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The Yangtze River (hereafter referred to as the YZR), the largest river in China, is of paramount importance for ensuring water resource security. The Yangtze River Basin (hereafter referred to as the YRB) is one of the most densely populated areas in China, and complex human activities have a significant impact on the ecological security of water resources. Therefore, this paper employs theories related to ecological population evolution and the Driving Force-Pressure-State-Impact-Response (DPSIR) model to construct an indicator system for the ecological security of water resources in the YRB. The report evaluates the ecological security status of water resources in each province of the YRB from 2010 to 2019, clarifies the development trend of its water resource ecological security, and proposes corresponding strategies for regional ecological security and coordinated economic development. According to the results of the ecological population evolution competition model, the overall indicator of the ecological security of water resources in the YRB continues to improve, with the safety level increasing annually. Maintaining sound management of water resources in the YRB is crucial for sustainable socioeconomic development. To further promote the ecological security of water resources in the YRB and the coordinated development of the regional economy, this paper proposes policy suggestions such as promoting the continuous advancement of sustainable development projects, actively adjusting industrial structure, continuously enhancing public environmental awareness, and actively participating in international ecological construction and seeking cooperation among multiple departments. [ABSTRACT FROM AUTHOR]

China's Yangtze River Basin has an increasingly strong demand for crude oil. As a seaborne import port for crude oil, Ningbo-Zhoushan Port is under pressure to undertake the transshipment of crude oil to various oil terminals in the Yangtze River Basin. To alleviate the stress of crude oil transportation in Ningbo-Zhoushan Port, the port operator proposed the crude oil sea–river transshipment scheme in Nantong Port. Therefore, this paper aims to verify the feasibility of this scheme. We used the discrete event system modeling and entity relationship diagram method to construct the hierarchical and concept models of the Yangtze River Basin's crude oil sea–river transportation system. Furthermore, we developed corresponding simulation modules on the Witness platform and carried out a simulation experiment of the crude oil sea–river transfer scheme. In the experiment, we analyzed the influence of the transshipment ratio on berth utilization, waiting time, and sailing time of other ports by adjusting the parameter of the transshipment ratio. The experimental results show that when the transshipment rate reaches 100%, the utilization rates of loading and unloading berth in Nantong Port are 4% and 13%, respectively, which evidences that Nantong Port has transshipment potential. At the same time, the simulation experiment's statistical indicators, such as the utilization rate of oil berths, the queuing time of oil tankers, and the sailing time, not only confirm the feasibility of the crude oil sea–river transshipment scheme of Nantong Port but also confirm that the scheme is helpful to improve crude oil transportation efficiency. The simulation results benefit the port operation decision, and the established model and simulation module can be encapsulated and reused. [ABSTRACT FROM AUTHOR]

Serving as a crucial part of the Yangtze River Basin (YRB)'s flood control system, Flood Detention Areas (FDAs) are vital in mitigating large-scale floods. Urbanization has led to the development of urban FDAs, but significant losses could ensue if these FDAs are activated. With improved reservoirs and embankments, flood pressure in the middle reaches has lessened, posing challenges in balancing flood control and economic benefits. This paper presents a comparative analysis of land use, GDP, and population in FDAs and adjacent cities, enhancing our understanding of their disparities and interrelations. Using the Analytic Hierarchy Process (AHP)–Entropy Weight Method (EW)–Technique for Order of Preference by Similarity to Ideal Solution (TOPSIS) comprehensive evaluation method, we assess changes in flood control and economic values in FDAs. The results show a conflict between flood control and economic policies in FDAs, highlighting their underestimated economic potential, especially in urban areas. This study identifies differences in economic development across FDAs and a strong correlation between flood control value and inundation rates. Based on evaluations and simulations of the 1954 flood, we provide recommendations for the FDAs' construction plan, which serves the development and flood management of the YRB and offer insights for similar assessments elsewhere. [ABSTRACT FROM AUTHOR]

In-depth insights into the profound impacts of climate change and human activities on water resources are garnered through the dynamic changes in surface water, a crucial aspect of effective water resource management and the preservation of aquatic ecosystems. This paper introduces an innovative approach employing the random forest algorithm for the systematic extraction and monitoring of surface water at large regional or national scales. This method integrates spectral bands, spectral indices, and digital elevation model data, offering a novel perspective on this critical task. A data-filling model is proposed to mitigate the impact of missing data due to cloud cover. Leveraging the capabilities of the Google Earth Engine (GEE), detailed information on surface water dynamics during the rainy and dry seasons in the Yangtze River Basin (YRB) from 1991 to 2021 is extracted using Landsat time series imagery. The analysis encompasses spatial-temporal variation characteristics and trends, with a specific focus on the intricate interplay between the areal extent of surface water and hydro-meteorological factors in each sub-basin of the YRB. Importantly, this includes considerations of potential groundwater contributions to surface water. Key findings from our research include: (1) Achieving a remarkable overall classification accuracy of 0.96 ± 0.03 in obtaining reliable surface water datasets with the support of GEE. (2) Identifying significant trends, such as a noteworthy increase in rainy season surface water bodies (+248.0 km2·yr−1) and a concerning decrease in surface ice/snow cover during both rainy and dry seasons, with change rates of −39.7 km2·yr−1 and −651.3 km2·yr−1, respectively. (3) Uncovering the driving mechanisms behind these changes, revealing positive correlations between the areal extent of rainy season surface water bodies and precipitation, as well as negative correlations between surface ice/snow cover area and average surface skin temperature. It is crucial to note that these driving factors exhibit variation among secondary river systems, underscoring the complexity of surface water dynamics. Furthermore, comparative analyses with existing surface water products are conducted, contributing to a deeper understanding of the advantages and uncertainties inherent in our proposed extraction method. The proposed method for large-scale surface water extraction not only enhances the monitoring of spatio-temporal surface water dynamics in the YRB but also provides valuable insights for the sustainable utilization and protection of water resources, considering the potential role of groundwater in supplementing surface water. [ABSTRACT FROM AUTHOR]

Accurate runoff prediction plays a pivotal role in facilitating effective watershed management and the rational allocation of water resources. Given the inherent challenges posed by the nonlinear and nonstationary nature of runoff sequences, this study introduces a novel coupled model, combining complete ensemble empirical mode decomposition with adaptive noise (CEEMDAN), variational mode decomposition (VMD), long short-term memory (LSTM), and Informer techniques for monthly runoff prediction at the Wulong hydrological station of the Yangtze River Basin from 1973 to 2022. In addition, by comparing the prediction results of the traditional statistical model, which is the seasonal exponential smoothing model, with those of the machine learning model, the prediction accuracy of the machine learning model was found to be much higher than that of the traditional statistical mode. And the coupled model of secondary decomposition and secondary prediction was compared with other types of coupled models, such as one decomposition and one prediction. The CEEMDAN-VMD-LSTM-Informer model exhibited superior performance, as evidenced by an NSE value of 0.997, MAE of 1.327 × 108 m3, MAPE of 2.57%, and RMSE of 2.266 × 108 m3. The combined model proposed in this paper has the highest prediction accuracy, rendering it suitable for long-time series prediction. Accurate runoff prediction plays a pivotal role in facilitating effective watershed management and the rational allocation of water resources. [ABSTRACT FROM AUTHOR]

Objective A prerequisite for managing a catchment is to comprehensively understand the changes in its water quality. Using different methods, this paper comparatively analyzes the spatiotemporal variation in water quality of the Yangtze River, including its main streams and tributaries. Method The study is based on water quality data collected from 2008 to 2018 from 16 monitoring sections within the basin. Various methods, including the comprehensive water quality index (WQI), water pollution index (WPI), and comprehensive water quality identification index (Iwq), were used to assess water quality. Additionally, statistical methods including the Mann- Kendall trend test, cluster analysis, and discriminant analysis were utilized to analyze the spatiotemporal variation in water quality. Result In flooding and non-flooding seasons, the section proximal to the Leshan Minjiang Bridge had minimum dissolved oxygen (DO) concentration, which is 2.86 mg/L and 3.16 mg/L, respectively. Conversely, the Nanchang Chucha section had maximum concentration of chemical oxygen demand (CODMn) and ammonia nitrogen (NH3-N), which was 10.00 mg/L and 6.45 mg/L, and 2.23 mg/L and 4.48 mg/L, respectively. In the nonflooding season, 31.82% of water in the Nanchang Chucha section achieved Class IV grade or higher (evaluated by WPI), whereas this figure reduced to 19.70% (evaluated by WQI) for the Leshan Minjiang Bridge section. The Iwq method yielded the highest water quality, followed by WQI and WPI. All three methods indicated that water quality had improved in the Leshan Minjiang Bridge, Changsha Xingang, and Nanchang Chucha sections. Water quality varied spatially, with poor quality observed in the Leshan Minjiang Bridge, Changsha Xinkang, and Nanchang Chucha sections, and slightly poor quality was found in the Minjiang, Xiangjiang, and Ganjiang sections. Conclusion The evaluation of water quality using different methods within the Yangtze River basin yielded varied results, with the WQI method working best. [ABSTRACT FROM AUTHOR]

