The confluence of escalating anthropogenic demands and climate change-driven hydrological alterations has accelerated the Mediterranean region’s vulnerability to water scarcity. This study applied the Soil Water Assessment Tool (SWAT+) model to simulate hydrological behavior and assess impacts of climate change in the El Torcón and Picadas reservoir catchments, located within the Tagus River basin in central Spain. Advanced SWAT + capabilities, incorporating reservoir operations and water allocation modules, were utilized to simulate regulated (non-natural) flow transfers from the catchments. Model calibration and validation employed an innovative multi-criteria framework that combined hard and soft calibration techniques by integrating statistical and process-based metrics to ensure not only statistically robust models but also realistic representation of hydrological processes. A multi-variable calibration strategy was adopted using observed reservoir inflow, storage, and streamflow data to enhance the models’ overall performance and reliability. Climate impacts were analyzed for the medium-term (2041–2070) and long-term (2071–2100) projections under the Shared Socioeconomic Pathways (SSP2–4.5 and SSP5–8.5) scenarios using 11 downscaled General Circulation Models (GCMs) from the Coupled Model Intercomparison Project Modeling in Phase 6 (CMIP6). The main findings of the study were: (1) Projections indicate declining precipitation (up to − 23%) and increasing potential evapotranspiration (up to + 23%) in both catchments, thereby intensifying hydrological deficits, particularly under SSP5–8.5. (2) Long-term projections under SSP5–8.5 scenario indicate substantial decline in water availability across both catchments, with reservoir inflows declining by − 53% in El Torcón and − 41% in Picadas, implying an accelerating transition towards an arid hydrological regime. Based on these findings, urgent implementation of adaptive and climate-resilient water governance strategies might be necessary to mitigate the effects of these climate change-driven hydrological disruptions. This study demonstrates the robustness of SWAT + as an effective tool for assessing future water resources availability, providing evidence-based decision-making, and informing long-term water resource planning amidst climate uncertainty, particularly in vulnerable, water-stressed regions. This graphical abstract presents a concise visual summary of the research by offering an overview of the study area, methodologies, and core findings, thus serving as a pivotal entry point for readers. The visualization starts with the two study areas, followed by the model configuration, then calibration and validation, then presents climate change simulation, and at the bottom is a visual summary that illustrates the future climate change impacts on key hydrological variables for both catchments. The research focused on two Mediterranean reservoir catchments (El Torcon and Picadas) located in Tagus basin in central Spain. The SWAT+ model was employed by integrating its advanced capabilities such as reservoir operations and water allocation modules to simulate the catchments natural and regulated hydrological behavior and climate projections, ensuring a robust assessment of future water security. Model calibration and validation were conducted using multi-criteria (hard and soft), multi-variable approach implemented through the R package SWATRunR, yielding statistically satisfactory performance while also realistically representing the catchment processes well. Climate change was simulated using 11 General Circulation Models (GCMs) from the Coupled Model Intercomparison Project Modeling in Phase 6 (CMIP6) under moderate (SSP2-4.5) and high (SSP5-8.5) emission scenarios, downscaled for the study areas. Projections for the medium-term (2041–2070) and long-term (2071–2100) were compared against the historical baseline (1981–2010) using an ensemble of the GCMs. Future projections revealed declining trends in total reservoir inflow in both catchments driven by declining precipitation and increasing potential evapotranspiration due to increased warming. Similar declining trends were observed in direct and groundwater flows, signaling a transition toward a more arid hydrological regime, further exacerbating the existing water stress in the region. The findings highlight the growing vulnerability of Mediterranean reservoir catchments to climate-driven aridification, with significant implications for future water resource planning. SWAT + model used to simulate climate change impacts on El Torcón and Picadas. Reservoir operations and water allocation protocols improved simulation of regulated flows. Multi-criteria, multi-variable calibration effectively captured flow and reservoir dynamics. Projected water availability declines under SSP5-8.5, signaling a shift to arid regimes. El Torcón shows greater hydrological stress, nearing its water-limited threshold.

