Cattle feedlot wastewater contains high organic and nutrient loads along with residual veterinary antibiotics, posing risks to downstream soil and groundwater quality. This study evaluates Macrophyte-Assisted Vermifiltration (MaVF) as a sustainable, low-energy, nature-based treatment system for such antibiotic-rich wastewater. A comparative assessment was conducted using two macrophyte species, Canna indica and Saccharum spontaneum, integrated into vermifiltration units and monitored for 126 days. Weekly analyses included COD, nutrients (TN, TP, NH₄⁺–N, PO₄³⁻–P), and commonly occurring antibiotics. MaVF–Canna demonstrated the highest treatment efficiency, achieving 56.1 ± 1.6 % COD removal, 43.4 ± 1.7 % TN removal, and 50 ± 5.4 % TP removal. Antibiotic removal across the MaVF systems ranged from 36–54 % for most compounds, with Canna indica consistently outperforming Saccharum spontaneum. MaVF–Canna exhibited superior performance compared to MaVF–Saccharum, which can be attributed to the higher root density, faster growth rate, and greater rhizosphere oxygenation capacity of Canna indica. These traits enhance plant–microbe–earthworm interactions, leading to improved degradation of organics, nutrients, and antibiotics. Ampicillin showed limited removal (2–4 %) across all systems, reflecting its known recalcitrance. A life cycle cost (LCC) assessment revealed that MaVF provides an economically viable and resource-efficient alternative to conventional systems, with a total treatment cost of 261 ₹ m⁻³. The low operational energy demand and use of locally available materials further support its suitability for decentralized rural applications. Overall, the findings underscore the potential of MaVF particularly with Canna indica as a climate-resilient, cost-effective, and environmentally sound nature-based solution for mitigating antibiotics and co-occurring pollutants in livestock wastewater.

How to cite: Singh, S., Singh, R., and Yadav, B. K.: Comparative Performance of Canna indica and Saccharum spontaneum in nature-based Systems for treatment of antibiotic-laden wastewater, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-296, https://doi.org/10.5194/egusphere-egu26-296, 2026.

A substantial body of literature documents the benefits of nature-based solutions in urban areas, while local authorities often struggle to translate these insights into practice. This gap persists because governance arrangements remain fragmented, responsibilities are distributed across multiple institutions, and decision-making is frequently constrained by short-term planning and limited long-term empirical evidence. While nature-based solutions are increasingly promoted as effective adaptive measures, it remains insufficiently understood how specific local governance conditions enable or hinder their sustained and institutionalised implementation. The aim of this paper is to examine just how governance structures operate in a specific context to shed light on the performance of water-related nature-based solutions in coastal cities and to improve knowledge regarding specific adjustments in the institutional setup or decision-making process, which could be capable of supporting the uptake of nature-based solutions in the urban context. The research draws on a set of semi-structured interviews with key stakeholders from the coastal city of Piran, Slovenia, representing diverse expertise and responsibilities in municipal spatial planning, water and wastewater management, environmental and cultural heritage protection, and civil society. The paper synthesises how participants understand governance barriers, how coordination occurs across institutional levels, and how knowledge from past projects informs current decisions. These empirical, locally grounded insights are compared with barriers widely discussed in the literature to assess the relevance of literature to the real-world case study and offer insights into making the literature more actionable. Preliminary findings show that strengthening communication between municipal departments, public utilities and external actors is essential for maintaining continuity beyond project-based cycles and for embedding nature-based solutions into local practice, but that the preference for nature-based solutions is often tied to the personal views rather than an institutional mandate. By providing fine-grained empirical insight into how governance barriers operate in practice, this study contributes to advancing more durable, learning-oriented water governance pathways for nature-based solutions in coastal cities. This research, part of the ongoing consortium-based European project, seeks to generate new granular insights on the operation of nature-based solutions in practice with the view of developing a more durable water governance pathway.

How to cite: Jamsek, J. and Penca, J.: Beyond single drops: How local authorities can improve the uptake of nature-based solutions for water governance?, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-2538, https://doi.org/10.5194/egusphere-egu26-2538, 2026.

