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The management and protection of the world's major river basins have received increasing attention, and a series of related measures, including fishing bans and ecological engineering restoration, has been pioneered in the Yangtze River Basin (YRB). This paper provides a quantitative and qualitative analysis of research trends and hotspots in the water environment of the YRB through bibliometric means. The database period was from its inception to December 31, 2020. This review combines the changing trends in the water environment of the YRB in the form of keywords. The results show that the governance of the YRB is based on the relationship between "water" and "sediment" as an entry point, focusing on changes in the "temporal" and "spatial" allocation of water resources; further, when considering the problem of "eutrophication" caused by the release of "nitrogen" and "phosphorus" from "sediments," water quality factors such as "heavy metal pollution" and "organic pollution" are becoming more prominent; then water quality factor affects "biodiversity," aquatic ecology becomes more and more concerned, and "ecological risk" factor is taken into consideration. Therefore, future management of the YRB requires consideration of all elements of the basin, including water resources, water quality, and aquatic ecology, and how to coordinate these all material elements is the obstacle and breakthrough point. In addition, further studies on research frontiers have revealed that ecological risk, emerging bioinformatics technologies, and, source apportionment will become the new and popular directions and trends in research. This review is intended to provide insights into the management of other large river basins around the world. [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]

The Yangtze River Basin has periodically been subject to torrential rains and floods. It is of great significance to characterize the extreme precipitation patterns to learn about frequent flood characteristics in the Yangtze River Basin. Commonly, spatiotemporal characteristics of extreme precipitation was studied by regional frequency analysis method with site data. Spatial sparse site data may cause imprecise divisions of homogeneous regions. In this paper, the spatiotemporal characteristics of extreme precipitation was studied by regional frequency analysis with corrected satellite‐based grid precipitation data (Global Land Data Assimilation System, GLDAS) rather than site data. The results show that: (1) The corrected GLDAS daily precipitation data had greatly improved its ability to capture extreme precipitation events in Yangtze River Basin, as the data average accuracy increased from 0.215 before correction to 0.849 after correction. It is feasible to use satellite‐based grid precipitation data to replace the site data for the regional frequency analysis of extreme precipitation. (2) The Yangtze River Basin was categorized into seven homogeneous regions for the annual maximum 1‐day (RX1DAY) index with an automatic subjective adjustment method. (3) The regional growth curves and quantiles of the Yangtze River Basin were drawn for the return period for 2–100 years. (4) Spatial patterns of extreme daily precipitation series with a return period of 100 years indicated that the precipitation amount increases gradually from the upper to the lower Yangtze River Basin, from the "arid zone" to the "wet zone" and then to the "special wet zone", and the 100‐year return level of RX1DAY varied from 30.3 to 301.8 mm. There were three main precipitation centres, the Sichuan Basin, Dongting Lake Basin, and a great triangle area covering the Poyang Lake Basin and the south foot of Dabie Mountain. [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]

Revegetation programmes aim to avoid land degradation, control soil erosion, reduce floods, and improve ecological conditions. China has planted billions of trees over the past 20 years. However, little is known about the effectiveness of this artificial revegetation and its consequences on China's national conservation policies and changes in biophysical factors at the county level. Here we use satellite time series data and develop a new metric, the revegetation index (RVI), that quickly monitors revegetation and its long‐term changes. We found that the number of regions where the Grain to Green Program (GTGP) was successfully implemented was only about 55.8% of the areas of GTGP implementation. Surprisingly, we provide observational evidence that the implementation of the GTGP can decrease soil erosion and drought, and increase water availability, but revegetation in the Yangtze River basin (YRB) in China has a limited impact on soil erosion, water, and drought. In particular, for revegetation between 1999 and 2016, indicating that a previous assessment by the Government revealed as official statistics may have overestimated the effects of the ecological restoration practices. [ABSTRACT FROM AUTHOR]

