2026-03-31
Akshay Kumar, Mahima Madan, Vinod Kumar, Jaydeep Bhattacharya, Kashyap Kumar Dubey
Raman spectroscopy (RS) is a widely employed technique for analyzing emerging environmental pollutants, microplastics and nanoplastics (MNPs), detection of biomolecules, identification of cells and pathogens. Detecting, identifying, and quantifying these particles in environmental samples and living organisms poses significant challenges due to their minute size, irregular shapes, diverse polymer compositions, surface coatings, and large surface areas that readily attract chemical and microbial contaminants. Raman Spectroscopy is a reliable, specific, fast, more sensitive method for the characterization of small sized particles. Moreover, the handheld Raman device is easily deployable in the field. This review addresses the key analytical strengths and the challenges that limit precise characterization of MNPs and provide recommendations to improve data reliability, that further include strategies to mitigate common quality control issues, particularly the challenge of distinguishing between plastic particles present in the sample and those introduced through contamination during sampling, processing, or analysis. Recently, the use of artificial intelligence (AI) and machine learning has been incorporated with Raman spectroscopy to facilitate the detection of MNPs and provide automation.
DOI: 10.3389/frwa.2026.17639162026-03-25
MD Shaibaz Khan, Marwan Fahs, Ahmed Hadidi, Husam Musa Baalousha
Groundwater recharge estimation in arid regions is challenged by data scarcity and high uncertainty. This study presents a Physics-Informed Bayesian Neural Network (PI-BNN) to quantify groundwater recharge and its uncertainty in the South Al Batinah (SAB) Basin, northern Oman. The PI-BNN was applied within a soil-moisture mass balance framework using 34 years (1990–2023) of monthly FLDAS remote sensing data, embedding the water balance equation directly into the training loss function through nine physics-informed penalty terms. Results were compared against Latin Hypercube Sampling (LHS) using the same inputs. Recharge is highly seasonal and episodic, peaking in December (~5–6 mm/month) with moderate values in February–March and July, and negligible recharge during dry months. Annual recharge is estimated at approximately 16 mm/yr (PI-BNN) and 7–11 mm/yr (LHS). Precipitation variability accounts for more than 70% of recharge uncertainty during wet months. The PI-BNN reduces uncertainty bounds by approximately 50% compared to independent LHS while maintaining physically consistent estimates. An ablation experiment confirms that the physics-informed constraints, rather than the Bayesian architecture alone, drive physically plausible recharge recovery. The proposed methodology offers a robust and transferable framework for recharge estimation in data-scarce arid environments.
DOI: 10.3389/frwa.2026.17876592026-03-23
Kazuki Matsuo
In conflict-laden international river basins, collaborative governance has often relied on third-party involvement in conflict resolution. In recent years, increasing attention has been paid to the role of non-state actors—such as NGOs, research institutions, and private-sector actors—that differ in character from traditional international organizations. It has also been argued that such non-state actors may function as Track 1.5 diplomacy, bridging formal multilateral negotiations among state actors by facilitating dialogue and trust-building. However, empirical cases in which non-state actors have effectively played such roles remain limited. Against this backdrop, Global Infrastructure Fund Research Foundation Japan (GIF) and its support for water resource development in the eastern Himalayan region during the 1990s constitute a notable example. This study represents the first systematic attempt to document and analyze the evolution of GIF’s activities in this context. GIF engaged high-level stakeholders from India, Nepal, and Bangladesh by organizing international conferences and workshops aimed at promoting dialogue. It also facilitated the prioritization of transboundary river development projects, which had previously been pursued separately by each country. Nevertheless, amid political instability in the region—where governmental counterparts and project priorities shifted frequently—GIF faced organizational constraints inherent to non-state actors, limiting its ability to respond effectively to these changes. Furthermore, insufficient funding and a lack of engagement with local communities ultimately prevented the projects from being realized. Drawing on the GIF case, this study examines the conditions necessary for non-state actors to elicit sustained commitment from state actors in conflict-prone transboundary river basins.
