Günter Blöschl’s research while affiliated with Federal Agency for Water Management Austria and other places

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Publications (371)


Figure 4: Relationship between (a) peak sediment load (kg/5 min) and total event sediment load (kg) at site E2, (b) peak flow 297
Figure 5: The map illustrates the division of the HOAL catchment into four distinct categories based on topographical and 348
Figure 8: Spearman correlation matrix for overland flow measurements, showing the relationships between rainfall intensity 471
Figure 9: Spearman correlation matrix for in-stream measurements, showing the relationships between rainfall intensity (EI₃₀), 499
Figure 10: The images at the top (a, b) illustrate how overland flow and sediment erosion originate from erosive areas of the 569

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Identification of erosion hotspots and scale-dependent runoff controls on sediment transport in an agricultural catchment
  • Preprint
  • File available

June 2025

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4 Reads

Christopher Thoma

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Borbala Szeles

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Miriam Bertola

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[...]

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Günter Blöschl

Understanding how agricultural land management influences sediment transport is crucial for identifying critical source areas (CSAs) and improving erosion mitigation strategies. While numerous studies focus on in-stream sediment concentrations, fewer investigate overland flow on the hillslopes. We monitored streamflow and sediment fluxes at an overland flow station (E2) and an in-stream station (MW) across 55 runoff events (2011–2022) in the Hydrological Open Air Laboratory (HOAL), Austria. The catchment was segmented into four distinct areas (A, B, GW9, C) based on topography, hydrological connectivity, and proximity to the stream, allowing a spatially explicit assessment of erosion hotspots. Temporal patterns of sediment transport were analysed to infer spatial variability, and differences in sediment transport dynamics among areas were quantified using Kruskal-Wallis tests and effect size analysis. Results suggest that at E2 (hillslope scale), non-erosive cultivation significantly reduced peak turbidity (~9.5 times) and sediment load (~3.8 times) in flat agricultural areas (7.2 % slope, <500 m from the stream) but had no measurable effect in steep (10–12 % slope) or distant (>1000 m) agricultural areas. Across all field types, conversion to non-erosive cultivation did not affect peak flow. At MW (catchment scale), compared to E2, peak turbidity at MW decreased (~5.4–7.7 times) due to dilution from subsurface flow contributions, while peak flow increased (~2.8–11 times) due to additional inputs from wetlands, springs, and subsurface flows. Sediment load at MW was ~2.4–5.4 times higher than at E2, likely due to unmonitored diffuse overland flow and sediment inputs from tile drainages. Our findings indicate that non-erosive cultivation alone in steep terrains or distant agricultural areas is insufficient to effectively mitigate sediment transport. Effective sediment management in agricultural catchments requires spatially targeted erosion control strategies that account for topography, hydrological connectivity, and field proximity to streams.

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Hydro‐Meteorological Drivers of Event Runoff Characteristics Under Analogous Soil Moisture Patterns in Three Small‐Scale Headwater Catchments

June 2025

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36 Reads

Hydrological Processes

A catchment's runoff response to precipitation largely depends on the antecedent soil moisture and on the characteristics of the precipitation event, but also on other hydro‐meteorological conditions, such as evapotranspiration. Studies investigating the effects of hydro‐meteorological variables on runoff characteristics in catchments with daily temporal resolution mostly used surrogate measures of soil moisture derived from hydrological models or remote sensing products. Here, we applied a time series‐based pattern search to up to 12 years of daily in situ measured soil moisture in three depths (5, 20 and 50 cm) in three headwater catchments, two of which are located in Germany (forest and grassland) and one in Austria (agriculture), to identify key variables influencing runoff characteristics under analogous soil moisture patterns. After detecting groups of analogous soil moisture, we split the corresponding runoff into similar and different patterns based on goodness‐of‐fit criteria and analysed their influencing hydro‐meteorological variables with descriptive statistics and Spearman rank correlation coefficients ( ρ ). Results showed that in the forest and in the grassland catchment, the antecedent soil moisture mainly influenced runoff characteristics for analogous soil moisture patterns. In the agricultural catchment in Austria, both the antecedent soil moisture and rainfall characteristics had an influence on runoff characteristics. The proposed method can be used to evaluate hydro‐meteorological drivers of event runoff characteristics under analogous soil moisture. In this way, hydrological processes that dominate in either group of similar or different runoff patterns can be differentiated, providing insights into the potential predictability of the respective runoff pattern.



