Jan Szolgay
@stuba.sk
Faculty of Civil Engineering, Dept. of Land and Water Resources Management
Slovak University of Technology
RESEARCH INTERESTS
Hydrology
Scopus Publications
Scopus Publications
Anna Liová, Roman Výleta, Kamila Hlavčová, Silvia Kohnová, Tomáš Bacigál, Jana Poórová, and Ján Szolgay
Akademiai Kiado Zrt.
AbstractDesign flood hydrographs are often used to project safe and cost-effective hydraulic structures. This study proposes a system based on a combination of empirical and statistical approaches for constructing synthetic design flood hydrographs, that practitioners can easily apply. The system uses scaled observed seasonal flood hydrographs and respects the dependence structure among the flood peaks, volumes, and durations deduced from the set of seasonal flood hydrographs observed. The method was developed and tested based on data from the Horné Orešany reservoir in Slovakia.
András Szabó, Zoltán Gribovszki, Ján Szolgay, Péter Kalicz, Kitti Balog, József Szalai, Kamila Hlavčová, and Bence Bolla
MDPI AG
The process of groundwater evapotranspiration and its subsequent recharge are fundamental aspects of the Earth’s natural water cycle and have significant implications for the preservation and functionality of various forested ecosystems. This study presents a case analysis examining the recent fluctuations in groundwater levels and their replenishment in two wells situated at a designated forested experimental area and a control site. The magnitude and temporal fluctuations of groundwater recharge were examined through the utilisation of a novel adaptation of the traditional White method, which was specifically tailored to the local context. We also tested the sensitivity of the White method as an indicator of the system’s behaviour because the signal has changed in relation to the access of the forests to groundwater under the conditions of regionally declining groundwater resources and a warming climate. The novelty of this approach is found in the examination of the temporal fluctuations in groundwater recharge, which are influenced by both a decrease in groundwater levels caused by forest evaporation in response to climate change and a regional reduction in groundwater supplies. As a result, the ongoing decrease in groundwater levels may have significant adverse effects on local forests.
Miriam Bertola, Günter Blöschl, Milon Bohac, Marco Borga, Attilio Castellarin, Giovanni B. Chirico, Pierluigi Claps, Eleonora Dallan, Irina Danilovich, Daniele Ganora,et al.
Springer Science and Business Media LLC
Roman Výleta, Kamila Hlavčová, Silvia Kohnová, Tomáš Bacigál, Anna Liová, and Ján Szolgay
Central Library of the Slovak Academy of Sciences
Martin Kuban, Juraj Parajka, Rui Tong, Isabella Greimeister-Pfeil, Mariette Vreugdenhil, Jan Szolgay, Silvia Kohnova, Kamila Hlavcova, Patrik Sleziak, and Adam Brziak
Walter de Gruyter GmbH
Abstract In a previous study, the topsoil and root zone ASCAT satellite soil moisture data were implemented into three multi-objective calibration approaches of the TUW hydrological model in 209 Austrian catchments. This paper examines the model parametrization in those catchments, which in the validation of the dual-layer conceptual semi-distributed model showed improvement in the runoff simulation efficiency compared to the single objective runoff calibration. The runoff simulation efficiency of the three multi-objective approaches was separately considered. Inferences about the specific location and the physiographic properties of the catchments where the inclusion of ASCAT data proved beneficial were made. Improvements were primarily observed in the watersheds with lower slopes (median of the catchment slope less than 15 per cent) and a higher proportion of farming land use (median of the proportion of agricultural land above 20 per cent), as well as in catchments where the runoff is not significantly influenced by snowmelt and glacier runoff. Changes in the mean and variability of the field capacity parameter FC of the soil moisture regime were analysed. The values of FC decreased by 20 per cent on average. Consequently, the catchments’ water balance closure generally improved by the increase in catchment evapotranspiration during the validation period. Improvements in model efficiency could be attributed to better runoff simulation in the spring and autumn month. The findings refine recommendations regarding when hydrological modelling could consider satellite soil moisture data added to runoff signatures in calibration useful.