Green and Blue Infrastructure (GBI) and Nature-Based Solutions (NBS) are becoming increasingly important for sustainable water management and climate change adaptation, especially in urban areas facing greater hydrological pressures. This study uses a literature-based comparative analysis, based on a critical review of scientific publications, technical reports, and design documents. The analysis focuses on two European case studies: the proposed GBI/NBS project in Grundarfjörður, Iceland, and the completed intervention at the Scalo intermodale di Milano–Segrate.
The analysis shows that the Grundarfjörður project mainly tackles heavy rainfall and rapid surface runoff by adopting sustainable urban drainage systems combined with microclimatic adaptation strategies. This takes place within a setting of high climatic variability and intricate geopedological conditions. Conversely, the Milan–Segrate case, evaluated solely through published project documents and monitoring records, concentrates on reducing hydraulic risk, environmental regeneration of a key infrastructural zone, and the multifunctional role of open spaces as vital links between hydraulic systems, landscape, and urban areas.
The comparison based on the documentary highlights notable differences in bioclimatic conditions, design approaches, and the importance of environmental monitoring for the long-term assessment of GBI/NBS performance. These results underline the need for a unified methodological framework that combines urban hydrology, ecology, and spatial planning to enhance solution transferability and strengthen the reliability of long-term effectiveness evaluations.

How to cite: Sgalippa, N.: Urban Hydrological Adaptation Through GBI and NBS: A Comparative Study of European Case Studies., EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-3034, https://doi.org/10.5194/egusphere-egu26-3034, 2026.

With the acceleration of urbanization, the building density and pollution emission sources have increased, and the problem of urban tropospheric ozone has become increasingly severe. Traditional pollution control strategies have focused on source reduction. However, emission reductions have reached their limits, making substantial further reductions difficult to achieve while maintaining socio-economic stability. Moreover, ozone is a secondary pollutant whose formation exhibits a non-linear relationship with its precursors (VOC and NO_x). Addressing the issue solely through source reduction of these precursors proves insufficient. Consequently, there is an urgent need for atmospheric ozone self-purification technologies to tackle air pollution. By applying catalytic materials to building facades, atmospheric ozone pollution can be self-purified at low cost and with zero energy consumption. Under ambient temperature and pressure, alongside typical wind speeds and sunlight conditions, these catalytic materials decompose ozone into oxygen.

Application experiments have been conducted under real meteorological conditions in a park. Results indicate that coating park perimeter walls with catalytic materials can reduce nearby ozone concentrations by 5%-20%, with effects extending up to 18 m. Moreover, the higher the temperature, the greater the wind speed and the higher the relative humidity, the overall level of ozone will also increase. These results further confirm that wall catalysis significantly reduces ozone in a small near-wall range, but on a larger spatial scale, the distribution of ozone is still controlled by the atmospheric background and flow field. Therefore, numerical simulations at the urban block scale are required to evaluate the effectiveness of self-purification materials in ozone removal.

The study selected a real building complex in Nanchang as the computing domain, with a horizontal range of approximately 1000 m × 600 m, and constructed a three-dimensional physical model through the urban building outline. In this model, we first examined the impact of varying inflow wind speeds (1 m/s, 3 m/s, and 6 m/s) on ozone distribution. The results show that higher wind speeds correlate with overall elevated ozone concentrations, indicating that atmospheric background transport plays a dominant role. We have paid particular attention to several typical street canyon configurations. These include combinations with aspect ratios of 0.75 and 1.0, as well as scenarios where the canyon is parallel to the wind direction or forms a 40° angle with it. Ozone concentration profiles reveal that different combinations of aspect ratio and wind direction significantly alter vortex structures, thereby influencing ventilation within the canyon and pollutant residence times. Preliminary findings indicate that deep street canyons with larger aspect ratios and those aligned parallel to the prevailing wind are more prone to forming high ozone exposure zones, where ozone catalytic effects are enhanced. Conversely, canyons with wider openings or those angled relative to the wind direction exhibit superior ventilation, resulting in ozone concentrations closer to background levels. In summary, this study confirms the effectiveness of applying ozone-catalysing materials to building facades for urban ozone control.