Upscaling colloidal transport from the column to the field: The value of a large gravel column experiment as an intermediate step

May 2025

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40 Reads

Hydrogeology Journal

Due to public health or environmental concerns, examining the effects of preferential flow processes on the transport of pathogenic microorganisms or contaminants of emerging concern must be studied in the laboratory. However, the resulting transport parameters cannot be directly applied to field-scale groundwater models. This research explores how an upscaling relationship, with removal as a function of distance, can be found using B. subtilis spores and microspheres as colloidal trac-ers in saturated flow-through experiments at three different scales. The study investigates transport processes in a 4-m-tall undisturbed gravel column and compares the results with previously published data. Results showed that colloidal removal (log-removal, attachment rate/efficiency) in heterogeneous porous media follows a power law as a function of travel distance, rather than an exponential relationship, which is normally assumed in removal equations. It was found that by using a power function, it was possible to decrease the difference between the attachment coefficients so that the meso-scale value was closer to the small-scale value. To the contrary, using a dual permeability model increased the difference between attachment rates at these two scales. Groundwater transport modeling may benefit from taking this power law relationship into account, instead of using a constant first-order removal rate, as most tracer tests are performed at a smaller scale than the scale that is being modeled. The meso-scale column provides insights into upscaling processes by incorporating an intermediate step when comparing groundwater transport at the column scale to the field scale.


How changes in future precipitation impact flood frequencies: a quantile-quantile mapping approach

Flood risk management institutions and practitioners need accurate and easy-to-use approaches that incorporate the changing climate conditions into flood predictions in ungauged basins. The present work aims at developing an operative procedure to include the expected variation in precipitation extremes in flood frequency analysis. We relate Flood Frequency Curves and Intensity-Duration-Frequency curves through quantile-quantile relationships. Assuming that the percentage variations of precipitation and flood quantiles are linked by the quantile-quantile relationship, we obtain modified Flood Frequency Curves accounting for the projected changes in precipitation extremes. The methodology is validated in a virtual world based on the Rational Formula approach where flood events are the result of the combination of two jointly distributed random variables: extreme precipitation and peak runoff coefficient. The proposed methodology is found to be reliable in basins where flood changes are dominated by precipitation changes rather than variations in the runoff generation process. To illustrate its practical usefulness, the procedure is applied to 227 catchments within the Po River basin in Italy using projected percentage changes of precipitation extremes from CMIP5 CORDEX simulations for the end of the century (2071-2100). With projected changes in 100-year precipitation ranging from 5 to 50\%, the corresponding variations in 100-year flood magnitudes are expected to span a broader range (10 to 90\%), reflecting substantial heterogeneity in catchment responses to rainfall changes. Powered by TCPDF (www.tcpdf.org)