Land use/cover change (LUCC) can change the energy balance of the earth's surface by altering its biophysical properties (surface albedo), and it also has an important impact on the ecological climate. In this paper, using surface energy balance algorithms, the differences in energy balance and the resulting ecoclimatic effects under different land use changes in the Yangtze River basin from 2000 to 2020 were analyzed. The results showed that: (1) from 2000 to 2020, the energy uptake of surface net radiation ( R s ) in the Yangtze River basin showed a downward trend with increasing intensity of impact from human activities. This indicated that human activities could weaken the positive trend of R s uptake and increase the warming effect; (2) R s and latent heat flux (LHF) showed an upward trend, which was more obvious in natural and semi-natural regions and mixed pixel regions; (3) LHF − R s energy uptake showed a decreasing trend, indicating that the effect of R s on surface absorbed energy was greater than that of LHF, which was more significant in old urban areas and urban expansion areas. This research highlights the variation in the surface energy budgets of the five land use types with different levels of human activities. This will provide a theoretical reference for future land planning and management. It will also provide a theoretical basis for judging climate change trends and urban heat island effects in the Yangtze River basin from the perspective of bio-geophysics. [ABSTRACT FROM AUTHOR]

High Mountain Asia (HMA), with its high altitude, widely distributed snow and frozen soil, influences the climate of the northern hemisphere and even the world through thermal balance and the water vapor cycle and is also an indicator of global climate change. The influence of HMA snow cover on its surrounding areas has always been a research hotspot. Taking the Yangtze River Basin (YRB) of China as an example, this paper analyzes the relationship between winter snow depth in HMA and drought and flood in spring and summer in the YRB in the recent 40 years by using Singular Value Decomposition (SVD). The results show that the influence of snow cover on drought and flood in spring is inversely different between eastern and western parts of HMA, while the effect in summer is consistent. When the snow depth is larger (smaller) in the east and smaller (larger) in the west in winter, the YRB is drier (wetter) in spring. When the overall snow depth in HMA is larger (smaller) in winter, the northern part of the middle and lower reaches of the YRB is drier (wetter) in summer. The results provide support for understanding the impact of HMA snow cover on the surrounding climate and some important indicators for drought and flood prediction in the YRB. [ABSTRACT FROM AUTHOR]

The Yangtze River Basin (YRB), a key biodiversity area and a major economic zone in China, the biodiversity of the area is confronted with severe challenges. In this paper, we analyzed species distribution patterns based on a dataset with 18,538 seed plant species to identify hotspots and evaluate conservation effectiveness and gaps of the YRB. We calculated distribution patterns of species richness with the top 5% richness algorithm and complementarity algorithm, and reconstructed a phylogenetic tree and elucidated spatial phylogenetics. There were 214 hotspot grid cells covering only 6.8% of the study region, but containing 88% seed plant species. Then, we conducted correlation analysis on distribution patterns of different algorithms and species categories, which showed moderate or weak correlations between the top 5% richness algorithm and complementary algorithm. Conservation effectiveness analysis indicated there were 116 hotspot grid cells (accounting for 73.6% of the total species) protected by current conservation networks and there are many conservation gaps remaining. Finally, we used the maximum entropy model (MaxEnt) to predict suitable habitat areas of threatened species under current and future climate scenarios. Prediction analysis results indicated future expansion of suitable habitat to the southeast, and reduction in the central and western portions of the study area. When we considered anthropogenic areas, the suitable habitat was severely decreased, indicating the importance of optimizing the layout of conservation networks and comprehensive biodiversity conservation planning in the YRB. [ABSTRACT FROM AUTHOR]

Analysis of spatiotemporal heterogeneity and evolutionary characteristics of agricultural land eco-efficiency is of great significance for achieving a rational use of natural resources and coordinated development of the agricultural economy as well as the ecological environment. In this study, we construct the "ecological space–agricultural production–carbon emission" framework, incorporate carbon emission intensity as an undesired output into the evaluation index system of agricultural land eco-efficiency, calculate the eco-efficiency of agricultural land in 128 cities in the Yangtze River basin from 2009 to 2018 by adopting the super-efficiency SBM model, and discuss the spatial and temporal changes using methodology such as hotspot analysis and kernel density estimation by ArcGIS. The results show the following. The overall trend of agricultural land eco-efficiency in the Yangtze River basin is increasing year by year and still has potential for improvement. However, there are significant discrepancies among cities, with the eco-efficiency of the downstream being much higher than that of the midstream and upstream regions, and demonstrating the pattern of "big dispersion–small agglomeration". Some cities are still facing pressure to improve the eco-efficiency of agricultural land. Correspondingly, this paper puts forward optimization recommendations: Firstly, the downstream cities should give full play to their geographical advantages, actively introduce advanced production technologies, and reasonably allocate agricultural resources. Secondly, the upstream and midstream regions should formulate reasonable regional strategies in accordance with their natural resource endowments to improve the ecological benefits of agricultural land and narrow the regional disparities. This paper gives targeted policy recommendations at the levels of paying attention to education of farmers, providing incentives for ecological planting, strengthening agricultural infrastructure construction, reasonably controlling the use of agricultural materials, and increasing investment in agricultural pollutant emission management. [ABSTRACT FROM AUTHOR]

In view of the influence of the water conservancy project on the ecological environment along the coastal basin, this paper analyzes the characteristics of short-term runoff variation of the reservoir during and after the construction with the support vector machine. At the same time, a comprehensive evaluation system of the influence of the water conservancy project on the coastal basin is established to analyze the long-term influence of the the water conservancy project on the coastal basin. The conclusions are as follows: the support vector machine (SVM) can better simulate the situation of water passing in the coastal basin under complex conditions. During the construction of the dam, the water conservancy project has no significant influence on the runoff of this map in the Yangtze River basin, and the environment and monthly flow of the region are significantly affected within one year after the completion of the dam, which has obvious peak-cutting and valley-filling effect on the coastal basin and can suppress the emergence of floods. The long-term monitoring results of the project after its completion show that the ecological economy around the water conservancy project is mainly affected by the abundance of animals and plants and the distribution of groundwater, while the climate has less influence on the eco-economy. The water resources in the coastal basin are artificially controlled, which can effectively promote the local economic development. The power generation, farmland irrigation and water use in the upstream of the reservoir are satisfied, but the groundwater level is continuously lowered due to the continuous decrease of the water discharge in the lower reaches of the water conservancy project. The ecological environment of the lower reaches has been damaged to varying degrees. [ABSTRACT FROM AUTHOR]

The Yangtze River Basin experienced a once-in-a-century extreme drought in 2022 due to extreme weather, which had a serious impact on the local agricultural production and ecological environment. In order to investigate the spatial distribution and occurrence of the extreme drought events, this study used multi-source remote sensing data to monitor the extreme drought events in the Yangtze River Basin in 2022. In this study, the gravity satellite data product CSR_Mascon was used to calculate the GRACE Drought Intensity Index (GRACE-DSI), which was analyzed and compared with the commonly used meteorological drought indices, relative soil humidity, and soil water content data. The results show that (1) terrestrial water storage change data can well reflect the change in water storage in the Yangtze River Basin. Throughout the year, the average change in terrestrial water storage in the Yangtze River Basin from January to June is higher than the average value of 33.47 mm, and the average from July to December is lower than the average value of 48.17 mm; (2) the GRACE-DSI responded well to the intensity and spatial distribution of drought events in the Yangtze River Basin region in 2022. From the point of view of drought area, the Yangtze River Basin showed a trend of extreme drought increasing first, and then decreasing in the area of different levels of drought, and the range of drought reached a maximum in September with a drought area of 175.87 km2, which accounted for 97.71 per cent of the total area; at the same time, the area of extreme drought was the largest, with an area of 85.69 km2; (3) the spatial and temporal variations of the GRACE-DSI and commonly used meteorological drought indices were well correlated, with correlation coefficients above 0.750, among which the correlation coefficient of the SPEI-3 was higher at 0.937; (4) the soil moisture and soil relative humidity products from the CLDAS, combined with soil moisture products from the GLDAS, reflect the starting and ending times of extreme drought events in the Yangtze River Basin in 2022 well, using the information from the actual stations. In conclusion, gravity satellite data, analyzed in synergy with data from multiple sources, help decision makers to better understand and respond to drought. [ABSTRACT FROM AUTHOR]

With the continuous warming of the global climate, the ecological environment and water resources in the Yangtze River Basin are apt to be affected. The analysis and study of the future precipitation change trend in the region will help to provide a theoretical basis for water resources management and ecological protection in the Yangtze River Basin. Based on the observed precipitation data and precipitation data output from 13 global climate models of the Sixth International Coupled Model Comparison Program (CMIP6) with bias correction, this paper evaluates the precipitation simulation ability of climate models in the Yangtze River Basin from 1995 to 2014. The temporal and spatial variation trends of precipitation in 2021-2040 (near term), 2041-2070 (middle term), and 2071-2100 (long term) are analyzed under four SSP scenarios (SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5). The results show that: ① The model data with bias correction can simulate the characteristics of precipitation well in the Yangtze River Basin on the spatial and temporal scale, which is close to the observed values. ② The annual precipitation in the Yangtze River Basin will increase significantly with the increase in the radiation forcing level. Compared with the historical period (1995-2014), the annual precipitation growth in each scenario is relatively flat in the near term, and the precipitation growth is the largest in the long term. In general, seasonal precipitation shows the largest increase in winter, and the increase in spring and summer precipitation is relatively gentle. In autumn, except for the negative value of the precipitation change rate in the near term under the scenario SSP3-7.0, the other scenarios and periods are slowly increasing with lower change rates. ③ Spatially, the regions with larger annual precipitation increase are concentrated on the source region of the Yangtze River and the middle and upper reaches of the Yangtze River with relatively less precipitation. The high value center of spring precipitation increase is in the source area and the north of the middle and upper reaches, while the precipitation change rate is low in the south of the basin. The precipitation increment in summer and autumn is relatively low, and the near term and middle-term precipitation in the northern part of the middle and upper reaches is lower than that in the historical period. In winter, the precipitation in the whole basin has increased, which shows that the precipitation change rate in the north of the Yangtze River Basin is the largest, and it is smaller in the south. [ABSTRACT FROM AUTHOR]

