Dongting Research Articles

Trends and risk assessment of heavy metals in the surface sediments of river-connected lakes: A case study of Dongting Lake

This study analyzed the spatiotemporal distribution characteristics, ecological risks, biological toxicity, and sources of Cu, Zn, Pb, Cd, Hg, and As in the surface sediments of Dongting Lake, as well as the response of benthic macroinvertebrates to these pollutants. Among the three lake regions, the concentration of Cu, Zn, Pb, Cd, and As fell in the order of South Dongting Lake (SD) > East Dongting Lake (ED) > West Dongting Lake (WD), whereas the concentration of Hg fell in the order of WD > SD > ED. The concentrations of Cu, Zn, Pb, and As were 1.69–2.02 times the background values recorded in 1986, whereas the concentrations of Cd and Hg were 8.97 and 5.32 times the background values, respectively. The ecological risk was low for Cu, Zn, Pb, As but high for Hg and Cd. For Dongting Lake in aggregate, the heavy metals caused considerable ecological risk and high biotoxicity, although the situation was improving in recent years. Cd, As, Cu, Pb, Hg were mainly from agricultural sources, mining sources, tire wear and agricultural sources, industrial smelting and mining sources, industrial processing and smelting sources, respectively, and Zn was from mixed sources. A total of 66 species of benthic macroinvertebrates were identified from the sediments. From 2018 to 2022, the dominant benthic macroinvertebrates gradually shifted from the pollution-resistant in Tubificidae to those in Gammarus, Bellamya, Valvatidae, etc. Oligochaetes and Stictochironomus spp. exhibited extremely high response to heavy metals and could serve as indicator organisms of heavy metal pollution.

Different Adaption Strategies of Abundant and Rare Microbial Communities in Sediment and Water of East Dongting Lake.

The dynamics of aquatic microbes is of great importance for comprehending the acclimatisation and evolution of microorganisms in lake ecology. However, little is known about the adaption strategies of microbial communities in East Dongting Lake, which had special and complexity geographical characteristics. A semi-enclosed lake area (A) and a waterway connected to Yangtze River (B) both existed in the lake zone. Here, we investigated bacterial and fungal community diversity, community network and community assembly processes in sediment and water. The results indicated that the proportion of OTU numbers and their relative abundance for rare and abundant taxa were different obviously between sediment and water, but not between bacteria and fungi. However, abundant subcommunities dominated the shifts of bacterial community diversity and structure in A region, while rare subcommunities for fungal community diversity. Compared to fungal community, bacterial network was more compact and more key stones were identified as rare taxa. In addition, stochastic processes (dispersal limitation) drove the community assembly of abundant and rare subcommunities, but the effects of deterministic processes (including variable and heterogeneous selections) affected more on rare rather than abundant taxa. Partial Mantel test further indicated that the effect of environmental factors was a stronger force in shaping abundant bacterial subcommunities (TOC, NH4+-N, TN, and ORP) and rare fungal subcommunities (ORP). Environmental factors explained more of the variation in bacterial community structure than that in fungal community structure, although they had additional effects on fungal community diversity and community assembly. Moreover, bacterial community affected the fungal community as a biotic factor in water. This research provided new insights into better understanding of microbial communities in the complex environment of the East Dongting Lake.

Sustainable development of urban agglomerations around lakes in China: Achieving SDGs by regulating Ecosystem Service Supply and Demand through New-type Urbanization