Many studies found that land use change (LUC) had great impacts on regional precipitation, due to thermodynamic and dynamic responses. However, the relative contributions of these two factors to changes in precipitation due to LUC are rarely investigated. This study quantifies the relative contributions of thermodynamic and dynamic to the changes of mean and extreme precipitation due to LUC based on simulations of the Weather Research and Forecasting (WRF) model. The Yangtze River Basin (YRB) is used as a case study, as it has experienced great LUC during the past decades. Four land use scenarios (two factual cases and two hypothetical reforestation scenarios) were used to test the sensitivity of precipitation changes to LUC. Changes in mean and extreme precipitation over the YRB for all seasons are attributed to thermodynamic and dynamic changes using 500‐hPa geopotential height and precipitation data derived from the simulations of WRF. The results show that the factual process of LUC results in a decrease in summer mean daily precipitation and precipitation extremes in most areas of the YRB (except for the middle reaches of the YRB), while the hypothetical reforestation contributes to an increase in summer mean and extreme precipitation, and the impacts of reforestation on increasing precipitation are limited. The thermodynamic change contributes to an increase in seasonal mean daily precipitation, extreme precipitation totals and occurrence frequency of precipitation extremes with contributions ranging from 94 to 102%, which is the main contributor of changes in precipitation due to LUC. The dynamic change only makes a small contribution to the change of precipitation. Because the contributions of thermodynamic can be offset by dynamic changes to changes in precipitation, it could result in minimal changes in precipitation and occurrences of precipitation extremes. [ABSTRACT FROM AUTHOR]

As one of the most influential oceanic and atmospheric oscillations in the Earth system, El Niño‐Southern Oscillation (ENSO) has modulated numerous geophysical processes. This is particularly true for the Yangtze River Basin (YRB), which is vulnerable to Asian Monsoon and faces serious hydrological hazards. In this study, the co‐variability between lag–lead precipitation and sea surface temperature anomalies was evaluated utilizing singular value decomposition (SVD) method. Moreover, certain teleconnections between ENSO and streamflow were identified by wavelet methods. In addition, the contribution of related atmospheric variables was revealed by composite analysis. Results indicate that there are strong associations in lag–lead seasons between the wet condition (dry condition) and September–November (December–February) mature ENSO phase. Significant common power and coherence signals between the ENSO indices and the streamflow occur in the 4–8, 8–16 and 16–32 seasonal scales. Meanwhile, the activity cycle of the ENSO indices ahead of streamflow increases from the mid‐lower reaches to the source region. In addition, the Western Pacific Subtropical High is strengthened during the mature ENSO phase. Anomalous sinking motions and divergent water vapour flux occupy the YRB, reducing the precipitation and leading to the dry condition in the source region until the following March–May. On the other hand, ascending movements and abundant water vapour flux coming from northern Pacific, equatorial western Pacific and the Bay of Bengal result in the wet condition in the mid‐lower reaches. [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]

The culture‐based fishery of Liangzi Lake, Yangtze River Basin, established in 1992, yielded 2,652 t/year (±167) between 2005 and 2015, dominated by stocked carps [Hypophthalmichthys molitrix (Val.) and Hypophthalmichthys nobilis (Richardson)] and mitten crab Eriocheir sinensis (Milne Edwards), accounting for 53% and 23% of the production and 20% and 52% in value, respectively. The lake had a macrophyte cover dominated by Vallisneria natans (Lour.) Hara with a cumulative biomass of 10,647 g/m2 that disappeared after a major flood in 2010 and changed its ecology. Management changes in stocking strategies introduced in the post‐flood period enabled the culture‐based fishery to maintain viability and sustainability to combat the major ecological change in the lake. The stocked species contributed significantly to nutrient removal of 24.71 ± 5.12 t/yr and 6.29 ± 0.87 t/yr of total nitrogen and total phosphorus, respectively. [ABSTRACT FROM AUTHOR]