[Display omitted] • A water-type classification procedure integrating shape, landscape patterns, topography, and phenology was proposed. • The distribution and transition of various wetlands in the middle and lower reaches of the Yangtze River Basin were mapped. • Nearly half of the wetlands experienced a significant trend of decrease in water inundation frequency from 1990 to 2020. • Farmland reclamation was the primary anthropogenic factor in natural wetland loss and degradation. Wetlands are crucial to diverse societies and ecosystems but are threatened globally. Natural wetlands in the middle and lower reaches of the Yangtze River Basin (MLRYRB) have long been exploited to meet the increasing food and energy demands, especially in recent decades. However, how their landscapes and hydrological patterns changed over time was poorly qualified, which was crucial to conserving biodiversity and ecosystems. In this study, we proposed a new wetland classification procedure taking advantage of the shape, topography, landscape patterns, and phenology to map the distribution of six wetland types in the MLRYRB in 1990 and 2020 with Landsat images. The transitions among different wetland types and associated driving factors were examined. Artificial wetlands expanded by 3907.6 km2 while natural wetlands decreased by 423.2 km2, resulting in a net area increase of 3484.4 km2. Farmland reclamations, aquacultural activities, urban expansion, and dam constructions induced 70 % of the area's loss of natural wetlands. Meanwhile, spatiotemporal patterns in wetland inundation dynamics were determined with agglomerative hierarchical cluster analysis. Widespread transitions from perennial water to seasonal wetlands were detected. Notably, 47.8 % of the natural wetlands experienced significant drying trends, and as a result, the mean yearly inundated periods for natural wetlands decreased from 303 days in 1990 to 272 days in 2020. Given the substantial structural alterations, wetland destruction was more severe than the area reflected. Our results suggested that category-based changes in wetland areas, inundation patterns, associated driving forces, and underlying ecological consequences should be comprehensively assessed to conduct scientific conservation and prevent "paper offsets." [ABSTRACT FROM AUTHOR]

Terrestrial gross primary production (GPP) changes due to impervious surfaces significantly impact ecosystem services in watersheds. Understanding the asymmetric response of vegetation GPP to impervious surface expansion is essential for regional development planning and ecosystem management. However, the asymmetric response of vegetation GPP to the impacts of impervious surface expansion is unknown in different watersheds. This paper selected the Yellow River and Yangtze River basins as case studies. We characterized the overall change in GPP based on changes in impervious surface ratio (ISR), determined impervious surface expansion's direct and indirect impacts on GPP in the two watersheds, and further analyzed the asymmetric response of the compensatory effects of indirect influences on the impervious surface expansion in different watersheds. The results showed that: (1) The vegetation GPP decreased with increasing ISR in the Yangtze River Basin, while that in the Yellow River Basin first increased and then reduced. (2) The direct impacts of increased ISR reduced vegetation GPP, while the indirect impacts both had a growth-compensating effect. Growth compensation stabilized at approximately 0.40 and 0.30 in the Yellow and Yangtze River Basins. (3) When the ISR was 0.34–0.56, the growth compensation could offset the reduction of GPP due to direct impact and ensure that the background vegetation GPP was not damaged in the Yellow River Basin. In contrast, the background vegetation GPP was inevitably impaired with increased ISR in the Yangtze River Basin. Therefore, this study suggests that the ISR should be ensured to be between 0.34 and 0.56 to maximize the impervious surface of the Yellow River Basin without compromising the background vegetation GPP. While pursuing impervious surface expansion in the Yangtze River Basin, other programs should be sought to compensate for the loss to GPP. [Display omitted] • Vegetation GPP decreases with an increase in the impervious surface ratio. • Indirect impacts in different watersheds have growth compensation effects. • Growth compensation can offset the reduction in GPP caused by direct impacts in the Yellow River Basin. • Background vegetation GPP inevitably impairs as impervious surfaces increase in the Yangtze River Basin. [ABSTRACT FROM AUTHOR]

Currently, the manufacturing development in Yangtze River Basin is featured by high energy consumption and high pollution. This consumes lots of energy and creates severe environmental pollution. For the sustainable development of manufacturing, it is necessary to scientifically evaluate the manufacturing energy efficiency of Yangtze River Basin. In this paper, the suitable metrics are firstly selected to evaluate the manufacturing energy efficiency (MEE) under environmental constraints. Then, the panel data 2010–2018 on the manufacturing of the 11 regions of the Yangtze River Basin were taken as the object. On this basis, the MEE in the Belt was analyzed statically and dynamically with the slack-based measure (SBM) model and Malmquist-Luenberger metric, respectively. In addition, the Tobit model was adopted for regression analysis on how various factors affect the Belt MEE. The results show that: the MEEs in the Belt were severe polarized, with significant differences between regions; in most regions, the ML was improved to varied degrees in the sample interval; comparatively, technological progress boasts stronger promoting effect than technical efficiency improvement; the Belt MEE is significantly promoted by technological innovation, foreign trade, and environmental regulation, significantly suppressed by property-right structure and energy price, and not significantly affected by industrial structure or energy structure. [ABSTRACT FROM AUTHOR]

A rare compound hot and drought (CHD) event occurred in the Yangtze River Basin (YRB) in the summer of 2022, which brought serious social crisis and ecological disaster. The analysis of the causes, spatiotemporal characteristics and impacts of this event is of great significance and value for future drought warning and mitigation. We used the Gravity Recovery and Climate Experiment (GRACE)/GRACE Follow-On (GRACE-FO) data, meteorological data, hydrological data and satellite remote sensing data to discuss the spatiotemporal evolution, formation mechanism and the influence of the CHD event. The results show that the drought severity caused by the CHD event was the most severe during 2003 and 2022. The CHD event lasted a total of five months (from July to November), and there were variations in the damage in different sub-basins. The Wu River Basin (WRB) is the region where the CHD event lasted the longest, at six months (from July to December), while it also lasted four or five months in all the other basins. Among them, the WRB, Dongting Lake Rivers Basin (DLRB) and Mainstream of the YRB (MSY) are the three most affected basins, whose hot and drought severity values are 7.750 and −8.520 (WRB), 7.105 and −9.915 (DLRB) and 6.232 and −9.143 (MSY), respectively. High temperature and low precipitation are the direct causes of the CHD event, and the underlying causes behind this event are the triple La Niña and negative Indian Ocean Dipole event. The two extreme climate events made the Western Pacific Subtropical High (WPSH) unusually strong, and then the WPSH covered a more northerly and westerly region than in previous years and remained entrenched for a long period of time over the YRB and its adjacent regions. Moreover, this CHD event had a devastating impact on local agricultural production and seriously disrupted daily life and production. Our results have implications for the study of extreme disaster events. [ABSTRACT FROM AUTHOR]

A holistic understanding of the magnitude and long-term trend of water vulnerability is essential for making management decisions in a given river basin. Existing procedures to assess the spatiotemporal dynamic of water vulnerability in complex mega-scale river basins are inadequate; a new method named ensemble hydrologic assessment was proposed in this study, which allows collection of data and knowledge about many aspects of water resources to be synthesized in a useful way for vulnerability assessment. The objective of this study is to illustrate the practical utility of such an integrated approach in examining water vulnerability in the Yangtze River Basin. Overall, the results demonstrated that the ensemble hydrologic assessment model could largely explain the spatiotemporal evolution of water vulnerability. This paper improves understanding of the status and trends of water resources in the Yangtze River Basin. [ABSTRACT FROM AUTHOR]

This paper explored the drought propagation phenomenon based on meteorological, hydrological, and agricultural aspects in the Yangtze River basin (YRB), China. To evaluate meteorological, hydrological, and agricultural droughts, this paper used three drought indices, standardized precipitation evapotranspiration index (SPEI), standardized runoff index (SRI), and standardized soil moisture index (SSMI), respectively. The community land model (CLM) in the YRB to generate the monthly evapotranspiration, soil moisture, runoff data, which are required for the estimation of drought index, were applied. Different mean durations (6-and 12-month) were used for drought estimation, and propagations of meteorological to hydrological and meteorological and agricultural droughts were investigated for different durations as SPEI6-SRI6, SPEI6-SSMI6, SPEI12-SRI12, SPEI12-SSMI12. The average drought propagation between 1950 and 2010 presented the highest autocorrelation and correlation with one-month lags in four combinations of drought indices in SPEI6-SRI6, SPEI6-SSMI6, SPEI12-SRI12, and SPEI12-SSMI12. Additionally, this paper estimated the optimal lags of SPEI-SRI and SPEI-SSMI drought propagations using mean 6-and 12-month lag times for six representative drought periods. Therefore, the propagation phenomenon of meteorological to hydrological and to agricultural droughts were confirmed in the YRB. • SPEI, SRI, and SSMI indices have been applied to the Yangtze River basin (YRB). • Propagation analysis of SPEI-SRI and SPEI-SSMI have extended to 1951–2010. • Mean 12-month duration shows clearer drought propagation than mean 6-month duration. • SPEI-SSMI presents 1–7 months propagation time. • SPEI-SRI presents 1–2 months propagation time. [ABSTRACT FROM AUTHOR]

