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.
The accuracy of hydrological forecasting is closely related to the multi-source uncertainty in the modeling process, and its interactive effects will further increase the prediction uncertainty. To reduce its impact, the Jinghe River basin was taken as the research object and the global sensitivity analysis method (LH-OAT) was used to effectively obtain the “available” parameter set of SIMHYD Hydrological model. Secondly, the impact of multiple uncertainties on runoff and soil moisture simulation was explored based on the hydrological model driven by meteorological elements obtained from the Statistical Downscaling Model (SDSM). Finally, the analysis of variance (ANOVA) method was used to dynamically quantify the relative contribution of various sources of uncertainty and their interactions to hydrological prediction uncertainty. The results show that the annual average runoff of the Jinghe River basin has a significant decreasing trend year by year. The “available” parameter group can better reproduce the hydrological process of the watershed, but its uncertainty has a significant impact on the uncertainty of the simulation results. The relative contributions of parameter, climate model, and climate change scenario uncertainties to monthly scale runoff are 30%, 40%, and 10%, respectively, and 75%, 15%, and 5%, respectively to soil water content. The interaction between multiple uncertainties before and after the flood has significantly increased. The research results are particularly important for reducing the uncertainty of hydrological prediction and improving the accuracy of hydrological simulation.
In order to provide reference for the decision-making of the cascade development plan and engineering scale of the Tiger-Leaping-Gorge reach cascade, and promote the early start and effectiveness of the project, we established the joint operation model of controlled water projects in the upper reaches of the Yangtze River based on boundary conditions considering the regulation and storage of the controlled reservoirs, the existing and constructing transbasin water transfer projects and the additional water consumption outside the river channel. By using the model, we calculated and analyzed the utilization of the reservoir’s own storage capacity of different regulating storage schemes in the Tiger-Leaping-Gorge reach. The water resource utilization benefits of downstream cascade hydropower stations was analyzed using power generation indicators as a representative. Through analysis and demonstrates, it is believed that, to meet the requirement of reserving 5.86 billion m3 of flood control storage capacity during the flood season, the Tiger-Leaping-Gorge reach set with 6 to 12 billion m3 regulating storage can fully utilize the hydraulic resources of this reach and increase the average annual power generation of downstream cascade hydropower stations from 5.62 to 11.94 billion kW·h for many years, and from 16.15 to 29.40 billion kW·h for many years during normal water periods and dry season. Further increasing the regulating storage can have more significant compensation benefits for downstream cascade hydropower stations, but the utilization rate of storage capacity is relatively low, and the marginal effect decreases rapidly.
In order to analyze the impact characteristics of the Three Gorges Reservoir operation process on the ecological flow and ecological effects of three outlets of the Jingjiang River, we use daily flow data of Xinjiangkou, Shadaoguan, Mituo Temple, Kangjiagang, and Guanjiapu, which are the main five hydrological control stations in the three outlets of the Jingjiang River, from 1988 to 2020. The changes in ecological surplus and ecological deficit indicators are calculated using the flow duration curve (FDC), and the overall hydrological variability D0 is calculated to evaluate the ecological runoff and hydrological change characteristics of the three outlets of the Jingjiang River. The research results indicate that: (1) after the operation of the Three Gorges, the proportion of Songzi in the flow of Jingjiang River flowing into Dongting Lake continues to increase, while the proportion of Ouchi and Taiping continues to decrease; the annual and flood season flow rates at Ouchi and Taiping show a significant downward trend; during the dry season, the flow rate at Songzi increases by 2.5 times compared to its natural state.(2) The average number of days of zero flow at Kangjiagang Station has increased by 30.88 days, showing an increasing trend, while at Mituo, it has decreased by 21.62 days, showing a decreasing trend.(3) After the operation of the Three Gorges, the overall FDC curve decreased, especially in the upper part, with a significant decrease in the magnitude and frequency of high flow rates; except for the low flow area of FDC at Xinjiangkou Station in Songzikou which exceeds the area before the operation of the Three Gorges, other stations with high and low flow cannot fully cover the areas where high and low flow occurred before the operation of the Three Gorges.(4) Due to the continuous decrease in the proportion of Kangjiagang and Guanjiapu in the flow from Ouchi to Dongting Lake, and the continuous increase in the proportion of Guanjiapu, the Kangjiagang and Guanjiapu stations continued to experience ecological deficits and surplus from 2003 to 2020.(5) The changes in the Xinjiangkou Station at Songzikou during the trial operation of the Three Gorges Reservoir (2003-2008) and after the trial operation of the Three Gorges Reservoir (2009-2020) reached 66.68% and 72.46%, indicating a obvious change, while the remaining control stations showed moderate changes. The operation of the Three Gorges has led to long-term ecological deficits or surplus in some areas, which is not conducive to the river ecosystem. It is recommended that basin managers strengthen monitoring of changes in the diversion ratio of different branches at the same outlet and carry out corresponding ecological impact management work.
