Federal Agency for Water Management Austria

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 ${\text{km}}^{2}$. 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.

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.

Purpose The present study evaluates the sediment mass and storage of total organic carbon (TOC), total nitrogen (TN) and total phosphorus (TP) in a managed agricultural pond, representative for ponds situated in Central Europe. The study is designed to enhance understanding of the functioning of such ponds as nutrient sinks and the capacity to retain TOC, TN and TP within the pond's sediment layer. Methods In order to assess the distribution of sediments and the storage of nutrients, orthomosaics and digital elevation models (DEMs) were generated from imagery recorded by unmanned aerial vehicles (UAVs) in 2021 and 2022. The thickness of the sediment was measured at 174 points over nine diving campaigns, with the volume estimated comparing three interpolation methods. Sediment core samples were analysed to determine their physical and chemical composition. In addition, water samples were collected from the inlets and outlets to trace potential pathways of nutrients. Results The pond was found to store 330.9 t ha⁻¹ TOC, 16 t ha⁻¹ TN and 0.8 t ha⁻¹ TP with an sediment mass of 1,460 t ha⁻¹. The DEM comparison indicates areas of sediment loss and accumulation, with the overall sediment mass remaining stable. The vertical distribution of nutrients indicated the presence of layered sediment deposition, which suggests a complex history of sediment and nutrient retention. Conclusion The pond acts as a nutrient sink, but sediment and nutrients can be temporarily resuspended and lost to receiving waters during fish harvest. Further research should explore sediment connectivity and nutrient pathways into ponds in agricultural landscapes.

Hydrological processes of mountainous watersheds commonly impact water resource supply in downstream areas. To better understand how re‐vegetation affects the different hydrological pathways of watersheds, we investigated their change at various temporal scales for the Xiaoluan River watershed, a typical meso‐scale watershed featuring a plateau–mountain transition topography in northern China. For the non‐growing season from 2006 to 2020, the groundwater discharge of the watershed and the wetting of the watershed in terms of the Horton Index significantly increased, and the recession process in terms of the recession coefficient ( k ) was considerably prolonged. We suggest that re‐vegetation and snowmelt were responsible for this change, but they affected the hydrological processes differently. That is, re‐vegetation might improve the water storage capacity of the shallow soil layers of the watershed, thereby enhancing the capacity of groundwater recharge and discharge. Meanwhile, snowmelt may provide available water for recharging and discharging the watershed. Because reforestation progresses and global climate change continues, more complex hydrological processes are to be expected. Therefore, continuous monitoring and detailed investigations of subsurface hydrological processes will be necessary for adaptive watershed management.

Springs provide critical water resources that are sensitive to changing climate and catchment processes. In many regions, understanding the temporal variability and spatial distribution of spring discharge is therefore crucial for sustainable water management. Knowledge of these discharge characteristics, organised in a coherent framework, is essential for protecting spring water and preventing shortages. To establish such a framework, we conducted a comparative analysis of long-term discharge records from 96 springs across Austria. Based on discharge seasonality and autocorrelation, we derived a broad-scale classification through cluster analysis and explored associations between individual clusters. The identified similarities in discharge patterns were grouped into four distinct spring categories, each demonstrating common behaviour. To determine the main factors influencing discharge across these four groups, we compared their spatial and temporal patterns with regional climate and catchment characteristics. They align with physical drivers of spring discharge, including precipitation frequency and intensity, snow cover duration, and dominant aquifer type. As these factors were not included in the classification procedure, their alignment supports the validity of our statistical approach. We conclude that the quantitative information derived from this analysis provides a valuable complement to traditional spring classification schemes, which are often based on qualitative knowledge. Our proposed strategy refines these classification approaches, enhances objectivity and reproducibility, and promotes conformity across hydrological disciplines.

