[Objective] Global warming has exacerbated extreme climate events and their compound hazards, causing increasingly severe impacts on both ecological environments and socioeconomic systems. [Methods] Based on daily meteorological observations from the Yangtze River Basin from 1961 to 2022, the percentile threshold method was used to identify extreme climate events, and four major types of compound extreme climate events were constructed from both temporal and spatial dimensions. The spatiotemporal distribution and evolution characteristics of compound events in the Yangtze River Basin were systematically analyzed. [Results] (1) The spatial distribution of the frequency and annual average duration of compound heatwave-drought events in the Yangtze River Basin generally exhibited a pattern of “low in the upstream source area and high in most parts of the middle-lower reaches”. The annual average frequency of regional heatwave-drought events was 1.8-1.9 times, the average duration per single event was 9.6-9.9 days, and the longest duration was 53-59 days. Both the frequency and duration of these regional heatwave-drought events showed an increasing trend over the past 62 years, with a more significant increase in the upstream. (2) The spatial distribution of the frequency of drought-flood abrupt alternation events in the Yangtze River Basin was characterized by “low in the upper reaches and high in the middle-lower reaches”. The frequency was approximately three events per decade in the upper reaches and six events per decade in the middle-lower reaches. Over the past 62 years, the occurrence frequency has exhibited a slight increasing trend, with the growth rate in the middle-lower reaches being twice that of the upper reaches. (3) The spatial distribution of the frequency of compound flood-heatwave events in the Yangtze River Basin exhibited a pattern of “low in the upstream source area and high in most parts of the middle-lower reaches”. The frequency was approximately five events per decade in the upper reaches and seven events per decade in the middle-lower reaches. Over the past 62 years, it has shown a significant increasing trend. (4) Compound flood events involving both the upper and middle-lower reaches of the Yangtze River occurred every year, with an annual average frequency and duration of 3.7 times and 25 days, respectively. These events exhibited a fluctuating increasing trend over the past 62 years. [Conclusion] Overall, in the context of climate change, compound extreme climate events in the Yangtze River Basin show a significant increasing trend. The intensification of temperature-related extreme events is more pronounced in the upper reaches, while the intensification of precipitation-related extreme events is more prominent in the middle-lower reaches. Since the beginning of the 21st century, the extremeness of various compound events has increased significantly.

[Objective] High-precision, large-scale identification of crop growth stages in irrigation areas has long been one of the core demands for the development of smart agriculture. Based on Sentinel-2 satellite imagery data, this study systematically analyzes the effectiveness of spectral reflectance and vegetation index (VI) curves for identifying different growth stages of winter wheat, and proposes a remote sensing identification method for winter wheat growth stages that integrates multi-spectral features with ensemble learning. [Methods] Using a feature selection + heterogeneous ensemble learning approach, 83 Sentinel-2 Level-2A images were collected, covering all 9 growth stages of winter wheat (emergence, tillering, overwintering, regreening, jointing, booting, heading, grain filling, and maturity). The reflectance patterns of 12 original Sentinel-2 bands and 8 vegetation indices (NDVI, EVI, RECI, NDRE, GCI, LSWI, MASVI, GNDVI) across all growth stages of winter wheat were systematically analyzed. Recursive feature elimination combined with the XGBClassifier was applied to select key feature parameters. A Stacking ensemble architecture was used to heterogeneously integrate five different types of machine learning models—support vector machine (SVM), random forest (RF), extremely randomized trees (ERT), backpropagation neural network (BPNN), and k-nearest neighbors (KNN)—for the identification of winter wheat growth stages. [Results] The 13 feature parameters retained by recursive feature elimination were NDVI, LSWI, GCI, NDRE, EVI, B₅, B₉, B₁₂, B₁, B₇, B_8a, B₁₁, and B₄. Analysis of the selected parameters showed that NDRE, B₅, and B₇ were all related to the red-edge bands, confirming the unique advantage of red-edge bands in capturing key physiological changes of winter wheat (such as chlorophyll content and leaf structure). Furthermore, the overall importance of vegetation indices was significantly higher than that of original spectral bands, highlighting that vegetation indices derived from multi-band combinations could more effectively characterize changes in crop physiological status and reduce background interference. After accuracy validation, it was found that all six models achieved relatively high remote sensing classification accuracy for the growth stages of winter wheat, with overall accuracy exceeding 0.907 5, and Kappa coefficient and F1-Score above 0.891 6. Additionally, significant changes in spectral reflectance and vegetation indices were observed in the winter wheat canopy during certain growth stages, providing a crucial basis for distinguishing key growth stages. [Conclusions] (1) Significant differences are observed in the spectral reflectance and vegetation index values across different growth stages of winter wheat. Furthermore, the spectral reflectance curve of the winter wheat canopy shows completely opposite trends in the visible and near-infrared bands. The vegetation index curves generally exhibit consistent trends throughout all growth stages of winter wheat, but numerical differences between the curves are significant during specific stages. (2) Red-edge bands can effectively improve the accuracy of identification models for winter wheat growth stages. Compared to using spectral reflectance alone, vegetation indices are more effective in identifying different growth stages. (3) The identification model constructed using the Stacking ensemble achieves significantly higher accuracy than the other models and is suitable for research on growth stage identification. The overall model accuracy ranks as follows: stacking ensemble model>random forest model>extremely randomized trees model>k-nearest neighbors model>backpropagation neural network model>support vector machine model.