How to cite: Luo, Q. and Hang, J.: The influence of catalytic coating walls on O3 in urban street canyon based on CFD simulation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-4461, https://doi.org/10.5194/egusphere-egu26-4461, 2026.

As climate extremes intensify, Nature-based Solutions (NbS) are increasingly integrated with traditional infrastructure to enhance urban flood resilience. However, current design paradigms often treat NbS and grey infrastructure as separate, additive components, failing to capture the complex hydraulic interactions required to withstand unprecedented flood events. Based on a systematic review of literature from 2015 to 2025, this study critically analyzes the engineering limits of hybrid systems and proposes a conceptual framework to operationalize true resilience. The review reveals a critical gap: while NbS is widely praised for its sustainability, its capacity to prevent the brittle failure of conventional systems remains under-quantified. Existing studies predominantly focus on volume reduction, overlooking how NbS can modulate hydraulic loading rates and provide functional redundancy during extreme events. We argue that urban flood resilience is not merely about increasing total retention capacity but about optimizing the synergistic coupling between the saturation characteristics of NbS and the discharge limits of grey infrastructure. To address this, we introduce an integrated resilience assessment framework that moves beyond static capacity analysis. This approach quantifies how NbS acts as a "resilience buffer," delaying system failure and extending the operational range of drainage networks. By shifting the focus from additive performance to synergistic interaction, this study provides a robust pathway for designing hybrid NbS that remains functional under deep uncertainty, offering a strategic guide for future urban flood management.

Acknowledgement
This work was supported by National Research Foundation of Korea(NRF) grant funded by the Ministry of Science and Technology (RS-2024-00356786) and Korea Environmental Industry & Technology Institute grant funded by the Ministry of Environment (RS-2023-00218973).

How to cite: Ashraf, M., Heo, E., Li, S., and Park, J.: Redefining Urban Flood Resilience: A Systematic Framework for the Synergistic Integration of Hybrid Nature-based Solutions, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6249, https://doi.org/10.5194/egusphere-egu26-6249, 2026.

Urban runoff transports diverse organic pollutants that threaten urban waters and soils. Blue-green infrastructures such as tree trenches may help to mitigate these impacts. Tree trenches are increasingly implemented in cities to manage urban runoff. While the hydraulic and physical retention functions of tree trenches are well studied, their potential to perform biological cleaning processes is less understood.

This study explores whether organic carbon amendments can stimulate the microbial transformation of organic pollutants in tree trench systems. We hypothesize that stimulation with low molecular weight organic carbon increases microbial activity and promotes co-metabolic degradation pathways in the tree rhizosphere. This would support active pollutant removal rather than passive retention.

To test this hypothesis, an outdoor mesocosm experiment was established that simulates a real tree trench in Leipzig, Germany. Linden trees (Tilia cordata) were planted in 1000 L containers filled with the volcanic substrate used in Leipzig, which has rapid permeability to ensure better infiltration. The systems received 60 L of water within two hours to simulate a rainfall event. The water contained a mix of fuel spills, fuel additives, and tire wear pollutants commonly found in urban runoff waters (naphthalene, methyl tert-butyl ether, and 1,3-diphenylguanidine). The common industrial by-products molasses and whey were applied as organic stimulants of microbial metabolism. The system’s response was investigated from a plant, geochemical, and soil microbial perspective.