DOI: 10.3389/frwa.2026.17623512026-03-19
Rashmi Kulranjan, Veena Srinivasan
In rapidly urbanizing regions, interconnected lake systems play a critical role. They regulate runoff, store water, and maintain urban hydrological balance. However, their functioning is shaped by anthropogenic interventions and natural characteristics. Lake functioning also exhibits spatial and temporal variability. These challenges are particularly acute in developing cities, especially in tropical regions. Yet, we do not understand how such interconnected human-water coupled systems operate and respond to natural and human influences at different scales. This study investigates how upstream–downstream interactions, temporal changes and human interventions shape lake behavior and function. For this, we used the case study of the cascading lake network of the Hebbal-Nagavara Valley in Bengaluru, India. We developed a hydrological model to simulate runoff and sewage flows across 44 interconnected lakes. The flows were simulated under varying management scenarios. High-resolution observed data at 15-min intervals were used to calibrate the model. Results reveal that upstream lakes are more sensitive to seasonal and catchment-level characteristics. In contrast, downstream lakes are primarily influenced by accumulated upstream flows. Sewage, treated or untreated, is the dominant source. This leads to perennial conditions and reduced variability as the flows accumulate downstream. Thus, both the location within the lake cascade and the own catchment characteristics influence the water quantity in a given lake. These in turn determine whether a lake can function effectively as a flood buffer, ecological site, or storage reservoir. The findings emphasize that lake functions are dynamic and dependent on both catchment characteristics and spatial location within the network. This underscores the need for differentiated, cascade-wide management strategies to enhance urban water security. Through this study, we have developed a diagnostic typology linking lake function to spatial position, inflow type, and temporal changes.
DOI: 10.3389/frwa.2026.17780712026-03-18
Teresa Serra, Marianna Soler, Jordi Colomer
Microplastic (MP) beaching is the buildup of microplastics (MPs) in sand and along the coastline. It is a growing environmental issue in which beaches act as traps for MPs, impacting marine life and potentially human health. This paper supports the hypothesis that microplastics (MPs) accumulation on sandy beaches is directly influenced by both sediment granulometry and proximity to anthropogenic sources. Two sampling campaigns were carried out at Pletera Beach, a nationally protected site in northeastern Spain on the western Mediterranean coast. This study focuses primarily on fibre and fragment abundances, as these were the dominant MP particles, accounting 95.88 and 84.40% of total MPs in the two sampling campaigns, respectively. The study further discusses how the surface distribution of MPs on beaches results from the capacity of microfibers and microfragments to infiltrate beach sediments. MP retention was higher in fine-grained sand sizes, suggesting that fine-sand beaches may be more prone to elevated surface MP concentrations due to a lower infiltration, whereas beaches characterized by coarser bed grains tend to present lower MP abundances at the surface due to the higher infiltration capacity. For the medium-grained sands, microfiber abundances were 7.6 fold higher than microfragments. Other grain-size fractions could not be considered in this study. Greater microfiber abundances are most likely caused by their entanglement within the interstitial spaces between sediment grains, indicating that differences in MP shape will result in differential depositional patterns. Higher MP abundances were found at the north of the Pletera Beach, and these were linked to both anthropogenic tourism and by the nearby port activities. Likewise, the stations closest to the Ter River had the lowest Pollution Load Indexes (PLI), which might be associated to the flushing and transport by the river while the stations closest to the northern urban area had the highest values. This study also reveals the high level of pollution at Pletera Beach, with localized MP abundances exceeding 6,000 MPs/kg, corresponding to Level 1 on the Higher Pollution Load Index.
