Search Results (207)

Traditional reservoir flood control operations in China have long relied on a fixed flood-limited water level (FLWL), which frequently results in the underutilization of water resources during flood seasons. Dynamic FLWL regulation and joint reservoir operation have emerged as core strategies to optimize floodwater resource utilization while ensuring flood control safety. However, these approaches typically treat the flood control storage capacity of individual reservoirs as fixed constraints, failing to consider the potential for reallocating this capacity within a cascade reservoir system. This study explores the concept of “equivalent utilization of flood control storage capacity” among cascade reservoirs. Focusing on the four major reservoirs (Wudongde, Baihetan, Xiluodu, and Xiangjiaba) in the lower reaches of the Jinsha River, a methodology for analyzing the equivalent index of their flood control storage capacity is established. The core of this methodology involves a two-round scheduling simulation under various design flood scenarios. The first round of simulation adheres to standard operating rules, while the second round allows upstream reservoirs to retain additional flood volume—with downstream reservoirs correspondingly reducing their outflow—on the premise that downstream safety targets are satisfied. The equivalent index is defined as the ratio of the reduced storage capacity utilized downstream to the additional storage capacity utilized upstream. Nine design flood scenarios (covering three typical years with 1%, 2%, and 5% exceedance probabilities) for flood control in the Sichuan–Chongqing reach were analyzed, with the tightly coupled Wudongde–Baihetan and Xiluodu–Xiangjiaba reservoir pairs treated as two integrated units. The results indicate that the equivalent indices between these two reservoir groups range from 0.96 to 0.999, demonstrating near-perfect functional interchangeability of their flood control storage capacities for the specified research objective. For practical engineering application, a value of 0.96 is recommended as the lower-bound equivalent index. This study provides a methodological framework and specific index to support the dynamic, coordinated, and more efficient utilization of flood control storage capacity in large-scale cascade reservoir systems. Full article

Nanobubbles (NBs) are emerging as a promising area of research across multiple scientific and industrial domains due to their unique physicochemical characteristics. NBs exhibit distinctive properties compared to normal bubbles, including high internal pressure, a large specific surface area, high interfacial activity, and long-term stability in liquids. Therefore, NBs have gained increasing attention as a novel enhanced oil recovery (EOR) technique, offering potential advantages over traditional gas flooding and chemical flooding. CO₂-NB specifically represents a particularly promising approach as an intersection of EOR and carbon capture, utilization, and storage (CCUS), as CO₂-NB enables hydrocarbon recovery and in situ CO₂ utilization and storage at reservoir conditions. This paper presents a structured comparative discussion of currently identified experimental EOR studies that employ CO₂-NBs. Based on the observations of these experiments, this paper discusses the proposed mechanisms in those experiments or other studies that could scientifically play a role in achieving incremental recovery. The main mechanisms discussed include interfacial tension reduction, wettability alteration, CO₂ transfer from NBs into the oil liquid phase, and suppression of gravity segregation. Other possible contributors discussed in the literature include buoyancy-assisted mobilization, induced shock waves, and drag force reduction. These mechanisms are examined in relation to the distinctive properties of CO₂-NBs, showing how these properties contribute to the occurrence of the proposed mechanisms, showcasing the potential of CO₂-NBs as an emergent EOR–CCUS technology. A preliminary probabilistic assessment was performed to estimate CO₂ storage potential during CO₂-NBs EOR injection. The results suggest that the majority of the injected CO₂ is dissolved in the saturated liquid phase, while the amount of free NBs is negligible, indicating that CO₂-NB injection may provide secure storage through solubility trapping, but with lower storage capacity compared to conventional geological sequestration in saline aquifers. Full article

Small streams exhibit rapid and nonlinear flood responses due to steep slopes, short flow paths, and limited storage capacity, making real-time flood prediction difficult under both computational and data constraints. This study presents a measurement-based flood prediction framework for real-time estimation of flood discharge and depth in small-stream basins. Conventional approaches, such as physically based hydrodynamic models, require detailed boundary conditions and high computational cost, while data-driven models often lack physical interpretability. The proposed framework integrates high-frequency monitoring data from the Small-Stream Smart Monitoring System, short-term rainfall nowcasting from the MAPLE system, and nonlinear regression-based hydraulic relationships within a unified operational structure. Rainfall–discharge nomographs and depth–discharge rating curves were developed using a four-parameter logistic regression model based on long-term observations from 12 small streams in Korea. Additional comparisons with alternative regression forms confirmed the suitability of the 4PL model for representing nonlinear hydrological responses. Forecast rainfall was used to estimate discharge, which was subsequently converted to flood depth through calibrated rating curves. For ungauged reaches, depth–discharge relationships were derived using HEC–RAS-based scenario simulations and the Manning equation to enable spatially continuous prediction along stream networks. Model performance was evaluated using independent validation events, showing mean prediction accuracies of approximately 89% for discharge and 90% for flood depth. The framework reduces computational demand by relying on pre-established relationships while maintaining physically interpretable structures. The results indicate that the proposed approach can support real-time flood prediction in small streams under conditions like those examined in this study, although its applicability to other regions requires site-specific calibration and further validation. Full article