[Objective] The aim of this study is to address the issue of stability control of surrounding rocks during the construction of underground oil storage caverns. [Methods] We first clarified the types and manifestations of surrounding rock instability in caverns, and then applied the block theory to analyze the issues of block identification and stability caused by unfavorable combinations of structural planes. The key blocks identified during construction period were classified based on their geometric shapes, and key blocks requiring support were selected according to their morphological types. Subsequently, we focused on the identification of hazard-causing blocks during construction to analyze key issues such as the identification of cross-layer blocks (which only become fully exposed after multi-layer excavation in high-sidewall caverns), instability characteristics of surrounding rocks involving along-cavern joints, and potential instability risks at the intersections of caverns. [Results] Using block theory to determine whether different combinations of structural planes could form key blocks, followed by stability and support analysis, serves as a necessary supplement to the conventional approach relying on surrounding rock quality classification for support design. The geometric shapes of blocks were classified into three types: “regular-shaped”, “flat and shallow-buried”, and “sharp and deeply embedded”, with the “regular-shaped” blocks being the primary type requiring support. “Flat and shallow-buried” blocks were prone to spontaneous falling, “sharp and deeply embedded” blocks were less likely to become unstable, and “regular-shaped” blocks required support, thereby providing a basis for differentiated support during the construction period. Based on the distribution characteristics of blocks during the construction period, the key issues of the identification and control of hazard-causing blocks were summarized as follows: (1) cross-layer blocks were the main hazard sources during the construction of high-sidewall caverns. It was necessary to splice and compare geological sketches obtained from multiple excavation layers to analyze the cross-layer extension characteristics and intersections of structural planes to determine whether cross-layer blocks may form. (2) Along-cavern joints, due to their limited visible exposure and “concealed” characteristics, were prone to form collapse blocks when intersecting with other structural planes in hard rock sections, while in medium to soft rock sections, they may cause large-scale sliding instability. (3) At cavern intersections, the increase in free surfaces, along with fewer structural plane cuts, may still result in the formation of hazard-causing blocks, thereby increasing safety risks. [Conclusion] The findings advance the understanding of block identification and stability analysis during the construction of underground caverns. The proposed classification of block shapes and the summarized key issues in recognizing hazard-causing blocks can provide a reference for the stability control of surrounding rocks in similar cavern engineering projects.