Factors such as climate variability, rapid urbanization, and limited adaptive capacity affect the water resources of tropical coastal cities. This study evaluates the response of water resources to projected climate variability in Mati City, Davao Oriental, Philippines, using the Soil and Water Assessment Tool (SWAT). Surface runoff, Evapotranspiration (ET), and water yield were simulated by integrating historical climate records (2000–2024) and the downscaled Coupled Model Intercomparison Project Phase 6 (CMIP6)-based projections (2025–2050) from the Philippine Atmospheric, Geophysical, and Astronomical Services Administration (DOST-PAGASA) across seven sub-catchments. During simulations, three climate scenarios were considered: dry, median, and wet. The temperature trend analysis indicates a statistically significant positive trend (+0.004 °C/year) in contrast to non-statistically significant precipitation trends. Across all future scenarios, water yield is projected to decline due to increased ET and reduced recharge—despite a higher runoff under wetter conditions. The dry scenario results in the steepest reductions in water availability. The wet scenario fails to compensate for the present losses. Under the dry scenario, water availability per capita is expected to have decreased below the Falkenmark water stress threshold by the 2040s and to have reached scarcity by 2050, when considering the projected population growth. These findings underscore the necessity of climate-informed water governance, integrated planning, and resilient infrastructure investments to ensure future water security. The study supports Sustainable Development Goals 6 (Clean Water and Sanitation) and 13 (Climate Action) by providing a localized, evidence-based framework for water resource planning under climate change.

Water security assessment in mountainous regions: A new framework for integrating water quality and ecosystem service flows

Water scarcity is an enduring worldwide concern, especially in areas experiencing groundwater depletion, unpredictable rainfall, and lack of access to centralized water infrastructure. Atmospheric Water Generation (AWG) is a promising decentralized option by harvesting moisture straight from surrounding air. This study introduces development, and experimental test of a solar-powered Peltier-assisted Atmospheric Water Recovery System based on dew-point condensation using thermoelectric cooling under different climatic conditions. A systematic review of 30+ state-of-the-art AWG papers identified major challenges in current systems, namely high energy consumption, poor condensation surface efficiency, and low adaptability for off-grid implementation. The suggested prototype combines TEC1-12706 thermoelectric modules, optimized heat sink-fan assemblies, and a sustainable power source to boost water condensation rate with low power loss. Experimental testing was successful in producing water at various temperature–humidity conditions with a maximum yield of ≈15 mL/hour at 28–31°C and 65–75% RH using an enhanced condensation surface. Results confirm the viability of a compact and mobile AWG system for rural, emergency, and water-stressed areas. Additional advancements in thermal management and air–water contact efficiency can facilitate scalable and energy-efficient deployment. This paper adds a sustainable, refrigerant-free, and environment-friendly solution toward SDG-6: Clean Water and Sanitation, solidifying Peltier-based AWG as a potential entry to future water security.

ABSTRACT China’s water security faces unprecedented challenges, examined through the variation in socio-economic development, water resource availability, water-related disasters and aquatic ecosystems to develop a water security philosophy under a changing environment. Guided by the human-water harmony notion, water security needs to balance the human need and natural need, load pressure and carrying capacity, and risk aggregation and mitigation. We propose an integrated water security framework of adaptive socio-economic development patterns, resilient water infrastructure systems and rigorous water governance mechanisms, which manages both human activities and water infrastructure, including natural assets and built projects. Policy recommendations are further proposed for future water security.

Abstract Water scarcity is an escalating environmental challenge, particularly in semi-arid regions like Spain, where balancing human and ecosystem needs is critical for sustainable development. Freshwater ecosystems are vital for biodiversity, water security, and economic systems, but often lose protection during droughts. Spain, largely under a Mediterranean climate, shows strong interdependence between ecological and socioeconomic systems, with agriculture, tourism, and energy sectors heavily reliant on scarce water resources. Spain’s economy has thrived on water-dependent activities yet increasing droughts and infrastructure limits are pushing ecosystems toward collapse, with severe biodiversity loss and irreversible damage. Furthermore, investments aimed at increasing water-use efficiency often backfire, leading to expanded irrigation without real water savings. Climate change, urbanization, and pollution exacerbate these tensions, posing risks to public health and economic stability. Transformative strategies are urgently needed: protecting and restoring ecosystems, promoting conservation agriculture, regulating water-intensive industries, and planning collective responses to illegal water use. Simply increasing supply or reacting to crises without systemic change of water demands will not ensure future water security. Spain’s experience highlights the urgent need for integrated management of natural and human systems to preserve freshwater resources, biodiversity, and economic resilience.