In this study, we conducted an analysis of the CN05.1 daily precipitation observation dataset spanning from 1985 to 2014. Subsequently, we ranked the 30 global climate model datasets within the NEX-GDDP-CMIP6 dataset using the RS rank score method. Multi-model weighted-ensemble averaging was then performed based on these RS scores, followed by a revision of the multi-model weighted-ensemble averaging (rs-MME) using the quantile mapping method. The revised rs-MME model data were utilized for simulating precipitation variations within the Yangtze River Basin. We specifically selected 11 extreme-precipitation indices to comprehensively evaluate the capability of the revised rs-MME model data in simulating extreme-precipitation occurrences in the region. Our investigation culminated in predicting the characteristics of precipitation and the potential shifts in extreme-precipitation patterns across the region under three distinct shared socioeconomic pathways (SSP1-2.6, SSP2-4.5, and SSP5-8.5) for three temporal segments: the Near 21C (2021–2040), Mid 21C (2041–2070), and Late 21C (2071–2100). Our findings reveal that the revised rs-MME model data effectively resolve the issues of the overestimation and underestimation of precipitation data present in the previous model. This leads to an enhanced simulation of mean annual precipitation, the 95th percentile of precipitation, and the extreme-precipitation index for the historical period. However, there are shortcomings in the simulation of linear trends in mean annual precipitation, alongside a significant overestimation of the CWD and CDD indices. Furthermore, our analysis forecasts a noteworthy increase in future mean annual precipitation within the Yangtze River Basin region, with a proportional rise in forced radiation across varying scenarios. Notably, an ascending trend of precipitation is detected at the headwaters of the Yangtze River Basin, specifically under the Late 21C SSP5-8.5 scenario, while a descending trend is observed in other scenarios. Conversely, there is an escalating pattern of precipitation within the middle and lower reaches of the Yangtze River Basin, with most higher-rate changes situated in the middle reaches. Regarding extreme-precipitation indices, similar to the annual average precipitation, a remarkable upsurge is evident in the middle and lower reaches of the Yangtze River Basin, whereas a relatively modest increasing trend prevails at the headwaters of the Yangtze River Basin. Notably, the SSP5-8.5 scenario portrays a substantial increase in extreme-precipitation indices. [ABSTRACT FROM AUTHOR]

Active accumulated temperature is an important index of agricultural heat resources in a region. Based on the temperature data of the Yangtze River Basin from 1970 to 2014, this paper analyzed the characteristics of the temporal and spatial variations of the biological boundary temperature in the Yangtze River Basin. The main conclusions were drawn as follows: (1) since 1970, the accumulated temperature of ≥0 °C in the northern subtropical zone, mid-subtropical zone, and plateau climate zone showed overall increasing trends, and the trends were 122 (p < 0.001), 87.7 (p < 0.001), and 75.3 °C/10a (p < 0.001), respectively. The accumulated temperature of ≥5 °C showed an upward trend, and the change tendency rates were 122.6 (p < 0.001), 90.5 (p < 0.001), and 81.4 °C/10a (p < 0.001), respectively. The accumulated temperature of ≥10 °C showed overall increasing trends and the trends were 115.7 (p < 0.001), 92.5 (p < 0.001), and 78.9 °C/10a (p < 0.001). Accumulated temperatures of ≥0 °C, ≥5 °C, and ≥10 °C in the northern subtropical zone increased significantly higher than that in the mid-subtropical zone and plateau climate zone. (2) The accumulated temperatures of ≥0 °C, ≥5 °C, and ≥10 °C in the northern subtropical zone showed an abrupt change in 1997. In the mid-subtropical zone and plateau climate zone, there was an abrupt change in the accumulated temperatures of ≥0 °C and ≥5 °C in 1994, and in the northern subtropical zone, the abrupt change of the accumulated temperature ≥10 °C occurred in 1998. (3) There are obvious differences in the biological boundary temperature within the Yangtze River Basin, and the stations with large increases are mainly distributed in the middle and lower reaches, such as the Hanshui Basin, the Poyang Lake Basin, the Taihu Lake Basin, and the middle and lower reaches of the mainstream area. The initial day, final day, and continuous days showed a trend of advancement, postponement, and extension, respectively. Besides, the heat resources showed significant increasing trends, which is of guiding significance for the future production and development of agriculture in the region. With the increase of heat resources in the Yangtze River Basin, appropriate late-maturing varieties should be selected in variety breeding, to make full use of heat resources and improve the quality of agricultural products. Secondly, the planting system should be adjusted and the multiple cropping index improved to steadily increase agricultural output. This brings new opportunities to adjust the structure of the agricultural industry and increase farmers' income, in the Yangtze River basin. [ABSTRACT FROM AUTHOR]

Quantification of the relationship between agricultural water use and social development is important for the balance between conserving water resources and sustainable economic development. The agricultural water footprint (AWF) from crop production across 11 provinces in the Yangtze River Basin (YRB) of China, from 1999 to 2018, was calculated in the current paper. The driving factors which affected the provincial AWF were revealed using the logarithmic mean Divisia index (LMDI) model, based on a temporal and spatial variation assessment. The results showed that, with a growth rate of 1.95% per year, the annual AWF of the in the basin was 441.6 Gm3 (green water accounted for 73.63% of this) in the observed two decades. The Jiangsu, Anhui, Hubei and Sichuan provinces jointly accounted for 54% of the total AWF of the region. Cereal, cotton and fruit crops contributed most of the AWF, and determined the trends of the AWF over time. With the development of the economy and market demand, the dominant crop contributing to the AWF has shifted, from cereal and cotton around 2000, to cereals and fruits at present. The economic level was the main contributing factor driving the AWF. However, water use intensity was the most important factor which inhibited the growth of the AWF. Irrigation technology and the degree of urbanization also played a certain inhibitory role. There were significant differences in the driving effects among the different provinces. A comprehensive evaluation of the AWF and analysis of its driving factors provides a solid foundation for optimizing planting structure, strengthening water resource management, and enhancing regional exchanges and cooperation. [ABSTRACT FROM AUTHOR]

Sun, X.-P.; He, S.-M.; Guo, Y.; Sima, W.-P., and Liu, W.-F., 2019. Comprehensive evaluation of the impact of the water conservancy project in on the ecosystem of the yangtze river basin. In: Gong, D.; Zhu, H., and Liu, R. (eds.), Selected Topics in Coastal Research: Engineering, Industry, Economy, and Sustainable Development. Journal of Coastal Research, Special Issue No. 94, pp. 758–762. Coconut Creek (Florida), ISSN 0749-0208. In view of the influence of the water conservancy project on the ecological environment along the coastal basin, this paper analyzes the characteristics of short-term runoff variation of the reservoir during and after the construction with the support vector machine. At the same time, a comprehensive evaluation system of the influence of the water conservancy project on the coastal basin is established to analyze the long-term influence of the the water conservancy project on the coastal basin. The conclusions are as follows: the support vector machine (SVM) can better simulate the situation of water passing in the coastal basin under complex conditions. During the construction of the dam, the water conservancy project has no significant influence on the runoff of this map in the Yangtze River basin, and the environment and monthly flow of the region are significantly affected within one year after the completion of the dam, which has obvious peak-cutting and valley-filling effect on the coastal basin and can suppress the emergence of floods. The long-term monitoring results of the project after its completion show that the ecological economy around the water conservancy project is mainly affected by the abundance of animals and plants and the distribution of groundwater, while the climate has less influence on the eco-economy. The water resources in the coastal basin are artificially controlled, which can effectively promote the local economic development. The power generation, farmland irrigation and water use in the upstream of the reservoir are satisfied, but the groundwater level is continuously lowered due to the continuous decrease of the water discharge in the lower reaches of the water conservancy project. The ecological environment of the lower reaches has been damaged to varying degrees. [ABSTRACT FROM AUTHOR]