[Objective] This study focuses on morphodynamic evolution of braided rivers in the Source Region of the Yangtze River (SRYR), a representative high-altitude fluvial system on the Qinghai-Xizang Plateau. It aims to 1) systematically review recent advances in remote sensing monitoring, quantitative morphological characterization, and numerical simulation; 2) establish a unified morphological representation framework applicable across spatial scales; 3) analyze the response mechanisms of braided rivers to variations in water and sediment under climate change; 4) identify key process mechanisms and influencing factors to support the sustainable management and ecological protection of braided river systems on the plateau. [Methods] This study integrated multiple research approaches, including the extraction of morphological parameters at various scales from remote sensing imagery, UAV-based photogrammetry, and field surveys. Numerical models such as Delft3D were used to simulate morphological evolution under typical flood scenarios. A three-tier morphological representation system comprising whole-reach, sub-reach, and bar-channel unit levels was constructed. Indicators such as braiding intensity, channel density, and bar-to-channel area ratio were analyzed across different scales. Through literature review and empirical comparison, the climatic, hydrological, and geomorphic factors affecting the evolution of braided rivers on the Qinghai-Xizang Plateau were identified, and their evolutionary patterns were summarized. [Results] In recent years, research on the morphodynamics of braided rivers in the SRYR has made systematic progress. The focus has shifted from qualitative descriptions to quantitative analyses, covering spatial scales from bar-channel units to entire river reaches and temporal scales from individual flood events to interannual evolution. In terms of morphological characterization, a multi-scale index system incorporating indicators such as braiding intensity, channel density, and bar-to-channel area ratio has been developed, achieving a preliminary quantitative description of structural complexity. Regarding process mechanisms, explanatory frameworks such as “oblique bar cutting”,“dual driving by flow and sediment”, and “tectonic-geomorphic coupling” have been proposed. Concerning climatic responses, three typical response modes have been identified: Sediment-Increase Dominated Pattern, Water-Increase Dominated Pattern, and Sediment-Increase Constrained Pattern, which exhibit significant spatial differentiation. Methodologically, the integration of remote sensing, UAV photogrammetry, and numerical modeling has significantly improved the precision of fluvial dynamic process recognition. Despite these advancements, three major challenges remain: (1) the multi-scale quantitative characterization system lacks uniformity and transferability. Morphological parameters across different scales remain poorly integrated, and the coupling mechanism between bar-channel structures and overall stability has not been clearly understood. Existing indices, mostly derived from lowland alluvial river systems, are difficult to directly apply in high-altitude cold environments. Quantitative descriptions of three-dimensional riverbed structures remain inadequate, and topological network characteristics and flow direction information have not been systematically incorporated.(2) There is insufficient understanding of spatiotemporal response mechanisms, making cross-scale modeling difficult. A unified framework is still lacking to explain morphological evolution driven by both short-term flood events and long-term climate change. The absence of high-temporal-resolution data across multiple spatial scales hampers the parameterization and validation of dynamic evolution models, resulting in difficulties in scale conversion.(3) The bidirectional effects of climate change remain unclear. In the short term, glacier melt and permafrost degradation increase water and sediment fluxes, promoting the enhancement of braided structures. However, future glacier retreat may reverse the water and sediment processes, causing channel incision and transition toward single-thread morphology. There is currently no systematic method to predict the overall impacts of such bidirectional changes on braided river morphology, and research on threshold identification and irreversible responses remains lacking. [Conclusions] Overall, future research on braided rivers urgently needs to shift from qualitative understanding to quantitative prediction. An integrated research framework that combines process analysis, threshold identification, and evolutionary trend modeling should be established. By combining multi-source data and multi-scale models, this framework can provide scientific support for infrastructure planning and ecological conservation on the Qinghai-Xizang Plateau.