András Szabó, Zoltán Gribovszki, Péter Kalicz, Ján Szolgay, and Bence Bolla
Walter de Gruyter GmbH
Abstract The decline in groundwater levels is a cause of concern in many regions of the world, including the Sand Ridge of Hungary. The causes of the regional depletion range from rising air temperatures, changes in precipitation, domestic and agricultural groundwater use and past amelioration and recent afforestation, including the effects of drilling for crude oil exploration. The relations between the decline, the soil water regime and groundwater recharge under existing aged forests remained unclear thus far. Based on our monitoring of groundwater and soil moisture we aim to clarify this interplay in a new experimental site on the hilltop of the Sand Ridge. We compared three land-uses: a 41-year-old black locust (Robinia Pseudoacacia) offshoot forest, an 83-year-old first generation black pine (Pinus nigra) forest, and a grassland control site. The observed differences in the soil moisture profiles and dynamics were connected to the use of water by the given type of vegetation. We indicated a connection between the disruption of the groundwater recharge and the loss of contact of the rooting system of the forests with the deepening of the unconfined aquifer. Even if the aged forests could locally contribute to the decline, we conclude that the decline at the hilltop site that may be more strongly driven by other regional factors.
Pavel Raška, Nejc Bezak, Carla S.S. Ferreira, Zahra Kalantari, Kazimierz Banasik, Miriam Bertola, Mary Bourke, Artemi Cerdà, Peter Davids, Mariana Madruga de Brito,et al.
Elsevier BV
Martin Kubáň, Juraj Parajka, Ján Szolgay, Silvia Kohnová, Kamila Hlavčová, Patrik Sleziak, and Adam Brziak
Central Library of the Slovak Academy of Sciences
Anna Liová, Peter Valent, Kamila Hlavčová, Silvia Kohnová, Tomáš Bacigál, and Ján Szolgay
Central Library of the Slovak Academy of Sciences
Recent changes in climatic characteristics and consequent changes in the discharges and in the hydrological response of watersheds raise questions about the safety of water structures. Changes in flood wave characteristics (shape, volume, peak flow) may significantly affect the functionality of these structures. The study proposes a methodology for constructing design wave and flood hydrographs using discharge time series. A case study was carried out in the Little Carpathians watershed of the Parná River, above the profile of the Horné Orešany reservoir in Slovakia. The volumes and characteristic shapes of the flood waves with the maximum annual and seasonal discharges were determined using the Floodsep software. Subsequently, the T -year annual and seasonal discharges were estimated. Then, for pairs of the T year discharges and the associated volumes of flood waves, a joint probability distribution was constructed by copula functions. The associated volume of the T -year peak discharges was selected from the copula, and the probability of exceeding it was determined. Based on this analysis, a set of annual and seasonal control flood waves with the design maximum discharge, the associated volume with the selected probability, and the typical shape of the flood wave was constructed. This research provides satisfactory results for designing control waves necessary for assessing water structures with extreme loads and establishing a functional methodology for assessing other water structures in the region.
Patrik Sleziak, Roman Výleta, Kamila Hlavčová, Michaela Danáčová, Milica Aleksić, Ján Szolgay, and Silvia Kohnová
MDPI AG
The changing climate is a concern with regard to sustainable water resources. Projections of the runoff in future climate conditions are needed for long-term planning of water resources and flood protection. In this study, we evaluate the possible climate change impacts on the runoff regime in eight selected basins located in the whole territory of Slovakia. The projected runoff in the basins studied for the reference period (1981–2010) and three future time horizons (2011–2040, 2041–2070, and 2071–2100) was simulated using the HBV (Hydrologiska Byråns Vattenbalansavdelning) bucket-type model (the TUW (Technische Universität Wien) model). A calibration strategy based on the selection of the most suitable decade in the observation period for the parameterization of the model was applied. The model was first calibrated using observations, and then was driven by the precipitation and air temperatures projected by the KNMI (Koninklijk Nederlands Meteorologisch Instituut) and MPI (Max Planck Institute) regional climate models (RCM) under the A1B emission scenario. The model’s performance metrics and a visual inspection showed that the simulated runoff using downscaled inputs from both RCM models for the reference period represents the simulated hydrological regimes well. An evaluation of the future, which was performed by considering the representative climate change scenarios, indicated that changes in the long-term runoff’s seasonality and extremality could be expected in the future. In the winter months, the runoff should increase, and decrease in the summer months compared to the reference period. The maximum annual daily runoff could be more extreme for the later time horizons (according to the KNMI scenario for 2071–2100). The results from this study could be useful for policymakers and river basin authorities for the optimum planning and management of water resources under a changing climate.