Global climate change and human activities have increased the frequency and severity of droughts. This has become a critical factor affecting vegetation growth and diversity, resulting in detrimental effects on agricultural production, ecosystem stability, and socioeconomic development. Therefore, assessing the response of vegetation dynamics to drought can offer valuable insights into the physiological mechanisms of terrestrial ecosystems. Here, we applied long-term datasets (2001–2020) of solar-induced chlorophyll fluorescence (SIF) and normalized difference vegetation index (NDVI) to unveil vegetation dynamics and their relationship to meteorological drought (SPEI) across different vegetation types in the Yangtze River Basin (YRB). Linear correlation analysis was conducted to determine the maximum association of SPEI with SIF and NDVI; we then compared their responses to meteorological drought. The improved partial wavelet coherence (PWC) method was utilized to quantitatively assess the influences of large-scale climate patterns and solar activity on the relationship between vegetation and meteorological drought. The results show that: (1) Droughts were frequent in the YRB from 2001 to 2020, and the summer's dry and wet conditions exerted a notable influence on the annual climate. (2) SPEI exhibits a more significant correlation with SIF than with NDVI. (3) NDVI has a longer response time (3–6 months) to meteorological drought than SIF (1–4 months). Both SIF and NDVI respond faster in cropland and grassland but slower in evergreen broadleaf and mixed forests. (4) There exists a significant positive correlation between vegetation and meteorological drought during the 4–16 months period. The teleconnection factors of Pacific Decadal Oscillation (PDO), El Niño Southern Oscillation (ENSO), and sunspots are crucial drivers that affect the interaction between meteorological drought and vegetation, with sunspots having the most significant impact. Generally, our study indicates that drought is an essential environmental stressor that disrupts vegetation growth over the YRB. Additionally, SIF demonstrates great potential in monitoring vegetation response to drought. These findings will be meaningful for drought prevention and ecosystem conservation planning in the YRB. [ABSTRACT FROM AUTHOR]

Tourism ecological security (TES) has gradually become a frontier topic because it is related to the virtuous circle of ecosystems and sustainable development, especially in river basins with fragile ecosystems. Based on the Driver–Pressure–State–Impact–Response (DPSIR) model and open systems theory, we constructed a TES evaluation system in the Yellow River Basin (YRB), China. Then, the TES index was measured from 2004 to 2019 and its spatio-temporal characteristics and driving mechanism were analyzed. The results show that: (1) In terms of temporal evolution, the comprehensive TES index shows a steady upward trend, but the difference between cities increases over time. Moreover, the proportion of cities with low status levels of TES declined rapidly, while the proportion of cities with high status levels of TES has grown slowly. (2) Spatially, low-TES value cities have always been in the majority, and the high-value cities show a scattered spatial distribution, most of which are along the river. Moreover, TES is randomly distributed in space before 2013, but it shows a significant positive spatial clustering feature thereafter. Specifically, the range of hot spots extends from the intersection of the middle and upper reaches to downstream, while the cold spots are always scattered. Furthermore, the trend surface in the east–west direction is always smooth, while it gradually manifests an inverted U-shape in the north–south direction. (3) In the dynamic transfer, TES lacks the vitality of transfer, but the probability of shifting upward becomes more significant when adjacent to higher-level cities; the opposite is true when adjacent to lower-ranked cities. (4) In terms of the driving mechanism, the factors related to tourism and the economy are the most important driving forces, and the effect of tourism-related factors on TES is becoming increasingly significant. Moreover, the driving mechanism is constructed. Finally, this study provides targeted policy implications for improving TES in the YRB, which has reference value for the development of ecological protection and high-quality tourism. [ABSTRACT FROM AUTHOR]

Locally evaporated water vapor is an important source of precipitation in China. The spatiotemporal variation characteristics of the precipitation recycling ratio (ρ) in the Yangtze River Basin (YRB) in 1979–2020 were calculated and analyzed, and the contribution of internal and external cycling precipitation changes to the total precipitation changes in YRB under climate change was studied. The results show that the annual average ρ in YRB is approximately 10.3%, with the highest value of 21.8% in summer, lower than 10% in spring and autumn, and the lowest in winter, with only approximately 3.5%. Over the past 40 years, the annual average ρ in YRB has shown an increasing trend, with an increased rate of 0.4%/10a, especially in summer, with an increasing rate of 1.2%/10a. In terms of spatial distribution, ρ in YRB shows an obvious difference between the eastern and western regions, with that in the upstream western region being significantly higher than that in the downstream eastern region. The annual average ρ in the upstream region was 15–35% and can reach 20–50% in summer. The annual average ρ in the downstream region is below 10%. In general, precipitation formed by advection moisture accounts for the majority of the total precipitation in YRB. From 1979 to 2020, the annual precipitation in YRB showed an increasing trend. The cumulative increase is about 47.4 mm, of which 68.9% was contributed by local evaporation, and 31.1% was contributed by external moisture. [ABSTRACT FROM AUTHOR]

Satellite geodetic technologies, such as the Global Navigation Satellite System (GNSS), Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-On (GFO), have complementary advantages in inferring terrestrial water storage (TWS) changes at regional and basin scales. We introduced a joint inversion strategy to infer TWS changes using GNSS- and GRACE/GFO-derived vertical displacements based on Green's function theory in the Yangtze River Basin (YRB) from January 2011 to December 2020. Additionally, we investigated the performance of variance component estimation (VCE) and Akaike's Bayesian Information Criterion (ABIC) to determine the optimal relative weights of different observation data. The performance of our joint inversion strategy was verified through a closed-loop simulation and multi-source hydrometeorological data [i.e. the time derivative of TWS changes (⁠|${\rm d}S/{\rm d}t$|⁠) from precipitation (P), evapotranspiration (ET) and run-off (R) based on the water balance equation, called P-ET-R]. The closed‐loop simulation shows that the TWS changes from joint inversion have better consistencies with the synthetic signals than those of GNSS- and GRACE-only estimates, and the corresponding root mean square error (RMSE) decreased 1.43−6.28 mm and correlation coefficient (CC) increased 3−10 per cent. The ABIC was more suitable for the joint inversion of measured GRACE/GFO and GNSS data for TWS changes in the YRB. Analysis from the measured data shows that the spatial patterns and seasonal characteristics in TWS changes derived from GNSS, GRACE/GFO and their joint inversion are in good agreement in the YRB. The contribution of GNSS observations to the joint inversion in the upstream of the YRB is greater than that of GRACE/GFO due to the relatively densely distributed GNSS stations, but the opposite is true in the downstream. Furthermore, the joint inversion results have better agreements with P and P-ET-R compared to GNSS- and GRACE/GFO-only estimates in the upstream, and the corresponding CCs increased 5−7 per cent (for P) and 2−5 per cent (for P-ET-R), respectively, which further demonstrates the effectiveness of our joint inversion strategy. Our estimation strategy provides a new insight for joint inversion of GNSS and GRACE/GFO data to obtain more reliable TWS changes. [ABSTRACT FROM AUTHOR]

The Yangtze River Basin is a resource axis represented by hydropower resources, bulk agricultural products, and mining resources. However, with rapid socio-economy development, the balance between water, energy, and food elements in the region has become more fragile. As the core element of the water-energy-food nexus, it is necessary to study water resources security and give effective pre-warning of possible water safety problems from the perspective of water-energy-food symbiosis. In this paper, we introduce the "symbiosis theory" to build a regional water-energy-food nexus symbiosis framework. Then, we establish a Lotka–Volterra symbiotic evolution model to calculate the symbiotic security index. Finally, we judge the water security state and pre-warning level and analyze the causes of water security problems by the inverse decoupling of the indicator-index. The results show that the spatial differentiation of water security in the Yangtze River Basin is obvious from the perspective of water-energy-food symbiosis. The state of water security in the middle and upper reaches of the Yangtze River Basin is better than that in the lower reaches. Specifically, the water resources security levels in the upstream hydropower energy enrichment regions are generally low. By contrast, the water systems of some downstream socio-economically developed provinces have certain risks. Therefore, each province needs to find out the key factors that hinder the healthy development of the water resources system based on combining the evolution mechanism and symbiotic state of water-energy-food so that water security can be managed in a targeted manner. [ABSTRACT FROM AUTHOR]

Owning to the nature of flood events, near-real-time flood detection and mapping is essential for disaster prevention, relief, and mitigation. In recent years, the rapid advancement of deep learning has brought endless possibilities to the field of flood detection. However, deep learning relies heavily on training samples and the availability of high-quality flood datasets is rather limited. The present study collected 16 flood events in the Yangtze River Basin and divided them into three categories for different purpose: training, testing, and application. An efficient methodology of dataset-generation for training, testing, and application was proposed. Eight flood events were used to generate strong label datasets with 5296 tiles as flood training samples along with two testing datasets. The performances of several classic convolutional neural network models were evaluated with those obtained datasets, and the results suggested that the efficiencies and accuracies of convolutional neural network models were obviously higher than that of the threshold method. The effects of VH polarization, VV polarization, and the involvement of auxiliary DEM on flood detection were investigated, which indicated that VH polarization was more conducive to flood detection, while the involvement of DEM has a limited effect on flood detection in the Yangtze River Basin. Convolutional neural network trained by strong datasets were used in near-real-time flood detection and mapping for the remaining eight flood events, and weak label datasets were generated to expand the flood training samples to evaluate the possible effects on deep learning models in terms of flood detection and mapping. The experiments obtained conclusions consistent with those previously made on experiments with strong datasets. [ABSTRACT FROM AUTHOR]