[Objective] This study reveals the epistemological rationale underlying George Gabriel Stokes’ cautious and reserved stance in his review of Osborne Reynolds’ groundbreaking 1895 paper proposing the Reynolds-Averaged Navier-Stokes (RANS) equations. While Reynolds’ methodology has become a cornerstone of turbulence modeling in engineering practices, Stokes—co-developer of the Navier-Stokes (N-S) equations—notably refrained from offering an endorsement during its first-round review. Through an interdisciplinary investigation combining archival analysis, theoretical fluid dynamics, and philosophy of science, it is revealed that Stokes’ reservations stemmed not from technical negligence but from a profound understanding of the N-S equations’ physical completeness and the inherent epistemological limitations of turbulence closure models. [Methods] Three complementary approaches were employed: 1. Fundamental theory reconstruction: the N-S equations were reconstructed based on Stokes’ original axiomatic framework — Newton’s law of viscosity, the assumption of stress isotropy, and the law of mass conservation — confirming their physical completeness. However, introducing additional independent laws to close the unclosed terms derived from Reynolds averaging procedure would fracture the physical completeness of the N-S equations. 2. Theoretical framework comparison: Stokes’ derivation of viscous stress based on physical laws was juxtaposed with Reynolds’ empirical stress closure schemes, revealing a fundamental epistemological asymmetry between the physical law-based N-S equations and phenomenologically approximation methods. 3. Modern computational validation: Contemporary Direct Numerical Simulation (DNS) demonstrated that turbulent dynamics could naturally emerge from N-S equation solutions without auxiliary models, confirming Stokes’ intuition about the equations’ inherent prediction capability. [Results] 1. Closure paradox: unlike the viscous stress governed by Newtonian mechanics in the N-S equations, Reynolds stress lacks a definitive physical closure law. Any imposed closure model constitutes a departure from the N-S framework’s physical completeness. 2. Epistemological boundaries: Turbulence models essentially belong to engineering phenomenology rather than fundamental physics, with parameters relying on calibration and validation against domain-specific observational data rather than universal principles. 3. Computational confirmation: DNS technology validates Stokes’ foresight that turbulence is an inherent property of the Navier-Stokes equations, demonstrating that vortex dynamics and flow transition are natural solutions rather than modeling artifacts. [Conclusion] Stokes’ reserved position reflects a form of prescient scientific conservatism, recognizing that although RANS models have engineering utility, their operation has exceeded the epistemological boundary of first-principles physics. The physical completeness of the N-S equations essentially excludes the possibility of establishing an independent closure law for Reynolds stress, making turbulence models inherently approximate and limited in application. This study bridges historical insights with contemporary controversies in turbulence modeling, demonstrating that mathematical parameterization cannot compensate for the absence of physical laws. While RANS remains indispensable in engineering analysis, Stokes’ implicit critique continues to highlight the unresolved fundamental challenges in fluid mechanics.

The construction of happy rivers and lakes is a significant initiative to expedite ecological civilization construction and a crucial task for the river-lake chief system at present and in the future. Taking the construction of a happy river and lake project in Zhongqu, Tibet as a case study, we outline 15 key tasks of the Zhongqu project from three aspects: river system governance, improvement of river management capacity, and support for the development of the watershed region. Subsequently, in comparison with the work plan for evaluating the effectiveness of happy-river-and-lake construction, we analyze the effectiveness of the Zhongqu project from seven perspectives: safety, ecology, livability, intelligence, culture, development, and public satisfaction. Given the unique geographical location, climatic conditions, topography, ecological environment, and cultural customs in the Zhongqu watershed, we discuss the challenges and propose corresponding solutions and suggestions. The pilot exploration of constructing happy-river-and-lake project for the Zhongqu River offers a theoretical foundation and technical reference for similar projects on the plateau.