The mechanism through which New-type Urbanization (NU), as a new direction in urban development, influences the Sustainable Development Goals (SDGs) by regulating the Ecosystem Services (ES) supply and demand remains to be determined. It is particularly true in urban agglomerations around lakes, characterized by severe human-land conflicts, where socio-economic development is closely linked to water. We selected China's urban agglomerations around lakes as the study area. We investigated the spatio-temporal heterogeneity of NU and the Ecosystem Service Supply and Demand Ratio (ESDR) from 2000 to 2018. We specifically focused on the dynamic trends of SDG 2 (Zero Hunger), SDG 13 (Climate Action), and SDG 15 (Life on Land). Furthermore, we utilized Structural Equation Modeling (SEM) to reveal the direct effects and indirect pathways through which NU influences the achievement of SDGs in the study area, emphasizing the differentiated performance of this mechanism across various urban agglomerations around Lakes. The results indicated that the ESDR has a particularly evident downward trend in urban centers along lakes, rivers, and road networks in spatial terms. The level of NU in urban agglomerations around lakes has increased by about 50% overall. It geographically exhibits three main spatial distribution patterns: “diffusion along the lake,” “homogeneous distribution,” and “diffusion along the river.” NU directly inhibits the achievement of SDGs but indirectly promotes the improvement of ESDR for food production and soil conservation, thereby indirectly facilitating the achievement of SDG 2 and SDG 15, but has an inhibitory effect on SDG 13. By regulating ESDR, NU is most effective in achieving SDGs in the urban agglomerations around Poyang Lake and Dongting Lake but has a significant inhibitory effect on the urban agglomeration around Hongze Lake. This research provides quantitative evidence for the urban planning shift, terrestrial ecosystem function restoration, and SDGs achievement in urban agglomerations around lakes. It also offers new insights from China for the sustainable urban construction of urban agglomerations around lakes worldwide.

Spatiotemporal change of lake shrinkage and its response to the unprecedented heat waves in the middle and lower Yangtze River Basin

ABSTRACT Due to the joint influence of human activities and climate change, lakes experience significant shrinkage or expansion, posing enormous challenges for water resource management and the ecological balance of lake ecosystems. As an important region abundant in water resources in China, the balance of water resources in the middle and lower Yangtze River Basin (MLY) is crucial for region sustainable development. However, to date, few studies have quantitatively analysed the lake area during heat waves in the MLY. To fill this gap, this study selected the summer of 2022, which encountered unprecedented heat waves, to analyse the changes of lake area in the MLY. Specifically, Sentinel-1 images were used as data sources, and the Random Forest (RF) model was applied to extract the monthly area of 62 lakes (area >10 km2) in the MLY from 2019 to 2022. The results showed that: (1) Compared to the Support Vector Machine (SVM) model and the Otsu method, the RF model had the highest accuracy, with its accuracy and Kappa coefficient in the testing samples of 97.14% and 0.94, respectively. During the period from June to September in 2022, the total area of 62 lakes decreased by 3475.50 km2. (2) Compared to the same period in the summer of 2019–2021, 23 lakes (37.10%) were observed to experience shrinkage. Among them, the area of Poyang Lake and Dongting Lake decreased to the level of the previous winter dry seasons in August 2022. (3) Temperature was the most important meteorological factor that caused changes in the lake area in the MLY, compared to precipitation, evaporation, and runoff. This research can help understand the impact of climate change on lakes and provide references for decision-making in the MLY to formulate the strategies of water resource management under the changing climate.

Spatiotemporal evolution and driving mechanism of Dongting Lake based on 2005–2020 multi-source remote sensing data