Following the rainfall event, all tree trenches remained oxygen-depleted during incubation, which was evident from a consistently low redox potential of -40 mV in the percolating soil water. In the plant-available porewater of the linden trees, the redox potential further decreased to -60 mV over time across treatments, indicating microbial fueling through plant exudation. A minor increase in bulk and rhizosphere pH from 7.8 to 8.0 across 4 weeks in trenches amended with and without contaminants and/or organic stimulants indicated a well-buffering trench substrate and allowed comparison of biogeochemical data. An accompanying laboratory study confirmed the mineralization of 13C-labeled naphthalene and, furthermore, that organic stimulants enhanced this process. Overall, organic stimulants seemed to increase biological activity in the rhizosphere as indicated by changing nitrogen speciation and a decrease in dissolved organic carbon. Besides monitoring porewater geochemistry shifts, genes coding for key enzymes of degradation pathways specific to each contaminant were quantified. They were correlated with shifts in microbial community composition and activity by assessing the abundances of 16S rRNA genes and transcripts in the bulk and rhizosphere soil of the trench system. Together, these patterns demonstrate that stimulation with organic compounds can activate biological processes relevant for pollutant transformation, even under complex and heterogeneous tree trench conditions.

This work aimed to evaluate biological stimulation as a design principle for tree trenches in urban water management. By promoting active cleaning rather than passive retention, blue-green infrastructures could become more effective tools for sustainable water runoff treatment, thereby strengthening the role of nature-based solutions in sustainable urban water management.

How to cite: Seiferth, K., Schumacher, M. C., Vogt, C., Schlosser, D., Kümmel, S., and Muehe, E. M.: Influence of organic stimulation on plant-microbe interactions in tree trenches exposed to urban runoff contaminants, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12045, https://doi.org/10.5194/egusphere-egu26-12045, 2026.

Nature-based wastewater treatment systems offer sustainable alternatives to conventional infrastructure due to lower operational costs and high environmental adaptability. This study investigates the efficiency of a laboratory-scale floating wetland (FW) utilizing plants of the genus Azolla to treat domestic wastewater under varying operating conditions. The experimental setup consisted of two 9-L reactors with different initial Azolla biomass loads of 20 g and 40 g, operated in batch mode. System performance was evaluated by the systematic characterization of chemical oxygen demand (COD), ammonia nitrogen, phosphorus, pH, dissolved oxygen, and alkalinity. The experimental period was divided into three phases: an initial acclimation period comparing reactors exposed to constant artificial light and natural light, an active monitoring phase, and a nutrient removal kinetic phase to assess daily pollutant removal rates, both conducted under natural light conditions.

The comparative analysis, during the first phase, demonstrated that light regime significantly affected FW performance, with natural light yielding higher removal efficiencies for both organic matter and ammonia nitrogen. COD removal was 90 and 96% in artificial and natural light, respectively, while the corresponding ammonia nitrogen removal was 18 and 40%. Furthermore, in the second phase, a higher initial biomass concentration (40 g) led to an 8% increase in phosphorus removal. During the nutrient removal kinetic phase, in the 4^th week of operation, the first-order removal constants were 0.1 and 0.26 d^-1 for COD, 0.2 and 0.36 d^-1 for ammonia nitrogen, and 0.43 and 0.4 d^-1 for phosphorus, for the 20 and 40 g FW, respectively. However, biomass yield was higher in the 20-g culture, compared to the 40-g during the entire operation period. These findings indicate that although Azolla-based FW are inherently robust, optimizing initial biomass concentration and light exposure is essential for achieving specific effluent quality targets.

How to cite: Manariotis, I., Polyzou, S. V., and Biliani, S.: Performance of Azolla-Based Floating Wetland for Domestic Wastewater Remediation, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-12672, https://doi.org/10.5194/egusphere-egu26-12672, 2026.

To support global decarbonization and climate resilient infrastructure targets, this study experimentally investigates the bond performance of a sustainable, economic zero-cement alkali activated system produced from industrial and agricultural byproducts. The proposed alkli activated system utilizes blast furnace slag and rice husk ash, thereby reducing reliance on carbon intensive Portland cement while promoting circular use of waste materials and lowering environmental footprints.

The effectiveness of alkali activated system as a concrete repairing agent for ageing and climate exposed infrastructure is governed primarily by both strength of the repairing agent and its bonding behaviour with existing concrete. The bonding behaviour plays a critical role in the long term performance of repaired systems under sustained load, moisture ingress, and thermal variability associated with climate change. Accordingly, a comprehensive experimental program has been prepared to evaluate bonding behaviour under various stress states, including pure tension, pure shear, and combined shear and compression.