The changing environment alters river water quantity. Scientifically clarifying the change trend of water quantity is fundamental for water resources management in river basins. This paper focuses on 23 rivers for water allocation in the Yangtze River Basin. Utilizing measured runoff data, we analyzed the annual and monthly flow trends of major rivers and the change trends of outbound flow across different provinces within the basin. Results indicate that since 2012, the annual water volume of rivers for water allocation in the Yangtze River Basin has remained stable with an upward trend in 2020, followed by a significant shift from wet period to moderately dry period. The monthly runoff of each river exhibited an obvious unimodal pattern, yet the annual water volume gradually concentrated towards non-flood season. The outbound water volume across provinces in the basin showed multiple alternations between dry and wet seasons, generally presenting a fluctuating upward trend that peaked in 2020. After that, the outbound water volume across provinces continuously declined to the present state. The annual overall compliance rate of Guizhou and Hunan showed a downward trend, while Hubei followed behind.

Confined concrete box steel arch is a composite arch structure comprising box steel and core concrete. It is a novel support form designed to effectively control deformation in soft rock tunnels. Currently, there is limited research on the bearing characteristics of this arch type. In view of this, a compression-bending yield criterion for confined concrete box section is deduced, and the ultimate bearing capacities for strength and structural stability are analyzed respectively. Furthermore, the bearing characteristics of three arch types: confined concrete box steel arch, H-type steel arch, and box steel arch, are compared. Results indicate that the yield criterion value for the confined concrete box steel arch section is the highest among the types considered. Specifically, its axial compression yield limit is 1.4 times that of the box type and 2.2 times that of the H-type. Moreover, the pure bending yield limit is 1.1 times that of the box type and 1.5 times that of the H-type. The strength and ultimate bearing capacity of confined concrete box steel arch surpass those of the box type and H-type steel arches. The ultimate bearing capacity for strength is 1.3-1.4 times that of the box steel arch and 2.2-2.3 times that of the H-type steel arch. The ultimate bearing capacity for structural stability is 1.03-1.04 times that of the box steel arch and 1.10-1.27 times that of the H-type steel arch. Consequently, the confined concrete box steel arch exhibits significant advantages in load-bearing characteristics and can provide reliable and efficient support in soft rock tunnels.

Under intense human interference and extreme climate events, the flow-sediment regimes, deposition and erosion patterns, and river-lake interactions in the middle and lower reaches of the Yangtze River have undergone significant transformations. After the impoundment of the Three Gorges Project, the annual upstream sediment supply to the middle and lower Yangtze River has decreased by 70% to 93%, and the flow process has become more concentrated. However, the post-flood recession has accelerated due to the operation of cascade hydropower stations. The annual water supply from the four rivers and three outlets flowing into the Dongting Lake has shown no significant adjustments, with a decline of 9%, while the annual sediment supply has decreased significantly by 38%. The annual water and sediment supply of the five rivers into the Poyang Lake have decreased by 2% and 57%, respectively, while the annual water and sediment outflow from the Poyang Lake have increased by 1% and 5%, respectively. These adjustments have altered the deposition and erosion patterns in the middle and lower Yangtze River. To be specific, from 2003 to 2021, the cumulative erosion of the mainstream reached 5.03 billion m³, with an average annual erosion of 265 million m³per year. The deposition-erosion state of the Dongting Lake has shifted from being deposition-dominated to slight erosion-dominated, and the riverbed of the three outlets generally exhibits an erosion trend. Similarly, the deposition-erosion state of the Poyang Lake has changed from deposition to erosion, and the channel connecting the Poyang Lake to the mainstream Yangtze River shows severe erosion and down-cutting. A predictive model indicates that over the next three decades, the mainstream of the middle and lower Yangtze River will continue to experience significant erosion. By the end of 2050, the cumulative total erosion of the mainstream from Yichang to Datong and the three outlets will be 3.58 billion m³ and 117 million m³, respectively. The Dongting Lake is expected to be slightly silted, while the Poyang Lake area will be slightly eroded. Based on these findings, the impacts of the river-lake evolution on flood control, water supply, navigation, ecology, and safety of water-related structures are expounded systematically. Countermeasures and suggestions are also put forward.