Figure 1. Trends in prokaryotic cell concentration (Total Cell Counts; TCC) (A), bulk bacterial secondary production (BSP) (B), and daily cell division rates (CDd) (C) along the Danube River from upstream (left; rkm 2600) to the river mouth (right; rkm 0). Regression statistics are shown in Table 2. (Data for JDS2 was taken from 20 ). n(JDS2) = 75, n(JDS3) = 54
Figure 2. The gradual development of alpha and beta diversity with increasing cumulative travel time (ttcum) during JDS3 (total community; violet; n = 54) and for the two separated size fractions studied during JDS2, representing the bacterioplankton communities of 0.2-3.0 µm (light blue; n = 39) and >3.0 µm (dark blue, n = 47) -corresponding to freeliving and particle-associated bacterioplankton, respectively. Panel (A) depicts the development of alpha diversity (ACE richness), (B) the dynamics of phylotype turnover (phylotype replacement) component of beta diversity between two consecutive sites given as Simpson dissimilarity, and (C) the pairwise phylotype turnover component among all sites. The colored lines represent fitted linear models for the respective datasets. Regression statistics are shown in Table 1. JDS2-
Figure 3. Changes in the abundance of selected phylotypes during their travel time along the Danube River. The lines show the fitted generalized additive models (R package mgcv), the ribbon marks their Bayesian credible interval (similar to confidence interval). JDS2-FL: free-living fraction, JDS2; JDS2-PA: particle-associated fraction, JDS2.
Summary table of linear models relating bacterial parameters to travel distance or travel time for both surveys. The probability of an error by rejecting the null hypothesis of no change over distance/time is < 0.05 in all models listed, except for the 'Simpson diversity (between consecutive sites)' model for JDS3 where it is >0.05.
Bacterial diversity turnover estimates in a continental river system

April 2025

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34 Reads

Understanding bacterial dynamics in large river systems is crucial for predicting continental-scale ecological functioning under anthropogenic pressures. Here, two consecutive surveys 6-years apart along the 2600 km Danube River found that carbon incorporation per cell and hour decreased by 5000 atoms every kilometer and that cells multiplied five times during their travel down the entire river. Resolving these cell turnovers taxonomically revealed taxa with a hundredfold difference from these average numbers. Bacterial community turnover was due to replacement (phylotype turnover) and could be linked to species sorting. This was despite an overall decrease in diversity richness downstream. Using linear models, we were able to relate carbon, cell, phylotype and diversity turnover rates to water residence time and discharge with outliers associated with human impacts. As such the reproduceable macroecological models predict microbial changes from anthropogenic and climate alterations along a continental drainage system providing insights into their ecological consequences.


Flood frequency analysis: selection of distribution functions for modeling extreme floods on mountain rivers

April 2025

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29 Reads

The most catastrophic floods in Ukraine occur in mountainous regions, where forecasting them based on existing global climate and hydrological models is ineffective. One of the alternative methods of Flood frequency analysis is the selection and use of the most suitable theoretical distributions for further modeling of extreme water flows, the so-called Peaks Above Threshold (РОТ). The research was carried out on the example of the Opir River (Carpathian Mountains, Ukraine) based on daily observations of water flow over a multi-year period (1961-2020). 10 theoretical distributions were examined using the Chi-square, Kolmogorov-Smirnov, Anderson-Darling criteria. The GEV distribution gave best goodness-of-fit values than other distributions. Based on the GEV distribution function, a statistical model was constructed, the parameters of which were estimated using the Monte Carlo method. The resulting model was used to simulate extreme floods on the Opir River. Two simulation procedures were performed using the Monte Carlo method to generate random data from the best fitting distributions while ignoring the correlations between variables and the Iman Conover method to generate random data from the best fitting distributions while preserving the rank correlation structure. An analysis of the obtained models shows that in the range of percentiles 0-60%, the model built using the Iman Conover methods demonstrates the best agreement of the simulated POT values. In the range of percentiles 60-80%, the model built by the Monte Carlo method demonstrates the best coincidence.