Urmia Lake (UL), one of the most important saline ecosystems in the world, has faced a severe water level drop in the last two decades. In this research, the seasonality of precipitation in the Urmia Lake basin (ULB) was analyzed using the daily precipitation data of 30 rain-gauge stations in the period 1991–2018. The occurrence time of extreme precipitation (OTEP) was determined by using circular statistics. The uniformity of OTEP was examined by Rayleigh test (RT) and Kuiper test (KT). The slope of the trend lines for the OTEP was estimated using the modified Sen’s estimator. Trends in the OTEP were analyzed by the non-parametric Mann–Kendall test. The results indicated no uniformity in the OTEP at 0.1, 0.05, and 0.01 levels in the basin. Seasonal events throughout the year were divided into two separate seasons denoted by S1 for late winter and early spring and S2 for autumn. The results showed that the mean seasonality increased from 0.3 to 0.82 (for S1) and 0.9 for S2. The comparison of seasonal strength in the west and east parts of ULB revealed that these two parts of ULB had the same seasonality strength (SS) in the S1. However, the seasonality of the western part of the lake was stronger than the eastern part in S2. Trends in OTEP showed that about 60% of the stations witnessed upward trends in S1. This was about 27% in S2. The findings of this analysis can provide useful information about the changes in the OTEP and its hydrological impact on the studied basin. This information is helpful in the scientific management of water resources in the Urmia Lake basin.

Plain Language Summary Seafloor avalanches of sediment, called turbidity currents, transport huge volumes of sediment and organic carbon to the deep‐sea, and they break critical seabed telecommunication cables that underpin global data transfer. However, turbidity currents are very difficult to measure directly as they often damage sensors placed in their flow path, so they are poorly understood. Here we show that turbidity currents generate ground vibrations that can be measured using ocean‐bottom seismographs placed outside the flow's destructive path, revolutionizing flow monitoring. These seismographs recorded the longest sediment flows yet measured in action on Earth, which traveled >1,000 km along the submarine Congo Canyon‐Channel offshore West Africa. We use these observations to test fundamental models of turbidity current flow behavior. Our measurements show that the front of the flows contain a fast frontal‐zone with high sediment concentrations, which can be up to ∼400 km long, whilst the whole duration of the flow can last for more than 3 weeks. These frontal‐zones develop near‐uniform durations and speeds, despite extensive seabed erosion that adds sediment into the flow. New information on flow durations shows how turbidity currents rapidly deliver prodigious volumes of organic carbon, sediment, and warm water to the deep‐ocean floor.

In this study a network of three eddy covariance stations rotated between five measurement sites is used to measure evaporation (E) within the Hydrological Open Air Laboratory (HOAL) in Petzenkirchen, Austria for 8 years. Discharge measurements at the tributaries and outlet of the main catchment allow for E to be estimated for 6 subcatchments using the water balance method. Year to year variability in monthly E measured by the eddy covariance stations is found to be driven primarily by net radiation and temperature and annual E by net radiation. Year to year variability in the water balance-based E estimate was driven by precipitation. The two methods are found to be consistent, when storage and leakage are accounted for. Daily and seasonal patterns can be seen resulting from the agricultural land use cycle, due to the variations in land cover during the growing season.

Correction for ‘Exploring the variability of PFAS in urban sewage: a comparison of emissions in commercial versus municipal urban areas’ by N. Krlovic et al. , Environ. Sci.: Processes Impacts , 2024, 26 , 1868–1878, https://doi.org/10.1039/D4EM00415A.

This paper presents an overview of the methods of nested sequents or tree-hypersequents that were originally introduced to provide a comprehensive proof theory for modal logic. The paper retraces the history of how these methods have developed. Its aim is also to present, in an unified and harmonious way, the most recent results that have been obtained in this framework. These results encompass several technical achievements, such as the interpolation theorem and the construction of countermodels. Special emphasis is also given to the application to logics other than the standard modal ones as well as to relations to other proof theoretic formalisms.

Vineyard soils are often of inherently poor quality with low organic carbon content. Management can improve soil properties and thus soil fertility. In European wine‐growing regions, a broad range of inter‐row management strategies evolved based on specific local site conditions and the varying effects of management intensities on soil, water balance, yield and grape quality. Accordingly, there is a need to investigate the effects of locally common cover crop management strategies and tillage intensity on soil organic carbon content and soil physical parameters. In this study, we investigated the impact of the most common inter‐row management practices in Austria, France, Romania and Spain. In all countries, we compared paired sites. Each site with cover crops and inter‐row management of low intensity was compared with one site with (temporarily) bare soil and high management intensity. All studied sites with cover crops and low management intensity, except those in Spain, had higher organic carbon contents than the paired more intensively managed vineyards. However, the highly water‐limited Spanish vineyards with temporary cover crops had lower organic carbon contents than the paired sites with bare soil. Sites with more organic carbon had better results for bulk density, percolation stability (PS), hydraulic conductivity and available soil water, with soil hydraulic parameters being less pronounced than others. Country comparison of inter‐row weed control systems showed that PS was particularly low in sampled vineyards in Romania and Spain, where weed control is based on intensive mechanical tillage. Alternating management systems with tillage every second inter‐row showed a decrease in soil structure compared with permanent green cover. Thus, inter‐row management with cover crops and reduced tillage increases soil organic carbon content and improves soil structure compared with bare soil management. If local constraints, such as water scarcity, do not allow year‐round planting, alternating inter‐row management with several years of alternating periods may be an option to mitigate those adverse effects. However, negative impact on the soil structure occurs with the very first tillage operation, whereas negative effects on the carbon balance only appear after long‐term use of tillage.