Martin Kubáň, Juraj Parajka, Rui Tong, Isabella Pfeil, Mariette Vreugdenhil, Patrik Sleziak, Brziak Adam, Ján Szolgay, Silvia Kohnová, and Kamila Hlavčová
MDPI AG
The role of soil moisture is widely accepted as a significant factor in the mass and energy balance of catchments as a controller in surface and subsurface runoff generation. The paper examines the potential of a new dataset based on advanced scatterometer satellite remote sensing of soil moisture (ASCAT) for multiple objective calibrations of a dual-layer, conceptual, semi-distributed hydrological model. The surface and root zone soil moisture indexes based on ASCAT data were implemented into calibration of the hydrological model. Improvements not only in the instrument specifications, i.e., better temporal and spatial sampling, but also in the higher radiometric accuracy and retrieval algorithm, were applied. The analysis was performed in 209 catchments situated in different physiographic and climate zones of Austria for the period 2007–2018. We validated the model for two validation periods. The results show that multiple objective calibrations have a substantial positive effect on constraining the model parameters. The combined use of soil moisture and discharges in the calibration improved the soil moisture simulation in more than 73% of the catchments, except for the catchments with higher forest cover percentages. Improvements also occurred in the runoff model efficiency, in more than 27% of the catchments, mostly in the watersheds with a lower mean elevation and a higher proportion of farming land use, as well as in the Alpine catchments where the runoff is not significantly influenced by snowmelt and glacier runoff.
Adam Brziak, Martin Kubáň, Silvia Kohnová, and Ján Szolgay
Central Library of the Slovak Academy of Sciences
Péter Csáki, Kitti Gyimóthy, Péter Kalicz, Ján Szolgay, Katalin Anita Zagyvai-Kiss, and Zoltán Gribovszki
Walter de Gruyter GmbH
AbstractProviding information on the impacts of climate change on hydrological processes is becoming ever more critical. Modelling and evaluating the expected changes of the water resources over different spatial and time scales can be useful in several fields, e.g. agriculture, forestry and water management. Previously a Budyko-type spatially distributed long-term climate-runoff model was developed for Hungary. This research includes the validation of the model using historical precipitation and streamflow measurements for three nested sub-catchments of the Zala River Basin (Hungary), an essential runoff contributing region to Lake Balaton (the largest shallow lake in Central Europe). The differences between the calculated (from water balance) and the estimated (by the model) mean annual evapotranspiration varied between 0.4% and 3.6% in the validation periods in the sub-catchments examined. Predictions of the main components of the water balance (evapotranspiration and runoff) for the Zala Basin are also presented in this study using precipitation and temperature results of 12 regional climate model simulations (A1B scenario) as input data. According to the projections, the mean annual temperature will be higher from period to period (2011–2040, 2041–2070, 2071–2100), while the change of the annual precipitation sum is not significant. The mean annual evapotranspiration rate is expected to increase slightly during the 21st century, while for runoff a substantial decrease can be anticipated which may exceed 40% by 2071–2100 relative to the reference period (1981–2010). As a result of this predicted reduction, the runoff from the Zala Basin may not be enough to balance the increased evaporation rate of Lake Balaton, transforming it into a closed lake without outflow.
Ján Szolgay, Günter Blöschl, Zoltán Gribovszki, and Juraj Parajka
Walter de Gruyter GmbH
AbstractThe paper introduces the Special Section on the Hydrology of the Carpathians in this issue. It is the result of an initiative of the Department of Land and Water Resources Management of the Slovak University of Technology in Bratislava, the Institute of Hydraulic Engineering and Water Resources Management of the TU Vienna and the Institute of Geomatics and Civil Engineering of the University of Sopron to allow young hydrologists in the Carpathian Basin (and from outside) to present their research and re-network on the emerging topics of the hydrology of the Carpathians at the HydroCarpath Conferences since 2012.