In order to explore the characteristics of heavy metal pollution in surface sediments of Niulan River (Kunming Section), the surface sediments of 20 points in the basin were collected ;and the contents of 8 metals (Cu, Zn, Cr, Cd, Ni, Pb, Hg and As) were determined in three water periods (wet period, dry period and normal period). Water stage and regional difference analysis, potential risk assessment and heavy metal source analysis were also carried out. The results showed that the content of Cd (1.45 mg/kg) and Hg (0.23 mg/kg) of heavy metals in sediments of Niulan River (Kunming Section) was 6.7 times and 4.0 times that of the background values 0.218 mg/kg and 0.058 mg/kg in Yunnan Province, respectively. It indicates that Cd and Hg pollution are relatively serious. The soil accumulation index showed that Cd had the highest pollution level in the three water periods of Niulan River (Kunming Section), followed by Hg. The average pollution levels reached moderate pollution and moderately moderate pollution, respectively. Therefore, Cd and Hg are the main ecological risk contributing factors of heavy metal pollution in surface sediments of Niulan River (Kunming Section). At the same time, the potential ecological risk coefficient showed that the distribution of potential ecological risk was higher in the main stream than in the tributaries, higher in the lower stream than in the upper stream and higher in the north than in the south.
The safety of water supply quality is a perennial concern in society. Silver nanoparticles (AgNPs) have demonstrated significant inhibitory and inactivating effects on a variety of pathogenic microorganisms (e.g., Escherichia coli and Staphylococcus aureus), thereby underscoring their substantial potential for application in water treatment technologies. This study focuses on the water purification efficacy of AgNPs, elucidating the working mechanisms of AgNPs composite materials in water purification. It systematically organizes and analyzes the research on nanosilver materials for water purification, offering an in-depth exploration of the current state of the art in this field. The biological toxicity and environmental risks associated with nanosilver have been analyzed, along with the prospective application of AgNPs in water purification. The findings of this work offer some insights and recommendations for studies endeavors in the realms of emergency water treatment, assurance of water quality safety, novel water purification technologies, and the development of AgNPs composite materials.
With Geheyan hydropower development in Qingjiang River Basin as analysis object, the comprehensive benefit of carbon emission reduction in the whole process of hydropower development is estimated by hybrid analysis method. The results show that the carbon emission per unit power generation of Geheyan Hydropower Station is 33.22g CO2eq/(kW·h), which is much lower than that of thermal power generation. And the tourism industry derived from hydropower development can reduce 2 282 100 tons CO2, the shipping industry derived from hydropower development can reduce 1 060 290 tons CO2. The derivative industry has significant benefits in reducing carbon emissions. The comprehensive annual average carbon emission reduction benefit of Geheyan hydropower development is 2 975 500 tons of CO2. Hydropower development has very obvious benefits of carbon emission reduction, and it is a powerful means of carbon emission reduction.At the same time, derivative industries often have a low-carbon nature. In the development process, we need to consider the guidance of derivative industries as a whole to further increase the benefits of carbon emission reduction.