Under the surging trend of the digital age, various industries are accelerating the construction and innovation of new quality productivity. The Ministry of Water Resources has put forward more stringent and forward-looking requirements for the construction of digital twin watersheds and digital twin hydrology. In response to the many challenges faced by current hydrological work, in-depth analysis has found that there are still significant gaps in the layout of station networks in some areas. The integration and application capabilities of intelligent perception technology urgently need to be strengthened, the intelligent transformation of professional algorithms still needs to be deepened, and the construction of the full business chain application system is not yet perfect. Based on the long-term research accumulation and practical experience of the Yangtze River Commission Hydrological Bureau, this article proposes a series of targeted strategies: 1)By continuously optimizing the station network layout and upgrading facilities and equipment, a more comprehensive and efficient station network system can be constructed. 2)By implementing the “one policy for one station” strategy, we will focus on improving hydrological measurement and reporting capabilities, and actively explore cutting-edge technologies such as quantum dot spectroscopy for sand measurement, to create a highly integrated intelligent perception system.3)By conducting research on intelligent flow prediction algorithms, low dry flow measurement algorithms, and hydrological models, an intelligent algorithm cluster is constructed.4)By developing the Yangtze River Smart Hydrological Monitoring and Management System and the Hydrological Data Online Compilation System, we have built a WISH application system that covers the entire business chain. The series of hydrological intelligent perception technology research and equipment development strategies proposed in this article will provide strong support and promotion for accelerating the development of new quality productivity in the hydrological field.

Developing new quality productive forces in water conservancy field is both an intrinsic requirement and a key focus for implementing the national “river strategy”. It addresses both current and emerging water problems, enhances basin safety and protection, and promotes high-quality economic and social development. In view of the main features and challenges in the new stage of governing and protecting the Yangtze River, we explore the pathways and principles of forming new quality productive forces covering scientific and technological innovations in ecological water conservancy, digitization and intelligence of production elements, and the green transformation and upgrading of industries. Furthermore, we propose to strengthen natural-based water engineering, digital twins, water conservation, pollution and carbon emission reduction, as well as watershed management modernization to advance the ecological, intelligent, green and modernized development of the Yangtze River.

The distribution and magnitude of earth pressure behind wall is the key basis for the design of assembled retaining wall. We investigated the displacement patterns and soil pressure distribution of retaining walls under loading conditions via designing and conducting field tests of a new type of assembled concrete retaining wall. Based on the field tests, we established the theoretical computational model of retaining wall with sloping and rough wall backs yet with no cohesive fill. In consideration of factors such as displacement pattern and magnitude, soil arching effect, and interlayer shear stress, we adopted the horizontal layer analysis method to derive an earth pressure formula for retaining wall rotating around the base (RB), defined as an RB displacement mode.Results indicate a sound overall performance of the retaining wall, rigidly rotating around the base. Under the RB mode, soils at the top of the wall reach the active limit state first, progressively followed by lower depths. Limit state will be reached when soil displacement S_c reaches 7 mm at any depth, corresponding to S_c=0.16%H(H is the wall height). The theoretical value closely matches test value, demonstrating the applicability of our derived formula in predicting the distribution and magnitude of earth pressure during the retaining wall’s rotation around the base. Furthermore, as the rotation intensifies, the concavity of the earth pressure distribution curve becomes more pronounced, and the height of the resultant soil pressure force point initially decreases and then recovers. A rotation angle η=0.007 rad is identified as the critical threshold for the retaining wall to reach its active limit state.