Lenka Slavíková, Pavel Raška, Kazimierz Banasik, Marton Barta, Andras Kis, Silvia Kohnová, Piotr Matczak, and Ján Szolgay
Informa UK Limited
ABSTRACT Flood recovery is an important period in the flood risk management cycle. Recently, flood recovery has become viewed as an opportunity for future flood damage mitigation. Financial flows to cover flood damages and rules regarding their allocation are crucial for supporting or undermining mitigation efforts. In this paper, we map and compare state flood recovery funding in the so-called Visegrad Group Countries (V4), i.e. Czechia, Hungary, Poland and Slovakia, over the past 30 years of their democratic history. We apply a qualitative comparative approach to identify differences and similarities in risk sharing and state flood recovery funding approaches among these countries. Additionally, we reveal how risk sharing is addressed by existing flood recovery funding schemes. The results indicate that national governments have a low willingness to institutionalise ex-ante compensation schemes. Ad hoc instruments initiated shortly after disastrous flooding usually do not provide incentives to reduce future flood damages.
P. Sleziak, J. Szolgay, K. Hlavčová, M. Danko, and J. Parajka
Elsevier BV
Abstract In the current changing climate, the importance of temporal stability of hydrological models is increasing. The objective of this paper is to assess the effects of the changing weight of snow (wS) in a multiple objective calibration of a conceptual hydrological model in terms of the temporal stability of runoff and snow model efficiency and hydrologic model parameters. The methodology was tested by a lumped conceptual hydrological model (the TUW model), which was calibrated and validated in 213 Austrian catchments in two climatically different decades (i.e., 1981–1990 and 2001–2010). The results indicate that the runoff and snow model efficiencies are almost insensitive to a large range of wS, i.e., from 0 to 0.9 for the runoff and from 0.75 to 1.0 for the snow. This relationship is similar in the two different decades; however, the calibration runoff model efficiency (i.e., Nash-Sutcliffe efficiency) was about 5 to 10% greater in flatland catchments in the warmer decade (2001–2010). The main impact of wS on the snow model efficiency is the reduction of snow underestimation errors in the flatland catchments. The relative improvement of the snow simulations in the validation periods is greater in the flatland catchments and is in a range of 45–60% compared to 13% and 31% in the alpine catchments. The evaluation of the temporal stability indicates that increasing the weight of the snow increases the temporal stability of the degree-day factor and the parameters of the snowfall and rainfall thresholds. A change in the weight of the snow has the greatest impact on glacerized catchments, which were the most sensitive to changes in the mean annual air temperature between the two decades.
Adam Brziak, Martin Kubáň, Silvia Kohnová, and Ján Szolgay
Central Library of the Slovak Academy of Sciences
The accurate modelling of discharges in catchments plays an important role in solving a large variety of water management tasks. Three basic errors may affect the outputs modelled: the quality of the input data, uncertainities about the parameters, and the structure of the model. This paper is focused on a comparison of the performances of the lumped and semidistributed versions of the conceptual TUW rainfall-runoff model, which represents two different model structures. The comparison took place on 180 Austrian catchments, which have variable morphologies, altitudes, land uses, etc. We focused on the variability of the efficiencies and parameters of both types of HBV models, which were calibrated based on discharges in the period from 1991 to 2000. Whether the morphology and mean elevation of the catchment affect the calibration results was also take in account. Finally, we realized that the semi-distributed version of the TUW model gave better results as to the calibration efficiencies, when we calibrated the model for discharges; at the same time, the variations in the model parameters also gave better results in the semi-distributed version of the TUW model.
Günter Blöschl, Julia Hall, Alberto Viglione, Rui A. P. Perdigão, Juraj Parajka, Bruno Merz, David Lun, Berit Arheimer, Giuseppe T. Aronica, Ardian Bilibashi,et al.
