmospheric moisture deficits. However, the stress of soil and atmospheric moisture deficits on carbon and water use of the ecosystem during flash droughts, particularly during the drought periods with hot conditions, are unclear over a large region. In this study, we decoupled the atmospheric and soil water stress over eastern China by using vegetation remote sensing products during flash droughts and their sub-periods that are accompanied by high temperature and intense radiation. The results showed that soil moisture (SM) stress on gross primary productivity (GPP) was significantly greater than the vapor pressure deficit (VPD) stress over eastern China, especially in humid area. In contrast, the atmospheric water stress in the North China Plain was more significant. By excluding the radiation effect, high VPD dominated the water stress on light use efficiency (LUE) in over 55% of the areas during flash droughts. For the hot periods of flash droughts, the GPP subject to VPD stress increased from 8% to 36% of the areas, especially in semi-arid and semi-humid regions. The concurrent hot and drought conditions also increased water use efficiency (WUE) for most areas. Moreover, the effect of water stress on LUE and WUE was similar to that during flash droughts. The reason may be that during hot periods of flash drought, the rise in VPD led to a decrease in vegetation stomatal conductance, which further reduced GPP, photosynthetically active radiation absorbed by vegetation and evapotranspiration at the similar rate.

How to cite: Xi, X. and Yuan, X.: Atmospheric and soil water stress on ecosystem carbon and water use during flash droughts, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-4061, https://doi.org/10.5194/egusphere-egu23-4061, 2023.

Ecosystem functioning is impacted by the rising intensity and frequency of climatic extremes. Given the substantial evidence of the impacts of climatic extremes on ecosystem productivity, plant ecologists have been fascinated by the role of species richness in sustaining ecosystem functioning and stability under climatic extremes. Using the above-ground net primary productivity (ANPP) and climate data of a long-running (1997-2020) biodiversity experiment in Bayreuth, Germany, we examined the (i) effects of climatic conditions on species richness and ANPP, and (ii) role of species richness on resistance and resilience of ecosystem under different climatic conditions. Bayreuth Biodiversity Experiment was established in 1996, which comprises 64 plots (each plot is 2m×2m in size). Biomass was harvested twice a year (June and September) at 5 cm above the ground within the centre of each plot. We employed the Standardized Precipitation Evapotranspiration Index (SPEI) to classify the growing season (3-month SPEI) and annual (12-month SPEI) climatic conditions (ranging from extreme wet to extreme dry conditions) into a 5-class and 7-class climatic conditions classifications. A number of pairwise tests (ANOVA and post-hoc) were used to assess the differences in species richness and ANPP among various climatic conditions. We utilized generalized linear models to assess the relationships between species richness and ANPP, and linear mixed-effects models to examine the relationships between species richness and resistance and resilience under different directions (e.g., dry or wet) and intensities (e.g., extreme, moderate and mild) of climatic conditions. Results show that ANPP varied greatly with respect to climatic intensity and direction, peaking in extreme wet conditions and declining in extreme dry ones. Species richness and ANPP formed a concave-up (unimodal) pattern for the dry conditions and a negative linear (positive linear) pattern for the wet conditions in June (September) harvests. Species richness increased ecosystem resistance regardless of intensity, direction and classification of climatic conditions, while decreased ecosystem resilience towards dry climatic conditions. Ecosystem resilience remained steady towards wet climatic conditions. Our study stresses the importance of maintaining a community with higher species richness to stabilize ecosystem functioning and enhance resistance to various climatic conditions.

How to cite: Hossain, M. L., Li, J., Hoffmann, S., and Beierkuhnlein, C.: Divergence of ecosystem functioning and stability under climatic extremes in a 24-year long-term grassland experiment, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-17067, https://doi.org/10.5194/egusphere-egu23-17067, 2023.