As one of the largest inland lakes in China, Dongting Lake has attracted widespread attention owing to its rich natural resources, unique geographical landscape, and important ecological functions. Recently, Dongting Lake has experienced phenomena such as an early dry season and backflow during the flood season. Multi-source remote sensing data and the normalised difference water index (NDWI) threshold method were used to systematically analyse the water area of the lake from 2005 to 2020. Additionally, it employed a centre of gravity migration model and a geographic detector model to investigate the lake's evolution patterns and driving mechanisms. The research identified notable fluctuations in Dongting Lake's water area during this period, with a particularly sharp decline in 2006—from 1509.74 km2 to 815 km2, marking a decrease of 694.74 km2 and a shrinkage rate of 46.01 %. Spatial analysis indicated that the centre of gravity of these water areas changed primarily between Nandashan Town, the Dongting Lake Management Committee, Wanzihu Township, and Qingtan Township, underscoring their significant influence on lake dynamics, including runoff, surface water availability, sediment deposition, and precipitation, all of which displayed strong positive correlations (Pearson coefficients of 0.57, 0.68, and 0.63, respectively), whereas population density showed a negative correlation (Pearson coefficient of −0.56). Furthermore, the study highlighted the substantial impact of the Digital Elevation Model (DEM) and its interaction with slope and aspect on Dongting Lake's evolution, with Q values of 0.537 and 0.543, respectively, emphasising their critical roles in shaping lake area changes and providing a crucial scientific basis for enhancing the understanding and effective management of water resources in the Dongting Lake Basin through comprehensive analysis of its spatiotemporal evolution and driving mechanisms.

Response to hydrometeorological changes and evaluation of habitat quality in the Dongting Lake basin, China

ABSTRACT With the advancement of hydraulic engineering processes, surface water resources are encountering unprecedented crises that threaten social and ecological sustainability. This study analyzed the response changes and potential correlations between river conditions and climate change in the Dongting Lake (DTL) basin using gray correlation analysis and the LSTM model. Additionally, the InVEST model was employed to further assess the distribution of habitat quality within the basin. The results of the study showed that (1) the range of variation of environmental flows in each tributary became significantly narrower and the frequency of extreme hydrological conditions was reduced in the period after the abrupt hydrological change. (2) The hydrological status had a higher degree of correlation with the rainfall index, and the performance is more prominent on the Xiang River, and the influence of temperature is less. (3) Except in the Xiang River Basin, human activities are the dominant factor of runoff variation, and the annual contribution is generally higher than 50%. (4) Habitat quality in the ‘high’ distribution was the most guarded and always accounted for more than 60% of the basin, while habitat quality in the east-central part of the DTL basin and around the DTL was generally low.

Spatial Distribution, Influencing Factors and Sustainable Development of Fishery Cultural Resources in the Yangtze River Basin

Agricultural cultural heritage is crucial in advancing comprehensive rural revitalization. The Yangtze River Basin is rich in biodiversity and abundant in fishery cultural resources. The cultural resources not only reflect the ecological wisdom of harmonious coexistence and the human–land relationship between humans and nature but also provide critical cultural support for rural revitalization and watershed sustainable development. This study investigates the spatial distribution, influencing factors, and historical evolution of fishery cultural resources in the Yangtze River Basin. The highest proportions of significant resources are found in fishery engineering and landscapes, culinary flavors, fishery customs, dances, fishery gear, and poetry. By analyzing 14 categories of fishery cultural resources and 157 national and provincial intangible cultural heritage items, this study reveals a significant geographical clustering of these resources in the mid-lower reaches, particularly around the middle reaches of the Yangtze River and Poyang Lake Basin, Wuhan and Dongting Lake, and the lower reaches of the Taihu Lake Basin. This study underscores the role of natural geographical conditions, aquatic biodiversity, socio-economic factors, and historical–cultural backgrounds in the distribution and evolution of fishery cultural resources, with these factors interacting dynamically. By advocating for a comprehensive approach to coordinating fishery culture preservation with rural revitalization, this study outlines a multidimensional strategy for the preservation and sustainable development of fishery cultural resources.

A long-term (1984–2021) wetland classification dataset for the Yangtze River Basin from continuous Landsat image collections