Springer Science and Business Media LLC
Climate change has led to concerns about increasing river floods resulting from the greater water-holding capacity of a warmer atmosphere1. These concerns are reinforced by evidence of increasing economic losses associated with flooding in many parts of the world, including Europe2. Any changes in river floods would have lasting implications for the design of flood protection measures and flood risk zoning. However, existing studies have been unable to identify a consistent continental-scale climatic-change signal in flood discharge observations in Europe3, because of the limited spatial coverage and number of hydrometric stations. Here we demonstrate clear regional patterns of both increases and decreases in observed river flood discharges in the past five decades in Europe, which are manifestations of a changing climate. Our results—arising from the most complete database of European flooding so far—suggest that: increasing autumn and winter rainfall has resulted in increasing floods in northwestern Europe; decreasing precipitation and increasing evaporation have led to decreasing floods in medium and large catchments in southern Europe; and decreasing snow cover and snowmelt, resulting from warmer temperatures, have led to decreasing floods in eastern Europe. Regional flood discharge trends in Europe range from an increase of about 11 per cent per decade to a decrease of 23 per cent. Notwithstanding the spatial and temporal heterogeneity of the observational record, the flood changes identified here are broadly consistent with climate model projections for the next century4,5, suggesting that climate-driven changes are already happening and supporting calls for the consideration of climate change in flood risk management.Analysis of a comprehensive European flood dataset reveals regional changes in river flood discharges in the past five decades that are consistent with models suggesting that climate-driven changes are already happening.
Günter Blöschl, Marc F.P. Bierkens, Antonio Chambel, Christophe Cudennec, Georgia Destouni, Aldo Fiori, James W. Kirchner, Jeffrey J. McDonnell, Hubert H.G. Savenije, Murugesu Sivapalan,et al.
Informa UK Limited
ABSTRACT This paper is the outcome of a community initiative to identify major unsolved scientific problems in hydrology motivated by a need for stronger harmonisation of research efforts. The procedure involved a public consultation through online media, followed by two workshops through which a large number of potential science questions were collated, prioritised, and synthesised. In spite of the diversity of the participants (230 scientists in total), the process revealed much about community priorities and the state of our science: a preference for continuity in research questions rather than radical departures or redirections from past and current work. Questions remain focused on the process-based understanding of hydrological variability and causality at all space and time scales. Increased attention to environmental change drives a new emphasis on understanding how change propagates across interfaces within the hydrological system and across disciplinary boundaries. In particular, the expansion of the human footprint raises a new set of questions related to human interactions with nature and water cycle feedbacks in the context of complex water management problems. We hope that this reflection and synthesis of the 23 unsolved problems in hydrology will help guide research efforts for some years to come.
Peter Rončák, Kamila Hlavčová, Silvia Kohnová, and Ján Szolgay
Springer International Publishing
In this study the authors looked at the impact of climate change on a hydrological regime and catchment runoff in selected catchments of Slovakia. Changed climate conditions, which are characterized in particular by changes in precipitation, air temperature, and potential evapotranspiration in future decades, have been predicted according to the outputs of the KNMI and MPI regional climate change models and the A1B emission scenario. Assuming these scenarios, the hydrological regime characteristics were simulated by a distributed WetSpa rainfall-runoff model parameterized for five selected river basins in a daily step by the year 2100. When compared to the current state, changes in the total runoff and its components, as well as changes in the soil moisture and the actual evapotranspiration, confirm the assumption of an increase in extremes of the runoff regime in the winter period and a decrease during the summer and autumn periods, causing possible droughts. The results of the study indicate a need for re-evaluation of the water demands and the future design of water management structures in Slovakia.
K. Hlavčová, M. Danáčová, S. Kohnová, J. Szolgay, P. Valent, and R. Výleta
Elsevier BV
Abstract The paper focuses on the generation of floods as a principal soil threat and on soil erosion as an additional soil threat on arable lands of hillslope areas. As the most important component of floods causing the degradation of soils on arable lands, surface runoff is analysed in this study. The protective effect of crop management on the generation of surface runoff and sediment transport on arable lands is estimated on a plot and slope scale. The site of the case study, which is located in the Myjava river basin in western Slovakia, is a hilly agricultural field with an area of 29 ha; it is characterised by arable soil, extreme erosion processes, and muddy floods. Field rainfall simulation experiments were combined with physically-based modelling for studying the formation of surface runoff under various soil covers. The field experiments consisted of simulating runoff generation from artificial rainfalls using the Eijkelkamp rainfall simulator on experimental plots with a focus on estimating the volume of surface runoff, the mass of sediments transported by the surface runoff, and the time to runoff. The volumes of the surface runoff and the values of the time to runoff have been applied in the parameterisation of the SMODERP physically-based hydrological model. The hydrological modelling of the surface runoff on the selected slope profile quantified the protective effect of various soil covers on reducing surface runoff. The outcome of the modelling was the maximum allowed lengths of the slope that represent the crucial values for flood and erosion control. When exceeding these critical values, protective measures, e.g., vegetation strips, should be proposed.