The sustainable development of the water environment in the Yangtze River basin has become a critical issue in China. Turbidity is a comprehensive element for water quality monitoring. In this study, the baseline of water turbidity in the Yangtze River was constructed using 36 years of Landsat images from 1986 to 2021. The spatial and temporal dynamics of turbidity and its driving factors were explored. The results show that (i) the proposed Landsat-based turbidity model performs well, with a correlation coefficient (R2) of 0.68 and a Root Mean Square Error (RMSE) of 7.83 NTU for the whole basin. (ii) The turbidity level in the Yangtze River basin is spatially high in the upper reaches (41.7 NTU), low in the middle reaches (30.9 NTU), and higher in the lower reaches (37.6 NTU). The river turbidity level (60.1 NTU) is higher than the turbidity in lakes and reservoirs (29.6 NTU). The turbidity in the Yangtze River basin shows a decreasing trend from 1986 to 2021, with the most significant decrease in the mainstream of the Yangtze River. Seasonally, the mean turbidity in the Yangtze River basin shows a "low in summer and high in winter" trend, but opposite trends were revealed for the first time in rivers and lakes, such as Dongting Lake, Poyang Lake, and Taihu Lake, etc. (iii) Natural factors, including precipitation and natural vegetation cover (woodlands, grasslands, and shrubs) could explain 58% of the turbidity variations, while human activities including impervious surfaces, cropland, and barren land are lower impact. Annual precipitation was negatively correlated with water turbidity, while cropland and barren land showed a significant positive correlation. The study is of great practical value for the sustainable development of the water environment in the Yangtze River basin and provides a reference for remote sensing monitoring of the water environment in inland water bodies. [ABSTRACT FROM AUTHOR]

Taxodium hybrid Zhongshanshan has been widely planted in the Yangtze River Basin (YRB) for soil and carbon conservation, with quantities over 50 million. The objective of this study was to determine how T. hybrid Zhongshanshan plantations affected soil physicochemical properties and bacterial community structure in the YRB, and to examine the consistency of changes by afforestation. Soils under T. Zhongshanshan plantations across six sites of the YRB were compared with soils of adjacent non-forested sites. Soil physicochemical properties and bacterial community structure were determined to clarify edaphic driving factors and reveal the effects of afforestation on bacteria. The results indicated that most soil attributes manifested improvements, e.g., total nitrogen in Jiangxi and Shanghai; available phosphorus in Hubei, Chongqing and Yunnan, exhibited the potential to maintain or ameliorate soil quality. A decrease in soil bulk density caused by plantation was also observed at the expense of soil macro-aggregates augment. Afforestation of T. Zhongshanshan plantation has habitually improved Shannon diversity and Chao1 richness, of which dominant phyla were Proteobacteria, Acidobacteria, and Actinobacteria, and increased the relative abundance of the phyla Proteobacteria and Nitrospirae, and the classes Flavobacteriia, Acidobacteria_Gp5, and Bacilli. We concluded that T. Zhongshanshan plantation can be employed to facilitate soil nutrient accumulation in the YRB, but that the degree, rate and direction of changes in soil attributes are sites dependent. It is recommended that afforestation of nutrient-depleted and less productive lands in the YRB should utilize this fast-growing species in combination with proper fertilization. [ABSTRACT FROM AUTHOR]

Using a dataset of 114 meteorological stations in the Yangtze River Basin from 1980–2019, the standardized precipitation evapotranspiration index (SPEI) was calculated based on the Penman-Monteith evapotranspiration model for multiple time scales, and the spatial and temporal evolution characteristics and driving factors of drought in the Yangtze River Basin were analyzed by combining spatial and temporal analysis methods as well as geodetector. The main results obtained are as follows: (1) The climate of the Yangtze River Basin is an overall wet trend, and the trend of summer drought is more similar to the annual scale trend. (2) Most areas in the Yangtze River Basin showed mild drought or no drought, and there is little difference in drought condition among the Yangtze River Basin regions. The areas with drought conditions are mainly distributed in the southwest and east of the Yangtze River Basin. (3) There are significant seasonal differences in drought conditions in all regions, and the drought condition is more different in autumn compared to spring, summer and winter. (4) The average annual precipitation and elevation factors are the dominant driving factors of drought in the Yangtze River Basin, and the double-factor interaction has a greater influence on the drought variation in the Yangtze River Basin than the single-factor effect, indicating that the difference of drought condition in the Yangtze River Basin is the result of the combination of multiple factors. [ABSTRACT FROM AUTHOR]

To better understand the mechanisms of the hydro-ecological cycle in the changing environments of the Yangtze River Basin (YZRB), it is valuable to investigate vegetation dynamics and their response to climate change. This study explored the spatial patterns of vegetation dynamics and the essential triggers of regional differences by analyzing vegetation variations in the 1982–2015 period at different time scales and the interannual variability of vegetation sensitivity to climate variability. The results showed that the normalized difference vegetation index (NDVI) increased significantly in the last three decades, but vegetation displayed great spatiotemporal variations at different time scales. The vegetation in the central part of the YZRB dominated by forests and shrublands was more sensitive to climate variability than vegetation in the source region of the YZRB, which was dominated by alpine meadows and tundra (AMT). The contribution of climate variables to the vegetation sensitivity index (VSI) had large spatial differences, but solar radiation and temperature were the dominant factors. Furthermore, 57.9% of the YZRB had increasing VSIs, especially in the south-central part. Consistent with the distributions of elevation and vegetation types, vegetation dynamics in the YZRB were divided into five spatial patterns, with the largest increasing NDVI trend in Region III and the largest VSI in Region IV. Moreover, the VSI exhibited fairly consistent dynamics in all subregions, but the contributions of climate variables to the VSI varied greatly among the different regions. [ABSTRACT FROM AUTHOR]

Numerous studies have divided industrial water use system into stages of industrial water use (IWU) and wastewater treatment (IWT) subsystems, named as the IWUWT system, yet scant studies have examined its dynamic recycling efficiency with non-discretionary variables. This paper proposes a dynamic two-stage recycling model with non-discretionary variables to compare and analyze the basin differences of the efficiency, and further reveal the driving forces of this efficiency in the Yangtze River basin and Yellow River basin. The results are as follows. (1) The average overall efficiency of the IWUWT system for the 30 provinces during 2011–2018 was 0.79 due to the bad performance of the IWT subsystem with an efficiency score of 0.74, especially for Yunnan and Guangxi. (2) The influence of economic policy uncertainty on circulating industrial water use is more significant in the south basin. (3) Economic development and water use intensity were the main drivers of IWUWT efficiency in the Yangtze River basin, while economic development and environmental consciousness were for the Yellow River basin. The results have important implications for Chinese government and different provinces to improve IWUWT efficiency by policy-making. • A dynamic two-stage recycling model with non-discretionary variables is proposed. • Basin differences of the IWUWT efficiency and its stage efficiencies are provided. • Driving factors of the IWUWT efficiency in typical river basins are revealed. • The influences of EPU on IWUWT efficiency are highlighted. [ABSTRACT FROM AUTHOR]

Droughts resulting from global warming severely hamper the healthy development of terrestrial vegetation ecosystems. This paper defines a terrestrial vegetation ecological drought index, i.e., the Standardized Water Supply–Demand Index (SSDI), based on the water balance method using the same calculation model as the SPEI. The theory of run is used to analyze the spatial and temporal distribution of the drought characteristics in the Yangtze River Basin (YRB). The results show that (1) the drought events monitored by the SSDI were in good agreement with historical drought events, and the correlation coefficient between SSDI and NDVI (0.94) was significantly higher than that between SPEI and NDVI (0.88). (2) About 55.4% of the regions in the YRB experienced more than 13 droughts, and about 41.4% of the regions had an average drought duration of more than 3.1 months. In the northern part of the YRB, droughts tend to develop in a short-term high frequency, while in the southern part of the YRB, there is a long-term low-frequency development trend. Nearly 24.5% of the regions have an average drought intensity of more than 1.4, and most of them are located in the lower reaches of the Yangtze River. (3) Over the last 18 years, about 79.5% of the regions in the YRB showed an increasing trend in SSDI, of which 36.8% showed an increasing trend of more than 0.04/yr. In addition, 40.4% of the regions showed a significant upward trend. Precisely analyzing the spatiotemporal variation of drought characteristics in the YRB is critical for drought risk assessment and sustainable development of water resources and could provide a theoretical basis for effective water resource allocation and drought relief. • A new drought monitoring index, i.e., the Standardized Water Supply–Demand Index (SSDI) was defined. • SSDI can effectively monitor drought events. • SSDI is more suitable for monitoring ecological drought. • Drought of vegetation ecosystem in the Yangtze River Basin was assessed and analyzed with the SSDI. • It provides a theoretical basis for drought management and water allocation in the Yangtze River Basin. [ABSTRACT FROM AUTHOR]