The wetlands along the Yangtze River Basin (YRB) have provided a variety of ecological and economic benefits. However, the lack of a long-term wetland classification dataset with comprehensive wetland categories has created in a barrier to evaluating the long-term variations of YRB wetlands for their habitat health, carbon storage, greenhouse gas emissions, and ecosystem service capacity. Therefore, this study aimed to generate a wetland classification dataset for the YRB covering the time period from 1984 to 2021. The dataset named Long-Term Wetland Classification Dataset for YRB (LTWCD_YRB) was created using a Random Forest machine learning classifier on Google Earth Engine with 30 m resolution Landsat 5, 7, 8 muti-spectral images. The maps of LTWCD_YRB demonstrated the spatial distribution, annual variability, and seasonal cycle of nine wetland categories in the extent, and the total validation accuracy can reach 85 %. The LTWCD_YRB indicates that the total wetland area of the YRB in 2021 was larger than that in 1984, with a constant increase in human-made wetlands and fluctuating natural wetlands. Aquaculture ponds expanded the most by 4,987 km2, while inland marshes in the source region exhibited the most fluctuations. Seasonal changes in wetlands were prominent in the Poyang Lake Basin, Dongting Lake Basin, and YRB source region. Human activities were found to be more dominant than natural driving forces in affecting wetlands. The LTWCD_YRB offers a consistent agreement of wetland area variations with the other satellite-based wetland datasets in the YRB, making it valuable for researchers, policymakers, and stakeholders to better understand the YRB wetlands and to support sustainable wetland management practices.

Different effects of natural siltation, damming and pollution on two adjacent lakes of Dongting Lake Wetland: Evidence from paleolimnology

Evaluating the influences of hydrology on lotic floodplain lakes has been difficult due to concurrent effects of different human activities in the catchment. This study aims to explore the responses of floodplain lakes to natural siltation and damming by studying grain size and geochemical elements in 210Pb-dated sediment cores from two adjacent lakes with different hydrological conditions in the same catchment, including a hydrologically-isolated lake (Donghu Lake) and a hydrologically-connected lake (East Dongting Lake) in the middle Yangtze floodplain. The results showed that the riverine sediment supply declined in Donghu Lake after its isolation from the Yangtze River due to natural siltation in the 1910s. In East Dongting Lake, the riverine sediment supply remained relatively stable before the operation of the Three Gorges Dam (TGD) in 2003 CE, and then declined rapidly in response to a decrease in riverine sediment supply. Total phosphorus and total organic carbon in Donghu Lake increased after the “reform and opening-up” in the late 1970s, whereas they remained at low concentrations in East Dongting Lake before the TGD operation in 2003 CE. Hydrological isolation from the Yangtze River reduced the influxes of riverine sediments, but promoted nutrient enrichment and primary production in East Dongting Lake through extending water residence times. Stable element composition in Donghu Lake after 2003 CE suggested that the TGD operation had minor effects on hydrologically-isolated lakes. The comparison between hydrologically-closed and hydrologically-free lakes within the same catchment provides an effective method to identify different effects of natural siltation, damming and environmental pollution.

A Study on the Spatial Structures and Mechanisms of Intangible Cultural Heritage and Traditional Villages in the Dongting Lake Basin

This study focuses on 1209 national and provincial intangible cultural heritage items and 1234 traditional Chinese villages within the Dongting Lake Basin. Using kernel density analysis, centroid models, coupling models, and quantitative spatial–structural models, the present research analyzes the spatial–structural characteristics and formation mechanisms of intangible cultural heritage and traditional villages to provide scientific support for their preservation, inheritance, and effective utilization. The results revealed the following: (1) Intangible cultural heritage and traditional villages in the Dongting Lake Basin exhibit a very concentrated spatial distribution, with similar spatial–structural characteristics. (2) High spatial coupling of intangible cultural heritage and traditional villages is observable in the sub-basins of Dongting Lake, such as the Yuanjiang, Zishui, and Lishui basins, whereas the Xiangjiang Basin and Dongting Lake area present relatively lower levels of spatial coupling. In terms of the categories of intangible cultural heritage, four of them—cultural heritage, folk literature, traditional music, traditional dance, and traditional drama—have the smallest deviation distance and index values from traditional villages. The coupling degree was higher than 0.70, and there were some differences in the coupling degree between the other six categories of intangible cultural heritage and traditional villages. (3) The spatial–structural characteristics of intangible cultural heritage and traditional villages in the Dongting Lake Basin emerged from the combined effects of multiple factors, including internal connections between the two, as well as external factors such as the natural environment, socio-economic conditions, and cultural policies, all of which play crucial roles in the formation processes of these characteristics.