Silvia Kohnová, Marianna Vasilaki, Martin Hanel, Ján Szolgay, Kamila Hlavčová, Athanasios Loukas, and Gabriel Földes
Central Library of the Slovak Academy of Sciences
Abstract This paper analyses projected changes in short-term rainfall events during the warm season (April – October) in an ensemble of 30 regional climate model (RCM) simulations. The analysis of trend changes and changes in scaling exponents was done for the Hurbanovo, Bratislava, Oravská Lesná, and Myjava stations in Slovakia. The characteristics of maximum rainfall events were analysed for two scenario periods, one past and one future (1960–2000 and 2070–2100) and compared to the characteristics of the actual observed events. The main findings from the analysis show that 60-min short-term events for most of the RCM simulations will either increase or remain constant. On the other hand, the depths and intensities of daily events are projected to increase significantly; in some cases they were found to be ten times larger. Trends in future events at the Hurbanovo station were found to be insignificant. In the other stations positive trends in future rainfall events prevail, except for daily rainfall at the Myjava station, which shows a negative trend. Using results from the selected simulations, the scaling exponents estimated are on average lower than the exponents of the data observed. On the other hand, due to the higher daily precipitation amounts in the future seen to all the scenarios, the downscaled values of short-term rainfall at all the stations analysed might be considerably higher in the future horizons, which could subsequently affect future design rainfall values for engineering designs.
Patrik Sleziak, Ján Szolgay, Kamila Hlavčová, Doris Duethmann, Juraj Parajka, and Michal Danko
Walter de Gruyter GmbH
Abstract In many Austrian catchments in recent decades an increase in the mean annual air temperature and precipitation has been observed, but only a small change in the mean annual runoff. The main objective of this paper is (1) to analyze alterations in the performance of a conceptual hydrological model when applied in changing climate conditions and (2) to assess the factors and model parameters that control these changes. A conceptual rainfall-runoff model (the TUW model) was calibrated and validated in 213 Austrian basins from 1981–2010. The changes in the runoff model’s efficiency have been compared with changes in the mean annual precipitation and air temperature and stratified for basins with dominant snowmelt and soil moisture processes. The results indicate that while the model’s efficiency in the calibration period has not changed over the decades, the values of the model’s parameters and hence the model’s performance (i.e., the volume error and the runoff model’s efficiency) in the validation period have changed. The changes in the model’s performance are greater in basins with a dominant soil moisture regime. For these basins, the average volume error which was not used in calibration has increased from 0% (in the calibration periods 1981–1990 or 2001–2010) to 9% (validation period 2001–2010) or –8% (validation period 1981–1990), respectively. In the snow-dominated basins, the model tends to slightly underestimate runoff volumes during its calibration (average volume error = –4%), but the changes in the validation periods are very small (i.e., the changes in the volume error are typically less than 1–2%). The model calibrated in a colder decade (e.g., 1981–1990) tends to overestimate the runoff in a warmer and wetter decade (e.g., 2001–2010), particularly in flatland basins. The opposite case (i.e., the use of parameters calibrated in a warmer decade for a colder, drier decade) indicates a tendency to underestimate runoff. A multidimensional analysis by regression trees showed that the change in the simulated runoff volume is clearly related to the change in precipitation, but the relationship is not linear in flatland basins. The main controlling factor of changes in simulated runoff volumes is the magnitude of the change in precipitation for both groups of basins. For basins with a dominant snowmelt runoff regime, the controlling factors are also the wetness of the basins and the mean annual precipitation. For basins with a soil moisture regime, landcover (forest) plays an important role.
Peter Roncak
Stef92 Technology