Slope ecological restoration is important in the construction of power transmission projects. In traditional spray-sowing technology, we use cement as binding materials, which results in a low germination rate of vegetative substrate, restricting the ecological restoration efficiency. Taking the high-steep slope of power transmission construction project in the red soil area as research object, we used seaweed polysaccharide, which is a polymer chemical binder, to replace cement, with addition of ecological fertilizer and fiber. Indoor direct shear tests and pot experiments were carried out with bermudagrass as the plant species to analyze the mechanical and planting properties of the neotype spray-sowing substrate in red soil. Results showed that seaweed polysaccharide and fiber were the main factors affecting the cohesion of the neotype spray-sowing substrate. Bermudagrass germination rate was negatively correlated with seaweed polysaccharide content, while was significantly positively correlated with ecological fertilizer content, and exhibited no significant correlation with fiber content. The optimum content of seaweed polysaccharide to improve the substrate cohesion was 1%. The addition of fiber could also improve the cohesion, and the maximum cohesion was achieved when fiber content was 0.75%. When the content of seaweed polysaccharide was 1% and the content of ecological fertilizer was 5%, the bermudagrass germination reached 100%. The research results would provide new technical references for ecological restoration of high-steep slopes in red soil areas.
To investigate the spatial and temporal distribution patterns of vegetation net primary productivity (NPP) in the Lüliang Mountains from 2000 to 2019, and to quantitatively assess the impact of human activities on these patterns, this study employs an enhanced CASA model to estimate the actual NPP (NPPA) for the region. By integrating the potential NPP (NPPP) estimated using Zhou Guang-sheng’s model, we calculate the NPP loss (NPPH) attributed to human activities. In association with the Relative Impact Contribution Index (RICI), we quantify the influence of human activities on vegetation NPP and analyze how changes in land use types affect NPPA. Results reveal that NPPA in the Lüliang Mountains generally exhibited a decreasing trend from southeast to northwest, while NPPH displayed an increasing trend in the same direction. Changes in land use primarily affected forest land, farmland, grassland, and water bodies. Increasing areas of forest land and farmland led to a rise in total NPPA, whereas converting forest land to other uses and transforming grassland into farmland resulted in a decrease in NPPA. Human activities account for 51.80% of the observed changes in NPP, highlighting their significant role in altering NPP in the Lüliang Mountains. These findings provide a scientific foundation for the restoration, protection, and sustainable management of ecological environment in the Lüliang Mountains.
Qujing City is located in the upper reaches of the Yangtze River and the source of the Pearl River holding an important ecological position. Exploring the dynamics and evolutionary process of rocky desertification over a long time series in this area is of great significance. In this study, using Landsat5, Landsat8, DEM, etc., we obtained the rocky desertification distribution from 1990 to 2020 through the Google Earth Engine(GEE) cloud platform and decision tree classification, and analyzed the spatial and temporal change characteristics and evolution process of the rocky desertification. The results show that: 1) the overall rocky desertification in Qujing City was primarily characterized potentially rocky and no rocky desertification; in 31 years, the rocky desertification area in Qujing City decreased by 1 728.38 km2, while the no rocky desertification area increased by 1 936.61 km2, and the overall rocky desertification was significantly improved.(2) From 1990 to 2020, the overall change rate of rocky desertification in Qujing City was -57.61 km2/a, and the change rate decreasd as the intensity of rocky desertification aggravated: extreme intensity > intensity > moderate > mild > no > potential desertification. (3)Over 31 years, the pattern of rocky desertification evolution in Qujing City remained mostly unchanged, covering an area of 7 967.67 km2, accounting for 61.39%. Continuous and fluctuating transformations, reflecting improvements in rocky desertification, covered an area of 3 197.03 km2, or 24.63%. The area of deterioration was 558.52 km2, accounting for 4.3%. The results indicate a general improvement in rocky desertification in the study area.