Abstract

USLE (Universal Soil Loss Equation) was used as a standard tool for evaluating Slovakia's water erosion risk. Understanding interactions between land cover, land use management, and topographical properties of the land are essential to effectively control soil erosion by implementing best management practices. Two ways for LS factor calculation are recommended for use in practice. The first way is in the computing method based on the USLE 2D software, and the second is the other computing algorithms. Various forms can assess the LS factor but with different results. This article aimed to show the differences in LS factor assessment methods in the Myjava Hills – Sobotište study area, a small agricultural area strongly threatened by water erosion. All in two variants before and after the application of anti-erosion measures (water retention grass ditch). Changes in the LS factor were directly indicated in calculating the long-term average soil loss by water erosion. After applying a complex system of anti-erosion measures, results show a significant reduction of the mean long-term soil loss by water erosion in both comparisons.

Keywords: USLE, LS factor, anti-erosion measures, soil loss

Acknowledgement: This study was supported by PhD student project LABEX. The study was also supported by the VEGA grant agency under the contract numbers VEGA 1/0632/19.

How to cite: Tomaščík, M., Danáčová, M., Grečnárová, J., Výleta, R., and Hlavčová, K.: Evaluating the erosion risk using the USLE tool in a small agricultural area, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5311, https://doi.org/10.5194/egusphere-egu23-5311, 2023.

Soil erosion and sediment loading are mainly caused by extreme events with rare occurrence. Thus, long term observation is necessary for identification of causes and factors that trigger the erosion process and lead to the generation of river sediment.

To investigate the main drivers of erosion in the catchment of the Hydrological Open Air Laboratory (HOAL) Petzenkirchen, we performed time series analyses for the period of 2002-2022, including agricultural land use, precipitation, discharge and sediment load with high temporal and spatial resolution. The HOAL Petzenkirchen, located in the alpine forelands of Lower Austria, extends to 66 ha and is mainly used for intensive agriculture.

To highlight the effect of heavy precipitation events, a 100-year flood event that occurred in 2021 is analysed in detail to demonstrate the immense impact of such events on the sediment loading.

How to cite: Rab, G., Krammer, C., Brunner, T., Schmaltz, E., Széles, B., Blöschl, G., and Strauss, P.: Analysis of erosion drivers in the Hydrological Open Air Laboratory Petzenkirchen, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-7340, https://doi.org/10.5194/egusphere-egu23-7340, 2023.

Biochar application is considered a beneficial strategy for improving soil ecosystem services and also takes place in carbon sequestration, decreasing greenhouse gas emissions, renewable energy, elimination of waste, and as a soil remedy. The literature reports that, in general, biochar application reduces runoff by 5-50% and soil loss by 11-78%, suggesting that it may be effective in reducing water erosion, but the extent of erosion reduction is highly variable. The main mechanism by which biochar can reduce water erosion is by improving soil properties (i.e., organic carbon, hydraulic conductivity, aggregate stability) that affect soil erodibility.
The subject of this study is the application of a relatively new approach to estimating soil erosion in small catchment using the physically-based erosion Erosion-3D model. The model has been developed as a physically-based model for predicting soil erosion by water on agricultural land, amount of runoff and sediment concentration.  Erosion-3D model is predominantly built on physical principles and simulates surface runoff, erosion, deposition and separation of soil particles for individual events and provides a beneficial tool for simulating and quantifying soil erosion.
The impact of biochar application on soil water erosion was determined for several scenarios in order to cover various condition and reflect the answer of biochar application to different soil properties. Based on the results, it can be concluded that the application of biochar has a positive effect on erosion activity to a certain extent.
The positives and negatives of biochar application to different soil properties were identified and provide a useful basis for further research.

Keywords: Erosion 3D model, biochar, soil water erosion, physically-based model

This article was created with financial support from the project of the Scientific Grant Agency VEGA 2/0155/21.

How to cite: Roncak, P., Nemetova, Z., Vitkova, J., Botkova, N., and Tokova, L.: Effect of biochar application on soil hydrophysical properties and erosion potential, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5986, https://doi.org/10.5194/egusphere-egu23-5986, 2023.