Land use and river-lake connectivity: Biodiversity determinants of lake ecosystems

Lake ecosystems confront escalating challenges to their stability and resilience, most intuitively leading to biodiversity loss, necessitating effective preservation strategies to safeguard aquatic environments. However, the complexity of ecological processes governing lake biodiversity under multi-stressor interactions remains an ongoing concern, primarily due to insufficient long-term bioindicator data, particularly concerning macroinvertebrate biodiversity. Here we utilize a unique, continuous, and in situ biomonitoring dataset spanning from 2011 to 2019 to investigate the spatio-temporal variation of macroinvertebrate communities. We assess the impact of four crucial environmental parameters on Lake Dongting and Lake Taihu, i.e., water quality, hydrology, climate change, and land use. These two systems are representative of lakes with Yangtze-connected and disconnected subtropical floodplains in China. We find an alarming trend of declining taxonomic and functional diversities among macroinvertebrate communities despite improvements in water quality. Primary contributing factors to this decline include persistent anthropogenic pressures, particularly alterations in human land use around the lakes, including intensified nutrient loads and reduced habitat heterogeneity. Notably, river-lake connectivity is pivotal in shaping differential responses to multiple stressors. Our results highlight a strong correlation between biodiversity alterations and land use within a 2–5 km radius and 0.05–2.5 km from the shorelines of Lakes Dongting and Taihu, respectively. These findings highlight the importance of implementing land buffer zones with specific spatial scales to enhance taxonomic and functional diversity, securing essential ecosystem services and enhancing the resilience of crucial lake ecosystems.

Reconstruction of Historical Metal Backgrounds in Lacustrine Environments of China Using an Anodonta woodiana "Specimen Bank".

Anodonta woodiana samples from Xidong Water Works and Mashan in Taihu Lake, Yiyang near Dongting Lake, and Taiping Harbor in Gehu Lake preserved in a "specimen bank" established for the "Freshwater Mussel Watch" monitoring program were used to determine the historical metal backgrounds from different waters in the present study. The elements Co, Ni, Mo, Cd, Al, Cr, Mn, Fe, Cu, Zn, As, Ba, and Pb were determined using A. woodiana from four lacustrine sites. The results showed that Al, Cr, Mn, Fe, Cu, Zn, As, Ba, and Pb were all detected, whereas Co, Ni, Mo, and Cd were below the detection limits of 0.0165, 0.0106, 0.0189 and 0.0182µg kg- 1, respectively. In particular, A. woodiana was noted to be an unusual Mn hyperaccumulator (ranged from 5124.09 to 13015.47µg g- 1). The results of discriminant analysis showed that the four water samples could be accurately separated. This difference has the potential to infer the background difference of heavy metal pollution in different lacustrine habitats.

The relationship between landscape pattern and plant species diversity in east Dongting lake wetland based on different Eco-environment