Deep reinforcement learning (DRL) has been increasingly used in reservoir operation, but several key challenges and limitations need further study. This paper developed a novel and optimal reservoir operation model incorporating inflow forecasts based on DRL and the deterministic policy gradient algorithm. A multi-dimensional reward function was derived from the objective functions and constraints, and an optimal scheduling scheme was established with dynamically weighted reward functions. The observed daily flow data and 5-day inflow forecasts of the Three Gorges Reservoir (TGR) during flood seasons (from 10 June to 31 October) from 2010 to 2025 were used to evaluate the model performance and compared with the actual operation results. The results show that, compared with the actual operation, Scheme-1 with dynamic weights increases annual average flood prevention storage capacity by approximately 36.8%, enhances power generation by about 2.86 billion kW·h (≈5.49%), and reduces spillway waste water volume by around 3.33 billion m³. This study demonstrates that the optimal scheduling model can substantially improve the overall efficiency of reservoir operation, and the improvement is even more pronounced when the reward function weights are set dynamically. Full article

Urban flood resilience is an important indicator for measuring a city’s capacity to respond to and recover from flood disasters. However, existing assessments often lack a long-term hydrological baseline. This study establishes the historical water system of Yuan Dadu (1267–1368 CE) as a control scenario to benchmark the flood resilience of modern Beijing. By integrating a historical geographic reconstruction with a hydrological–hydrodynamic simulation and the fuzzy analytic hierarchy process (FAHP), the research quantifies structural differences in resilience profiles between the nature-adapted historical system and the modern engineering-dominated system. The results indicate that Yuan Dadu’s urban flood resilience index (UFRI) is 3.44 and modern Beijing’s is 3.28. Despite modern Beijing’s significant advantage in drainage facility density (0.61 km/km²) and emergency management, the system exhibits a functional substitution failure, where gray infrastructure has failed to fully compensate for a 26% reduction in the unit area storage capacity (from 6.4 to 4.7 × 10⁴ m³/km²) and a 48.4% decline in the water system structural complexity. The findings indicate that, in rapidly urbanized cities on alluvial plains with high impervious coverage, expanding drainage networks alone may be insufficient to offset losses in a natural hydraulic buffering capacity. Accordingly, planning strategies are proposed that integrate distributed micro-storage and restore topological connectivity to recreate system-level hydraulic buffering functions. Full article

In the late stage of oilfield water flooding, the rapid increase in water cut of produced fluids significantly reduces oil well productivity. To tackle the challenge of excessive water production in ultra-high-temperature (150 °C) reservoirs, this study introduces a copolymer (acrylamide/vinylpyrrolidone copolymer, acrylamide/2-acrylanmido-2-methylpropanesulfonic acid copolymer)-based gel system. The gelation performance of copolymers with varying compositions and molecular weights was systematically investigated at 150 °C using gelation visualization codes, mechanical strength tests, microstructural analysis, thermogravimetric analysis (TGA), and nuclear magnetic resonance (NMR) spectroscopy. These approaches provide insights into the thermal and mechanical behavior of the gel under high-temperature conditions. Experimental results show that under optimized conditions—specifically with a vinylpyrrolidone (NVP) content of 30–40% in the copolymer and a copolymer concentration of 1.0 wt%—the gel system exhibited the best performance: a gelation time of 9.5–11 h, storage modulus (G′) of 14.7–16.0 Pa, and stability exceeding 6 months at 150 °C. Moreover, increasing the molecular weight from 1.78 × 10⁶ to 3.82 × 10⁶ shortened the gelation time from 18.5 h to 14 h and raised the gel strength code from F to G. Although higher molecular weight led to a finer microstructure lattice and somewhat lower chemical structure stability, it also reduced the gel’s water-binding capacity compared to lower-molecular-weight analogues. The copolymer gel system developed in this work offers a promising technical solution for improving water flooding efficiency in ultra-high-temperature reservoirs. Full article