The combined contribution of blast furnace slag and rice husk ash for development of interfacial strength and cracking pattern of the alkali activated system has been investigated through controlled laboratory testing and compared with that of conventional Portland cement based concrete. The results demonstrate that the blast furnace slag and rice husk ash based alkali activated system exhibits superior bonding performance compared with conventional cement based repair mortars, indicating improved resistance to debonding, cracking and moisture induced deterioration.

By enabling durable, low carbon repair solutions that extend the service life of existing structures while reducing raw material consumption and greenhouse gas emissions, this study highlights how material technologies that are aligned with Nature-based Solutions can contribute to sustainable and resilient adaptation of the built environment under a changing climate.

How to cite: Laskar, S. M., Pandit, P., and Hussain, A.: Sustainable Zero-Cement Repairing Agent for Climate-Resilient Infrastructure, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-13037, https://doi.org/10.5194/egusphere-egu26-13037, 2026.

Living roofs are commonly evaluated using event-scale runoff metrics, while gas-phase dynamics are rarely considered in relation to rainfall timing. This study investigates how storm sequencing and hydrological memory jointly influence runoff response and near-surface CO₂ concentration in living roof systems.

Rainfall, runoff, and near‑surface CO₂ concentration were monitored on five experimental roof trays in Auckland, New Zealand, representing three substrate configurations of equal depth: an unvegetated stone ballast reference and two vegetated substrates (Daltons living roof mix and eco‑pillows). We analysed a six‑month winter‑to‑spring period (1 June–30 November 2025) with variable inter‑event dry durations. Rainfall events were classified by inter‑event dry duration to distinguish closely spaced and isolated storms. Runoff response was quantified using runoff coefficients and peak discharge metrics normalized by rainfall forcing, while CO₂ dynamics were assessed during rainfall and inter‑event periods and expressed as anomalies relative to the stone reference (ΔCO₂).

Closely spaced storms generally produced higher runoff coefficients and reduced peak attenuation compared with isolated events, consistent with incomplete hydrological recovery. However, isolated events associated with exceptionally large or intense rainfall like the one in July 2025, with a depth of 82.8 mm and an intensity of 4.17 mm/hr, can produce high peak discharges, indicating that storm characteristics may override memory effects under extreme conditions. CO₂ concentrations increased during rainfall and remained elevated between closely spaced events, indicating a gas‑phase “memory” associated with rainfall‑driven state changes. Substrate type strongly modulated the CO₂ signal: Daltons showed persistent CO₂ drawdown relative to stone (mean ΔCO₂ ≈ −8.9 ppm), whereas eco‑pillows exhibited net enrichment (mean ΔCO₂ ≈ +11.8 ppm, increasing in spring). These results highlight non‑stationary coupled hydrological and gas‑phase behaviour in living roofs, while noting that concentration‑based metrics capture near‑surface signals rather than CO₂ fluxes.

How to cite: Soe, A. N., Dong, S., Shamseldin, A. Y., Latu, K., Zorn, C., Attafuah, E., and Devine, R.: Hydrological Recovery and Gas‑Phase Memory Across Green Roof Substrates: Evidence from Auckland, New Zealand, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-14989, https://doi.org/10.5194/egusphere-egu26-14989, 2026.

ABSTRACT

Urban ponds are widely recognised as high-emission hotspots of greenhouse gases (GHGs), mainly in the form of methane. Whereas hyper-eutrophication also simultaneously presents an opportunity to harness algal biomass for substantial energy recovery. The present study addresses this dual challenge and opportunity by studying Hauz Khas Pond, a 15-acre hyper-eutrophic urban pond in South Delhi, India. This pond receives a continuous inflow of treated effluent to maintain water levels in the pond.