Panta Rhei: a decade of progress in research on change in hydrology and society

April 2025

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920 Reads


A Scale‐Adaptive Urban Hydrologic Framework: Incorporating Network‐Level Storm Drainage Pipes Representation

March 2025

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191 Reads

Below‐ground urban stormwater networks (BUSNs) significantly influence urban flood dynamics, yet their representation at the watershed or larger scales remains challenging. We introduce a scalable urban hydrologic framework that centers on a novel network‐level BUSN representation, balancing the needs for physical basis, parameter parsimony, and computational efficiency. Our framework conceptualizes an urban watershed into four interacting zones: hillslopes (natural), storm‐sewersheds (urban), a sub‐network channel (tributaries), and a main channel. We develop an innovative Graph Theory‐based algorithm to derive network‐level BUSN parameters from publicly available datasets, enabling efficient, scalable parameterization. We demonstrate this framework's applicability at nine representative watersheds in the Houston metropolitan region, USA, with urban imperviousness ranging from 0% to 64% and drainage areas ranging from 24 to 302 km2 km2{\text{km}}^{2}. Our model achieves satisfying computational efficiency, completing hourly time step simulations for 18 years in less than 5 sec per watershed on a standard PC. Validation against observed daily streamflow confirms that the model can capture small‐to‐large flood peaks and seasonal and annual water balance over these watersheds. Comparisons with the National Water Model show better performance in predicting flood peaks and overall water balance, underscoring the promises of our new framework for urban hydrologic modeling at large scales. Furthermore, analysis reveals nonlinear relationships between BUSNs' designed capacities and flood reduction effects. Our approach bridges the gap between detailed hydraulic and large‐scale hydrologic models, providing a valuable tool for urban flood prediction and management across broader spatial and temporal scales.


Heavy rainfall evolution in Austria
a, Daily heavy rainfall (99th percentiles of wet days) anomalies for the reference period 1981–2010 calculated from the GSA (green) and HYD (purple) datasets. Solid lines indicate the mean over all stations, shaded bands the 95% confidence interval of the mean estimated by bootstrapping (n = 1,000). The confidence intervals of the GSA data are wider because of the smaller number of stations. b, Hourly heavy rainfall (99th percentiles of wet hours) anomalies, otherwise similar to a. Insets, histograms of the 99th percentiles over all stations for 1981–2010. c, Daily heavy rainfall anomalies for north (green) and south (purple) of the Alpine ridge. d, Hourly heavy rainfall anomalies, otherwise similar to c. The grey bars at the bottom of each panel indicate the reference period.
Attribution of heavy rainfall evolution in Austria
a, Daily heavy rainfall anomalies (both datasets) for the north and the meridionality index. b, Daily heavy rainfall anomalies (both datasets) for the south and the persistency index. c, Hourly heavy rainfall anomalies (both datasets) and air temperature anomalies over the entire domain. d, Instantaneous scaling: hourly heavy rainfall rates above the 99th percentile binned by daily air temperature of the day of occurrence for each month of the warm season. Grey dashed lines indicate scaling of +7% °C⁻¹. A quantile regression of (log-)hourly heavy rainfall against daily air temperature for 1950–2023 gives an instantaneous scaling across all months of 6.8 ± 0.1% °C⁻¹. e, Climate scaling: comparison of the periods 1950–1970 and 2003–2023. The average hourly heavy rainfall anomaly increases by +14.7% and the air temperature anomaly by +1.8 °C, which gives a climate scaling of 8.1 ± 1.2% °C⁻¹. The grey bars at the bottom of a–c indicate the reference period. The shaded bands in a–d indicate the 95% confidence interval of the mean, estimated by bootstrapping (n = 1,000). The lower and upper box boundaries in e are the 25th and 75th percentiles, respectively; the line inside the box is the mean; the upper and lower whiskers extend to the largest value, but no further than 1.5 times the interquartile range, and the points outside the whiskers are individual data points.
Effect of heavy rainfall evolution on flood peaks
a, Daily heavy rainfall anomalies and flood peak discharge anomalies for large catchments (greater than 500 km²), north (left) and south (right) of the Alpine ridge. b, Hourly heavy rainfall anomalies and flood peak discharge anomalies for small catchments (less than 50 km²), north (left) and south (right) of the Alpine ridge. Heavy rainfall values are 99th percentiles, as in Fig. 1, and flood peaks are the mean annual floods of the warm season. The grey bars at the bottom of the panels indicate the reference period. Solid lines indicate the mean over all stations, the shaded bands the 95% confidence interval of the mean, estimated by bootstrapping (n = 1,000). A remarkable similarity can be seen between the daily heavy rainfall and floods in large catchments and between the hourly heavy rainfall and floods in small catchments, which is related to the travel times of water within the catchments.
Increasing hourly heavy rainfall in Austria reflected in flood changes