As urbanization expands, the loss of pervious surfaces has led to greater stormwater runoff and contributed to an increase in urban flooding—localized flooding in areas not formally designated as flood zones. This study evaluates the potential of decentralized active rainwater harvesting (RWH) to mitigate urban flooding in semi-arid urban environments. A neighborhood in northeast El Paso, Texas, was selected as a pilot site. Using a GIS-HEC-HMS modeling framework, approximately 9000 residential parcels were analyzed to assess rooftop harvesting capacity, runoff potential, and system feasibility under different adoption rates and antecedent moisture conditions. Land cover and building footprints were extracted using supervised machine learning to generate stormwater runoff parameters and catchment areas for rainfall-runoff simulations for storms with return periods ranging from 1 to 50 years. The results indicate that for 1- and 2-year storms, a 25% adoption rate may reduce street runoff by 16–19% from 13.1 to 10.6 × 10³ m³ and from 31 to 26.1 × 10³ m³. Increasing adoption to 50% yields substantially greater reductions of approximately 30–36%. Even higher-magnitude storms (5- and 10-year events) experience measurable decreases in runoff volume, with reductions of 10% for the 5-year storms and up to 10.4% for the 10-year storm at the 25% adoption and 20–22% across the same events at 50% adoption. Overall, the results of this study demonstrate that GIS and HEC-HMS are effective tools for evaluating urban flood mitigation strategies, and that decentralized RWH offers a viable method for reducing flood risk in urbanized settings when adoption levels and storage capacities are considered. Full article

Climate change results in reservoir management challenges, especially in areas with a high risk of drought and flooding. Traditional reservoir rule curves are insufficient for addressing variations in reservoir inflow. This study presents a framework combining GCMs from CMIP6 (ACCESS-CM2, MIROC6, and MPI-ESM1-2-LR) under SSP2-4.5 and SSP5-8.5 scenarios and WEAP, the accuracy of which has been validated for reservoir inflow and storage capacity. This framework is integrated with Hippopotamus Optimization (HO) to develop a resilience reservoir rule curve (RRRC) for the Ubolrat Reservoir for 2024–2055, employing a dual-objective function that emphasizes reducing water shortages and water excess. The results indicate that the RRRC developed via HO is more efficient and suitable than Honeybee Mating Optimization (HBMO) and existing rule curves. When tested with historical inflow data, HO reduced the average water shortage by 50% and the maximum shortage period by 79% compared to the existing rule curve. Under future climate scenarios (SSP2-4.5 and SSP5-8.5), efficiency improved significantly, achieving a water shortage reduction of 95–98% and a shortage period reduction of 83–88%. Additionally, HO demonstrated outstanding efficiency in water excess management, with a 7–11% reduction in average excess water. This potential reflects its adaptability in the context of future variations in hydrological conditions. This crucial finding illustrates that the integrated framework can develop resilient rule curves even under uncertainty. HO integrated with various models can be implemented as an optimal framework with high potential for reservoir operation planning under climate change. The developed methodology can be implemented in other reservoirs to investigate additional factors for the sustainable promotion of water resource resilience. Full article

Low-permeability reservoirs have poor reservoir properties and are difficult to develop by conventional water flooding. CO₂ flooding can significantly improve oil recovery while achieving carbon storage, and is widely recognized as an effective solution for the development of low-permeability oil reservoirs. In order to address the lack of a comparative quantitative analysis of the tradeoff between oil recovery factor, CO₂ storage rate, and total CO₂ storage volume for the main injection modes in low-permeability reservoirs, this study systematically evaluated the performance of CO₂-enhanced oil recovery (EOR) and geological storage under different pressures and injection modes through core flooding experiments. The results indicate that displacement pressure and injection strategy significantly influence the CO₂ flooding performance. Continuous miscible flooding (30 MPa) substantially reduced the displacement pressure differential (maximum 6.1 MPa) and achieved the highest oil recovery (78.96%) and the greatest CO₂ storage capacity (5916 cm³). Miscible WAG flooding effectively delayed gas breakthrough (extended to 1.90 pore volumes), homogenized the displacement front, and yielded the best overall outcome: the highest ultimate oil recovery (83.8%) coupled with the optimal CO₂ storage rate (89.1%). The study further reveals that the pre-breakthrough stage is critical for contributing to oil recovery and achieving efficient storage, regardless of the injection modes. These findings clarify the technical characteristics and applicable conditions of different injection modes, providing crucial theoretical insights and practical guidance for optimizing CO₂ EOR and storage projects in low-permeability reservoirs. Full article