This case study focuses on climate change adaptation strategy for densely urbanised areas. The phenomenon of heavy urbanization has significantly intensified during the last decades. Building constructions are still expanding, resulting in the decline or even elimination of green spaces. Not only does it cause the eradication of green spaces, but it also prevents unbuilt areas from the further development of green infrastructure. The pressure of developers urges the maximum use of urban areas for financial profit at the expense of greenery, which does not generate such profit. However, the benefits of greenery on human health are more significant, hence it is necessary to educate the public about these positive aspects and create and promote adaptation strategies for climate change. Furthermore, hydrological extremes are increasingly and more regularly repeating during the year, and it is necessary to create a green infrastructure to mitigate the impacts of these extremes. In severely and densely urbanised spaces, such as the historic city centres, there is no longer an option to provide areas for the possible further creation of green spaces. Therefore, in this case study we focused on the possibility of creating green infrastructure using the vertical gardens and bringing all the benefits of green spaces to vertical dimension, which does not require any land space. The example of the Old Town district of Bratislava, Slovakia was used in this case study. This proposal presents a selection of possible spaces for the creation of vertical gardens, which are also designed as an information system for visitors navigating them from major transport hubs to the city centre.

How to cite: Majorošová, M. and Zaťovičová, M.: The elimination of climatic extremes using vertical gardens in densely urbanised areas, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6366, https://doi.org/10.5194/egusphere-egu23-6366, 2023.

In recent years, the changing weather patterns caused by climate change have already impacted the population, but in 2022, these weather extremes surpassed the ones of previous years. Severe droughts across Europe posed significant challenges, primarily through water scarcity and caused severe (security of supply and economic) damages to different societal sectors. Drier summers and warmer, snow-less winters significantly change the water cycle and thus the amount of naturally retained rainwater on site. A long-term, sustainable solution is the widespread implementation of nature-based solutions.

The Lake Velence watershed in Hungary has been showing signs of drying up for years. To implement nature-based solutions, the catchment's natural features, the stakeholders' general requirements, the economic opportunities, and possible benefits must be incorporated. Small- and large-scale agricultural activities face a growing deficit in irrigation water, while the surrounding settlements of Lake Velence can collect a significant amount rainwater. The research focuses on the potential amount of rainwater that can be collected in the selected hilly settlements, it’s uses, and its ability to generate additional income. We evaluated the costs and benefits of implementing or non-implementing nature-based solutions based on the extent of rainwater usage. Using basic calculations of the area's present and possible future cultivation/agricultural activities, we examined the impacts of blue-green infrastructures on local GDP through a lost profit versus available surplus income comparison.

How to cite: Kalman, A. and Bene, K.: Financial benefits from the implementation of nature-based solutions in the settlements – a case study on a catchment of Lake Velence, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-9476, https://doi.org/10.5194/egusphere-egu23-9476, 2023.

Shallow urban groundwater is habitat of microorganisms as well as invertebrate fauna. Both communities are assumed to be strongly influenced by multiple stressors, such as increased groundwater temperatures and enhanced local hydraulic fluctuations, acting in the urban subsurface. To date, ecological studies mainly focused on natural and arable environments, with little attention to biodiversity and the role of anthropogenic factors in urban groundwater habitats. Our project targets the subterranean regime of the city of Halle (Saale) as an ideal benchmark to explore spatial and temporal dynamics of subsurface biodiversity on the urban scale. The unique hydrogeological setting of Halle, which covers a broad range of different aquifer types, with characteristic subsurface urban warming, allows for the evaluation of selected abiotic factors related to hydraulics, hydrochemistry and temperature trends. We expect new insight into the individual and concerted role of these factors on groundwater microorganisms and fauna.

First data were collected within a field campaign in June/July 2022. Physico-chemical parameters in groundwater were recorded with a multiparameter probe at each sampling point. Hydrochemical analysis including major anions and dissolved organic carbon (DOC) was conducted with the water samples from the wells and freshly pumped groundwater. Groundwater animals were collected from the bottom of the wells with a net sampler. Animals were sorted and counted at the level of higher taxonomic groups (e.g. amphipods, copepods, isopods, ostracods, oligochaetes, nematodes, and mites). In the presentation, first results on the hydrogeology, hydrochemistry, microbiology and faunal diversity of the urban center and surroundings of Halle are introduced. We show major spatial trends and how faunal abundance and diversity relates to direct urban temperature effects and zones of anoxic conditions. Moreover, research activities planned for the near future will be discussed.