March 2025

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280 Reads

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4 Citations

Nature

Climate change is expected to increase heavy rainfall with concomitant increases in flooding¹. Causes of increased heavy rainfall include the higher water-holding capacity of a warmer atmosphere and changes in atmospheric circulation patterns², which may translate into future heavy rainfall increases in most of Europe³. However, gathering evidence on the time evolution of past changes has been hampered by data limitations and measurement uncertainties, in particular for short rainfall durations, such as 1 h. Here we show an 8% increase in daily and 15% increase in hourly heavy rainfall over the last four decades by analysing a new dataset comprising 883 stations in Austria from 1900 to 2023. These increases are fully consistent between two independent networks and occurred after a retarding phase between 1960 and 1980. Hourly heavy rainfall changes are aligned with temperature increases with the sensitivity of a 7% increase per 1 °C of warming, in line with Clausius–Clapeyron scaling. Daily heavy rainfall changes, however, are aligned with atmospheric circulation indices with little correlation to air temperature, which suggests a bigger role of atmospheric circulation modes than previously thought. The daily heavy rainfall changes are remarkably consistent with observed flood increases of about 8% in large catchments. The hourly heavy rainfall changes are similarly consistent with flood changes in small catchments, although the flood increase is stronger (25% over the last four decades). Climate adaptation measures in flood management may therefore be more pressing for rivers draining smaller catchment areas than for large rivers.


Citations (73)


... However, there is widespread interest in the influence of climate variability and change on the intensity of rainfall, particularly in short-duration rainfall events and over short periods within longer events. Variations of short-term intensity have been linked to temperature changes and increased atmospheric water-holding capacity (Chen et al., 2013, Chiappa et al., 2024, Fu and Wu 2024, and Haslinger et al., 2025). Some studies have suggested that short-term (sub-daily or sub-hourly) intensities have increased, and are increasing at a more rapid rate, than those for longer-duration rainfalls, such as daily totals (Tamm et al., 2023) [8]. ...

Reference:

Uncertainty of Tipping-Bucket Data May Hamper Detection and Analysis of Secular Changes in Short-Term Rainfall Rates
Increasing hourly heavy rainfall in Austria reflected in flood changes

Nature

... SFINCS is a reduced-complexity model designed to simulate flooding from multiple drivers, such as 260 storm surge, river discharge, and precipitation (Leijnse et al., 2021). It offers a simplified yet robust approach to modeling The lack of observed flood data to validate and calibrate flood models is a common challenge (see e.g., Merz et al., 2024;Molinari et al., 2019). For this case study, we search for historical flood information from several different sources, including high-water marks from USGS (United States Geological Survey), satellite images, the NOAA storm event dataset, FEMA Flood Risk Map, local news, and crowd-sourced platforms such as social media and citizen science platforms. ...

Invited perspectives: safeguarding the usability and credibility of flood hazard and risk assessments

... Performance indexes are also used to provide a non-dimensional measure of the agreement of the two models against the reference scenario, and a value of 1 indicates a perfect match between the model and the reference (Table 2). A first performance index, P 1 , is the so-called Hit Rate (Blöschl et al., 2024;Sampson et al., 2015), which provides a nondimensional measure of the correctly predicted flooded area, and is defined as: ...