The scheduling for sediment discharge from the Three Gorges Reservoir (TGR) is a crucial technical issue influencing its safe operation and overall benefits. Based on long time series measured water and sediment data and reservoir operations, we expound the water and sediment characteristics in TGR during flood season, the sediment peak forecasting techniques and sediment reduction scheduling strategies in practice. Results indicate that after 2012, the flood season runoff in TGR constituted 45% of the annual total runoff, while sediment transport during this period reaching 84%. The proportion of sediment transport during each flood event notably increased, highlighting an asynchronous pattern between water and sediment transport. Leveraging real-time monitoring data, we built a sediment forecasting system integrating multi-form boundary prediction model and reservoir water-sediment transport model. This system forecasts the time of sediment peak arriving dam and the corresponding sediment load, offering technical support for sediment reduction dispatch during flood season. Successful operational tests of sediment peak discharge in TGR have yielded expected outcomes, significantly increasing sediment discharge ratios within the reservoir. During each flood event, sediment discharge ratios ranged from approximately 27% to 39%.

The Three Gorges Project has operated for 20 years since 2003, achieving all major design objectives while continuously optimizing operational strategies to suit changing conditions and developmental needs. Its multifaceted benefits in flood control, power generation, navigation, and water resource utilization have been fully realized. By the end of 2023, the project has executed 66 flood detention operations, retaining an accumulated flood of over 208.8 billion m³, ensuring flood safety for Jingjiang River and substantially easing pressure on flood protection in the middle and lower reaches of Yangtze River. Power generation has surpassed 1 660 billion kW·h, equivalent to saving 510 million tons of standard coal and reducing carbon dioxide emissions by 1.33 billion tons. Channel conditions have markedly improved, facilitating a freight volume exceeding 2 billion tons, thus catalyzing the rapid development of Yangtze River navigation. During dry seasons, approximately 340 billion m³ of water was replenished downstream, effectively securing water supply safety. Ecological operations have yielded significant results, notably in the restoration of four major Chinese carps. To address challenges posed by frequent extreme hydrological events and ensure the long-term safe operation of the Three Gorges Project, as well as maximize its comprehensive benefits, future prospects entail advancing meteorological and hydrological forecasting technologies, optimizing the reservoir’s operational schemes, leveraging and applying innovative achievements, and implementing intelligent management practices.

After seven decades of construction, the Yangtze River basin’s control reservoir group has reached completion. The joint operation of cascade reservoirs, with the Three Gorges reservoir as its core, has been ongoing for ten years. This study presents an analysis of the achievements, challenges, and solutions stemming from this joint operation in flood control, water supply, ecology, and emergency response. The findings underscore the pivotal role played by joint reservoir group operation in flood control, drought relief, water supply, ecological preservation, and emergency management. The main challenges identified are climate change and the uncertainties in medium- to long-term hydrological forecasts. Additionally, management issues such as coordinating interests between joint reservoir group operations and single reservoir multi-objective operations, quantifying operational effectiveness, and devising fair compensation mechanisms are also significant hurdles. The primary solution proposed involves strengthening the “Four Preemptive” system, namely, forecasting, early warning, contingency planning, and rehearsal, to address climate change uncertainties and human activities’ impacts. Furthermore, enhancing joint reservoir and water network operations can significantly bolster water security of hydraulic projects. Establishing a scientifically sound and equitable joint operation system and mechanism for water project groups emerges as a crucial and effective measure.

Changes of glacier in the source region of Changjiang (also known as Yangtze) River reveal the climate change trends in the Qinghai-Xizang (Tibetan) Plateau. Subglacial topography is crucial for understanding glacier development and movement processes, and is, furthermore, of guiding importance for the soil and water conservation and freshwater resource reserves in the source region of Changjiang River. Based on a decade of scientific expedition and research on the source region, the Changjiang River Scientific Research Institute accurately measured the glacier thickness on the main peak of Geladandong in 2022 and 2023 by employing ground-penetrating radar (GPR). We also conducted investigations on the upper limit of permafrost thickness in the Chatan Wetland. In association with numerical simulations of GPR wave field by multiple glacier and permafrost geological models, we have enhanced the effectiveness and accuracy of GPR in detecting glacier and permafrost in the source region. The findings manifest that both the glacier thickness on the main peak of Geladandong and the upper limit of permafrost in the Chatan Wetland have experienced varying degrees of decline. Long-term observations of glacier thickness and permafrost upper limits are essential and must be continued in order to accumulate more data and analyze trends, thus estimating ice reserves in the detection area and investigating the impacts of climate change on glaciers.