Yaodi levee of Hanjiang River is a national first-class embankment, serving as an important flood control barrier safeguarding the Hanbei Plain and Wuhan City. The Lijiazhou levee of Tianmen City is a historical danger section, with a series of piping dangers occurred in this section of the Hanjiang River during the autumn flood season of 2021. A new design of relief well was applied to treat hidden danger of piping in 2022. A three-dimensional seepage model was established and the effect of relief well under different working conditions was analyzed for design. Simulation data shows that the relief well has a significant drainage and pressure reduction effect, and the permeability stability meets the requirements under flood conditions. No piping danger occurred during the 2023 flood period of the Hanjiang River when the flood level was 1.3 m higher than the flood level during 2021 in this embankment section. It indicates that the relief wells played a significant role in flood control and disaster reduction. Practical application shows that relief well is one of the most effective measures for typical pipe surge hazards of binary structure embankment foundation. This study provides references for dealing with similar levee pipe surge hazards.
Storm surge is one of the most serious natural disasters along the coast of China. The temporal and spatial distribution of storm surge in China’s coastal areas was obtained by analyzing the storm surge data of 67 stations from 1950 to 2003. It is found that the southeast coast of China is the region with the most serious storm surge disasters in terms of frequency and intensity, and the intensity of storm surges is concentrated in Ⅲ, Ⅳ, and Ⅳ levels. The storm surge in the Yangtze Estuary and Hangzhou Bay are relatively large. Moreover, the path of the wind field and the astronomical tide have a significant impact on the storm surge. Taking Dinghai station as an example, the path of the tropical cyclone turning to the west of 125°E has the most significant impact on the storm surge and most of the occurrence time of peak surge is around spring tide and before and after the astronomical low tide. The results can provide a reference for storm surge risk assessment and disaster prevention and mitigation.
To cope with the severe flood challenges caused by extreme meteorological events in the western part of Shanghai, an effective water level control strategy was proposed. The Qingsong region of Shanghai during the “Fireworks” typhoon was selected as the research object. The actual rainfall and working condition data were comprehensively analyzed, including rainfall, water level of the river outside the polder, water level of the secondary polder, and water level process of the river outside the polder. Two strategies were proposed, namely, over-storage of rivers and lakes in the secondary polder area and controlling of drainage after the rain peak in the polder area. The effectiveness of alleviating the high water level was evaluated by using digital topographic analysis and numerical simulation of flood control. It is found that the implementation of the above strategies can greatly enhance the storage capacity, and the theoretical estimate is to increase the capacity by about 11.7 million m3 and 2.46 million m3, respectively, which can reduce the water level of the river channel in the area by about 30 cm, and effectively alleviate the high water level. This study not only verifies the effectiveness of the strategy, but also adds new controlling methods to the existing flood control and drainage system, which provides a scientific basis for the city’s scheduling decision-making when facing major water challenges, and has important practical value and theoretical contribution to building a more resilient water management system and ensuring the safe operation of the city.
In order to reveal the characteristics of radial and vertical jets in the opposite wall jet, renormalization group k-ε model is adopted to simulate complex three-dimensional opposed jet. The partition structure and expansion rate of radial and vertical jets are analyzed.The influences of initial Reynolds number and nozzle distance on jet expansion rate are discussed.The results show that radial jet and vertical jet have similar regional division, however, vortices in different directions formed in the flow field have different influence ranges. The initial Reynolds number has no obvious effect on the expansion rate of the radial jet. The nozzle distance has a significant effect on the expansion rates of radial and vertical jets. The larger the nozzle distance is, the larger the expansion rates of the radial and vertical jets are. Meanwhile, the nozzle distance has a certain influence on the jet development. Near nozzle spacing shortens the time for jet to reach the maximum velocity point, and speeds up the development process.