Stakeholder-informed approach improves national modelling of water resources for a Sub-Saharan African basin

ABSTRACT This study investigates the microlevel resilience of surface water resources in microlevel subcatchments within the lower Palar basin (LPB), Tamil Nadu, India, as it experiences shrinking water resources, rising demand with the changing climate. This study employs the Water Evaluation and Planning (WEAP) model to assess LPB's surface water potential and demand, along with projections for future scenarios. Archival data of comprehensive hydrological, climatic, and socioeconomic data for 32 years (1991–2022) are simulated using the WEAP model for understanding the surface water potential and its demand. The future climate scenarios were explored using Shared Socioeconomic Pathways (SSP) 126, 245, 370, and 585 (CMIP6_MPI-ESM1-2-HR), representing low to very high greenhouse gas (GHG) emissions. With a current surface water potential (581 MCM) and demand (310 MCM) for the LPB, the present study provides, for the first time, future water accounting for the region. A hydroclimate simulation study shows high surface water runoff in SSP 585 and lowest in SSP 126 and experiences increasing reduction in surface water resilience, dominated by evapotranspiration (27.5%) during the severe climate scenario. The present study provides insights for policymakers by recommending the capacity augmentation of surface water bodies, ensuring LPB's future water security by increasing water potential and addressing future water demand.

This study projects future Residential Water Use (RWU) under climate change scenarios using a Bayesian Neural Network (BNN) model that quantifies the relationship between observed temperatures and RWU. Eighteen Global Climate Models (GCMs) under the Shared Socioeconomic Pathway 5–8.5 (SSP5–8.5) scenario were used to assess the uncertainties across these models. The findings indicate that RWU in Republic of Korea (ROK) is closely linked to temperature changes, with significant increases projected in the distant future (F3), especially during summer. Under the SSP5–8.5 scenario, RWU is expected to increase by up to 10.3% by the late 21st century (2081–2100) compared to the historical baseline. The model achieved a root mean square error (RMSE) of 11,400 m3/month, demonstrating reliable predictive performance. Unlike conventional deep learning models, the BNN provides probabilistic forecasts with uncertainty bounds, enhancing its suitability for climate-sensitive resource planning. This study also projects inflows to the Paldang Dam, revealing an overall increase in future water availability. However, winter water security may decline due to decreased inflow and minimal changes in RWU. This study suggests enhancing summer precipitation storage while considering downstream flood risks. Demand management strategies are recommended for addressing future winter water security challenges. This research highlights the importance of projecting RWU under climate change scenarios and emphasizes the need for strategic water resource management in ROK.

ABSTRACT This study extends the social license to operate (SLO) concept to the context of purified recycled water (PRW). We developed a novel indicator of SLO to operate a PRW scheme and tested it in Queensland, Australia, drawing on representative samples from surveys conducted in 2017 (N = 1390), 2018 (N = 1400), and 2019 (N = 1401). Based on the pyramid model of SLO we categorised participants into rejectors, marginal acceptors, approvers, and endorsers of PRW. Findings revealed that 60% of participants were approvers or endorsers of PRW in 2019, making it likely they would extend SLO. Rates of approval and endorsement increased over time; rates of rejection and marginal acceptance decreased. Group profiling revealed that water literacy, trust in water management, concern about future water security, valuing water conservation, and conservation intentions during drought consistently distinguished between SLO groups. Interpretations and implications for PRW managers are discussed.