How to cite: Becher, J., Gardt, K., Meyer, L., Griebler, C., Hermann, M., and Bayer, P.: Hydrogeological, physicochemical, and thermal conditions as drivers of faunal diversity in an urban groundwater ecosystem, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14570, https://doi.org/10.5194/egusphere-egu23-14570, 2023.

Climate change can be characterized by a definite warming trend with its most significant impact on the water cycle through altering precipitation and evapotranspiration processes. The anticipated changes induce the higher water consumption of plants, thus a lower groundwater table may appear and the regeneration of groundwater-dependent forest communities are called into question. In Hungary, woodlands on the plains with high water requirements and wetlands are particularly affected.

Kaszó LIFE project is a respectable example of positive water supply interventions (for groundwater-dependent forest ecosystems). This project aimed the water supply’s improvement of the forests, small fens and grasslands at West Inner-Somogy micro-region, in the Szentai forest, utilizing log weirs and lake rehabilitation to restore the degraded habitats.

The goal of this study is the analysis of the hydrological impacts of water supply interventions on the groundwater level. In case of three different forest ecosystems water balance modeling was also carried out to analyze in a complex way the effects of the interventions.

The main conclusion of this work is that, however, the rehabilitation of lakes and the construction of new ones significantly affected the water levels in the surrounding groundwater wells, but the effects of the log weirs were undetectable.

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.

How to cite: Kalicz, P., Herceg, A., Horváth, L., and Gribovszki, Z.: Water supply impacts on forest’s groundwater levels with water-balance analysis: a case study at Szentai forest (Hungary), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13698, https://doi.org/10.5194/egusphere-egu23-13698, 2023.

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. 

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.

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. 

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.

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.

How to cite: Gribovszki, Z., Herceg, A., Holik, B., Nevezi, C., Kalicz, P., Bazsó, T., Brolly, G., and Zagyvai-Kiss, K. A.: Spatial and temporal water table dynamic of a common alder riparian forest, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13980, https://doi.org/10.5194/egusphere-egu23-13980, 2023.

We made our investigation in the Gemenc forest, which is situated beside the Danube river near the southern border of Hungary. Mainly the Danube and in the last decades, watercourse management played a significant role in landscape evolution. Most of the area is on the saved side today, so it doesn’t get flooded. The Danube usually brings calcium carbonate to this area with its sediment. The flooded areas are built from fine sediment materials. Meadow soils rich in calcium carbonate are characteristic, and the forests of this land grow healthy here (assuming that are high-quality forest types). Farther away from the river, higher plains have sand with humus soils and Chernozem soils.

Forest ecosystems of this area are probably one of the most important members of the continental vegetation that stores carbon. Because of their size, they take huge part of the global carbon cycle. The amount of carbon stored in the soil – similar to the carbon stored in wood- and the consequences of human activities on this carbon are less known in Hungary. The reason for this is the small amount of information we have about this topic. During our examinations, we visited six Quercus petraea and Robinia pseudoacacia forests and measured the carbon stock of those forest soil besides the determination of water holding capacity. The humus content of the examined soil samples varied between 0.7 and 6.9 %. Since the study areas are no longer or rarely affected by flooding, the highest organic matter content was found in the topsoil layer for each sample. SOM content gradually decreased with depth. The effect of flooding is clearly shown by the fact that we found organic matter in the samples even in the layer below 100 cm, and in several cases, we found buried humus levels. Accordingly, the organic carbon stock of these soils may be higher than average. However, the decreasing number of floods endangers the vitality of forest stands. With less flooding, decreasing groundwater level, and an increase in the temperature at night, dew formation becomes more limited, and evaporation increases. These changes also affect the decomposition processes taking place in the soil, the circulation of nutrients, and soil respiration. Increasing temperature, the speed of decomposition, and the intensity of soil respiration increase, which can further increase the decrease in the soil's C pool.