In the process of flood discharge atomization, a large number of water droplets will be generated by the collision between the jetted water tongue and the downstream water cushion pond. The droplets carried by the airflow form a fog flow, which affects slope stability and traffic safety. To predict the distribution of fog flow in the downstream space, the interaction process between the jetted water tongue, air, and downstream water was simulated, and a background field for fog flow generation and transport was constructed. Based on the fog source generation mechanism and dimensional analysis methods, a calculation formula for fog flow source strength is proposed, and a mathematical model for fog flow source strength and diffusion is established. The fog flow process of the 3# spillway hole discharge at the Manwan hydropower station is simulated using this model. The comparison shows that the distribution of fog flow source strength and the location of the fog source generation are consistent with prototype observation. The distribution of fog flow concentration distribution in the downstream space is in line with the prototype observation, and the calculated values of fog flow concentration at observation points match the trend of the original observed values. The comparison results verify the applicability of this model, providing a new method for predicting the distribution of fog flow in downstream spaces of flood discharge atomization.
Suction vortices at the inlet of discharge structures often affect the discharge safety of water conservancy projects. Existing research primarily focuses on theoretical analyses and simulation methods for inlet vortices, while studies on the hydraulic response characteristics of vortices under operational disturbances are limited, especially with respect to scheduling control. We performed comparative experimental research through prototype observation, numerical simulations, and physical model experiments to elucidate the mechanisms and key factors influencing vortex formation. We also aim to clarify the hydraulic response of discharge structures under various regulation and operational conditions and to establish the relationship between water flow patterns and flood discharge scheduling methods. Our findings reveal that vortex formation and intensity are significantly affected by factors such as water flow velocity, circulation patterns, flow field boundary conditions, and the relative submergence depth at the gate. These vortices result from the combined effects of river regime, design and layout of flood discharge structures, and flood discharge scheduling practices. By optimizing discharge scheduling and regulation, we can effectively reduce the intensity of harmful vortices and mitigate operational risks associated with discharge structures.
In order to explore the effect of mulching on soil aeration under drip irrigation,field experiment was carried out in the sub-humid area of Northeast China. In the experiments,four treatments,including mulched + fertilized,non-mulched + fertilized,mulched + unfertilized and non-mulched + unfertilized drip irrigation were tested. The results showed that soil redox potential in surface layer (0-10 cm)was increased by plastic film mulching with a difference of 2.7-10.0 mV (increasing by 0.5%-2.0%) compared with no plastic film mulching. Plastic film mulching had no significant effect on the distribution of soil redox potential in 0-30 cm layer,and the redox potential of each treatment increased with the increase of depth in the range of 0-30 cm. During the maize growth period,the soil under drip irrigation belonged to strong oxidizing soil with good aeration,and the redox potential of each treatment was higher than 500 mV. Plastic film mulching significantly improved soil aeration in the early growth stage,and the soil redox potential for mulching increased by 59.5-122.9 mV (9.7%-22.8%) compared with no mulching.
Rural water supply system is affected by geographical conditions, water resources endowment and regional differences in economic development level. In some areas, rural water supply projects exhibit weak resilience to risks, potentially leading to water shortage or contamination during emergencies. In this paper, the natural disaster risk theory is introduced into the analysis of rural water supply risk. An evaluation index system and the corresponding evaluation model were constructed from four aspects: disaster-causing factors, disaster-prone environment, disaster-bearing entities, and disaster prevention and mitigation capability. Based on data of rural water supply projects in 34 districts in Chongqing in 2020, the rural water supply risk at district level was assessed. According to the calculation results, the risk level was divided into three levels: low, medium and high, with the thresholds set at 0.336 6 and 0.558 1 respectively. Results indicate that five districts (Yongchuan, Beibei, Wansheng, Fengjie and Fuling), primarily located in the urban area, exhibited low risk. Two districts (Wushan and Youyang) were classified as high risk. Wushan is situated in the Three Gorges reservoir area in northeast Chongqing, while Youyang is in the Wuling Mountainous area in southeast Chongqing. The remaining 27 districts were categorized as medium risk. The risk assessment results offer technical support for early warning and response for rural water supply risks in Chongqing.