Across the globe, countries grapple with strains on resources and the effects of climate change on the ways populations live. Australia’s fresh water supplies are vulnerable and the nation will continue to experience water security issues. Thus, understanding the perceptions of people to the water security threat will assist in developing effective mitigation strategies. To identify these perceptions, a case study of residents in the coastal city of Townsville in north Queensland, Australia, was undertaken. A total of 299 participants were recruited who completed an online survey that, in line with construal level theory, presented water scenarios as proximal and distal in terms of spatial, temporal, hypothetical and social distances. Results were that distal threats and previous exposure to water-security threats elicited higher individual threat perceptions. This research offers considerations for future water security mitigation strategies that encourage water-saving behaviour, particularly in this region.

Abstract Understanding the long-term hydroclimatic variation in the mountainous region of South Asia (northern Pakistan) is essential for forecasting future water security and environmental changes. In this study, we developed a 586 year regional tree-ring width chronology using standard dendrochronological techniques on Picea smithiana (Wall.) Boiss, samples collected from lower elevations in the Chara and Naltar valleys of Gilgit-Baltistan. Correlation analysis indicates a significant positive relationship between tree growth and summer precipitation as well as the Palmer Drought Severity Index (PDSI) (p < 0.01), while a negative correlation was observed with summer temperatures. We used a linear regression model to reconstruct the summer (June–August) PDSI for the period 1431–2016 CE based on the relationship between regional chronology and climate data. This model accounted for 37.6% of the actual PDSI variation observed during the calibration period from 1956 to 2016 CE. The reconstruction identifies key hydroclimatic events, notably an extended severe drought from 1601 to 1608 (−0.87 ± 0.31), and a prolonged drought interval 1537–1549 (−0.61 ± 0.18). An extreme wet period was recorded in 1522–1533 (0.91 ± 0.32), whereas repeated decadal drought events were observed in the late 18th and early 19th centuries. Spatial correlation analyses demonstrate the impact of large-scale climatic drivers, such as sea surface temperature anomalies in the Indian and Pacific Oceans, and underscore the significance of monsoon variability in determining regional moisture patterns. Our reconstruction, derived from the multitaper spectrum and Morlet wavelet spectrum analysis, exhibited significant periodicities of 47.9, 27, 21.8, and 2–3 years. The three periodicities likely correspond to the Pacific decadal oscillation or the Atlantic multidecadal oscillation, whereas 2–3 cycles is strongly linked to El Niño–Southern Oscillation. Our study illustrates the essential function of tree-ring records in evaluating drought risk and underscores the wider consequences of variations in the climate in the Hindu Kush–Karakoram–Himalaya for millions of downstream populations.

This paper critically examines innovative technologies that can produce high-quality effluent for a variety of beneficial applications, acknowledging the limitations of traditional wastewater treatment methods that are solely focused on environmental protection. In response to the growing global challenge of water scarcity, this study offers a thorough overview of advanced wastewater treatment technologies and their critical role in enabling resource recovery and reuse for future water security. The paper goes into detail about the basic ideas and workings of the primary, secondary, and tertiary stages of wastewater treatment. To minimize initial pollution loads and remove gross solids, the first treatment uses mechanical techniques. Secondary treatment greatly reduces suspended solids and biochemical oxygen demand (BOD) by using biological processes. However, the main emphasis is on the thorough examination of tertiary, or advanced, wastewater treatment methods, which are necessary to produce water fit for reuse in industry, agriculture, and even drinking. Many techniques are tested for their ability to remove particular contaminants such as pathogens, nutrients, heavy metals, and dissolved salts. These techniques include oxidation, precipitation, membrane filtration (RO, NF, micro-, ultra-), adsorption, and advanced oxidation processes (AOPs). Additionally, as sustainable and efficient secondary or tertiary treatment options, the study investigates the integration of biofilm-based reactors (submerged bio-contactors, trickling filters) and natural treatment systems (wetlands). To guarantee the safety of reclaimed water by rendering microorganisms inactive, chemical disinfection techniques are also examined. Important facets of technology selection are discussed, with a focus on taking established water quality standards, planned end-use, and wastewater characteristics into account. When designing suitable treatment trains, factors like cost, energy consumption, operational complexity, efficiency, and dependability are emphasized as crucial determinants. This study concludes by highlighting the critical role that wastewater recycling and reuse play as a tactical way to improve water security, lessen dependency on freshwater supplies, and lessen environmental damage. The various uses and advantages of recycled water are examined within the context of a hierarchical wastewater management strategy that places an emphasis on responsible disposal, treatment for reuse, and pollution prevention. This critical analysis directly compares emerging advanced technologies with conventional methods, highlighting their superior efficacy in resource recovery and reuse. Key findings from our analysis include the elimination of about 85% of BOD and suspended solids by a well-functioning secondary treatment system, and the capacity of reverse osmosis membranes to remove up to 99% of contaminants for high-quality effluent. This analysis highlights the critical role that cutting-edge wastewater treatment technologies play in supporting the shift to a circular water economy and guaranteeing long-term water sustainability in the face of growing global water scarcity.