The source region of Yangtze River is highly sensitive to climate change, leading to significant alterations in river runoff. According to hydro-meteorological data from Zhimenda hydrological station and five meteorological stations in the source region of Yangtze River spanning 1960 to 2022, we investigated the changes in annual and seasonal runoff in the source region of Yangtze River. Utilizing correlation analysis, cross-wavelet transform, and principal component analysis, we further examined the relationship between runoff fluctuations and key meteorological factors. Findings indicated a notable upward trend in annual runoff at Zhimenda station throughout 1960 to 2022, with a particularly substantial increase of runoff in the past two decades. The seasonal runoff trend in the source region remained relatively stable from 1960 to 2000, but exhibited an increasing trend from 2000 to 2022, persisting to the present day. Precipitation, temperature, and relative humidity emerged as the primary meteorological factors exerting the most significant influences on the runoff at Zhimenda station.

Coarse-grained soil, the primary material used in the filling of earth-rock dams, consists of particles with a maximum size reaching meter-level. However, indoor tests only allow for downscaled samples. Shrinking the scale while ensuring that the indoor test results accurately reflect the mechanical characteristics of the actual material has always been a challenge in the research of earth-rock dams. Despite significant progress in the research of downscaling methods for coarse-grained soil and their effectiveness in recent years, disagreements still exist in some specific aspects. We made a comprehensive summary and analysis of the existing methods for downscaling coarse-grained soil, as well as the boundary effects and scale effects in sample testing. Scholars in Changjiang River Scientific Research Institute present a method of downscaling coarse-grained soil by determining the density of specimens according to pressuremeter modulus equivalent to that of the actual material, which is called the method of “Equivalent Pressuremeter Modulus to Determine Density”. We further elucidate the relationship between equivalent pressuremeter modulus and consistency in mechanical properties, and expound the theoretical foundation of this method,providing technical support for researching the downscale methods for coarse granular soil.

This article presents an eco-hydrological scheduling technology for hydropower stations aimed at enhancing the reproduction of fishes spawning drifting eggs. Artificial ecological flow processes can be created by adjusting the startup time and the outflow rate increment synchronously. In line with the principles and targets, an eco-hydrological regulation model for hydropower stations is proposed, and the corresponding solution ideas are then explained. The model was applied to the eco-hydrological regulation practices at Liyuan Hydropower Station based on the required ecological flow processes and mid-and-long-term inflow for target fish breeding in the middle reach of the Jinsha River. Results verifies the rationality and feasibility of the proposed technology, serving as a valuable reference for the eco-hydrological scheduling of other existing hydropower stations.

As a typical bifurcating channel in the tidal reach of the lower Yangtze River(also known as the Changjiang River), the Zhenjiang-Yangzhou Reach has experienced long-term complicated evolution. By examining historical documents, ancient maps, modern topographic mapping, and hydrological data, we analyzed the long-term evolution of the Zhenjiang-Yangzhou Reach. According to our findings, prior to the Western Han Dynasty, the Zhenjiang-Yangzhou Reach served as the mouth of the Changjiang River. Sediment gradually accumulated in the ancient estuary, giving rise to the development of a sandbar along the north bank. The river channel generally shifted in a southerly direction, resulting in decreased river width. The sediment deposition eventually stabilized, forming the Shiye sandbar branching channel and the Hechang sandbar branching channel. Throughout history, hydraulic power and sediment transport characteristics played a key role in shaping and transforming the river. River nodes located on both the north and south banks played an essential role in controlling the river’s flow regime. Since the 1950s, the channel morphology of Zhenjiang-Yangzhou Reach has been in a relatively stable state. However, recent developments have shown adjustments in the flow regime within the branching channel. Human activities, such as the construction of various projects in the river, have become important external factors influencing the evolution of the riverbed.