Storage-oriented reservoir schemes are effective for large-scale hydrological modeling, yet two important limitations remain. First, although some reservoirs seasonally adjust flood storage capacity (FSC), no global study has examined whether constant or seasonally varying FSC performs better. Second, these schemes rely on empirical operational-zone parameterization, but its impact on simulation accuracy has never been systematically assessed. This study presents an open-source Python module integrating three leading storage-oriented schemes (S25, Z17, H22) with both constant and seasonally varying FSC options. Evaluated using daily observations from 289 global reservoirs via Nash-Sutcliffe Efficiency (NSE), constant FSC significantly outperforms seasonal variation, increasing median outflow NSE by 0.18–0.47 and reducing storage error magnitude by 38–61%, and is selected as optimal for 84% of reservoirs. Sensitivity analysis across eight alternative zoning schemes shows that, under constant FSC, outflow remains stable, whereas seasonal FSC sharply increases sensitivity. Storage simulation is more sensitive overall, yet constant FSC consistently yields the smallest errors. This work provides the first global comparison of FSC strategies and the first systematic assessment of operational zone parameter uncertainty. It strongly recommends constant FSC with H22 or S25 as the default for large-scale modeling. The released module offers a flexible, reproducible platform for the community. Future extensions may incorporate demand-driven rules and hybrid calibration to further improve performance in data-rich regions. Full article

In Mediterranean climate regions, water scarcity, seasonal droughts and hydrological extremes are exacerbated by climate change. In these areas, small dams are increasingly used as decentralized water infrastructure for water supply, especially in agricultural areas. However, several challenges must overcome when planning and managing small reservoirs. This review combines evidence from case studies to analyze the benefits and challenges of small dams. The findings show that small reservoirs may offer a wide array of ecological, agricultural, hydrological, and socio-economic benefits when strategically planned and properly maintained, providing water and contributing to groundwater recharge, vegetative restoration, and biodiversity conservation, while simultaneously controlling flash floods in a cost-effective and participatory manner. On the other hand, evaporation losses and sedimentation may affect water quality and reduce storage capacity. In addition, small dams may negatively affect river ecosystems. Persistent disturbance of downstream flow and sediment regime contributes to altered river morphology and habitat, with effects on biota, and may reduce river system resilience. These impacts are context-dependent, influenced by dam density, geomorphic setting, and climate. Finally, this study highlighted the importance of governance and maintenance practices. Polycentric and participative systems may promote more adaptable responses to water stress, whereas fragmented institutions exacerbate trade-offs between water supply and ecological integrity. Full article

In response to the requirements of wellbore plugging and lost circulation control, this study designed and prepared a new type of thixotropic polymer gel system. The optimal formula was obtained through systematic screening of the types and concentrations of high molecular polymers, cross-linking agents, flow pattern regulators, and resin curing agents. Comprehensive characterization of the gel’s gelling performance, thixotropic properties, high-temperature stability, shear resistance, and plugging capacity was conducted using methods such as the Sydansk bottle test, rheological testing, high-temperature aging experiments, plugging performance evaluation, as well as infrared spectroscopy, nuclear magnetic resonance, and thermogravimetric analysis, and its mechanism of action was revealed. The results show that the optimal formula is 1.2% AM-AA-AMPS terpolymer + 0.5% hydroquinone + 0.6% S-Trioxane + 0.8% modified montmorillonite + 14% modified phenolic resin. This gel system has a gelling time of 6 h, a gel strength reaching grade H, and a storage modulus of 62 Pa. It exhibits significant shear thinning characteristics in the shear rate range of 0.1~1000 s⁻¹, with a viscosity recovery rate of 97.7% and a thixotropic recovery rate of 90% after shearing. It forms a complete gel at a high temperature of 160 °C, with a dehydration rate of only 8.5% and a storage modulus retention rate of 80% after aging at 140 °C for 7 days. Under water flooding conditions at 120 °C, the converted pressure-bearing capacity per 100 m reaches 24.0 MPa. Mechanism analysis confirms that the system forms a stable composite network through the synergistic effect of “covalent cross-linking—hydrogen bonding—physical adsorption”, providing a high-performance material solution for wellbore plugging in high-temperature and high-salt environments. Full article