Exploring the impact factors associated with biodiversity and the relationship between them has always been a concerned issue in recent years. However, the previous research mostly focus on theoretical layer. Accordingly, the relationship between landscape pattern and biodiversity is to be analyzed in this research. The landscape pattern determines the function and ecological process of the landscape, and affects the species flow, information flow and energy flow in the landscape. Land use patterns has inevitably left an impact on the landscape pattern. Landscape pattern determines the function and ecological process of landscape and thus plays a significant role in biodiversity. East Dongting Lake National Nature Reserve is taken as the research object of the paper, and the remote sensing image data of three different time periods are collected, including 2000, 2010 and 2020. With an interpretation of the vegetation landscape pattern changes inside the protected area to collect and analyze the vegetation coverage. By comparing landscape patterns and the dynamic changes of land use in different periods of time, the correlation between landscape pattern characteristics and regional biodiversity is to be analyzed. Research shows: (1) From 2000 to 2020, the vegetation coverage of East Dongting Lake increased, but the landscape shape, scale, diversity and uniformity index decreased to varying degrees. (2) At the class level of landscape type, the relationship between landscape index and biodiversity is different. A complex relationship between farmland landscape and biodiversity. There is a significant positive correlation between the index of grassland landscape type and the index of regional biodiversity. (3) The correlation analysis results at the landscape level show that the landscape characteristic index is positively correlated with the regional biodiversity index. The grassland landscape in the area is the main habitat of biological species. At the same time, as the main grain producing area, the impact of farmland landscape cannot be ignored. This study has certain theoretical guiding significance for the protection and management of biodiversity in the region in terms of maintaining landscape pattern in particular the grassland landscape area and increasing vegetation coverage in the process of land use.

The lake and groundwater interaction based on water balance in Dongting Lake, China

Study region: Dongting Lake (DTL), the second largest freshwater lake in China, plays a crucial role in regulating and storing water within the Yangtze River Basin.Study focus: The study utilized the water balance method to extensively investigate the exchange volume of groundwater and DTL from 2003 to 2020. Furthermore, we analyzed the impact of climate change and human activities on the interaction between groundwater and DTL.New hydrological insights for the region: Unlike previous studies, our study further included the ungauged runoff, providing a more comprehensive assessment of the water balance of DTL. From May to July, groundwater recharge from DTL, with an average monthly recharge of 0.71 km³. Conversely, groundwater discharges into DTL from August to April of the following year, with an average monthly discharge of 1.12 km³. The net groundwater discharge into the lake from 2003 to 2020 amounts to 7.98 km³/yr. Intriguingly, precipitation over the lake contributes a mere 0.6% to the total inflow, while lake evapotranspiration constitutes only 0.4% of the total outflow. Inflow runoff and outflow runoff play a leading role in the water balance of DTL, significantly influencing the exchange capacity between the lake and groundwater. Groundwater discharge into the lake serves as compensation for diminished runoff stemming from extreme climate occurrences, like droughts, and anthropogenic actions such as dam construction.

Characterizing future changes in compound flood risk by capturing the dependence between rainfall and river flow: An application to the Yangtze River Basin, China

Compound floods induced by co-occurring multiple drivers may exacerbate the flood impacts and lead to larger flood damage. Exploring future changes in compound flood risk is imperative for flood management and disaster reduction. This study attempts to investigate future changes in compound flood risk across the Yangtze River Basin during 2030 ∼ 2100. Future river flow was projected using an improved hydrological model and pairwise series of extremes of rainfall and river flow were extracted from both observed and projected series. Subsequently, stochastic pairs of rainfall and river flow characterizing compound floods were proportionally sampled from their bivariate joint distributions. The damage from each compound flood was obtained from the flood damage function constructed by Random Forests (RF). Further, the expected annual damage (EAD) was calculated to investigate future changes in compound flood risk. Results show that: (1) Future annual maximums of rainfall and river flow are expected to increase by 14.51 % ∼ 66.13 % and 1.72 % ∼ 55.73 % in the mainstream and northern tributaries, while future annual peak discharge in the southern tributaries (except for the Dongting Lake Basin) is expected to decrease by 4.18 % ∼ 12.30 %. A similar spatial distribution of future changes is also found in the bivariate joint distribution of rainfall and river flow. (2) The high coefficient of determination (R2) of 0.84 indicates the satisfactory simulation and projection capacity of the constructed flood damage function. The positive stepped relationship between flood damage and rainfall or river flow reflects the superposition of multiple flood damage processes. (3) The Han River Basin, the Jialing River Basin, and the two-lakes (the Dongting and Poyang Lakes) area face great threat from compound floods in both historical and future periods. Future compound flood risk is expected to increase by 13.43 % ∼ 46.04 % in these regions except for the Poyang Lake Basin, while future risk is expected to increase by 2.03 % ∼ 46.04 % in the whole basin. The findings help improve the understanding of future flood risk variations in the Yangtze River Basin and provide essential information for damage reduction.