DOI: 10.3389/frwa.2026.17680532026-03-09
Yan Wang, Zhao Cai, Shaozhi Chu, Peng Liu, Hongwei Liu, Jin Lin, Li Tang
Urban underground spaces are rapidly expanding, but their low elevation, limited drainage capacity, and strong enclosure make them highly vulnerable to pluvial flooding. To elucidate how inundation dynamics in 3D underground spaces under extreme rainfall translate into actionable risk indicators (e.g., depth thresholds and arrival time), we propose and cross-validate a rainfall-informed capacity–depth–damage (C–D–D) curve method and a physics-based computational fluid dynamics (CFD) inundation model. The first approach is a rainfall-informed C–D–D curves method that rapidly maps net inflow to depth evolution and warning indicators (e.g., threshold depth and arrival time). The second approach is a 3D-geometry-resolved CFD inundation model that simulates spatially distributed depths/flows under prescribed inflow and drainage/outlet conditions, providing high-fidelity validation and hazard maps. A GeoSLAM handheld 3D Laser Scanning system was used to reconstruct as-built, modeling-ready 3D geometry of the underground space, addressing the common limitation of idealized layouts in prior evacuation-time assessments and enabling geometry-specific inundation and warning-threshold predictions. Using an underground parking garage in Tongzhou District, Beijing as a case study, we evaluated flood dynamics and risks under rainfall scenarios with annual exceedance probabilities of 1%, 2%, and 5%. Results show that stronger rainfall significantly advances critical water-depth thresholds and compresses evacuation windows; for example, under P = 1%, the 0.2 m alert occurs 1.5 h earlier than under P = 2% and 5.3 h earlier than under P = 5%. The two methods exhibit strong consistency in threshold timing (typically within 0–1 h), while CFD resolves spatial heterogeneity and identifies medium-to-high risk zones earlier in the intrusion stage. This integrated framework supports rapid early warning, evacuation-window assessment, entrance protection, and drainage-capacity design. Novelty lies in (i) integrating handheld 3D Laser Scanning with a “curve-first, CFD-refine” dual-model workflow; (ii) cross-validating fast C–D–D-based warning thresholds against geometry-resolved CFD dynamics; and (iii) delivering actionable time-to-threshold warnings and spatial risk maps for emergency planning.
DOI: 10.3389/frwa.2026.17770132026-03-09
Ryo Tsuchida
Earlier disaster research has often assumed that the primary agent of choice is the autonomous human individual, overlooking how such decisions are shaped through relationships, notions, infrastructure, technologies, institutions, residential choice, and non-human environments. Following two major flood disasters in 2019 and 2021, local volunteer groups, municipal officials, and residents in Takeo City, Saga Prefecture engaged in various collaborative efforts to rebuild livelihoods, navigate administrative systems, and prepare for future events. This study examines how Japan’s emerging basin-based flood management policy, Ryuiki-chisui (River Basin Disaster Resilience and Sustainability by All), is implemented and reinterpreted in everyday practice through an ethnographic case study of Takeo City. Drawing on “logic of care,” “saikan (in-between disaster),” and “fluid,” the study analyzes how flood governance unfolds not as a sequence of rational choices or top-down directives, but as ongoing socio-technical tinkering shaped by relational labor, uncertainty, and situated forms of expertise. The findings show that Ryuiki-chisui operates as a dynamic set of practices that bridge the gaps between hydrological models, administrative frameworks, and residents’ embodied knowledge of the Rokkaku River basin. Volunteer intermediaries are critical in translating institutional categories, coordinating support for disaster certification and emergency repairs, and addressing the grey zones that fall between formal systems. Through these practices, flood governance has become a care-intensive process involving continuous adjustments across human and non-human actors such as pumps, gates, tides, homes, legal documents, and community networks. By highlighting the relational and ethically charged dimensions of life amid recurring disasters, this study advances international discourse on inclusive and transdisciplinary water governance. It demonstrates that effective basin-based flood management relies not only on technical measures, but also on cultivating forms of collaboration and care that sustain communities within continually changing environments. Practically, the findings suggest that Ryuiki-chisui will be more effective when intermediary work for translation, coordination, and grey-zone problem solving is recognized and resourced as part of basin governance, alongside conventional hard and soft measures. Conceptually, the study provides a practice-oriented specification of socio-hydrological coupling that can inform future interdisciplinary research integrating socio-hydrological modeling with ethnographic and participatory approaches.