Microplastics in urban runoff undergo rapid fragmentation and accumulate in the soil, potentially endangering shallow groundwater. To improve the understanding of microplastic transport in groundwater, column experiments were performed to compare the transport behavior of fragmented microplastics (FMPs ∼1‐µm diameter) and spherical microplastics (SMPs ∼1‐, 10‐, and 20‐µm diameter) in natural gravel (medium and fine) and quartz sand (coarse and medium). Polystyrene microspheres were physically abraded with glass beads to mimic the rapid fragmentation process. The experiments were conducted at a constant flow rate of 1.50 m day⁻¹ by injecting two pore volumes of SMPs and FMPs. Key findings indicate that SMPs showed higher breakthrough, compared to FMPs in natural gravel, possibly due to size exclusion of the larger SMPs. Interestingly, FMPs exhibited higher breakthrough in quartz sand, likely due to tumbling and their tendency to align with flow paths, while both sizes (larger and smaller relative to FMPs) of SMPs exhibited higher removal in quartz sand. Therefore, an effect due to shape and size was observed.

The intensity and frequency of inter‐row management in vineyards are highly diverse and depend on local environmental conditions and the wine grower's attitude and experience. Reasons for different management include water conservation, weed and pest control, biological activity promotion and soil fertility and biodiversity preservation. We studied different soil cover management in 16 paired vineyards located at eight sites in the Leithaberg and Carnuntum regions of eastern Austria. To this end, we compared inter‐rows with medium intensity (Periodically Mechanically Disturbed) and low intensity (Permanent Green Cover). We investigated the effects of these different management intensities on soil organic carbon, bulk density, saturated and unsaturated hydraulic conductivity, pore size distribution and percolation stability in the upper soil layer from 3 to 8 cm. Soil organic carbon and percolation stability were significantly higher and soil bulk density was significantly lower in vineyards with permanent green cover. No significant differences were observed for saturated hydraulic conductivity, pore size distribution and plant available water. This may be attributed to a minor effect as a result of the time lag of up to 2 years since the last tillage. Regression analysis to predict plant‐available water for local vineyard soils also showed that texture, total organic carbon and bulk density were suitable predictor variables. These results suggest that both investigated inter‐row management systems support a good soil structure for winegrowers. Organic carbon content and parameters interacting with organic carbon may still be improved with permanent vegetation cover systems; however, the positive effects on plant available water are limited.

Soil erosion from agricultural fields is a persistent ecological problem, potentially leading to eutrophication of aquatic habitats in the catchment area. Often used and recommended mitigation measures are vegetated filter strips (VFS) as buffer zones between arable land and water bodies. However, if they are designed and managed poorly, nutrients — especially phosphorus (P) — may accumulate in the soil. Ultimately, VFS can switch from being a nutrient sink to a source. This problem is further aggravated if the field runoff does not occur as uniform sheet flow, but rather in concentrated form, as is usually the case. To assess the impact of concentrated flow on VFS performance, we have taken soil core samples from field-VFS transition zones at six sites in Lower Austria. We determined a multitude of physical and chemical soil parameters, focusing on P fractions and indices. Our results revealed that concentrated flow can lead to an accumulation of P in the VFS. P levels in the VFS inside the area of concentrated runoff can be equal to or higher than in the field, even though they receive no direct fertilization. However, the concentration and distribution of nutrients in the fields and VFSs were also site-specific and affected by local factors such as the age of the VFS, cropping, and fertilization. Accordingly, there is a need for more sophisticated, bespoke VFS designs that can cope with site-specific runoff volumes and movements of nutrients that occur.