2011–2015年东洞庭湖洲滩典型植物群落样方调查数据集

The fixed sample plot investigation obtains the dynamic characteristics of ecosystem through long-term data accumulation and accurate space-time comparison, which provides a solid basis for long-term ecosystem research. In accordance with the unified monitoring specifications set forth by the Chinese Ecosystem Research Network (CERN), Dongting Lake Wetland Ecosystem Research Station conducts long-term positioning monitoring on the species composition and community characteristics of typical beach vegetation in the wetland ecosystem in response to the changing hydrological conditions of Dongting Lake. We processed the data of long-term monitoring sample plots of three typical wetland plant communities (Carex sp, Miscanthus lutarioriparius and Polygonum hydropiper) in Dongting Lake to obtain the dataset of sample survey of typical plant communities on East Dongting Lake beach from 2011 to 2015. This dataset covers a total of 14 indicators, including species name, Latin name, number of plants (clusters) (plants or clusters/quadrats), average height of leaf layer (cm), average height of reproductive branches (cm), coverage (%), phenological period, dominant species, number of plant species, density (plants or clusters/m2), leaf layer height (cm) of dominant species, reproductive branch height (cm) of dominant species, total coverage (%), and total dry weight of aboveground green parts (g/m2). This dataset comes with detailed background information to ensure its consistency across both spatial and temporal dimensions. Moreover, to ensure data accuracy and reliability, the dataset underwent comprehensive quality control throughout the entire process and is subject to expert review and verification. It can serve as an important source of background data for studying the process and succession trends of the beach wetland ecosystem in response to the hydrological conditions of Dongting Lake, and provide data support for vegetation remote sensing monitoring, biodiversity protection, wetland ecological restoration and adaptive management of Dongting Lake.

Distribution Characteristics, Ecological Risk Assessment, and Source Tracing of Heavy Metals in the Sediments of Typical Lakes in the Middle Reaches of the Yangtze River

In this study, surface sediment samples were collected from Dongting Lake, Honghu Lake, and Chihu Lake, and the concentrations of 10 heavy metals were measured. Then, the potential risk of heavy metal accumulation was evaluated using the cumulative pollution index (Igeo), the enrichment factor (EF), and the potential ecological risk index (RI), and the sources were traced using correlation analysis (Pearson) and principal component analysis (PCA). The results showed that the pollution and potential ecological risk of Cd were the most serious. The mean values of Cd in East Dongting Lake, Honghu Lake, and Chihu Lake were 2.85, 1.59, and 3.57 mg·kg-1, respectively. The concentrations of Cd were 25.87, 11.36, and 37.58 times higher than the soil background values of the corresponding provinces, which exceeded the risk screening value (0.6 mg·kg-1). Particularly, the Cd concentration of Chihu Lake exceeded the risk control value (3.0 mg·kg-1). Besides Cd, the concentration of As in Honghu Lake was also of concern. At the same time, the Cu, As, Zn, and Pb in Chihu Lake should not be neglected. The potential ecological risks of the three lakes were ranked as follows:Chihu Lake (RI=1 127)>East Dongting Lake (RI=831)>Honghu Lake (RI=421). The primary sources of heavy metals were industrial mining, agricultural production, and aquaculture, and some heavy metals (Mn and Cu) were from natural sources. This study was of great significance for the prevention and control of heavy metals in the sediments of typical lakes in the middle reaches of the Yangtze River.