To investigate the permeability of sludge solidified soil prepared using a self-developed water glass-based curing agent, the microstructure and pore size distribution characteristics of the soil were analyzed using scanning electron microscopy (SEM) and mercury intrusion porosimetry (MIP) with varying amounts of curing agent. Based on the effective porosity theory, a one-dimensional permeation differential equation was established, and a constant head permeability test scheme for fine-grained soil was proposed and applied to the permeability testing of the solidified soil. Through back pressure saturation and unloading tests, the relationship between the effective porosity rate increment and the pore water pressure function was established, and the permeability parameters of the soil were obtained through constant head permeability testing and numerical calculations. The permeability parameters of the solidified soil were studied with varying curing agent content. The results showed that with increasing amounts of curing agent, both the particle structure and porosity rate of the solidified soil increased. The initial effective porosity rate and starting hydraulic gradient of the solidified soil decreased monotonically, while the absolute effective permeability coefficient initially decreased and then increased, reaching a minimum value at a curing agent ratio of 7%.
To investigate how different fibers influence soil reinforcement, basalt fiber and glass fiber were separately added to the same soil. Unconfined compressive strength tests were performed to compare the stress-strain curves and analyze the relationship between strength and both fiber content and fiber length for the two types of fiber-reinforced soil. Additionally,fiber anchorage test was conducted to explore the mechanisms of fibers enhancing soil strength. The results demonstrate that fiber-reinforced soil exhibits significantly greater compressive strength compared to plain soil. As fiber length increases, the strength of both basalt and glass fiber-reinforced soils first rises and then falls, with the optimal fiber length being 9 mm. Similarly, increasing fiber content causes the strength of both types of fiber-reinforced soil to fluctuate, with two peaks observed; the optimal fiber content is 0.5%. The fiber anchorage tests reveal that the pull-out force of the fibers varies with changes in fiber spacing. At small spacings, fibers interact, resulting in peak and valley values of pull-out force. As fiber spacing increases and reaches a critical anchorage distance, fibers no longer affect each other.
To study the relationship between shear stress and shear displacement at the nail-soil interface, as well as the variation of interfacial shear strength and apparent friction coefficient with changes in soil water content and stress state, a pull-out shear test was conducted on the interface between silt and nail under controlled water content in this paper. The results of the soil-nail interface shear test were compared with those of the soil-structure shear test. Additionally, a calculation analysis of the shear stress at the nail-soil interface was conducted. The results show that the shear stress at the nail-soil interface increases significantly with the increase in overburden pressure, and the pull-out displacement corresponding to the peak shear stress also increases gradually. Meanwhile, a softening phenomenon occurs after the shear stress reaches its peak. The shear stress at the soil interface is negatively correlated with the soil’s water content. The shear stress in the low water content silt test is almost double that of the saturated silt test, and the pull-out displacement corresponding to the peak shear stress also increases by about twofold. The peak and residual shear stresses increase approximately linearly with increasing overburden pressure, and decrease significantly with increasing soil water content (w). The difference between them decreases with increasing w, and increases with increasing overburden pressure. The research results can provide a reference for studying the pull-out bearing capacity of nails.