DOI: 10.3389/frwa.2026.17659442026-03-04
Nesrine Kadri, Sihem Jebari, Naceur Mahdhi
Climate change represents today one of the most pressing environmental and socio-economic challenges facing humanity. However, its effect is uneven across regions, affecting most severely those whose populations depend directly on natural resources for their livelihood. Many studies have assessed climate vulnerability at national and regional levels, but there remains a lack of detailed analysis of how vulnerability manifests in rural areas and how it varies across local contexts, particularly in rural territories such as those in Tunisia. To address this gap, we investigate the vulnerability of local population to climate change in Rihana, a small rural territory in Sidi Bouzid governorate (Central Tunisia), through two complementary approaches. The first is a qualitative approach based on a participatory territorial diagnosis to assess the perception of climate change, current and future vulnerability; while the second is a quantitative approach based on the Climate Change vulnerability index_Intergovernmental Panel on Climate Change (LVI-IPCC). This methodology involves a comparative study of two Homogeneous Territorial Units (HTU) located upstream (HTU2) and downstream (HTU1) of the study area. The use of both qualitative and quantitative approaches provides a more comprehensive understanding of vulnerability, unlike other studies that limit themselves to a single approach and may therefore overlook certain crucial aspects. The results reveal that the local population in the study area perceives climate change as a threat to its main resources, particularly changes in rainfall and temperature patterns, drought and floods. Moreover, vulnerability levels vary significantly between the two areas, mainly due to differences in geographical position. The upstream part is more vulnerable (LVI-IPCC = 0.14), being more sensitive, more exposed and with a lower capacity to adapt, while the downstream part is less vulnerable (LVI-IPCC = 0.03). The results also show that households anticipate an increase in future vulnerability, with intensified soil erosion, declining rain-fed crops, growing water scarcity, and a heightened risk of rural exodus. Finally, this study confirms that even at small local scale vulnerability levels vary significantly so it’s important to integrate local knowledge with scientific tools when analyzing vulnerability at the local level. Based on these findings, the study emphasizes the use of a territorial approach and the active involvement of local communities. Such engagement enhances the resilience of rural populations and facilitates the development of effective adaptation strategies, while providing valuable insights for future research on climate.
DOI: 10.3389/frwa.2026.17505792026-03-04
Niels van Ras, Maurice Henssen, Tim Grotenhuis
Groundwater contamination by high-density and mobile-chlorinated volatile organic compounds (CVOCs) can lead to obstruction of all kinds of societal developments, such as the redevelopment of urban contaminated areas. Here, an integrated combination of technologies is presented in which the relatively new sustainable energy technology of Aquifer Thermal Energy Storage (ATES) is combined with in situ bioremediation (ISB) into RemediaTES (WKO-plus in Dutch). Laboratory and pilot studies at the municipality of Utrecht, the Netherlands, are combined to demonstrate the effectiveness of the proposed combination of technologies. From the results, it could be derived that a generally applicable area-oriented strategy that focuses on the prevention of CVOC transport to the receptor is most cost-effective in the long term. This combination of technologies, Aquifer Thermal Energy Storage (ATES) and in situ bioremediation (ISB), has the potential to become a breakthrough in the redevelopment of contaminated sites and a stimulus in the transition towards sustainable cities.
DOI: 10.3389/frwa.2026.17717342026-03-04
Cuthbert Madzivanyika, Beaven Utete, Tendai Joseph Mabvure, Ishmael Sango
Alone, the public sector cannot help nations achieve Sustainable Development Goal 6 target by 2030 due to financial constraints. Studies indicate that shifting water financing policies creates unequal social and economic impacts across different regions and timeframes. These disparities stem from the uneven natural distribution of water and the ongoing competition between different sectors for limited resources. Complex, ostensibly, synergistic public-private partnerships in water financing distends and intersperse with geopolitical dynamics disenfranchising fragile livelihoods in least developed nations with contrasting patterns for the developed world. A caveat looms in synthesizing, developing, decoding and integrating fiscal policies to incentivise multifaceted stakeholder financing, participation and uptake and mainstreaming holistic water and sanitation projects for sustainable livelihoods. This contemporary systematic and bibliometric literature review used a derivate SPAR-4-SLR model to evaluate the contribution of financial paradigms and fiscal policies toward the attainment of SDG 6 targets by 2030 for Africa, Asia, and South and North America. Extensive research highlights a persistent financing gap in the water and sanitation sectors, which fundamentally aligns with global patterns of systemic poverty. While developed nations have successfully leveraged functional public-private partnerships to address these shortfalls, lower-income regions remain trapped by a lack of investment capital. Future research imperatives delegate towards evaluating the stochastic impacts of capital markets, in tandem with tailored water market instruments buttressed by donor funding and innovative localized funding mechanisms to achieve SDG 6 by 2030.
DOI: 10.3389/frwa.2026.1703548