Hyper-resolution flood hazard mapping at the national scale

... Still, similar shapes of the runoff response at the catchment's outlet were also influenced by the temporal precipitation pattern (Hövel et al. 2024a). The potentially dominant control of rainfall characteristics on the runoff response in the agricultural catchment is further supported by Szeles et al. (2024), who found a high contribution of new water (~50%) during peak flows, suggesting a rapid contribution of precipitation to the stream via surface runoff. Surface runoff in the catchment may occur for various reasons, with agricultural land use and soil compaction being one of the major influencing factors (Szeles et al. 2024). ...

Comparison of two isotopic hydrograph separation methods in the Hydrological Open Air Laboratory , Austria

Hydrological Processes

... Given these distinctive features of ship pollution, it is critical to pay attention to inland ship water pollution. Although some studies have proposed methods for calculating inland vessel pollution , Steinbacher et al 2024, there is a lack of research evaluating pollution control policies for inland vessels. As the Yangtze River is the world's busiest river in terms of shipping volume, the issue of ship-induced water pollution cannot be overlooked. ...

Assessing the impact of inland navigation on the faecal pollution status of large rivers: A novel integrated field approach
  • Citing Article
  • July 2024

Water Research

... ( http://creativecommons.org/licenses/by-nc-nd/4.0/ ). become a reality [4]. Moreover, in small catchments of southern Europe, floods have increased [5], essentially due to this increment in the frequency and intensity of short time precipitation events [6]. ...

HESS Opinions: The sword of Damocles of the impossible flood

... Furthermore, global forest loss is visualized (Vizzuality, 2022) or the habitats of selected species are presented geographically (The IUCN Red List of Threatened Species, 2022b;Global Biodiversity Information Facility, 2022;Janicki et al., 2016;Telenius, 2011). In addition, Annanias et al. (2022) and Rauer-Zechmeister et al. (2024) have shown how human impacts have reshaped land and in return how climate change is affecting humans in the form of floods. Next to heat maps, Gixhari et al. (2014) designed various glyph-based maps to communicate diverse aspects of fruit tree species distributions in Albania. ...

HORA 3D: Personalized Flood Risk Visualization as an Interactive Web Service

... Validation and calibration of flood models is a difficult task due to the common lack of observed flood data worldwide (Merz et al., 2024a;Molinari et al., 2019a). This is especially true for under-resourced regions; but the lack of observed flood data is also an issue in developed countries and more noticeable in the case of pluvial flood events, which are the most frequent in our study area of Gloucester City (Hino and Nance, 2021). ...

Invited perspectives: Safeguarding the usability and credibility of flood hazard and risk assessments

... On this account, concepts that promote working with nature rather than against it, like nature-based solutions (NbS), are increasingly being prioritised in policy and practice to reverse urbanisation's negative impacts on ecosystems and advance climate adaptation [15,102,124]. NbS are defined as solutions that are inspired and supported by nature, which are cost-effective, simultaneously provide environmental, social and economic benefits and help build resilience [46,95]. For mitigating flood risk hazards, the restoration of wetlands in river catchments and floodplain restoration is considered as NbS that can effectively restore natural hydrological cycles for regulating runoff [116], enhance environmental quality and biodiversity [88], offer more cost-effective and sustainable outcomes [90], improve urban resilience to climate change and provide significant social and economic co-benefits [125]. ...

The IAHS Science for Solutions decade, with Hydrology Engaging Local People IN one Global world (HELPING)

... We used recent streamflow data, the same method used by Wasko et al. (2020), and a spatial interpolation method to construct a CONUS-scale LWY timeframe. In addition, given that the most appropriate definition of water year varies depending on research purposes, we applied the same process and generated a second LWY timeframe starting from the month with the highest average monthly streamflow, an approach often used in studies of low streamflow and hydrological drought (e.g., Caruso 2000;Chagas et al. 2024). To create these LWYs, we used subregions that were created based on the drainage features by the USGS (Seaber et al. 2007). ...

Regional Low Flow Hydrology: Model Development and Evaluation