The dry density of soft rock rockfill is an important control index for the design and construction of earth-rock dams, as it directly influences the settlement of earth-rock dams during construction and operation. The Φ950 mm×H1 000 mm super-large compactor was used to conduct compaction tests under five levels of compaction energy, including 483, 992, 1 475, 1 957,2 681 kJ/m3, for the strongly weathered silty mudstone, weakly weathered silty mudstone,and a mixture of silty mudstone. The results were compared with those from φ300 mm×H285 mm large compaction test. The test results show that the dry density increases with the increase in compaction energy.When the compaction energy is less than 2 000 kJ/m3, the dry density increases rapidly with increasing the compaction energy. When the compaction energy exceeds 2 000 kJ/m3, the rate of increase slows down and the increment is small. Further increasing the compaction energy does not significantly improve the dry density.Under the same compaction energy, the maximum dry density from the ultra-large compaction is slightly lower (by 0.01 to 0.02 g/cm3) than that from the large compaction test. The size effect of soft rock rockfill on compaction characteristics is not significant, and under the heavy standard compaction functional conditions, it is appropriate to use a compaction instrument with a diameter of 300 mm to study the compaction characteristics of soft rock rockfill indoors.
The instability and failure of surrounding rock in water-bearing weak strata are often closely related to the effects of water. To deeply reveal the influence and mechanical mechanism of water saturation on rock damage and failure, uniaxial compression tests on white sandstone under dry and water-saturated conditions were carried out. Through comparative analysis, the effects and mechanisms of water saturation on strength, deformation, stress thresholds, strain energy, and acoustic emission characteristics were studied. The results showed the following when the white sandstone was water-saturated: (1) Uniaxial compressive strength and elastic modulus decrease, while Poisson’s ratio increases.(2) The normalized crack initiation stress (σci/σf) decreases. The analysis shows that the softening effect of water weakens the bonding between mineral particles, making new cracks easier to initiate, thus leading to a decrease in σci/σf.(3) The normalized crack damage stress (σcd/σf) decreases. Based on the analysis of the AE b-value, the proportion of small-scale ruptures increases. The increase in the proportion of small-scale fractures makes it easier for microcracks to coalesce into macrofractures, leading to a decrease in σcd/σf.(4) The total energy (U), elastic energy (Ue), and dissipated energy (Ud) at peak strength decrease, and the ratio of elastic energy to total energy (Ue/U) also decreases.(5) The analysis based on AE RA value (ratio of rise time to amplitude) and AF value (average frequency) shows that the proportion of shear fractures increases after water saturation, making it easier to produce intragranular fractures. The research results provide important insights into the failure mechanisms of water-saturated rocks.
To explore the reuse of steel slag powder in PVA-ECC (Polyvinyl Alcohol Engineered Cementitious Composite), we produced PVA-ECC samples by incorporating steel slag powder at various mass fractions. We measured the mass change, compressive strength, and tensile performance of the test samples in Na2SO4 solution (with a mass fraction of 5%) during dry-wet cycle accelerated sulfate attack tests, cubic compressive strength tests, and axial tensile tests. By microstructural and phase analysis using scanning electron microscopy (SEM) and X-ray diffraction (XRD) meter, we examined the influence of steel slag powder content on the sulfate resistance of PVA-ECC. Results indicate that when the steel slag powder content in PVA-ECC reaches 20%, the mass loss remains lower than that of the reference group. PVA-ECC with a low dosage of steel slag powder demonstrates sound corrosion resistance, with compressive and corrosion resistance coefficients of 1.13, 1.02, and 0.96 for the S20 group, respectively. PVA-ECC specimens containing steel slag powder exhibited multiple cracks; however, the addition of steel slag powder enhanced tensile strength, with a maximum increase of 31.4% observed in the S40 group. The inclusion of an appropriate amount of steel slag powder effectively mitigates corrosion damage, with no significant material deterioration observed within the studied age range when the addition does not exceed 60%.