For the day-by-day evaporation observation data in the Yangtze River Basin from 1951 to 2019, the effects of the gradual shift of observation instruments from 20 cm diameter evaporation pan (D20) to E601 evaporation pan after 1980 are discussed, including inconsistent data series, and missing and anomalous data. This study proposes a governance and improvement method for dual-source evaporation data (GIME). The method can accomplish the homogenization of data from different observation series and solve the problem of inconsistent and missing data, and we applied it in practice on data of the Yangtze River Basin. Firstly, the primary and secondary periods of the data were obtained by wavelet periodicity analysis; secondly, we considered the first cycle of observations to be representative of the sample and calculated the conversion relationship between the primary and secondary periods; thirdly, the conversion coefficient between the dual-source observations was calculated, and the results were corrected for stations outside the main cycle; finally, the daily evaporation dataset of E601 pan was established through data fusion and interpolation technology. The study found that the annual average conversion coefficients of the D20 and E601 pans in the Yangtze River Basin are basically between 0.55 and 0.80, and there are obvious differences in different regions. The conversion coefficient is positively correlated with relative humidity, wind speed, minimum temperature and altitude; and negatively correlated with sunshine duration, average temperature and maximum temperature. Evaporation is high in the upper reaches of the basin and low in the middle and lower reaches; in particular, evaporation is highest in the southwest, which is associated with the drought hazards. In addition, the article presents the spatial distribution of the conversion coefficients of D20 and E601 pans in the Yangtze River Basin. The results can realize the rapid correction of the evaporation data of the local meteorological department, and can be extended to the processing of other types of data in similar areas. [ABSTRACT FROM AUTHOR]

Net Primary Productivity (NPP) is a basis of material and energy flows in terrestrial ecosystems, and it is also an important component in the research on carbon cycle and carbon budget. This paper evaluated the spatial distribution pattern and temporal change trends for forest NPP simulated by the LPJ (Lund-Potsdam-Jena) model and NDVI (normalized difference vegetation index) in the Yangtze River basin from 1982 to 2013. The results revealed that: (1) the spatial distribution of the forest NPP and NDVI in the Yangtze River basin has gradually decreased from the southeast coast to the northwest. The forest NPP and NDVI in the mid-lower Yangtze were higher than that of the upper Yangtze; (2) the forest NPP and NDVI in most areas of the Yangtze River basin were positively correlated with the temperature and precipitation. Moreover, the correlations among the temperature with the forest NPP and NDVI were stronger than that of correlations among precipitation with forest NPP and NDVI. Moreover, the extreme drought event in the year of 2004–2005 led the NPP to decrease in the middle and lower Yangtze River basin; (3) human activity such as major ecological projects would have a certain impact on the NPP and NDVI. The increase in forest areas from 2000 to 2010 was larger than that from 1990 to 2000. Moreover, the increasing rate for the NDVI was higher than that of NPP, especially after the year 2000, which indicates that the major ecological projects might have great impacts on the vegetation dynamics. Moreover, more attention should be paid on the joint impacts of human activity and climate change on terrestrial NPP and NDVI. [ABSTRACT FROM AUTHOR]

This paper estimates the likely impacts of future climate change on streamflow, especially the hydrological extremes over the Yangtze River basin. The future climate was projected by the Coordinated Regional Climate Downscaling Experiment in East Asia (CORDEX-EA) initiative for the periods 2020–2049 under two representative concentration pathways (RCP) 4.5 and 8.5 emission scenarios. The bias corrected outputs from five regional climate models (RCMs) were used in conjunction with the variable infiltration capacity (VIC) macroscale hydrological model to produce hydrological projections. For the future climate of the Yangtze River basin, outputs from an ensemble of RCMs indicate that the annual mean temperature will increase for 2020–2049 by 1.81 °C for RCP4.5 and by 2.26 °C for RCP8.5. The annual mean precipitation is projected to increase by 3.62% under RCP4.5 and 7.65% under RCP8.5. Overall, increases in precipitation are amplified in streamflow, and the change in streamflow also shows significant temporal and spatial variations and large divergence between regional climate models. At the same time, the maximum streamflow in different durations are also projected to increase at three mainstream gauging stations based on flood frequency analysis. In particular, larger increases in maximum 1-day streamflow (+14.24% on average) compared to 5-day and 15-day water volumes (+12.79% and +10.24%) indicate that this projected extreme streamflow increase would be primarily due to intense short-period rainfall events. It is necessary to consider the impacts of climate change in future water resource management. [ABSTRACT FROM AUTHOR]

The spatiotemporal distribution of lakes in the Yangtze River basin (YRB) has changed tremendously; however, research on how and why lakes changed across this basin is limited. In this study, based on Google Earth Engine, Landsat images were used to track lakes (>1 km2) across the YRB from 2000 to 2019. Then, the anthropogenic and climatic impacts on the evolution of lakes were fully discussed. Results showed that the distribution of lakes across the YRB was extremely uneven. From 2000 to 2019, the total number and the area (referring to the surface area) of lakes increased by 30 and declined by 885 km2, respectively, but the trends of them were unobvious. In contrast, these changes and related causes exhibited high spatial heterogeneity. Lakes in the upper reaches significantly increased (P < 0.01). The expanded and new lakes were mainly distributed in the headwater catchment of the Yangtze River, which was closely related to increased precipitation. The number of lakes in the middle reaches decreased significantly (P < 0.05), which was primarily affected by intense human activities, such as land reclamation and agricultural irrigation. Precipitation played a dominant role in the fluctuation of the lake area here. In the lower reaches, the number of lakes increased (P < 0.01) as a result of the policy of "returning farmland to lakes," while the expansion of area (P < 0.05) was closely related to the precipitation and runoff. These findings have important policy implications for the conservation of lake resources. Plain Language Summary: Lakes are not only important water resources for human beings, but also play a vital role in ecosystems. However, with climate change and intensified human activities, the spatial distribution of lakes across the YRB has changed dramatically, and the causes have been unclear so far. In this work, based on satellite images and image processing, we tracked the lakes in the YRB during 2000–2019. And the climatic and anthropogenic causes of lake evolution (the total number and surface area) in different regions (the upper reaches, middle reaches, and lower reaches) were revealed. Results showed that the distribution of the lakes is uneven in the YRB, and most lakes are located in the middle and lower reaches. In the entire YRB, the total number and the area of lakes increased by 30 and declined by 885 km2, respectively, during 2000–2019. In the upper reaches, both the number and area of lakes increased significantly due to increased precipitation. In the middle reaches, the lake quantity reduced considerably as a result of intense human activities. Although most lakes in this region have shrunk, the total area was annually fluctuating due to changing precipitation. In the lower reaches, the increase in the number of lakes was mainly caused by human activities, while the expansion of the lakes was related to increased regional precipitation and runoff. This study would do a favor to the utilization and management of lake water resources. Key Points: Precipitation plays an important role in the expansion (upper and lower reaches) and shrinkage (middle reaches) of the lake surface areaHuman activities are of great significance in the fluctuation of the number of lakesThree shape indicators (aspect ratio, saturation, and narrowness) are defined to identify and remove rivers automatically and effectively [ABSTRACT FROM AUTHOR]

The use of remote sensing to monitor surface water bodies has gradually matured. Long-term serial water change analysis and floods monitoring are currently research hotspots of remote sensing hydrology. However, these studies are also faced with some problems, such as coarse temporal or spatial resolution of some remote sensing data. In general, flood monitoring requires high temporal resolution, and small-scale surface water extraction requires high spatial resolution. The machine learning method has been proven to be effective against long-term serial surface water extraction, such as random forests (RFs). MODIS data are well suited for large-scale surface water dynamic analysis and flood monitoring because of its short return cycle and medium spatial resolution. In this paper, the Yangtze River Basin (YRB) in China was selected as the study area, and two MODIS products (MOD09A1 and MOD13Q1) and RF method were used to extract the surface water from 2000 to 2016. Considering the disadvantages of temporal or spatial resolution of these two MODIS products, this study also presents a data fusion method to combine them and get higher spatiotemporal resolution water results. Finally, 762 surface water maps from 2000 to 2016 are obtained, whose temporal and spatial resolution is every eight days and 250 m, respectively. In addition, water extent variation is analyzed and compared to observed precipitation data. The main conclusions are as follows: (1) this constructed approach for long-term serial surface water extraction based on the RF classifier is feasible, and a good fusion method is used to obtain the surface water body with higher spatiotemporal resolution; (2) the maximum area of the surface water extent is 48.53 × 103 km2, and seasonal and permanent water areas are 20.51 × 103 km2 and 28.01 × 103 km2, respectively; (3) surface water area is increasing in the YRB, such that seasonal water area decreased by 3450 km2, and the permanent water area increased by 3565 km2 in 2001–2015; (4) precipitation is the main factor causing variation in the surface water bodies, and they both show an increasing trend in 2000–2016. As such, the approach is worth referring to other remote sensing applications, and these products are very both valuable for water resource management and flood monitoring in the study area. [ABSTRACT FROM AUTHOR]