This study investigates the morphometric and anthropogenic controls governing the occurrence and spatial distribution of tributary–junction fans (TJFs) along the Chaudière River, Québec, Canada. Using GIS-based morphometric analysis, field validation, and multivariate statistics (PCA, CART, LDA), 142 tributary watersheds were analyzed, of which 41 display fan-shaped depositional features. Basin relief, drainage density, contributing area, and slope–area coupling emerge as the dominant predictors of TJF development, delineating an intermediate energy domain where sediment supply and transport capacity become balanced enough to allow partial geomorphic coupling at confluence nodes. CART analysis identified approximate slope and area thresholds (slope < 9°, area > 20 km²; 66% accuracy), while LDA achieved 76%, indicating that morphometry provides useful but incomplete predictive power. These moderate performances reflect the additional influence of event-scale hydrological forcing and unquantified Quaternary substrate heterogeneity typical of postglacial terrain. Beyond morphometry, anthropogenic disturbance exerts a secondary but context-dependent influence, with moderately disturbed watersheds (10–50% altered) showing higher frequencies of fans than both highly engineered (>50%) and minimally disturbed (<10%). This pattern suggests that land-use modification can locally reinforce or offset morphometric predisposition by altering sediment-routing pathways. Overall, TJFs function as localized sediment-storage buffers that may be periodically reactivated during high-magnitude floods. The combined effects of basin geometry, land-use pressures, and hydroclimatic variability explain their spatial distribution. The study provides an indicative, process-informed framework for evaluating sediment connectivity and depositional thresholds in cold-region fluvial systems, with implications for geomorphic interpretation and hazard management. Full article

Flooding poses significant risks to urban areas, especially in regions vulnerable to climate change, where developing countries are disproportionately affected. Compared to rural areas, urban zones are more severely impacted by natural disasters, particularly flooding. The influence of surface cover types on runoff and flood risk is examined in two different neighborhoods of Erbil, Kurdistan Region of Iraq, one representing a newly developed area and the other an older established neighborhood. A newly developed area is compared with an older quarter to assess how different surface compositions impervious versus permeable affect hydrological responses and flood generation. The Soil Conservation Service Curve Number (SCS-CN) method was employed to estimate runoff under varying rainfall scenarios. The findings demonstrate that the implementation of impervious surfaces results in an approximately twofold increase in runoff generation during rainfall events, primarily due to the substantial reduction in infiltration and surface storage capacity. The study also highlights the potential of household-level rainwater harvesting and the redevelopment of low-density neighborhoods with multi-story buildings as effective strategies to reduce runoff and enhance urban resilience. These findings underscore the importance of integrating permeable materials, green infrastructure, and water harvesting measures into urban planning. The research offers valuable insights for urban planners, policymakers, and developers aiming to reduce flood risks in rapidly urbanizing areas, particularly in cities like Erbil that face the dual challenges of urban expansion and climate change. Full article

The Jing River–Dongting Lake (DTL), a critical river–lake complex system in the Middle Yangtze River, China, plays a vital role in flood regulation and ecological sustainability. Recent decades have experienced significant morphology adjustments due to upstream reservoir operations; however, the long-term high-resolution hydro-morphodynamic evolution and its impacts on river–lake interactions remain insufficiently quantified. To address this gap, a two-dimensional hydro-morphodynamic model based on HEC-RAS was employed to simulate three decades of hydro-morphology evolution under projected flow–sediment conditions. The model was validated against observed data and reproduced erosion–deposition trends consistent with previous numerical studies. The results indicate sustained channel incision in the Jing River, with a cumulative erosion volume of 462 million m³, in contrast to net deposition in the DTL area totaling 276 million m³ over three decades. A comparison of results under a sediment reduction regulation shows that the overall spatial pattern of erosion and deposition remains largely consistent, although local areas, particularly the confluence of the three major inlets feeding the lake, exhibit pronounced sensitivity to sediment variations. Furthermore, continuous mainstream incision intensifies a draining effect on the lake during dry seasons, leading to declines in both water levels and surface area in the DTL. This effect is most pronounced in the eastern lake area, with reductions being markedly greater in dry periods than in wet periods. Finally, the lake’s storage capacity progressively decreases, with an average annual loss of approximately 36.5 million m³ in the wet periods, underscoring significant impairment of its flood-regulation function. This study provides a validated modeling framework and critical insights for predicting morphological evolution and informing adaptive management in large river–lake systems. Full article