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.

How to cite: Horváth, A., Szász, D., Balázs, P., Végh, P., and Bidló, A.: Carbon stock of the Gemenc forest (Hungary), EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14221, https://doi.org/10.5194/egusphere-egu23-14221, 2023.

In our study, we analysed the long-term land cover changes and soils of the Erebe-islands forest reserve (Hungary). The historical land cover investigation is based on digitized military survey maps dating back to the 18^th century and the lately finished national ecosystem basemap. Based on the analysed map series in the core area forests first appeared in the middle of the 20^th century. The buffer zone was covered by water and grassland until the first half of the 20^th century. Results can contribute to the investigation of interrelations between historical land use and actual soil and vegetation properties, especially carbon storage.

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.

How to cite: Balázs, P., Horváth, A., Végh, P., and Bidló, A.: Historical land cover changes of the Erebe-islands forest reserve (Hungary) and their effects on carbon cycle, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-14513, https://doi.org/10.5194/egusphere-egu23-14513, 2023.

Evapotranspiration has an essential role in the hydrological cycle by affecting the volume of surface runoff and the amount of available water on the land. It is an input parameter for many hydrological models based on water balance; it is an important parameter for calculating agricultural land irrigation and water management. In the current hydrology, the role of evapotranspiration is increasingly important because of global warming and the increasing occurrence of drought. Many methods for evaluating drought are based on the value of Actual evapotranspiration, which is not directly measured, and data about this variable are not available from a national database. For this reason, the Reference evapotranspiration, which can be calculated from more frequently measured meteorological variables, is gaining in importance. FAO Penman-Monteith (P-M) method is a method for the calculation of Reference Evapotranspiration recommended by many international organizations and worldwide used by researchers like reference method in research. However, the high demand for required P-M method input meteorological parameters caused its difficult usability in the case of research covering large regions. For this reason, the methods less demanding on inputs for reference evapotranspiration calculation were derived. The accuracy of this method is necessary to verify in local conditions.

This research aims to describe the spatial and temporal distribution of reference evapotranspiration and evaluate the Hargreaves method accuracy in the selected stations of Slovakia. The punctuality of the Hargreaves method showed a positive correlation with the increasing altitude of the Climatological station. The correlation coefficient of P-M and Hargreaves reaches more accuracy in comparing monthly values for all Climatological stations. The results bring information about the usability of the Hargreaves method in different conditions, which is mainly essential for hydrological modelling.

This publication is the result of the project implementation: „Scientific support of climate change adaptation in agriculture and mitigation of soil degradation” (ITMS2014+ 313011W580) supported by
the Integrated Infrastructure Operational Programme funded by the ERDF; and was supported by the Slovak Research and Development Agency under Contract No. APVV-18-0347; and grant number VEGA 1/0782/21.

How to cite: Rattayová, V., Garaj, M., Kandera, M., and Hlavčová, K.: Evaluation of Hargreaves method for calculation of reference evapotranspiration in selected stations of Slovakia, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-1712, https://doi.org/10.5194/egusphere-egu23-1712, 2023.

Reliable flood risk management needs to correctly estimate and design the size of volumes in reservoirs, spillways of dams and flood levees. To design secure and well-serving hydraulic structures, we often need to use design flood hydrographs that allow a sufficient description of the impacts of flood events in many cases.

In this study, a methodology is proposed based on using both empirical and statistical approaches for constructing nonparametric synthetic design flood hydrographs. It is based on flood hydrographs that are observed in the hourly discharge time series, in which is respected the dependence among the peaks, volumes and duration of a set of observed seasonal flood hydrographs. The method consists of seasonality analysis of floods, sampling of seasonal flood hydrographs, normalization of the hydrographs into flood fragments, dependence modelling of peaks, volumes and durations using the vine copulas, rescaling of hydrograph fragments with the appropriate design flood into synthetic design hydrographs and determining the joint conditional return period of the flood volume and the duration conditioned on the flood peak for each synthetic hydrograph.