• Improve the traditional emergy ecological footprint by integrating it with DEA-SBM. • Construct an ecological security assessment framework. • Develop the environmental technology investment efficiency index. • Fill the gap on quantitative research of ecological security for megacities. Environmental problems caused by intensive economic development and rapid urbanization have seriously constrained the sustainable development of social economy. Ecological security assessments have become an effective tool for measuring the unsustainability bottom line. Although Shanghai, Nanjing, Suzhou, Hangzhou, Wuhan, Hefei, Chongqing, and Chengdu are developed megacities in the Yangtze River basin of China, they are located in a fragile ecological environment. The megacities of the Yangtze River basin must achieve sustainable development based on an appropriate assessment of ecological security so that suitable suggestions can be proposed. To quantitatively measure and analyze the ecological security levels in these eight megacities in 2007–2016, this study applied the improved emergy ecological footprint model which optimizes the traditional emergy ecological carrying capacity by adding the new account of the socioeconomic emergy ecological carrying capacity. To improve accuracy, the environmental technology investment efficiency in the socioeconomic account was introduced using the slack based measure model of undesirable output. Then, this study constructed a framework of ecological security assessment. The results showed that from 2007 to 2016, the renewable resources carrying capacity varied greatly among these eight megacities which had an absolute effect on the contribution of emergy ecological carrying capacity. Environmental technology investment efficiency failed to increase. However, in the short term, it effectively increased the socioeconomic carrying capacity for megacities with poor renewable resources. The emergy ecological footprint followed a growth trend in Shanghai, Nanjing, Hangzhou, Hefei, and Chongqing, and a decreasing trend in Suzhou, Wuhan, and Chengdu. Across the study period, ecological deficits were identified in Shanghai, Suzhou, Nanjing, Wuhan, and Hefei. Hangzhou, Chengdu, and Chongqing had ecological surplus because of their superior renewable resources and their ecological security. Nanjing and Wuhan changed their status from sub-secure to secure. Except for Shanghai, the ecological footprint diversity indexes of all other megacities followed a growth trend, indicating that their consumption structure improved. Finally, this paper provides policy recommendations to help decision-makers formulate ecological security and sustainable development strategies. The results of this study provide a scientific reference for other megacities to mitigate ecological pressures by considering their local situations. [ABSTRACT FROM AUTHOR]

This paper explored the projected changes in precipitation, maximum temperature (T max), and minimum temperature (T min) over the Yangtze River Basin (YRB) based on 23 Global climate models (GCMs) from the Coupled Model Intercomparison Project phase 6 (CMIP6). The Empirical Quantile Mapping (EQM) approach was firstly applied to correct the biases in the GCMs. Next, the future changes were investigated by analyzing the multi-model ensemble (MME) of the bias-corrected dataset during 2025–2044 (near-term), 2045–2064 (mid-term), and 2081–2100 (long-term) periods, with reference to the baseline period 1995–2014, under three integrated scenarios (SSP1-2.6, SSP2-4.5, and SSP5-8.5) of the Shared Socioeconomic Pathways (SSPs) and the Representative Concentration Pathways (RCPs). Results show that: (1) the biases in CMIP6 GCMs can be effectively corrected by EQM, and the MME performs better than individual models for each climatic variable. (2) Precipitation over the YRB from 2025 to 2100 is projected to increase at the rate of 9.66 mm/decade, 13.45 mm/decade, and 21.01 mm/decade under SSP1‐2.6, SSP2‐4.5, and SSP5‐8.5, respectively. In the long-term, the annual precipitation is projected to increase by 10.41%, 10.66% and 15.80%, under SSP1‐2.6, SSP2‐4.5 and SSP5‐8.5, respectively. (3) T max (T min) over the YRB is projected to increase by 0.09 (0.07) °C/decade, 0.29 (0.27) °C/decade, and 0.66 (0.64) °C/decade under SSP1‐2.6, SSP2‐4.5, and SSP5‐8.5, respectively. In the long-term, T max (T min) averaged over the YRB is projected to increase by 1.75 (1.50) °C, 2.72 (2.54) °C and 5.04 (4.85) °C under SSP1‐2.6, SSP2‐4.5 and SSP5‐8.5, respectively. (4) Uncertainties in the projected precipitation and temperature over the YRB were reduced based on MME. But further researches, such as selecting the superior models with respect to the regional climate of the YRB from the CMIP6 and using the ensemble methods that assign weight based on the performance of each model, are still needed to provide more reliable climate projections. • Projected changes were explored by 23 CMIP6 GCMs under the three SSP-RCP scenarios. • Biases in the GCMs were corrected by Empirical Quantile Mapping (EQM) method. • Multi-model ensemble (MME) was used to reduce the uncertainties. [ABSTRACT FROM AUTHOR]

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Abstract: This paper examines the spatial variation of sediment yield in the Yangtze basin in China, a large basin with complex geology, climate, land-use history, and extensive sediment monitoring. 287 stations with drainage area less than 10,000km2 were used to study the scale effects of sediment yield. In order to develop scale relations for regional sediment yield, the whole study area was divided into eight sub-basins. Relation between specific sediment yield and drainage basin area was built for each sub-basin. Regional scaling relation was analyzed based on landforms, geology, lithology and land-use of each sub-basin. Three regional trends were identified in relation to the drainage area: (1) a declining trend, due to soil erosion on heavily cultivated steep land and the storage of sediment in floodplains; (2) a flat trend, due to mass movement on the upper reach and heavy agricultural disturbance on the middle and lower reaches; and (3) an increasing trend, due to downstream recruitment of sediment from land downstream where slope farming and deforestation occurred. Using these developed relations, areally adjusted sediment yield maps were created over the entire Yangtze basin. [Copyright &y& Elsevier]

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Coupled human and natural system research is an urgent issue in the Anthropocene. However, this has not yet been conducted from the perspective of multiplex networks, which are a powerful tool to elucidate the interactions in human-natural systems. This paper establishes a framework of human-water multiplex networks (HWMNs) to explain the combined effects of human-water interactions in the Yangtze River basin. The spatial linkages and the status of each province in the Yangtze River basin can be characterized through the index of network flow and topology. Research demonstrated that the highest import flow of the virtual water environment capacity flow in the Yangtze River Basin is to Jiangsu Province, at 16.2 thousand t. The highest export flow in the Yangtze River Basin is from Shanghai city, at 33.2 thousand t. The control power of Shanghai city over Sichuan Province accounts for 56.59% of the water resources, which is the highest value and can be recognized as one type of telecoupling of water resources. The provinces in the delta of the Yangtze River basin, including Shanghai city, Jiangsu Province and Zhejiang Province, benefit the most from economic trade. The community structure of the virtual water environment capacity flow is highly consistent with the geographical distribution of the Yangtze River basin. Comprehensive research methods combined with network flow analysis and network topology analysis provide more general results. The microenvironmental effect of indirect pollutant discharge is uncovered through HWMNs. This research can provide a more connected view of integrated water management. Image 1 • A framework of HWMN is established to reveal the combined environmental effects. • The key provinces are revealed through the network flow analysis and topology analysis. • The provinces in the Yangtze river delta obtains most of the water environment benefits. • The environmental effect of the indirect pollutant discharge through HWMN is revealed. [ABSTRACT FROM AUTHOR]

This paper developed a GIS-based spatial multi-index model for large basin-scale flood risk assessment. In terms of the risk definition proposed by the IPCC, the flood risk in the Yangtze River Basin (YRB) was classified into indexes of hazard, vulnerability, and exposure. The model systematically accounts for various flood risk indicators related to the economic, social and ecological environment of the YRB. Using the robust data space analysis and processing capabilities of ArcGIS, these flood risk indicators were superimposed and analyzed to generate an integrated flood risk spatial distribution map for the YRB. The modeling results were verified reasonably well using observation data from the YRB floods in 1998, 2008, and 2016. We found that 24.90% of the study area was at very high and high risk in 1998, and the risk in these areas decreased to 15.95% and 17.61% in 2008 and 2016, respectively. We believe that the GIS-based spatial multi-index model can be applied to other areas where basin-scale flood risk assessment is desired and contribute to further scientific research on flood forecasting and mitigation. • Develop a conceptual model for the large-scale flood risk assessment. • Integrating an index system method and a GIS-based approach. • Considering comprehensive economic, social and ecological impacts on the flood risks. • Model verification was conducted using observed floods in the Yangtze River Basin. [ABSTRACT FROM AUTHOR]

Analysis of ground‐based and remotely retrieved precipitation data reveals that heavy Meiyu precipitation events (HMPEs) produce a relatively independent rain belt over eastern China. A rotating calipers algorithm is applied to quantify the spatial scales of HMPEs. We find that HMPEs have regular spatial scales with an average length, width, and extent of about 1,400 km, 500 km, and 40.00 × 104 km2, respectively, through a comprehensive assessment of different types of HMPE, illustrating that HMPEs have a size similar to that of the subsynoptic‐scale Meiyu front (1,500–2,000 km). Convective activities along the Meiyu front zone and the upper westerly jet stream strongly affect the position and orientation of rain belts of HMPEs. The Meiyu front zone, strong vertical motions, and large transport of warm moisture have a comparable spatial scale to the HMPE rain belts over eastern China. Plain Language Summary: Many studies have revealed that extreme precipitation events of short or long duration have highly varying spatial scales from several hundred kilometers to several thousand kilometers, increasing the difficult of identifying the most flood‐related precipitation events and corresponding important atmospheric processes. We used a rotating calipers algorithm to quantify the length, width, position, and orientation of rain belts and found that flood‐related heavy Meiyu precipitation events with strong intensity, long duration, and large area have regular climatological spatial scales. Our results will benefit flood‐risk management and decision making for the Yangtze River Basin in China. Key Points: Flood‐related heavy Meiyu precipitation events have robust climatological spatial scales over eastern ChinaAn upper westerly jet stream and lower Meiyu front steer the position and orientation of rain belts of heavy Meiyu precipitation eventsConvective activities along the Meiyu front zone have a comparable spatial scale to the rain belt of heavy Meiyu precipitation events [ABSTRACT FROM AUTHOR]

Copyright of Advances in Atmospheric Sciences is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)