Comprehensive long-term monitoring of nutrient dynamics, water quality, and biomass generation revealed persistent hyper-eutrophic conditions with TSI of 197.6 ± 10.7 with minor seasonal fluctuations. Continuous nutrient loading ((PO₄³⁻: 4–8 mg L⁻¹, NO₃-N: 1.9-3.13 mg/L),and shallow depth (1-2.5m), is causing high algal productivity and benthic methanogenesis leading to high methane emissions (~1.7 times freshwater systems). Although biomass assessment revealed average standing algal biomass in pond of approximately 183 tonnes and 43% of which is excess eutrophic biomass (approx. 80 tonnes) and can be harnessed for energy recovery without affecting ecological health of aquatic life in pond. The harvested algal biomass was characterized using biochemical methane potential assays, which demonstrated competitive methane yields under anaerobic digestion. This recoverable fraction alone holds methane generation potential of about 20000 m³ equivalent 0.37 m³m^-2. This finding indicates the possibility of an in situ energy recovery system. Since India has sufficient solar energy availability Power-to-Gas technology is further being proposed to enhance the methane percentage upto 95%.This technology involves injecting renewable hydrogen into the anaerobic digestion process, which upgrades the biogas produced to pipeline- grade methane.

By combining nutrient management, continuous harvesting, and integrating renewable energy, this nature-based algal harvesting approach can achieve controlled emissions while enhancing urban water quality. Our research redefines eutrophic urban lakes as multifunctional blue-green infrastructure that seamlessly integrate sustainable water management, climate mitigation, and circular bioenergy recovery in rapidly urbanizing regions.

Keywords: Bioenergy recovery; Blue–green infrastructure; Circular bioeconomy; Nature-based solutions; Urban eutrophic lakes; Methane emissions; Algal biomass harvesting; Anaerobic digestion

How to cite: Singh, A., Prajapati, S. K., and Bai, A.: Blue–green infrastructure of Urban Ponds: nature-based algal harvesting for greenhouse gas mitigation and bioenergy recovery, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16190, https://doi.org/10.5194/egusphere-egu26-16190, 2026.

Climate change poses an increasing challenge to the sustainable management of urban green infrastructure. Rising air temperatures, changing precipitation patterns and an increasing frequency and intensity of droughts lead to greater water stress for urban vegetation and consequently a higher demand for irrigation. Urban green infrastructure can only provide its multifunctional ecosystem services, such as cooling, when sufficient water is available. This highlights the importance of reliably assessing future irrigation requirements. This work presents a methodological framework for the spatial and temporal estimation of irrigation requirements for urban green infrastructure under current and future climatic conditions.

The presented approach is based on a quantitative assessment of irrigation deficit, which is defined as the difference between the water demand of the vegetation and the amount of effective precipitation. The methodological framework integrates evapotranspiration-based, vegetation-ecological and hydrological components, following established scientific approaches [1]. Reference evapotranspiration is calculated using the Hargreaves equation. Additionally, the study systematically assesses scenario-based changes in irrigation demand resulting from alternative urban green infrastructure development pathways.

Vegetation-specific water demand is estimated using the landscape coefficient approach. For this purpose, specific landscape coefficients were derived for typical types of urban green infrastructure, integrating the effects of vegetation type, planting density, and water stress into a multiplicative coefficient. This enables a differentiated representation of the variety of vegetation structures and management strategies found in urban green spaces. Natural water supply is accounted for by estimating effective precipitation using the NRCS Curve Number method, which characterizes runoff and retention processes in urban areas and quantifies the proportion of precipitation available within the root zone.

The spatial implementation is carried out within a grid-based framework with a spatial resolution of 100 m × 100 m across three case studies. Within each grid cell, the proportions of different vegetation types, the associated normalized difference vegetation index (NDVI), land use information, and soil parameters are compiled. Area-weighted vegetation coefficients and hydrological parameters are then aggregated to the grid areas, which serve as the basis for irrigation calculations.

Analyses are performed for a historical reference period (1991–2020) and a future period (2031–2060) under different climate change scenarios (RCP2.6, RCP4.5, and RCP8.5). This allows a systematic evaluation of climate-driven changes in irrigation requirements. The results are evaluated monthly and visualized using box plots to illustrate changes in irrigation requirements and associated uncertainties. The results show a potential increase in irrigation demand in the case studies, with scenario-specific differences. In addition, the influence of different developments in green infrastructure on irrigation requirements is highlighted.