Based on runoff series from the Tuotuohe and Zhimenda hydrological stations, we use the North Atlantic Oscillation Index (NAOI) to analyze the intensity of the North Atlantic Oscillation (NAO) and the impact of NAO on winter, summer, and annual runoff at the two stations. The impact of changes in wet and dry conditions was analyzed using correlation analysis and cross-wavelet transform to examine the multi-scale correlation characteristics between the NAO and runoff. The possible impact of NAO on runoff in the source region of the Yangtze River was also analyzed from the perspective of sea-atmosphere coupling affecting atmospheric circulation mechanisms. The research results showed that winter runoff was greatly affected by NAO. Before 2000, strong NAO years corresponded to relatively lower runoff probabilities, while weak NAO years corresponded to slightly higher runoff probabilities. Summer runoff was more significantly affected by the temperature in the source region of the Yangtze River. In summer, the response to the strength of NAO was not as obvious as in winter. The NAOI and the runoff at the Tuotuohe and Zhimenda hydrological stations showed good convergence in inter-decadal variation, but there was no close relationship on inter-annual or shorter time scales. There was a resonance cycle between monthly runoff and the NAOI on a time scale of 8-16 months throughout the entire period from 1960 to 2020. Before the 1970s and 1980s, the two stations and the NAOI showed similar frequency and phase changes; after that, they exhibited opposite phase changes. The North Atlantic Oscillation, as the most important climate mode in the North Atlantic region, directly affects the strength of the monsoon and westerly winds through atmospheric teleconnection and Rossby Waves, and then adjusts the water vapor transport over the Qinghai-Tibet Plateau, thereby affecting the temporal and spatial distribution of precipitation and runoff in the source region of the Yangtze River.
Forage yield and quality are the basis of reasonable livestock carrying capacity, which is of great significance for livestock production. Based on the field survey data and spatial information of natural alpine meadows in Chatan wetland of Dangqu basin, this paper analyzes the spatial distribution of forage nutrient quality indexes and explores their spatial heterogeneity under the change of soil types by combining with the laboratory test. The results showed that: crude protein content decreased and then increased from south to north in Cambisols pasture, with the minimum value occurring at about 32.90°N; neutral detergent fiber content increased and then decreased from south to north in highly active lyophilized soil pasture, with the maximum value occurring at about 32.85°N; and acidic detergent fiber content increased and then decreased from south to north in Cambisols pasture, with the maximum value occurring at about 32.90°N. Between 4 650 and 4 850 m, the crude protein content of Cambisols pasture had an extremely significant positive correlation with elevation (R2=0.61, p<0.01); the acid detergent fiber content of Cambisols pasture had a significant negative correlation with elevation (R2=0.43, p<0.05). High-quality alpine pastures are mainly distributed in a U-shape from south to north with 32.90°N as the lowest point. Forage nutritional quality was positively correlated with elevation between 4 650 and 4 850 m. The research results can deepen the knowledge of the nutritional quality of the alpine grassland in the Yangtze River source, improve the rational utilization of the alpine grassland in the Yangtze River source, and provide auxiliary suggestions for the intensive, large-scale, ecological and digital development of the animal husbandry industry.
The grassland ecosystem is an important resource for humans to cope with climate change. The Headwaters of the Three Rivers is an important area to study the status of grassland ecosystem due to its vulnerability and sensitivity. Based on the totally 45 measured grassland biomass with varied coverage in the headwaters, mainstreams and tributaries, this study analyzed the spatial distribution of biomass and the ratio in the southern source of the Yangtze River. The results indicated that the grassland biomass becomes lower when the location is closer to headwater (as elevation increases). The grassland above-ground biomass (AGB) ranged from 21.12 g/m2 to 850.61 g/m2, while belowground biomass (BGB) ranged from 50.34 g/m2 to 6 810.68 g/m2. The higher the grassland coverage, the more obviously the biomass decreased with increasing elevation. The ratio of grassland AGB to BGB was less than 0.5, and the higher the grassland coverage, the lower the ratio. The study explored the distribution of AGB and BGB and their ratios, which provided preliminary exploration and data accumulation for understanding the grassland status in the source region of the three rivers.