Chlorination enhances the phthalates release and increases the cytotoxicity and bacterial functions related to human disease of drinking water in plastic pipes.

Projections of water availability in the near future are increasingly worrisome due to climate change. It is, therefore, high time to seek and develop technologies that would guarantee water availability in the future. In this respect, desalination of seawater is one of the most important alternatives, as specific attention needs to be directed at improving the existing techniques of it. This is why updating information about new achievements for researchers is so important in improving such technologies. This comprehensive review article analyzes advancements in seawater desalination through a bibliometric study encompassing 8523 scientific papers published from 1966 to 2023. The analysis identifies eight key research areas, highlighting significant improvements in energy efficiency and membrane technology. The review examines innovative approaches, including the application of nanoparticles and hydrogels, as well as the integration of renewable energy sources. Additionally, it addresses persistent challenges such as biofouling and brine management. A compilation of costs of different technologies of the last decade has been carried out in order to serve as a baseline for future research or technological developments. This study serves as a valuable resource for researchers and policymakers, aiming to promote sustainable water solutions and enhance future water security. By synthesizing decades of research, this review provides a foundation for further advancements in desalination technology and policy development, ultimately contributing to the global effort to secure water resources for future generations

Groundwater is a critical resource for sustaining human activities, particularly in urban areas, where its importance is exaggerated by growing water demands, urban expansion, and industrial activities. Ensuring future water security necessitates an in-depth understanding of groundwater recharge dynamics, which are often complex and influenced by rapid urbanization. The alarming decline in groundwater resources in both urban and rural regions underscore the urgency for advanced groundwater management strategies. However, identifying and evaluating groundwater recharge potential zones (GWPZs) remains a challenge due to the dynamic interplay of hydrogeological and urban development factors. This study employs an integrated approach combining geographic information system (GIS), remote sensing, and multi-criteria decision analysis using the analytical hierarchy process (MCDA-AHP) to delineate GWPZs in the Sulaymaniyah Basin (SB). The methodology is further supported by hydrogeological data and validated through geophysical investigation using electrical resistivity tomography (ERT) data. For the MCDA-AHP, six thematic layers including rainfall, geology, lineament density, slope, drainage density, and land use/land cover were derived from satellite imagery, geological surveys, and well data. These layers were ranked based on their relative influence on groundwater recharge and integrated using GIS-based weighted overlay analysis to generate groundwater potential maps. The results identified three potential zones for groundwater recharge: low (11.26%), moderate (45.51%), and high (43.23%). Validation using ERT data and receiver operating characteristics (ROC) analysis revealed strong agreement, with an area under the curve (AUC) accuracy of 86%. These findings demonstrate the robustness of the integrated approach, providing a reliable tool for minimizing hydrogeophysical exploration costs and reducing the number of unsuccessful boreholes.

Agriculture, being a major consumer of water resources, is crucial for ensuring global food security. Current patterns of water use and agricultural practices, if continued, are projected to cause severe water shortages, particularly in agriculture, by 2054. This water scarcity has already reduced crop cultivation, threatening future food and water security. This study introduces a dynamic system-based model to simulate water resources, focusing on agricultural water consumption and groundwater reclamation from 2025 to 2054. The model evaluates cultivated areas using three indicators: physical productivity, economic productivity, and water consumption. Under projected conditions, significant water shortages and declining underground water levels are anticipated. The most effective scenario involves halting cultivation of water-intensive crops, reducing groundwater withdrawal by 25%, and transferring 250 million cubic meters of water annually. This approach increases surface and underground water levels by 29.5% and 36.5%, respectively, and offsets 65.1% of the water shortage. These results emphasize the urgent need for sustainable water management to address future water scarcity and ensure agricultural and food security. The proposed model serves as a valuable tool for policymakers to design and implement strategies in water-scarce regions.