This chapter delves into the feasibility of implementing River Bank Filtration (RBF) as a sustainable and cost-effective solution for drinking water supply in Middle Eastern countries. Comprehensive assessments across diverse hydrogeological settings highlight both positive and negative influences on water quality. Notably, the study shows the successful application of RBF in alluvial aquifers along the Nile River (Egypt), Zarqa River (Jordan), and Sirwan Al-Kufa Rivers (Iraq), affirming the technique's viability. The interaction between surface water systems and adjacent coarse aquifers underscores the long-term effectiveness of RBF. The technology remarkably efficiently removes various pollutants, including organic and microorganic contaminants. However, careful design considerations are essential to minimize the contribution of ambient groundwater, known for elevated concentrations of organic compounds and metals. The ongoing operation of RBF wells is critical to sustained success, which helps increase the share of bank filtrate and counteracts declining surface water levels. Strategic well placement near the surface water system (aerobic zone) is recommended to prevent mobilization of iron (Fe) and manganese (Mn) into the bank filtrate. Economic analyses underscore RBF as a cost-effective alternative, delivering high water quality while surpassing conventional treatment techniques.

The Danube River is, at 2857 km, the second longest river in Europe and the most international river in the world with 19 countries in its catchment. Along the entire river, faecal pollution levels are mainly influenced by point-source emissions from treated and untreated sewage of municipal origin under base-flow conditions. In the past 2 decades, large investments in wastewater collection and treatment infrastructure were made in the European Union (EU) Member States located in the Danube River Basin (DRB). Overall, the share of population equivalents with appropriately biologically treated wastewater (without disinfection) has increased from 69% to more than 85%. The proportion of tertiary treatment has risen from 46 to 73%. In contrast, no comparable improvements of wastewater infrastructure took place in non-EU Member States in the middle and lower DRB, where a substantial amount of untreated wastewater is still directly discharged into the Danube River. Faecal pollution levels along the whole Danube River and the confluence sites of the most important tributaries were monitored during four Danube River expeditions, the Joint Danube Surveys (JDS). During all four surveys, the longitudinal patterns of faecal pollution were highly consistent, with generally lower levels in the upper section and elevated levels and major hotspots in the middle and lower sections of the Danube River. From 2001 to 2019, a significant decrease in faecal pollution levels could be observed in all three sections with average reduction rates between 72 and 86%. Despite this general improvement in microbiological water quality, no such decreases were observed for the highly polluted stretch in Central Serbia. Further improvements in microbiological water quality can be expected for the next decades on the basis of further investments in wastewater infrastructure in the EU Member States, in the middle and lower DRB. In the upper DRB, and due to the high compliance level as regards collection and treatment, improvements can further be achieved by upgrading sewage treatment plants with quaternary treatment steps as well as by preventing combined sewer overflows. The accession of the Western Balkan countries to the EU would also significantly boost investments in wastewater infrastructure and water quality improvements in the middle section of the Danube. Continuing whole-river expeditions such as the Joint Danube Surveys is highly recommended to monitor the developments in water quality in the future.

Exploring the contributions of new and old water to runoff during precipitation events in agricultural catchments is essential for understanding runoff generation, solute transport, and soil erosion. The aim of this study was to investigate the variability in the isotopic composition of precipitation and runoff in the 66 ha agricultural catchment in Austria, in the Hydrological Open Air Laboratory (HOAL), in order to compare two isotope hydrograph separation methods. The classical two‐component (IHS) and the ensemble hydrograph separation (EHS) were applied to multiple large events in May–October of 2013–2018 using δ ¹⁸ O and δ ² H. The peak flow new water contributions obtained by IHS were compared with the average new water fraction from EHS. The average new water fraction calculated with EHS based on regular weekly sampling was close to zero, which can be explained by the large diffuse groundwater discharge into the stream between the events. When only investigating events with high temporal resolution sampling, the results suggest that EHS provided average new water fractions during peak flows (0.46 ± 0.04 for δ ¹⁸ O, 0.47 ± 0.03 for δ ² H) that were close to the averages obtained by IHS (0.47 for δ ¹⁸ O, 0.50 for δ ² H). New water fractions tended to be higher for larger rainfall intensities. High peak flow new water fractions could be explained by the agricultural land use and soils with low permeability promoting overland flow generation and by some of the tile drainage systems contributing to the delivery of water. In conclusion, a weekly sampling frequency was not sufficient in the HOAL but instead high‐resolution sampling during events was necessary to estimate the average new water contributions during events. While EHS may be a more robust approach compared to IHS, as it relaxes some of the assumptions of IHS, IHS can provide information on the variability of new water contributions of individual events.