By that, the designer is furnished with a set of design flood hydrographs, which have diverse shapes, volumes, and durations for a selected design discharge with a known joint conditional return period of the volumes and durations for flood risk analysis.  The method was tested and carried out on gauged discharge data from the Horné Orešany reservoir in the watershed of the Parná river in Slovakia. Using flood regionalization approaches can be this method also applicable to ungauged catchments.

Acknowledgements:

This study was supported by PhD student project SYLUETI.  The study was also supported by the Slovak Research and Development Agency under Contract No. APVV-20-0374.

How to cite: Liová, A., Výleta, R., Hlavčová, K., Kohnová, S., Bacigál, T., and Szolgay, J.: A vine copula-based approach for constructing nonparametric synthetic design flood hydrographs, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6179, https://doi.org/10.5194/egusphere-egu23-6179, 2023.

The observations made from satellite technology enable more and more scientific communities to test and rely on this kind of product. Moreover, data acquired from satellite products is of great use regarding conceptual hydrological modeling. This study represents the process of testing the advanced scatterometer (ASCAT) remote sensing product-ASCAT SWI. In regions with little or no data, soil moisture products have significant value. They represent the relationship between surface and root zone soil moisture as a function of time. SWI represents the soil moisture content equal to a soil depth of 1 meter represented in percentage (%), with a minimum of 0% and a maximum value of soil moisture at 100% of soil capacity. In this study, the tested data in focus are soil moisture data with changing values of modeled water infiltration into the different soil layers (T). In addition to these data, the hydrometeorological data are used for hydrological modeling. These are data from water gauge stations such as runoff values (Q), precipitation (P), air temperature (T), and potential evapotranspiration (PET). All the data used in the hydrological model represent the time series from 01.01.2007 to 31.12.2019. The spatial resolution of the datasets is 500x500 meters, and the temporal resolution is one day. Calibration was performed using the lumped hydrological model developed at Technical University in Vienna-TUWdual. Areas of interest in modeling are selected catchments in Slovakia with various land use and height above sea level. Another aim of this study is to test the correlation between the measured soil moisture and the modeled one using the TUWdual model. The expected outcome of the study should point out the catchment areas that would benefit more from the additional data on satellite soil moisture in Slovakia.

Acknowledgment: This study was supported by a Ph.D. student project HYDRODIAĽ.

How to cite: Aleksić, M., Kubáň, M., Paulíková, L., Hlavčová, K., and Szolgay, J.: Exploring the impact of satellite products on the calibration of the conceptual hydrological model, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6334, https://doi.org/10.5194/egusphere-egu23-6334, 2023.

The rainfall-runoff process transforms a precipitation input to a catchment into runoff output and is an important indicator for river water quality and quantity. Since runoff events are comprised of precipitation event water and stored pre-event water of the catchment, exploring the event and pre-event components of runoff events using the stable isotopes of water (δ¹⁸O, δ²H) and two-component and ensemble isotopic hydrograph separation may further our insights into overall catchment behaviour and the origin of water. The aim of this study is to investigate the origin of water for different streamflow gauges in a small agricultural catchment that represent different runoff generation mechanisms. The analysis is performed at the Hydrological Open Air Laboratory (HOAL) in Austria, which is a 66 ha experimental catchment dominated by agricultural land use. One of the main features of this research catchment is that several tributaries of the catchment representing different runoff generation mechanisms are gauged. Two-component and ensemble isotopic hydrograph separations (for both δ¹⁸O and δ²H) are conducted for three streamflow gauges (the catchment’s inlet and outlet and a tile drainage system) for multiple events in the warm periods of 2013-2018. The results of the two methods are compared and discussed for different runoff generation mechanisms.

How to cite: Széles, B., Holko, L., Parajka, J., Wyhlidal, S., Schott, K., Stumpp, C., Stockinger, M., Hogan, P., Pavlin, L., Rab, G., Strauss, P., and Blöschl, G.: Isotopic hydrograph separation in the Hydrological Open Air Laboratory, Austria, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8592, https://doi.org/10.5194/egusphere-egu23-8592, 2023.