Abstract Crucial to the assessment of future water security is how the land model component of Earth System Models partition precipitation into evapotranspiration and runoff, and the sensitivity of this partitioning to climate. This sensitivity is not explicitly constrained in land models nor the model parameters important for this sensitivity identified. Here, we seek to understand parametric controls on runoff sensitivity to precipitation and temperature in a state‐of‐the‐science land model, the Community Land Model version 5 (CLM5). Process‐parameter interactions underlying these two climate sensitivities are investigated using the sophisticated variance‐based sensitivity analysis. This analysis focuses on three snow‐dominated basins in the Colorado River headwaters region, a prominent exemplar where land models display a wide disparity in runoff sensitivities. Runoff sensitivities are dominated by indirect or interaction effects between a few parameters of subsurface, snow, and plant processes. A focus on only one kind of parameters would therefore limit the ability to constrain the others. Surface runoff exhibits strong sensitivity to parameters of snow and subsurface processes. Constraining snow simulations would require explicit representation of the spatial variability across large elevation gradients. Subsurface runoff and soil evaporation exhibit very similar sensitivities. Model calibration against the subsurface runoff flux would therefore constrain soil evaporation. The push toward a mechanistic treatment of processes in CLM5 have dampened the sensitivity of parameters compared to earlier model versions. A focus on the sensitive parameters and processes identified here can help characterize and reduce uncertainty in water resource sensitivity to climate change.

ABSTRACT Globally, there is an increasing trade-off between efforts to attain human water security and minimise ecosystem threats. Poorly planned efforts to meet current human water demands may jeopardise the ecological integrity of the river basins and may put future water security at risk. This article assesses the trade-offs between the future human and ecosystem water security threats in the South East Queensland Region, Australia. The article evaluates future water security threats based on a set of water and ecosystem services-related indicators and an ensemble of all climate change scenarios and models on water flow. It predicts the hotspots with higher human water security and ecosystem threats in 2040. The article finds that 52.1 per cent of the region may be affected in 2040 with either higher human water security risk or ecosystem services risk and, in some cases, with both. The challenge of managing the trade-offs is complex in regions with higher economic activities, which cover 16.3 per cent of the region. The research recommends that mitigation measures that address human water provision and nature conservation will need to be balanced and put at the same level of importance in these regions that are more affected.

Abstract Water scarcity is a critical threat in arid regions in China due to dry climate and rising human water demand. The sustainability of a recent wetter trend and its impact on future water security remain uncertain. This case study focuses on a hotspot region, the North Slope of the Tianshan Mountains (NSTM), to assess water scarcity in the coming decades (2030–2050) under two climate scenarios. To this end, we developed an integrated agro‐hydrological model to simulate historical and future hydrological processes and crop water dynamics in arid regions. Our results indicate nonsignificant increases in precipitation (around 3%) and evident rising temperatures (0.9–1.5°C) in the NSTM compared to the present‐day (2011–2020) climate. This translates to a projected increase in water availability (5.6%–11.2%) during 2030–2050, with slightly larger increases (6.3%–14%) in glacier runoff. However, the spatial mismatch between precipitation increases and water demand makes this potential gain largely offset by rising irrigation water demand (over 7%) if cropland remains constant from 2020 onwards. As a result, the current annual water deficit (3.3 km3) is likely to increase by 5%–11%, with 32% of NSTM basins facing persistent water scarcity. Most croplands are at high risk of groundwater depletion and 17%–34% of basins will experience intensified water scarcity. These findings highlight the urgent need for comprehensive water management strategies, including improved irrigation efficiency and exploration of alternative water sources, to ensure water security and sustainable development in arid China facing a changing climate.