Overall, the developed methodology provides a scalable, integrated, and scientifically robust tool for assessing the irrigation requirements of urban green infrastructure.

Acknowledgements: The presented research is funded by the Federal Ministry for Agriculture and Forestry, Climate and Environmental Protection, Regions and Water Management Republic of Austria

References:

• Cheng, H.; Park, C.Y.; Cho, M.; Park, C. Water Requirement of Urban Green Infrastructure under Climate Change. Science of The Total Environment 2023, 893, 164887, doi:10.1016/j.scitotenv.2023.164887.

How to cite: Stelzl, A., Kudaya, F. S., Rajic, J., Buttinger, U., Pitha, U., Pucher, B., Schwab, E., and Fuchs-Hanusch, D.: Estimating Future Irrigation Requirements of Urban Green Infrastructure under Climate Change, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-18701, https://doi.org/10.5194/egusphere-egu26-18701, 2026.

Urban heat island (UHI) effects can result in numerous negative impacts on the health and well-being of urban residents. Modelling UHI intensity is essential for characterising its spatiotemporal dynamics, assessing urban heat exposure risks, and projecting future changes under urbanisation and climate change. This study adopts the ADMS-Urban Temperature and Humidity model to simulate the interannual variation and spatial distribution of UHI intensity in the West Midlands, UK. This model has been validated in a previous, smaller-scale study conducted in Birmingham city. The model inputs include the spatial distributions of three thermal attribute parameters (i.e. thermal admittance, surface resistance to evaporation, and albedo) as derived from land-cover datasets and rasterised to a 100 m resolution, upwind meteorological data, urban canopy, terrain, and anthropogenic heat. The model outputs include the long-term variation of temperature and its perturbations at selected locations for receptor runs and high-resolution short-term contour maps for the contour runs. The preliminary output of this study will be a baseline in the year 2023. In this baseline, we output the UHI intensity of the West Midlands, including temporal variation on receptors and instantaneous spatial distributions. This baseline could be the basis for modelling scenarios in the future. Based on changes in land cover caused by urbanisation, in the next step, we could simulate the changes in UHI intensity relative to the baseline due to land-cover change, such as the expansion of green spaces, and the replacement of natural surfaces in rural areas by urban built-up areas. Future scenarios could also include patterns of temperature and perturbation changes under new upwind meteorological conditions induced by climate change, as well as changes in UHI driven by increased anthropogenic heat emissions. These results can be used to test the effectiveness of strategies for mitigating the UHI through urban and green space planning, thus providing data support for the planning of climate-resilient cities.

How to cite: Lu, Y., Zhong, J., Stocker, J., Hamilton, V., and Johnson, K.: Neighbourhood scale Urban Heat Island modelling in the West Midlands, UK Using ADMS-Urban Temperature and Humidity model, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19247, https://doi.org/10.5194/egusphere-egu26-19247, 2026.

Rapid urbanisation in Oman’s extreme climate is intensifying water stress and expanding Urban Heat Islands (UHI), which directly threaten population health, economic productivity, and municipal budgets. Urban planners must optimise resource allocation and capital investments while maintaining urban livability. This study presents a Digital Twin (DT) framework, grounded in the Astra Terra architecture, to model the dual benefits of Nature-based Solutions (NbS) for UHI mitigation and hydrological resilience. In contrast to traditional models that focus exclusively on vegetation, this approach incorporates "wetness" as a primary variable in regulating the urban microclimate.

The methodology integrates a federated data ecosystem, utilising the Copernicus Climate Data Store (CDS) for baseline indicators and Landsat 8 thermal imagery for hotspot identification. A Data Fusion Core merges satellite Earth Observation data with three-dimensional urban morphology. The framework follows FAIR data principles and high-performance computing (HPC) standards, ensuring scalability and policy-driven simulation capabilities compatible with the Destination Earth (DestinE) platform.