PDFID: A high-resolution flood inundation dataset with a long time series

Study regionPoyang Lake and East Dongting Lake, China. Study focusOn the basis of data on the extent of the inundation of water bodies, the water level, and DEM data, this study constructed an hourly flood inundation dataset (PDFID) for the East Dongting Lake and Poyang Lake regions with a 10 m resolution and a coverage area of >5000 km2 from 2012 to 2022 by using the RFim model and the U-net model. Validation of the results on Sentinel-1 SAR images and Sentinel-2 MSI optical images showed that the overall accuracy of the dataset ranged from 88% to 97%, with a kappa coefficient ranging from 0.601 to 0.932. The accuracy for the East Dongting Lake region ranged from 88% to 97%, with a kappa coefficient of >0.67, and for the Poyang Lake region, the accuracy ranged from 89% to 97%, with a kappa coefficient of >0.6. New hydrological insights for the regionFlood inundation datasets with a high spatiotemporal resolution and long time series enable us to analyze and comprehend floods’ processes, patterns, and dynamics, facilitating the enhanced development and management of flood prevention and mitigation strategies. However, they have yet to be made available. Thus, this study can provide a fundamental data source for analytical mining and predicting the flooding processes in basins.

Forecasting environmental water availability of lakes using temporal fusion transformer: case studies of China's two largest freshwater lakes.

Preserving lacustrine ecosystems is vital for sustainable watershed development, and forecasting the environmental water availability of lakes would support policymakers in developing sound management strategies. This study proposed a methodology that merges the lake water level prediction and environmental water availability evaluation. The temporal fusion transformer (TFT) model forecasted the lake water levels for the next 7 days by inputting the streamflow and lake water level data for the past 30 days. The environmental water availability was assessed by comparing the forecasted lake water levels with the environmental water requirements, resulting in adequate, regular, scarce, and severely scarce environmental water availability. The methodology was tested in two case studies: Poyang Lake and Dongting Lake, the two largest freshwater lakes in the Yangtze River Basin, China. The TFT model performed well in forecasting the lake water levels, as shown by the high coefficient of determination and finite root mean square error. The coefficients of determination exceeded 0.98 during the model training, validation, and test for both Poyang Lake and Dongting Lake, and the root mean square errors ranged from 0.06 to 0.46 m. The accurate prediction of lake water level promoted the precise forecasting of the environmental water availability with the high Kappa coefficient exceeding 0.90. Results indicated the rationality and effectiveness of integrating the lake water level prediction and environmental water availability evaluation. Future research includes the applicability of the TFT model to other lakes worldwide to test the proposed approach and investigate strategies to cope with environmental water scarcity.

The Spatial and Temporal Variability of the Blue–Green Spatial Structures of the South Dongting Lake Wetland Areas Amidst Climate Change, including Its Relationship with Meteorological Factors

In recent years, the water level of the Dongting Lake (DTL) has been continuously low, and the wetland area and landscape pattern have changed significantly. Considering the obvious spatial heterogeneity of water regime changes in different waters of the DTL, this paper takes two core areas of the South Dongting Lake Nature Reserve (SDLNR) as study areas and analyzes the spatial distribution characteristics of the wetland blue–green landscape patterns by using remote sensing image data and hydrological and meteorological data. The multi-scale correlation between runoff, precipitation, temperature, and evapotranspiration in the SDLNR was studied via cross-wavelet transform analysis. The results show the following: (1) The change in the blue–green spatial patterns in different regions in different periods is inconsistent, and this inconsistency is related to the topography, climate, and human activities in each region; (2) there are seasonal fluctuations in precipitation, air temperature, and evapotranspiration in the SDLNR. Among them, the annual mean temperature shows a rising trend and passes the significance test with 95% confidence, while the annual mean precipitation and annual mean evapotranspiration show no significant change trend; and (3) our Pearson correlation analysis and cross-wavelet change results show that precipitation and temperature are strongly correlated with runoff, with a resonance period of 8–16 months, while the correlation between evapotranspiration and runoff is not significant. We recommend that policymakers establish an effective early warning system and make plans to store water through micro-terrain transformation in possible climate change treatments and strategies.