As a proof-of-concept demonstrator, this framework explores the theoretical ability to simulate urban responses to varying 'wetness' levels. This initial iteration focuses on modeling 'wet infrastructure' to establish the basic principles of hydro-thermal feedback in arid environments. By mapping existing wadis and topographical depressions, the framework simulates Blue-Green Infiltration Basins and water-retention zones. These scenarios are used to evaluate two critical environmental and economic responses:

• Hydrological Resilience and Financial Optimisation: Zones are modeled as Managed Aquifer Recharge (MAR) sites. The Digital Twin simulates how infiltration rates stabilize local aquifers, thereby reducing the long-term costs associated with water scarcity management. Incorporating native species such as Acacia and Date palm, the model demonstrates ecological balance with minimal maintenance requirements.
• Thermal Cooling and Public Health: The framework quantifies the thermal response to increased soil moisture. Simulations indicate that higher thermal inertia and latent heat dissipation can reduce surface temperatures by 3–5°C near critical infrastructure. This temperature reduction is directly associated with improved population mobility and reduced heat-related health risks, both of which are essential for sustaining economic activity and resident well-being.
• Eco-Hydrological Feedback: "Greenness" serves as a biological indicator of subsurface water availability. The Digital Twin models the feedback loop in which urban vegetation protects water resources from evaporation, thereby supporting the longevity of urban investments.

Impact and Decision Support: Through advanced analytics, the Digital Twin provides actionable insights to help planners prioritise multifunctional spaces. By demonstrating that interventions are both thermally effective and economically viable, this approach offers a practical roadmap for reducing complexity in urban planning and enhancing the climate resilience of heat-stressed arid cities.

How to cite: van den Dool, G., Jiang, A., and Elhajj, M.: Dual-Benefit Digital Twins: Modeling Water Retention and Urban Heat Mitigation in Arid Cities, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-19255, https://doi.org/10.5194/egusphere-egu26-19255, 2026.

Urban waterfronts are important parts of the city. These spaces improve social life, regulate the microclimate, and strengthen place identity. They often remain inaccessible, underused, and degraded. This study explores how blue–green infrastructure can revitalise neglected waterfronts and transform them into public spaces that are open to everyone and resilient to climate change. The research focuses on two European capitals – Podgorica (Montenegro) and Reykjavík (Iceland). Two contrasting cultural and climatic contexts of the Nordic and Balkan regions are examined. The aim of the study is to identify, through these two case studies, different relationships between water and urban space.

In Podgorica, the banks of the Morača River are occupied by logistics and storage facilities. These physical and visual barriers limit the city’s connection with the riverfront. The development of public spaces along the river is therefore restricted. This is particularly important given the role of the river as a cooling corridor in a city that faces extremely high summer temperatures and is ranked among the warmest European capitals. In Reykjavík, the transformation of industrial zones into residential areas has improved land-use efficiency along the waterfront. However, due to insufficient integration of blue–green infrastructure and unfavourable microclimatic conditions, the waterfront remains insufficiently socially activated.

The study uses a mixed-method approach. On-site work and qualitative methods are focused on space users. GIS analysis is used to define the location of built structures, their relationship with water, and the public accessibility of the waterfront. Fieldwork includes walking diaries and recording patterns of how people use waterfront areas. Surveys are used to assess frequency of use and functional integration of waterfront spaces. In both cases, the results indicate insufficient use of these areas. This is directly related to microclimatic constraints and spatial barriers. The findings confirm the importance of climate-responsive revitalisation. Blue–green infrastructure is presented as a key element for enabling urban waterfronts to function as accessible and socially meaningful public spaces, contributing to long-term urban resilience.

How to cite: Medenica, B., Finger, D., and Mašanović, N.: Revitalisation of Neglected Urban Waterfronts through Blue-Green Infrastructure:A Comparative Study of Reykjavík, Iceland, and Podgorica, Montenegro, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-6098, https://doi.org/10.5194/egusphere-egu26-6098, 2026.